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ISRO Mechanical Exam: Heat Transfer Quiz
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Question 1
Surface A in the figure is coated with white paint and maintained at temperature of 27 °C. It is coated directly opposite to surface B which can be directly opposite to surface B which can be considered a black body and maintained at temperature of 727 °C. Calculate the amount of heat that needs to be removed from surface A per unit area to maintain its constant temperature. (consider emissivity of the white paint = 1 and view factor =1, 
= Stefan – Boltzmann constant)
= Stefan – Boltzmann constant) Question 2
For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for ___________.
Question 3
In a heat exchanger, the hot liquid enters with a temperature of 180 °C and leaves at 160°C. The cooling fluid enters at 30 °C and leaves at 110 °C. The capacity ratio of the heat exchanger is
Question 4
An adiabatic heat exchanger is used to heat cold water at 15ºC entering at a rate of 5 kg/s by hot air at 90ºC entering also at rate of 5 kg/s. If the exit temperature of hot air is 20ºC, the exit temperature of cold water is __________. Ca= 1 and Cw=4.2.
Question 5
A radiator in a domestic heating system operates at a surface temperature of 55 °C. Assuming the radiator behaves as a black body, the rate at which it emits the radiant heat per unit area is (assume o- = 5.67 x10-8 Wi(m2K4))
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