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 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 air across the evaporator coil cooling the air and forcing it out into the container.
The cooled air in typical container system is forced out of the refrigeration unit and along a floor of the container. As the cooled air travels away from the refrigeration unit, its temperature increases and it rises in the container and eventually returns to the refrigeration unit. This circulation of cool air from one end of the container to the other end and back again results in uneven cooling of the cargo in the container, since the air forced into the container gets warmer as it travels farther from the refrigeration unit. Further, the cargo positioned at a lower portion of the container will benefit more form the cooling flow than the cargo positioned at an upper portion of the container.
Additionally, the typical refrigeration system for a container is costly and occupies a large amount of space that would otherwise be available for loading cargo.
In one embodiment, a refrigerated cargo container includes a cargo container and a refrigeration unit. A plurality of refrigerant tubes are in fluid communication with the refrigeration unit and extend along a roof of the cargo container. The plurality of refrigeration tubes are configured to convey refrigerant there through and cool an interior of the cargo container via natural convection and thermal radiation.
In another embodiment, a method of cooling a cargo in a cargo container includes flowing a refrigerant through a plurality of refrigerant tubes disposed at a roof of the cargo container. Thermal energy is transferred from container air in the container to the refrigerant thereby cooling the container air. The container air is circulated via natural convection toward the cargo thereby cooling the cargo via thermal energy transfer to the container air. The container air is recirculated toward the plurality of refrigerant tubes.
In yet another embodiment, a method of heating a cargo in a cargo container includes heating a flow of refrigerant located in a plurality of tubes. The flow of refrigerant is circulated through the plurality of tubes at the cargo container. Thermal energy is transferred from flow of refrigerant to container air in the container thereby heating the container air, and the container air is circulated via natural convection toward the cargo thereby heating the cargo via thermal energy transfer from the container air. The container air is recirculated toward the plurality of tubes.
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
Instead of a traditional evaporator of the typical cargo container refrigeration unit, the container 10 includes a plurality of refrigerant tubes 32 located at the roof 30 of the container 10, formed of highly thermally conductive material such as an aluminum or copper material. The plurality of refrigerant tubes 32 are connected to the expansion valve 20 and the compressor 16 of the refrigeration unit 14, and convey a flow of refrigerant 34 throughout the refrigerant tubes 32 from the expansion valve 20 to the compressor 16. The refrigerant tubes 32 extend along a length 36 of the roof 30 from a header 38. The refrigerant tubes 32 may be substantially straight, or alternatively as shown in
Referring now to
Referring again to
In a traditional refrigerant unit there is no radiative effect for cooling or heating. In the unit 14 the entire roof 30 and sidewall 26 surface is in visible contact with the cargo 12 and the thermal radiant cooling effect is very significant. The radiant effect does not involve air but relies on changing the motion of charged particles of matter. As long as the radiative surface (the plurality of tubes 32 and roof 30) has a direct path to the cargo 12, the radiant effect can be a large percentage of the overall cooling capacity. This method is typically small in traditional “forced air” designs.
In some embodiments, in addition to providing cooling, the refrigerant tubes 32, such as those located in the floor 28 of the container 10 are used to provide heating to the cargo 12. In such embodiments, the unit 14 conveys hot gas from the compressor 16 to the evaporator refrigerant tubes 32 to heat the refrigerant therein. The refrigerant 32 then is flowed through the tubes 32 and transfers thermal energy to the cargo 12, thus heating the cargo 12. Heating of the cargo as described herein may be required when the ambient temperature is very low and the cargo 12 requires a set point above the ambient temperature.
As shown in the side view of
Integrating refrigerant tubes 32 into the roof 30 and/or other elements of the container 10 saves cost and reduces complexity of the container 10 and refrigeration unit 14 through elimination evaporator fan of a typical refrigeration unit, and related components. Further, due to the airflow being driven primarily by natural convection, power consumption of the refrigeration unit is reduced. Additionally, since the refrigerant tubes 32 extend over the length of the container 10, cooling from the refrigeration unit 14 is more evenly distributed from end to end of the container 10, as compared to the conventional container where cooling air is forced into the container only from one end of the container and warms along the length of the container.
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/US2013/035906 | 4/10/2013 | WO | 00 |
Number | Date | Country | |
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61658100 | Jun 2012 | US |