HEATING A HOUSE

One of the main problems that many families have to face in winter is that of keeping their homes pleasantly warm without too much cost and effort. What are the factors that you think should be considered in designing a new house, or improving one already built? If possible, obtain information on the various heating systems and methods of insulation available.

We shall first consider methods of preventing the loss of heat, and, later, the methods of obtaining heat.

Transfer of heat

Heat can be transferred in three ways:

a) Conduction. When heat is transferred through a material, that material is said to 'conduct' heat. It is conduction of heat that causes the handle of a spoon left in a bowl of hot water to become unpleasantly hot.

Different materials conduct at different rates: metals, for example, conduct quickly while polystyrene conducts very slowly and is therefore said to be a good 'insulator'. Why do metals feel colder than polystyrene in cold weather, and hotter in hot weather?

b) Radiation. We receive heat from the sun even though there is nothing between the earth and the sun to act as a conductor: the heat is transferred by 'radiation'. We also receive radiant heat from, for instance, an open flame or electric fire.

c) Convection. If part of a fluid is warmed then that part will rise, causing a circulation in the fluid and thus a transfer of heat. Any transfer by this method is referred to as 'convection'. You must have actually seen this happening in a saucepan of hot water or in the air over a radiator or fire or a hot asphalt road. What heating and what cooling systems often rely upon convection?

<== попередня сторінка	\|	наступна сторінка ==>
Методичні вказівки	\|	Heat losses

Не знайшли потрібну інформацію? Скористайтесь пошуком google:

Генерація сторінки за: 0.005 сек.