**4.2 Experiments with MR compositions of R600a, R116, R23, and R14**

Experiments based on the composition proportion of high boiling point refrigerant were carried out by replacing R290, the high boiling point refrigerant in the initial refrigerant, with R600a. In this case, the total charging amount in the mass of the refrigerant was the same.

**Figure 15** shows the results of experiments performed by adjusting R600a to a mass fraction of 10–35%. Unlike the experimental results of the R290-applied MR, the compressor suction temperature and discharge temperature did not change significantly according to the composition change of the high boiling point refrigerant, in the results of R600a-applied MR experiments. Furthermore, the evaporator inlet temperature was maintained relatively constant between −109.2 and − 108.4°C.

**Figure 16** shows the cooling capacity and cooling time according to the decrease of mass ratio of the high boiling point refrigerant. As the mass ratio of the high boiling point refrigerant in the composition of the MR decreased, the cooling capacity

*Perspective Chapter: Ultra-Low Temperature Chillers for Semiconductor Manufacturing Process DOI: http://dx.doi.org/10.5772/intechopen.98547*

increased to 1.94–2.27 kW, and the cooling time was 37–46 min, indicating that the target temperature was reached at a slower rate compared to the MR using R290. It appears that a refrigerant with a boiling point between the high and low boiling points needs to be added to reach the cooling time faster.

#### **Figure 15.**

*Temperature comparison of various refrigerant composition cases (including R600a).*
