Two-phase computational modeling of evaporative film boiling in plate heat exchangers with offset-strip fins

To date, computational simulation on compact heat exchangers has been limited to either liquid-to-liquid single-phase flows or two-phase flow boiling across only one single plate despite the fact that heat exchangers are an indispensable part of any effective active thermal management solution. Here, the transient evaporation rate and liquid-gas maldistribution across a complete stack of three-dimensional cross-flow plate heat exchangers with offset-strip fins in between have been demonstrated. With maldistribution being a known implication of high mass flow rates across plate-fin heat exchangers (PFHXs), our simulations show that maldistribution at lower mass flow rates is primarily implicated by unequal distribution of liquid into each plate through the inlet tube or non-uniform distribution of liquid across the plate-fin, which highlights that the design and optimization of PFHXs require accurate simulation tools. Experiments were conducted on PFHXs within an environmental chamber with controllable conditions, followed by simulations across thermohydraulic parameters including mass flow rates, inlet gas quality and temperature, etc. Computational and experimental results were found to be in good agreement given the intricate complexity of two-phase liquid- gas flows with evaporation phase-change. According to the results, the overall heat transfer and effectiveness of the PFHX are strong functions of mass flow rate ((m) over dot(T)) and inlet temperature of the two-phase stream (T-t,T-i). The maximum heat transfer is achieved at (m) over dot(T) = 150 kg/h and T-t,T-i = 18 degrees C while an optimal effectiveness as high as 0.78 is achievable with (m) over dot(T) = 100 kg/h and T-t,T-i = 17.6 degrees C.