Method and apparatus for maintaining a uniform temperature in a refrigeration system

A refrigeration apparatus includes an air chiller, a storage enclosure defining a compartment, a duct system, and a valve system. The air chiller blows chilled air into the duct system. The compartment has a first and a second opening, each of which is coupled to the duct system. The valve system has valves that can be moved to route the chilled air so that it enters into the first opening and exits the second opening, or vice versa. In one implementation, the first opening is at the top of the compartment and the second opening is at the bottom of the compartment, and the valve system is controlled by a control circuit that periodically switches the valves (via an actuator) to change the direction of the chilled air. This effectively maintains a relatively uniform temperature throughout the compartment.

TECHNICAL FIELD

This application relates generally to food and beverage refrigeration and more particularly, to food and beverage refrigeration systems that alter airflow to maintain uniform temperatures.

BACKGROUND

Maintaining a relatively uniform temperature is important in any refrigeration system, but it is particularly important in the context of food and beverage refrigeration. Without proper temperature distribution, some food in a refrigerator will be too cold, resulting in unwanted freezing and some will be too warm, which raises the risk of spoilage. In most contexts, a uniform temperature is not only desirable, but is mandated by regulations. For example, depending upon the aircraft operating authority certain types of food served on passenger airlines is required to be maintained at a maximum temperature of no more than 7° C. and in some countries 4° C.

Typically, pre-prepared airline food is stored in galley carts prior to serving to passengers. However, current galley cooling systems have to force air just above freezing either into the galley carts or into insulated compartments containing several galley carts just to ensure that the temperature does not exceed the required temperature in any portion of the carts. This is due to the temperature increase as the air passes through or over the galley carts to remove the heat entering the galley cart or compartment. The lower maximum temperature requirement of 4° C. means that the current cold air source is less efficient resulting in the need to use more powerful and heavier systems that use more electrical power. Thus, it can be seen that there is a need for a new method and apparatus for maintaining a uniform temperature in a refrigeration system.

SUMMARY

In accordance with the foregoing, a method and apparatus for maintaining a uniform temperature in a refrigeration system is provided. According to an embodiment of the invention, the method involves directing chilled air through a galley cart or compartment in a first direction, switching the flow of the chilled air to a second direction (substantially opposite the first direction), and periodically repeating these steps. In another embodiment, the apparatus includes an air chiller, a storage enclosure defining a compartment, a duct system, and a valve system. The air chiller blows chilled air into the duct system. The compartment has a first and a second opening, each of which is coupled to the duct system. The valve system has valves that can be moved to route the chilled air so that it enters into the first opening and exits the second opening, or vice versa. In one embodiment, the first opening is at the top of the compartment and the second opening is at the bottom of the compartment, and the valve system is controlled by a control circuit that periodically switches the valves (via an actuator) to change the direction of the chilled air. This effectively maintains a relatively uniform temperature throughout the compartment.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a galley cart that is used in conjunction with an embodiment is shown. The cart, generally labeled10, includes an enclosure12and castors14attached to the bottom of the enclosure12. The enclosure12has a front side16and a back side19. A door20is attached to the front side16by hinges22. The enclosure12has a storage compartment24defined by an inner surface26of the door20, a back wall28, a first side wall30, a second side wall32, a ceiling34, and a floor36.

Protruding from the first and second side walls30and32, are rails38, which are configured to hold food trays. The enclosure12also has a divider40attached to the first and second side walls30and32. The divider40is disposed at or about the vertical midway point of the side walls30and32. The divider40has a pair of generally V-shaped cutouts42, one proximate to the door20and one proximate to the back wall28. The back wall28has a pair of generally square openings, a first opening43and a second opening45, in which a first grill44and a second grill46are disposed. The first and second openings43and45link the storage compartment24with the outside of the enclosure12, allowing air to move in or out through the grills44and46.

The first grill44is located proximate to the ceiling34while the second grill46is located proximate to the floor36. The first and second grills44and46permit air to flow through the back wall28.

