Effective heat transfer from a high-temperature surface is a crucial consideration across various domains, including electronic cooling, cooling of dies in the forging industry, and the quenching of metal alloys in material processing industries. In numerous instances, the extraction of heat is achieved through various techniques such as jet impingement cooling, and free or forced convection cooling, resulting in heat transfer coefficients ranging from 0.0057 to 5.7 W∕cm2K. However, to achieve higher rates of heat removal, alternative approaches like spray cooling become necessary, where the heat transfer coefficient falls within the range of 5.7 to 57 W∕cm2K. Remarkably elevated heat transfer rates, reaching several orders of magnitude higher (1000 to 5000 W∕cm2K), can be attained when the liquid undergoes a phase change to vapor upon impact, increasing the substantial latent heat of vaporization.

So far, the application of spray cooling, especially in the phase change regime, has predominantly been based on empirical correlations. These correlations, for the most part, lack universality and exhibit a notable dependence on specific experimental conditions. In the present study, we developed a physics-based model that is highly non-empirical in nature to calculate the total amount of heat transfer from the heated surface by the spray in various boiling regimes.

Although the study has a broad scope, it stems from a specific application, guiding operational parameter selection for computational illustration. The main focus is not just achieving high cooling rates for heated tubes but also ensuring a substantial vaporization rate of the impinging fluid, aligning with high heat transfer goals. The example concerns ORC system evaporators in waste heat recovery, where surface temperatures are typically below 500°C. By replacing the traditional Rankine cycle's steam with low-boiling refrigerants like R134a or R152a, efficient operation at low source temperatures is achieved. Current ORC designs, using conventional shell and tube heat exchangers, incur higher costs due to the small range of temperature differences between tube surfaces and working fluid. Exploring spray cooling as an alternative in ORC evaporator design is seen as a good potential for a cost-effective solution.