Saturated flow boiling inside conventional and mini/micro channels: A new general model for frictional pressure drop using genetic programming

This study presents a general explicit model for estimating the saturated flow boiling frictional pressure drop (FPD) in conventional (macro) and mini/micro channels heat exchangers. An extensive database including 6021 experimental data samples has been gathered from 42 published sources, covering a broad range of fluids, channel diameters and operating parameters. The new model is based on the separated model suggested by Lockhart and Martinelli (1949) for two-phase flow. Thus, the two-phase multiplier, phi(2)(lo) has been estimated using the intelligent approach of genetic programming (GP). The presented model predicts the mentioned database with a reasonable value of average absolute relative deviation (AARD) of 21.34%. Moreover, 74.85% of predicted data have an error of lower than 30% of the experimental values. The entire database is compared with ten well-known two-phase pressure drop correlations for the evaluation of previous models. But all of them showed a total AARD of more than 27%. The GP model shows good accuracy for both conventional and mini/micro channels and different flow regimes, including low and high Reynolds numbers. In addition, it is applicable for estimating the boiling FPD in different operating conditions. Based on 752 additional data from 4 independent sources, the new model provides the best predictions for estimating the FPD in conventional and mini/micro channels.