R410A is a widely used refrigerant in residential liquid-to-water heat pumps. Variable speed compressors and electronic expansion valves are known to increase the heat pump performance and are becoming a common option in high efficiency heat pumps. Additionally, in order to minimize the system dimensions and the refrigerant charge, many domestic heat pumps are produced without liquid receivers. These systems are said to be critically charged as the refrigerant charge has a direct impact on the system performance.

Even though refrigerant R410A does not contribute to the depletion of the ozone layer it has a Global Warming Potential (GWP) of 1924, so its impact on global warming is significant. For this reason, various lower-GWP alternatives to R410A have been proposed in recent years. Two of them are R452B and R454B with GWP values of 675 and 466, respectively.

This paper presents an experimental study of the drop-in performance of refrigerants R452B and R454B in an R410A liquid-to-water heat pump. Experimental results for the three refrigerants are presented for the heating mode of operation at two different water temperatures in the condenser and different compressor speeds. The effect of the refrigerant charge for each case is also studied in order to identify its impact on the heat pump performance. An optimum charge that maximized the system COP could be determined for each refrigerant. This optimum charge is lower for the alternative refrigerants and it is slightly affected by the test condition and compressor speed. When compared with R410A, the lower-GWP alternatives present higher discharge temperatures, lower heating and compression powers, and similar COPs.

R410A是住宅液体水热泵中广泛使用的制冷剂。众所周知，变速压缩机和电子膨胀阀可提高热泵性能，并已成为高效热泵中的常见选择。另外，为了最小化系统尺寸和制冷剂充注量，生产了许多没有液体接收器的家用热泵。由于制冷剂充注量直接影响系统性能，因此称这些系统为临界充注量。

即使制冷剂R410A对臭氧层的消耗没有贡献，它的全球变暖潜能值（GWP）为1924，因此，它对全球变暖的影响很大。由于这个原因，近年来已经提出了R410A的各种低GWP替代方案。其中两个是R452B和R454B，其GWP值分别为675和466。

本文介绍了R410A液水热泵中R452B和R454B制冷剂的滴入性能的实验研究。给出了三种制冷剂在冷凝器中两种不同水温和不同压缩机速度下加热运行模式的实验结果。为了确定制冷剂对热泵性能的影响，还研究了每种情况下制冷剂充注的影响。可以为每种制冷剂确定使系统COP最大化的最佳充气量。替代制冷剂的最佳充量较低，并且受测试条件和压缩机速度的影响很小。与R410A相比，较低的GWP替代品具有较高的排放温度，较低的加热和压缩功率以及类似的COP。