Cold storage

Equipment for refrigerated storage is widespread and varies considerably in size and capacity, which depend on the specific applications.

Small-sized equipment is, as a rule, refrigerated cabinets with absorption machines on trailers or marine vessels. There are also larger domestic or industrial refrigerators, relatively small cold rooms in warehouses and, eventually, large cold storage rooms with loaders to move pallets or product crates, some of which can handle thousands of tons of food. Many refrigerated warehouses for fruits are equipped with additional control of the atmosphere, which, to increase the shelf life of the product, maintains a low oxygen content and a high carbon dioxide content. This technology is not new, and has recently been widely used in connection with the possibilities of improving the quality of products [8]. We will look at store-cooled refrigerated display cases below in a separate section, and a description of the design of home and several larger industrial refrigerators is beyond the scope of this book.

For the preparation of most refrigerated products and their short-term storage, small cold rooms are preferable. Although they are also designed as part of the overall structure of a building, modular construction is most often used when refrigerating chambers are located in existing premises. If we are talking about the storage of semi-finished products, they cannot be stored together with other foodrefrigeration tunnel device in the store

Fig. 4.3. refrigeration tunnel device in the store

products requiring cold storage. [3] prescribes the following rules for cold storage of semi-finished products:

  • first, it is necessary to decide on the type of packaging / packaging used and methods of loading and unloading - for example, whether it will be disposable containers, roller pallets or something else;
  • you need to determine the frequency and volume entering the storage of goods to calculate the required storage time and storage space;
  • the applied thermal insulation must comply with the maintained temperature in the storage and meet the operational standards (taking into account the wear of the insulation during operation);
  • materials used for decoration (interior and exterior) shall be durable and easily replaceable;
  • duplication of compressor systems should be used to ensure safety and reliability in case of emergency;
  • for large storages where frequent movements in and out are planned, air curtains or additional lock doors should be provided;
  • evaporator coils must have sufficient performance to ensure the required parameters even in the case of sizing or frosting;
  • defrost system must be efficient and equipped with devices to remove thawing water;
  • alarm and blocking systems should be designed so as to exclude the possibility of locking in the chamber of the staff;
  • continuous monitoring and / or temperature recording should be provided with the possibility of external control in case of equipment failure.

Modular cold rooms are small closed-loop systems ranging in size from 2 to 30 to m3 and more. Refrigerator condenser units may be located on top, side, or be removed from the chamber in case of poor ventilation and heat removal. If necessary, you can build a sequence of multi-chamber storages where chilled, frozen or fresh products will be stored. One of the options for a modular cold room for a low-ceiling room is shown in 4.4 Figure, although a variety of placement options are possible depending on local conditions.

For larger stores, the main requirement is to take into account the methods of placing and moving products and loading / unloading methods, which determine the height of the store, whether a stationary racking system for palletized or “boxed” storage is required or not, as well as the overall size of the store. In most cases, industrial cold storage rooms are designed for their specific use with possible changes in a few years, so that, if possible, some flexibility and versatility should be provided for reconstruction without major alterations.

The evaporators of the refrigerator, from which cold air begins to circulate in the storage chamber can be located on the back wall of the chamber, on the wall near the ceiling,Driving modular refrigeration chamber premises with a low ceiling

Fig. 4.4. Driving modular refrigeration chamber premises with a low ceiling

as well as being raised to the center of the ceiling. In any case, the placement of the evaporator must be such as to ensure that cold air is available to all parts of the chamber, and the fan must have sufficient power to ensure air circulation with the required temperature. Many of the above options for refrigerated cargo storage are also suitable for larger chambers.

Many refrigerating chambers were designed with steel structures for fixing internal heat insulating surfaces, however, at present such a construction is increasingly being replaced by a structure using profiles in which the intersecting surfaces are attached to each other. In those cases where the use of such technologies is possible, they can significantly reduce the cost of building a refrigerator.

