WO2012020098A2

WO2012020098A2 - An automated container refrigeration system

Info

Publication number: WO2012020098A2
Application number: PCT/EP2011/063865
Authority: WO
Inventors: Morten Rene Baerentz
Original assignee: A.P. Møller - Mærsk A/S
Priority date: 2010-08-11
Filing date: 2011-08-11
Publication date: 2012-02-16
Also published as: WO2012020098A3

Abstract

An automated container refrigeration system for a container comprising a transport volume. A cooling unit is configured to control air temperature within the transport volume by discharging cooled air with a supply air temperature into the transport volume in accordance with control signals supplied by a temperature control system. A first temperature probe is insertable into fruit pulp of a commodity load arranged within the transport volume, wherein the first temperature probe is operatively connected to the temperature control system for supplying a load temperature thereto. The temperature control system is adapted to adjust the supply air temperature over time so that the load temperature follows a predetermined temperature profile.

Description

AN AUTOMATED CONTAINER REFRIGERATION SYSTEM

The present invention relates to an automated container refrigeration system adapted to controlling a temperature of a commodity load in response to probe temperature data and a corresponding method of controlling the temperature of the commodity load in response to probe temperature data.

BACKGROUND OF THE INVENTION

Cold treatment is one very useful application of the present invention. Cold treatment protocols are applied to kill unwanted pests in or on a container carried commodity load such as fruit or vegetables before arrival at the destination port and country. Cold treatment protocols vary by commodity type and the relevant national agricultural authority. The USDA has a leading role in specification work related to cold treatment protocols. Cold treatment protocols generally comprise lowering the temperature of the commodity load arranged within a transport volume of the container to a predefined temperature for a specified time period or treatment time. The predefined temperature of the commodity load is often required to be below 2.2 degree Celsius for the entire treatment time which may be between 10 and 20 days. The cold treatment protocol is preferably applied to the commodity load during shipment of the container between a departure port and a destination port or harbor.

Prior art container refrigeration methods and systems for temperature control of commodity loads in refrigerated containers have relied on manual monitoring and intervention in the cold treatment protocol in response to temperature deviations. Probe temperature data measured by a number of temperature probes embedded in the commodity load inside the container have been transmitted from the ship or vessel by e-mail (via a satellite link) to an on-shore situated control room. An operations manager situated in the onshore control room has previously monitored the received probe temperature signals or data from the refrigerated container carried on the vessel. The operations manager has been responsible for identifying temperature deviations and taking appropriate corrective actions if measured probe temperature or temperatures deviated from the target or intended

temperature profile associated with the particular cold treatment protocol in question. The information specifying required corrective action(s) has been forwarded via fax or e-mail message through the satellite link to the Captain of the vessel. The Captain has in turn been required to contact his chief officer, or an on-board technician, who manually entered the new set-point temperature in a control panel of the cooling unit on the container in question.

WO 2008/027028 discloses a system and a method of providing automatic temperature control to apply cold treatment to harvested produce. The method includes steps that iteratively transition between different sets of cold treatment criteria in pursuit of compliance with a cold treatment protocol. The system is configured with a cooling device to output a flow of cold air within e.g. a freight container. The cold air circulates to function as a coolant and returns to the cooling device. Temperature sensing devices provide respective measurements that are communicated to the cooling device which may take actions thereon. The cooling device may be loaded with cold treatment rules.

However, there exists a need in the art for container refrigeration systems and control methods therefore which provide improved load temperature control. The present invention is capable of providing container refrigeration systems and corresponding control methods where human caused delays and errors in detecting and responding to temperature deviations between a predetermined temperature profile and an actual load temperature

measurement are eliminated or at least significantly reduced by adapting automated control strategies. The present invention provides automated load temperature control in container refrigeration systems during transportation so as to speed-up detection and appropriate correction of unwanted temperature deviations. Thus, allowing freight carriers to minimize

temperature deviations between a predetermined desired temperature profile and actual load temperature. In connection with cold treatment procedures, the present invention allows setting a treatment setpoint temperature very close to a specified protocol temperature of the cold treatment protocol in question due to the improved responsiveness of the present container refrigeration systems.

SUMMARY OF INVENTION

A first aspect of the invention relates to an automated container refrigeration system comprising a container comprising a transport volume. A cooling unit is configured to control air temperature within the transport volume by discharging cooled air with a supply air temperature into the transport volume in accordance with control signals supplied by a temperature control system. A temperature probe is insertable into fruit pulp of a commodity load arranged within the transport volume. The temperature probe is operatively connected to the temperature control system for supplying a load

temperature thereto. The temperature control system is adapted to adjust the supply air temperature over time so that the load temperature follows a predetermined temperature profile. The temperature control system is preferably programmable and comprises a processor, such as a microprocessor and/or digital signal processor, operating in accordance with a set of program instructions held in a program memory area of microprocessor. The control signals supplied by the temperature control system may therefore be defined by the set of program instructions. The control signals are suitable to individually control the operation of one or more components of the cooling unit such as compressor(s), heater(s) evaporator fan(s) and economizers) such that the supply air temperature has an appropriate value for reaching the desired air temperature inside the transport volume. Control signal supplied to the evaporator fan(s) may switch an evaporator speed between a number of preset settings such as HIGH/LOW/OFF. The load temperature, which is indicative of the fruit pulp temperature, generally follows the air temperature within the transport volume to a certain extent depending on factors such as a heat capacity of the commodity load, a rate of change of the supply air temperature, temperature gradients within the transport volume etc.

The temperature control system may be adapted to adjust the supply air temperature in up-going or down-going steps of a predetermined size such as size between 0.05 and 0.45; 0.05 and 0.45; or 0.1 and 0.5 degree C, preferably between 0.1 and 0.3; or 0.1 and 0.2 degrees C in a way that counteracts a detected deviation between a target or desired temperature, specified by the predetermined temperature profile, and a measured load temperature. The supply air temperature may be adjusted in such small steps and the impact on the load temperature measured or monitored over a predetermined time period such as a few hours by the temperature control system. If a first step was insufficient to reach the desired load temperature, another temperature increment or decrement of the supply air temperature in the same direction may be taken and its effect monitored again and so on until the load temperature follows the predetermined temperature profile with narrow temperature limits.

The temperature probe may be any commercially available or proprietary temperature probe shaped and sized to be inserted into the fruit pulp of the commodity load. Suitable commercially available temperature probes are available from the manufacturer DANFOSSunder trade names such as NTC or PT100 temperature probes. The operative connection between the temperature probe and temperature control system may be established by a wired connection, such as a data cable, or a wireless communication channel operating according to a standardized or proprietary digital communications protocol such as Bluetooth etc. The load temperatures measured by the temperature probe are preferably encoded as digital data before transmission to the temperature control system. Current or updated load temperatures may be transmitted to the to the temperature control system at regular time intervals, such as every second, every 30 seconds or every minute or at even longer intervals. The current or updated load temperature may be transmitted voluntarily by the temperature probe at preset intervals or in response to a request from the temperature control system, i.e. by polling the temperature probe.

According to a preferred embodiment of the invention, the predetermined temperature profile comprises:

- a first segment with gradually decreasing load temperature over time until a treatment setpoint temperature is reached,

- a second segment where the load temperature is maintained at the treatment setpoint temperature over a predetermined treatment time period. Optionally, a third segment with gradually increasing air temperature over time until the load temperature reaches a final setpoint temperature may be added. The predetermined temperature profile in accordance with these embodiments of the invention is particularly suitable for cold treatment of fruits of the commodity or cargo load according to various cold treatment protocols.

