Visit the clinic after an injury and get methylated spirit spilled on it, a cooling effect is felt as it evaporates. The body becomes cooler because the latent heat needed to convert the liquid to the vapour state is extracted from the liquid or any object in contact with it. This extraction of latent heat leads to fall in its temperature. The faster the evaporation the greater is the fall in temperature.. .png) [Wikimedia](https://commons.wikimedia.org/wiki/File:Refrigeration_PV_diagram.svg) The human body utilizes the effect of evaporation for cooling. Perspiration cools the body as sweat evaporates from the surface of the skin. As the latent heat of vaporization is extracted from the body. It is cooled in the process. Cooling by evaporation is also utilized by doctors for numbing pains from needle points. Volatile ether is usually dabbed on the skin before the body is injected with some drug. As the methylated spirit evaporates, it cools the part of the skin and nubs it so that the pain from the needle prick during an injection process is not much felt. Also in the refrigerator, the cooling effect of evaporation is utilized. .png) [Wikimedia](https://commons.wikimedia.org/wiki/File:Refrigerator_Cycle.svg) The volatile liquid is the *refrigerant*. Examples of such liquids are ammonia and ethyl chloride also known as freon. The volatile liquid is contained inside coiled copper pipes or tubes which surround the freezing chamber. As the liquid evaporates, it absorbs the necessary latent heat of vaporization from its surrounding thereby cooling the inside of the refrigerator and its contents. The vapour is removed by the pump which compresses it into a condenser attached outside the refrigerator and fixed with metal cooling fins. The compressed vapour condenses and gives out latent heat. The heat is removed by conduction into the cooling fins and thence by convection and radiation to the surrounding. The condensed vapour goes back into circulation around the freezing chamber, where it again evaporates, thus setting up a continuous circulation of liquid and vapour. .png) [Wikipedia](https://en.wikipedia.org/wiki/Direct_exchange_geothermal_heat_pump) The thermostat inside the refrigerator switches the pump motor on and off at intervals. In this way it controls the rate of vaporization and the consequent degree of cooling.