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CHICAGOCENTRAL CHILLEDWATER SYSTEMS
(SEE) MODEL ANALYSIS
Waterside Economizers
Kirby Nelson PE5/5/2023
Kirby Nelson PE Page 1
Contents:Executive Summary (a) ASHRAE JOURNAL Articles of June 2014 & August 2014 (b) System Energy Equilibrium (SEE) Modeling (c) BASE BUILDING-Large office of (PNNL) studyCHAPTER 1: Peak Day Performance & Performance at 50F DB & 45F WBCHAPTER 2: Increase supply air temperature from 55F to 60F NOMENCLATURE:
EXECUTIVE SUMMARY(a) ASHRAE JOURNAL Articles of June 2014 & August 2014In the June 2014 ASHRAE Journal Taylor presents an article titled, How to Design & Control Waterside Economizers, and in the August 2014 issue Nall presents a more detail discussion titled, Waterside Economizers & 90.1. Both articles advocate waterside economizers but neither provides justification; analysis of the concept with detail energy models is, I suggest, required before inclusion into 90.1-2013. To my knowledge none of the models advocated by ASHRAE or Pacific Northwest National Laboratory (PNNL) can adequately address this problem. I have put the problem to a System Energy Equilibrium (SEE) model that is consistent with the laws of thermodynamics. The model is of a Chicago half million square foot 13 story large office as defined by (PNNL) in its study of 90.1-2010, (see link below). Chapter 1 shows that a water economizer can have little effect on the kW demand of the system. Chapter 1 does not deal with increasing air supply temperature, increasing water supply temperature, and the effect of solar. These issues and others will be addressed in upcoming chapters. Chapter 2 deals with increasing supply air temperature from 55F to 60F. The result is not good; the system kW demand increases. Kirby Nelson P.E.Life Member ASHRAE
Kirby Nelson PE Page 2
(b) System Energy Equilibrium (SEE) ModelingFollowing is a brief summary of the characteristics of system energy equilibrium (SEE) models and the (SEE) model experience of the author.(SEE) ModelSystem energy equilibrium (SEE) models and schematics can be developed for any condition of weather and operational conditions that may occur in a real system. The requirement for the (SEE) model/schematic is always the same; it must duplicate the performance of the equipment that make up the system and it must obey the laws of thermodynamics and physics and include the nonlinear characteristics of the components of the system. The (SEE) model/schematics defined here assume all chillers are of the same size and model and the air handlers are the same size and model and equally loaded.Math models that duplicate the real time performance of systems are standard practice in the space program and in the development of military products such as missiles, cannons, and other complex systems. The System Energy Equilibrium (SEE) Model presented here duplicates the thermodynamic and nonlinear performance of real systems and therefore can define the best possible performance of a system consistent with the design and control concepts incorporated in the design i.e. the theoretical performance of the system.The author has found that the design and control concepts advocated by ASHRAE and Pacific Northwest National Laboratory (PNNL) yields a design that requires more demand kW and therefore energy than does a more conventional design and control strategy. These differences in design and control are detailed in other papers on this site.
Kirby Nelson experienceSystem Energy Equilibrium (SEE) modeling is not a new concept. The author was involved in this approach to modeling in the 1970’s designing military products and then as corporate energy manager for Texas Instruments Inc. modeling building systems.The concept is to simply write the basic physics and thermodynamic equations of the system and simultaneously solve the set of equations with a computer. The results will duplicate the performance of the real system if the equations are correct; nonlinear characteristics input and equipment efficiencies input. The equations can be, and should be, corrected by iterating between the real performance data verses the model and updating the model equations.
The first HVAC paper published by Kirby using this approach was in the ASHRAE Journal of December 2006. "7 Upgrades to Reduce Building Electrical Demand"In March 2010 he had an article in Engineered Systems "Central Chilled Water System Modeling" & July 2010 an HPAC article on chiller selection "Central-Chiller Plant Modeling"In 2011 a 5 article series in HPAC dealing with Primary/Secondary vs. Primary-Only Pumping. The second article dealt with the efficient control of a P/S plant and the third article with efficient control of a P-only plant. The fourth article was "Anatomy of Load delta-T" and the fifth added the building and air side equipment to the analysis.In 2012 Kirby presented two advance technical papers at ASHRAE Chicago 2012. (CH-12-002) title “Simulation Modeling of a Central Chiller Plant” and (CH-12-003) "Simulation Modeling of Central Chilled Water Systems".Since Chicago he has continued to develop the concept of (SEE) modeling and has entered into discussions on ASHRAExCHANGE on the ASHRAE web site. Kirby’s analysis of these issues and others to follow can be viewed at http://kirbynelsonpe.com/
Kirby Nelson PE Page 3
Personal note:I first became involved in this approach to system analysis/design in the late 1960's and early 1970's in the design of military products, Shrike Missile, Lacer Guided Bombs, Anti-Tank Projectiles, a helicopter mounted cannon to shoot electronic sensors, and other systems including dynamics of impact with soil, as an engineer with Texas Instruments Inc. (TI). An analog/digital computer was the key to the success of the models. I became Corporate Energy Manager for (TI) in 1974 and continued to use this approach to define energy saving projects for over 30 million square feet of (TI) facilities. I also used the Control Data program ECUBE and DOE. I lost access to the analog/digital computer in 1982 when I left (TI) and only recently returned to an effort to model central chilled water systems using Excel; the only tool I have that can solve a set of simultaneous equations. My objective was and is to demonstrate the concept of (SEE) Modeling & (SEE) Schematics to the HVAC community believing the approach is a powerful and needed tool in the quest to improve the energy efficiency of buildings.Critical review is solicited.Best Regards, Kirby Nelson PE kirbynelsonpe@aol.comLife Member ASHRAE
(c) Base BuildingThe Chicago Large Office as defined by Pacific Northwest National Laboratory (PNNL) in their study of ASHRAE STD 90.1-2010 is chosen as the benchmark building for the (SEE) modeling analysis.The study by Pacific Northwest National Laboratory (PNNL) of ASHRAE Standard 90.1-2010 defines a large office building that is used as the base building for this study. The (PNNL) study defines the building characteristics, schedules, control, and HVAC equipment of the large office building defined here as the “ASHRAE Design”. Further the ASHRAE Journal of July 2011 defines “Optimizing Design & Control of Chilled Water Plants” by Taylor, which is used to define the plant of the “ASHRAE Design”. This (SEE) modeling analysis has found that the “ASHRAE Design” calls for design and control concepts that significantly increase the energy consumption of the system compared to a “(min kW) Design”. The “(min kW) Design” is, I believe, less first cost. The (PNNL) study can be viewed at;http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010
The (PNNL) study defines the building as given by Figure, a 13 story office with 498,600 square feet of air conditioned space.
FIGURE: Building description
Kirby Nelson PE Page 4
CHAPTER 1: Performance at peak day weather & 50F DB-45F WB
45 45 45 45 45 45 45 45 45 45 45 45
50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0
80.077.0 77.0 79.0
82.085.0
88.0 90.0 91.787.0
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76.0 75.0 73.076.0 78.0 79.0 80.0 81.0 81.8 80.0 79.0 78.0
3035404550556065707580859095100
3035404550556065707580859095
100
% Clear Sky
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ture
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)
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(Temp)wet bulb (Temp)dry bulb Peak day dry bulb F Peak day wet bulb F
FIGURE 1-1: Weather conditions
732 754 754658
788
1,110 1,109 1,125 1,144
705549
858
361 346 341 395
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1,696 1,743 1,8111,891
1,171
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(50F DB-45F WB) (kW) Design day (kW)
FIGURE 1-2: Total system kW
Figure 1-1 illustrates the two weather profiles to be evaluated in this chapter 1.
The total system kW is very different for the two conditions as illustrated by Figure 1-2. Perimeter heat is required at night resulting in greater kW demand for the winter conditions.