The cold treatment protocols generally vary by fruit type and country of origin or destination. Cold treatment protocols often specify a treatment time period together with an associated protocol temperature. The fruit pulp temperature must be at or below the specified protocol temperature for the entire treatment time period to comply with the cold treatment protocol in question. In accordance with the present embodiment, the load temperature may be maintained at the treatment setpoint temperature over the predetermined treatment time period to ensure compliance with the relevant cold treatment protocol. The treatment setpoint temperature generally stays fixed through the entire predetermined treatment time period and may be set to a value slightly below the specified protocol temperature for the commodity load in questions such as between 0.2 and 0.6 degree C below the specified protocol temperature.

Claim 3: While cold treatment protocols, as mentioned above, generally require the fruit pulp temperature to be at or below the specified protocol temperature, there is not any official lower limit for the fruit pulp temperature. However, to avoid chill damage to the fruit of the commodity load, it is highly desirable to avoid lowering the fruit pulp temperature more than strictly necessary to ensure compliance with the cold treatment protocol in question. An advantageous embodiment of the invention therefore comprises setting the treatment setpoint temperature, during the second segment, a

predetermined amount below the protocol temperature specified by the relevant agricultural authority for the commodity load where the

predetermined amount lies between 0.1 and 0.6 degree Celsius, or even more preferably between 0.2 and 0.5 degree Celsius. The temperature control system therefore adjusts the supply air temperature to obtain a treatment setpoint temperature that is only slightly lower, e.g. between 0.2 and 0.5 degree Celsius, than the protocol temperature. The temperature probe provides the temperature control system with load temperature data to adjust the supply air temperature accordingly in manner where a substantially constant load temperature at, or close to, the treatment setpoint temperature is maintained during the predetermined treatment time period. The

temperature control system may be adapted to control the load temperature so it follows the treatment setpoint temperature within certain temperature limits. These temperature limits may for example be less than +/- 0.4 degree C, or less than +/- 0.2 degree C, from the treatment setpoint temperature so as to allow accurate control of the load temperature within these limits. By accurately controlling the load temperature within such narrow temperature limits around the treatment setpoint temperature, the predetermined temperature amount may be set to a small value as outlined above allowing the load temperature to stay just beneath the protocol temperature.

The automated operation of the present temperature control system is therefore very effective in preventing chilling damage to fruit of the

commodity load due to significantly improved responsiveness to unwanted temperature deviations between the measured load temperature and the treatment setpoint temperature.

The temperature control system or certain portions thereof may be arranged internally within the cooling unit or externally to the cooling unit for example on board the vessel or at shore. In an external temperature control system, the system may comprise a remote processor, such as a processor of a computer server located on-vessel or inside an on-shore control center, coupled to the cooling unit through a bi-directional data communication link. The remote processor is programmed or adapted to generate the control signals based on load temperatures received through the bi-directional data communication link. In the latter embodiment, the speed of modern communications networks such as cellular networks, switched telephone networks and TCP/IP based data networks, is utilized by the external temperature control system to adjust the supply air temperature without any noticeable delay. However, in certain applications it may be advantageous to locate the processor of the temperature control system more proximate to the container for example within the cooling unit or at least on-vessel. This kind of proximate location of the processor may be advantageous in avoiding interruption or malfunction of the temperature control system during communications interruptions through the bi-directiona! data communication link. Such communications interruption may be caused by technical causes or natural force such atmospheric disturbances or a failure of certain components of the bi-directional data communication link such as satellite dishes, radios, terminals etc. In one embodiment, the temperature control system is further adapted to comparing the supply air temperature to a minimum supply air temperature, Tsup-min- The temperature control system stops further decrease of the supply air temperature and maintains the supply air temperature for a predetermined time period if the supply air temperature equals or fails below the minimum supply air temperature. The minimum supply air temperature therefore imposes a lower limit on the supply air temperature which is a helpful feature in preventing chill damage to the fruit of the commodity load. The

temperature control system may be adapted to record a failure of the cold treatment protocol if the load temperature exceeds the protocol temperature despite the supply air temperature equals the minimum supply air

