Search Results (2)

This paper presents the results of a simulation study on the selection of an energy-optimal refrigeration system based on natural refrigerants as a function of outdoor climate parameters as a decision variable in a supermarket application. Simulations were conducted for twelve locations. Three new original refrigeration systems were presented: Cascade R744/R717 which is an advanced booster extended with an ammonia condensing system (CASC_1); Cascade R744/R717 with CO₂ pump-fed MT and pressure-fed LT evaporators (CASC_2); and the R717 booster with CO₂ pump-fed MT and LT evaporators (CB_NH3). As a reference system, a CO₂ booster system with multi-ejectors and flooded evaporators (CB_EJ) was adopted. The CB_EJ system has been confirmed to be energy optimal for cold and temperate climates (Cfb, Dfa and cooler). In warm temperate climates (Csa, BSk, Cfa and similar), the energy consumption of CB_NH3 was the lowest. CASC_2 and CB_NH3 are energy optimal for hot climates (BWh, Af, Aw). The CB_NH3 system always outperforms CASC_2 by 2.5–3.8%. For a tropical climate (Bhubaneswar—Aw), the annual electricity demand of the optimal CB_NH3 system is lower by 18.8%, 10.2%, and 2.7% relative to CB_EJ, CASC_1, and CASC_2, respectively. The COP of the CASC_1 (outdoor temperature 40 °C) is higher by 50%, 2.7%, and 4.7% compared with the CB_EJ, CB_NH3 and CASC_2 systems, respectively. The application of CASC_1 system, relative to CB_EJ, is reasonable only for hot climates and decreases by 7.2% the annual electricity demand for Bhubaneswar. Full article

This study presents an experimental rig of a multi-evaporator refrigeration system, in which the pressure difference between two evaporators can be maintained by using both the pressure-regulating valve (PRV) and electronic expansion valve (EEV)-based ejector. The proposed EEV-based ejector that is used to partially recover the throttling losses of the PRV consists of an EEV and the main body of an ejector. The established experimental system can work in both PRV-based mode and ejector-based mode by switching the valves. Via experimental means, the performances of both modes were evaluated by varying the cooling loads. Moreover, the effects of the spindle-blocking area percentage of the EEV-based ejector and the condensing temperature on the system performance were identified. The results showed that: (1) the system performance of the ejector-based mode was 3.6% higher than the PRV-based mode; (2) both entrainment ratio and coefficient of performance dropped along with the increase in ejector spindle-blocking area percentage; (3) compared to ejector spindle-blocking area percentage, the condensing temperature had a more evident influence on the system performance. Full article