Kirby Nelson PE Page 5
Figure 1-3 gives the (SEE) schematic at 4PM at peak design hour. The peak system kW is also shown on Figure 1-2 above. This (SEE) schematic is
consistent with the laws of thermodynamics and the manufactures performance data. Nomenclature is given at the end of this paper.BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 47.55
Condenser # floors = 13 Tdry-bulb = 91.7 Infil-CFM = 6811 <(cond)ton= 543 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 81.8 Infilsen-ton = 11.5
TCR= 104.8 > gpmT= 1800 > (ewt)T= 103 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= 3.76TCR-app= 1.32 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 16.6 E/W wall ft2 = 27,008 WallStrans ton= 4.19
(COND)ton= 1086 PT-heat = -1.47 Trange= 14.5 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= 3.32(H)cond= 51.3 < pT-kW= 30.5 < (lwt)T = 89.0 tton-ex= -545 Glass U = 0.55 WallWtranston= 2.50 WallTot trans ton = 13.8
(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 7.2 T#= 2 Wall U = 0.09 GlassN trans ton = 13.04Ptower # = 2 T-Ton-ex= -1091 Glass SHGC = 0.40 GlassS trans ton = 13.04
Trg+app = 21.7 Wall emitt = 0.55 GlassE-trans ton = 8.68Compressor ASHRAE Design RoofTrans ton = 31.8 GlassW-trans ton = 8.68 GlassTot-trans-ton= 43.4
(chiller)kW= 279 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 62.0 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 100% Peak day Design 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 2 Weather %clear sky = 1.00 Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2
(CHILLER)kW= 558 conditions Tdry bulb = 91.7 (int-cfm)to-per-ret= 176135 BLD kW= 731.4 (int cfm)per-ton = 31.70 >(chiller)kW/ton= 0.607 Twet bulb = 81.8 Total Bldint-ton = 299.3 AHU kW= 499.7 Tot Bldper-sen-ton = 167.6 vPlant kW = 660.1 Tstat-int= 75.0 SITE kW = 1231.2 Tstat-per = 73.0 return
(Bld)int.air-ton= -299.3 ^ Design 4PM ^ (Bld)per.air-ton= -167.6 airTair supply int= 56.12 ASHRAE Design Tair supply per= 56.72
^ ABS Bld Ton = 466.89 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 459.9 (fan)int-ter= 17.7 62.4 (fan)per-ter= 17.7 62.4TER= 42.8 Theat-air= 55.0
TER-app= 1.29 (D)heat = 0.0 0.0 ^ EVAPton= 920 Treheat air = 55.0
(H)evap= 51.9 (D)reheat = 0.0 0.0(evap)ft/sec= 10.44 62.4
(evap)des-ft/sec= 10.44 (D)int-air-ton= -317.0 Interior (D)per-air-ton= -205.9 Peri ^ V Tair coils = 55.00 duct Tair coils= 55.00 duct
gpmevap= 1200 Psec-heat-ton = -2.4 (D)int-CFM= 176,135 ^ (D)per-CFM= 114,401 ^(lwt)evap = 44.06 > Psec-kW= 37.5 > (ewt)coil= 44.1 >>>(Coil)sen-ton= 644 ^ (coil)gpm= 42.5 ^
(H)pri-total= 61.4 v Efdes-sec-p = 0.80 (coil)cap-ton= 34.3 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.06 Efsec-pump = 0.78 (coil)H2O-ft/sec= 1.17 COIL UA= 2.61
(H)pri-fitings= 7.0 gpmbp= -96 (H)sec= 140 PLANTton = 908 (coil)des-ft/sec= 1.20 (one coil)ton= 34.91(Ef)c-pump= 0.81 (H)pri-bp= 0.02 (H)sec-pipe= 78 LMTD= 13.12 (H)coil= 2.0 VPc-heat-ton= -0.93 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 908 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 17.1 (ewt)evap = 62.45 < (gpm)sec= 1104 < (lwt)coil= 64.1 <<<< Tair VAV= 79.61 TBLD-AR = 73.00Pchiller-# = 2 (FAN)VAV-CFM= 290,536 (Air)ret-CFM = 297,347 Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 82.0 (FAN)ret-kW= 87 FanPerformance 4PM Design kW THERM (FAN)kW-VAV= 288 (FAN)ret-ton= 24.6 V
chillerkW/evapton= 0.607 BLD.kW= 731.4 ^ (Air)ret-ton = 506.3(plant)kW/site ton= 0.727 (Fan)kW = 499.7 26 F.A.Inlet ^ Tar-to-VAV = 73.92CCWSkW/bld ton= 2.48 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 423.5WeatherEin-ton = 648.0 (FA)heat= 0.0 0 TFA to VAV = 91.7 > Tret+FA = 76.48 InfilVAV-Lat-ton = 39.77(Site)kW-Ein-ton = 350.2 Heat total = 0.0 0.00 Tdry bulb = 91.7 >(FA)sen-ton = > 138.1 (dh) = 5.546 < VAVret-CFM = 248,719 <PlantkW-Ein-ton = 187.7 PlantkW= 660.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.657 InfilCFM-ton = 11.6 V
Total Ein-ton = 1186 SystkW = 1891.3 1891.3 Twet bulb = 81.8 > (FA)Lat-ton= 224.2Pumptot-heat-ton = -4.8 (FA)kW= 0.0 ExLat-ton = -7.8
AHU ExLat-ton = -7.8 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628AHU Exsen-ton = -82.8 CCWSkW = 1159.9 ton blue water temp pink TEx = 73.92Tower Tton-Ex = -1091 SystkW = 1891.3 air cfm purplewater gpm orange Exsen-ton = -82.8 V Total Eout-ton = -1186 air temp green kW red
FIGURE 1-3: (SEE) Schematic at peak design hour
Kirby Nelson PE Page 6
Figure 1-4 gives the (SEE) schematic for the condition of 50F DB & 45F WB. A careful review of the two schematics provides understanding of
why the system kW reduced about 750 kW.
BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 exfil-CFM = 6811 >>
(cond)ton= 303 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 66.5 > gpmT= 900 > (ewt)T= 65.4 tfan-kW= 8 N/S wall ft2 = 40,560 WallNtrans ton= -4.17
TCR-app= 1.17 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 303 PT-heat = -0.74 Trange= 8.08 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96
(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 57.3 tton-ex= -305 Glass U = 0.55 WallWtranston= -2.78 WallTot trans ton = -12.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 12.3 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03
Ptower # = 1 T-Ton-ex= -305 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 20.4 Wall emitt = 0.55 GlassE-trans ton = -10.68
Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 84 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 23.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 30% Peak day Design 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 100% Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2
(CHILLER)kW= 84 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 172581 BLD kW= 731 (int cfm)per-ton = 31.06 >(chiller)kW/ton= 0.304 Twet bulb = 45.0 Tot Bldint-ton = 292.9 AHU kW= 286 Tot Bldper-sen-ton = 18.1 vPlant kW = 126.1 Tstat-int= 75.0 SITE kW = 1017.9 Tstat-per = 73.0 return
(Bld)int.air-ton= -292.9 ^ Design 4PM ^ (Bld)per.air-ton= -18.1 airTair supply int= 56.14 ASHRAE Design Tair supply per= 63.91
^ ABS Bld Ton = 311.02 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 275.5 (fan)int-ter= 17.7 62.4 (fan)per-ter= 17.7 62.4TER= 43.3 Theat-air= 55.0
TER-app= 1.17 (D)heat = 0.0 0.0 ^ EVAPton= 276 Treheat air = 55.0
(H)evap= 51.9 (D)reheat = 0.0 0.0(evap)ft/sec= 10.44 62.4
(evap)des-ft/sec= 10.44 (D)int-air-ton= -310.6 Interior (D)per-air-ton= -39.8 Peri ^ V Tair coils = 55.00 duct Tair coils= 55.00 duct
gpmevap= 600 Psec-heat-ton = -1.6 (D)int-CFM= 172,581 ^ (D)per-CFM= 22,136 ^(lwt)evap = 44.52 > Psec-kW= 10.1 > (ewt)coil= 44.5 >>>(Coil)sen-ton= 272 ^ (coil)gpm= 12.7 ^
(H)pri-total= 61.9 v Efdes-sec-p = 0.80 (coil)cap-ton= 10.2 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.52 Efsec-pump = 0.43 (coil)H2O-ft/sec= 0.35 COIL UA= 1.27
(H)pri-fitings= 7.0 gpmbp= -269 (H)sec= 70.0 PLANTton = 272 (coil)des-ft/sec= 1.20 (one coil)ton= 10.47(Ef)c-pump= 0.81 (H)pri-bp= 0.50 (H)sec-pipe= 7 LMTD= 8.05 (H)coil= 0.2 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 272 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 8.6 (ewt)evap = 55.54 < (gpm)sec= 331 < (lwt)coil= 64.5 <<<< Tair VAV= 70.54 TBLD-AR = 73.00Pchiller-# = 1 (FAN)VAV-CFM= 194,717 (Air)ret-CFM = 201,528 Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 35.4 (FAN)ret-kW= 37 FanPerformance 4PM Design kW THERM (FAN)kW-VAV= 124 (FAN)ret-ton= 10.6 V
chillerkW/evapton= 0.304 BLD.kW= 731.4 ^ (Air)ret-ton = 337.1plantkW/site ton= 0.463 (Fan)kW = 286.5 26 F.A.Inlet ^ Tar-to-VAV = 73.58
CCWSkW/bld ton= 1.33 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 255.7WeatherEin-ton = 64.1 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 68.52 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 289.5 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -18.8 (dh) = 3.303 < VAVret-CFM = 152,900 <PlantkW-Ein-ton = 35.9 PlantkW= 126.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.608 InfilCFM-ton = 11.4 V
Total Ein-ton = 389 SystkW = 1144.0 1144.0 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.8 (FA)kW= 0.0 ExLat-ton = 0.0
AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628
AHU Exsen-ton = -81.3 CCWSkW = 412.5 ton blue water temp pink TEx = 73.58Tower Tton-Ex = -305 SystkW = 1144.0 air cfm purplewater gpm orange Exsen-ton = -81.3 V Total Eout-ton = -389 air temp green kW red
FIGURE 1-4: (SEE) Schematic at 50F DB-45F WB
Kirby Nelson PE Page 7
414500
551660
731 731
361 346 341 395
1,167
1,696 1,743 1,8111,891
1,171
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TIME OF DAYSYSTEM kW-All electric-498,600 sqft Bld-24 hr. Peak Day
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
FIGURE 1-5: System kW at peak dayFigure 1-5 gives the components that make up the system kW at peak day conditions and Figure 1-6 for the 50F/45F conditions.
731 731
263 286
115 126
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(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
FIGURE 1-6: System kW at 50F DB-45F WB
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DRY BULB (F)
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on)
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DIN
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W)
TIME OF DAYBUILDING (KW) & (TON) (Peak day)
(Bld) kW Bld sen.ton (Bld)Infil lat ton
FIGURE 1-7: Building loads-peak dayFigure 1-7 gives the building loads at peak design day and Figure 1-8 at 50F/45F conditions. The building kW demand is the same for both figures but the load (ton) is significantly less at 50F/45F as expected.
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BUIL
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W)
TIME OF DAYBUILDING (KW) & (TON)(50F DB-45F WB)
(Bld)kW Bld.sen.ton (Bld) Infil Lat ton
FIGURE 1-8: Building loads-50F DB 45F WB
Kirby Nelson PE Page 8
44.71 44.44 44.31 44.06 44.36 44.76 44.49 44.56 44.06 44.65 44.52 44.52
64.7
1
64.4
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64.0
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Total -EVAPORATOR TON
Wat
er Te
mp.
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Wat
er Te
mp.
(F)
Plant (ton)= 26-(Coil)Lat+sen-ton(Peak day) PRIMARY/SECONDARY PUMPING-Water temperatures (F)
Coil entering water (F) Evaporator leaving water (F) Bypass water(F)
Coil leaving water (F) Evap. Entering water (F)
FIGURE 1-9: P/S pumping Temperatures (F)Figure 1-9 gives the water temperatures at peak day conditions and Figure 1-10 for the 50F/45F conditions. The supply water into the coils is about 44.5F for both figures and the coil leaving water is about 64.5F. The water into the evaporator varies because of bypass water; however an economizer would be placed before the bypass pipe.
44.94 44.90 44.90 44.43 44.46 44.68 44.64 44.34 44.52 44.52 44.58 44.65
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64.9
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Total -EVAPORATOR TON
Wat
er Te
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(F)
Wat
er Te
mp.
