Development of mixed-refrigerant Joule-Thomson refrigerator below 120 K

Abstract

The purpose of the present study is to develop an efficient mixed-refrigerant Joule-Thomson (MR JT) refrigerator below 120 K (-150 ℃). The demand of high density semiconductor increases to respond to the treatment of the extensive data. One of the promising technologies in the semiconductor manufacturing process is cryogenic etching which requires a temperature below -100 ℃ for more efficient production and precise manufacturing of the semiconductor. The refrigerator in the semiconductor facility assures extreme safety and high efficiency. Therefore, the MR JT refrigerator can be a sensible choice satisfying to the prerequisite. This study utilizes the cascade cycle with non-flammable refrigerants. Both of the selection of the adequate MR constituents and determination of the MR composition are crucial factors to develop the efficient refrigerator. The liquid-phase range diagram indicates the temperature range from the triple and critical points. It provides the appropriate components to Ar, R14, R23, and R218. The iso-thermal enthalpy difference graph suggests that the composition (Ar+R14+R23+R218 = 0.5+0.3+0.1+0.1) can yield high efficiency. The result of the cycle design presents that the maximum COP at 120 K is approximately 0.371. One of the available methods to enhance the cycle efficiency is to apply an ejector in the designed MR JT refrigerator. This study also explored the effect of ejector utilization on the efficiency. The result shows that the cycle efficiency with an ejector is approximately 1.8 % higher than that without the ejector. Also, the exergy efficiency is about 47.6 %. A heat exchanger is one of the influential cycle components on the efficiency. In the present study, two kinds of heat exchangers (TYPE-Ⅰ and TYPE-Ⅱ) are fabricated and their performances are evaluated experimentally. From the experimental results, the heat transfer correlations for the TYPE-Ⅰ heat exchanger are proposed. In addition, TYPE-Ⅱ heat exchanger is fabricated to enhance the performance on the TYPE-Ⅰ heat exchanger. The TYPE-Ⅱ shows the enhanced performance compared to the TYPE-Ⅰ. The heat flow of TYPE-Ⅱ is about 1.7 times higher than that of TYPE-Ⅰ since the heat transfer area and coefficients are enhanced in the TYPE-Ⅱ. The experiment study is conducted to assess the performance and to verify the numerical result. The experimental apparatus for the MR JT refrigerator was constructed with the developed TYPE-Ⅱ heat exchanger. As a result, the target temperature (120.3 K) is achieved with a cooling capacity of 2.1 W. Also, the cooling capacity map is proposed.