Two-stage dew-point evaporative cooler: A comprehensive study on thermodynamic performance and global climate applicability

Research on energy-efficient cooling has increasingly focused on dew-point evaporative technology. This study systematically assesses the performance of a recently developed two-stage dew-point evaporative cooler (DPEC) using second-law thermodynamics referenced to the ambient saturation state. Unlike a conventional single-stage M-cycle cooler, the studied two-stage DPEC handles the cooling load in two distinct indirect evaporative stages within a single compact four-fluid-flow heat and mass exchanger. The first stage deals with the major cooling load using ambient working air, while the second stage achieves sub-wet-bulb temperatures by utilizing a small fraction of product air. Comparative analyses demonstrate that the two-stage DPEC can preserve up to 90% of process air, resulting in 36% higher cooling capacity and 25% higher coefficient of performance (COP) than the conventional crossflow M-cycle cooler under identical conditions. Exergy analysis reveals that the two-stage DPEC attains a superior exergy efficiency of 70–74%, attributed to the functional combination of the two stages. The first stage is a high-capacity cooling process but is highly irreversible; in contrast, the second stage is a precision cooling process with low irreversibility. Parametric studies identified an optimal operating regime with a product air recirculation ratio of 10–20%. Furthermore, global climate simulations show that the cooler excels in hot and dry conditions, achieving a COP of up to 160 in Las Vegas. This work positions the two-stage DPEC as a thermodynamically efficient and globally adaptable technology, offering a significant advancement for low-energy buildings.