(F)
Plant (ton)= 26-(Coil)Lat+sen-ton(50F DB & 45F WB) P/S PUMPING-Water temperatures (F)
Coil entering water (F) Evaporator leaving water (F) Bypass water(F)
Coil leaving water (F) Evap. Entering water (F)
FIGURE 1-10: P/S pumping Temperatures (F)
84.382.3
80.3
85.0
91.9
98.5 100.0101.8 103.5
95.798.2
89.7
79.8 78.676.7
80.183.5
86.1 87.1 88.1 89.085.7 86.0
82.7
3.83 3.57 3.74 4.055.47
7.10 7.07 7.10 7.185.73
7.01
4.74
0
5
10
15
20
60
70
80
90
100
110
Tower range + approach (F)
Tow
er a
ppro
ach
(F)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)Tower performance- peak design day
(ewt)tower (F) (lwt)tower (F) Tower approach (F)
FIGURE 1-11: Tower performanceFigure 1-11 provides the tower performance for peak day and Figure 1-12 for 50F/45F conditions. Figure 1-12 illustrates that the tower leaving water temperature (lwt) of about 52F to 57F offers an opportunity to cool the 64.5F water leaving the coils.
55.3 55.2 55.2 54.855.9
63.4 63.4 64.3 65.4
57.656.0
57.7
52.0 52.0 52.0 51.7 52.3
56.2 56.2 56.7 57.3
53.2 52.453.3
7.0 7.0 7.0 6.77.3
11.2 11.2 11.712.3
8.27.4
8.3
0
5
10
15
50
60
70
80
Tower range + approach (F)
Tow
er a
ppro
ach
(F)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)TOWER PERFORMANCE 50F DB-45F WB
(ewt)tower (F) (lwt)tower (F) Tower approach (F)
FIGURE 1-12: Tower performance
Kirby Nelson PE Page 9
52.0 52.0 52.0 51.7 52.3
56.2 56.2 56.7 57.3
53.2 52.453.3
64.9 64.9 64.9 64.4 64.5 64.7 64.6 64.3 64.5 64.5 64.6 64.7
40
45
50
55
60
65
70
40
45
50
55
60
65
70
Dry bulb (F)
Tow
er w
ater
tem
p. (F
)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)TOWER & COIL PERFORMANCE 50F DB-45F WB
(lwt)tower (F) (lwt)coil (F)
FIGURE 1-13: Temperatures of Coil & Tower water (F)Figure 1-13 gives the coil leaving water temperature verses the tower leaving water; clearly if we consider only these temperatures then opportunity exists for a water economizer.
1 1 1 1 1 1 1 1 1 1 1 1
39 39 39 39 42
73 73 78 84
47 42
47
77 77 77 77 80
115 115 120 126
8880
88
0
20
40
60
80
100
120
140
160
180
200
0
1
TOTAL EVAPORATOR TON
kW
# Nu
mbe
r Chi
llers
On
Total System Demand (kW)
CHILLER & PLANT PERFORMANCE-(50F DB & 45F WB)
# number chillers on Total Chiller-kW Plant (kW)
FIGURE 1-14: Chiller & Plant kWFigure 1-14 gives the chiller kW and we see that the maximum possible reduction in kW is from 39 to 84kW to eliminate the chiller operation at these 50F/45F conditions.
Figure 1-14 also gives the total system kW and we see that the maximum possible reduction is about 5% to 7% of the total system kW. However Figure 1-13 illustrates that the tower could only provide about a 50% reduction in evaporator load if supply water is 44F.Figure 1-15 illustrates that the chiller kW/ton is very good, about .30 to .36kW/ton.
0.36
4
0.36
6
0.36
6
0.39
5
0.35
6
0.29
8
0.29
9
0.30
4
0.30
4
0.32
3
0.35
1
0.31
9
0.73
4
0.73
8
0.73
8
0.79
5
0.69
9
0.47
8
0.47
9
0.47
4
0.46
3 0.60
6
0.69
0
0.60
0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
TOTAL EVAPORATOR TON
kW/T
ON
kW/t
on
PLANT TONCHILLER & PLANT kW/ton at 50F DB & 45F WB
Chiller kW/evaporator ton Plant kW/plant ton
FIGURE 1-15: Chiller & Plant kW/ton
Figure 1-16 gives the chiller lift and chiller kW for peak day and the 50F/45F conditions, a value that varies from about 12.4F to 23.2F for the 50F/45F conditions. A further drop in lift due to a water economizer could cause the chiller to surge and/or a significant increase in chiller kW/ton.
Kirby Nelson PE Page 10
12.4 12.4 12.4 12.5 13.5
21.0 21.0 22.2 23.2
15.3 13.5 15.2
41.8 40.0 38.243.1
49.9
56.2 58.0 59.862.0
53.556.1
47.4
39 39 39 39 4273 73 78 84
47 42 47106 99 95 112
324
458486
519558
380
226
140
0
100
200
300
400
500
600
700
800
0
10
20
30
40
50
60
70
Time of Day
kW
Chill
er Li
ft (F
)
Time of Day
Chiller performance at peak day & 50F DB-45F WB
Chiller Lift (50F DB-45F WB) Chiller Lift (Peak day)Total Chiller-kW(50F DB-45F WB) Total Chiller (kW)(Peak day)
FIGURE 1-16: Chiller Performance
CONCLUSIONConsidering that a water economizer only offers a maximum opportunity of 5% to 7% if all chiller kW is eliminated by an economizer and for this case only about 2.5% to 3.5% as illustrated by Figure 1-13; the author arrives at the conclusion; the cost, complexity, and control of a water economizer for the Chicago large office as defined by the Pacific Northwest National Laboratory (PNNL) study of 90.1-2010 is not a good idea. However other control concepts are suggested by Taylor and Nall that will change the system response. Increasing supply air temperature, increasing supply water temperature, effects of solar load and also a decrease in outside temperature below 50F/45F will change the system response.Chapter 2 will address increasing supply air temperature.Kirby Nelson P.E.Life Member ASHRAE
Kirby Nelson PE Page 11
CHAPTER 2: Performance at 50F DB-45F WB & supply air temperature of 55F & 60F
45 45 45 45 45 45 45 45 45 45 45 45
50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0
3035404550556065707580859095100
3035404550556065707580859095
100
% Clear Sky
AIR
TEM
Pera
ture
(F)
Air T
empe
ratu
re (F
)
TIME OF DAY
WEATHER
(Temp)wet bulb (Temp)dry bulb (Temp) dry bulb F (Temp) wet bulb F
FIGURE 2-1: Weather conditions
732 754 754658
788
1,110 1,109 1,125 1,144
705
549
858656 678 678598
811
1,244 1,243 1,274 1,315
740
567
786
0
200
400
600
800
1000
1200
1400
1600
0
200
400
600
800
1000
1200
1400
1600
% Clear Sky
Syst
em (k
W)
Syst
em (k
W)
TIME of DAY
SYSTEM TOTAL (kW)
(50F DB-45F WB)55F supply air (kW) (50F DB-45F WB) 60F supply air (kW)
FIGURE 2-2: Total system kW
Figure 2-1 illustrates the weather profiles are the same to be evaluated in this chapter 2.
Figure 2-2 illustrates that the system kW increased with 60F supply air during the day and decreased during night time operation.
Kirby Nelson PE Page 12
Figure 2-3 gives the (SEE) schematic at 4PM with 55F supply air. The system kW is also shown on Figure 2-2 above.
BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 exfil-CFM = 6811 >>
(cond)ton= 303 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 66.5 > gpmT= 900 > (ewt)T= 65.4 tfan-kW= 8 N/S wall ft2 = 40,560 WallNtrans ton= -4.17
TCR-app= 1.17 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 303 PT-heat = -0.74 Trange= 8.08 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96
(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 57.3 tton-ex= -305 Glass U = 0.55 WallWtranston= -2.78 WallTot trans ton = -12.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 12.3 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03
Ptower # = 1 T-Ton-ex= -305 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 20.4 Wall emitt = 0.55 GlassE-trans ton = -10.68
Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 84 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 23.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 30% 50F/45F 55F supply 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 100% Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2
(CHILLER)kW= 84 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 172581 BLD kW= 731 (int cfm)per-ton = 31.06 >(chiller)kW/ton= 0.304 Twet bulb = 45.0 Tot Bldint-ton = 292.9 AHU kW= 286 Tot Bldper-sen-ton = 18.1 vPlant kW = 126.1 Tstat-int= 75.0 SITE kW = 1017.9 Tstat-per = 73.0 return
(Bld)int.air-ton= -292.9 ^ 55F supply 4PM ^ (Bld)per.air-ton= -18.1 airTair supply int= 56.14 ASHRAE Design Tair supply per= 63.91
^ ABS Bld Ton = 311.02 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 275.5 (fan)int-ter= 17.7 62.4 (fan)per-ter= 17.7 62.4TER= 43.3 Theat-air= 55.0
TER-app= 1.17 (D)heat = 0.0 0.0 ^ EVAPton= 276 Treheat air = 55.0
(H)evap= 51.9 (D)reheat = 0.0 0.0(evap)ft/sec= 10.44 62.4
(evap)des-ft/sec= 10.44 (D)int-air-ton= -310.6 Interior (D)per-air-ton= -39.8 Peri ^ V Tair coils = 55.00 duct Tair coils= 55.00 duct
gpmevap= 600 Psec-heat-ton = -1.6 (D)int-CFM= 172,581 ^ (D)per-CFM= 22,136 ^(lwt)evap = 44.52 > Psec-kW= 10.1 > (ewt)coil= 44.5 >>>(Coil)sen-ton= 272 ^ (coil)gpm= 12.7 ^
(H)pri-total= 61.9 v Efdes-sec-p = 0.80 (coil)cap-ton= 10.2 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.52 Efsec-pump = 0.43 (coil)H2O-ft/sec= 0.35 COIL UA= 1.27
(H)pri-fitings= 7.0 gpmbp= -269 (H)sec= 70.0 PLANTton = 272 (coil)des-ft/sec= 1.20 (one coil)ton= 10.47(Ef)c-pump= 0.81 (H)pri-bp= 0.50 (H)sec-pipe= 7 LMTD= 8.05 (H)coil= 0.2 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 272 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 8.6 (ewt)evap = 55.54 < (gpm)sec= 331 < (lwt)coil= 64.5 <<<< Tair VAV= 70.54 TBLD-AR = 73.00Pchiller-# = 1 (FAN)VAV-CFM= 194,717 (Air)ret-CFM = 201,528 Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 35.4 (FAN)ret-kW= 37 FanPerformance 4PM 55F supply kW THERM (FAN)kW-VAV= 124 (FAN)ret-ton= 10.6 V
chillerkW/evapton= 0.304 BLD.kW= 731.4 ^ (Air)ret-ton = 337.1plantkW/site ton= 0.463 (Fan)kW = 286.5 26 F.A.Inlet ^ Tar-to-VAV = 73.58
CCWSkW/bld ton= 1.33 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 255.7WeatherEin-ton = 64.1 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 68.52 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 289.5 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -18.8 (dh) = 3.303 < VAVret-CFM = 152,900 <PlantkW-Ein-ton = 35.9 PlantkW= 126.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.608 InfilCFM-ton = 11.4 V
Total Ein-ton = 389 SystkW = 1144.0 1144.0 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.8 (FA)kW= 0.0 ExLat-ton = 0.0
AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628
AHU Exsen-ton = -81.3 CCWSkW = 412.5 ton blue water temp pink TEx = 73.58Tower Tton-Ex = -305 SystkW = 1144.0 air cfm purplewater gpm orange Exsen-ton = -81.3 V Total Eout-ton = -389 air temp green kW red
FIGURE 2-3: 4PM (SEE) Schematic at 50F DB 45F WB with 55F supply air
Kirby Nelson PE Page 13
Figure 2-4 gives the (SEE) schematic for the condition of 50F DB & 45F WB & 60F supply air. A careful review of the two schematics provides understanding of why the system kW
increased about 170 kW with 60F supply air. The following discussion and charts will help understand why.
BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 Infil-CFM = 6811 <
(cond)ton= 351 Pipesize-in =6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 69.2 > gpmT= 900 > (ewt)T= 68 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.17
TCR-app= 1.19 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8.3 E/W wall ft2 = 27,008 WallStrans ton= -3.73(COND)ton= 351 PT-heat = -0.74 Trange= 9.3 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -1.96
(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 58.7 tton-ex= -353 Glass U = 0.55 WallWtranston= -2.78 WallTot trans ton = -12.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 13.7 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03
Ptower # = 1 T-Ton-ex= -353 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 23.0 Wall emitt = 0.55 GlassE-trans ton = -10.68
Compressor ASHRAE Design RoofTrans ton = 25.4 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 101 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 7.1(chiller)lift= 26.2 Large Office Peopleton = 60 kW GlassS-solar-ton = 22.3(chiller)%= 36% 50F/45F 60F supply 4PM plugton = 93 328 GlassE-solar ton = 4.7(chiller)#= 1 Weather %clear sky = 1.00 Lightton= 115 404 GlassW-solar ton = 33.1 GlassTot-solar-ton = 67.2
(CHILLER)kW= 101 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 230108 BLD kW= 731.4 (int cfm)per-ton = 41.42 >(chiller)kW/ton= 0.316 Twet bulb = 45.0 Total Bldint-ton = 292.9 AHU kW= 440.2 Tot Bldper-sen-ton = 28.5 vPlant kW = 143.1 Tstat-int= 75.0 SITE kW = 1171.7 Tstat-per = 73.0 return
(Bld)int.air-ton= -292.9 ^ 60F supply 4PM ^ (Bld)per.air-ton= -28.5 airTair supply int= 60.86 ASHRAE Design Tair supply per= 64.99
^ ABS Bld Ton = 321.38 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 318.3 (fan)int-ter= 17.7 62.4 (fan)per-ter= 17.7 62.4TER= 43.0 Theat-air= 60.0
TER-app= 1.19 (D)heat = 0.0 0.0 ^ EVAPton= 318 Treheat air = 60.0
(H)evap= 51.9 (D)reheat = 0.0 0.0(evap)ft/sec= 10.44 62.4
(evap)des-ft/sec= 10.44 (D)int-air-ton= -310.6 Interior (D)per-air-ton= -53.3 Peri ^ V Tair coils = 60.00 duct Tair coils= 60.00 duct
gpmevap= 600 Psec-heat-ton = -1.5 (D)int-CFM= 230,108 ^ (D)per-CFM= 39,501 ^(lwt)evap = 44.22 > Psec-kW= 10.5 > (ewt)coil= 44.2 >>>(Coil)sen-ton= 315 ^ (coil)gpm= 14.7 ^
(H)pri-total= 61.7 v Efdes-sec-p = 0.80 (coil)cap-ton= 16.5 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.22 Efsec-pump = 0.48 (coil)H2O-ft/sec= 0.40 COIL UA= 1.38
(H)pri-fitings= 7.0 gpmbp= -218 (H)sec= 70 PLANTton = 315 (coil)des-ft/sec= 1.20 (one coil)ton= 12.11(Ef)c-pump= 0.81 (H)pri-bp= 0.33 (H)sec-pipe= 9 LMTD= 11.92 (H)coil= 0.2 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 315 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 8.6 (ewt)evap = 56.96 < (gpm)sec= 382 < (lwt)coil= 64.2 <<<< Tair VAV= 72.98 TBLD-AR = 73.00Pchiller-# = 1 (FAN)VAV-CFM= 269,608 (Air)ret-CFM = 276,419 Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= 69.0 (FAN)ret-kW= 73 FanPerformance 4PM 60F supply kW THERM (FAN)kW-VAV= 243 (FAN)ret-ton= 20.7 V
chillerkW/evapton= 0.316 BLD.kW= 731.4 ^ (Air)ret-ton = 344.1(plant)kW/site ton= 0.454 (Fan)kW = 440.2 26 F.A.Inlet ^ Tar-to-VAV = 73.83CCWSkW/bld ton= 1.82 Ductheat= 0.0 0.00 statFA= 42 26 VAV FANS VAVret-ton = 283.6WeatherEin-ton = 42.2 (FA)heat= 0.0 0 TFA to VAV = 50.0 > Tret+FA = 70.14 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 333.2 Heat total = 0.0 0.00 Tdry bulb = 50.0 >(FA)sen-ton = > -37.6 (dh) = 4.961 < VAVret-CFM = 227,791 <PlantkW-Ein-ton = 40.7 PlantkW= 143.1 Fresh air > >>> > (FA)CFM= 41,817 > Efan-VSD= 0.648 InfilCFM-ton = 8.5 V
Total Ein-ton = 416 SystkW = 1314.8 1314.8 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.7 (FA)kW= 0.0 ExLat-ton = 0.0
AHU ExLat-ton = 0.0 BLD.kW= 731.4 SEE SCHEMATIC ExCFM = -48,628AHU Exsen-ton = -60.5 CCWSkW = 583.4 ton blue water temp pink TEx = 73.83Tower Tton-Ex = -353 SystkW = 1314.8 air cfm purplewater gpm orange Exsen-ton = -60.5 V Total Eout-ton = -416 air temp green kW red
FIGURE 2-4: 4PM (SEE) Schematic at 50F DB-45F WB-(60F supply air)
Kirby Nelson PE Page 14
386 440
126 143
731 731656 678 678
598
811
1,244 1,243 1,274 1,315
740
567
786
0.00 0.00 0
200
400
600
800
1000
1200
1400
1600
0
200
400
600
800
1000
1200
1400
1600
DRY BULB (F)
(kW
)
kW
TIME OF DAYSYSTEM kW-60F supply air
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
FIGURE 2-5: System kW with 60F supply airFigure 2-5 gives the components that make up the system kW with 60F supply air and Figure 2-6 for 55F supply air.The charts illustrate that during the day the air handler kW increase with 60F supply air drives the system kW increase. At night the perimeter reheat is reduced with 60F supply air resulting in a decrease in system kW.
731 731
263 286
115 126
732 754 754658
788
1,110 1,109 1,1251,144
705549
858
0 0 0
200
400
600
800
1000
1200
1400
1600
0
200
400
600
800
1000
1200
1400
1600
Dry bulb (F)
(kW
)
TIME OF DAY
SYSTEM kW-55F supply air
(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
FIGURE 2-6: System kW with 55F supply air
731
110
305 321
050100150200250300350400450500550600
0
100
200
300
400
500
600
700
800
DRY BULB (F)
BUIL
DIN
G (t
on)
BUIL
DIN
G (k
W)
TIME OF DAYBUILDING (KW) & (TON) (50F DB-45F WB)(60F supply air)
(Bld) kW Bld sen.ton (Bld)Infil lat ton
FIGURE 2-7: Building loads-60F supplyFigure 2-7 gives the building loads with 60F supply air and Figure 2-8 with 55F supply air. The building kW demand and load (ton) is the same for both figures.
168
731
295 311
050100150200250300350400450500550600
0
100
200
300
400
500
600
700
800
DRY BULB (F)
BUIL
DIN
G (t
on)
BUIL
DIN
G (k
W)
TIME OF DAYBUILDING (KW) & (TON)(50F DB-45F WB)(55F supply air)
(Bld)kW Bld.sen.ton (Bld) Infil Lat ton
FIGURE 2-8: Building loads-55F supply
Kirby Nelson PE Page 15
286
440272
314.9
0
50
100
150
200
250
300
350
400
0
100
200
300
400
500
600
700
800
Dry bulb (F)
TON
(kW
)
TIME OF DAY
(AHU) kW & Plant Load (Ton) (55F & 60F supply air)
(AHU)Total kW (55F supply air) (AHU)Total kW(60F supply air)
Plant load Ton (55F supply air) Plant load Ton (60F supply air)
FIGURE 2-9: (AHU) kW & plant (ton) for 55F & 60F supply air
37
286
0
125
124
0
50
100
150
200
250
300
350
400
450
500
550
0
50
100
150
200
250
300
350
400
450
500
550
(AHU) Total kW
(kW
)
(kW
)
TIME OF DAY
(AHU) total kW-55F supply air
Return fanl kW (AHU)Total kW Duct reheat (kW) Terminal fans (kW)
Duct heat (kW) VAV Fans (kW) Fresh Air (kW)
FIGURE 2-10: (AHU) total kW 55F supply air
Figure 2-9 illustrates that 60F supply air gives a reduction in load and total (AHU) kW during night operation and an increase during the day when solar load is occurring. Figures 2-10 & 2-11 further illustrate. Raising supply air to 60F reduces duct reheat kW more than the increase in VAV fans kW during night hours when perimeter heat is required. Perimeter heat is not required during the day, due to solar, stat set points and return air path, and therefore the increase in VAV fans kW drives total kW to a greater value than for 55F supply air.
73
440
0
125
243
0
50
100
150
200
250
300
350
400
450
500
550
0
50
100
150
200
250
300
350
400
450
500
550
(AHU) Total kW
(kW
)
(kW
)
TIME OF DAY(AHU) total kW-60F supply air
Return fanl kW (AHU)Total kW Duct reheat (kW) Terminal fans (kW)
Duct heat (kW) VAV Fans (kW) Fresh Air (kW)
FIGURE 2-11: (AHU) total kW 60F supply airIn later Chapters we will investigate the effect of low solar load and also the effect of stat set points and return air path.
