Investigation of Refrigerant Boiling in a Compact Heat Exchanger Manufactured Using Additive Manufacturing Technology

An experimental investigation was conducted to characterize refrigerant boiling in a compact shell-and-tube heat exchanger manufactured from SS316L stainless steel using selective laser melting. The exchanger incorporated horizontally oriented minichannels surrounded by a confined shell-side space, where boiling occurred on the external surfaces heated internally by water. Four refrigerants with different thermophysical properties were investigated: R1234ze(E), R1234yf, R134a, and HFE7100. Experiments were performed for heat flux densities ranging from 0.5 to 30 kW/m2 under natural circulation conditions, with measured refrigerant mass flow rates between approximately 1 and 22 kg/h. The results showed that both the overall and boiling heat transfer coefficients increased with increasing heat flux. R1234ze(E) and R1234yf provided the highest thermal performance, whereas HFE7100 exhibited the lowest heat transfer coefficients. For all tested fluids, the boiling heat transfer coefficient showed an exponential dependence on heat flux density. The experimental results were also compared with a previously developed empirical correlation, yielding a mean absolute percentage error of 12.5%, with approximately 93.4% of the data falling within a ±25% deviation band. The results demonstrate the applicability of additively manufactured compact heat exchangers for boiling heat transfer and their potential use with modern low-GWP refrigerants.