81. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because
82. 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
83. A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires
84. Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.
85. A hot body will radiate heat most rapidly, if its surface is
86. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.
87. At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical?
88. Peclet number (Pe) is given by
89. Pick out the correct equation.
90. Kirchoff s law applies to __________ radiation.
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