EP2715255A1

EP2715255A1 - System and method for cooling a compartmentalized refrigeration enclosure

Info

Publication number: EP2715255A1
Application number: EP11727027.2A
Authority: EP
Inventors: Jean Philippe GOUX; Roland MOTTAL
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2011-06-02
Filing date: 2011-06-02
Publication date: 2014-04-09
Also published as: WO2012166144A1; US20140305147A1; CN103703330A

Abstract

A refrigeration enclosure comprises a cargo box with a partition wall that subdivides the cargo box into compartments. In one embodiment, the refrigeration enclosure includes a refrigeration system with a refrigeration unit for cooling one of the compartments and an air moving device disposed proximate the partition wall to facilitate airflow from the first compartment to the second compartment. The refrigeration system further comprises a control device coupled to each of the air moving device and the refrigeration unit. The control device provides control signals that vary the operation of each of the air moving device and the refrigeration unit in response to variations in the operating conditions (e.g., temperature) inside each of the compartments.

Description

SYSTEM AND METHOD FOR COOLING A COMPARTMENTALIZED

REFRIGERATION ENCLOSURE

BACKGROUND

Technical Field

[0001] The subject matter disclosed herein relates generally to transport refrigeration and, in one embodiment, to a refrigeration enclosure with multiple cargo compartments and a refrigeration system to facilitate variable cooling of the cargo compartments.

Description of Related Art

[0002] Refrigerated cargo containers utilize a refrigeration unit to maintain the interior volume or environment of the cargo container at a desired temperature. A wide variety of products, ranging for example from freshly picked produce to deep frozen seafood, are commonly shipped in refrigerated truck trailers and other refrigerated freight containers. To facilitate shipment under different temperatures, e.g., frozen and non-frozen perishable goods, some cargo containers are compartmentalized into two or more separate cargo compartments.

[0003] Conventional transport refrigeration units include a refrigerant compressor, a condenser, and a main evaporator. When used in connection with compartmentalized refrigerated cargo containers, however, the refrigeration unit is often outfitted with one or more remote evaporators. Such systems are often called "reversible multi-temperature systems" because the temperatures of the various compartments (usually frozen temperatures on a first compartment and fresh temperatures on a second compartment) can be reversed. In exemplary systems, the remote evaporators reside proximate each of the compartments, thereby providing individualized temperature control. Moreover, each evaporator may further consist of an evaporator coil, an expansion device, solenoid valves, a heating system, one or more fans, an optional drain heater, a return air temperature sensor, and a defrost functionality that includes an additional temperature sensor for end-defrost monitoring. Thus, all-in-all the conventional multi-compartment cargo container is complex and costly to construct, install, and operate.

[0004] Alternative configurations of refrigeration units deploy a fan or "bulkhead fan" in place of at least one of the remote evaporators. Systems with the bulkhead fan are "non- reversible multi-temperatures systems," where the forward compartment temperature is lower than the aft compartment temperature. Typically the bulkhead fan is coupled to a locally oriented temperature sensor, i.e., a temperature sensor that senses temperature of only one compartment. The temperature sensor indicates changes in temperature of the cargo compartment, which in turn changes the operation of the bulkhead fan unit.

SUMMARY

[0005] As discussed more below, embodiments of the refrigeration enclosure couples a fan unit to the control structure of the refrigeration unit. This configuration reduces the cost of the multi-component refrigeration system and insures an accurate temperature control in each of the compartments of the compartmentalized refrigeration enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For further understanding of the subject matter, reference is made to the following detailed description, which is to be read in connection with the accompanying drawings, in which:

[0007] FIG. 1 is a top, schematic view of an exemplary embodiment of a refrigeration enclosure having a compartmentalized structure and equipped with a refrigeration system;

[0008] FIG. 2 is a perspective view, partly in section, of the refrigeration enclosure of Fig. 1 in position on a truck;

[0009] FIG. 3 is a schematic diagram of a control diagram for use in controlling a refrigeration system in a refrigeration enclosure such as the enclosure of FIGS. 1 and 2;

[0010] FIG. 4 is a flow diagram of an exemplary method for cooling a refrigeration enclosure such as the enclosure of FIGS. 1 and 2; and

[0011] FIG. 5 is a flow diagram of another exemplary method for cooling a refrigeration enclosure such as the enclosure of FIGS. 1 and 2.

