Chemical Heat Transfer Quiz 8

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Chemical Heat Transfer Quiz 8

1 / 50

The purpose of floating head in a heat exchanger is to__________?

2 / 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 _______?

3 / 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?

4 / 50

The sum of reflectivity and absorptivity for an opaque body is equal to______?

5 / 50

The unit of heat transfer co-efficient is__________?

6 / 50

The range of electromagnetic spectrum important in heat transfer by radiation is _______ microns?

7 / 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___________?

8 / 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________?

9 / 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___________?

10 / 50

The ratio of total radiating power to the absorptivity of the body depends upon the ______ as per Kirchoff?s law?

11 / 50

The thermal boundary layer at NPr > 1 ?

12 / 50

The value of Stefan-Boltzmann constant in SI unit is__________?

13 / 50

The statement that ?maximum wavelength of radiation is inversely proportional to the temperature? is _______ law?

14 / 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?

15 / 50

The Stefan-Boltzmann constant depends on the__________?

16 / 50

The heat flux in the nucleate boiling regimes is proportional to (where, ?T = excess temperature) ?

17 / 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__________?

18 / 50

The ratio of kinematic viscosity to thermal diffusivity is called the ________ number?

19 / 50

The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is _________?

20 / 50

The Graetz number is concerned with the_____

21 / 50

The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the_____?

22 / 50

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is_______?

23 / 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___________?

24 / 50

The purpose of providing bleed points in the evaporator is to___________?

25 / 50

The overall resistance for heat transfer through a series of flat resistance, is the ______ of the resistances?

26 / 50

The steam ejector is used to___________?

27 / 50

The purpose of providing expansion bellows in the shell of tubular exchanger is to _______?

28 / 50

The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) __________?

29 / 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) ?

30 / 50

The units of resistance to heat transfer is _______?

31 / 50

The rate of emission of radiation by a body does not depend upon the___________?

32 / 50

The heat transfer co-efficient in film type condensation is ________ that for dropwise condensation?

33 / 50

The number of kg vaporised per kg of steam fed to the evaporator is defined as_____?

34 / 50

The maximum heat transfer co-efficient from steam heating will be attained when the steam is__________?

35 / 50

The unit of heat transfer co-efficient in SI unit is______?

36 / 50

The purpose of providing a ?catchall? in the vapor line of an evaporator is to___________?

37 / 50

The separation of liquid droplets from the vapor is done by a/an ______ in the evaporators?

38 / 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 __________?

39 / 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_______?

40 / 50

The unit of conductance in SI unit is________?

41 / 50

The Fourier number (defined as a.t/L2) is used in the analysis of problem involving heat transfer by________?

42 / 50

The main function of baffles provided in a shell and tube heat exchanger is to_______?

43 / 50

The most conducive surface for dropwise condensation to occur is the ______ surface?

44 / 50

The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ______?

45 / 50

The main purpose of providing fins on heat transfer surface is to increase the__________?

46 / 50

The thickness of condensate layer in filmwise condensation depends on the___________?

47 / 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_______?

48 / 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 ________?

49 / 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_________?

50 / 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___________?

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