20851. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface tempeature follows __________ law.
20852. Intermittant tube cleaning is possible to be done in case of a __________ evaporator.
20853. X-rays cannot penetrate through a sheet of?
20854. Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is
20855. 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
20856. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about
20857. Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?
20858. The Battle of Plassey was in the year:?
20859. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?
20860. Fourier's law of heat conduction applies to __________ surfaces.
20861. __________ chart is known as transient heat conduction chart.
20862. Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?
20863. Which of the following has the minimum thermal conductivity ?
20864. In a heat exchanger, one transfer unit means
20865. For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then
20866. He was born in His real name was Karattu Govinda Menon.He founded the Anandamatham.Who is he?
20867. For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
20868. Circulation pump is located below the evaporater to
20869. The statement that "maximum wavelength of radiation is inversly proportional to the temperature" is __________ law.
20870. Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low
20871. At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below :
The thermal conductivity of material I
20872. Duhring rule is important in solving problems on
20873. In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell)
20874. Multiple effect evaporation is generally recommended, when the
20875. 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.
20876. __________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side.
20877. In which mode of heat transfer, the Biot number is important ?
20878. __________ paint has the minimum absorption co-efficient.
20879. Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
20880. 1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is
20881. Which is the most suitable for the con-certration of highly concentrated solution?
20882. Unsteady state heat conduction occurs, when
20883. What is the absorptivity of a black body ?
20884. Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called
20885. Baffle spacing
20886. Boiling point elevation of a solution of NaOH
20887. The advantage of backward feed multiple effect evaporators over forward feed units is that
20888. Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface ?
20889. Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ?
20890. Thermal conductivities of most of the liquids __________ with rise in temperature.
20891. A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is
20892. The purpose of floating head in a heat exchanger is to
20893. 1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be
20894. Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the
20895. Double pipe heat exchangers are preferably useful, when
20896. Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.
20897. The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as
20898. If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
20899. Prandtl and Reynold's analogies are identical for Prandtl number value of
20900. 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