In the early discovery of mechanical refrigeration, the machines were bulky and expensive and had little efficiency and had to be maintained by an expert. Mechanical refrigeration was therefore limited to just a few large applications such as ice making units, meat packing, and large cold storage. The industry has grown rapidly over the decades. This rapid growth was the result of several factors. By the advancement of precision manufacturing methods, it has been possible to produce smaller equipment with higher efficiency. This issue has provided safe refrigerants and the invention of less powerful electric motors, the possibility to build small refrigeration units that are nowadays used in applications such as cold storage and freezers, small air conditioners and commercial units. So that fewer homes or business units can now be found that do not use one of a variety of mechanical refrigeration machines.
For example, today without using the refrigeration industry, preparing and storing protein materials will not be possible with increasing population growth. Also in large buildings such as residential, commercial and industrial complexes, if the air conditioning and mechanical refrigeration equipment is not utilized due to the ambient heat in summer, these buildings will be intolerant.
In addition to the use of refrigeration in air-conditioning and its use in refrigeration and cold storage’ processes, in the transportation and maintenance of perishable foods, mechanical refrigeration is used to prepare and supply most of the materials or products of today’s stores. The number of processes or products that are improved using mechanical refrigeration is countless.
For example, refrigeration enables the construction of large dams, which are essential for power generation and irrigation projects. Refrigeration allows the construction of roads, tunnels, foundation wells and drilling in loose ground. Refrigeration makes possible the production of plastics, synthetic tires and many other useful products and materials. Textile and paper manufacturers can increase the speed of their machines using refrigeration and produce more products. Using refrigeration provides better methods for plating the steels used in the machines. These cases are just a corner of hundreds of mechanical refrigeration applications that are used today and every year, several new applications are added to them. The only factor that slows down the growth of the refrigeration industry is the lack of experts in the industry.
A- Classification of refrigeration applications
Application of refrigeration can be divided into six main categories for the ease of studying the refrigeration industry: 1) Household refrigeration 2) Commercial refrigeration 3) Industrial refrigeration 4) Transportation refrigeration 5) Air conditioning of buildings 6) Industrial air conditioning.
The exact boundaries of these groups are obviously unclear and there is some interference between them.
Household Refrigeration: The scope of household refrigeration is limited and mainly relates to household cold storage, but due to the multitude of use, it includes a significant portion of the refrigeration issue.
Household cold storage are usually small and manufactured with input capacities of 35 to 375 watts. In these devices, closed compressors are used.
Because of the public familiarity with these devices, they are no longer discussed, but issues related to their design and maintenance will be investigated in different seasons.
Commercial Refrigeration: Commercial refrigeration is limited to the design, manufacture, installation and repair of refrigeration equipment used in shops, restaurants, hotels and institutions of producing and preparing perishable food.
Industrial Refrigeration: Because of the unclear precise limits of industrial and commercial refrigeration, they often confuse them with each other. Generally, industrial refrigeration devices are larger in size than commercial refrigeration devices and are maintained by one experienced technician. The common samples of industrial refrigeration are ice making units, packaging of large protein materials (meat, fish, poultry, frozen foods, etc.), beverage-making, ice cream-making and industrial units such as oil refineries, chemical units, rubber-making units, etc.
Transportation Refrigeration: Some of the applications of this group can be considered as a branch of commercial refrigeration and another part as a branch of industrial refrigeration. However, both cases are sufficiently extensive and significant.
Ship refrigeration is observed in fishing vessels and transport tanks of perishable products. Transportation refrigeration relates to refrigeration equipment used in trucks for long or local transport and its wagons.
Air Conditioning: This category is related to the weather conditions in the areas or spaces concerned and includes not only temperature control but also humidity and wind speed control along with its purification and cleaning.
Applications of air conditioning are both household and industrial types. Systems whose primary function is air conditioning for human convenience are called home air conditioning. Examples of these systems can be found in homes, schools, offices, mosques, hotels, supermarkets. , Public buildings, factories, cars, buses, airplanes, ships, and so on. On the other hand, any air conditioning that its main goal is not human welfare is called industrial air conditioning. This necessarily means that industrial air conditioning systems according to their primary function cannot be used for human comfort.
The applications of industrial air conditioning are unlimited in terms of number and variety. In general, the task of industrial air conditioning systems is to: 1) control the humidity of the wet material; 2) control the intensity of chemical and biochemical reactions; 3) limit the amount of fine material changes in terms of expansion and thermal shrinkage 4) Provide clean and refined air, which is often needed for comfortable issue and production of better quality products.
– Refrigeration cycle:
Refrigeration is the heart of cooling production. There are 4 processes in a refrigeration cycle that we describe.
- The heart compressor is the refrigeration system that pushes the refrigerant into system and captures the high pressure refrigerant surrounding the condenser. The refrigerant fluid before this gas phase is low pressure.
- In condenser, refrigerant at high temperature and pressure gives its heat to the environment and cools and becomes a high pressure condensing liquid.
- The condensed liquid, after passing through the expansion valve, its pressure reduces and its temperature reduces.
The low-pressure refrigerant goes into the evaporator where it absorbs and cools the heat of the evaporator, thus it converts into a low-pressure gas. This low pressure gas enters the compressor and the cycle continues.