[0012] Where applicable, like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. DETAILED DESCRIPTION

[0013] Figs. 1 and 2 depict an exemplary refrigeration enclosure 100 that is made in accordance with the present disclosure. As best shown in Fig. 1, the refrigeration enclosure 100 includes a cargo box 102 that has a partition wall 104, which subdivides the volume of the cargo box 102 into one or more cargo compartments 106 including a first compartment 108 (or "forward compartment 108") and a second compartment 110 (or "aft compartment 110"). The partition wall 104 has a plurality of openings 112, which facilitate airflow between the forward compartment 108 and the aft compartment 110. Each of the cargo compartments 106 has an access point, generally identified by the numeral 116, in the form of panels and/or doors that provide access into the respective cargo compartment 106 to facilitate loading and unloading of cargo therein.

[0014] The refrigeration enclosure 100 also includes a refrigeration system 118 that regulates the environment within each of the respective cargo compartments 106. The refrigeration system 118 includes a refrigeration unit 120 and an air moving device 122 proximate at least one of the openings 112. Examples of the air moving device 122 include a fan 124 or impeller. In one embodiment, the refrigeration system 118 also includes an airflow regulator 126 (or "air flap 126"), which regulates airflow through one or more of the openings 112. Preferably the air flap 126 permits airflow in only one direction such as from the forward compartment 108 to the aft compartment 110 or vice versa.

[0015] The refrigeration unit 120 includes a condensing unit 128 and a forward evaporator 130 in flow connection with the interior of the forward compartment 108. The condensing unit 128 has a housing 132 that is secured to the exterior of the cargo box 102 as in conventional practice. The housing 132 encases a compressor 134 and a condenser 136, as well as related components which an artisan skilled in the refrigeration art will recognize, and thus details are not necessary.

[0016] The refrigeration system 118 also has a control device 138 and one or more sensors that provide inputs respecting operating conditions (e.g., temperature, pressure, and humidity) inside of the cargo compartments 106. The sensors can include a forward temperature sensor 142 and an aft temperature sensor 144 that are responsive to the cargo temperature of, respectively, the forward compartment 108 and the aft compartment 110. The present example identifies the cargo temperature for the forward compartment 108 as Tp and the cargo temperature of the aft compartment 110 as T_A. In response to the inputs from the sensors 140, the control device 138 generates control signals that selectively control and/or operate, e.g., the fan 124, the condensing unit 128, and/or the forward evaporator 130, as discussed more below.

[0017] Operation of the refrigeration system 118 causes an airflow pattern 146 that defines the movement of air among and between the cargo compartments 106. In one example, the airflow pattern 146 includes an aft flow 148 and a forward flow 150. The former, i.e., the aft flow 148, may result from rotation of the fan 124 drawing air from the forward compartment 108 and dispersing (and mixing) the air into the aft compartment 110. The forward flow 150 describes the flow of air from the aft compartment 110 to the forward compartment 108 to equalize the pressure inside of the aft compartment 110.

[0018] As best shown in Fig. 2, the refrigeration enclosure 100 can be incorporated onto a truck 152 for transport of the cargo stored therein. In one embodiment, a power source (not shown) such as a generator can be coupled to the engine (or drive train) of the truck 152. The power source generates sufficient electrical power required by, e.g., the fan 124 and the compressor 134, as well as other parts of the refrigeration system 118. In one example, the power source comprises a single on-board engine driven synchronous generator that produces at least one AC voltage at one or more frequencies.

