Flow boiling heat transfer of R1234ze(E) in a horizontal mini-channel at medium and high saturation temperatures

• Published in: International journal of heat and mass transfer 2024-07, Vol.226, p.125495, Article 125495
• Main Authors: Bediako, Ernest Gyan, Rullière, Romuald, Marchetto, Daniel Borba, Dančová, Petra, Revellin, Rémi, Vít, Tomáš
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Flow boiling; Flow patterns; Heat transfer; High saturation temperature; R1234ze(E)
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2024.125495

•Flow boiling heat transfer characteristics of R1234ze(E) (a low global warming potential (GWP) refrigerant) at moderate and high saturation temperatures is investigated.•Heat transfer characteristics and flow pattern visualization through high-speed camera were investigated for saturation temperatures ranging from 60 to 95 °C, corresponding to reduced pressures from 0.35 to 0.75.•Pre-dryout data measured were compared against different prediction methods developed under different theories.•Saturation temperature has a significant effect on heat transfer coefficient and the nucleate boiling dominates the heat transfer.•The higher the saturation temperature, the earlier the vapor quality at which dryout incipience occurs. This study reports experimental results of flow boiling heat transfer characteristics of R1234ze(E) (a low global warming potential refrigerant) at moderate and high saturation temperatures. The study was performed in a single horizontal circular smooth tube of 2.07 mm internal diameter. Heat transfer characteristics and flow pattern visualization through high-speed camera were investigated for saturation temperatures ranging from 60 to 95 °C, corresponding to reduced pressures from 0.35 to 0.75, mass velocities from 300 to 500 kg/m2s, heat fluxes from 30 to 50 kW/m2 and vapor qualities from 0 to 1. The pre-dryout data (214 data points) measured were compared against different prediction methods from the literature developed under different theories. The study revealed that the saturation temperature has a significant effect on heat transfer coefficient whereas the mass velocity presented a less pronounced or negligible effect. Furthermore, the heat transfer coefficient was observed to decrease slightly to a minimum in the low vapor quality region and then levels off or increases slightly with increasing vapor quality until dryout occurs. As a result, nucleate boiling was observed to be the dominant mechanism controlling the heat transfer. It was observed that the higher the saturation temperature, the earlier the vapor quality at which dryout incipience occurs. Considering the 214 pre-dryout data points analyzed, the methods proposed by Kew and Cornwell (1997), Lazarek and Black (1982) and Choi et al. (2007) were the most accurate, predicting the entire pre-dryout database with mean absolute errors (MAEs) of 13.7%, 13.9 % and 14.4 %, respectively.