Finned Heat exchangers designed to save energy

The current environment of high and continuously rising energy costs sees an increasing demand for heat recovery from existing processes, in a bid to reduce energy consumption. Waste streams of liquids or gases may contain sufficient energy to financially justify the installation of a purpose designed heat exchanger.

Traditionally these were made of carbon steel materials, but to reduce costs and increase the life of heat exchangers, We introduced higher specification materials, such as stainless tubing and aluminium fins.

Developing expertise with these materials opened up opportunities for expansion into general heat exchanger work, such as spray drier heat exchangers in the dairy industry and heat dumps and recuperators for solid fuel heatplants.

Finned tubing has a unique application in heat exchanger design. The transfer of heat to air is not easy. Air is an excellent insulator, and notoriously difficult to get to conduct heat. It is an oxidising medium, readily coating heat transfer surfaces with insulating deposits. It requires vigorous turbulence to absorb heat from a hot surface and distribute it amongst itself.

To overcome this limitation it is necessary to increase the surface area of the side of the heat exchanger in contact with the air. This is the so called finned tube; a fin is wound onto the outside surface of a tube in a continuous helix. This fin can take many forms, ranging from an interference fit (L and LL fin), through a grooved and swaged fixing (G fin), to a continuously welded form. The fin can be in a range of materials. Fin fixing generally makes little difference to thermal efficiency (unless it has a poor or non-continuous attachment to the tube) but places strict limits on the maximum temperature the fin can be used at.

For industrial applications Windsor uses almost exclusively an aluminium G fin. This ensures the aluminium fin will not come loose on the base tube in service, and provides a high fin efficiency (a measure of the variation in fin temperature) leading to a smaller, less costly exchanger.

Most heat exchangers are purpose engineered by Windsor for the particular application. There are important issues with construction - in particular with the stainless steel welding and the differential thermal expansion of components in the heater. Lifting, transportation and support of the heat exchanger also require careful attention.