Heat Transfer MCQs | Heat Transfer Short Questions and Answers
Questions
41
Absorptivity of a body will be equal to its emissivity
Answer: when system is under thermal equi-librium
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43
A grey body is one whose absorptivity
Answer: does not vary with temperature and wave length of the incident ray
44
The time constant of a thermocouple is
Answer: the time taken to attain 63.2% of the value of initial temperature difference
45
The concept of overall coefficient of heat transfer is used in heat transfer problems of
Answer: conduction and comte_ction
46
In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by
Answer: Planck’s constant
47
Thermal Conductivity Of Glass-Wool Varies From Sample To Sample Because Of Variation In
Answer: All Of The Above
48
Moisture would find its way into insulation by vapour pressure unless it is prevented by
Answer: a vapour seal
50
Thermal diffusivity of a substance is .
Answer: proportional of thermal conductivity
52
Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called
Answer: thermal conductivity
54
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
Answer: 1 : 2
55
In heat exchangers, degree of approach is defined as the difference between temperatures of
Answer: hot medium outlet and cold water outlet
56
According of Kirchhoff’s law,
Answer: ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body.
57
According to Kirchoff’s law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a
Answer: black body
58
The concept of overall coefficient of heat transfer is used in case of heat transfer by
Answer: conduction and convection
60
Log mean temperature difference in case of counter flow compared to parallel flow will be
Answer: more
