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