When designing any large refrigerator, it is important to protect vehicles and cargo during loading and unloading operations. Protection from exposure to sunlight and precipitation is especially important, and for many important operations temperature control of the loading / unloading zone is necessary.

refrigerated transport

Basic requirements

Refrigerated transport for the transport of refrigerated products is the primary means of moving refrigerated food products from one storage facility to another. The operations that make up the transportation of chilled cargo form a kind of chain of operations, from which the actual transportation of cargo in a refrigerated truck, isothermal container, railway car, ship or plane is only part of this chain. Maintaining the temperature throughout this chain is extremely important for successful transportation, but even the best refrigeration equipment will not be able to compensate for damage during loading and unloading operations, damage from improper packaging, stacking or improper cooling of the product [10]. By itself, the term "refrigerated transport" can be misleading - it is more appropriate to talk about "transport with temperature control." For example, transporting food in a cold winter can freeze a product that should not be frozen (this applies in particular to many tropical fruits that can be irreversibly damaged even at moderate temperatures). Thus, the well-known bananas should not be cooled below 13 ° C, and in countries with cold winters, heating of the product is required instead of cooling. Understanding the difference between the “refrigerator” (refrigerator) and “temperature control” is very important for the consumer of refrigeration equipment, who may not know that incorrect parameters when setting temperature conditions in transport can heat up the product, which will inevitably lead to a lack of cold in stationary stores.

In general, the transport equipment is designed to maintain the required temperature, and not at all to cool the product. In the process of transportation, the product, of course, may be subject to some cooling, but this is a very slow and completely non-standard method, which we will not even consider here. The pre-cooled product, wherever possible, should be in a temperature controlled environment. In some cases, packaging designed to cool a product in horizontal airflow chambers may not be applicable in vehicles where vertical streams are mainly used.

There are a large number of various types of refrigerated transport. The simplest of them are thermoses, containers with ordinary ice, and the most complex ones are isothermal containers with integrated refrigeration equipment. Such equipment is able to maintain the required temperature for chilled or frozen products when the external temperature varies from -20 to + 50 ° С. Most often it is a car specially designed for cargo delivery either to local customers, or over long distances, or for wholesale deliveries (Fig. 4.5).

Temperature control of the cooled product is more difficult in practice than for the frozen product. As a rule, for chilled products and semi-finished products, it is necessary to maintain the temperature between 0 and 5 ° С (for many products only with small deviations), whereas for the frozen product the upper temperature limit is -18 ° С, and the lower one is not regulated at all. To achieve temperature stability in the transported refrigerated product, constant air circulation is essential, a high level of temperature control of the product is necessary, and proper and careful stacking inside the vehicle to achieve proper air circulation.Semitrailer

Fig. 4.5. Refrigerated semi-trailer, a van and a removable container

motor transport

Refrigerated vehicles are divided into two main categories: first, they are large semi-trailers with a refrigeration device that can operate independently of the tractor; secondly, these are trucks of various capacities with an independent body cooling system or with a cooling system powered by an engine or axles; coolant can also be used to cool the body. Semitrailers are used for the transportation of goods over long distances and for the transport of bulk cargo, usually in one or several destinations. Travel time can vary from several hours (when delivering goods to supermarkets) to several days. A typical device of such a semi-trailer is shown in Fig. 4.6. Although currently most of these vehicles use diesel engines with additional electrical equipment, refrigerant tanks (liquid nitrogen or carbon dioxide) are sometimes used to reduce capital costs and noise levels.

In most developed countries, refrigerated semi-trailers are designed for use at ambient temperatures above 30 ° C. Heat insulation rated at 0,7 W / m2K and above. For the transport of frozen products, transport with thermal insulation on 0,4 W / m is used.2K. Increasingly, multi-chamber multi-purpose machines are being produced and used, capable of transporting frozen, chilled and fresh products simultaneously in separate chambers.

Refrigerated trucks are very different - from huge refrigerators, similar to semi-trailers, to small trucks to deliver goods to stores. Their refrigeration units can be powered by a diesel or electric motor, hydraulically driven from the chassis, and they can use both conventional and eutectic cooling systems. The latter system is more often used for the transport of frozen products, since it is rather difficult to control the temperature range for refrigerated products - after all, during the delivery process, you have to take products from different shelves and quite often open the doors of the refrigerator compartment. UK regulationsDriving device refrigerated semi-trailers

Figure 4.6. Driving device refrigerated semi-trailers

with regard to food safety, [4] provides developers of transport refrigeration equipment with data on increasingly stringent temperature requirements.

The needs of customers forced the developers to pay more attention to the development of multi-chamber refrigerators with separate temperature conditions in each chamber. Such vehicles can deliver to the trading network and frozen, and chilled, and fresh products at the same time. In such vehicles, each chamber may have its own separate evaporator coil; In addition, a fan can be used to move some amount of cold air from the coldest chambers to warmer ones. As a rule, in refrigerators on wheels, the temperature of the air entering the refrigeration chamber, as well as the temperature of the air returned from the refrigerator, is monitored using either external thermometers or displays, or (more often) a display installed directly in the cabin. In the old models of refrigerators, which are usually intended for the transport of frozen products, the control was carried out only for the air returned to the refrigerating chamber, with the risk of freezing the cooled products that were loaded too warm.

