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.Management Sciences
Category: Chemical Heat Transfer
Natural convection is characterised by__________________?
A. Grashoff number
B. Peclet number
C. Reynolds number
D. Prandtl number
Finned tube heat exchangers__________________?
A. Give larger area per tube
B. Use metal fins of low thermal conductivity
C. Facilitate very large temperature drop through tube wall
D. Are used for smaller heat load
Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the____________________?
A. Maximum resistance in the series
B. Sum of all resistances
C. Average of all resistances
D. Minimum resistance presents in the series
Heat transfer by natural convection is enhanced in system with__________________?
A. High viscosity
B. High co-efficient of thermal expansion
C. Low temperature gradients
D. Low density change with temperature
The Graetz number is concerned with the___________________
A. Mass transfer between a gas and a liquid
B. Absorption with chemical reaction
C. Heat transfer in turbulent flow
D. Heat transfer in laminar flow
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
A. (COP)R = (COP)HP = 0.6
B. (COP)R = 2.5; (COP)HP = 1.5
C. (COP)R = 1.5; (COP)HP = 2.5
D. (COP)R = (COP)HP = 2.5
Colburn analogy is applicable for the value of Prandtl number from_________________?
A. 0.001 to 1
B. 0.6 to 120
C. 0.5 to 5
D. 120 to 400
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is_________________?
A. Linear
B. Hyperbolic
C. Parabolic
D. None of these
Pick out the wrong statement?
A. Bubble size increases with the dynamic viscosity of the liquid in case of nucleate pool boiling
B. Thermal conductivity of a dry material is more than that of the damp material
C. Ratio of its capacity to economy equals the steam consumption in kg/hr in an evaporator
D. Vaporisation of organic substances in evaporator mostly causes foam formation
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