joshua rogers final project
TRANSCRIPT
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Mechanical Cooling Design
for The New Orleans Home
B
Joshua Roge
Building Systems ARCH 5
Spring 20
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Table of Contents
HVAC Design and Theory
Project Overview
Designing the HVAC System
HVAC System Layout
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4-5
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HVAC Design and Theory
An HVAC system provides cool air to a buildings occupant during even the hottest
summer days. An HVAC system is often overlooked when it is working, but when it fails
everyone realizes it. After all other steps of passive cooling have been exhausted onlythen should an HVAC system be applied to any building.
There are several key design issues which must be accounted for during the design
process of an HVAC system. First, the system needs to distribute air eciently, quietly,
and gently across a room. It should distribute air around the room, the walls, and
ceilings so it provides an environment of cold air throughout the building. It is
important to recognize that a system cannot deliver air across a distance of greater than
twenty feet, so the supplys for cold air need to be placed accordingly. Duct work can
cause great ineciencies in the system, so it should always be designed to deliver airwith as little friction and interruption as possible. The system should be quiet and the air
quality high. Finally, the system needs to be easy to install and maintain for long periods
of time.
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Project Overview
The New Orleans Home is a small, two-bedroom residence located in New Orleans,
Louisiana. The home is located in an area devastated by ooding during Hurricane
Katrina, and therefore has all the living spaces seven feet above the ground. NewOrleans is a very hot and humid climate located along the Gulf of Mexico, so having a
cool home during the summer is priority for residents of New Orleans.
The home is 866 square feet, and is designed to be LEED Platinum. The walls and ceiling
have a R-Value of 30, and the house has very few windows facing East and West which
are not shaded. The building is designed to have a very high indoor air quality, so the air
leakage from inside to outside is minimal.
Even with the high levels of insulation and care in designing the building envelope, thebuilding will still require an HVAC unit. The average temperatures in New Orleans in July,
is 95 degrees with 68% relative humidity. Living in New Orleans without air conditioning
during the summer months is a very uncomfortable experience.
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Designing the HVAC System
1. Estimate Heat Gain Using Table F3 from Mechanical and Electrical Equipment for Buildings
A. People and Equipment
Heat gain from people: 230 BTU/H per person = 230*3 = 690 BTU/H
Heat gain from appliances: 1200 BTU/H per residence
B. Electrical Lighting
Heat gain from interior lighting: 2.7 BTU/H
C. Heat Gain through Building Envelope
Heat gain through windows: Total window area/total oor area = 99 SF/866 SF = 2.4 BTU/SF
Heat gain through walls: (Total Wall area/total oor area)*U-value of wall*25=
(1871 SF/866 SF)*.065*.25 = 3.5 BTU/SF
Heat gain through roof: (Total roof area/total oor area)*U-value of Roof*45=
(1290 SF/866 SF)*0.34*45 = 2.2 BTU/SF
D. Inltration
Heat gain from inltration in windows and walls:
{(Total window area + Total wall area)/Total oor area}*1.9 =
{(99 SF+1871 SF)/866 SF)*1.9 = 4.32 BTU/SF
E. Ventilation
Heat Gain from air ventilation:
(Total CFM of outdoor air/Total oor area)*27 =
(45 CFM/866 SF)*27 = 1.4 BTU/SF
Add B, C, D, E together = 2.7+2.4+3.5+2.2+4.32+1.4 = 16.52 Total Heat Gain per SF
Total Transmission = 16.52 BTU/SF * 866 SF = 14,306 BTU/H
Room Sensible Heat = People + Equipment + Total Transmission
= 690 BTU/H+1200 BTU/H+14,306 BTU/H = 16,196 BTU/H
2. Calculate quantity of air required to cool the room
A. Calculate Cubic feet per minute: Room sensible heat/1.1*Change in temperature =
16,196 BTU/H/1.1*(75-20) = 736 CFM
B. Calculate portion which is outdoor air: 3 People * 45 CFM = 135 CFM
135 CFM/736 CFM = 18% Outdoor Air
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B A 18%
OUTD
OOR
AIR
82%
INDOOR
AIRC
D
3. Calculate Grand Total Heat
A. GTH = 4.5 * cfm * (Hc-Hb) = 4.5 * 736 * (34-23) = 36,432 BTU
The size of required refrigeration unit is specied in tons where 1 ton = 12,000 BTU/H
The refrigeration required: 36,432 BTU/H/12,000 BTU/H ton = 3.036 Tons
A 3 Ton unit will be sucient
4. Calculate Duct Size
B. Table 9.4 in MEEB: 3 ton system will supply 1600 CFM
(1600CFM * 144(in/ft))/1700 CFM = 135 in so choose a 10*14 duct
Point A - Bulls eye Temperature @ 75 degrees & 50% RH
Point B - Desired condition of the chilled air @ 55 degrees,
Enthalpy is 23 BTU/H
Point C - Mixture of indoor and outdoor air,
Enthalpy is 34 BTU/H
Point D -Temperature outside @ 95 degrees and 68% RH
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HVAC System Layout
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