Patent Description:
Refrigerated trucks, trailers, and containers are commonly used to transport perishable cargo, such as, for example, produce, meat, poultry, fish, dairy products, cut flowers, pharmaceuticals and other fresh or frozen perishable products. Conventionally, transport refrigeration systems include a trailer refrigeration unit having a refrigerant compressor, a condenser with one or more associated condenser fans, an expansion device, and an evaporator with one or more associated evaporator fans, which are connected via appropriate refrigerant lines in a closed loop refrigerant circuit. Air or an air/gas mixture is drawn from the interior volume of the cargo box by means of the evaporator fan(s) associated with the evaporator, passed through the airside of the evaporator in heat exchange relationship with refrigerant whereby the refrigerant absorbs heat from the air, thereby cooling the air. The cooled air is then supplied back to the cargo box.

The components of the trailer refrigeration unit must be powered during transit by an onboard power source. In existing systems, the onboard power source typically comprises a diesel engine operable to drive the compressor. A liquid coolant system including a radiator is normally used to pass heat from the engine to ambient. Since it is desirable to reduce emissions by eliminating the use of such an engine, refrigeration units powered by electric sources are being developed. Although a fuel cell may provide a viable option as a power source, difficulties arise with dissipating the waste heat generated by the fuel cell, especially in high temperature ambient conditions.

<CIT> discloses a refrigeration system comprising an electrically powered trailer refrigeration unit including a refrigeration circuit, which is supplied with electrical energy by a fuel cell. <CIT> and <CIT> also disclose electrically powered transportation refrigeration units.

According to an embodiment of the present invention there is provided a refrigeration system as set out in independent claim <NUM>.

Optionally, a first end of both the condenser and the radiator is positioned adjacent to a front of the housing.

Optionally, the condenser and the radiator are stacked along a vertical axis.

Optionally, the condenser is arranged above the radiator along the vertical axis.

Optionally the condenser is arranged below the radiator along the vertical axis.

Optionally, the condenser and the radiator are stacked along a horizontal axis.

Optionally, the condenser is arranged left of the radiator along the horizontal axis.

Optionally, the condenser is arranged right of the radiator along the horizontal axis.

Optionally, a depth of the radiator is equal to or less than the depth of the condenser.

Optionally, the coolant circuit is arranged in fluid communication with the fuel cell.

Optionally, the fuel cell is arranged at least partially within the housing.

Optionally, the radiator further comprises a plurality of radiator coils arranged in series relative to the flow of unconditioned ambient air.

Optionally, the trailer refrigeration unit further comprises a condenser fan assembly arranged in fluid communication with both the condenser and the radiator.

Optionally, a temperature of the coolant at the outlet of the radiator is controlled via at least one of a flow rate of the coolant and a speed of the condenser fan assembly.

The condenser and the radiator may be arranged in parallel relative to a flow of unconditioned ambient air.

A detailed description of one or more embodiments of a refrigeration system is presented herein by way of exemplification and not limitation with reference to the Figures.

With reference now to <FIG>, an exemplary transport refrigeration system <NUM> is illustrated. In the illustrated, non-limiting embodiment, the transport refrigeration system <NUM> is shown as a trailer system. As shown, the refrigerated container system <NUM> includes a cargo container or trailer <NUM> being towed or otherwise transported by a tractor <NUM> including an operator's compartment or cab <NUM> and also including an engine or other power source, such as a fuel cell for example, which acts as the drivetrain system of the system <NUM>. A trailer refrigeration unit <NUM> is configured to maintain cargo located within the container <NUM> at a selected temperature by cooling the cargo space of the container <NUM>. As shown, the trailer refrigeration unit <NUM> is typically mounted at the front wall <NUM> of the container <NUM>. Together, the trailer refrigeration unit <NUM> and the cargo container <NUM> may form a refrigerated container system. It should be appreciated by those of skill in the art that embodiments described herein may be applied to any transport refrigeration system such as, for example shipping containers that are shipped by rail, sea (via a watercraft), or any other suitable container, without use of a tractor <NUM>.

With reference now to <FIG>, a schematic diagram of an exemplary trailer refrigeration unit <NUM> is illustrated. The trailer refrigeration unit <NUM> includes a compressor <NUM>, a heat rejection heat exchanger or condenser <NUM>, an expansion valve <NUM>, and a heat absorption heat exchanger or evaporator <NUM>. During operation of the trailer refrigeration unit <NUM>, refrigerant R enters the compressor <NUM> and is compressed to a higher temperature and pressure. From the outlet of the compressor <NUM>, the refrigerant gas is then provided to the condenser <NUM>. The condenser <NUM> is an air cooled condenser such that a flow of air across the condenser coils <NUM> cools the refrigerant gas R to its saturation temperature. By removing latent heat, the refrigerant gas within the condenser <NUM> condenses to a high pressure/high temperature liquid. The air flow across the condenser <NUM> is energized by a condenser fan assembly <NUM> including one or more fans <NUM>, such as two fans for example. As shown, each fan <NUM> may be driven by a separate fan motor <NUM>.

