chapter 9 ref and air condition
DESCRIPTION
حساب الأحمال الحراريةTRANSCRIPT
-
Heat Loads Calculation
21
21
.ASHRAE
)sAir Conditioning Load(
.
)sSummer Air Conditioning Load(
24 2 = CT oR
5 % 50 =R.
-
) GainsExternal Heat(
.
)Heat Transmission Through Walls(
)- (
:
Fig. 9-1 Heat transmission through walls
oi hk
x
k
x
k
x
hU
111
3
3
2
2
1
1 +
+
+
+= (9-1)
# "! k x
io hh , % &! U*1 0 - # "& + *(& )
: TQ - # "&
TUAQTrans = (9-2)
T A
.
-
)4.29()5.25().( +++= oR TTKLMCLTDT (9-3)
2 CLTD Cooling load temperature difference
Co 5.25 Co 4.29 Co 6.11
o 40
CLTD ) -( 21
.
LM
o 40 o 24 ) - (
.
K 1 =K 85.0 =K
. K=65.0
RT oT
:
cmmo PTTT = (9-4)
Tm Pc
,min,max ooC TTP CP=11~14 =
Tm
).- (
:
[ ] FTTKLMCLTDT oR +++= )4.29()5.25().( (9-5)
-
F )-( CLTD
F=75.0
K=1 K
.K=5.0
)dowsTransmission through Win(
wQ
oi A x hh ,
:
io hk
x
hU
111 ++= (9-6)
)( max CLFSHGFSCTUAQW += (9-7)
)4.29()5.25( ++= oR TTCLTDT (9-8)
U 1.25
.ASHRAE
CLTD ).-(
Sc Shading coefficient
mm 3
) -(
.
maxSHGF Solar Heat Gain Factor Maximum
mm 3
)-( )-( )-(
o 24 o 23 .
CLF
M L
-
CLF ) -( H
.
)Infiltration and Ventilation Loads(
.
)ateRiltration Inf(
Tight
) -( )- ( Loose Medium
)- (
Va )/( sm
Ro TT . ,
)( Va RoA TTcbaN ++= (9-9)
abc : &infm )-( , ,
= VNm Ainf& (9-10)
. AN V ,
) ateRVentilation(
: &venm )-(
= VNm Pven && (9-10)
&V PN
.
LeakQ Leakage Load,
-
LeakSQ ,
LeakLQ . ,
)()( inf, RoPvenLeakS TTCmmQ a += && (9-11)
fgRovenLeakL hmmQ += )()( inf, && (9-12)
LeakLLeakSLeak QQQ ,, += (9-13)
aP
C fgh
.
) GainsInternal Heat(
.
)Lighting Load(
10~20 /2 mWLR =
.
CLFLFFQ RbuLight = (9-14)
Utilization factor uF
. 1
bF 1.2 1
1.37
.
CLF
Convective heat
CLF
-
ASHRAE
hr 16~5 8.0~98.0=CLF.
)Appliances Load(
AppQ
= )1( PowerQApp (9-15)
.
)Loadcy Occupan(
PerQ
PerSQ PerLQ , ,
.
CLFHNQ SPPerS =, (9-16)
LPPerL HNQ =, (9-17)
LH SH PN
) - (
. % 75 % 85
CLF
CLF=6.0 ~ 0.97
.
)System Load(
-
Safety factor
% 20~5=SF.
)Total Heat Load(
.LQ SQ TotalQ
=i
iSS QQ1
, , =i
iLL QQ1
,
LSTotal QQQ += (9-18)
) Heat FactorRoom Sensible(
Fig. 9-2 Room sensible heat factor, RSHF in Summer
15
40 , & 60 % == oo
o CT
RS ) -(
.
LS
S
Total
S
QQ
Q
Q
QRSHF
+== (9-19)
-
24 2 R = CT oR 50 %5 =R
CTT S oRS )10~5(=
RS S=85~95% .
)Winter Air Conditioning Load(
10 , & 90 % == oo
o CT
S )- (
CTT oRS )10~5(+= .
SQ)(
. R
:
LQ)( .
RS R .
LQ+)( .
RS R \ .
-
Fig. 9-3 Room sensible heat factor, RSHF in Winter
LQ+)(
R
LQ)(
R
.
Example 9-1
The room shown below is theater, calculate the total cooling load TQ and room
sensible heat factor, RSHF , if the number of persons are 500. The room is at
latitude of N 30 o , 21 of July, and solar time of hr 15 . The room is maintained at
dbt 24 Co and RH % 50 , the ambient conditions are dbt 38 Co and wbt 25 Co . The
ceiling is from heavy concrete of cm 20 , cm 5 ceramic slab and cm 3 cement layer
from inside. The walls are from common bricks of cm 20 and cm 3 cement layer
from inside and outside. The floor is from concrete of cm 10 over unconditioned
space, cm 5 ceramic slab and cm 3 cement layer from outside. The inside and
outside convective heat transfer coefficient is KmWhi ./ 92= and KmWho ./ 22
2= .
The light intensity is 2/ 15 mW of floor area and fluorescent. The appliances load is
-
kW 10 . The air density is 3/ 18.1 mkg and specific heat of KkgkJ ./ 1005 . The water
evaporation heat is kgkJ / 2570 .
Data: 500 wbt, 25 ,dbt 38 ,% 50 ,dbt 24 oo ===== PooRo
R NCtCtRHCt N 30 o , 21 July, Solar time hr 15 , KmWhi ./ 9
2= , KmWho ./ 222=
Light of 2/ 15 mW , 3/ 18.1 mkga = , KkgkJC aP ./ 1005= , kgkJh fg / 2570= Required: RSHFQT ,
Solution Data from ASHRAE tables for Daily range, M and walls density Medium.