Insulated shipping containers

Isothermal freight containers (the so-called 150 containers) with integrated refrigeration equipment are widely used to transport fresh fruits, vegetables, and chilled meat over long distances. Since such flights can last up to six weeks, isothermal containers are equipped with highly reliable refrigeration units and a powerful temperature control system that is capable of maintaining the cargo temperature unchanged with large fluctuations in the ambient temperature. Such containers are mainly used for door-to-door export-import operations by sea transport [5, 10, 13], although it is possible to use such containers as temporary storage for refrigerated products. The standard length of such containers is 20 or 40 feet with a volume from 28 to 60 м3, and their cooling units, as a rule, operate either from a three-phase network or from a diesel generator. The main difference between isothermal containers and refrigerated trucks is that air is supplied through a T-shaped flooring (Fig. 4.7).

Brief description of the equipment

It should be borne in mind that the required temperature control with the possibility of heating.

Automobile transportLarge semi-trailers for international and long-distance transport, large trucks mainly for deliveries to the distribution network, small trucks for local transportation
Containers:IS0-containers with refrigeration unit for transportation over long distances, mainly by sea transport.

The circuit device of the isothermal container

Fig. 4.7. The circuit device of the isothermal container

Refrigerated showcases and counters

Refrigerated display cases and retail counters are divided into two main groups. Most are vertical cabinets with shelves, serving for laying out and selling packaged chilled products, fresh meat and poultry by self-service. Examples of such counters are shown in Fig. 4.8. In addition, there are counters for sliced ​​but not packaged foods. Multi-storey refrigerated showcases are equipped with an evaporator located at the base and with either an autonomous condenser or a condenser connected via pipelines to a central refrigeration unit (in large commercial enterprises). The evaporator coil is mounted either in the lower part of the display case, or behind it, or below the display area, and the fan delivers cold air both behind the shelves with food and just before the glass, creating a kind of air curtain in front of the doors. Warm air is removed through the slots in the base of the cabinet.

Modern multi-tiered refrigerated display cases have been designed to maintain the temperature of the product at 5 ° C and below, however some older models have difficulty keeping the temperature below 10 ° C. The temperature of the product in the showcase depends not only on the design of the showcase itself, but to a large extent on the layout. Thus, a dense or erratic layout of products may interfere with the circulation of cold air, and indiscriminate placement of price tags or promotional materials may also lead to this. High temperatures in the room or heat from the lamps may cause the products to heat up in the display case. The advanced experience with such refrigerated showcases shows that good results can be achieved by covering refrigerated showcases for the night with special covers. It should be borne in mind that refrigerated display cases and counters are designed only to maintain the desired temperature - you should not put hot or warm food or dishes in them. In some countries, to achieve a more productive cooling of the product at anyMultilevel counter

Counter

Figure 4.8. Multilevel counter: a) a separate module; b) counter with an increased area calculations

while showcases with doors were replaced almost everywhere with high-bay showcases, however they have some inconvenience for trading due to the large loading time and the possibility of thefts. Some open windows have combined shelves to accommodate non-refrigerated and refrigerated products.

In the self-service display windows, the products are located on the base, which is blown by a stream of cold air. As a rule, they are glazed in front. The air from the evaporator located on the rear side can be supplied by the fan or without it, but considering that most of the products in this display case are unpackaged, it is necessary to avoid high airflow rates due to possible losses of moisture and mass. For these reasons, the products are placed on the same storefronts only for the working time of the store, and for the night they are put in refrigerators. The diagram of the device of such a showcase is shown in Fig. 4.9. Variants of similar counters for demonstration of the cooled ingredients of dishes are also used in some grocery stores and catering establishments. In showcases of this type, refrigerated products are located in such a way that cold air is blown from below, keeping the food cold with a curtain of cold air. This is just one example of the design of equipment of this type, created based on the specific requirements of the customer.

