Chemical Heat Transfer Quiz 8

1 / 50

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

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

4 / 50

**The steam ejector is used to___________?**

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 unit of heat transfer co-efficient is__________?**

7 / 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__________?**

8 / 50

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

9 / 50

**The thermal boundary layer at NPr > 1 ?**

10 / 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_________?**

11 / 50

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

12 / 50

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

13 / 50

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

14 / 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) ?**

15 / 50

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

16 / 50

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

17 / 50

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

18 / 50

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

19 / 50

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

20 / 50

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

21 / 50

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

22 / 50

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

23 / 50

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

24 / 50

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

25 / 50

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

26 / 50

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

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

29 / 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?**

30 / 50

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

31 / 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___________?**

32 / 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___________?**

33 / 50

**The Stefan-Boltzmann constant depends on the__________?**

34 / 50

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

35 / 50

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

36 / 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________?**

37 / 50

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

38 / 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___________?**

39 / 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 ________?**

40 / 50

**The Graetz number is concerned with the_____**

41 / 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_______?**

42 / 50

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

43 / 50

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

44 / 50

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

45 / 50

**The units of resistance to heat transfer is _______?**

46 / 50

**The unit of conductance in SI unit is________?**

47 / 50

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

48 / 50

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

49 / 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?**

50 / 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___________?**

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