Breaking the limits of ambient air conditions in evaporative cooling with vacuum-assisted hollow fiber membrane technology

Conventional direct evaporative cooling systems suffer from persistent issues like air–water cross-contamination, mold growth, and scaling of paddings. Moreover, their widespread application in humid climates is hindered by ambient air conditions. This research presents a promising solution in the form of a vacuum-assisted hollow fiber membrane-based evaporative water cooler (VMEWC). It shifts from relying on air state to vacuum pressure for cold water production. A numerical model was established to reflect the coupled heat and mass transfer characteristics, employing Knudsen diffusion to describe water vapor migration within membrane pores. Experimental tests were performed on the constructed VMEWC system, revealing strong alignment between simulation and measured data, with a 2.2 % error in outlet water temperature predictions. Numerical studies explored the effects of six parameters (inlet water temperature, water velocity, shell-side pressure, fiber length, fiber inner diameter, and overall membrane structure parameter) on VMEWC's outlet water temperature (T_w2), cooling capacity per unit volume (Q_v), and coefficient of performance (COP). The results emphasized that elevated inlet water temperature, reduced shell-side pressure, and a large overall membrane structure parameter effectively enhanced the overall performance of VMEWC. Under specific conditions, Q_v and COP reached impressive values of 3753.1 kW/m³ and 13.6, respectively. This work provides a novel and practical perspective, offering references for advancing efficient and sustainable refrigeration technologies.