Latitude N 30 o E W S N Ceiling Glass Light Persons CCLTD o 13 8 8 5 18 8
LM -0.4 -0.4 -2.0 0.5 0.5 0 K 0.85 1 F 1 Sc 0.64 Glass windows and doors
2max / mWSHGF 678 678 207 128 866
CLF 0.20 0.53 0.50 0.82 0.92 0.97 Data of construction materials properties Material
Thermal conductivity
KmW ./
Material
Thermal conductivity
KmW ./ Asphalt 0.75 Ceramic 0.67 Common Bricks 0.73 Glass 1.4 Face Bricks 1.32 Polystyrene 0.035 Hall Bricks 0.813 Corkboard 0.043 Concrete 1.1 Foam glass 0.044 Cement layer 0.72 Wood 0.116
-
Heat transmission through walls
oi hk
x
k
x
k
x
hU
111
3
3
2
2
1
1 +
+
+
+=
22
1
72.0
03.0
73.0
2.0
72.0
03.0
9
11 ++++=U
KmWU ./ 946.1 2=
)4.29()5.25().( +++= oR TTKLMCLTDT
CTNo 76.14)4.2938()245.25(85.0)5.05( =+++=
CTEo 81.20)4.2938()245.25(85.0)4.013( =++=
CTWo 56.16)4.2938()245.25(85.0)4.08( =++=
CTSo 2.15)4.2938()245.25(85.0)0.28( =++=
WTUAQ NNN 941.1068476.14)361330(946.1 ===
WTUAQ EEE 423.1978281.20)5.133361340(946.1 ===
WTUAQ WWW 33.1617756.16)5.1341340(946.1 ===
WTUAQ SSS 569.111362.15)5.1331330(946.1 ===
WQWalls 263.57781569.1113633.16177423.19782941.10684 =+++=
Heat transmission through ceiling
oi hk
x
k
x
k
x
hU
111
3
3
2
2
1
1 +
+
+
+=
22
1
67.0
05.0
1.1
2.0
72.0
03.0
9
11 ++++=U
KmWU ./ 199.2 2=
FTTKLMCLTDT oRC +++= )]4.29()5.25().[(
CTCo 6.281)]4.2938()245.25(1)5.018[( =+++=
WTUAQ CCCeiling 094.754826.28)3040(199.2 ===
Heat transmission through floor
oi hk
x
k
x
k
x
hU
111
3
3
2
2
1
1 +
+
+
+=
22
1
72.0
03.0
1.1
1.0
67.0
05.0
9
11 ++++=U
-
KmWU ./ 749.2 2=
CTTT RoFo 142438)( ===
WTUAQ FFFloor 2.4618314)3040(749.2 ===
Heat transmission through doors
Assume the doors from wood with 4 cm thickness.
oi hk
x
hU
111 ++=
22
1
116.0
04.0
9
11 ++=U
KmWU ./ 994.1 2=
WTUAQ NDNDN 766.52976.14)36(994.1 ===
WTUAQ EDEDE 913.74681.20)36(994.1 ===
WQDoors 679.1276913.746766.529 =+=
Transmission Load
WQTrans 236.180723679.12762.46183094.75482263.57781 =+++=
Solar heat gains through glass windows
Assume clear glass of 3 mm thickness and Venetian medium shading.
oi hk
x
hU
111 +
+=
22
1
4.1
003.0
9
11 ++=U
KmWU ./ 301.6 2=
)4.29()5.25( ++= oRG TTCLTDT
CTGo 1.18)4.2938()245.25(8 =++=
)( max CLFSHFGScTUAQ GGG +=
WQGE 609.4468)5.067864.01.18301.6)(5.133( =+=
WQGW 525.8457)82.067864.01.18301.6)(5.134( =+=
WQGS 544.2487)53.020764.01.18301.6)(5.133( =+=
WQGlass 678.15413544.2487525.8457609.4468 =++=
-
Ventilation and Infiltration
Room volume, 3 15600133040 mV == , and tight room
From table (9-11), 36.0=AN air change rate,
skgVNm A / 841.118.1156003600
36.0inf === &
From tables (9-14), (9-15), smoking persons and seated rest, ventilation is,
skgVNm Pven / 425.418.110)5.7500(3 === &&
)()( inf, RoPvenLeakS TTCmmQ a += &&
WQ LeakS 62.88162)2438(1005)425.4841.1(, =+=
fgRovenLeakL hmmQ += )()( inf, &&
WQ LeakL 824.8373810257010)5.97.14()425.4841.1(33
, =+=
Lighting Load
RbuLight LCLFFFQ =
WQLight 19872)4030(1592.02.11 ==
Appliances Load
WPowerQApp 10000==
Persons Load
WHCLFNQ SPPerS 363757597.0500, ===
WHNQ LPPerL 2000040500, ===
Sensible, Latent and Total Load
=i
iSS QQ1
,
kWWQ
Q
S
S
547.350 534.350546
36375100001987262.88162678.15413236.180723
==+++++=
kWWQQi
iLL 739.103 824.10373820000824.837381
, ==+==
kWQTotal 286.454739.103547.350 =+=
Room sensible heat factor
-
% 2.777716.0286.454
547.350 ===Total
S
Q
QRSHF
Ct oS 14=.
From Psychrometric chart, the air properties are,
kgmkgkJhkgkJh ooR / 9023.0 v,/ 4.76 ,/ 1.483===
Process SR is parallel to RSHF = 0.772, and Ct oS 14= .