Kirby Nelson PE Page 16
44.43 44.40 44.40 44.28 44.33 44.72 44.67 44.51 44.22 44.21 44.35 44.18
64.4
3
64.4
0
64.4
0
64.2
8
64.3
3
64.7
2
64.6
7
64.5
1
64.2
2
64.2
1
64.3
5
64.1
8
47.8
9
47.8
3
47.8
3
47.5
8
49.2
8
55.8
2
55.7
4
56.3
1
56.9
6
50.4
6
49.3
1
49.3
4
40
45
50
55
60
65
70
40
45
50
55
60
65
70
Total -EVAPORATOR TON
Wat
er Te
mp.
(F)
Wat
er Te
mp.
(F)
Plant (ton)= 26-(Coil)Lat+sen-ton(60F supply air) PRIMARY/SECONDARY PUMPING-Water temperatures (F)
Coil entering water (F) Evaporator leaving water (F) Bypass water(F)
Coil leaving water (F) Evap. Entering water (F)
FIGURE 2-12: P/S pumping Temperatures (F)Figure 2-12 & 2-13 gives the water temperatures for 55F & 60F supply air. The supply water into the coils is about 44.5F for both figures and the coil leaving water is about 64.5F. The water into the evaporator is about the same for both supply air conditions & varies because of bypass water; however an economizer would be placed before the bypass pipe.
44.94 44.90 44.90 44.43 44.46 44.68 44.64 44.34 44.52 44.52 44.58 44.65
64.9
4
64.9
0
64.9
0
64.4
3
64.4
6
64.6
8
64.6
4
64.3
4
64.5
2
64.5
2
64.5
8
64.6
5
49.2
4
49.1
8
49.1
8
48.3
8
49.1
7
54.4
1
54.3
5
54.6
3
55.5
4
50.4
1
49.3
5
50.5
9
40
45
50
55
60
65
70
40
45
50
55
60
65
70
Total -EVAPORATOR TON
Wat
er Te
mp.
(F)
Wat
er Te
mp.
(F)
Plant (ton)= 26-(Coil)Lat+sen-ton(55F supply air) P/S PUMPING-Water temperatures (F)
Coil entering water (F) Evaporator leaving water (F) Bypass water(F)
Coil leaving water (F) Evap. Entering water (F)
FIGURE 2-13: P/S pumping Temp. (F) with 55F supply air
54.1 54.0 54.0 53.8
56.2
65.5 65.466.6 68.0
58.256.2
56.6
51.4 51.3 51.3 51.252.5
57.3 57.3 57.9 58.7
53.552.5 52.7
6.37 6.34 6.34 6.247.50
12.35 12.3312.92
13.68
8.517.51 7.67
0
5
10
15
50
60
70
80
Tower range + approach (F)
Tow
er a
ppro
ach
(F)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)TOWER PERFORMANCE 60F supply air
(ewt)tower (F) (lwt)tower (F) Tower approach (F)
FIGURE 2-14: Tower performanceFigure 2-14 & 2-15 provides the tower performance for 60F & 55F supply air. The tower leaving water is about the same for both supply air conditions; increasing supply air temperature has little effect on tower performance.
55.3 55.2 55.2 54.855.9
63.4 63.4 64.3 65.4
57.656.0
57.7
52.0 52.0 52.0 51.7 52.3
56.2 56.2 56.7 57.3
53.2 52.453.3
7.0 7.0 7.0 6.77.3
11.2 11.2 11.712.3
8.27.4
8.3
0
5
10
15
50
60
70
80
Tower range + approach (F)
Tow
er a
ppro
ach
(F)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)TOWER PERFORMANCE 55F supply air
(ewt)tower (F) (lwt)tower (F) Tower approach (F)
FIGURE 2-15: Tower performance
Kirby Nelson PE Page 17
51.99 51.97 51.97 51.74 52.31
56.25 56.24 56.71 57.29
53.22 52.3653.27
64.94 64.90 64.90 64.43 64.46 64.68 64.64 64.34 64.52 64.52 64.58 64.65
40
45
50
55
60
65
70
40
45
50
55
60
65
70
Coil (lwt)F for 60F supply air
Tow
er w
ater
tem
p. (F
)
Tow
er w
ater
tem
p. (F
)
Tower (lwt)F-60F supply airTOWER & COIL PERFORMANCE 55F & 60F supply air
(lwt)tower (F)-55F supply air (lwt)coil (F)-55F supply air
FIGURE 2-16: Temperatures of Coil & Tower water (F)Figure 2-16 gives the coil leaving water temperature verses the tower leaving water for both 55F & 60F supply air; clearly if we consider only these temperatures then opportunity exists for a water economizer.
1 1 1 1 1 1 1 1 1 1 1 1
39 39 39 39 42
73 73 78 84
47 42
47
77 77 77 77 80
115 115 120 126
8880
88
0
20
40
60
80
100
120
140
160
180
200
0
1
TOTAL EVAPORATOR TON
kW
# Nu
mbe
r Chi
llers
On
Total System Demand (kW)
CHILLER & PLANT PERFORMANCE-(55F supply air))
# number chillers on Total Chiller-kW Plant (kW)
FIGURE 2-17: Chiller & Plant kW-55F supply airFigures 2-17 & 2-18 give the chiller kW and we see that the maximum possible reduction in kW is from 39 to 84kW for the 55F supply air operation
and 38 to 143 kW for the 60F supply air operation i.e. eliminate the chiller operation. Figure 2-17 &2-18 also gives the total system kW and we see that the maximum possible reduction is about 5% to 8% of the total system kW. However Figure 2-16 illustrates that the tower could only provide about a 50% reduction in evaporator load if supply water is 44F.
1 1 1 1 1 1 1 1 1 1 1 1
38 38 38 38 43
84 8491
101
5043
45
75 75 75 7482
126 126133
143
9182 84
0
20
40
60
80
100
120
140
160
180
200
0
0
0
0
0
1
1
1
1
1
1
TOTAL EVAPORATOR TON
kW
# N
umbe
r Chi
llers
On
Total System Demand kW
CHILLER & PLANT PERFORMANCE (60F supply air)
# number chillers on Total Chiller-kW Plant (kW)
FIGURE 2-18: Chiller & plant kW-60F supply air
The following four tables illustrate that raising the supply air temperature from 55F to 60F has a slight negative 24 hour effect.The increase in system kW at 4PM is significant but the 24 hour effect is only about a 3% increase in kWh by increasing supply air to 60F.
Kirby Nelson PE Page 18
Chicago 4PM All ElectricPerformance 4PM 55F supply kW
chillerkW/evapton= 0.304 BLD.kW= 731.4plantkW/site ton= 0.463 (Fan)kW = 286.5
CCWSkW/bld ton= 1.33 Ductheat= 0.0WeatherEin-ton = 64.1 (FA)heat= 0.0(Site)kW-Ein-ton = 289.5 Heat total = 0.0PlantkW-Ein-ton = 35.9 PlantkW= 126.1
Total Ein-ton = 389 SystkW = 1144.0Pumptot-heat-ton = -2.8
AHU ExLat-ton = 0.0 BLD.kW= 731.4AHU Exsen-ton = -81.3 CCWSkW = 412.5Tower Tton-Ex = -305 SystkW = 1144.0Total Eout-ton = -389
Table 2-1: 4PM-55F supply air
BLD sq-ft = 498,600ALL ELECTRIC 50F/45F
55F supply 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 3,921(Duct)24hr-heat kW= 4,313
(FA)24hr-heat kW= 0Heat24hr-total kW= 4,313
Plant24hr-kW= 2,240SYST 24hr-kW = 20,570
(CCWS)24hr-kW= 10,473BLD.24hr-kW= 10,096
Total24hr-kW = 20,570Weather24h-Ein-ton= -217SITE24h-kW-Ein-ton = 5213Plant24h-kW-Ein-ton = 637Total24h-Ein-ton = 5633Pump24hr-heat-ton = -63
AHU Ex24hr-Lat-ton = 0AHU Ex24hr-sen-ton = -1119
Tower24hr-ton-Ex = -4451Total E24hr-out-ton = -5633
Table 2-2: 24 hr-55F supply
Chicago 4PM All ElectricPerformance 4PM 60F supply kW
chillerkW/evapton= 0.316 BLD.kW= 731.4(plant)kW/site ton= 0.454 (Fan)kW = 440.2CCWSkW/bld ton= 1.82 Ductheat= 0.0WeatherEin-ton = 42.2 (FA)heat= 0.0(Site)kW-Ein-ton = 333.2 Heat total = 0.0PlantkW-Ein-ton = 40.7 PlantkW= 143.1
Total Ein-ton = 416 SystkW = 1314.8Pumptot-heat-ton = -2.7
AHU ExLat-ton = 0.0 BLD.kW= 731.4AHU Exsen-ton = -60.5 CCWSkW = 583.4Tower Tton-Ex = -353 SystkW = 1314.8Total Eout-ton = -416
Table2-3: 4PM-60F supply
BLD sq-ft = 498,600ALL ELECTRIC 50F/45F
60F supply 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 5,165(Duct)24hr-heat kW= 3,584
(FA)24hr-heat kW= 0Heat24hr-total kW= 3,584
Plant24hr-kW= 2,331SYST 24hr-kW = 21,176
(CCWS)24hr-kW= 11,079BLD.24hr-kW= 10,096
Total24hr-kW = 21,176Weather24h-Ein-ton= -519SITE24h-kW-Ein-ton = 5360Plant24h-kW-Ein-ton = 663Total24h-Ein-ton = 5504Pump24hr-heat-ton = -60
AHU Ex24hr-Lat-ton = 0AHU Ex24hr-sen-ton = -825
Tower24hr-ton-Ex = -4619Total E24hr-out-ton = -5504
Table 2-4: 24 hr-60F supply
Following are schematics at 4AM.
Kirby Nelson PE Page 19
Figure 2-19 gives the system schematic at 4AM with 55F supply air. Note the required perimeter heat kW is 457.2 & the perimeter stat is set at 73F & interior at 75F. The terminal
fans are assumed as controlled off which may be a bad assumption, however not much would change if we turn the terminal fans on.
BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 exfil-CFM = 6811 >>
(cond)ton= 122 Pipesize-in = 6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 56.3 > gpmT= 900 > (ewt)T= 55.2 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.37
TCR-app= 1.06 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8.3 E/W wall ft2 = 27,008 WallStrans ton= -4.37(COND)ton= 122 PT-heat = -0.74 Trange= 3.2 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -2.91
(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 52.0 tton-ex= -124 Glass U = 0.55 WallWtranston= -2.91 WallTot trans ton = -14.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 7.0 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03
Ptower # = 1 T-Ton-ex= -124 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 10.2 Wall emitt = 0.55 GlassE-trans ton = -10.68
Compressor ASHRAE Design RoofTrans ton = -4.6 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 39 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 0.0(chiller)lift= 12.4 Large Office Peopleton = 0 kW GlassS-solar-ton = 0.0(chiller)%= 14% 50F/45F 55F supply 4AM plugton = 41 146 GlassE-solar ton = 0.0(chiller)#= 1 Weather %clear sky = 100% Lightton= 6 22 GlassW-solar ton = 0.0 GlassTot-solar-ton = 0.0
(CHILLER)kW= 39 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 19194 BLD kW= 168.0 (int cfm)per-ton = 12.09 >(chiller)kW/ton= 0.366 Twet bulb = 45.0 Total Bldint-ton = 43.2 AHU kW= 508.8 Tot Bldper-sen-ton = -70.0 vPlant kW = 77.0 Tstat-int= 80.0 SITE kW = 676.9 Tstat-per = 73.0 return
(Bld)int.air-ton= -43.2 ^ 55F supply 4AM ^ (Bld)per.air-ton= 70.0 airTair supply int= 55.00 ASHRAE Design Tair supply per= 94.00
^ ABS Bld Ton = 113.18 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 106.9 (fan)int-ter= 0.0 0.0 (fan)per-ter= 0.0 0.0TER= 43.8 Theat-air= 94.0
TER-app= 1.06 (D)heat = 70.0 246.2 ^ EVAPton= 107 Treheat air = 80.0
(H)evap= 51.9 (D)reheat = 60.0 211.0(evap)ft/sec= 10.44 457.2
(evap)des-ft/sec= 10.44 (D)int-air-ton= -43.2 Interior (D)per-air-ton= -83.3 Peri ^ V Tair coils = 55.00 duct Tair coils= 55.00 duct
(bEQ)day gpmevap= 600 Psec-heat-ton = -1.12 (D)int-CFM= 19,194 ^ (D)per-CFM= 37,035 ^(lwt)evap = 44.90 > Psec-kW= 5.6 > (ewt)coil= 44.9 >>>(Coil)sen-ton= 104 ^ (coil)gpm= 4.9 ^
(H)pri-total= 62.9 v Efdes-sec-p = 0.80 (coil)cap-ton= 7.5 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.90 Efsec-pump = 0.30 (coil)H2O-ft/sec= 0.14 COIL UA= 0.72
(H)pri-fitings= 7.0 gpmbp= -472 (H)sec= 70.0 PLANTton = 104 (coil)des-ft/sec= 1.20 (one coil)ton= 4.01(Ef)c-pump= 0.81 (H)pri-bp= 1.55 (H)sec-pipe= 1 LMTD= 10.40 (H)coil= 0.0 VPc-heat-ton= -0.47 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 104 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 8.8 (ewt)evap = 49.18 < (gpm)sec= 128 < (lwt)coil= 64.9 <<<< Tair VAV= 75.62 TBLD-AR = 73.00Pchiller-# = 1 (FAN)VAV-CFM= 56,229 (Air)ret-CFM = 63,040 Return
Chicago 4AM All Electric Fuel Heat (FAN)ton-VAV= 11.3 (FAN)ret-kW= 12 FanPerformance 4AM 55F supply kW THERM (FAN)kW-VAV= 40 (FAN)ret-ton= 3.4 V
chillerkW/evapton= 0.366 BLD.kW= 168.0 ^ (Air)ret-ton = 105.5plantkW/site ton= 0.738 (Fan)kW = 51.7 26 F.A.Inlet ^ Tar-to-VAV = 73.60
CCWSkW/bld ton= 5.18 Ductheat= 457.2 19.50 statFA= 42 26 VAV FANS VAVret-ton = 93.3WeatherEin-ton = -75.9 (FA)heat= 0.0 0.00 TFA to VAV = 50.0 > Tret+FA = 73.39 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 192.5 Heat total = 457.2 19.50 Tdry bulb = 50.0 >(FA)sen-ton = > -0.2 (dh) = 2.600 < VAVret-CFM = 55,731 <PlantkW-Ein-ton = 21.9 PlantkW= 77.0 Fresh air > >>> > (FA)CFM= 499 > Efan-VSD= 0.432 InfilCFM-ton = 11.4 V
Total Ein-ton = 139 SystkW = 753.9 296.7 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.3 (FA)kW= 0.0 ExLat-ton = 0.0
AHU ExLat-ton = 0.0 BLD.kW= 168.0 SEE SCHEMATIC ExCFM = -7,309AHU Exsen-ton = -12.2 CCWSkW = 585.9 ton blue water temp pink TEx = 73.60Tower Tton-Ex = -124 SystkW = 753.9 air cfm purplewater gpm orange Exsen-ton = -12.2 V Total Eout-ton = -139 air temp green kW red
FIGURE 2-19: 4AM (SEE) Schematic at 50F DB 45F WB with 55F supply air
Kirby Nelson PE Page 20
Figure 2-20 is for 60F supply air and perimeter heat kW reduces to 381.4 verses 457.2 of Figure 2-19 above. Raising the supply air temperature
typically increases fan kW and reduces perimeter heat kW; however other variables are involved as discussed in conclusions below.
BLD ft2 = 498600 %clear sky = 100.0% InfilLat-ton = 0.00Condenser # floors = 13 Tdry-bulb = 50.0 exfil-CFM = 6811 >>
(cond)ton= 100 Pipesize-in = 6" (H)T-pipe= 13.5 Tower Roof ft2 = 38,354 Twet-bulb= 45.0 Infilsen-ton = -14.1TCR= 55.1 > gpmT= 900 > (ewt)T= 54.0 tfan-kW= 8.3 N/S wall ft2 = 40,560 WallNtrans ton= -4.37
TCR-app= 1.05 (H)T-total= 74.7 (H)T-static = 9.9 Tfan-kW= 8.3 E/W wall ft2 = 27,008 WallStrans ton= -4.37(COND)ton= 100 PT-heat = -0.74 Trange= 2.7 tfan-%= 100% Wall % glass= 37.5% WallEtrans ton= -2.91
(H)cond= 51.3 < pT-kW= 15.2 < (lwt)T = 51.3 tton-ex= -102 Glass U = 0.55 WallWtranston= -2.91 WallTot trans ton = -14.6(cond)ft/sec= 10.8 EfTpump= 0.83 Tapproach = 6.3 T#= 1 Wall U = 0.09 GlassN trans ton = -16.03
Ptower # = 1 T-Ton-ex= -102 Glass SHGC = 0.40 GlassS trans ton = -16.03Trg+app = 9.0 Wall emitt = 0.55 GlassE-trans ton = -10.68
Compressor ASHRAE Design RoofTrans ton = -4.6 GlassW-trans ton = -10.68 GlassTot-trans-ton= -53.4(chiller)kW= 38 Chicago 90.1-2010 Roofsky lite ton = 0.0 GlassN-solar-ton = 0.0(chiller)lift= 11.7 Large Office Peopleton = 0 kW GlassS-solar-ton = 0.0(chiller)%= 14% 50F/45F 60F supply 4AM plugton = 41 146 GlassE-solar ton = 0.0(chiller)#= 1 Weather %clear sky = 100% Lightton= 6 22 GlassW-solar ton = 0.0 GlassTot-solar-ton = 0.0
(CHILLER)kW= 38 conditions Tdry bulb = 50.0 (int-cfm)to-per-ret= 23993 BLD kW= 168.0 (int cfm)per-ton = 15.12 >(chiller)kW/ton= 0.440 Twet bulb = 45.0 Total Bldint-ton = 43.2 AHU kW= 434.9 Tot Bldper-sen-ton = -67.0 vPlant kW = 74.6 Tstat-int= 80.0 SITE kW = 602.9 Tstat-per = 73.0 return
(Bld)int.air-ton= -43.2 ^ 60F supply 4AM ^ (Bld)per.air-ton= 67.0 airTair supply int= 60.00 ASHRAE Design Tair supply per= 94.00
^ ABS Bld Ton = 110.16 ^ > Evaporator Ton kW Ton kW V
(evap)ton= 85.8 (fan)int-ter= 0.0 0.0 (fan)per-ter= 0.0 0.0TER= 43.4 Theat-air= 94.0
TER-app= 1.05 (D)heat = 67.0 235.5 ^ EVAPton= 86 Treheat air = 80.0
(H)evap= 51.9 (D)reheat = 41.5 145.8(evap)ft/sec= 10.44 381.4
(evap)des-ft/sec= 10.44 (D)int-air-ton= -43.2 Interior (D)per-air-ton= -63.8 Peri ^ V Tair coils = 60.00 duct Tair coils= 60.00 duct
(bEQ)day gpmevap= 600 Psec-heat-ton = -0.90 (D)int-CFM= 23,993 ^ (D)per-CFM= 35,435 ^(lwt)evap = 44.40 > Psec-kW= 4.5 > (ewt)coil= 44.4 >>>(Coil)sen-ton= 83 ^ (coil)gpm= 4.0 ^
(H)pri-total= 63.1 v Efdes-sec-p = 0.80 (coil)cap-ton= 8.4 UAdesign= 2.66 ^ (H)pri-pipe= 2.5 Tbp= 44.40 Efsec-pump = 0.30 (coil)H2O-ft/sec= 0.11 COIL UA= 0.63
(H)pri-fitings= 7.0 gpmbp= -497 (H)sec= 70.0 PLANTton = 83 (coil)des-ft/sec= 1.20 (one coil)ton= 3.21(Ef)c-pump= 0.81 (H)pri-bp= 1.72 (H)sec-pipe= 1 LMTD= 13.27 (H)coil= 0.0 VPc-heat-ton= -0.48 v (H)sec-bp= 0.00 Pipesize-in = 8.0 (COIL)L+s-ton= 83 ^ ^ ^ (H)coil-des= 2.1
^ < pc-kW= 8.8 (ewt)evap = 47.83 < (gpm)sec= 103 < (lwt)coil= 64.4 <<<< Tair VAV= 75.58 TBLD-AR = 73.00Pchiller-# = 1 (FAN)VAV-CFM= 59,428 (Air)ret-CFM = 66,239 Return
Chicago 4AM All Electric Fuel Heat (FAN)ton-VAV= 11.7 (FAN)ret-kW= 12 FanPerformance 4AM 60F supply kW THERM (FAN)kW-VAV= 41 (FAN)ret-ton= 3.5 V
chillerkW/evapton= 0.440 BLD.kW= 168.0 ^ (Air)ret-ton = 81.0plantkW/site ton= 0.895 (Fan)kW = 53.6 26 F.A.Inlet ^ Tar-to-VAV = 73.59
CCWSkW/bld ton= 4.62 Ductheat= 381.4 16.27 statFA= 42 26 VAV FANS VAVret-ton = 72.1WeatherEin-ton = -79.2 (FA)heat= 0.0 0.00 TFA to VAV = 50.0 > Tret+FA = 73.39 InfilVAV-Lat-ton = 0.00(Site)kW-Ein-ton = 171.5 Heat total = 381.4 16.27 Tdry bulb = 50.0 >(FA)sen-ton = > -0.4 (dh) = 2.600 < VAVret-CFM = 58,930 <PlantkW-Ein-ton = 21.2 PlantkW= 74.6 Fresh air > >>> > (FA)CFM= 499 > Efan-VSD= 0.441 InfilCFM-ton = 8.3 V
Total Ein-ton = 113 SystkW = 677.5 296.1 Twet bulb = 45.0 > (FA)Lat-ton= 0.0Pumptot-heat-ton = -2.1 (FA)kW= 0.0 ExLat-ton = 0.0
AHU ExLat-ton = 0.0 BLD.kW= 168.0 SEE SCHEMATIC ExCFM = -7,309AHU Exsen-ton = -8.9 CCWSkW = 509.5 ton blue water temp pink TEx = 73.59Tower Tton-Ex = -102 SystkW = 677.5 air cfm purplewater gpm orange Exsen-ton = -8.9 V Total Eout-ton = -113 air temp green kW red
FIGURE 2-20: 4AM (SEE) Schematic at 50F DB-45F WB-(60F supply air)
Kirby Nelson PE Page 21
CONCLUSION FOR CONDITIONS DEFINEDConsidering that a water economizer only offers a maximum opportunity of 5% to 8% if all chiller kW is eliminated by an economizer and for this case only about 2.5% to 4% as illustrated by Figure 2-16; the author arrives at the conclusion; the cost, complexity, and control of a water economizer for the Chicago large office as defined by the Pacific Northwest National Laboratory (PNNL) study of 90.1-2010 is not a good idea; and raising air supply temperature to 60F from 55F is a bad ideal for the conditions studied here. Other changes that will make a difference for this building as defined include;(1) Solar load(2) Interior and perimeter stat set points.(3) Return air path(4) Outside temperatures below 50F DB & 45F WB.We plan to address these issues in coming chapters.