[0019] Embodiments of the refrigeration enclosure 100 lend themselves to other transport vehicles. For example, the refrigeration enclosure 100 may be embodied as a refrigerated transport trailer attached to and hauled by a suitably configured tractor (i.e., "tractor trailer") or as a refrigerated freight container of compartmentalized design for transporting perishable product by ship and/or rail and/or intermodally. Moreover, while the discussion of the refrigeration enclosure 100 will focus on the dual-compartment configurations of the cargo box 102, it is to be understood that the variants of the cargo box 102 may have more than two compartments.

[0020] The control device 138 may include a microprocessor board that includes the microprocessor, an associated memory, and an input/output board that contains an analog-to- digital converter. Other configurations are likewise contemplated in which one or more of these devices are combined within a single integrated circuit (e.g., a chip, chip-on-chip package, and the like). The control device 138 may also include drive circuits, field effect transistors ("FET"), relays, and other discrete devices (e.g., transistors, resistors, capacitors) that are arranged to implement control features associated with the refrigeration system 118. In one example, the control device 138 comprises a Micro Link™ controller available from Carrier Corporation, Farmington, Connecticut, USA. However, the particular type and design of the control device 138 is within the discretion of the artisans skilled in the refrigeration arts and familiar with the cooling and refrigeration.

[0021] In one embodiment, the control device 138 operates the refrigeration system 118 in response to various operating parameters including, but not limited to, set points for each of the forward compartment temperature T_F and the aft compartment temperature T_A. These operating parameters may be pre-set or pre-selected such as by factory calibration. Alternative embodiments may permit user initiated changes and/or implementation of specific operating parameters such as might be beneficial to account for variations in the use and operation of the refrigeration enclosure 100 (e.g., based on the ambient temperature of the surrounding environment).

[0022] The operating parameters may distinguish between the temperature of the forward compartment 108 and the aft compartment 110. For example, the forward compartment 108 can be maintained at a temperature suitable for use with frozen items (e.g., perishable frozen foods) and the aft compartment 110 can be maintained at a temperature suitable for use with refrigerated items (e.g., fruits, vegetables, and perishable non-frozen foods). It is not uncommon that the operating parameters will include a first set point from about -18 °C to about -25 °C for the forward compartment temperature T_F and a second set point from about 0 °C to about 12 °C for aft compartment temperature T_A.

[0023] The control device 138 may implement various algorithms to regulate the cargo temperature for each of the forward compartment 108 and the aft compartment 110. The memory may store these algorithms in the form of executable instructions such as software and/or firmware, which are available for execution, e.g., by the microprocessor. In one example, the algorithm compares the input from the sensors 140 (e.g., the forward temperature sensor 142 and the aft temperature sensor 144) to the operating parameters (e.g., set points for each of the forward compartment temperature T_F and the aft compartment temperature T_A). The algorithm initiates the control device 138 to generate one or more control signals which effectuate operation of the components of the refrigeration system 118. In one example, the control signals cause rotation and/or variations in the speed of rotation of the fan 124.

[0024] Activation of the fan 124 mixes air from the forward compartment 108 with air in the aft compartment 110. When the forward compartment temperature is less than the aft compartment temperature, mixing of air acts to lower or "pull-down" the cargo temperature of the aft compartment 110. Pull-down may continue until the aft compartment temperature T_A reaches the desired cargo temperature as, e.g., designated by the set point discussed above. In one example, the algorithm initiates the control device 138 to generate one or more control signals that stop rotation of the fan 124 in response to lowering of the aft compartment temperature T_A to at, about, or near (e.g., within a certain tolerance) the set point for the aft compartment temperature T_A.

