Refrigeration and AC
JKSSB Junior Engineer (Mechanical) · Thermal Engineering and Refrigeration & Air-conditioning · 28 practice questions with answers and explanations: 11 Easy, 17 Medium, 0 Hard.
Sample questions
Sample Easy question 1
Relative humidity is the ratio of:
- Mass of water to mass of dry air
- Dry-bulb to wet-bulb temperature
- Vapour pressure to total pressure
- Actual vapour pressure to saturation vapour pressure at the same temperature
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Answer: D. It is expressed as a percentage.
Sample Easy question 2
A good refrigerant should have:
- a low latent heat and a high freezing point
- a high viscosity
- a high toxicity
- a high latent heat of vaporisation and a low freezing point
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Answer: D. A high latent heat gives a high refrigerating effect per kilogram.
Sample Easy question 3
The dry bulb temperature of air is the temperature measured by:
- a thermometer with a wet wick
- an ordinary thermometer exposed to the air
- a thermometer in the water
- a hydrometer
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Answer: B. It is not affected by the moisture in the air.
Sample Medium question 4
In a vapour compression cycle, the refrigerant leaves the condenser as:
- a superheated vapour
- a wet vapour at low pressure
- a saturated or sub-cooled liquid at high pressure
- a low-pressure vapour
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Answer: C. Condensation turns the hot vapour into liquid, which is then throttled.
Sample Medium question 5
The COP of a Carnot refrigerator working between 250 K and 300 K is:
- 0.2
- 5
- 1.2
- 6
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Answer: B. COP = T_L / (T_H − T_L) = 250 / 50 = 5.
Sample Medium question 6
The refrigerant R-12 is a:
- water-based fluid
- chlorofluorocarbon (CFC) that harms the ozone layer
- hydrocarbon
- natural gas
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Answer: B. CFCs such as R-12 are being phased out under the Montreal Protocol.