temperature. A trained technician or operator on board the vessel, or situated in the remote on-land control center, may take appropriate corrective action, if any exists, after receipt of a corresponding treatment failure notification. In one embodiment, the temperature control system is configured to adjust the air temperature by changing a flow rate of the cooled air. This may be advantageous to either lower or increasing the load temperature. The flow rate of the cooled air may be changed in conjunction with adjustment of the supply air temperature or alone. The temperature control system may initially adjust the flow rate of the cooled air in response to an unwanted temperature deviation (e.g. outside preset temperature limits) between the measured load temperature and the treatment setpoint temperature. If the change of flow rate proves to be unsuccessful after a period of time, the temperature control system may proceed to adjust the supply air temperature in the appropriate direction to compensate for the measured temperature deviation. In one embodiment, the temperature control system is configured to logging load temperatures measured by the temperature probe to an electronic temperature record of the temperature control system. The temperature control system may be formed integrally with the cooling unit arranged proximate to the container and the electronic temperature record stored in a non-volatile memory space of the temperature control system for later readout or transmission. The non-volatiie memory space may comprise anyone of EEPROM, flash-memory, magnetic or optical discs. The temperature control system may alternatively be located remotely and the electronic temperature record stored in a suitable electronic storage media at the remote location such as on a magnetic disc of a server computer.

According to a preferred embodiment, the temperature control system is configured to transmitting the electronic temperature record to an authority in the discharge or destination port or country after completion of the second segment of the temperature profile. In embodiments where the commodity load is subjected to a cold treatment protocol during the second segment of the temperature profile, the transmission of the electronic temperature record is preferably conditioned on a successful completion of the cold treatment.

A second aspect of the invention relates to a method of automatically controlling temperature of a commodity load, the method comprising steps of:

- loading the commodity load into a transport volume of a refrigerated container,

- inserting a temperature probe into fruit pulp of the commodity load to measure a load temperature,

- generating cooled air with a supply air temperature by a cooling unit operating in accordance with control signals from a temperature control system,

- discharging the cooled air into the transport volume to control air

temperature inside the transport volume, - transmitting the load temperature to the temperature control system,

- automatically adjusting the supply air temperature over time by the temperature control system so that the load temperature follows a

predetermined temperature profile.

The respective features and functions of the cooling unit, control signals, temperature control system, temperature probes, predetermined temperature profile etc described in detail above in connection with the first aspect of the invention applies to the present method of controlling the temperature of the commodity load.

According to one embodiment, the method of controlling the temperature of the commodity load comprises a further step of:

- after temperature probe insertion, gradually decreasing the air temperature over time in accordance with a first segment of the predetermined

temperature profile until a treatment setpoint temperature of the commodity load is reached,

- maintaining the load temperature substantially at the treatment setpoint temperature over a predetermined treatment time period. This embodiment is particularly well-suited for applying various cold treatment protocols to the commodity load. This embodiment may advantageously comprise a further step of:

- after expiry of the treatment time period, gradually increasing the air temperature until the load temperature reaches a final setpoint temperature.

Preferably, the treatment setpoint temperature is set in dependence of a protocol temperature specified by an agricultural authority for the commodity load. In one such embodiment, the treatment setpoint temperature is set to a predetermined amount below the protocol temperature where the

predetermined temperature amount is between 0.1 and 0.5 degree Celsius, more preferably between 0.2 and 0.4 degree Celsius. The load temperature may be altered by a step(s) of;

- changing a flow rate of the cooled air to adjust the air temperature and/or changing the supply air temperature.

In a preferred embodiment of the invention comprises a further step of:

- comparing the supply air temperature to a minimum supply air temperature, Tsup-min- If the supply air temperature is equal to or lower than the minimum supply air temperature, stop further lowering of the supply air temperature and maintaining the supply air temperature for a predetermined time period.

If the supply air temperature decreases so as to reach the minimum setpoint air temperature it may be advantageous to monitor the load temperature thereafter and comparing the load temperature with the protocol temperature to determine whether the load temperature exceeds the protocol temperature since this correction leads to a cold treatment protocol failure. In the latter situation, a treatment failure indicator may be recorded in the temperature control system. The treatment failure indicator is preferably displayed and/or transmitted to a trained technician or operator on board the vessel who may take appropriate corrective action.