[0025] Suitable algorithms can also prioritize operation of the components of the refrigeration system 118. In one example, the algorithm prioritizes cooling of the cargo compartments 106, and in one construction cooling of the forward compartment 108 is prioritized over cooling of the aft compartment 110. That is, the algorithm is configured to first ensure that the forward compartment temperature Tp meets (and/or is within acceptable tolerances of) the set point established for the forward compartment 108. The pull-down of the forward compartment temperature T_F (or "forward pull-down") may require that at least the forward evaporator 130 is active, which provides cooling air to the forward compartment 108. When the forward pull-down is complete (e.g., the forward compartment temperature T_F reaches the set point), then the algorithm may initiate the control device 138 to generate control signals that cause the aft compartment temperature T_A to meet (and/or is within acceptable tolerances of) the set point established for the aft compartment 110. The pulldown of the aft compartment temperature T_A (or "aft pull-down") may require operation of the fan 124, as discussed above. In other examples, the aft pull-down may require simultaneous operation of the fan 124 and the forward evaporator 130 to maintain the forward compartment temperature Tp.

[0026] Referring now to Fig. 3, embodiments of the refrigeration enclosure 100 (Figs. 1 and 2) can implement a variety of hardware configurations to effectuate control of, e.g., the fan 124 and the forward evaporator 130. The example of FIG. 3 provides a schematic diagram of one configuration of hardware platform 200 for use in, e.g., the refrigeration system 118. The hardware platform 200 includes a control device 202 (e.g., the control device 138), which includes a processor 204, a memory 206, and control circuitry 208 configured for general operation of a refrigeration system (e.g., refrigeration system 118). The control circuitry 208 comprises an evaporator control circuit 212, a fan control circuit 214, a condenser control circuit 216, and a sensor circuit 218. In one embodiment, the control circuitry 208 includes a comparator circuit 220 such as for comparing inputs received by the sensor circuit 218 to set points that indentify certain operating conditions for the compartments of the refrigeration enclosure. One or more buses 222 couple together all of these components, allowing each component to communicate with one or more of the other components as necessary.

[0027] The hardware platform 200 further includes sensors 224, which includes a first temperature sensor 226 and a second temperature sensor 228. The hardware platform 200 also includes refrigeration components 230 such as a fan 232, an evaporator 234, and a compressor 236. Examples of the hardware platform 200 may also have a control panel 238, which is coupled to the control device 202, and includes one or more refrigeration system controls such as a first control 240 and a second control 242. When implemented in the refrigeration enclosure 100 of Fig. 1 and 2, the control device 202 effectuates operation of one or more of the refrigeration components 230 such as in response to inputs from the sensors 224 and/or the control panel 238. The comparator circuit 220, of which various configurations are contemplated, indicates deviations in the temperature of the various compartments of the refrigeration enclosure. Deviations may require the control device 202 to generate one or more control signals, which communicate via the buses 222, to change operation of the refrigeration unit (e.g., the fan 232, the evaporator 234, and the compressor 236). The change in operation can change the operating conditions of the compartments.

[0028] At a high level, the hardware platform 200 and its constructive components communicate amongst themselves and/or with other circuits (and/or devices), which execute high-level logic functions, algorithms, as well as firmware and software instructions. Exemplary circuits of this type include, but are not limited to, discrete elements such as resistors, transistors, diodes, switches, and capacitors, as well as microprocessors and other logic devices such as field programmable gate arrays ("FPGAs") and application specific integrated circuits ("ASICs"). While all of the discrete elements, circuits, and devices function individually in a manner that is generally understood by those artisans that have ordinary skill in the electrical arts, it is their combination and integration into functional electrical groups and circuits that generally provide for the concepts that are disclosed and described herein.

[0029] The electrical circuits of the control device 202 can often physically manifest logical operations, which facilitate the changes in operation of the components of the refrigeration unit. These electrical circuits can replicate in physical form an algorithm, a comparative analysis, and/or a decisional logic tree, each of which operates to assign an output (e.g., the control signals) and/or a value to the output (e.g., the control signals) such as to turn the fan 232 on and off, to vary the speed of the fan 232, to activate the evaporator 234, and/or to activate the compressor 236.

