40 TOP Heat Transfer Online Test – Multiple Choice Questions and Answers 1. In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of activity co-efficients concentrations chemical potentials mass transfer co-efficients 2. Low thermal conductivity of heat insulating materials is due to its high specific heat dense structure high proportion of air space none of these 3. Loss of heat from untagged steam pipe to the ambient air is by radiation conduction convection all of above 4. Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator high pressure falling film long tube none of these 5. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is 0.2 0.4 0.6 0.8 6. With increase in temperature, the total emissivity of conductors increases decreases remains same decreases linearly 7. Small scale evaporation is done in a condenser heat exchanger steam jacketed kettle multiple effect evaporator 8. Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping both the tube sheets fixed both the tube sheets floating the top tube sheet fixed and the bottom tube-sheet floating the top tube sheet floating and bottom tube sheet fixed 9. At constant temperature, the thermal conductivities of gases __________ with rise in pressure increase remain unchanged may increase or decrease; depends on the pressure decrease 10. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is 0.5 2 10 100 Loading … Question 1 of 10
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