Kinetic Investigation of PbCl2 Composite Adsorbent-NH3 Adsorption Refrigeration System Driven by Ultra-Low-Grade Waste Heat from Data Centers

To achieve the efficient recovery and utilization of low-grade waste heat from data centers， this study systematically investigates the adsorption-desorption characteristics and refrigeration performances of the PbCl2 composite adsorbent -NH3， and establishes a novel system-scale kinetic model. The results indicate that at an ambient temperature of 30 ℃， the PbCl2 adsorbent achieves a cyclic adsorption capacity of 0.295 g/g at 52 ℃， with effective adsorption observed within the evaporating temperature range of 10 ℃ to 25 ℃. The coefficient of performance （COP） of the system increases from 0.26 to 0.44 with the increase of evaporating temperature. There is an optimal range for the desorption temperature， and the comprehensive performance is optimized at 48 ℃. With respect to kinetic modeling， although the pseudo-second-order model adequately described the adsorption process， it exhibited substantial fitting errors during desorption. While the Sigmoid model better captures the typical unimodal kinetic behavior， it lacks the accuracy when describing the variations of initial rate. In contrast， the newly proposed model of incomplete Gamma function， which has a flexibly adjustable shape factor and time-scale coefficient， can control the curve morphology and tailing behavior， achieving goodness of fit values of 99.1% and 97.3% for the adsorption and desorption processes， respectively. This model can accurately characterize the entire kinetic process， effectively overcoming the shortcomings of traditional models， such as large parameter fluctuation， complex calculation， and poor adaptability at the system scale. The proposed model provides theoretical support for the modeling optimization and engineering application of low-temperature adsorption refrigeration systems.