Simulation study of R134a based vapour compression-adsorption hybrid chiller with activated carbon as adsorbent

Abstract

Vapour adsorption is one of the viable routes for producing refrigeration from low-grade thermal energy. This paper presents the simulation study of a proposed novel hybrid chiller combining a R134a based vapour compression refrigeration (VCR) chiller with a single-bed vapour adsorption (VAd) chiller. The proposed system layout leads to minimal thermal inventory and it also ensures that the VAd system can be integrated with any pre-existing R134a VCR system. The performance of proposed hybrid chiller is compared with the standalone VCR system. Maxsorb-III (MX-III) and a low cost Coconut shell based activated carbon (CSAC) are chosen as the two adsorbents for this comparative study. When compared to standalone VCR system, the hybrid system shows a maximum increment of 50% and 9% in peak refrigeration capacity for 30 kg MX-III and CSAC as adsorbents respectively. Time-averaged specific cooling capacity (SCC) and COP ratio of hybrid to standalone VCR system is used as performance parameters in the present study to evaluate optimum adsorption time, which lies between 450 and 750 s. This paper also presents the evaluation of practical minimum desorption heat source temperature of the hybrid system. For both the adsorbents, minimum desorption temperature lies in the range of 62–71 °C making this hybrid system suitable for both industrial waste heat as well as non-concentrating type solar based heat source.