Evaluation of R513A as an environmentally friendly alternative to R134a in spray cooling for laser surgery: Heat transfer performance and optimization

Spray cooling plays a pivotal role in mitigating thermal injuries to the epidermis during laser surgery. However, the widespread use of R134a, a refrigerant with a high global warming potential (GWP) of 1300, poses significant environmental concerns. In this study, R513A, a more environmental-friendly cryogen with a GWP of 573, is used to investigate the feasibility of replacing R134a and the effects of spray height, spurt duration, nozzle orifice diameter, and spray pressure on R513A spray cooling through a self-built open-loop spray system. Experimental results demonstrate that R513A exhibits superior cooling performance, achieving a minimum surface temperature (T_min) 12 °C lower and a maximum heat flux (q_max) 27.5 % higher than R134a. Additionally, R513A offers a broader optimal spray height range (30–50 mm) in which T_min is 4 °C and 13 °C lower than those at 20 mm and 10 mm, respectively. q_max in this range is 10 % and 16 % higher than those at 20 mm and 10 mm, respectively. While extending the spurt duration consumes more cryogen and prolongs the liquid film lifetime, the differences in T_min and q_max are less than 4 °C and 10 kW/m². With the nozzle orifice increasing from 0.6 mm to 1.0 mm, T_min remains approximately −42 °C but q_max gradually increases by 6 kW/m². Macroscopic analysis reveals that higher spray pressure induces a more dispersive spray, though this does not significantly improve cooling efficiency. To advance the understanding of R513A spray cooling dynamics, a dimensionless correlation was developed to predict the dynamic heat transfer coefficient across diverse conditions. This study not only highlights the potential of R513A as a sustainable alternative but also provides critical insights into optimizing spray cooling parameters for enhanced thermal management in laser surgery.