Carbon–ammonia pairs for adsorption refrigeration applications: ice making, air conditioning and heat pumping

A thermodynamic cycle model is used to select an optimum adsorbent-refrigerant pair in respect of a chosen figure of merit that could be the cooling production (MJ m⁻³), the heating production (MJ m⁻³) or the coefficient of performance (COP). This model is based mainly on the adsorption equilibrium equations of the adsorbent–refrigerant pair and heat flows. The simulation results of 26 various activated carbon–ammonia pairs for three cycles (single bed, two-bed and infinite number of beds) are presented at typical conditions for ice making, air conditioning and heat pumping applications. The driving temperature varies from 80 °C to 200 °C. The carbon absorbents investigated are mainly coconut shell and coal based types in multiple forms: monolithic, granular, compacted granular, fibre, compacted fibre, cloth, compacted cloth and powder. Considering a two-bed cycle, the best thermal performances based on power density are obtained with the monolithic carbon KOH-AC, with a driving temperature of 100 °C; the cooling production is about 66 MJ m⁻³ (COP = 0.45) and 151 MJ m⁻³ (COP = 0.61) for ice making and air conditioning respectively; the heating production is about 236 MJ m⁻³ (COP = 1.50).