Energy Efficiency of the Beverage Vending Machine Refrigeration System

The beverage vending machine (BVM) in Thailand is normally used the vapor compression refrigeration cycle. The research is conducted under collaboration with one of the leading Thai BVM company. In the research, the used BVM is imported from Japan and refurbished for local market sail so that energy efficiency of the compressor is crucial. If the compressor was used for a long-time its efficiency has been normally deteriorating. The performance of the vapor compression refrigeration cycle of BVM depends on the design, performance of each component; especially compressor, operating control and operation and maintenance. Therefore, it is necessary to monitor the refrigeration system under actual operation and to evaluate the coefficient of Performance (COP) of the refrigeration cycle. The cooling load of the experimental BVM consisted of 594 aluminum cans and Polyethylene terephthalate (PET) bottles totally volume about 189 L. The base case experiment was conducted on the existing refrigeration system of BVM using R-407C refrigerant. Then, the compressor is replaced by the appropriated one from local market for the similar performance test. The experiment on the modified refrigeration system used R134a refrigerant. The BVM has four cold compartments equivalent to 4 cooling coils connected to only one compressor, while 2–3 evaporator coils are operated simultaneously and controlled by four solenoid valves using on-off steps, allowing refrigerant to flow through those coils. The temperature and pressure of the refrigerant loop was measured during BVM operation. The temperature and relative humidity inside the cold chambers was also monitored. The modified refrigeration system showed that the compressor works comparable to the existing one. The average COP of the existing system was 3.43 ± 1.04 higher that of the modified system about 2.35 ± 0.34, although the replacing compressor was appropriately and carefully selected under unavoidable constraints. Therefore, the research in the following phase would investigate the alternative compressor, the control strategy, and the other components modification, effecting the energy efficiency of refrigeration cycle.