The thermodynamic efficiency of the stirling engine has a high theoretical efficiency closest to that of the Carnot cycle, and various heat sources can be used as an external combustion engine. In the early days of the invention, the sealing technology was not good, so it was pushed to the steam engine and was not put to practical use, and in modern times, it was not used due to the development of internal combustion engines. Sterling cryogenic refrigerators using linear compressors have advantages such as low vibration, small size, light weight, low required power, and sufficient durability compared to conventional cryogenic refrigerators, so they are widely used as infrared sensors for night vision goggles (0.5 to 1.9 W at 77 K) and superconducting filters for mobile communication wireless base stations (3 to 6 W at 77 K). By examining the characteristics of the refrigerator using such a stirling refrigerant refrigerator, the difference from the existing refrigeration air conditioning system using refrigerant gas can be seen, and this study showed that the manufacturing method of the motor part and the design of the inlet voltage and current and frequency of the motor greatly affect the performance of small linear stirling refrigerators when manufacturing a compressor of a linear stirling refrigerator.

Global population growth and industrial development are leading to water shortages, and water supplies from surface and groundwater sources are facing serious challenges. Many countries are projected to experience water shortages by 2025. More than 50% of these countries will face water resource depletion, and Korea is also expected to face water shortages, necessitating the development of water supply measures. This study explores the application of refrigeration technology to address this water shortage. It explores a small-scale seawater desalination system that utilizes the phenomenon of freshwater contained in seawater accumulating on the surface of a brine-cooled drum-type evaporator. This system exploits the phenomenon of freshwater contained in brine freezing on the low-temperature drum surface. Experiments were conducted to determine the amount of freshwater captured by varying the brine temperature entering a brine-cooled drum-type ice maker and the gap between the blades used to cut the frozen ice. When tested using seawater as the base, it was found that when the circulating brine temperature in the drum-type ice maker was -30℃ and the gap between the drum-type ice maker and the cutting blade was 1 mm, the salinity was removed by about 95%, and about 2.28 liters of fresh water could be produced per hour. It was also found that it was easy to install for small-scale seawater desalination and could be used with a low power capacity of about 2.3 kW.

The purpose of this study is to compare and analyze the conventional constant-speed compressor driven by an induction motor and the BLDC-applied capacity variable compressor in order to improve the energy efficiency of the refrigeration system. Through this study, it was found that, when a reciprocating hermetic compressor is operated, more power is consumed than a BLDC compressor due to the consumption of current through the instantaneous starting capacitor when operating at a constant voltage than a BLDC compressor.

This study aimed to develop an algae reduction device using bubbles to improve algal blooms occurring in lakes or reservoirs in summer, and to design a venturi, a major core device for bubble generation and supply. As a measure to improve the bubble generation effect of the venturi, the venturi was devised to change the air intake characteristics, and the flow characteristics were analyzed through CFD simulation to achieve the optimal design.