Building Heat Load Calculation 魏晓永Word下载.docx
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Building Heat Load Calculation 魏晓永Word下载.docx
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(1)Concretefloorof20cmthickness,withtotalfloorareaof160m2(16mx10m).
(2)Oneexteriorwall,facingsouth,16mx3.8m,composedofthefollowinglayers(fromoutsidetoinside):
brick,aircavity,metalstudswiththecavityfilledwithfiberglassbattinsulationof75mmthickness,andgypsumboard.
(3)Noexteriorwindowsanddoors.
(4)Airinfiltrationrateisequalto0ACH.Nointernalgains(people,lights,equipment).
(5)Thermostatsetpointequalto24℃,withthrottlingrangeof0.5℃.
(6)Datafortheoutsidesurfaceofexteriorwall:
hconvection=17W/m2K;
α=0.8.
(7)Datafortheinsidesurfaceofexteriorwall:
hconvection=4W/m2K;
hradiation=3W/m2K.
(8)Insidesurfacetemperaturesofallpartitions,floor,ceiling,andfurnitureis24.0℃.
(9)Table1showstheweatherdataforasummerdesignday.
Table1.Weatherdataforasummerdesignday
Hour
OutdoorairtemperatureT0[℃]
Totalsolarradiationnormaltotheexteriorwall[W/m2]
1
19.9
2
19.7
3
18.5
4
5
18.0
6
19.0
7
19.6
8
21.0
300
9
27.0
800
10
27.5
970
11
30.7
1200
12
35.0
1300
13
38.7
14
42.8
15
38.8
16
37.1
17
18
29.0
19
25.0
20
23.5
21
22.6
22
21.2
23
24
20.2
3.RadiantTimeSeries(RTS)Method
3.1calculatesol-airtemperature
:
Outdoorairtemperature℃
outersurfaceflowheattransfercoefficientW/(m2.k)
outersurfaceofsolarradiationabsorptioncoefficient
IntensityofsolarradiationW/m2
Outersurfaceofthelong-waveradiationcoefficient
Poorlong-waveradiationW/m2
3.2calculateheatgain
ConductiveheatinputforthesurfacenhoursagoW
OverallheattransfercoefficientforthesurfaceW/(m2.k)
Surfaceaream2
Sol-airtemperaturenhoursago℃
Presumedconstantroomairtemperature℃
Conductiontimefactors
j=0meanscurrenthour
and
Conductiveheatgainthroughwallscontainstwoparts:
convectivecoolingload(
)andradiantcoolingload(
).BysearchingthetableofconvectiveandradiantpercentagesofTotalSensibleHeatGain,wecanget:
Becauseoftime-delayeffects,radiantcoolingload(
)forthecurrenthour(θ)
from
RadiantheatgainnhoursagoW
3.6calculatecoolingload
4.CalculationresultsofRTS
4.1Sol-airtemperature
TheresultsofSol-airtemperature
areshownasTable2:
Table2Sol-airtemperature
Outdoorairtemperaturet0[℃]
sol-airtemperature
[℃]
35.11765
64.64706
73.14706
87.17059
96.17647
95.17059
88.44706
76.44706
51.21765
35
29
25
Figure1showstheresultsofRTSmethod
Figure1Theresultsofthesol-airtemperature
4.2calculateheatgain
Wehavethefigure2:
Figure2Theresultsoftheheatgain
4.3calculatecoolingload
Figure3showstheresultsof
Figure3Comparisonofheatgainandcoolingload
Fromthefigureswecangetthattheheatgainat16:
00isthehighest,1946Wandwithaphasedelayandattenuationofpeak,thecoolingloadat17:
00isthehighest,1634W.
5.HeatBalanceMethod
HBmethodcanbeviewedasfourdistinctprocedures:
(1)outside-faceheatbalance;
(2)wallconductionprocess;
(3)inside-faceheatbalance;
(4)airheatbalance.
Equationofoutside-faceheatbalanceis:
(1)
Where
=absorbeddirectanddiffusesolarradiationflux(q/A),W/m2.
=Netlong-waveradiationfluxexchangewithairandsurroundings,W/m2.
convectiveexchangefluxwithoutsideair,W/m2.
=Conductiveflux(q/A)intowall,W/m2.
Equationofinside-faceheatbalanceis:
(2)
Where
netlong-waveradiantfluxexchangebetweenzonesurfaces,W/m2.
=Netshort-waveradiationfluxtosurfacefromlights,W/m2.
=Long-waveradiationfluxfromequipmentinzone,W/m2.
=Conductivefluxthroughthewall,W/m2.
=Transmittedsolarradiantivefluxabsorbedatsurface,W/m2.
=Convectiveheatfluxtozoneair,W/m2.
Equationofairheatbalanceis:
(3)
=Convectiveheattransferfromsurfaces,W.
=Convectivepartsofinternalloads,W.
=Sensibleloadcausedbyinfiltrationandventilationair,W.
=Heattransferto/fromHVACsystem,W.
