Determination of temperature

1) Salt water temperature t 1 t 1 directly affects the freezing speed and ice mass. With the decrease of t 1, the freezing speed is accelerated, but the evaporation temperature is required to be lower, which reduces the refrigeration coefficient. The increase of t 1 is not conducive to the heat exchange between salt water and ice bucket, and the freezing speed slows down. Generally, t 1 is-10℃.

2) Although the temperature difference t2 between brine temperature and evaporation temperature is large, it can accelerate the heat exchange between brine and refrigerant, which is beneficial to the cooling of brine. However, with the increase of t2, a lower evaporation temperature will be required, which will lead to an increase in power consumption of the compressor unit. Therefore, the evaporation temperature is 5℃ different from the brine temperature.

3) The freezing temperature of salt water should be ensured not to freeze at low temperature, so that salt water can be continuously circulated in the ice-making pool. If the solidification temperature of brine is close to the evaporation temperature, brine is in danger of freezing. However, if the freezing temperature of brine is required to be too low, the power consumption of the agitator will increase due to the increase of brine concentration. Therefore, the solidification temperature of brine is generally set to be 6~8℃ lower than the evaporation temperature.

Preparation of brine

Salt water commonly used in ice making is sodium chloride or calcium chloride solution. The preparation of brine should not only meet the temperature needed in the ice-making process, but also minimize the corrosion to metals.

1) determination of brine concentration The relationship between brine temperature and concentration, the solidification temperature of brine will decrease with the increase of concentration; On the contrary, the curing temperature increases with the increase of brine concentration. Therefore, according to the determined solidification temperature, the corresponding brine concentration can be found from the characteristic table of calcium chloride and sodium chloride solution.

2) The corrosiveness of brine with pH value to metals is related to the pH value of brine. Generally, it is better to be slightly alkaline, that is, the pH value is between 7 and 9. In order to weaken the corrosion effect of brine, corrosion inhibitors can be added to it. The common corrosion inhibitor is made of sodium dichromate and sodium hydroxide, and the ratio is 27kg sodium hydroxide/100kg sodium dichromate. Generally speaking, every 1m? Add 1.6kg sodium dichromate to the calcium chloride aqueous solution, every 1m? 3.2 kg of sodium dichromate was added to the sodium chloride aqueous solution.