% 84 ,/ 3.8 ,/ 5.34 === SdaSS kggkgkJh
Assume safety factor of 5 %, and the supply air flow rate is,
-
kWQTotal 477779.46405.1 ==
skghh
Qm
SR
Totala / 83.33341.48
477 =
=
=&
The ventilation air for persons is skgmm oven / 425.4== && .
The return air should be, skgmmm oaR / 405.29 425.483.33 === &&&
Heat balance of mixing point m to calculate enthalpy of state m,
maRRoo hmhmhm &&& =+
mh=+ 83.334.48405.294.76425.4
damm kggkgkJh / 2.10 ,/ 1.52 ==
Process mS, cooling and dehumidification from m to S and straight to saturation
conditions to locate the apparatus dew point ADP,
CADPtkggkgkJh oadaaa 8.9 ,/ 8.7 ,/ 5.28 ====
Cooling coil capacity,
TRhhm
RC Sma 117.1705.3
)5.341.52(83.33
5.3
)(==
=
&
Cooling coil efficiency,
% 58.747458.05.281.52
5.341.52 ===
=am
Smcoil hh
hh
Bypass factor,
% 42.252542.07458.011 ==== coilBF
Condensate water,
min/ 857.36010)3.82.10(83.33 ),( 3 kgmmm wSmaw ===
&&&
Winter Heating Load)(
@ @?
-
Heat transmission through walls
KmWU ./ 946.1 2=
. 1739)5.1310362(132)3040[( 2mA =++=
WTUAQWalls 504.54145)248(1739946.1 ===
Heat transmission through ceiling
KmWU ./ 199.2 2=
WTUAQCeiling 8.42220)248()3040(199.2 ===
Heat transmission through floor
KmWU ./ 749.2 2=
WTUAQFloor 8.52780)248()3040(749.2 ===
Heat transmission through doors
Assume the doors from wood with 4 cm thickness.
KmWU ./ 994.1 2=
WTUAQDoors 544.1148)248()36(2994.1 ===
Transmission Load is,
WQTrans 648.150295544.11488.527808.42220504.54145 ==
Heat transmission through glass windows
Assume clear glass of 3 mm thickness and Venetian medium shading.
KmWU ./ 301.6 2=
WTUAQGlass 72.4536)248()5.1310(301.6 ===
Ventilation and Infiltration
Room volume, 3 15600133040 mV == , and is tight room
From table (9-12), 41.0=AN , the infiltration (air change rate),
skgVNm A / 096.218.1156003600
41.0inf === &
From tables (9-14), (9-15), smoking persons and seated rest, ventilation is,
skgVNm Pven / 425.418.110)5.7500(3 === &&
)()( inf, RoPvenLeakS TTCmmQ a += &&
-
WQ LeakS 68.104857)248(1005)425.4096.2(, =+=
fgRovenLeakL hmmQ += )()( inf, &&
WQ LeakL 556.5647010254710)5.91.6()425.4096.2(33
, =+=
Lighting Load
RbuLight LCLFFFQ =
WQLight 19872)4030(1592.02.11 ==
Appliances Load
WPowerQApp 10000==
Persons Load
WHCLFNQ SPPerS 363757597.0500, ===
WHNQ LPPerL 2000040500, ===
Sensible, Latent and Total Load
36375100001987268.10485772.4536648.1502951
, +++== i
iSS QQ
kWWQS 443.193 048.193443 ==
kWWQQi
iLL 471.76 556.7647020000556.564701
, ==+==
kWQTotal 914.269471.76443.193 ==
LQ)( SQ)(
.
Room sensible heat factor
% 67.717167.0914.269
443.193 ===
Total
S
Q
QRSHF
Ct oS 34=.
-
From Psychrometric chart, the air properties are,
daooR kggkgkJhkgkJh / 1.6 ,/ 23 ,/ 1.48 ===
Process SR is parallel to 7167.0=RSHF , and Ct oS 34= .
% 34 ,/ 11 ,/ 5.62 === SdaSS kggkgkJh
For sensible heating process in secondary heater 2S, state 2 at 90 RH.
% 90 ,/ 11 ,/ 45 222 === dakggkgkJh
Assume safety factor of 5 %, and the supply air flow rate is,
kWQTotal 41.283914.26905.1 ==
-
skghh
Qm
RS
Totala / 681.191.485.62
41.283 =
=
=&
The ventilation air for persons is skgmm oven / 425.4== && .
The return air should be, skgmmm oaR / 256.15 425.4681.19 === &&&
Heat balance of mixed point m,
maRRoo hmhmhm &&& =+
mh=+ 681.191.48256.1523425.4
Ctkggskgh omdamm 3.20 ,/ 7.8 ,/ 46.42 ===
Process 12, adiabatic air washer from 1 to 2 at 90 % RH, dam kggkgkJh / 7.8 ,/ 45 11 ===
Process 12a, adiabatic air washer from 1 to 2 to a at 100 % RH,
State a, Ctkgg oadaa 16 ,/ 5.11 ==
kWhhmPower ma 50)46.4245(681.19)( 11 === &
kWhhmPower Sa 418.344)455.62(681.19)( 22 === &
% 14.828214.07.85.11
7.8112 ==
=
=ma
mwasher
The water consumed in the adiabatic air washer is,
min/ 716.26010)7.811(681.19)( 32 kgmm maw ===&&
.
)e LoadCold Storag(
Cold storage
.
-
)External Heat Loads(
)Transmission Load(
.
)( TTTUAQ RoTran += (9-19)
U A Ro TT ,
T
T ) -(
ASHRAE 1998.
)Infiltration Load(
infQ
sm &InfV ASHRAE 1998 /3.
