joi, 23 iunie 2011

The procedure for calculating the heat flow necessary for preparing hot water




a)Basic scheme-summer
Φacb  = Gac x C2b x (  tac – t 21 b ) / 3600
Gac = 0.8 x  3600 / 0.9832 = 2929 kg/h

Φacb  = 2929 x 4198.6 x (  60 - 10 ) / 3600
Φacb  = 170800 w

b) Mode  peak - winter
Φacv  = Gac x C2v x (  tac – t 21v ) / 3600
Φacv  = 2929 x 4198.6 x (  60 - 7  ) / 3600 = 181048
Φacv  = 181048

Primary heat flow
Primary water heating

a)Basic scheme-summer
Φ: heat flux [w]
acb : hot water [the regime basic, top]
G: flow of fluid [kg / h]
C: specific heat of fluid [J / kg x degrees]
2b: the primary circuit in the scheme - final value
t: temperature [° C]
Action: hot water in the basic regime
2.1b: secondary circuit in the scheme - initial value
Ψac: specific weight [kg/m3]
                        
VALUES OF STATE FOR WATER TABLE

Tm
Ψac
Cp
     ° K                 ° C
kg/m3
j/kg x °K                         
303
30
995.6
4198.6
313
40
992.2
4198.6
323
50
988
4198.6
333
60
983.2
4202.7
343
70
977.7
4211.1
353
89
971.8
4215.3
363
90
965.3
4223.7
373
100
958.3
4227.9
383
110
951.7
4238.3
393
120
943.1
4248.8
                                     




t ac    = 60° C
t 21 b= 10° C
C2b = 4198.6 j/kg °K for  35 ° C
C1b = 4200    j/kg °K for 55 ° C
C1v = 4220    j/kg °K for  85 ° C

Flow Calculation

STORAGE VOLUME CALCULATION

QA = 3600 x Φacb x 0.8 = 3600 x 170800 x 0.8 = 491.904.000

Volume of water consumption be accumulated
V = QA x 45 / ( tac - 10  ) x C2b x Ψac x 60
V = 491.904.000 x 45/( 60 -10  ) x 4198.6 x 983.2 x 60
V = 1.49 mc
Vertical Boiler
QA = 3600 170800 x 0.57 = 350481600
V = 350481.600 x 45/( 60 -10  ) x 4198.6 x 983.2 x 60 =
V =1.2mc
Choose a vertical boiler with a capacity of 1600 liters

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