Monte Carlo simulation of an ammonia adsorption refrigeration system based on calcium chloride impregnated nanoporous...

We use Monte Carlo simulations to investigate the effect of incorporating calcium chloride salt into nanoporous carbon on the performance of an ammonia-carbon adsorption refrigeration system. Simulations of ideal carbon slit-pores with pore sizes of 1, 2, and 3 nm, each containing calcium chloride with ion densities of 0.0, 0.25, and 0.5 nm-3, were carried out at temperatures between 0 and 30 °C and ammonia pressures up to 15.0 bar. The results reveal that ideal 1 nm pores are able to achieve a good refrigeration performance using waste heat below 100 °C to drive the process, but adding salt to these pores increases the waste heat temperature required beyond 100 °C. However, ideal 2 nm pores require the addition of 0.25 nm-3 salt to achieve a similar performance, while the 3 nm pores were unable to achieve a satisfactory refrigeration performance. Considering that real nanoporous carbons usually feature a variety of specific adsorption sites and non-ideal geometries that should have a similar impact to adding salt, these results indicate that nanoporous carbons with pores in the range of 1-2 nm are likely to hold the most promise for adsorption refrigeration applications and that the addition of salt may not always be helpful.