224) The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called

225) The transfer of heat by molecular collision is smallest in

226) During dehumidification process, the relative humidity

227) The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.

228) The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness.