The subject matter disclosed herein relates to refrigeration systems. More specifically, the subject matter disclosed herein relates to refrigeration of containers utilized to store and ship cargo.
A typical refrigerated cargo container, such as those utilized to transport a cargo via sea, rail or road, is a container modified to include a refrigeration unit located at one end of the container. The refrigeration unit includes a compressor, condenser, expansion valve and evaporator coil, all located at the end of the container. A volume of refrigerant circulates throughout the refrigeration unit, and one or more evaporator fans of the refrigeration unit blow a flow of supply air across the evaporator coil cooling the supply air and forcing it out into the container.
The supply air flow in many applications is subject to stringent temperature requirements. For example, it may be necessary to provide supply air in a range of +/−0.25° Celsius. To meet such requirements, the compressor of the refrigeration unit is often a variable speed compressor, and supply air temperature is varied and controlled by changing speed of the compressor. Use of variable speed compressors, however, still often results in supply air temperature fluctuation and temperature undershoot that is unacceptable to customers shipping very temperature sensitive cargo. Alternatively, other compressor modulating schemes are utilized, such as suction modulation or the use of a digital compressor. Variable speed or digital compressors are costly, and relatively inefficient.
In one embodiment, a transportation cargo refrigeration system includes a refrigeration unit to provide a flow of supply air for a refrigerated cargo container. A refrigeration system outlet allows the flow of supply air into the cargo container. A mixing chamber is located between the refrigeration unit and the refrigeration system outlet for mixing of the flow of supply air thereby reducing supply air temperature fluctuation at the refrigeration system outlet.
In another embodiment, a method of operating a refrigeration system for a refrigerated cargo container includes flowing air through a refrigeration unit thereby reducing a temperature of the supply air. The supply air is directed into a mixing chamber and mixed in the mixing chamber until a selected supply air temperature is achieved. The supply air is directed through a refrigeration system outlet and into an interior of a cargo container.
In yet another embodiment, a refrigerated transportation cargo container includes a transportation cargo container and a refrigeration unit to provide a flow of supply air for the transportation cargo container. A refrigeration system outlet allows the flow of supply air into the transportation cargo container. A mixing chamber is located between the refrigeration unit and the refrigeration system outlet for mixing of the flow of supply air thereby reducing supply air temperature fluctuation at the refrigeration system outlet.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawing.
Shown in
Referring to
During operation of the refrigeration unit 14, the compressor 16 is cycled “on” and “off” for cost efficient compressor capacity modulation. When the compressor 16 is cycled on/off, however, there may be a high degree of fluctuation in the supply air 38 temperature, since the supply air produced while the compressor 16 is on is of significantly lower temperature than the supply air 38 produced when the compressor 16 is off. To reduce the fluctuation in temperature prior to being urged through the refrigeration unit outlet 30, the supply air 38 is held in a mixing chamber 40 upstream of the outlet 30. The mixing chamber 40 may be located at a lateral side of the refrigeration unit 14 as shown, or alternatively at any other suitable location between the refrigeration unit 14 and an interior of the container 10.
Referring to
Another embodiment is shown in
Mixing of the supply air 38 in the mixing chamber 40, and in some embodiments mixing the supply air 38 with a flow of return air 28 in the mixing chamber 40 reduces temperature fluctuation of the supply air 38 when it reaches the interior of the container 10. Reduced temperature fluctuation reduces risk to and damage to temperature sensitive cargo 12. Further, the reduction in temperature fluctuation is achieved through flow mixing in the mixing chamber 40, rather than through modulation at, or changing operation of the compressor 16. The compressor 16 in the embodiments described herein is operated only in either an “on” position or an “off” position, without costly and relatively inefficient variable operating speeds or other modulation.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US2013/029485 | 3/7/2013 | WO | 00 |
Number | Date | Country | |
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61645199 | May 2012 | US |