( )5.1
3.0
5.05.04inf )/(1
2/1)(1021.2
+=
oRRogHAV
& (9-20)
( ) RRoInfInf hhVQ = & (9-21)
A H Ro hh Ro , ,
. g
)Product Load(
-
.
[ ])()( 21Pr TTCLTTTCTimem
Q fPbfPaP
od ++= (9-22)
Time Pm
fT 1T PaC
2T .
LT kgkJ Co 0 334 /
) -(
.
)on HeatRespirati(
.
hPs RmQ =Re (9-23)
hR ASHRAE 1998
)-( Co 25 Co 0
Co 10
.
)Internal Heat Load(
)Loadcy Occupan(
PerQ
ASHRAE 1998
.Watt
PRPPer FTNQ = )6-(272 (9-24)
-
PN CT oR PF
PF=1
25.1=PF .
)Appliances Load(
. ASHRAE 1998
( ) = 1PowerQApp (9-25)
)Safety Factor(
5~20 %
2.1~05.1=SF
.
=i
iTotal QSFQ1
(9-26)
)Cooling Time(
khLBi =/
ASHRAE 1998
.
+
+
=4
12
2
1
1 Bi
T
H
T
H
hA
V
s
(9-27)
Where )(1 fiPa TTCH = , )(2 cfPb TTCLTH +=
mfi T
TTT
+=
21 , mf TTT = 2 , khLBi /=
-
V h sA Bi
k L
iT mT fT cT
PbPa LT CC ,
.
Example 9-2
Estimate the product load of kg 1500 beef from Co 18 to Co 18 in hr 6 .
Data: kgmP 1500= , CTo 181 = , CT
o 182 = , hr 6
Required: odQPr
Solution
From table (9-17), Beef properties are,
kgkJCkgkJCCTkgkJLT PbPao
f / 72.1 ,/ 43.3 , 7.1 ,/ 231 ====
)()([ 21Pr TTCLTTTCtime
mQ fPbfpa
Pod ++=
kWQ od 61.22))]18(7.1(72.1231))7.1(18(43.3[36006
1500Pr =++
=
Example 9-3
Cold storage of 3 82015 m maintains at dbt 4 Co and RH % 70 . The outside
conditions are dbt 35 Co and wbt 26 Co . The wall consists of cm 20 common
bricks, cm 5.7 cork board, and cm 3 cement layer at inside and outside surfaces. The
ceiling consists of cm 20 concrete, cm 10 cork board, cm 10 ceramic layer, and
cm 3 cement layer at inside surface. The floor consists of cm 10 concrete, cm 5 cork
board, cm 5 ceramic layer. The inside convection heat transfer coefficient is
KmW ./ 9 2 and outside is KmW ./ 23 2 . A 75 tons of Potatoes received at Co 30 are
to be cooled to Co 10 in hr 35 . Lighting load is W 800 and W 1500 fan motor with
efficiency of % 75 . Assume 4 workers of part work and safety factor of % 15 .
Data: Room 3 82015 m , inside dbt 4 Co and RH % 70 , outside dbt 35 Co
and wbt 26 Co , hi= KmW ./ 9 2 , ho= KmW ./ 23 2 , 75 ton of Potatoes
-
from Co 30 to Co 10 , Time is hr 35 , W 800 Lighting and W 1500 fan motor,
efficiency % 75 , SF is % 15 .
Required: Cooling Load, TotalQ
Solution
Transmission Load
Overall heat transfer coefficient for walls, Ceiling and Floor and load,
)( , 111 TTTUAQhk
x
hU Rooi+=++=
Walls, KmWUU
./ 443.0 23
1
7.0
03.0
043.0
075.0
73.0
2.0
7.0
03.0
9
11 2=+++++=
WQE 8.24804)4-(35 820 443.0 =+=
WQW 8.24804)4-(35 820 443.0 =+=
WQS 44.1807)34-(35 815 443.0 =+=
WQN 96.16474)-(35 815 443.0 ==
WQwalls 841796.164744.18078.24808.2480 =+++=
Ceiling, KmWUU
./ 3504.0 23
1
67.0
1.0
043.0
1.0
1.1
2.0
7.0
03.0
9
11 2=+++++=
WQC 8.4204)94-(35 2015 3504.0 =+=
Floor, KmWUU
./ 1133.0 67.0
05.0
043.0
05.0
1.1
1.0
9
11 2=+++=
-
WQF 69.10534)-(35 2015 1133.0 ==
kWWQQQQ FCWallsTrans 676.13 49.1367569.10538.42048417 ==++=++=
Infiltration Load
kgkJhmkg oo / 19.80 ,/ 114.13 == , kgkJhmkg RR / 84.12 ,/ 266.1
3 ==
KTKT oR 308 , 277 ==
( )5.1
3.0
5.05.04inf )/(1
2/1)(1021.2
+=
oRRogHAV
&
( )5.1
3.0
5.05.04inf )114.1/266.1(1
2266.1/114.11)481.9)(43(1021.2
+= V&
smV / 10573.5 33inf=&
( ) kWhhVQ RRoInfInf 4752.0266.1)84.1219.80(10573.5 3 === &
Product Load
[ ] kWTTCTime
mQ fPa
Pod 381.37)]1030(14.3[360035
75000)( 1Pr =
==
Respiration Load
kWWRmQ hPs 075.3 30757.4175Re ====
Occupancy Load
kWWFTNQ PRPPer 24.1 124025.1)46272(4)6-(272 ====
Lighting Load
kWWQLight 8.0 800 ==
Appliances Load
( ) kWWPowerQApp 375.0 375)75.01(15001 ====
Assume 15.1=SF
kWQTotal 576.65)375.08.024.1075.3381.374752.0676.13(15.1 =++++++=
Example 9-4
A piece of beef of 3 102.0165.0279.0 m at Co 07 is to be cooled in air blast freezer
of Co 25 . The convection heat transfer coefficient is )./( 48 2 KmWh = . Estimate
the cooling time of the piece to cool its center to Co 20 and product load.
