Chemical Heat Transfer Quiz 9
1 / 50
Unsteady state heat conduction occurs, when________?
2 / 50
Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is___________?
3 / 50
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is ________?
4 / 50
Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is__________?
5 / 50
Tube pitch is the ________ of tube diameters and the clearances?
6 / 50
Which of the following has maximum thermal conductivity ?
7 / 50
What is the geometric mean of two heat transfer areas A1 and A2 ?
8 / 50
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as _____ boiling?
9 / 50
Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids ?
10 / 50
When vaporisation takes place directly at the heating surface, it is called_________?
11 / 50
Thermal diffusivity is given by___________?
12 / 50
Vacuum is generally maintained in the vapour space of an evaporator mainly to___________?
13 / 50
Which has the lowest Prandtl number ?
14 / 50
What is the unit of thermal conductivity ?
15 / 50
What is the steam economy in case of a single effect evaporator system ?
16 / 50
Thermal conductivities of most of the liquids ________ with rise in temperature?
17 / 50
Use of transverse baffles in a shell and tube heat exchanger is done to increase the_____?
18 / 50
Which area is used in case of heat flow by conduction through a cylinder ?
19 / 50
Trap is used to remove _________ from steam pipe lines?
20 / 50
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
21 / 50
What is the emissivity of a black body ?
22 / 50
What is the thermal conductivity of a perfect heat insulator ?
23 / 50
When warm and cold liquids are mixed, the heat transfer is mainly by________?
24 / 50
View factor is important in heat transfer by_______?
25 / 50
Vent pipes are provided in a condenser to _________?
26 / 50
Value of Prandtl number for water ranges from__________?
27 / 50
Tube expansion allowances exist in ______ heat exchanger?
28 / 50
Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100?C and the inside heat transfer coefficient is ?3k/l?. If the wall temperature on the outside is held at 25?C, what is the inside wall temperature in degree centigrade ?
29 / 50
Water is normally used as a coolant in the heat exchange equipments mainly because of its_____?
30 / 50
Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. ?C respectively are joined together. The temperature outside of A and C are 30?C and 100?C respectively. The interface between B and C will be at a temperature of _____ ?C?
31 / 50
Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is _________ law?
32 / 50
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
33 / 50
Thermal diffusivity of a material ___________?
34 / 50
When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is ________?
35 / 50
Vibrations in the tubes of a shell and tube heat exchanger is induced due to the __________?
36 / 50
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
37 / 50
Viscosity of gases _______ with increase in temperature?
38 / 50
Thermal conductivity of a gas at low density, ___________ with increase in temperature ?
39 / 50
Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping__________?
40 / 50
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?
41 / 50
Thermal conductivity of a conducting solid material depends upon its________?
42 / 50
Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500?C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for__________?
43 / 50
What is the absorptivity of a black body?
44 / 50
What is Nusselt number ?
45 / 50
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ?
46 / 50
What is the logarithmic mean of r1 and r2 ?
47 / 50
Which is the most suitable for the concert-ration of highly concentrated solution ?
48 / 50
Which is the most suitable for the concentration of foamy & frothy liquors ?
49 / 50
Thermal diffusivity is the most important in heat transfer by___________?
50 / 50
Viscous & heat sensitive liquids are concentrated in ______ evaporators?
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