New heat exchanger developments from Occo Coolers Ltd

Citation

(2001), "New heat exchanger developments from Occo Coolers Ltd", Industrial Lubrication and Tribology, Vol. 53 No. 3. https://doi.org/10.1108/ilt.2001.01853cad.003

New heat exchanger developments from Occo Coolers Ltd

New heat exchanger developments from Occo Coolers Ltd

Keywords: Heat exchanger, Pumps, Temperature control

Pump and exchanger forms cooling module

Combining a pump with a heat exchanger forms the basis of a temperature control circuit. A fan blown exchanger normally performs cooling only of a fluid, whereas a liquid to liquid exchanger also offers the possibility of heating, using steam or hot water as the heat source. Occo can now offer both types of module over a wide range of sizes, the second type going by the name "Pumpex".

Pumps of various types are incorporated, e.g. centrifugal or turbine impellers for high flows and low pressure. Alternatively gear and vane pumps will pump at constant flow-rates virtually independent of the system head. Pump materials are chosen to suit all of the familiar fluids: from super-clean deionised water, through glycol, oil/water emulsions, to the various oils, mineral and synthetic (some pumps have integral pressure relief valves (prv) while other positive displacement types have the prv unit attached). Temperature control is normally provided by simple thermostat valve kits with more complex systems, using DIN standard controllers, available as required.

These pumped exchanger modules find a very wide range of application. They include, for example, the constant, reliable cooling of the working fluid, usually oil, in power transmitting systems. The Pumpex type use their exchanger as a barrier to separate the often polluted or aggressive site cooling water from a clean water system, which may be cooling expensive and high tech plant. Thus any fouling or corrosion is limited to the exchanger, which is much easier to clean, and eventually replace. Other panelled modules are produced to give full temperature control of large recirculator systems of highly deionised water.

New frontiers in exchanger design

High-pressure fluid systems in process and power engineering are always difficult to heat and cool due to the limitations of traditional heat exchangers. The new "plate and shell" concept extends the operating limits by an order of magnitude; 100 bar working pressures are now routinely possible with a new temperature ceiling of 850°C; both parameters offering step changes up from the operating limits of conventional exchangers.

The best features of these older designs are brought together by using the inherent strength of a cylindrical shell with the densely packed surfaces of a plate stack. The old established "shell and tube" and "plate, gasket and frame" have many good features, tested and proven over the last 100 years. The new design combines most of them and then adds several of its own, e.g. the plate stack, being all welded, is easily produced in virtually any metal – duplex stainless steel are popular, and titanium for marine duties.

For high temperature and pressure conditions these exchangers are usually manufactured under the strict quality regime of a pressure vessel code. However, non-coded construction is available, for more everyday duties – but still offering the benefits of compactness, performance, and material options. Maintenance is minimal due to resistance to fouling and the presence of only one seal ring – no expensive gaskets. These exchangers have already been proved over the past few years on high performance power plant and test rigs, in the refrigeration industry, and in the demanding conditions found in petro-chemical and process plant.

For further information, please contact Brian Withington at Occo Coolers, 7 Town Hall, Beaconsfield, Buckinghamshire HP9 2PP, UK. Tel: +44 1494 673458; Fax: +44 1494 677060.