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You Are On Multi Choice Question Bank SET 418

20901. In evaporators, lowering the feed temperature

20902. The type of liquor circulation system to be ' employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid.

20903. In case of surface condensers, a straight line is obtained on plotting __________ on an ordinary graph paper.

20904. Thermal diffusivity is the most important in heat transfer by

20905. (NGr x NPr) is called the __________ number.

20906. A dephlegmator is a

20907. A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?

20908. The separation of liquid droplets from the vapor is done by a/an __________ , in the evaporators.

20909. Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface)

20910. If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will

20911. A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.

20912. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

20913. Evaporator tubes are generally

20914. The metal in the liquid state is:?

20915. In a boiling curve, the peak heat flux is called the __________ point.

20916. Our Prime Minister announced ‘Beti Bachao,Beti Padhao Yojana’on 22 January 2015 at:

20917. h.D/K is called the __________ number.

20918. Who is the author of the book”The Country of First Boys”?

20919. Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)

20920. Heat flux, as defined in heat flow is analogous to __________ in electricity flow.

20921. The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)

20922. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.

20923. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is

20924. The purpose of providing bleed points in the evaporator is to

20925. Water always boils when its

20926. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has

20927. Which is the most suitable for cold viscous feed?

20928. Dropwise condensation is promoted on a/an __________ surface.

20929. At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the

20930. In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.

20931. is called the __________ number

20932. Nucleate boiling is promoted

20933. In forced circulation, the heating element is injected

20934. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is

20935. The equation, Nst = f/2, is the __________ analogy.

20936. Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.

20937. Rate of crystallisation does not depend upon the

20938. Stefen's block body radiation law can also be derived from __________ law.

20939. Multipass heat exchangers are used

20940. A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

20941. Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

20942. When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?

20943. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α 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

20944. A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time

20945. LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.

20946. Thermal diffusivity of a material

20947. Viscosity of gases __________ with increase in temperature.

20948. What is the emissivity of a black body ?

20949. Steam is routed through the tube in case of a __________ evaporator.

20950. Dropwise condensation of steam on cooling surface is promoted

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