The first factor is the boiling point. It will create the necessary conditions for the load and the corresponding temperature difference (C) in the evaporator. In the context of the evaporator choice, the difference between the boiling of refrigerant and temperature of the liquid at the inlet of the cooler, not the log mean temperature difference.
In the evaporator cools the air, the air itself becomes a coolant and the temperature and humidity should be examined in relation to the final product. Where the product may not suffer dehydration can be high, so as to reduce the size and cost of the coil, but the lower the boiling point decreases, the lower the productivity of the compressor and its police. In these circumstances, the first assessment can be made with 10-12 K and consult alternatives, no part of this range. In each case, 'owning' costs, i.e. taking into account the running costs should be considered by the user. In table. 10.1 illustrates this for the cold storage for comparison, running 8760 hours in a year. Data should be used for comparative analysis.
Outdoor products are affected by the low humidity of the cooled space may suffer from dehydration.
Conversely, some products, such as fresh meat will deteriorate in conditions of high humidity. Because the dew point of the air approaches edges of the evaporator surface temperature, humidity inside the function of the coil. That is colder fin surface the more moisture condenses out of the air, and the lower the humidity within the space. Optimum conditions for all products, most likely, will be kept in a cool atmospheres will find the standard reference books, or can be known from the practice of trafficking. The following may be taken as a guide:
Products that dehydrate quickly, such as most
Further consideration may be the possibility to reduce the buildup of ice on the evaporator, whether in the form of hoarfrost on the fins or ice on the reels liquid cooling coil. Where temperatures close to freezing point is required, this can be an advantage for design with evaporator temperature high enough to avoid frost or ice - either for security or simplify the method thawing.....
- fruits and vegetables T = 4K
- Products requiring about 85% of the saturated air T = 6K
- Products requiring 80% saturation or drier T = 8K
- Materials are not sensitive to dehydration T = 10 K up