Heat Transfer, Refrigeration and Air Conditioning Questions

• In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is
• The critical thickness of insulation for a sphere is
• The ratio of surface convection resistance to the internal conduction resistance is known as
• Wet bulb temperature is the temperature of air recorded by a thermometer, when
• When there is an addition of water vapour to the air of enclosed space, a gain in __________ is said to occur.
• The temperature below which a gas is always liquified, is known as critical temperature.
• The expression is used for calculating
• In aqua-ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in
• In a black body, all radiations are rejected.
• An ordinary passenger aircraft requires a cooling system of capacity.
• The specific humidity during humidification process
• Planck's law holds good for all coloured bodies.
• The reduced ambient air cooling system has
• Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)
• The thermal diffusivity for solids is generally less than those for liquids and gases.
• The by-pass factor (B. P. F.) in case of sensible heating of air is (Where td1 = Dry bulb temperature of air entering the heating coil, td2 = Dry bulb temperature of air leaving the heating coil, and td3 = Dry bulb temperature of heating coil)
• A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be
• The capacity of a domestic refrigerator is in the range of
• Carbon dioxide is
• The difference between dry bulb temperature and dew point temperature, is called