PROBLEM 2 Refrigeration Cycle Analysis

In the refrigeration lab, a water bath is cooled by a refrigeration unit, whereas a heater is used to compensate the cooling for temperature control.

The refrigerant used is R-290 (propane), with a density of 0.5 kg/L. The glass tube for measuring refrigerant flow rate has a volume of 14 ml. Using the propane property table provided and the data collected in Table 3, answer the following questions.

Water bath temperature at 10°C

Consider an ideal refrigeration cycle

1. Draw the T-s diagram and use the two measured pressures to calculate the coefficient of performance (COP).

Consider an actual refrigeration cycle

2. Consider the expansion process is isenthalpic and no pressure loss at the condenser, calculate the entropy at the evaporator inlet. Mark state 1 to 4 on the T-s diagram.

3. Using the T-s diagrams in part 1 and 3, discuss the major differences between the actual cycle and ideal cycle.

4. Calculate the COP of the actual cycle.

5. Analyze the energy balance of the water bath and discuss whether it can be considered to be well insulated.

Water bath temperature at 5°C and 15°C

6. Calculate the COP at both temperatures using the above actual cycle analysis. Mark the measured pressures and temperatures on the T-s diagram.

7. Discuss how the COP should vary with the water bath temperature in theory and whether the measured results are consistent with the theory.