Engineering :: Heat Engines

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71.

The work done on a compressor will be least when air is taken from

A.	Atmosphere	B.	Source of low temperature air
C.	Source of high temperature air	D.	As and where available
E.	A source at 0?C

72.

After cooler is used to

A.	Cool the air	B.	Reduce the volume of air
C.	To cause moisture and oil vapour to drop out	D.	Remove impurities from air
E.	None of the above

73.

A fan is being used under certain known conditions. If the speed of fan is doubled the air displaced by the fan

A.	Will remain the same	B.	Will be doubled
C.	Will be four times the original displacement	D.	will be either times the original displacement
E.	None of the above

74.

A fan is being used under certain conditions. If the fan speed is doubled the power requirement will be

A.	Unchanged	B.	Double of the original
C.	Four times	D.	8 times
E.	16 times

75.

A fan is being operated in an environment for which information is available. Now if the fan speed is doubled, how will the static pressure vary

A.	No change	B.	Doubled
C.	Four times	D.	Eight times
E.	Sixteen times

76.

In centrifugal pumps suction head is

A.	Vertical distance from supply level to pump centre line pump being level	B.	(A) Above less suction friction heat
C.	(A) Above less velocity heat	D.	Any of the above
E.	None of the above

77.

In a pumping installation the suction line is is 4 metre long and suction pipe diameter is 100 mm. Now if the suction pipe is replaced by a pipe combination consisting of 2 metres of 100 mm diameter pipe joined with 2 metres of 150 mm diameter pipe, the suction heat will become

A.	6 metres	B.	4 metres
C.	2 metres	D.	1 metre
E.	None of the above

78.

When steam expands without doing mechanical work, its enthalpy

A.	Increases	B.	Decreases
C.	Does not change	D.	Depends on the factors
E.	None of the above

79.

In thermodynamic analysis, a pure substance is that which

A.	consists of only a single chemical species	B.	May have a number of chemical species that the composition remains constant
C.	has no dissolved impurities	D.	behaves as perfect gas

80.

A perfect heat engine works on the Carnot cycle between 1000?C and 200?C. The efficiency of the engine will be

A.	80%	B.	60%
C.	42.80%	D.	37.20%
E.	62.80%