Performance investigation of hybrid adsorption-compression refrigeration system accompanied with phase change materials-Intermittent characteristics

In the current study, intermittent characteristics of hybrid adsorption-compression refrigeration systems are evaluated, notably for cold storerooms. This hybrid system utilizes ultra low-grade heat (65 degrees C) and works with natural refrigerants. Herein, the dual-bed adsorption system operates with a working pair of silica gel/water (R718), while isobutane (R600a) is adopted for the compression system. Phase change material (PCM) is additionally incorporated to prolong the compressor off durations and improve the stabilization of the air temperature inside the cold storeroom. Mathematical modeling of the proposed systems is established using MATLAB/SIMULINK framework and validated with relevant literature. An examination of the temporal behavior of the hybrid system's leading indicators such as temperature profiles, cooling capacity, COP, electric power, and electricity demand based on the intermittent characteristics has been conducted and compared against the baseline system. The results demonstrate that the energy saving of the hybrid system during the intermittent operation mode (37%) outperforms the continuous operation mode (31.63%). Also, the hybrid system at the steady-state stage attains COP of -4 compared to -2.3 for the baseline system. However, incorporating PCM into the hybrid system abates the air temperature fluctuation inside the cold storeroom, diminishes the cyclic operations, and reduces the on-time ratio by 24.1% compared to the baseline system (34.8%) while slightly reducing the system COP. The utilization of hybrid refrigeration systems accompanied by PCM has significant profit over conventional compression systems in the market.

Automated summary

The study evaluates the intermittent characteristics of hybrid adsorption-compression refrigeration systems for cold storerooms, utilizing low-grade heat and natural refrigerants. Mathematical modeling shows that, compared to the baseline system, the hybrid system demonstrates improved energy efficiency and stability in intermittent operation mode.