Heat Transfers

Heat transfers, which are also known as heat exchangers are devices that can transfer heat from one liquid or gas to another liquid or gas across a solid surface that never allows the liquids or gases to mix. A common example of a heat transfer is a car radiator. The process is also used widely in air conditioning, space heating, refrigeration, and chemical processing. In a car radiator the heat from engine water is pumped through the radiator as cooler air is blown through the radiator. The heat energy of the water is then transferred to the air make sure the water stays at the right temperature and keeps vehicle from overheating.

The science of studying heat transfer is called thermodynamics. The study of heat transfer is very important in the designing process of: heat pumps, boilers, chemical processes, and automobile engines. It is also used for studying the weather and climate as it is used to understand the movement of ocean currents, etc as heat always flows from a hot body to a cold one.

There are a number of laws of thermodynamics that help to explain the mechanisms of heat transfer. Heat is transferred through: space, solid objects, gases and fluids. Heat transfer mechanisms are conduction in solid materials, convection in fluids and gases and by radiation in outer space and other heated bodies. Convection can be free or forced.

There are three basic flow systems in heat transfers. In the parallel flow method both fluids flow in the same direction. In the counter flow method the fluids flow from opposite directions and in the cross flow method the fluids flow perpendicular to one another. Counter-flow heat transfers are usually considered to be the most efficient means of heat transfer, however they are easier to break than parallel-flow and cross-flow transfers and are typically more expensive to produce.

Some substances such as copper and aluminum are very good heat conductors while materials such as plastic, rubber, and ceramics, etc. are poor conductors. Bodies that are heated will expand by their coefficient of expansion. In the cases of as boilers, radiators and room heaters, etc. heat transfer is done deliberately. In other applications, such as the iron and steel manufacturing processes, heat transfer is actually a loss since money is spent in heating the steel into a molten state.


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