In the present paper, the experimental results of the use of R1234yf and R1234ze(E) as drop-in alternatives of R134a in a water-to-water heat pump are discussed. The heat pump is firstly tested with R134a, to establish the baseline performance, and, then, is tested with the two above-mentioned refrigerants considering the same compressor shaft rotational frequency and the same outlet temperatures of the secondary fluids from the evaporator and the condenser. The obtained results show that, compared to the R134a, the use of R1234yf leads to a reduction of the heating capacity and of the COP up to 9.80% and 7.39% respectively, whereas with the use of R1234ze(E) the capacity reduction achieves a maximum of 33.82% while a COP variation in the range −12.27% to +4.32% is found. A second group of tests is carried out varying the rotational frequency of the compressor shaft with the aim of matching the baseline R134a heating capacity. The results indicate an increase in the shaft rotational frequency up to 16% with R1234yf and up to 50% with R1234ze(E) which, however, leads to a maximum reduction of the heat pump COP respectively equal to 7.38% and to 18.11%.

本文讨论了在水对水热泵中使用R1234yf和R1234ze（E）作为R134a的替代产品的实验结果。首先使用R134a对热泵进行测试，以建立基准性能，然后在考虑到相同的压缩机轴旋转频率和相同的蒸发器和冷凝器二次流体出口温度的情况下，对上述两种制冷剂进行测试。 。获得的结果表明，与R134a相比，使用R1234yf导致加热容量和COP分别降低高达9.80％和7.39％，而使用R1234ze（E）时，容量降低可达到最大值为33.82％，而COP变化范围为-12.27％至+ 4.32％。为了匹配基准R134a的热容量，进行了第二组测试，更改了压缩机轴的旋转频率。结果表明，R1234yf可使轴旋转频率增加多达16％，R1234ze（E）可使轴旋转频率增加多达50％，但是这导致热泵COP的最大降低分别等于7.38％和18.11％。