wotapeta
12-12-2010, 04:38 PM
hello i tried solving these refrigeration problems..plz carry me thru to the end...
PROBLEM # 1(from stoecker)
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a computer room located on the second floor of a five storey office building is 10 by 7m.the exterior wall is 3.5 m high and 10 m long:it is a metal curtain wall(steel backed with 10 mm of insulating board).
75 mm of glass-fibre insulation,and 16 mm of gypsum board.double-glazed windows make up 30 percent of exterior wall.the computer and lights in gthe room operate 24 h/day and have a combined heat release to the space of 2KW.
the indoor temperature is 20 celsius.if the building is located in columbus.ohio,determine the heating load at winter design conditions.
SOLUTION:WHAT I HAVE CUM UP WITH\
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T,in=20 celsius
T,out=-15 C
R,glass=3.3 w/m^2.k
R,gypsium=0.10 m^2.K/W
R,fiber=1.94
W,bulb=2KW
R,steel=0.32 m^2.K/W
please carry this thru to the end...
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PROBLEM # 2
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a fan discharges 300 m^3 of moist air per minute at 30 celsius.1 atm and 92% relative humidity.find the specfic humidity of the mmixture,and the mass of water vapor and dry air through the fan per inute.
the moist air is passed over refrigerator coils in order to dehumifity it,and leaves the refrigerator chamber with a pressure and temperatuire of 1atm and 13 C.the condensate also leaves the chamber at 13 C(enthalpy of saturated liquid is 55 KJ/Kg)
determine the final specific humidity of the mixture,the mass of water condensing on the cooling per minute,and the ratye of heat transfer to the cooling coils
SOLUTION .WHAT I HAVE CUM UP WITH
--------
V,1=300/60=5 m^3/s
T,1=30 C
phi,1=0.92
Psat=4.241
Ps=0.92x4.241=3.90
w,1=0.622xPs/(Pt-Ps)
=0.0249
v,1=RaxT/Pa=
287x(30+273.15)/(101.325-3.90E3)
E=exponential
v,1=0.893 m^3/Kg dry air
m,a=V/v,1=300/0.893
=335.9 kg/s
m,w=w,1xm,a=335.9x0.0249
=8.37 kg water/min
Psat@13 C=1.49935 Kpa=Ps
w,2=0.622(1.49935)/(101.325-1.49935)
w,2=9.342E-3
m,w2=m,a1x w,2
=335.9*9.3e-3
=3.13
delta h=m,aCp(T,2-T,1)+(m,w1-m,w2)xhf+
m,w1(-h,g@13C+ h,g@30 C) + m,w1xh,fg+ m,w1(hf,1-h,f2)
delta h=27194.68 Kj/min
now?
PROBLEM # 1(from stoecker)
------------------------------------
a computer room located on the second floor of a five storey office building is 10 by 7m.the exterior wall is 3.5 m high and 10 m long:it is a metal curtain wall(steel backed with 10 mm of insulating board).
75 mm of glass-fibre insulation,and 16 mm of gypsum board.double-glazed windows make up 30 percent of exterior wall.the computer and lights in gthe room operate 24 h/day and have a combined heat release to the space of 2KW.
the indoor temperature is 20 celsius.if the building is located in columbus.ohio,determine the heating load at winter design conditions.
SOLUTION:WHAT I HAVE CUM UP WITH\
------------------------------
T,in=20 celsius
T,out=-15 C
R,glass=3.3 w/m^2.k
R,gypsium=0.10 m^2.K/W
R,fiber=1.94
W,bulb=2KW
R,steel=0.32 m^2.K/W
please carry this thru to the end...
----------------------------------
PROBLEM # 2
-------------------------------
a fan discharges 300 m^3 of moist air per minute at 30 celsius.1 atm and 92% relative humidity.find the specfic humidity of the mmixture,and the mass of water vapor and dry air through the fan per inute.
the moist air is passed over refrigerator coils in order to dehumifity it,and leaves the refrigerator chamber with a pressure and temperatuire of 1atm and 13 C.the condensate also leaves the chamber at 13 C(enthalpy of saturated liquid is 55 KJ/Kg)
determine the final specific humidity of the mixture,the mass of water condensing on the cooling per minute,and the ratye of heat transfer to the cooling coils
SOLUTION .WHAT I HAVE CUM UP WITH
--------
V,1=300/60=5 m^3/s
T,1=30 C
phi,1=0.92
Psat=4.241
Ps=0.92x4.241=3.90
w,1=0.622xPs/(Pt-Ps)
=0.0249
v,1=RaxT/Pa=
287x(30+273.15)/(101.325-3.90E3)
E=exponential
v,1=0.893 m^3/Kg dry air
m,a=V/v,1=300/0.893
=335.9 kg/s
m,w=w,1xm,a=335.9x0.0249
=8.37 kg water/min
Psat@13 C=1.49935 Kpa=Ps
w,2=0.622(1.49935)/(101.325-1.49935)
w,2=9.342E-3
m,w2=m,a1x w,2
=335.9*9.3e-3
=3.13
delta h=m,aCp(T,2-T,1)+(m,w1-m,w2)xhf+
m,w1(-h,g@13C+ h,g@30 C) + m,w1xh,fg+ m,w1(hf,1-h,f2)
delta h=27194.68 Kj/min
now?