ISRO Scientist or Engineer Refrigeration & Air-Conditioning 2014
For the following questions answer them individually
In liquid metal heat transfer for a fluid flowing through a tube, Nusselt number is a function of
For infinite parallel planes with emissivities 0.4 and 0.2, the interchange view factor for a radiation from surface 1 to surface 2 is about
A chromel — alumel thermocouple of diameter 0.7mm is used to measure the temperature of a gas stream for which h= 600 W/sqm K. Acceptable reading of the temperature can be
taken after (specific heat = 400 J/kg K, Density = 8600 kg/cum)
On a hot summerday, surface of the concrete highway may reach 328 K. Suppose a stream of wateris directed on the highwayso that the surface is suddenly lowered to 308 K. Time
taken in hours to cool the concrete to 318 K to a depth of 5 cm below the surface is:(Thermal diffusivity = 1.77 E-03 m$$^2$$/h)
Hot surface at temperature 400 K having emissivity of 0.5 dissipates heat by radiation into a surrounding of 375 K.Its radiation heat transfer coefficient (W/sqm K) is