When choosing refrigerated display cases or counters, you should first of all consider the required method of using them, the requirements for temperature control, and the level of costs; moreover, operating costs and ease of maintenance are also important. When choosing a refrigerant, proceed from the considerations outlined in the chapter “Refrigerants and the Environment”. At the time of this writing, the most common equipment was based on hydrogen-fluorine-carbon compounds. The use of SFC and HCFC (freon) in the new equipment is virtually ceased, and these systems are considered obsolete. In some countries, systems with secondary liquid cooling (brine or glycol) are also used. These liquids are cooled by a central device that uses (in large enterprises) ammonia. Equipment buyers in anySelf Showcase

Fig. 4.9. Self Showcase

The case should be guided by the regulations of the country where it is intended to be used, but the general prospects for the future use of refrigeration equipment are greatly complicated by ambiguities regarding refrigerants in environmental terms.

Conclusion

Manufacturers produce a wide enough range of refrigeration equipment to meet any customer requirements, both in terms of design features, and in terms of taking into account the temperature regimes for various products.

Normative acts

There are quite a few regulations governing the process of cooling food products, and they are discussed in more detail in the chapter 16.

Some countries have general standards for food safety, and often (as in the UK) they contain specific provisions that determine the temperature of certain food materials [4]. It should be borne in mind that such provisions, as a rule, concern not only the necessary equipment, but also its correct use, and also contain relevant provisions for the training of personnel involved in the processing, storage, delivery and retail of refrigerated products. For international shipments, there are provisions for international trade (APR) [14] that apply to both thermal insulation requirements and parameters of refrigeration equipment used in transportation, as well as temperature parameters during storage of various types of products. Some countries (in particular, France, Spain, Portugal and Italy) have their own national regulations, but these provisions are not considered part of the APR. As for the common economic space of the EU, uniform standards in this area are still being developed.

In some cases, there is a lot of similarity in the processes for producing chilled and frozen foods, but legal differences between these two categories of products should always be considered. Requirements for loading and unloading equipment used to work with chilled products may be supplemented by additional provisions that differ from those applied to frozen products, and this should be taken into account, for example, when organizing multi-temperature refrigerated storage facilities where simultaneous storage of both frozen and refrigerated products, and when using combined vehicles.

Some organizations for information

The Institute of Refrigeration, Kelvin House, 76 Mill Lane, Carshalton, Surrey SM5 2JR, UK. Web site

British Refrigeration Association, FETA, Henley Road, Medmenham, Marlow, Bucks SL7 2ER, UK. Web site:

International Institute of Refrigeration, 177 bd Malesherbes, F 75017, Paris, France. W

Cambridge Refrigeration Technology, 140 Newmarket Road, Cambridge CB5 SHE, U1 site:

Literature

  1. ALDERS, A. W. C., (1987) Marine refrigeration manual, RMCA, The Hague.
  2. ANON, (1987) UNEP, Montreal protocol on substances that deplete the ozone layer.
  3. ANON, (1989) Planning for cook-chill, The Electricity Council, London, 5th edn.
  4. ANON, (1995a) Food safety (general hygiene) regulations, HMSO S.I. 1763.
  5. ANON, (1995b) Guide to refrigerated transport, International Institute of Refrigeratior
  6. ANON, (1997) Guidelines for good hygienic practice in the manufacture of chilled Chilled Food Association.
  7. ASHRAE HANDBOOKS, ASHRAE, Atlanta, updated annually on a 4-year cy Fundamentals, Refrigeration, Systems, Equipment.
  8. BISHOP, D., (1996) Controlled atmosphere storage. A practical guide. David Bishop Consultants, Heathfield.
  9. CRITCHELL, J. T. and RAYMOND, J., (1969) A history of the frozen meat trade, Da London, (original edition 1912).
  10. FRITH, J., (1991) The transport of perishable foodstuffs, SRCRA Cambridge.
  11. GOSNEY, W. B., (1982) Principles of refrigeration, Cambridge University Press. HEA (1989) Design and performance of insulated and refrigerated ISO intermodal containe J. Refrig., Vol. 12 (May), pp. 137-145.
  12. HEAPRD, (1998) Global warming - considerations for the air-conditioning and refrig * industry. Dreosti Memorial Lecture. SAIRAC, Cape Town.
  13. THEVENOT, R., (trans. FIDLER, J. C.) (1979) A history of refrigeration throughc world, International Institute of Refrigeration, Paris.
  14. UNECE, (1998) Consolidated text of the agreement on the international carriage of per foodstuffs and on the special equipment to be used for such carriage (ATP). UNECE Transport Committee, Geneva.
  15. WALDRON, S. N. and PEARCE, I. A., (1998) The application of synthetic liquid cryo, the distribution, storage and production of food. HR Conference, Refrigerated tra; storage and retail display, Cambridge, 1998. IIR, Paris.

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