High-temperature heat pumps based on natural working fluids to produce district heating from industrial waste heat.

The amount of industrial waste heat produced in Europe annually corresponds to the total annual heating demand in buildings. Common barriers for utilizing this heat are the lack of required infrastructure, i.e. a district heating (DH) network, and too low temperature of the waste heat. To address the last-mentioned barrier, high-temperature heat pumps may be applied to upgrade the heat. This study evaluates the possibility of utilizing a heat pump to supply DH using industrial wastewater at 40 °C as a heat source. Different heat pump technologies based on natural refrigerants were compared at steady state operating conditions: single- and two-stage ammonia, and ammonia-water absorption-compression (hybrid) heat pumps. The highest COP as well as the lowest operating pressure were obtained with a two-stage hybrid heat pump. Moreover, the COP for hybrid heat pumps was hardly affected by an increase in the desired DH supply temperature.

欧洲每年产生的工业废热总量，与区域建筑年度总采暖需求持平。该类废热的规模化利用存在两项常见阻碍：一是缺乏必要的配套基础设施，即区域供热（district heating, DH）管网；二是废热温度过低。针对后者这一阻碍，可通过高温热泵实现废热的提质升级。本研究以40℃工业废水作为热源，评估了利用热泵为区域供热管网供能的可行性。研究在稳态运行工况下，对比了多款基于天然制冷剂的热泵技术方案：单级氨热泵、两级氨热泵，以及氨-水吸收压缩式复合热泵（hybrid）。结果显示，两级式复合热泵可实现最高的性能系数（Coefficient of Performance, COP）与最低的运行压力。此外，复合热泵的性能系数几乎不受目标区域供热供水温度提升的影响。