Referring toFIG. 3, an example of a refrigeration system configured according to an embodiment of the invention will now be described. The system, generally labeled100, includes a cart corral102, an air chiller104disposed on top of the cart corral102, and a duct system106disposed within the cart corral102. The duct system has an inlet108and an outlet110. The air chiller104has an outlet that is coupled to the inlet108of the duct system106. The air chiller104also has an inlet that is coupled to the outlet110of the duct system106.

The duct system106has a main duct112that extends around the inner periphery of the cart corral102. The main duct112starts at the inlet108of the duct system106and terminates at the outlet110of the duct system106.

The cart corral102has an open side114that enables a cart to be parked within the corral102.FIG. 3shows 3 carts, each of the carts being parked within the corral102. Cart10in this example will be assumed to have the same configuration as the cart10ofFIG. 1. Each cart10is parked so that its front side16faces the open side114of the cart corral102.

In addition to the main duct112, the duct system106includes a first branch116and a second branch118. The first branch116has openings120that are next to or coupled with the first openings43of the carts10. Similarly, the second branch118has openings122that are next to or coupled with the second openings45of the carts10.

Disposed within the duct system106is a valve system, which includes a first valve124and a second valve126. The refrigeration system100also includes a control unit128. The control unit128includes a control circuit130, which controls the movement of the first and second valves124and126by sending signals to an actuator that is mechanically coupled to the first and second valves124and126. The first valve124has at least two positions—a first position, shown inFIG. 3, in which the first valve124directs air flowing from the inlet108of the duct system106to flow to the first branch116, and a second position, shown inFIG. 4, in which the first valve124prevents air flowing from the inlet108of the duct system106directly to the first branch116. The second valve126also has at least two positions—a first position, shown inFIG. 3, in which the second valve126prevents air from flowing from the first branch116to the main duct112, and a second position, shown inFIG. 4, in which the second valve126permits air to flow from the first branch116to the main duct112.

The refrigeration system100has at least two modes of operation—a normal airflow mode and a reversed airflow mode. The normal airflow mode will now be described with respect toFIG. 3. In the normal airflow mode, the valve system is in a configuration in which the first valve124and the second valve126are in their respective first positions. The air chiller104blows chilled air into the inlet108of the duct system106. Because the first valve124prevents airflow directly from the inlet108to the main duct112, the air flows from the inlet108to the first branch116, and then flows through openings120of the first branch116and through the first openings43of the carts10. The chilled air flows through the storage compartment24of each cart10, through the generally V-shaped cutouts42, and out the second openings45of the carts10. The chilled air exiting the second openings45passes through the second branch118and proceeds to the main duct112and out the outlet110.

The reverse airflow mode will now be described with reference toFIG. 4. In the reverse airflow mode, the valve system is in a configuration in which the first valve124and the second valve126are in their respective second positions. The first valve124in its second position directs airflow from the inlet108to the main duct112. With the second valve126in its second position, airflow from the main duct112is prevented from flowing directly back to the chiller104through the outlet110. Instead, the air flows from the main duct112into the second branch118, through the openings122of the second branch118, and through the second openings45of the carts10. The chilled air then passes through the storage compartment24of each cart10, through the generally V-shaped cutouts42, and out the first openings43of the carts10. The chilled air exiting the first openings43passes through first branch116and proceeds to the main duct112and back to the chiller104through the outlet110.

According to an embodiment of the invention, the refrigeration system periodically switches from the normal airflow mode to the reverse airflow mode. The time interval for switching the airflow can depend on many factors, such as the desired temperature of the system, and may also depend upon a sensed temperature of the system. This could include, for example, temperature sensors that determine whether there is a difference between the temperature at the top of a cart as compared to the temperature at the bottom of a cart. If such a difference exceeds a particular threshold, the airflow may be switched to provide more uniform cooling. In one implementation, the switching may occur periodically from 2 to 30 minutes. The switching between the normal mode and the reverse mode is controlled by the control circuit130of the control unit128. Periodically reversing the flow of air helps to equalize the temperature throughout the compartment24.

As should be appreciate by one of skill in the art, the foregoing describes an embodiment where 3 different carts are accommodated within the cooling system of the present invention. The same invention may be readily implemented with respect to more or less carts. For example, the invention may be implemented with respect to just one cart, where 2 valve are operated to direct airflow through the cart initially in one direction, then to direct airflow through the cart in the other direction.