A large temperature difference absorption heat pump system with multi-step heat exchangers for district heating applications

초록

This study designed, simulated, and experimentally validated a large-temperature-difference absorption heat system intended to replace the conventional plate heat exchangers in district heating networks. The system operated within a concentration range of 0.47–0.60, as determined under external fluid conditions. By applying a multi-step configuration to the absorption system with hot water of 115 °C from the CHP, it is possible to achieve a return water temperature of 32 °C. This approach can reliably maintain a temperature difference (ΔT) of about 83 °C, achieving cycle effectiveness values from 1.04 to 1.33. Compared to a single-step system, the multi-step system provided the same 900 kW heating capacity with a UA value reduced by 50 %. Experimental validation confirmed the feasibility of the multi-step heat exchangers, and a flow coefficient correlation provided design criteria for the intermediate distributor. Economic analysis revealed that, when implementing the system in new urban district heating installations, cost savings of USD 2.24 million could be achieved. For the existing infrastructures with round-trip heat transport distances over 1.1 km, the absorption heat pump system proved advantageous over plate heat exchangers. Although initial installation costs are higher, the system's reduced operational expenses resulted in a break-even point after 11.3 years. © 2025 Elsevier Ltd

키워드