[0030] In one embodiment, the processor 204 is a central processing unit (CPU) such as an ASIC and/or an FPGA. The processor 204 can also include state machine circuitry or other suitable components capable of receiving inputs from, e.g. the control panel 238. The memory 206 includes volatile and non-volatile memory and can be used for storage of software (or firmware) instructions and configuration settings. Each of the evaporator control circuit 212, the fan control circuit 214, the condenser control circuit 216, the sensor circuit 218, and the comparator circuit 220 can embody stand-alone devices such as solid-state devices. These devices can mount to substrates such as printed-circuit boards, which can accommodate various components including the processor 204, the memory 206, and other related circuitry to facilitate operation of the control device 202 in connection with its implementation in the refrigeration enclosure.

[0031] However, although FIG. 3 shows the processor 204, the memory 206, the evaporator control circuit 212, the fan control circuit 214, the condenser control circuit 216, the sensor circuit 218, and the comparator circuit 220 as discrete circuitry and combinations of discrete components, this need not be the case. For example, one or more of these components can be contained in a single integrated circuit (IC) or other component. As another example, the processor 204 can include internal program memory such as RAM and/or ROM. Similarly, any one or more of functions of these components can be distributed across additional components (e.g., multiple processors or other components).

[0032] In one embodiment, the control and operation of the fan 232 is integral with the control and operation of the evaporator 234 and the rest of the refrigeration system. Such integration can occur by way of algorithms and proportional-integral-derivative (PID) control schemes. One example of a PID control scheme has a three-term control structure that generates a PID output, which in turn initiates the control signals that vary the operation of the refrigeration components 230. The three-term control structure represents one or more mathematical algorithms in the form of multiple "modules" that can individually (or collectively) contribute to the overall value of the PID output. In the discussion that follows below, an exemplary mathematical algorithm for use in connection with the three-term control structure is presented. It is contemplated, however, that other algorithms are likewise compatible with the scope and spirit of the concepts of the present disclosure.

[0033] By way of example, the modules can include a proportional control module, an integral control module, and a derivative control module. When implemented as a mathematical algorithm, each of the modules provides a "term." Manipulation of the terms (individually or collectively) is effective to modify or change the value of the PID output, and in turn the value of the control signals that the control device 202 delivers to the various components of the refrigeration system. The control signal can, in one example, activate and deactivate, e.g., the fan 232.

[0034] In one embodiment, the PID output is defined in accordance with Equation (1) below: u(t)— P_OUT + I_OUT + D_T OUT Equation (1) where u( t) is a value for the PID output, P_OUT is a proportional term of the PID output, I_OUT is an integral term of the PID output, and D_OUT is the a derivative term of the PID output. As discussed in more detail below, each of the terms corresponds to a gain parameter that is assigned a value in response to inputs from, e.g., the sensors 224 discussed above.

[0035] The proportional term P_OUT, also known as gain and/or the gain term, can change the PID output in proportion to an error value. In one example, the error value defines a change in the temperature of the compartments (e.g., the forward compartment temperature TF and the aft compartment temperature TA). In one example, the proportional term P_OUT is defined in accordance with Equation (2) below:

PQ_UT K p6{f) , Equation (2) where K_p is the proportional gain parameter, e is the error value, and t is time and/or instantaneous time.

[0036] The integral term I_out, also known as reset and/or reset term, can modify the PID output in proportion to both the magnitude of the error value and the duration of the error value over time. In one example, the integral term I_out is defined in accordance with Equation (3) below:

I_OUT = K_t f e(T)dr , Equation (3)

JO in which K_t is the integral gain parameter, e is the error value, t is time or instantaneous time, and T is a dummy integration value.

[0037] The derivative parameter D_ouh also known as rate and/or rate term, can change the PID output based on the rate of change of the error value such as by determining the slope of the error value over time. In one example, the derivative term D_out is defined in accordance with Equation (4) below:

^DOUT = ^Kd -^-e(t) , Equation (4)

at where K_d is the derivative gain parameter, e is the error value, and t is time or instantaneous time.

