Emissivity of a white polished body in comparison to a black body is Same Higher Lower Depends upon the shape of body TRUE ANSWER : ? YOUR ANSWER : ?
In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in Counter flow Parallel flow Cross flow All of these TRUE ANSWER : ? YOUR ANSWER : ?
According to Prevost theory of heat exchange Heat transfer in most of the cases takes place by combination of conduction, convection and radiation Heat transfer by radiation requires no medium All bodies above absolute zero emit radiation It is impossible to transfer heat from low temperature source to t high temperature source TRUE ANSWER : ? YOUR ANSWER : ?
A steam pipe is to be insulated by two insulating materials put over each other. For best results Whether to put inferior OIL over pipe or the better one would depend on steam temperature Inferior insulation should be put over pipe and better one over it Both may be put in any order Better insulation should be put over pipe and better one over it TRUE ANSWER : ? YOUR ANSWER : ?
The transfer of heat by molecular collision is smallest in Liquids None of these Solids Gases TRUE ANSWER : ? YOUR ANSWER : ?
Which of the following has least value of conductivity? Glass Plastic Air Water TRUE ANSWER : ? YOUR ANSWER : ?
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a Black body Opaque body Grey body White body TRUE ANSWER : ? YOUR ANSWER : ?
The natural convection air cooled condensers are used in All of these Domestic refrigerators Room air conditioners Water coolers TRUE ANSWER : ? YOUR ANSWER : ?
The automobile radiator is a heat exchanger of Counter flow type Parallel flow type Regenerator type Cross flow type TRUE ANSWER : ? YOUR ANSWER : ?
The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) TRUE ANSWER : ? YOUR ANSWER : ?