3.5. Retail refrigeration cabinets

One of the most common types of granular ice is flake ice, which is obtained by freezing water onto the surface of a rotating, refrigerated drum (Figure 9). The water freezes into a 2–3-mm-

Storing fish in ice is largely used aboard fishing ships; apart from chilling the fish, ice removes heat from the surrounding structure of the box or storage compartments, absorbs the heat input through the structure from the warm air and sea outside, and removes the heat produced by the spoilage process in the fish themselves [8]. It is therefore essential that plenty of ice is properly distributed throughout the catch to ensure efficient cooling. Ideally, each fish should be in contact only with ice; in practice, there are alternating layers of ice and fish (Figure 10). The ice-to-fish ratio is comprised between 1/3 and 1/1; there should be at least 5 cm thick layers of ice (1, 3) between fish and the compartment walls [8]. In order to avoid the lower layers being damaged under the weight of the upper layers, fish must be placed on shelves, in order to keep the depth

Ice chilling is also used for vegetables and fruits [4]; the products are placed in wooden or cardboard crates, filled with ice. Figure 11 presents the schematics of an ice-filling machine; the ice flakes flow into the machine hopper (2) through the chute (1) and are poured into the crates

This chilling method is used for liquid food products (milk, cream, juices, beer, wine, etc.). Refrigerants or secondary cooling agents are used on the cold side of the chilling device, which

In the batch operation mode, the product fed into the tank is cooled using an external cooling jacket or an internal cooling coil. Figure 12 presents the schematics of a tank equipped with an external cooling jacket (2). The product is fed into the tank through the pipe (7); when the desired final temperature is reached, the product is purged from the tank through the dis-

Figure 9. Production of ice flakes. 1, water tank; 2, rotating refrigerated drum; 3, ice layer; 4, ice flakes; 5, ice chute; 6,

thick layer of ice, which is then scraped off the drum as flakes of ice.

of the storage compartment (2) lower than 0.5 m [8].

3.4. Chilling in tanks and heat exchangers

is operated in batch or continuous mode [4].

through the hopper (4).

52 Refrigeration

charge pipe (5).

scrapper blade.

Retail refrigeration cabinets use cold air circulated through natural or forced convection. The cost of chill storage is high and, in order to reduce costs, large stores may have a centralized plant to circulate the refrigerant to all cabinets; the heat generated by the condensers of the refrigeration system may be used for in-store heating. Computer control of multiple cabinets detects excessive rises in temperature and warns of any requirement for emergency repairs or planned maintenance. Other energy-saving devices include night blinds or glass doors on the front of cabinets to trap cold air.

Figure 12. Chilling tank for batch operation. 1, tank; 2, cooling jacket; 3, coolant inlet; 4, stirrer.

Figure 13. Double pipe heat exchanger. 1, product inlet connection; 2, refrigerant outlet connection; 3, outer shell; 4, inner pipe; 5, flanges; 6, refrigerant inlet connection; 7, product outlet connection.

According to the cabinet geometry, the retail refrigeration cabinets are [10]:


Horizontal refrigeration cabinets (Figure 14) are open-top and are designed for self-service; the wall-site units (Figure 14a) allow shopping from one side, while the island type units (Figure 14b) are accessible from all sides [2, 10].

Figure 14. Horizontal refrigeration cabinets. 1, evaporator coil; 2, thermaly insulated case; 3, product loading space; 4, glass panels; 5, fan.

Figure 15. Vertical open front refrigeration cabinet. 1, 3, 7, fans; 2, 4, evaporator coils; 5, case; 6, 8, air channels; 9, products; 10, grills; a, b, c, air curtains.

According to the cabinet geometry, the retail refrigeration cabinets are [10]:

pipe; 5, flanges; 6, refrigerant inlet connection; 7, product outlet connection.

Figure 13. Double pipe heat exchanger. 1, product inlet connection; 2, refrigerant outlet connection; 3, outer shell; 4, inner

Figure 12. Chilling tank for batch operation. 1, tank; 2, cooling jacket; 3, coolant inlet; 4, stirrer.

• horizontal, single-deck units;

• vertical, multi-deck units.

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Axial fans (6) are used to provide air flow over the evaporator coils (1), and grills placed at the upper side of the cabinet deflect the air current from one side of the cabinet to the other, over the stacked products. Due to cold air stratification, air infiltrations from the environment are relatively low; the heating load is due to the radiant heat transfer and conductive heat transfer through the insulated walls of the cabinet case [10].

Vertical multi-deck units have an open front or are provided with a glass front door [2, 10]. The open front refrigeration cabinets (Figure 15) use air curtains (a, b, c) in order to prevent the infiltrations of warm air into the cabinet. The axial fans (1) and (3) circulate the cold air over the evaporator coils (2, 4) and produce the stream of air necessary for obtaining the inner air curtains; the outer air curtain (c) is generated by the axial fan (7). Grills are used in order to direct the air flow and obtain the air curtains.

The three air curtains form a very complex system, and the proper design imposes an in-depth understanding of the cabinet's fluid dynamics [2].

Some stores are equipped with combination cabinets (Figure 16), comprising an open front vertical cabinet and an open-top, horizontal cabinet [10].

The closed vertical refrigeration cabinets (Figure 17) use a glass door (4) in order to contain the products into the refrigerated space and prevent the infiltration of warm air [10].

Table 1 summarizes some characteristics of the retail display cabinets.

Figure 16. Combination cabinet. 1, vertical, open front, refrigeration cabinet; 2, 5, fans; 3, 6, evaporator coils; 4, horizontal, open type, refrigeration cabinet.

Food Chilling Methods and CFD Analysis of a Refrigeration Cabinet as a Case Study http://dx.doi.org/10.5772/intechopen.69136 57

Figure 17. Vertical, closed, refrigeration cabinet. 1, evaporator; 2, case; 3, product shelves; 4, glass door; 5, fan.


Table 1. Characteristics of the retail display cabinets [10].

Axial fans (6) are used to provide air flow over the evaporator coils (1), and grills placed at the upper side of the cabinet deflect the air current from one side of the cabinet to the other, over the stacked products. Due to cold air stratification, air infiltrations from the environment are relatively low; the heating load is due to the radiant heat transfer and conductive heat transfer

Vertical multi-deck units have an open front or are provided with a glass front door [2, 10]. The open front refrigeration cabinets (Figure 15) use air curtains (a, b, c) in order to prevent the infiltrations of warm air into the cabinet. The axial fans (1) and (3) circulate the cold air over the evaporator coils (2, 4) and produce the stream of air necessary for obtaining the inner air curtains; the outer air curtain (c) is generated by the axial fan (7). Grills are used in

The three air curtains form a very complex system, and the proper design imposes an in-depth

Some stores are equipped with combination cabinets (Figure 16), comprising an open front

The closed vertical refrigeration cabinets (Figure 17) use a glass door (4) in order to contain the

Figure 16. Combination cabinet. 1, vertical, open front, refrigeration cabinet; 2, 5, fans; 3, 6, evaporator coils; 4, horizontal,

products into the refrigerated space and prevent the infiltration of warm air [10].

Table 1 summarizes some characteristics of the retail display cabinets.

through the insulated walls of the cabinet case [10].

56 Refrigeration

order to direct the air flow and obtain the air curtains.

vertical cabinet and an open-top, horizontal cabinet [10].

understanding of the cabinet's fluid dynamics [2].

open type, refrigeration cabinet.
