51. A grey body is one whose absorptivity
(a) varies with temperature
(b) varies with wavelength of the incident ray
(c) is equal to its emissivity
(d) does not vary with temperature and. wavelength of the incident ray
(e) none of the above.
Ans: c
53. Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of
(a) 1 :1
(b) 2: 1
(c) 1 : 2
(d) 4 : 1
(e) 1 : 4.
Ans: c
55. A non-dimensional number generally associated with natural convection heat transfer is
(a) Grashoff number
(b) Nusselt number
(c) Weber number
(d) Prandtl number
(e) Reynold number.
Ans: a
56. LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is
(a) higher
(b) lower
(c) same
(d) depends on the area of heat exchanger
(e) depends on temperature conditions.
Ans: a
57. In heat exchangers, degree of approach is defined as the difference between temperatures of
(a) cold water inlet and outlet
(b) hot medium inlet and outlet
(c) hot medium outlet and cold water inlet
(d) hot medium outlet and cold water outlet
(e) none of the above.
Ans: d
58. In counter flow heat exchangers
(a) both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
(b) both the fluids at inlet are in their hottest state
(c) both the fluids .at exit are in their hottest state
(d) one fluid is in hottest state and other in coldest state at inlet
(e) any combination is possible depending on design of heat exchanger.
Ans: b
59. A steam pipe is to be insulated by two insulating materials put over each other. For best results
(a) better insulation should be put over pipe and better one over it
(b) inferior insulation should be put over pipe and better one over it
(c) both may be put in any order
(d) whether to put inferior OIL over pipe or the better one would depend on steam temperature
(e) unpredictable.
Ans: a
Read More Questions:
Heat Transfer - Mechanical MCQs Part1
Heat Transfer - Mechanical MCQs Part2
(a) varies with temperature
(b) varies with wavelength of the incident ray
(c) is equal to its emissivity
(d) does not vary with temperature and. wavelength of the incident ray
(e) none of the above.
Ans: c
53. Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of
(a) 1 :1
(b) 2: 1
(c) 1 : 2
(d) 4 : 1
(e) 1 : 4.
Ans: c
55. A non-dimensional number generally associated with natural convection heat transfer is
(a) Grashoff number
(b) Nusselt number
(c) Weber number
(d) Prandtl number
(e) Reynold number.
Ans: a
56. LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is
(a) higher
(b) lower
(c) same
(d) depends on the area of heat exchanger
(e) depends on temperature conditions.
Ans: a
57. In heat exchangers, degree of approach is defined as the difference between temperatures of
(a) cold water inlet and outlet
(b) hot medium inlet and outlet
(c) hot medium outlet and cold water inlet
(d) hot medium outlet and cold water outlet
(e) none of the above.
Ans: d
58. In counter flow heat exchangers
(a) both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
(b) both the fluids at inlet are in their hottest state
(c) both the fluids .at exit are in their hottest state
(d) one fluid is in hottest state and other in coldest state at inlet
(e) any combination is possible depending on design of heat exchanger.
Ans: b
59. A steam pipe is to be insulated by two insulating materials put over each other. For best results
(a) better insulation should be put over pipe and better one over it
(b) inferior insulation should be put over pipe and better one over it
(c) both may be put in any order
(d) whether to put inferior OIL over pipe or the better one would depend on steam temperature
(e) unpredictable.
Ans: a
Read More Questions:
Heat Transfer - Mechanical MCQs Part1
Heat Transfer - Mechanical MCQs Part2
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