Distribution optimization of circulating water in air-cooled heat exchangers for a typical indirect dry cooling system on the basis of entransy dissipation

The flow and heat transfer of air-cooled heat exchangers play important roles in the performance of indirect dry cooling systems in power plants, so it is of benefit to the design and operation of a typical indirect dry cooling system to optimize the thermo-flow characteristics of air-cooled heat exchangers. The entransy dissipation method is applied to the performance optimization of air-cooled heat exchangers in this paper. Two irreversible heat transfer processes in air-cooled heat exchangers, the heat transfer between circulating water and cooling air and the mixing of circulating water, are taken into account and analyzed by means of the entransy dissipation method. The total entransy dissipation rate, which connects the geometrical parameters of air-cooled heat exchanger sectors and the heat capacity rates of the fluids to the heat flow rate in every sector, is obtained. Based on the mathematical relation and the conditional extremum method, an optimization equation group is derived, by which the air-cooled heat exchanger with known air-side parameters is optimized, showing that the entransy dissipation based optimization approach can contribute to the distribution optimization of circulating water in air-cooled heat exchangers of a typical indirect dry cooling system.

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