[0038] In one embodiment, the sum of one or more of the proportional term, the integral term, and the derivative term is used to calculate the value for the PID output (e.g., u(t)) as illustrated in Equation (5) below: u(t) = K e(t) + K_i f e(T)dT + K_d—e(t) . Equation (5)

J^o dt

[0039] Each of the proportional control module, the integral control module, and the derivative control module can be configured as electrical circuitry. Utilizing discrete elements such as resistors and capacitors, processors such as ASICs and FPGAs, as well as combinations of various electrical devices, these modules can effectuate the changes, calculations, determinations the various parameters described above. These elements and components are selected in connection with the relevant theory of PID control and the PID control schemes described herein.

[0040] Fig. 4 depicts a flow diagram for an exemplary method 300 that is useful for cooling a refrigeration enclosure, e.g., the refrigeration enclosure 100 (Fig. 1). The method 300 includes, at block 302, receiving an input and, at block 304, generating a first control signal to change a first operating parameter of the refrigeration enclosure. The method 300 also includes, at block 306, generating a second control signal to change a second operating parameter of the refrigeration enclosure. The method 300 further includes, at block 308, monitoring the first operating parameter and the second operating parameter such as, for example, at block 310, receiving feedback in the form of the inputs (e.g., at block 302).

[0041] In one embodiment, the inputs arise from sensors, e.g., temperature sensors, which monitor the operating conditions (e.g., the environment) in each of the cargo compartments (e.g., the cargo compartments 106). The inputs can be received at the same time, such as when the refrigeration enclosure is configured for concurrent monitoring of each of the forward compartment temperature Tp and the aft compartment temperature T_A. Generally this arrangement forms a feedback loop in which inputs from the sensors are received continually. This feedback loop permits rapid response to changes in the operating parameters. In one example, values for the control signal are set based a change in one or more of the forward compartment temperature Tp and the aft compartment temperature T_. This change may indicate deviation of the respective temperature from, e.g., the set points of the forward compartment 108 and the aft compartment 110. Responsive to this deviation, the first control signal and the second control signal can effectuate operation of, respectively, the forward evaporator 130 and the fan 124.

[0042] Fig. 5 illustrates a flow diagram of another exemplary method 400. The inventors use like numerals to identify like components as between Fig. 4 and Fig. 5, but the numerals are increased by 100. For example, the method 400 includes, at block 402, receiving an input, at block 404, generating a first control signal, at block 406, generating a second control signal and, at block 408, monitoring the operating parameters.

[0043] The method 400 further includes, at block 412, receiving a first input from a first compartment and, at block 414, receiving a second input from a second compartment. The method 400 also comprises, at block 416, comparing the inputs (e.g., the first input and the second input) to a set point such as a first set point and a second set point for, respectively, the first compartment and the second compartment. The method 400 also includes steps for prioritizing operating conditions of the compartments such as, for example, prioritizing the first compartment over the second compartment. In one example, prioritization can occur in the method 400, at block 420, determining whether the first input varies from the first set point. If the first input is different from the first set point, then the method 400 continues to block 404, generating the first control signal. On the other hand, if the first input does not vary from the set point, then the method 400 continues, at block 422, determining whether the second input varies from the second set point. If the second input is different from the first set point, then the method 400 continues to block 406, generating the second control signal.

[0044] The inventors find that prioritizing and selecting between the compartments of the refrigeration enclosure can ensure proper cooling. In one implementation, the forward compartment is maintained at a lower temperature than the aft compartment. This configuration is typical of refrigeration enclosures used for frozen foods (e.g., the forward compartment) and non-frozen foods (e.g., the aft compartment). By coupling the fan and the evaporator to the same control device (e.g., the control device 138) priority can be given to the frozen food compartment. Thus cold air is only drawn from the frozen food compartment when the frozen food compartment is at sufficient temperature, e.g., does not deviate from the set point.

