217) For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is

218) In case ofsensible cooling of air, the coil efficiency is given by

219) The mass of water vapour present in 1 kg of dry air, is called humidity ratio.

220) In a vapour compression refrigeration system, a throttle valve is used in place of an expander because

221) The unit of overall coefficient of heat transfer is