Thegeneralformfortheinsideheatfluxis:
(4)
Foroutsideheatflux,theformis:
(5)
=outsideCTF,k=0,1,…nz;
=crossCTF,k=0,1,…nz;
=insideCTF,k=0,1,…nz;
=fluxCTF,k=0,1,…nq;
=time;
δ=timestep;
=inside-facetemperature,℃;
=outside-facetemperature,℃;
=conductiveheatfluxoninsideface,W/m2;
=conductiveheatfluxonoutsideface,W/m2;
①formulas:
=outside-facetemperature,℃,i=1,2,…,12;
j=1,2,…,24
=inside-facetemperature,℃,i=1,2,…,12;
=coolingload,j=1,2,…,24
Fromequations
(1)and(4),wecanget:
Where:
=outsideairtemperature
=outsideconvectionheattransfercoefficient
Fromequations
(2)and(5),wecanget:
where:
=roomairtemperature
=insideconvectionheattransfercoefficient
Fromtheequation
(2),wecanobtain:
and
areallequalto0.Sowecansimplifyqsys.
②WecanobtaintheCTFsandRadiantTimeSeriesvaluesbyusingthePRFgen.CTFsvaluesareputinTable3,whileCTSandRTSvaluesareputinTable4.
Table3.CTFsvalues
CTF
X-Exterior(W/m2K)
Y-Cross(W/m2K)
Z-Interior(W/m2K)
Flux
11.28142452
0.000322116
4.947700024
-17.19666862
0.014172389
-9.024801254
1.250475287
6.705113411
0.031286769
4.501733303
-0.399797946
-0.757661641
0.009221151
-0.377397597
0.028814277
0.023245038
0.000358497
0.008133379
-0.000552414
-9.0643E-05
9.96527E-07
-6.20116E-06
3.33923E-08
2.71818E-09
6.65832E-11
3.34581E-10
-2.62222E-13
-1.53771E-14
8.40115E-17
-2.27363E-15
-4.46136E-19
Table4.CTSandRTSvalue
CTS
RTS
1.58%
31.3%
24.55%
20.1%
32.26%
13.6%
19.45%
9.49%
10.43%
6.78%
5.53%
4.92%
2.92%
3.60%
1.54%
2.65%
0.82%
1.96%
0.43%
1.46%
0.23%
1.08%
0.12%
0.81%
0.06%
0.60%
0.03%
0.45%
0.02%
0.33%
0.009%
0.25%
0.005%
0.19%
0.003%
0.14%
0.001%
0.10%
0.0007%
0.08%
0.0004%
0.0002%
0.04%
0.0001%
0.00006%
Figure4showstheresultsofRTSandCTS:
Figure4TheresultsofRTSandCTS
③Theresultsofcalculation
Table5showstheresultsofcoolingload.
Table5Theresultsofthecoolingload
Time(h)
Outside-facetemperature
Tso(K)
Inside-facetemperature
Tsi(K)
Coolingload
qsys(W)
298.63
297.213
15.2346
297.766
297.198
11.6499
296.393
297.184
8.3094
295.753
297.17
4.8799
294.917
297.155
1.1814
295.023
297.14
-2.4561
295.028
297.127
-5.6086
304.074
297.119
-7.6353
322.59
297.126
-5.8035
330.08
297.185
8.4085
340.692
297.314
39.7975
348.762
297.483
80.8947
350.836
297.661
124.341
348.901
297.822
163.414
343.073
297.936
191.086
328.413
297.984
202.816
317.623
297.955
195.67
312.421
297.844
168.808
308.5
297.685
130.188
306.129
297.527
91.6669
304.283
297.4
60.8144
302.28
39.8644
301.077
297.262
27.233
299.667
297.232
19.8665
6.ComparisonoftheTwoMethods
Figure5Comparisonofthetwomethods
Figure5showsthecomparisonofthetwomethods.Fromcomparisonwecanget,themaximumvaluesandtheminimumvaluesarealmostatthesametime.Butthevaluesofcoolingloadalmosthavedifferencesateachtime.
7.ProgramofRTSmethodandHBmethod
7.1ProgramofRTSmethod
hour=1:
24;
%时间序列
U=0.4983269;
%总传热系数
A=60.8;
%传热面积
trc=24;
%室内计算温度
a=0.8;
%吸收系数
ho=17;
%墙外表面传热系数
%室外气温
to=[20.2,19.9,19.7,18.5,18.5,18,19,19.6,21,27,27.5,30.7,35,38.7,42.8,38.8,37.1,35,29,25,23.5,22.6,21.2,21];
%综合温度
te=[19.9,19.7,18.5,18.5,18,19,19.6,35.11765,64.64706,73.14706,87.17059,96.17647,95.17059,88.44706,76.44706,51.21765,35,29,25,23.5,22.6,21.2,21,20.2];
plot(h,to,'
--r+'
h,te,'
-bd'
);
h=legend('
airtemperature'
'
Sol-airtemperature'
2)
xlabel('
hour(h)'
)
ylabel('
temperature(℃)'
title('
AirandSor-airtemperature'
gridon
%太阳辐射强度
I=[0,0,0,0,0,0,0,0,300,800,970,1200,1300,1200,970,800,300,0,0,0,0,0,0,0];
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