Chemical Heat Transfer Quiz 8
1 / 50
The main purpose of providing fins on heat transfer surface is to increase the__________?
2 / 50
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is _________?
3 / 50
The unit of conductance in SI unit is________?
4 / 50
The interchange factor for radiation heat transfer from surface ?x? to surface ?y? in case of an infinite parallel planes with emissivities ?x & ?y is given by________?
5 / 50
The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (?T) between wall and outside bulk. The proportionality is given as_______?
6 / 50
The ratio of total radiating power to the absorptivity of the body depends upon the ______ as per Kirchoff?s law?
7 / 50
The overall resistance for heat transfer through a series of flat resistance, is the ______ of the resistances?
8 / 50
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 ________?
9 / 50
The most conducive surface for dropwise condensation to occur is the ______ surface?
10 / 50
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the_____?
11 / 50
The maximum heat transfer co-efficient from steam heating will be attained when the steam is__________?
12 / 50
The steam ejector is used to___________?
13 / 50
The radiation heat flux from a heating element at a temperature of 800?C, in a furnace maintained at 300?C is 8 kW/m2. The flux, when the element temperature is increased to 1000?C for the same furnace temperature is_______?
14 / 50
The statement that ?maximum wavelength of radiation is inversely proportional to the temperature? is _______ law?
15 / 50
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?
16 / 50
The units of resistance to heat transfer is _______?
17 / 50
The type of liquor circulation system to be ? employed in evaporators (viz. natural or forced circulation) is determined mainly by the _______ of the liquid?
18 / 50
The Fourier number (defined as a.t/L2) is used in the analysis of problem involving heat transfer by________?
19 / 50
The value of Stefan-Boltzmann constant in SI unit is__________?
20 / 50
The purpose of providing expansion bellows in the shell of tubular exchanger is to _______?
21 / 50
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is___________?
22 / 50
The ratio of kinematic viscosity to thermal diffusivity is called the ________ number?
23 / 50
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of ?n? is exactly 4 for___________?
24 / 50
The heat transfer co-efficient in film type condensation is ________ that for dropwise condensation?
25 / 50
The thickness of condensate layer in filmwise condensation depends on the___________?
26 / 50
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) ?
27 / 50
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu ? Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as __________?
28 / 50
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _______?
29 / 50
The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in ?K). The units of ?a? in SI system will be_________?
30 / 50
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is_______?
31 / 50
The unit of heat transfer co-efficient is__________?
32 / 50
The purpose of floating head in a heat exchanger is to__________?
33 / 50
The thermal boundary layer at NPr > 1 ?
34 / 50
The purpose of providing a ?catchall? in the vapor line of an evaporator is to___________?
35 / 50
The unit of heat transfer co-efficient in SI unit is______?
36 / 50
The main function of baffles provided in a shell and tube heat exchanger is to_______?
37 / 50
The sum of reflectivity and absorptivity for an opaque body is equal to______?
38 / 50
The Graetz number is concerned with the_____
39 / 50
The Stefan-Boltzmann constant depends on the__________?
40 / 50
The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ______?
41 / 50
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) __________?
42 / 50
The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50?C in industrial practice mainly to avoid__________?
43 / 50
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by___________?
44 / 50
The heat flux in the nucleate boiling regimes is proportional to (where, ?T = excess temperature) ?
45 / 50
The rate of heat transfer through a pipe wall is given by, q = 2? k (Ti ? T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by___________?
46 / 50
The separation of liquid droplets from the vapor is done by a/an ______ in the evaporators?
47 / 50
The purpose of providing bleed points in the evaporator is to___________?
48 / 50
The number of kg vaporised per kg of steam fed to the evaporator is defined as_____?
49 / 50
The range of electromagnetic spectrum important in heat transfer by radiation is _______ microns?
50 / 50
The rate of emission of radiation by a body does not depend upon the___________?
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