In a refrigerant-cooling system, 1.5 kg/s of refrigerant 134a flows at steady state through a coil having an inside diameter of 0.05 m. The refrigerant enters the tube as superheated vapor at 700 kPa and 70°C and leaves at 32°C and 690 kPa. You want to heat the water from of 25°C to 35°C by placing the coil inside a box and having the water enter and leave the box at a constant mass flow rate. Please answer the following: Please answer the following. a. Create a schematic that accurately describes the situation given in the problem. Include your chosen boundary and the energy interactions present across the boundary. You will select from which side the cold water enters the box; that is, closer to the inlet of the refrigerant at 70°C or closer to the exit of the refrigerant at 32°C. b. Represent the process for the refrigerant on a T-v diagram. Show the isobars corresponding to each state with their value. Include values on the axes using customary units. c. For this part you are going to sketch the temperature distribution for both fluids on a single diagram as a function of position of the fluid in the heat exchanger. To do this you will consider that that refrigerant and the water flow in counter flow. Include the temperature values for both fluids at the inlet and at the exit.
In a refrigerant-cooling system, 1.5 kg/s of refrigerant 134a flows at steady state through a coil having
an inside diameter of 0.05 m. The refrigerant enters the tube as superheated vapor at 700 kPa and 70°C
and leaves at 32°C and 690 kPa. You want to heat the water from of 25°C to 35°C by placing the coil
inside a box and having the water enter and leave the box at a constant mass flow rate. Please answer
the following:
Please answer the following.
a. Create a schematic that accurately describes the situation given in the problem. Include your
chosen boundary and the energy interactions present across the boundary. You will select from
which side the cold water enters the box; that is, closer to the inlet of the refrigerant at 70°C or
closer to the exit of the refrigerant at 32°C.
b. Represent the process for the refrigerant on a T-v diagram. Show the isobars corresponding to
each state with their value. Include values on the axes using customary units.
c. For this part you are going to sketch the temperature distribution for both fluids on a single
diagram as a function of position of the fluid in the heat exchanger. To do this you will consider
that that refrigerant and the water flow in counter flow. Include the temperature values for
both fluids at the inlet and at the exit.
d. Compute the rate at which heat is transferred to the refrigerant, in kJ/s.
e. Starting from the general energy balance equation, derive and expression to compute the mass
flow rate of water. Only use symbols and list your assumptions. You may assume that the box is
perfectly insulated.
f. Using your expression in part (e), estimate the flow rate of water you can cool, in kg/s.
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