One final note; the above analysis is for the building system as designed according to “ASHRAE” concepts. These (http://kirbynelsonpe.com) studies include a (minimum kW design) that would likely result in different results and conclusions for the issues raised here. Kirby Nelson P.E.Life Member ASHRAE
Kirby Nelson PE Page 22
System Nomenclature Each of the more than 100 components of the system will be defined.The (PNNL) study defines the large office building as given by Figure N-1, a 13 story office with 498,600 square feet of air conditioned space.
FIGURE N-1: Building description The (PNNL) study can be viewed at;http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010
BLD ft2 = %clear sky = InfilLat-ton =
# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =
N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=
Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =
Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =
Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =
Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =
(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v
Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air
BUILDING NOMENCLATURE:Building structure;
BLD ft2 = air conditioned space# Floors = number of building floorsRoof ft2 = roof square feetN/S wall ft2 =north/south wall square feetE/W wall ft2 =east/west wall square feetWall % glass = percent of each wall that is glassGlass U = glass heat transfer coefficientWall U = wall heat transfer coefficientGlass SHGC = glass solar heat gain coefficientWall emit = wall solar indexBuilding interior space;Rooftrans-ton =transmission through roof (ton)Roofsky-lite-ton =sky lite load (ton)Peopleton = cooling load due to people (ton)Plugton = cooling load due to plug kWPlugtkW = kW demand due to plug loadsLightton = cooling load due to lights (ton)LightkW = kW demand due to lights(int-cfm)to-per-return = CFM of interior supply air that returns to perimeter of buildingTotal Bldint-ton = total building interior load (ton)Tstat-int = interior stat set temperature (F)Bldint-air-ton = supply air ton to offset interior loadBuilding perimeter space;%clear sky = percent solar that hits buildingTdry bulb = outside dry bulb temperature (F)Twet bulb = outside wet bulb temperature (F)Infillat-ton = latent load due to air infiltration (ton)InfilCFM = air infiltration CFMInfilsen-ton = sensible load due to air infiltration (ton)Walln trans ton = north wall transmission (ton)Walls trans ton = south wall transmission (ton)WallE trans ton = east wall transmission (ton)Wallw trans ton = west wall transmission (ton)Walltot-trans-ton = total wall transmission (ton)GlassN-trans-ton = north wall glass transmission (ton)GlassS-trans-ton = south wall glass transmission (ton)GlassE-trans-ton = east wall glass transmission (ton)GlassW trans-ton = west wall glass transmission (ton)Glasstot-trans-ton = total transmission thru glass (ton) GlassN-solar-ton = north glass solar load (ton)GlassS-solar-ton = south glass solar load (ton)GlassE-solar-ton = east glass solar load (ton)GlassW-solar-ton = west glass solar load (ton)Glasstot-solar-ton = total glass solar load (ton)(int cfm)per-ton = effect of interior CFM to wall (ton)
Kirby Nelson PE Page 23
Total Bldper-sen-ton total perimeter sensible load (ton)Tstat-per = perimeter stat set temperature (F)Bldper-air-ton = supply air ton to offset perimeter load
Tair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
FIGURE 2A Air handler system AIR HANDLER DUCT SYSTEM NOMENCLATURE
(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^
Duct system nomenclatureTair supply int = temperature air supply to interior (F)(fan)int-ter-kW = kW demand of interior terminal fans(fan)int-ter-ton = load due to interior terminal fans kW (D)int-air-ton = cooling (ton) to interior ductTair coils = supply air temperature off coils to duct(D)int-CFM = supply air CFM to interior duct
(ABS Bld Ton) = absolute building load on (CCWS)Tair supply per = temperature air supply perimeter (F)(fan)per-ter-kW = kW demand perimeter terminal fans(fan)per-ter-ton = load due to perimeter terminal fansTheat-air = temp supply air before terminal fan heat(D)heat-kW = kW heat to perimeter supply air(D)heat-ton = (ton) heat to perimeter supply airTreheat air = temp(F) perimeter supply air after reheat (D)reheat-kW = kW reheat to perimeter supply air(D)reheat-ton = (ton) reheat to perimeter supply air(D)per-air-ton = cooling (ton) to perimeter duct Tair coils = supply air temperature off coils to duct(D)per-CFM = supply air CFM to perimeter ductCOIL NOMENCLATURE(coil)sen-ton = sensible load on all coils (ton)(coil)cap-ton = LMTD * UA = capacity (ton) one coil(coil)H2O-ft/sec = water velocity thru coil (ft/sec)(coil)design-ft/sec = coil design water velocity (ft/sec)LMTD = coil log mean temperature difference (F)(coil)L+s-ton = latent + sensible load on all coils (ton)(coil)gpm = water flow (gpm) thru one coilUAdesign = coil UA design valueUA = coil heat transfer coefficient * coil area. UA varies as a function water velocity (coil)gpm thru the coil, therefore as the (coil)gpm decreases the coil capacity decreases.
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR = Coils(one coil)ton = load (ton) on one coil(H)coil = air pressure drop thru coil (ft)(H)coil-design = design air pressure drop (ft)
(COIL)L+s-ton= ^ ^ ^ (H)coil-des=<<<< Tair VAV= TBLD-AR =
(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
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VAV FAN SYSTEM NOMENCLATUREFresh air nomenclature:statFA = fresh air freeze stat set temperature (F)TFA to VAV = temperature of fresh air to VAV fan(FA)sen-ton = fresh air sensible load (ton)(FA)CFM = CFM fresh air to VAV fan inlet(FA)Lat-ton = fresh air latent load (ton)(FA)kW = heat kW to statFA set temperatureAir return nomenclature: TBLD-AR = return air temp (F) before return fan(Air)ret-CFM = CFM air return from building(FAN)ret-kW = return fans total kW(FAN)ret-ton = cooling load (ton) due to (FAN)ret-kW
(Air)ret-ton = return air (ton) before return fansTAR to VAV = TBLD-AR + delta T due to return fans kWVAVret-ton = return (ton) to VAV fans inletInfilVAV-Lat-ton = infiltration latent (ton) to VAV fansVAVret-CFM = return CFM to VAV fans inletInfilCFM-ton = load (ton) due to infiltration CFMExhaust air nomenclatureExLat-ton = latent load (ton) exhaustedExCFM = CFM of exhaust airTEx = temperature of exhaust air Exsen-ton = sensible load (ton) exhaustedVAV Fans nomenclatureTair-VAV = temp. air to coils after VAV fan heat(FAN)VAV-CFM = CFM air thru coils(FAN)ton-VAV = load (ton) due to VAV fan kW(FAN)kW-VAV = total VAV fan kW demandTret+FA = return and fresh air mix temperature (F)(dh) = VAV air static pressure (ft)Efan-VSD = VAV fans efficiency
AIR SIDE SYSTEM PLUS BUILDING BLD ft2 = %clear sky = InfilLat-ton =
# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =
N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=
Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =
Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =
Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =
Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =
(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v
Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air
Tair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
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Condenser(cond)ton= Pipesize-in = (H)T-pipe= Tower
TCR= > gpmT= > (ewt)T= tfan-kW=TCR-app= (H)T-total= (H)T-static = Tfan-kW=
(COND)ton= PT-heat = Trange= tfan-%=(H)cond= < pT-kW= < (lwt)T = tton-ex=
(cond)ft/sec= EfTpump= Tapproach = T#=Ptower # = T-Ton-ex=
Trg+app =Compressor ASHRAE Design
(chiller)kW= Chicago 90.1-2010(chiller)lift= Large Office(chiller)%= Peak day Design 4PM(chiller)#= Weather %clear sky =
(CHILLER)kW= conditions Tdry bulb =(chiller)kW/ton= Twet bulb =Plant kW =
> Evaporator(evap)ton=
TER=TER-app=
^ EVAPton=(H)evap=
(evap)ft/sec=(evap)des-ft/sec=
^ Vgpmevap= Psec-heat-ton =
(lwt)evap = > Psec-kW= > (ewt)coil=(H)pri-total= v Efdes-sec-p =
^ (H)pri-pipe= Tbp= Efsec-pump =(H)pri-fitings= gpmbp= (H)sec= PLANTton =(Ef)c-pump= (H)pri-bp= (H)sec-pipe=Pc-heat-ton= v (H)sec-bp= Pipesize-in =
^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil=Pchiller-# =
CENTRAL PLANT Nomenclature will be defined by addressing each component of the plant.Primary/secondary pumping nomenclaturegpmevap = total gpm flow thru evaporators(H)pri-total = total primary pump head (ft) = (H)pri-pipe + (H)pri-fittings + (H)pri-bp + (H)evap
(H)pri-pipe = primary pump head due to piping (ft)(H)pri-fittings = primary head due to pump & fitting (ft)(Ef)c-pump = efficiency of chiller pumpPc-heat-ton = chiller pump heat to atmosphere (ton)Pc-kW = one chiller pump kW demand (kW)Pchiller-# = number chiller pumps operating(lwt)evap = temperature water leaving evaporator (F)Tbp = temperature of water in bypass (F)gpmbp = gpm water flow in bypass(H)pri-bp = head if chiller pump flow in bypass (ft)(ewt)evap = temp water entering evaporator (F)
Psec-heat-ton = secondary pump energy not into system (ton), goes to atmospherePsec-kW = kW demand of secondary pumpsEfdes-sec-p = design efficiency of secondary pumpingEfsec-pump = efficiency of secondary pumping(H)sec = secondary pump head (ft) = (H)sec-pipe + (H)sec-
bp + (H)coil + (H)valve
(H)sec-pipe = secondary pump head due to pipe (ft)(H)sec-bp = head in bypass if gpmsec > gpmevap
gpmsec = water gpm flow in secondary loop(ewt)coil = water temperature entering coil (F)Plantton = load (ton) from air side to plantPipesize-in = secondary pipe size (inches)(lwt)coil = temperature of water leaving coil (F)Condenser nomenclature:(cond)ton = load (ton) on one condenserTCR = temperature of condenser refrigerant (F)TCR-app = refrigerant approach temperature (F)(COND)ton = total load (ton) on all condensers(H)cond = tower pump head thru condenser (ft)(cond)ft/sec = tower water flow thru condenser Compressor:(chiller)kW = each chiller kW demand(chiller)lift = (TCR – TER) = chiller lift (F)(chiller)% = percent chiller motor is loaded(chiller)# = number chillers operating(CHILLER)kW = total plant chiller kW(chiller)kW/ton = chiller kW per evaporator tonEvaporator(evap)ton = load (ton) on one evaporatorTER = evaporator refrigerant temp (F)TER-app = evaporator refrigerant approach (F)EVAPton = total evaporator loads (ton)(H)evap = pump head thru evaporator (ft)(evap)ft/sec = velocity water flow thru evaporator(evap)des-ft/sec = evaporator design flow velocityTower piping nomenclaturePipesize-in = tower pipe size (inches)gpmT = each tower water flow (gpm)(H)T-total = total tower pump head (ft)PT-heat = pump heat to atmosphere (ton)PT-kW = each tower pump kW demandEfT-pump = tower pump efficiencyPtower # = number of tower pumps(H)T-pipe = total tower pump head (ft)
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Kirby Nelson PE Page 27
Tower piping nomenclature cont.(ewt)T = tower entering water temperature (F)(H)T-static = tower height static head (ft)Trange = tower range (F)= (ewt)T – (lwt)T
(lwt)T = tower leaving water temperature (F)Tapproach = (lwt)T – (Twet-bulb)Tower nomenclature
tfan-kW = kW demand of one tower fanTfan-kW = tower fan kW of fans on
tfan-% = percent tower fan speedtton-ex = ton exhaust by one tower
T# = number of towers onTton-ex = ton exhaust by all towers onTrg+app = tower range + approach (F)SYSTEM PERFORMANCE The performance indices of the following Tables are self-explanatory. A complete schematic will be shown below.
Chicago 4PM All ElectricFuel HeatPerformance 4PM Design kW THERM
chillerkW/evapton= BLD.kW=(plant)kW/site ton= (Fan)kW =CCWSkW/bld ton= Ductheat=WeatherEin-ton = (FA)heat=(Site)kW-Ein-ton = Heat total =PlantkW-Ein-ton = PlantkW=
Total Ein-ton = SystkW =Pumptot-heat-ton =
AHU ExLat-ton = BLD.kW=AHU Exsen-ton = CCWSkW =Tower Tton-Ex = SystkW =Total Eout-ton =
Performance table at given hour
BLD sq-ft =ALL ELECTRIC Peak day
Design 24hr BLD.24hr-kW=
(Fan)24hr-kW =(Duct)24hr-heat kW=
(FA)24hr-heat kW=Heat24hr-total kW=
Plant24hr-kW=SYST 24hr-kW =
(CCWS)24hr-kW=BLD.24hr-kW=
Total24hr-kW =
24 Hour performance, all-electric
ASHRAE DesignBLD sq ft =
Fuel heat Peak dayDesign 24hr ThermBLD.24hr-kW=
(Fan)24hr-kW =(Duct)24hr-heat therm=
(FA)24hr-heat therm=Heat24hr-total therm=
Plant24hr-kW=SYST 24hr-kW =
24 Hour performance, heat with fuel
Weather24h-Ein-ton= SITE24h-kW-Ein-ton = Plant24h-kW-Ein-ton =Total24h-Ein-ton =Pump24hr-heat-ton =
AHU Ex24hr-Lat-ton =AHU Ex24hr-sen-ton =
Tower24hr-ton-Ex =Total E24hr-out-ton =
ASHRAE Design
24 Hour Energy in = Energy out
ASHRAE Design kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
=(Fan)24hr-W/sq ft- =Plant24hr-W/sq ft-=
(Heat)24hr-W/sq ft-=Syst Total24hr-W/sq ft-=
90 day (bEQ)=FUEL HEAT SYSTEM (bEQ)day
Bld,Fan,Plant24hr-W/sq ft-= 49.70Heat24hr-btu/sq ft= 0.00
Syst Total24hr-=90 day (bEQ)=
(bEQ) estimate
Next the full system energy equilibrium (SEE) schematic.
Kirby Nelson PE Page 28
BLD ft2 = %clear sky = InfilLat-ton =
Condenser # floors = Tdry-bulb = Infil-CFM = <(cond)ton= Pipesize-in = (H)T-pipe= Tower Roof ft2 = Twet-bulb= Infilsen-ton =
TCR= > gpmT= > (ewt)T= tfan-kW= N/S wall ft2 = WallNtrans ton=TCR-app= (H)T-total= (H)T-static = Tfan-kW= E/W wall ft2 = WallStrans ton=
(COND)ton= PT-heat = Trange= tfan-%= Wall % glass= WallEtrans ton=(H)cond= < pT-kW= < (lwt)T = tton-ex= Glass U = WallWtranston= WallTot trans ton =
(cond)ft/sec= EfTpump= Tapproach = T#= Wall U = GlassN trans ton =Ptower # = T-Ton-ex= Glass SHGC = GlassS trans ton =
Trg+app = Wall emitt = GlassE-trans ton =Compressor ASHRAE Design RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=
(chiller)kW= Chicago 90.1-2010 Roofsky lite ton = GlassN-solar-ton =(chiller)lift= Large Office Peopleton = kW GlassS-solar-ton =(chiller)%= Peak day Design 4PM plugton = GlassE-solar ton =(chiller)#= Weather %clear sky = Lightton= GlassW-solar ton = GlassTot-solar-ton =
(CHILLER)kW= conditions Tdry bulb = (int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >(chiller)kW/ton= Twet bulb = Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = vPlant kW = Tstat-int= SITE kW = Tstat-per = return
(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^ > Evaporator Ton kW Ton kW V
(evap)ton= (fan)int-ter= (fan)per-ter=TER= Theat-air=
TER-app= (D)heat = ^ EVAPton= Treheat air =
(H)evap= (D)reheat =
(evap)ft/sec=(evap)des-ft/sec= (D)int-air-ton= Interior (D)per-air-ton= Peri
^ V Tair coils = duct Tair coils= ductgpmevap= Psec-heat-ton = (D)int-CFM= ^ (D)per-CFM= ^
(lwt)evap = > Psec-kW= > (ewt)coil= >>>(Coil)sen-ton= ^ (coil)gpm= ^(H)pri-total= v Efdes-sec-p = (coil)cap-ton= UAdesign=
^ (H)pri-pipe= Tbp= Efsec-pump = (coil)H2O-ft/sec= COIL UA=(H)pri-fitings= gpmbp= (H)sec= PLANTton = (coil)des-ft/sec= (one coil)ton=(Ef)c-pump= (H)pri-bp= (H)sec-pipe= LMTD= (H)coil= VPc-heat-ton= v (H)sec-bp= Pipesize-in = (COIL)L+s-ton= ^ ^ ^ (H)coil-des=
^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil= <<<< Tair VAV= TBLD-AR =Pchiller-# = (FAN)VAV-CFM= (Air)ret-CFM = Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= (FAN)ret-kW= FanPerformance 4PM Design kW THERM (FAN)kW-VAV= (FAN)ret-ton= V
chillerkW/evapton= BLD.kW= ^ (Air)ret-ton =(plant)kW/site ton= (Fan)kW = 26 F.A.Inlet ^ Tar-to-VAV =CCWSkW/bld ton= Ductheat= statFA= 26 VAV FANS VAVret-ton = WeatherEin-ton = (FA)heat= TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =(Site)kW-Ein-ton = Heat total = Tdry bulb = >(FA)sen-ton = > (dh) = < VAVret-CFM = <PlantkW-Ein-ton = PlantkW= Fresh air > >>> > (FA)CFM= > Efan-VSD= InfilCFM-ton = V
Total Ein-ton = SystkW = Twet bulb = > (FA)Lat-ton=Pumptot-heat-ton = (FA)kW= ExLat-ton =
AHU ExLat-ton = BLD.kW= SEE SCHEMATIC ExCFM =AHU Exsen-ton = CCWSkW = ton blue water temp pink TEx =Tower Tton-Ex = SystkW = air cfm purplewater gpm orange Exsen-ton = V Total Eout-ton = air temp green kW red
System Energy Equilibrium (SEE) Schematic
Kirby Nelson PE Page 29
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