-
Data: Beef of 3 102.0165.0279.0 m , CT oi 07= , CTo
c 20= , CTo
m 25=
)./( 48 2 KmWh =
Required: Cooling time and odQPr
Solution
From table (9-17), the thermo physical properties of beef are,
)./( 3430 KkgkJCPa = , )./( 1720 KkgkJCPb = , CTo
f 7.1= , kgJLT / 231000=
)./( 48 2 KmWh = , )./( 379.0 KmWk = , 3/ 1080 mkg=
Biot number,
mL 051.02
102.0 ==
459.6379.0
051.048 ===k
hLBi
Room volume, 3 0047.0102.0165.0279.0 mV ==
Product mass and surface area, kgVmP 076.50047.01080 ===
2 136611.0165.0279.0102.0)165.0279.0(2 mAs =++=
3831 / 101743.1))7.1(30(1043.31080)( mJTTCH fiPa ===
[ ] [ ] 382 / 10835.2))20(7.1(17202310001080)( mJTTCLTH cfPb =+=+=
CTTT
T omfi 65.41)25(
2
)7.1(35
21=+=
+=
CTTT omf 3.23)25(7.12 ===
+
+
=4
12
2
1
1 Bi
T
H
T
H
hA
V
s
hrs 802.7 4.280874
459.61
3.23
10835.2
65.41
101743.1
136611.048
0047.0 88 ==
+
+
=
Product load,
[ ])()( 21Pr TTCLTTTCtimem
Q fPbfpaP
od ++=
kWQ od 0702.0))]20(7.1(72.1231))7.1(35(43.3[3600802.7
076.5Pr =++
=
-
Problems
1- A waiting hall of 40x30x8 m3 maintained at 24 C and RH= 50 %. Calculate the
cooling load and RSHF of the hall if the outside condition is 40 C and 30 %
RH. The heat transmission through walls, ceiling and floor is 16 kW. The solar
heat gain through windows is 3.5 kW. The lighting density is 12 W/m2 of floor
area. The number of persons is 100 and 6 kW of appliances. The room is
medium tightness. The air density is 1.181 kg/m3 and specific heat is 1.005
kJ/(kg. K). Evaporation heat for water vapor is 2454 kJ/kg.
2- Room of 5x6x3.5 m3 maintained at 24 C and RH= 50 %. Calculate the cooling
load and RSHF of the room if the outside condition is 35 C and 40 % RH. The
heat transmission load is 9 kW. The room has one window of 1.2x1 in 6 m south
wall and other in 5 m east wall. The lighting load is 200 W. The number of
persons is 10. The room is medium tightness and wind speed is 4 m/s. The air
density is 1.16 kg/m3 and specific heat is 1.004 kJ/(kg. K). Evaporation heat for
water vapor is 2445 kJ/kg.
3- A training hall of 3 123040 m is maintained at dbt 24 Co and RH % 50 . The
room is at latitude of N 30 o , 21 of August, solar time of hr 15 and ambient
condition of dbt 39 Co and wbt 24 Co . The ceiling is from cm 20 concrete, cm 5
insulation, cm 8 ceramic and cm 3 cement layer from inside. The walls are from
common bricks of cm 20 , cm 5 insulation and cm 3 cement layer from inside and
outside. The floor is from concrete of cm 10 over unconditioned space, cm 5
ceramic and cm 3 cement layer from outside. The inside convection heat transfer
is KmWhi ./ 82= and outside KmWho ./ 19
2= . The number of persons is 300 and
fluorescent light intensity is 2/ 20 mW of floor area. The appliances load is kW 5 .
The walls 40 m are at North/South directions with one door of m 34 in each
wall. There are 3 windows in East and West walls of m 25.1 . Calculate the total
cooling load TotalQ and room sensible heat factor, RSHF in summer. If the ambient
-
condition in winter is dbt 10 Co and RH % 90 , calculate the total cooling load
TotalQ and RSHF .
4- A freezing room maintained at -25 oC. Beef of 30 ton at 15 oC to be cooled -25
oC in 16 hr. Thermal properties of Beef are, freezing point is -1.7 oC, latent heat
= 231 kJ/kg, specific heat above freezing is 3.43 kJ/(kg. K), and below freezing
is 1.72 kJ/(kg. K). Heat transmission, air change and other appliances loads are
estimated to be 6 kW. Estimate the cooling load in TR and assuming safety
factor of 10 %.
5- Calculate the cooling load for cold storage at 5 oC dbt and 90 % RH. Outside
air condition are 30 oC dbt and 24 oC wbt. The room volume is 10x15x6 m3
with door of 3x4 m2 and overall heat transfer coefficient for the exposed area
0.32 W/(m2. K). Apples of 20 ton are received at 30 oC and to be cooled to 2
oC in 18 hr. Lighting of 600 W and 750 W fan motor. There are 6 workers and
10 % safety factor. Assume the walls 15 m is North and South.
6- A freezing room of 10x12x6 m3 at -18 oC receives 30 ton of fish at 25 oC to
frozen it to -16 oC in 12 hrs. The room wall consists of 20 cm hall bricks, 7.5
cm cork board, and 5 cm cement layer at inside and outside. The ceiling consists
of 15 cm concrete, 10 cm cork board and 10 cm cement layer. The floor consists
of 10 cm concrete, 5 cm cork board and 5 cm cement layer. The inside and
outside heat transfer coefficient is 8 and 19 W/(m2. K). Number of air changes
per hour is 1 % of the room volume. The lighting load is 400 W and 5 workers.
