Publication

Abstract : This work focuses on a decentralised freshwater generation system where the waste heat from an air-conditioning (AC) system’s condenser unit is utilized to drive a hybrid humidification-dehumidification (HDH) desalination process. A Response Surface Methodology (RSM) with a Box-Behnken Design (BBD) is employed to investigate and optimize the influence of key operational parameters-AC temperature, feed flow rate of domestic wastewater across the humidifier, and coolant flow rate across the dehumidifier on system performance. The performance metrics analyzed include freshwater yield and Gained Output Ratio (GOR). The key novelty of the present work includes the utilization of heat pipes as a dehumidifier for the hybrid HDH unit and the identification of the optimal system conditions that deliver maximum yield and GOR. The experimental and supporting RSM analysis indicated that a maximum freshwater yield and a GOR of 1.12 kg/h and 0.039 were achievable with the usage of three heat pipes dehumidifier. From further analysis, it was inferred that efficient heat transfer and sustained condensation rates on the surface of the heat pipes contributed to an increased freshwater yield with a projected GOR of 0.57 for a scaled-up configuration employing around 44 heat pipes. Analysis of Variance (ANOVA) validated the model’s robustness, exhibiting high correlation between experimental and predicted values. Surface and contour plots highlighted the hierarchy of parameter influence, with coolant flow rate having the most significant impact, followed by wastewater feed rate and AC temperature. The developed models demonstrated strong predictive accuracy with R2 values of 99.97% for freshwater yield and 99.59% for GOR, and adjusted R2 values of 99.92% and 98.84%, respectively. These findings confirm the feasibility and efficiency of repurposing low-grade waste heat from AC systems and using a novel heat pipe dehumidifier for sustainable water treatment, offering a promising solution for water-scarce urban environments through enhanced thermal management and process optimization.