[0045] Where applicable it is contemplated that numerical values, as well as other values that are recited herein are modified by the term "about", whether expressly stated or inherently derived by the discussion of the present disclosure. As used herein, the term "about" defines the numerical boundaries of the modified values so as to include, but not be limited to, tolerances and values up to, and including the numerical value so modified. That is, numerical values can include the actual value that is expressly stated, as well as other values that are, or can be, the decimal, fractional, or other multiple of the actual value indicated, and/or described in the disclosure.

[0046] This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defied by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

What is claimed is:

1. A system for cooling a cargo box, said system comprising:

a refrigeration unit having a compressor, a condenser, and an evaporator in flow connection with a first compartment of the cargo box;

an air moving device in flow connection with a second compartment of the cargo box; a sensor responsive to operating conditions in each of the first compartment and the second compartment; and

a control device coupled to each of the refrigeration unit, the air moving device, and the sensors,

wherein the control device is configured to generate control signals that vary operation of the refrigeration unit and the air moving device in response to deviations between the inputs and operating parameters that define the operating conditions.

2. A system according to claim 1, wherein the sensor is responsive to the temperature of each of the first compartment and the second compartment.

3. A system according to claim 2, wherein the sensor comprises a first temperature sensor responsive to the temperature of the first compartment and a second temperature sensor responsive to the temperature of the second compartment.

4. A system according to claim 1, wherein the control device is configured to prioritize operation of the refrigeration unit and the air moving device.

5. A system according to claim 4, wherein the input from the first compartment is prioritized over the input from the second compartment.

6. A system according to claim 1, wherein the control device implements a PID control scheme that utilizes the temperature of the first compartment and the temperature of the second compartment.

7. A system according to claim 1, wherein the air moving device comprises a fan in flow connection with each of the first compartment and the second compartment.

8. A refrigeration enclosure, comprising: a cargo box having a partition wall subdividing the volume of the cargo box into a first compartment and a second compartment;

a refrigeration unit having an evaporator in flow connection with the first compartment;

an air moving device disposed proximate the partition wall, the air moving device in flow connection with each of the first compartment and the second compartment; and

a control device coupled to each of the refrigeration unit and the air moving device, wherein the control device is configured to generate control signals that vary operation of the refrigeration unit and the air moving device in response to deviations in operating conditions of the first compartment and the second compartment.

9. A refrigeration enclosure according to claim 8, wherein the partition wall comprises a plurality of openings, and wherein the air moving device is disposed in one of the openings and positioned to draw air from the first compartment and disperse the air to the second compartment.

10. A refrigeration enclosure according to claim 9, further comprising an air flap disposed in one of the openings, wherein the air flap permits airflow from the second compartment to the first compartment.

11. A refrigeration enclosure according to claim 8, further comprising sensors disposed in each of the first compartment and the second compartment, wherein the sensors are configured to provide inputs respecting the operating conditions.

13. A refrigeration enclosure according to claim 11, wherein the control device is configured to prioritize the operating conditions of the first compartment over the operating conditions of the second compartment.

14. A refrigeration enclosure according to claim 8, wherein the control device is configured to maintain the first compartment at a temperature that is less than the temperature of the second compartment.

15. A refrigeration enclosure according to claim 8, further comprising an access point for each of the first compartment and the second compartment.

16. A method of cooling compartments in a refrigeration enclosure, said method comprising: receiving an input respecting an operating temperature for each of the compartments of the cargo box;

generating a first control signal in response to the inputs to initiate a first pull down of the operating temperature of the first compartment; and

generating a second control signal in response to the inputs to initiate a second pull down of the operating temperature of the second compartment,

wherein the second pull down disperses air from the first compartment into the second compartment.

17. A method according to claim 16, further comprising prioritizing the first pulldown over the second pull-down.

18. A method according to claim 16, wherein the first control signal indicates that the inputs vary from a set point for the first compartment.

19. A method according to claim 16, wherein the second control signal indicates that the inputs vary from a set point for the second compartment.

20. A method according to claim 16, wherein the operating temperature of the second compartment is at least about 5 °C greater that the operating temperature of the first compartment.