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61.

Slelective surfaces

A.	maximize the absorption of solar energy and emission of radiative loss	B.	manimize the absorption of solar energy and emission of radiative loss
C.	Maximize the absorption of solar energy and minimize emission of radiative loss	D.	minimize the absorption of solar energy and maximize emission of radiative loss

62.

Which of the following passes through a maximum with increase in the number of covers (glazings) used in a flat-plate solar collector?

A.	Transmissivity - absorptivity product	B.	Top loss coefficient
C.	Collector efficiency	D.	Heat loss from the top cover

63.

The directions of the incident and refracted beams of light are related to each other by

A.	Bougers law	B.	Snells law
C.	Wiens law	D.	Hottel - Whillier-Bliss equation

64.

Which of the following is not combustible?

A.	H2	B.	CO
C.	CCI4	D.	CH4

65.

The extinction coefficient for different qualities of glasses varies in the range of

A.	5-25 m-1	B.	5-25 cm-1
C.	5-25 mm-1	D.	5-25 km-1

66.

Which of the following is not a good way to improve the performance of a flat-plate solar collector?

A.	Use of a selective surface	B.	Use of an anti-reflective coating
C.	Use of three cover plate	D.	Use of an evacuated collector

67.

Overall heat transfer coefficient is proportional to the tube side volumetric flow rate raised to the poer 0.8. This holds only if the ration of the tube side film resistance to the total resistance is nearly

A.	infinite	B.	unity
C.	zero	D.	twenty

68.

When water is heated from 0?C to 10?C the volume of water

A.	increases steadily	B.	decreases steadily
C.	first increases and then decreases	D.	first decreases and then increases

69.

Which of the following is not a good way to provide freeze protection for a flat-plate collector system?

A.	Use of movable insulation to cover the collector	B.	Drain the collector when it is not operating during periods of low ambient temperatures
C.	Circulate an antifreeze solution rather than water	D.	Increase the rate of water flow through the collector by a factor of 2 leaving it on at all times

70.

A severe disadvantage of using a mixture of ethylene glycol and water as the heat-exchange fluid for a flat-plate collector is that

A.	it has an extremely low specific heat	B.	too much pumping power is required
C.	it is toxic	D.	it does not freeze at -1?C