Calculate the unit refrigeration capacity with 10 % safety factor.
7- A tank of milk with dimensions of 3 251510 cm at Co 20 is to be cooled to
Co 5 . The convection heat transfer coefficient is )./( 55 2 KmWh = and the
temperature cooling medium is Co 2 . Estimate the cooling time and product
load.
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Table (9-1) Walls CLTD oC values from ASHRAE, 1985
Solar time 6 7 8 9 10 11 12 13 14 15 16 17 18
Wall group A, common bricks mm 203 , KmWU ./1 379.1~874.0 2= N 7 7 6 6 6 6 6 6 6 6 6 6 6 E 12 11 11 10 10 10 11 11 12 12 13 13 14 S 10 9 9 9 8 8 8 8 8 8 8 9 9 W 14 13 13 12 12 11 11 10 10 10 10 10 11
Wall group B, common bricks mm 203 , KmWU ./1 714.1 2= N 6 6 6 5 5 5 5 5 5 5 6 6 7 E 10 9 8 8 9 9 10 12 12 13 14 14 15 S 9 8 7 7 6 6 6 6 7 8 9 10 11 W 13 12 11 10 9 9 8 8 8 8 8 9 11
Wall group C, concrete bricks mm 203 , KmWU ./1 561.1~255.1 2= N 5 5 4 4 4 4 5 5 6 6 7 8 9 E 8 7 7 8 9 11 13 14 15 16 16 17 17 S 7 6 6 5 5 5 5 6 8 9 11 12 13 W 11 10 9 8 7 7 7 7 7 8 9 11 13
Wall group D, common bricks mm 6.101 , KmWU ./1 356.2 2= N 4 3 3 3 3 4 4 5 6 6 7 8 9 E 5 5 5 7 10 13 15 17 18 18 18 18 18 S 5 4 4 2 3 4 5 7 9 11 13 15 16 W 9 7 6 5 5 5 5 6 6 8 10 13 17
Wall group E, concrete mm 6.101 , KmWU ./1 811.1 2= N 2 2 2 3 3 4 5 6 7 8 10 10 11 E 3 3 6 10 15 18 20 21 21 20 19 18 18 S 3 2 2 2 3 5 7 10 14 16 18 19 18 W 5 4 3 3 3 4 4 5 6 8 11 15 20
Wall group F, hall bricks mm 6.101 , KmWU ./1 493.1~914.0 2= N 1 1 2 3 4 5 6 8 9 11 12 12 13 E 1 4 9 16 21 24 25 24 22 20 19 18 17 S 1 1 1 2 4 7 11 15 19 21 22 21 19 W 2 2 2 2 3 4 6 8 11 16 22 27 32
Ceiling group 3, concrete mm 100 , KmWU ./1 209.1 2= -2 -2 1 5 11 18 25 31 36 39 40 40 37
Ceiling group 6, concrete mm 152 , KmWU ./1 897.0 2= 2 1 0 2 4 8 13 18 24 29 33 35 36
Ceiling group 6, concrete mm 203 , KmWU ./1 715.0 2= 8 6 5 4 4 5 7 11 14 18 22 25 28
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Table (9-2) LM values for latitudes 24o to 40o of walls and roofs ASHRAE, 1989.
Latitude North
Month N NE NW
E W
SE SW
S Horizontal
24
Dec -2.7 -5.0 -3.8 1.6 7.2 -7.2 Jan/Nov -2.2 -4.4 -3.3 1.6 7.2 -6.1 Feb/Oct -2.2 -3.3 -1.6 1.6 5.5 -3.8 Mar/Sep -1.6 -1.6 -0.5 0.5 2.2 -1.6 Apr/Aug -1.1 0.0 -0.5 -0.5 -1.6 0.0 May/Jul 0.5 1.1 0.0 -1.6 -3.3 0.5
Jun 1.6 1.6 0.0 -2.2 -2.3 0.5
32
Dec -2.7 -5.5 -4.4 1.1 6.6 -9.4 Jan/Nov -2.7 -5.0 -4.4 1.1 6.6 -8.3 Feb/Oct -2.2 -3.8 -2.2 2.2 6.1 -5.5 Mar/Sep -1.6 -2.2 -1.1 1.6 3.8 -2.7 Apr/Aug -1.1 -0.5 0.0 0.0 0.5 -0.5 May/Jul 0.5 0.5 0.0 -0.5 -1.6 0.5
Jun 0.5 1.1 0.0 -1.1 -2.2 1.1
40
Dec -3.3 -5.5 -5.5 0.0 5.5 -11.6 Jan/Nov -2.7 -5.5 -5.0 0.5 6.1 -10.5 Feb/Oct -2.7 -4.4 -3.3 1.6 6.6 -7.7 Mar/Sep -2.2 -2.7 -1.6 2.2 5.5 -4.4 Apr/Aug -1.1 -1.1 0.0 1.1 2.2 1.6 May/Jul 0.0 0.0 0.0 0.0 0.5 0.5
Jun 0.5 0.5 0.5 0.0 -0.5 1.1 Table (9-3) Percentage of daily range, ASHARE 1997.
