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You Are On Multi Choice Question Bank SET 420

21001. With increase in temperature, the thermal conductivity of a gas





21002. A __________ evaporator employs an annular downtake.





21003. Radiation heat losses from satisfactorily insulated high pressure boilar may be about __________ percent.





21004. In natural convection heat transfer, the correlating parameter is the





21005. Boiling of milk in an open vessel is an example of __________ boiling.





21006. Who won the Sree Chithira Tirunal National Award-2015?





21007. Mode of heat transfer involved in the cooling of air cooled internal combustion engine is





21008. Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume that





21009. The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in °C is





21010. In a shell and tube heat exchanger, the shell side fluid velocity can not be changed by changing the





21011. To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is





21012. Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by This is valid for the value of NRe equal to





21013. Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C.





21014. Correction is applied to LMTD for __________ flow.





21015. If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is





21016. One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to




21017. For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone.





21018. The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is





21019. Heat exchangers operating, when the asymptotic range is reached,





21020. In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell)





21021. In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used to calculate the heat transfer rate.





21022. In a gas-liquid shell and tube heat exchanger, the





21023. Which is the most suitable for the concentration of foamy & frothy liquors ?





21024. Boiling point elevation of an ideal solution





21025. The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the





21026. Which of the following has the lowest overall heat transfer co-efficient ?





21027. Which of the following has the minimum absorptivity ?





21028. A black body when hot, emits heat radiation of __________ wavelengths.





21029. A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when





21030. Vibrations in the tubes of a shell and tube heat exchanger is induced due to the





21031. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is





21032. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is





21033. Sensible heat of hot industrial flue gases can not be recovered by a/an





21034. The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface)





21035. Radiator of an automobile engine is a __________ type of heat exchanger.





21036. In pipe flow, heat is transferred from hot wall to the liquid by





21037. The value of Stefan-Boltazman constant in SI unit is





21038. The unit of heat transfer co-efficient is





21039. For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of





21040. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is





21041. 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





21042. Low thermal conductivity of heat insulating materials is due to its





21043. The most conducive surface for dropwise condensation to occur is the __________ surface.





21044. In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of





21045. Calburn analogy is applicable for the value of Prandtl number from





21046. Pick out the correct equation.





21047. Multiple effect evaporators ar used to





21048. Small scale evaporation is done in a





21049. Heat exchanger tubes are never made of





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