Experimental study on diffusion absorption refrigerator achieving 0.2 coefficient of performance using low global warming potential refrigerant and low-grade heat source

[Display omitted] •R600a/n-octane is newly proposed for diffusion absorption refrigerator.•Copper absorber is preferred to R600a without using ammonia refrigerant.•Effectiveness of steel and copper absorber is compared with numerical analysis.•A high COP of 0.2 is achieved with copper absorber.•A generator temperature of 71 °C shows suitability for solar applications. The commercial model of diffusion absorption refrigeration operated purely via thermal energy utilizes ammonia as a refrigerant. Ammonia is not only a toxic substance but also reacts with copper; thus, most commercialized diffusion absorption refrigerator is fabricated using carbon steel instead of copper. In the previous research, copper cannot be used in the diffusion absorption refrigerator because of the ammonia. However, in this study, via the newly proposed low global warming potential refrigerant R600a, copper absorber can be employed to improve the coefficient of performance of diffusion absorption refrigerator. R600a, n-octane and helium are used as the refrigerant, absorbent, and auxiliary gas, respectively. Simultaneously, the bubble pump and absorber are fabricated from copper to improve the heat transfer rate. As a result, a high coefficient of performance is achieved despite the use of a low global warming potential refrigerant. In particular, the experimental analysis is conducted with a focus on how the effectiveness and performance of the absorber vary by comparing carbon steel and copper as the absorber material. The configuration of the two diffusion absorption refrigerators is exactly the same but the absorber material is changed. When employing copper, the effectiveness of the absorber is improved by 9.09–35.71% compared to that of carbon steel absorber under the same heat input. In addition, an experimental investigation is conducted by changing the pressure to 400 kPa, 465 kPa, 530 kPa, and 600 kPa for heat input in the range of 30–100 W to analyze the effect of heat input and operating pressure. By utilizing copper for diffusion absorption refrigerator with R600a, a coefficient of performance of 0.20 is achieved at a low generator temperature of 71.07 °C, which is the highest coefficient of performance and the lowest generator temperature with low global warming potential, so that solar energy can be utilized as the heat source in the present diffusion absorption refrigerator system.