The space between the two walls of a thermos flask is evacuated because vacuum i

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Question
The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.
Options
A. good
B. bad

Correct Answer

bad

Heat Transfer, Refrigeration and Air Conditioning problems

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1. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called
Options
A. humidity ratio
B. relative humidity
C. absolute humidity
D. degree of saturation

2. The cooling system used for supersonic aircrafts and rockets is
Options
A. simple air cooling system
B. boot-strap air cooling system
C. reduced ambient air cooling system
D. regenerative air cooling system

3. Which of the following statement is correct?
Options
A. In vapour absorption refrigerator, the compression of refrigerent is avoided.
B. Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
C. In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.
D. all of the above

7. The reciprocating refrigerant compressors are very suitable for
Options
A. small displacements and low condensing pressures
B. large displacements and high condensing pressures
C. small displacements and high condensing pressures
D. large displacements and low condensing pressures

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