chapter 9 ref and air condition

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.

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

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

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



Latitude o 28 N NE

NW E W

SE SW

S Horizontal




Latitude o 32 N NE

NW E W

SE SW

S Horizontal


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,.

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

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.

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 .

chapter 9 ref and air condition

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