Approach temperature
Heat Interface Units (BG 62/2015) was written by Reginald Brown and published by BSRIA in December 2015. It states: ‘The approach temperature is the smallest temperature difference between the primary and secondary fluids at any point within a heat exchanger. It depends on the design of the heat exchanger and the operating conditions. For a counter flow or cross flow plate heat exchanger it will usually be the difference between the primary return temperature and the secondary return temperature. Ideally for network efficiency, the approach temperature should be as small as possible, but reducing the approach temperature for a given heat transfer rate means increasing the physical size and therefore cost of the heat exchanger.’
--BSRIA
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