In a trailer refrigeration unit <NUM> having a basic vapor compression cycle, the flow output from the condenser <NUM> is provided directly to a thermostatic expansion valve <NUM> and evaporator <NUM>. As the liquid refrigerant R passes through the orifice of the expansion valve <NUM>, some of it vaporizes into a gas. Return air from the refrigerated space flows over the heat transfer surface of an evaporator <NUM>. As refrigerant flows through tubes <NUM> in the evaporator <NUM>, the remaining liquid refrigerant R absorbs heat from the return air, and in so doing, is vaporized. The air flow across the evaporator <NUM> may be energized by an evaporator fan assembly <NUM> including at least one fan <NUM> and a corresponding fan motor <NUM>. From the evaporator <NUM>, the vapor then flows through a suction modulation valve <NUM> back to an inlet of the compressor <NUM>. In an embodiment, a thermostatic expansion valve bulb or sensor (not shown) is located at an evaporator outlet tube. The bulb is intended to control the thermostatic expansion valve <NUM>, thereby controlling refrigerant superheating at the evaporator outlet tubing.

In the illustrated, non-limiting embodiment, the trailer refrigeration unit <NUM> includes a plurality of components arranged between the condenser <NUM> and the expansion valve <NUM>. As shown, a receiver <NUM> is arranged directly downstream from the outlet of the condenser <NUM>. The receiver <NUM> is configured to provide storage for excess liquid refrigerant during low temperature operation. From the receiver <NUM>, the liquid refrigerant R may pass through a subcooler heat exchanger <NUM>. The subcooler <NUM> may be arranged in-line with and downstream from the condenser <NUM> such that the air flow from the fan assembly <NUM> moves across the condenser <NUM> and the subcooler <NUM> in series. In an embodiment, at the outlet of the subcooler <NUM>, the refrigerant R is provided to a filter dryer <NUM> that keeps the refrigerant cool and dry, and in some embodiments to a heat exchanger <NUM> that increases the refrigerant subcooling. In such embodiments, the refrigerant provided at the outlet of this heat exchanger <NUM> is delivered to the thermostatic expansion valve <NUM>.

The trailer refrigeration unit <NUM> includes a power source <NUM> that is capable of powering all of the electric components of the trailer refrigeration unit <NUM>. Such components include, but are not limited to the electric motor associated with the compressor <NUM>, and the fan motors <NUM>,<NUM> associated with both the condenser <NUM> and the evaporator <NUM> fan assemblies <NUM>, <NUM>. The power source <NUM> may include a single fuel cell, or alternatively a plurality of fuel cells, suitable to provide enough power for all of the dynamic components of the trailer refrigeration unit <NUM>. In an embodiment, the fuel cell provides AC power as needed. The power source <NUM> may be located remotely from the remainder of the trailer refrigeration unit <NUM>, or alternatively, may be arranged within the housing <NUM> (<FIG>) of the trailer refrigeration unit <NUM>.

A controller <NUM>, such as a microprocessor, may be programmed to control power usage and the operation of various electrically powered components within the system <NUM>. For example, the controller <NUM> may be operable to regulate the power supplied to the condenser fan motors <NUM> and the evaporator fan motors <NUM>. Programming such controllers is within the skill in the art.

The power source <NUM> operable to drive the compressor <NUM> and the other electric components of the trailer refrigeration unit <NUM> typically requires some method of cooling to prevent excessive temperature therein. In conventional refrigeration units, such as units where the power source is an internal combustion engine, a coolant circuit including a radiator fluidly coupled with the power source is positioned directly behind the condenser coil such that when the condenser fan assembly is driven, the cooling air flows through the condenser and the radiator in series. Accordingly, the cooled coolant output from the radiator is typically returned to the power source to remove further heat therefrom. However, when such a configuration is used to cool a power source <NUM> including one or more fuel cells in an environment having a high ambient temperature, such as above about <NUM>, about <NUM>, about <NUM>, or even about <NUM> for example, the radiator may not be capable of rejecting a sufficient amount of heat. This may force the fuel cell to operate at limited power (i.e., to reduce heat generation) in order to avoid overheating the fuel cell.

