Simulation and optimisation of silica gel-water adsorption chiller for enhancing the performance of cooling system

The adsorption cooling system (ACS) using silica gel-water as working-fluid pair is gaining more traction as a substitute for vapor compression system (VCS) due to its environmental friendliness and low energy cost. This paper focuses on improving the efficiency of cooling processes by utilizing silica gel-water adsorption system. The MATLAB-based simulation models integrated with brute force techniques and empirical lumped analytical simulation were adopted in enhancing the operations. Three operational models (A, B, and C) were utilized, with models A and B validating the experimental setup. Model A simulates a laboratory version of a two-bed chiller which uses the Tóth equation for equilibrium uptake and the Clausius-Clapeyron relations for the pressure dynamics. Model B investigates the performance of a two-bed type adsorption chiller with different adsorbents properties. Both models were aligned with experimental outcomes, with Coefficient of Performance (COP) 0.43 and 0.55, specific cooling capacity (SCC) 74.0 and 69.7 W/kg, specific cooling power (SCP) 19.5 and 10.2 W/kg, across hot water (70 to 80°C) and chilled water (-4 to 20°C). The Mean Absolute Percentage Error (MAPE) was between 2.47 to 4.19%, while the Mean Absolute Error (MAE) was between 0.014 to 0.022. Model C enables predictive analysis via user-defined inputs (adsorbent mass, flow rates and temperatures), employing parallel processing for parametric sweeps and transient phase-switching dynamics. Results highlight the system's adaptability to low-grade heat (70 to 80°C, typical of solar thermal or industrial waste heat) and at subzero temperatures, emphasizing its potential for diverse applications. The computational rigor of the framework is validated through thermodynamic and kinetic accuracy, demonstrating silica gel-water adsorption viability in reducing electricity demand and greenhouse emissions. The findings are beneficial to designers of ACS system using silica gel-water as a working-fluid pair, thus contributing to sustainable solutions, which are aligned with global decarbonization goals.