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