In an embodiment, the controller <NUM> is operable to control the temperature of the coolant provided at the outlet of the radiator <NUM>, such as by controlling a flow rate of the coolant and/or by controlling a speed of the condenser fan <NUM>. With reference now to <FIG>, in the illustrated, non-limiting embodiment of the trailer refrigeration unit <NUM>, a radiator <NUM> is arranged in parallel with the condenser <NUM> relative to the flow of air driven by the one or more condenser fans <NUM>. In the illustrated, non-limiting embodiment, the radiator <NUM> is part of a high-temperature cooling loop. However, the transport refrigeration unit <NUM> may additionally include at least one radiator <NUM> associated with a low-temperature cooling loop. In an embodiment, the one or more axial condenser fans <NUM> aligned about a horizontal axis is positioned within the housing <NUM>, downstream from both the condenser <NUM> and the radiator <NUM> such that the condenser fans <NUM> have a draw-through configuration.

As shown in <FIG>, a first end <NUM>, <NUM> of each of the condenser <NUM> and the radiator <NUM>, respectively, is arranged at or adjacent to a front end <NUM> of the housing <NUM> of the trailer refrigeration unit <NUM> such that a flow of ambient air A is provided directly thereto. In the illustrated, non-limiting embodiment shown in <FIG> and <FIG>, the condenser <NUM> and the radiator <NUM> are stacked relative to one another along a vertical axis (e.g., side-by-side, in parallel). Although the condenser <NUM> is shown as being positioned above the radiator <NUM>, it should be understood that embodiments where the condenser <NUM> is positioned beneath the radiator <NUM> are also contemplated herein.

In another embodiment, illustrated in <FIG>, the condenser <NUM> and the radiator <NUM> are stacked relative to one another along a horizontal axis (e.g., side-by-side, in parallel). Although the condenser <NUM> is illustrated as being positioned generally adjacent a left side <NUM> of the housing <NUM> and the radiator <NUM> is illustrated as being positioned generally adjacent to a right side <NUM> of the housing <NUM>, embodiments where the radiator <NUM> is near the left side <NUM> of the housing <NUM> and the condenser <NUM> is near the right side <NUM> of the housing <NUM> are also within the scope of the present invention.

With reference now to <FIG>, in yet another embodiment, the radiator <NUM> may include a plurality of coils, and the condenser <NUM> may be arranged centrally (either vertically or horizontally) between a first and second radiator coil such that air flow is provided to each of the condenser and the first and second radiator coils <NUM> in parallel. Further, it should be understood that embodiments where the condenser <NUM> is separated into a first portion and a second portion, and the radiator <NUM> is disposed centrally (either vertically or horizontally) between the first and second portion, respectively are also contemplated herein.

Because at least one dimension, such as the height, or alternatively, the width (measured between the left and right sides <NUM>, <NUM> of the housing <NUM>) of each of the condenser <NUM> and the radiator <NUM> has been significantly reduced compared to prior art systems, another dimension of the condenser <NUM> and the radiator <NUM> may be increased to achieve a necessary heat exchange surface area. In an embodiment, a depth of both the condenser <NUM> and the radiator <NUM> has been extended to achieve the required surface area. The total depth of the condenser <NUM> and the radiator <NUM> may be determined in part by the constraints of the available space within the housing <NUM> of the trailer refrigeration unit <NUM><NUM>.

Further, the radiator <NUM> may include a single radiator coil, or in some embodiments, may include a plurality of radiator coils fluidly coupled to one another and arranged in series relative to the air flow A. Although the depth of the condenser <NUM> and the total depth of the one or more radiators <NUM> may be the same, as shown in <FIG>, embodiments where the depth of the radiator <NUM> is different than the depth of the condenser <NUM>, such as less than the depth of the condenser <NUM> for example, are also contemplated herein.

A refrigeration unit having both a condenser <NUM> and a radiator <NUM> positioned to receive a direct flow of unconditioned, ambient air will increase the ability of the radiator <NUM> to reject heat. This enhanced heat rejection will allow for operation of the refrigeration unit, and specifically of the fuel cell power source during higher ambient temperature conditions.

The term "about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the present invention.

Claim 1:
A refrigeration system (<NUM>) comprising:
a trailer refrigeration unit (<NUM>) including a housing (<NUM>), and a refrigerant circuit through which a refrigerant is circulated, the refrigerant circuit including a condenser (<NUM>);
a fuel cell configured to generate electrical power for the trailer refrigeration unit (<NUM>); and
a coolant circuit;
characterized in that the coolant circuit includes a radiator (<NUM>), the radiator (<NUM>) configured to dissipate heat generated by the fuel cell, wherein the condenser (<NUM>) and the radiator (<NUM>) are positioned such that each of the condenser (<NUM>) and the radiator (<NUM>) receives a flow of unconditioned ambient air;
the condenser (<NUM>) and the radiator (<NUM>) are positioned within the housing (<NUM>); and
the trailer refrigeration unit (<NUM>) further comprises at least one condenser fan (<NUM>) operable to move the flow of unconditioned ambient air across the condenser (<NUM>) and the radiator (<NUM>).