Heat Transfer, Refrigeration and Air Conditioning Questions

• The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called
• During dehumidification process, the relative humidity
• The evaporator changes the low pressure liquid refrigerant from the expansion valve into
• When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a
• The mass of water vapour present in __________ is called absolute humidity.
• During sub-cooling, sensible heat from a liquid refrigerant is removed.
• The emissivity of a polished silver body is __________ as compared to black body.
• A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.
• The wet bulb temperature during sensible cooling of air
• The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to
• In absorption vapour systems, the refrigerant widely used is R-12.
• In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
• The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.
• The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The by-pass factor of the heating coil is
• Prandtl number (PN) is given by PN = μ.cp/k.
• The transfer of heat by molecular collision is smallest in
• A composite slab has two layers of different materials with thermal conductivities k1 and k2. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be
• The wet bulb depression indicates __________ humidity of the air.
• If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called
• In case ofsensible cooling of air, the coil efficiency is given by