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The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as______________?
Related MCQs
Heat transfer occurs by natural convection because change in temperature causes difference in__________?
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is__________?
The ratio of momentum diffusivity to thermal diffusivity is the __________ number?
What is the thermal conductivity of a perfect heat insulator ?
The value of Stefan-Boltzmann constant in SI unit is__________?
A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is __________?
Air is best heated with steam in a heat exchanger of__________?
Which is the most suitable for the concentration of foamy & frothy liquors ?
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?
Boiling point elevation of an ideal solution__________?
The main function of baffles provided in a shell and tube heat exchanger is to__________?
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C?
The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoff‟s law?
For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature) ?
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about__________?
Intermittent tube cleaning is possible to be done in case of a __________ evaporator?
In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient__________?
In evaporators, lowering the feed temperature__________?
Shell side pressure drop in a shell and tube heat exchanger does not depend upon the__________?
The most conducive surface for dropwise condensation to occur is the __________ surface?
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be__________?
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
Analogy between mass and heat transfer is not applicable in case of__________?
An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is__________?
Steady state one dimensional heat flow by conduction as given by Fourier’s low does not assume that__________?
Heat transfer co-efficient (h1) for liquids increases with__________?
Multiple effect evaporators ar used to__________?
In natural convection heat transfer, the correlating parameter is the__________?
Correction is applied to LMTD for __________ flow?
Increasing the liquor level in the evaporator results in the__________?
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) ?
Double pipe heat exchangers are used__________?
A body is called grey if the monochromatic emissivity of the body is__________?
While the total emissivity of a perfect black body is unity, the same for a real body is__________?
Crystal size in a continuous crystalliser depends upon the__________?
Boiling of milk in an open vessel is an example of __________ boiling?
Black liquor generated during paper manufacture is concentrated in a__________?
What is Nusselt number ?
In the equation Q = UAΔt; Δt is__________?
For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in__________?
Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately ?
Graetz number is given by__________?
Reynold’s analogy states that__________?
Which of the following has the minimum thermal conductivity ?
For an ideal black body__________?
For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator?
Leidenfrost point is a term concerned with the__________?
Which of the following is not used as a medium for high temperature heating ?
The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8?
In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred__________?
A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is__________?
The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as______________?
A. (ΔT)1/4
B. (ΔT)1/2
C. (ΔT)5/4
D. (ΔT)3/4
Correct Answer:
(ΔT)3/4
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Last Updated:
March 03, 2019