Solar Time, hr Tm % Solar Time, hr Tm % Solar Time, hr Tm % 1:00 87 9:00 71 17:00 10 2:00 92 10:00 56 18:00 21 3:00 96 11:00 39 19:00 34 4:00 99 12:00 23 20:00 47 5:00 100 13:00 11 21:00 58 6:00 98 14:00 3 22:00 68 7:00 93 15:00 0 23:00 76 8:00 84 16:00 3 24:00 82
Table (9-4) CLTD oC for glass windows
Solar time, hr CLTD Solar time, hr CLTD Solar time, hr CLTD 6:00 -1 11.00 4 16:00 8 7:00 -1 12.00 5 17:00 7 8:00 0 13.00 7 18:00 7 9:00 1 14.00 7 19:00 6 10:00 2 15.00 8 20:00 4
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Table (9-5) SC Shading coefficient for glass windows Glass type
Thickness mm
Without Shading
With Shading
Venetian Blind or Roller Medium Light Dark Medium Light
SC SC
Clear
3 1 0.64
0.55
0.59
0.25
0.39 6 0.95
10 0.92 12 0.88
Absorbent
3 0.85 0.57
0.53
0.45
0.30
0.36 6 0.73
10 0.64 12 0.53
Table (9-6) SHGFmax W/m
2 from glass window exposed to solar radiation Month
Latitude o 24 N NE
NW E W
SE SW
S Horizontal
January 85 129 599 798 716 675 February 95 252 694 767 606 786 March 107 391 738 675 432 868 April 117 502 719 533 237 893 May 136 562 688 416 145 890 June 174 581 669 369 136 880 July 142 555 672 407 145 877 August 120 492 694 511 227 874 September 110 375 700 650 423 839 October 98 249 666 741 590 770 November 85 133 590 786 707 672 December 82 91 568 779 748 628
Table (9-7) SHGFmax W/m
2 from glass window exposed to solar radiation Month
Latitude o 28 N NE
NW E W
SE SW
S Horizontal
January 79 110 577 792 751 618 February 91 227 672 776 653 738 March 104 366 729 697 495 836 April 114 476 719 562 297 877 May 126 543 691 454 183 883 June 161 562 672 404 155 877 July 129 536 678 442 180 870 August 120 470 694 543 287 858 September 107 350 691 672 486 808 October 95 224 644 751 637 722 November 82 110 571 779 741 615 December 75 76 543 782 776 565
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Table (9-8) SHGFmax W/m
2 from glass window exposed to solar radiation Month
Latitude o 32 N NE
NW E W
SE SW
S Horizontal
January 76 91 552 876 776 555 February 85 205 647 782 697 685 March 101 338 716 716 555 795 April 114 461 716 590 363 855 May 120 536 694 489 233 874 June 139 555 675 439 189 871 July 126 527 678 473 227 861 August 117 445 691 571 350 836 September 104 325 678 688 540 770 October 88 199 615 754 678 672 November 76 91 546 773 767 552 December 69 69 511 776 795 498
Table (9-9) CLF for glass windows without inside shade Solar Time, hr
N E S W
L M H L M H L M H L M H
6.00 0.33 0.34 0.38 0.19 0.18 0.2 0.06 0.08 0.11 0.06 0.09 0.11 7.00 0.42 0.41 0.45 0.37 0.33 0.34 0.09 0.11 0.14 0.07 0.09 0.12 8.00 0.48 0.46 0.49 0.51 0.44 0.45 0.14 0.14 0.17 0.08 0.10 0.13 9.00 0.56 0.53 0.55 0.57 0.50 0.49 0.22 0.21 0.24 0.10 0.11 0.14 10.00 0.63 0.59 0.60 0.57 0.51 0.49 0.34 0.31 0.33 0.11 0.12 0.14 11.00 0.71 0.65 0.65 0.50 0.46 0.43 0.48 0.42 0.43 0.12 0.13 0.15 12.00 0.76 0.70 0.69 0.42 0.39 0.36 0.59 0.52 0.51 0.14 0.14 0.16 13.00 0.80 0.73 0.72 0.37 0.35 0.22 0.65 0.57 0.56 0.20 0.19 0.21 14.00 0.82 0.75 0.72 0.32 0.31 0.29 0.65 0.58 0.55 0.32 0.29 0.30 15.00 0.80 0.76 0.73 0.29 0.29 0.26 0.59 0.53 0.50 0.45 0.40 0.40 16.00 0.79 0.74 0.70 0.25 0.26 0.24 0.50 0.47 0.43 0.57 0.50 0.49 17.00 0.75 0.75 0.70 0.22 0.23 0.22 0.43 0.41 0.37 0.64 0.56 0.54 18.00 0.84 0.79 0.75 0.19 0.21 0.19 0.36 0.36 0.32 0.61 0.55 0.52 19.00 0.61 0.61 0.57 0.15 0.17 0.17 0.28 0.29 0.26 0.44 0.41 0.38 20.00 0.48 0.50 0.46 0.12 0.15 0.15 0.22 0.25 0.22 0.34 0.33 0.30
L denotes light walls and ceiling of 50.8 mm concrete 146 kg/m2 floor area, M denotes
walls and ceiling of 101.6 mm concrete 341 kg/m2 floor area,, H denotes walls and ceiling of 152.4 mm concrete 653 kg/m2 floor area,.
