Heat pumps are gaining interest to replace fossil fuel burners with the increase of the share of renewable sources in the electricity generation mix. Moreover, low global warming potential (GWP) alternatives offer a more environmentally friendly option as refrigerants. HFO-1234ze(E) and its non-flammable mixture R-515B are experimentally investigated for the first time to replace HFC-134a in heat pump water heaters (HPWH) and moderately high temperature heat pumps (MHTHP). Tests are performed in a test rig equipped with a variable frequency compressor at evaporating temperatures of 7.5, 15 and 22.5 °C and condensing temperatures from 55 to 85 °C (65 experimental tests). HFC-134a outperforms both alternatives in heating capacity (approx. 26% higher) due to the higher mass flow rate and heating effect. However, this effect is compensated by, on average, 25% lower compressor power consumption. Therefore, the coefficient of performance (COP) is comparable or slightly higher (up to 5%) for HFO-1234ze(E) and R-515B. Considering the positive results in COP and the reduced GWP, both options decrease HFC-134a MHTHP equivalent carbon emissions down to 28%. Besides, given the 20 K lower discharge temperature reached by the alternatives, the compressor operating map can be significantly extended. Finally, it is demonstrated that R-515B is a suitable non-flammable alternative to HFO-1234ze(E) that keep energetic and environmental benefits while offers a safer system operation.

随着可再生能源在发电组合中所占份额的增加，热泵越来越有兴趣取代化石燃料燃烧器。此外，低全球变暖潜能值 (GWP) 替代品作为制冷剂提供了更环保的选择。首次对 HFO-1234ze(E) 及其不可燃混合物 R-515B 进行了实验研究，以取代 HFC-134a 在热泵热水器 (HPWH) 和中高温热泵 (MHTHP) 中的应用。测试在配备变频压缩机的测试台中进行，蒸发温度为 7.5、15 和 22.5 °C，冷凝温度为 55 至 85 °C（65 次实验测试）。由于更高的质量流量和加热效果，HFC-134a 在加热能力方面优于这两种替代品（高出约 26%）。然而，这种影响被补偿，平均而言，压缩机功耗降低 25%。因此，HFO-1234ze(E) 和 R-515B 的性能系数 (COP) 相当或略高（高达 5%）。考虑到 COP 和 GWP 降低的积极结果，两种选择都将 HFC-134a MHTHP 等效碳排放量降低至 28%。此外，鉴于替代方案达到的排放温度低 20 K，压缩机运行图可以显着扩展。最后，证明 R-515B 是 HFO-1234ze(E) 的合适的不易燃替代品，可保持能量和环境效益，同时提供更安全的系统操作。考虑到 COP 和 GWP 降低的积极结果，两种选择都将 HFC-134a MHTHP 等效碳排放量降低至 28%。此外，鉴于替代方案达到的排放温度低 20 K，压缩机运行图可以显着扩展。最后，证明 R-515B 是 HFO-1234ze(E) 的合适的不易燃替代品，可保持能量和环境效益，同时提供更安全的系统操作。考虑到 COP 和 GWP 降低的积极结果，两种选择都将 HFC-134a MHTHP 等效碳排放量降低至 28%。此外，鉴于替代方案达到的排放温度低 20 K，压缩机运行图可以显着扩展。最后，证明 R-515B 是 HFO-1234ze(E) 的合适的不易燃替代品，可保持能量和环境效益，同时提供更安全的系统操作。