Improving cooling system efficiency with pre-coolingin
By AJ Schutte, R Pelzer and EH Mathews, Centre for Research and Continuing Engineering Development (CRCED), North-West University and consultants to TEMM International and HVAC International
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Electricity+Control, March 2013 (pages 64 - 68)
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A case study was undertaken on a mine refrigeration system - on a South African mine - where the water quality was poor. Dissolved salts form crystals on the heat exchanger's film surface when the temperature of the solution is reduced. Solid particles suspended in the water compounded the situation by further clogging the fill of the pre-cooling tower.
The cooling capacity of the pre-cooling tower was greater than required and could be replaced by a lower maintennace fill. The increase in utilisation is at the cost of efficiency. Each of the eight cells' large fan was replaced by four high-speed direct drive fans with an improved efficiency and better utilisation factor. The overall system efficiency increased and resulted in an average power saving of 1 MW over a 24 hour day on average on the mine refrigeration system. The system maintained the same level of service to the mine production process.
- A typical South African deep level mine requires substantial cooling, and has a refrigeration plant on the surface where water is cooled for use in the bulk air coolers.
- Poor water quality and fans, that are not operating optimally, can reduce the cooling efficiency and result in wasted energy.
- Simply managing the efficiency by controlling water quality and repairing damaged components of the pre-cooling tower in one case study resulted in a 1 MW saving over a 24 hour period.