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Table (9-10) CLF for glass windows with inside shade
Solar time, hr N E S W Horizontal 6.00 0.73 0.47 0.09 0.06 0.12 7.00 0.66 0.72 0.16 0.09 0.27 8.00 0.65 0.8 0.23 0.11 0.44 9.00 0.73 0.76 0.38 0.13 0.59 10.00 0.80 0.62 0.58 0.15 0.72 11.00 0.86 0.41 0.75 0.16 0.81 12.00 0.89 0.27 0.83 0.17 0.85 13.00 0.89 0.24 0.8 0.31 0.85 14.00 0.86 0.22 0.68 0.53 0.81 15.00 0.82 0.2 0.50 0.72 0.71 16.00 0.75 0.17 0.35 0.82 0.58 17.00 0.78 0.14 0.27 0.81 0.42 18.00 0.91 0.11 0.19 0.61 0.25 19.00 0.24 0.06 0.11 0.16 0.14 20.00 0.18 0.05 0.09 0.12 0.12
Table (9-11) Summer air change rate, McQuiston 1985. Outdoor Design Temperature, oC
29 32 35 38 41 43 Type
AN Number of air change from room volume per hour Tight 0.33 0.34 0.35 0.36 0.37 0.38 Medium 0.46 0.48 0.50 0.52 0.54 0.56 Loose 0.68 0.70 0.72 0.74 0.76 0.78
Note: values for wind velocity of 3.4 m/s and indoor temperature of 24 oC. Table (9-12) Winter air change rate, McQuiston 1985. Outdoor Design Temperature, oC
10 4 -1 -7 -12 -18 Type
AN Number of air change from room volume per hour Tight 0.41 0.43 0.45 0.47 0.49 0.51 Medium 0.69 0.73 0.77 0.81 0.85 0.89 Loose 1.11 1.15 1.20 1.23 1.27 1.3
Note: values for wind velocity of 6.7 m/s and indoor temperature of 20 oC. Table (9-13) Constants of Eq. (9-9) for number of air change per hour. Type a b c Tight 0.15 0.010 0.007 Medium 0.20 0.015 0.014 Loose 0.25 0.020 0.022
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Table (9-14) Ventilation rate for persons.
Place No. of persons per 2 100 m of floor area
Ventilation per person in lit/s Non smoking persons Smoking persons
Offices 7 2.5 10 Conference or waiting halls
60 3.5 17.5
Seated rooms 30 2.5 7.5 Table (9-15) Heat gains from occupants.
Activity
Metabolic rate
WQP ,
Heat Liberated, W Room dry bulb temperature, oC
20 22 24 26
SH LH SH LH SH LH SH LH
Seated rest 115 90 25 80 35 75 40 65 50 Office work 140 100 40 90 50 80 40 70 70 Standing 150 105 45 95 55 82 68 72 78 Restaurant 160 110 50 100 60 85 75 75 85 Light work 235 130 105 115 120 100 135 80 155 Dancing 265 140 125 125 140 105 160 90 175
Table (9-16) CT o to compensate solar effect on transmission load for cold storage Surface types East West South Ceiling Dark colored surfaces 5 5 3 11 Medium colored surfaces 4 4 3 9 Light colored surfaces 3 3 2 5
Dark colored surfaces as slate roofing, tar roofing, and black paint. Medium colored surfaces as unpainted wood, brick, red tile, dark cement, and red, gray or green paint. Light colored surfaces as white stone, light colored cement, and white paint.
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Table (9-17) Thermal properties of some common foods
Product Moisture %
hR
tonW /
LT kgkJ /
fT
Co
PaC
KkgkJ ./ PbC
KkgkJ ./
Water 100 - 334 0.0 4.18 2.06 Beans, 1.68 3.06 0.6- 235 58 70.2 Beets, 1.68 3.77 1.1- 293 34.9 87.6 Cabbage, 1.97 3.94 0.9- 308 93.1 92.2 Carrots, 1.93 3.77 1.4- 293 93.1 87.8 Cauliflower, 1.97 3.89 0.8- 307 100.4 91.9 Corn, 1.77 3.32 0.6- 254 332.2 76 Garlic, 1.76 3.31 0.8- 196 27.2 58.6 Leaks, 1.97 3.98 0.7- 277 159.1 83 Mushrooms, 1.97 3.89 0.9- 307 210 91.8 Okra, 1.93 3.85 1.8- 299 259 89.6 Onions, 1.93 3.77 0.9- 300 14.7 89.7 Peas, 1.97 3.89 1.1- 307 163.4 91.9 Potatoes, 1.68 3.14 1.3- 243 15 72.8 Potatoes, 1.82 3.63 0.6- 264 41.7 79 Peppers, 1.97 3.94 0.7- 308 42.7 92.2 Spinach, 2.01 3.94 0.3- 306 173 91.6 Tomatoes, 2.01 3.98 0.6- 311 60.6 93 Turnip, 1.97 3.89 1.1- 307 28.1 91.9 Apples, 1.84 3.6 1.1- 280 35.9 83.9 Apricots, 1.93 3.68 1.1- 288 33 86.3 Bananas, 1.76 3.35 0.8- 248 59.7 74.3 Grapes, 1.83 3.6 1.6- 272 16 81.3 Lemon, 1.93 3.85 1.4- 292 47 87.4 Mangos, 1.93 3.77 0.9- 273 133.4 81.7 Watermelon, 2.01 4.06 0.4- 306 22.3 91.5 Orange, 1.93 3.77 0.8- 275 40.3 82.3 Peaches, 1.93 3.77 0.9- 293 46.6 87.7 Pears, 1.89 3.75 1.6- 280 23.3 83.8 Strawberries 91.6 145.5 306 -0.8 3.89 1.14 Egg, 1.95 3.83 0.6- 293 - 87.8 Cod, 2.05 3.77 2.2- 271 - 81.2 Tuna, 1.72 3.18 2.2- 228 - 68.1 Mackerel, 1.55 2.76 2.2- 212 - 63.6 Beef, 1.72 3.43 1.7- 231 - 69.0 Chicken, 1.55 3.31 2.8- 220 - 66.0 Milk, 1.94 3.85 0.6- 293 - 87.7
hR , respiration heat in tonW / at average temperature of Co 15~10 .