Heat exchangers are specifically designed for the efficient transfer of heat from one fluid to another fluid over a solid surface. This transfer of heat can either take the form of absorption or dissipation of heat. The heat exchanger effectiveness is defined as the ratio of the actual heat transfer to the heat transfer attainable in an infinitely long counterflow exchanger.
Heat exchangers are typically constructed of steel, titanium, copper, bronze, stainless steel, aluminum or cast iron.
Heat Exchangers may be classified according to their flow arrangement.
- Parallel-Flow Heat Exhangers - The two fluids
enter the exchanger at the same end, and travel in parallel to one
another to the other side.
- Counterflow Heat Exchangers - In the exchanger,
the fluids enter the exchanger from opposite ends.
- Cross Flow Heat Exchangers - The fluids travel roughly perpendicular to one another through the exchanger.
Pressure drop is very important in any heat exchanger design. As the pressure drops, the viscosity and the fluids ability to transfer heat also drops. The velocity is directly proportional to the heat transfer coefficient.
Applications of Heat Exchangers
- Oil coolers
- Transmission and engine coolers
- Boiler coolers
- Waste water heat recovery
- Chilled water systems
- Ground water systems
- Condensers and evaporators in refrigeration systems
- Close approach fluid-to-fluid heat transfer