A household refrigerator operates with cold- andhot-temperature reservoirs et T c = 5 ° C and T h = 25 ° C , respectively. When new, the cold and hot side resistancesare R c , n = 0.05 K/W and R h , n = 0.04 K/W , respectively.Over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to R h , d = 0.1 K/W . It isdesired to have a refrigerator cooling rate of q i n = 750 W .Using the results of Problem 1 .38, determine the modifiedcoefficient of performance and the required power input W ˙ under (a) clean and (b) dusty coil conditions.
A household refrigerator operates with cold- andhot-temperature reservoirs et T c = 5 ° C and T h = 25 ° C , respectively. When new, the cold and hot side resistancesare R c , n = 0.05 K/W and R h , n = 0.04 K/W , respectively.Over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to R h , d = 0.1 K/W . It isdesired to have a refrigerator cooling rate of q i n = 750 W .Using the results of Problem 1 .38, determine the modifiedcoefficient of performance and the required power input W ˙ under (a) clean and (b) dusty coil conditions.
A household refrigerator operates with cold- andhot-temperature reservoirs et
T
c
=
5
°
C
and
T
h
=
25
°
C
, respectively. When new, the cold and hot side resistancesare
R
c
,
n
=
0.05
K/W
and
R
h
,
n
=
0.04
K/W
, respectively.Over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to
R
h
,
d
=
0.1
K/W
. It isdesired to have a refrigerator cooling rate of
q
i
n
=
750
W
.Using the results of Problem 1 .38, determine the modifiedcoefficient of performance and the required power input
W
˙
under (a) clean and (b) dusty coil conditions.
1- A refrigerator is to serve a cooling load of 16 tons. The machine condenser is air cooled
and the heat rejection ratio is 1.244. The condenser has an air-side area of 210 m and the
overall coefficient of heat transfer based on this area is 37W/m2k. The condenser has a face
area of 2.2 m and the face velocity of air is 3 m/s. Density of ambient air is 1.15 kg/m. If
the condensing temperature is to be limited to 55°C, what is the maximum allowable
ambient temperature ?
A parameter used to characterize the heat pump cycle performance is called the thermal
efficiency. True or False?
A
A Single
system has a cooling capacity of 6 tons. The discharge of the
evaporator is at -20°C & 0.1 MPa and the discharge of the
condenser is at 30°C & 1.0 MPa. Determine the following: (a)
the COP of the system, (b) the Energy Efficiency Ratio in
kJ/hr/W, (c) the HP/ton of the system, (d) the Refrigerating
Efficiency of the system.
Stage Vapor Compression (SSVC) refrigeration
20
우 6 4
+ -
150
140-
170-
T = 160°C
OL
국100-
06-
s= 2.30 kJ/(kg-k)
09
006
220
4-
30:
0001
00
08
1050
06
0g
Saturated Vapor
60
09
8'0
1200
1.70 -
09'1
0.7
1250
90
1.50-
1.40
OL-
1350
8-1.30 -
07-
00L 0E
1.20
FOL
-50 1450
09-
1.10
T=-40°C
00'L
=08'0=
Saturated Liquid
20
-06'0
4.
2.
0.80
0.70
1
PRESSURE, MPa
250
350
009
150
008
00L
007
R-134a
0.2
0.2
2.0
0.04
20'0
zo'o
0.01
009
00S
002
008
001
€ Tiliner-Roth and Baehr (1994
ENTHALPY, kJ/kg
o paseg
SIN m paynduoo saguadod
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