Heat Transfer, Refrigeration and Air Conditioning Questions

• The sensible heat factor during cooling and dehumidification process is given by (where h1 = Enthalpy of air entering the cooling coil, h2 = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process)
• The optimum effective temperature for human comfort is
• Defrosting of a refrigerator may be done by stopping the compressor for a short period.
• A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser.
• For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
• In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
• The heat transfer by conduction through a thick sphere is same as through a thick cylinder.
• As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.
• Which of the following statement is wrong?
• During adiabatic saturation process on unsaturated air __________ remains constant.
• The centrifugal compressors are generally used for refrigerants that require
• A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as
• Which of the following statement is correct for ammonia as a refrigerant?
• During humidification process, __________ increases.
• Conduction is a process of heat transfer
• Sulphur dioxide is extremely toxic and non-flammable.
• A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
• The emissivity for a black body is
• Thermal conductivity of air increases with rise in temperature.
• In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in