XII Международная студенческая научная конференция Студенческий научный форум - 2020

In the modern world, long-distance car trips are made by each person quite often, and therefore for most people automobile refrigerators and temperature containers have become a necessity, especially in the warm season, for the safety of products during rest or for their transportation between cities.

The frozen food industry aims at providing customers with safe, high-quality food products. Proper transportation and storage of frozen foods throughout the distribution process is essential to maintain food safety and quality. The packages containing frozen foods should be efficiently constructed, thermally insulated and equipped with sufficient refrigerants to continuously maintain product temperature of 0°C (32°F) or colder. Thermal containers are needed as they limit the exchange of heat between the environment and the inside of the package, thus delaying the time in which the temperature inside the package reaches equilibrium with the ambient temperature.[1]

Current research objectives:

- studying ways of storing frozen products during transportation;

- developing more reliable heat chambers, as well as considering options for extending shelf life.

There are several types of thermal cameras:

- thermal container;

- thermal bag;

The thermal container acts on the principle of a thermos and is able to maintain not only cold, but also heat. Thanks to the thick walls, it retains temperature well. They are made of rigid polymeric materials with thermal insulation from foam or foam rubber with metal containing inner lining.[2]

The thermal bag is a type of thermally insulated shipping container in the form of a bag which can be carried.

It is usually made of heat-insulating materials and refrigerant can be used to help maintaining the temperature of its contents, keeping cold items cold, and hot items hot.

Insulated bags have been in use for many years in industry, medical/pharmaceutical use, food delivery, lunch bags, etc. But such a bag, even tightly closed, is able to maintain the same internal temperature for only 2-3 hours. [3]

In order to extend the storage time of frozen products, we can use packages with refrigerants. The gel bag is a portable plastic bag filled with refrigerant. For use, the contents are frozen in the freezer. non-toxic refrigerants can absorb a significant amount of heat before they heat above 0 ° C, due to the high latent heat of fusion of the water. These packages are typically used to cool food in portable refrigerators or in insulated shipping containers to cool food during transportation.

Gel packs are often made of non-toxic materials that will remain a slow-flowing gel, and therefore will not spill easily or cause contamination if the container breaks. Gel packs may be made by adding hydroxyethyl cellulose.[4]

In transporting fish the shelf life can be increased with ice. This action mainly prevents surface dehydration and reduces weight losses. Melting water also increases the heat transport between fish and ice surfaces (water conducts heat better than air): the quickest practical chilling rate is obtained in a slurry of water and ice.[5]

There are also auto-refrigerators of 2 types: ammonia or freon vs thermoelectric. The main component for the operation of automotive refrigeration equipment is open refrigerant (ammonia or freon). In addition to the refrigerant, the composition of such a refrigerator includes a sealed system, a receive, where the liquid is located, as well as an evaporator and heating element. Refrigerators with a refrigerant work as follows: a special compressor and a hermetic system are used at the base of the refrigerator. The compressor pressurizes the refrigerant (usually in a gaseous state) to the evaporator. At the moment of transition from a gas to a liquid state, it cools the surface of the evaporator, thereby generating cold. This type of device is considered more reliable, but besides advantages there are also some disadvantages. The downside is that ammonia is harmful to humans, regardless of whether it is pure or diluted. In the event of an accident and depressurization of the ammonia automobile refrigerator system, pure ammonia can easily injure the airways, that is why this type of refrigerator is not in great demand, although prices are moderately low.[6]

Refrigeration units with freon can distinguish several types (classes) and among them there are both safe and dangerous. In some freon installations, manufacturers can use the brand of freon R600a, which, in contact with open fire, ignites very quickly. The thermoelectric refrigerator kit includes a cooling device, a heat exchanger, a semiconductor and thermoelectric modules. The box of the refrigerator itself is made of aluminum inside, it is this part that absorbs heat from foods and food products. The resulting heat is transferred to a special thermal module, which in turn transfers it to the stabilizer. It is the temperature difference in the metal and the heating due to current that leads to the absorption of heat and the generation of chilled air on the design of an automobile refrigerator.[7] A thermoelectric refrigerator can lower the temperature of products by 4-6 degrees Celsius relative to the street. Such a refrigerator will not give minus temperature, but cooling drinks using it is quite possible. The above types of refrigerators consume quite a lot of electricity, which affects fuel consumption, the box should be located near the outlet. Not all car refrigerators have battery control. With the car turned off, you can easily put the battery in and there will be a problem in how to start the car.

Having considered all the pros and cons of existing equipment, we focused our efforts on developing a heat chamber, since there is no mechanical part or power supply system from the vehicle’s on-board network.

Our next task in is to develop a pneumatic shutter to improve tightness of the chamber.

References

1. Alternative Insulation Solutions for Frozen Food Transportation Electronic data. - Access mode https://ipcpack.com/resources/alternative-insulation-solutions-frozen-food-transportation/

2. Isothermal containers Electronic data. - Access mode https://www.ap-portugal.com/en/food/isothermal-containers/

3. Thermal bag Electronic data. - Access mode https://en.wikipedia.org/wiki/Thermal_bag

4. Ice pack Electronic data. - Access mode https://en.wikipedia.org/wiki/Ice_pack

5. Improved fish handling methods - Electronic data. - Access mode http://www.fao.org/3/v7180e/V7180e08.htm

6. Risk Management When Using Ammonia as a Refrigerant Electronic data. - Access mode https://www.goodway.com/hvac-blog/2012/10/risk-management-when-using-ammonia-as-a-refrigerant/

7. Thermo-electric Car Cooler Warmer Travel Refrigerator Electronic data. - Access mode https://www.costway.co.uk/26l-mini-thermoelectric-car-cooler-warmer-refrigerator-portable-travel-fridge.html

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