Figure 9 shows the ice thickness at different times in the experiment. It can be seen that the thickness increased with time, rapidly increasing in the initial stage and slowly increasing at the end of production. This was due to ice layers forming in the ice-making tubes. The ice had low heat conduction, which resisted heat transfer between liquid water and ammonia or the refrigerant, outside the tube. Therefore, when the ice thickness increased, heat transfer became more difficult. The heat flow rate between the water, which was liquid, and ammonia became increasingly lower and lower. Thus the cycle of ice formation slowed. This means that the cooling load also changed with time.