Optimization design of the large temperature lift/drop multi-stage vertical absorption temperature transformer based on entransy dissipation method

Abstract

In the district heating system, the AHE (Absorption Heat Exchanger) can transfer the heat of the primary network with a large temperature drop to the secondary network with a small temperature lift in a heating station. Triangular heat transfer processes exist in a traditional AHE, and limit the performance of the system. In order to eliminate the mismatched heat transfer processes, the new ATT (Absorption Temperature Transformer) is suggested, which can separate the condensation or evaporation pressure into several levels. A new method based on entransy dissipation analysis is applied to conduct an optimization design to the ATT. Simulation results show that the minimum total KA (multiplication of the heat transfer coefficient by the heat transfer area) is obtained when entransy dissipation per transferred heat is uniformly distributed in the four basic components. The flow path of the ATT is also optimized. The best different flow direction is obtained which has the lowest flow mismatched coefficient. The total KA reduction becomes not obvious when the stage number is over 3. And the total KA reduction of a 4-stage ATT reached 28.9% compared to a 1-stage AHE.