The evaporator section of a heat pump is installed in a large tank of water, which is used as a heat source during the winter. As energy is extracted from the water, it begins to freeze, creating an ice/water bath at 0 ° C , which may be used for air conditioning during the summer. Consider summer cooling conditions for which air is passed through an array of copper tubes, each of inside diameter D = 50 m m , submerged in the bath. (a) If air enters each tube at a mean temperature of T m , i = 24 ° C and a flow rate of m ˙ = 0.01 k g / s , what tube length L is needed to provide an exit temperature of T m , o = 14 ° C ? With 10 tubes passing through a tank of total volume V = 10 m 3 , which initially contains 80 ice by volume, how long would it take to completely melt the ice? The density and latent heat of fusion of ice are 920 k g / m 3 and 3.34 × 10 5 J / k g , respectively. (b) The air outlet temperature may be regulated by adjusting the tube mass flow rate. For the tube length determined in part (a), compute and plot T m , o as a function of m ˙ for 0.005 ≤ m ˙ ≤ 0.05 k g / s . If the dwelling cooled by this system requires approximately 0.05 k g / s of air at 16 ° C , what design and operating conditions should be prescribed for the system?
The evaporator section of a heat pump is installed in a large tank of water, which is used as a heat source during the winter. As energy is extracted from the water, it begins to freeze, creating an ice/water bath at 0 ° C , which may be used for air conditioning during the summer. Consider summer cooling conditions for which air is passed through an array of copper tubes, each of inside diameter D = 50 m m , submerged in the bath. (a) If air enters each tube at a mean temperature of T m , i = 24 ° C and a flow rate of m ˙ = 0.01 k g / s , what tube length L is needed to provide an exit temperature of T m , o = 14 ° C ? With 10 tubes passing through a tank of total volume V = 10 m 3 , which initially contains 80 ice by volume, how long would it take to completely melt the ice? The density and latent heat of fusion of ice are 920 k g / m 3 and 3.34 × 10 5 J / k g , respectively. (b) The air outlet temperature may be regulated by adjusting the tube mass flow rate. For the tube length determined in part (a), compute and plot T m , o as a function of m ˙ for 0.005 ≤ m ˙ ≤ 0.05 k g / s . If the dwelling cooled by this system requires approximately 0.05 k g / s of air at 16 ° C , what design and operating conditions should be prescribed for the system?
Solution Summary: The author explains the tube length required to achieve a prescribed air outlet temperature and time to completely melt the ice.
The evaporator section of a heat pump is installed in a large tank of water, which is used as a heat source during the winter. As energy is extracted from the water, it begins to freeze, creating an ice/water bath at
0
°
C
, which may be used for air conditioning during the summer. Consider summer cooling conditions for which air is passed through an array of copper tubes, each of inside diameter
D
=
50
m
m
, submerged in the bath. (a) If air enters each tube at a mean temperature of
T
m
,
i
=
24
°
C
and a flow rate of
m
˙
=
0.01
k
g
/
s
, what tube length L is needed to provide an exit temperature of
T
m
,
o
=
14
°
C
? With 10 tubes passing through a tank of total volume
V
=
10
m
3
, which initially contains 80 ice by volume, how long would it take to completely melt the ice? The density and latent heat of fusion of ice are
920
k
g
/
m
3
and
3.34
×
10
5
J
/
k
g
, respectively. (b) The air outlet temperature may be regulated by adjusting the tube mass flow rate. For the tube length determined in part (a), compute and plot
T
m
,
o
as a function of
m
˙
for
0.005
≤
m
˙
≤
0.05
k
g
/
s
. If the dwelling cooled by this system requires approximately
0.05
k
g
/
s
of air at
16
°
C
, what design and operating conditions should be prescribed for the system?
The evaporator section of a heat pump is installed in a large tank of water, which is used as a heat source during the winter. As energy is extracted from the water, it begins to freeze, creating an ice/water bath at 0°C, which may be used for air conditioning during the summer. Consider summer cooling conditions for which air is passed through an array of copper tubes, each of inside diameter D = 59 mm, submerged in the bath.
(a) If air enters each tube at a mean temperature of Tm,i = 25°C and a flow rate of m·=0.01 kg/s, what tube length L is needed to provide an exit temperature of Tm,o = 16°C? With 10 tubes passing through a tank of total volume V = 11 m3, which initially contains 83% ice by volume, how long would it take to completely melt the ice? The density and latent heat of fusion of ice are 933 kg/m3 and hsf = 3.34 × 10^5 J/kg, respectively.
Design a hydrocooling unit that can cool fruits andvegetables from 30 to 5°C at a rate of 20,000 kg/h under thefollowing conditions:The unit will be of flood type, which will cool the productsas they are conveyed into the channel filled with water. Theproducts will be dropped into the channel filled with water atone end and be picked up at the other end. The channel canbe as wide as 3 m and as high as 90 cm. The water is to becirculated and cooled by the evaporator section of a refrigerationsystem. The refrigerant temperature inside the coils is tobe 22°C, and the water temperature is not to drop below 1°Cand not to exceed 6°C.Assuming reasonable values for the average product density,specific heat, and porosity (the fraction of air volume ina box), recommend reasonable values for (a) the water velocitythrough the channel and (b) the refrigeration capacity ofthe refrigeration system.
Saturated steam at 1 atm is condensed on the external surface of a copper tube withan outside diameter 16 mm and tube wall of thickness 0.5 mm. The tube is cooledinternally by water with a mass flow rate of 0.06 kg/s, which in turn is raised intemperature from 15 oC to 60 oC as it flows through the tube.Take the heat-transfer coefficient at the condensing side as 10.0 kW/m2K and theisobaric specific heat-capacity of water as 4180 J/kg K.i) Calculate the heat transfer rate to the cooling water.ii) Calculate the length of the tube.
Use the steam property table (Roger and Mayhew)
Fox and McDonald's Introduction to Fluid Mechanics
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Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning