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| 1 | |
A reversed Carnot cycle heat pump uses a hot reservoir whose temperature is Th and a cold reservoir whose temperature is Tl. The coefficient of performance of this heat pump is: |
| | A) | Tl / (Th - Tl) |
| | B) | Th / (Th - Tl) |
| | C) | (Th - Tl) / Tl |
| | D) | (Tl - Tl) / Tl |
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| 2 | |
A basic R-134a, ideal vapor-compression refrigerator operates its evaporator at -16°C and its evaporator at 1.4 MPa. How much power will the compressor require to service a 10 kW cooling load? |
| | A) | 4.03 kW |
| | B) | 5.97 kW |
| | C) | 7.32 kW |
| | D) | 10.0 kW |
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| 3 | |
A basic R-134a, ideal vapor-compression refrigerator operates its evaporator at 157 kPa and its evaporator at 1.4 MPa. What is the rate at which the condenser rejects heat when this refrigerator services a 100 kW load? |
| | A) | 80 kW |
| | B) | 103 kW |
| | C) | 120 kW |
| | D) | 141 kW |
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| 4 | |
An ideal R-134a vapor-compression heat pump operates its evaporator at 1.4 MPa and its condenser at -16°C. The coefficient of performance of this heat pump is: |
| | A) | 2.48 |
| | B) | 2.79 |
| | C) | 3.43 |
| | D) | 3.79 |
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| 5 | |
A R-134a vapor-compression refrigerator operates its evaporator at 1.4 MPa and its condenser at 157 kPa. All the cycle states and processes are ideal except for the compressor, which has an isentropic efficiency of 79%. How much power must be supplied to the compressor when this refrigerator serves a100 kW cooling load? |
| | A) | 27.3 kW |
| | B) | 34.2 kW |
| | C) | 52.0 kW |
| | D) | 100 kW |
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| 6 | |
A simple R-134a vapor-compression refrigerator system operates its evaporator at 157 kPa and the exit of the compressor at 1.4 MPa. The working fluid enters the throttle valve as a saturated liquid at 1.2 MPa as a result of pressure losses in the condenser and connection lines. What is the coefficient of performance of this device? |
| | A) | 2.64 |
| | B) | 2.93 |
| | C) | 3.26 |
| | D) | 3.69 |
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| 7 | |
An ideal R-134a, dual compressor vapor-compression refrigerator system uses a flash chamber to separate the vapor in the evaporator feed line. This system operates the evaporator at 133 kPa, the flash chamber at 400 kPa, and the condenser at 1.4 MPa. What fraction of the mass flow rate passing through the evaporator passes through the condenser? |
| | A) | 0.80 |
| | B) | 1.00 |
| | C) | 1.20 |
| | D) | 1.50 |
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| 8 | |
An ideal R-134a, dual compressor vapor-compression refrigerator system uses a flash chamber to separate the vapor in the evaporator feed line. This system operates the evaporator at 133 kPa, the flash chamber at 400 kPa, and the condenser at 1.4 MPa. What is the coefficient of performance of this device? |
| | A) | 1.87 |
| | B) | 2.63 |
| | C) | 2.95 |
| | D) | 3.17 |
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| 9 | |
A simple, ideal reversible Brayton cycle uses air as the working fluid and has a pressure ratio of 6. What is the refrigerator COP of this cycle when the temperature at the compressor entrance is -13°C and that at the turbine entrance is 37°C? |
| | A) | 0.33 |
| | B) | 0.72 |
| | C) | 1.48 |
| | D) | 1.97 |
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| 10 | |
The major performance gain of an absorption refrigeration system is: |
| | A) | Replacing a vapor compressor with a liquid pump |
| | B) | The use of a regenerator between the generator and absorber |
| | C) | Heating of the generator with an external heat source |
| | D) | Cooling of the absorber with an external energy sink |
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