The present methodology may advantageously comprise a further step of logging load temperatures measured by the temperature probe to an electronic temperature record of the temperature control system to obtain the previously outlined advantages. One such embodiment comprises a further step of, after completion of the predetermined treatment time period, transmitting the electronic temperature record to an authority in the discharge or destination port or country. The automated container refrigeration system may comprise more than one temperature probe such as two, three, four or even more temperature probes inserted into the commodity load depending on specific protocols or requirements of the relevant national authorities and other factors. Likewise, the above described methodology of controlling the temperature of the commodity load may rely on additional temperature probes that transmit respective measured load temperatures to the temperature control system.

One embodiment of the present methodology therefore comprises further steps of:

- inserting a second and a third temperature probe in fruit pulp at different positions of the commodity load to measure a second and a third load temperature,

- transmitting the second and third load temperatures to the temperature control system,

- comparing the load temperature, the second load temperature and the third load temperature,

- selecting the highest one of the load temperature, the second load temperature and the third load temperature as representative of the load temperature. According to this embodiment, the temperature control system exclusively relies on the hottest temperature probe at any particular point in time to control the supply air temperature and (indirectly) load temperature. In connection with the application of cold treatment protocols this embodiment advantageously ensures that temperatures of all portions of the commodity load lie below the relevant protocol temperature, in particular under circumstances where large temperature gradients could exist within the transport volume.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will be described in more detail in connection with the appended drawings, in which: Figs. 1a)-c) show top, side and door schematic views of a refrigerated container, respectively, comprising three temperature probes in accordance with a first embodiment of the invention,

Fig. 2 is a flow chart comprising initialization steps of a temperature control system adapted to controlling a temperature profile of a commodity load housed inside the refrigerated container in accordance with the first embodiment of the invention,

Fig. 3 is a flow chart illustrating program steps executed by a processor of the temperature control system during execution of an automated cold treatment (ACT+) protocol to the commodity load in accordance with the first embodiment of the invention,

Fig. 4 is a flow chart illustrating program steps executed by the processor of the temperature control system during application of a heat-up procedure to the commodity load; and

Fig. 5 illustrates a predetermined temperature profile of a commodity load for automated cold treatment of fruits of the commodity load.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figs. 1a)-c) show schematically top, side and door schematic views of a refrigerated container 10, respectively, comprising three temperature probes P1 , P2 and P3 located within a transport volume 12 of the refrigerated container 10. Each of the temperature probes P1 , P2 and P3 are inserted into fruit pulp at different spatial positions of a commodity load (not shown) housed within the transport volume 12. The illustrated spatial positions of the temperature probes P , P2 and P3 are in the present embodiment fixed by requirements imposed by the USDA but may in other embodiments be located otherwise. Temperature probes P1 and P2 are located relatively close to a back-end of the refrigerated container 0 and approximately midways between the floor and ceiling structures of the refrigerated container 10 as illustrated. P3 is positioned approximately midways between side wall structures of the refrigerated container 10 and towards the ceiling structure. All temperature probes are placed at positions where the highest

temperatures of the commodity load inside the transport volume are to be expected so as to generally represent worst-case, i.e. highest, temperatures of the entire commodity ioad,

A cooling unit (not shown) is integrated together with the refrigerated container 0 and produces a stream of cooled air that is discharged into the transport volume 12 through a suitable discharge or inlet port or channel. A air return port or channel (not shown), preferably mounted close to the door and proximate to the ceiling structure or surface is used to collect heated or "warm" return air from the transport volume and transport a return air stream to an air conditioning or cooling element within the cooling unit. The cooling unit comprises an evaporator fan with controllable fan speed, either in discrete steps or continuously, in addition to the cooling element so that both the supply air temperature and its flow rate can be controlled by the cooling unit to control air temperature within the transport volume 12.

A temperature control system (not shown) is integrally formed with the cooling unit in the present embodiment of the invention. The temperature control system comprises a microprocessor adapted to generate suitable control signals to the temperature control system based on measured cargo or load temperatures supplied by the temperature probes P1 , P2 and P3. The microprocessor is programmed by set of program instructions, but may in other embodiments be replaced, or supplemented, by hard-wired application specific logic circuit adapted to execute a certain subset or all the

microprocessor functions. The microprocessor based temperature control system ensures that the control signals for the cooling unit are generated automatically so as to appropriately control the supply air temperature and/or the flow thereof such that the load temperature follows a predetermined temperature profile as illustrated in Fig. 5 and the accompanying description thereof below. Fig. 2 is a flow chart comprising initialization steps of a temperature control system adapted to provide automated cold treatment of a commodity load housed inside the refrigerated container (10 Fig. 1 ). The automated cold treatment is provided by controlling the temperature of the commodity load in accordance with predetermined parameters entered into the temperature control system by an authorized person such as an employee or vendor of the carrier company for example a technician or vessel officer. Steps 20 , 203, 205, 207, 209 and 211 are preferably executed by manually entering the relevant parameters in the temperature control system. The temperature control system may comprise a touch display, keyboard or any other suitable means for entry of the relevant parameters via suitable menus and submenus. The parameters are subsequently read and stored in a suitable non-volatile memory segment accessible to the microprocessor and the temperature profile determined.

In step 203, the technician enters the setpoint temperature, Tsetpoint, for the load temperature during cold treatment.

The initialization procedure proceeds to steps 205 and 207 where the technician, in step 205, enters the maximum protocol temperature, Tprotocol, or protocol temperature for the cold treatment protocol in question and secondly a desired duration of the cold treatment period or treatment time period. This allows the temperature control system to compare measured probe temperatures to the protocol temperature and generate and transmit a failure indicator if the latter unintentionally is exceeded.

The initialization procedure proceeds to step 209 where the technician enters a desired minimum supply air temperature, Tsup-min, that serves a lower temperature limit for the supply air temperature. According to the present embodiment of the invention, any further lowering of the supply air temperature is cancelled if the supply air temperature reaches Tsup-min to avoid chilling damage of the commodity load. The initialization procedure proceeds to step 211 where the technician enters a final setpoint temperature, Tfinal, for the commodity load that represents a desired temperature for the commodity load after the cold treatment procedure has been completed. This is explained in further detail below with reference to Fig. 4. in step 213, the microprocessor of the temperature control system communicates with the temperature probes (Fig. 1 P1 , P2 and P3) to ensure all probes are present and operational. The temperature probes are preferably calibrated in crushed ice water during the present initialization process to verify their accuracy and/or compute appropriate correction factors as the case may be.

The initialization procedure thereafter proceeds to step 215 where the commodity load is positioned inside the transport volume of the refrigerated container and stuffed in an appropriate manner so as to allow appropriate air circulation. In the present embodiment of the invention, the commodity load comprises fruits such as apples, citrus fruits, grapes, kiwis, pears, cherries etc. In step 217, the temperature probes (Fig. 1 - P1 , P2 and P3) are inserted into the fruit pulp at the locations illustrated on Fig. 1 .

Previous to executing step 219, the refrigerated container is sealed or closed and the automated cold treatment procedure, according to the previously entered parameters, initialized by the temperature control system either automatically or by manual intervention. The refrigerated container is now ready for applying the automated cold treatment protocol as described below in further detail with reference to Fig. 3. Fig. 3 is a flow chart illustrating program steps executed by the

microprocessor of the temperature control system during execution of the automated cold treatment (ACT+) protocol in the second segment of the predetermined temperature profile 50 illustrated of Fig. 5, The illustrated steps 301 -323 are preferably executed by a set of program instructions stored in program memory of the microprocessor. In this manner, the present invention may be implemented on existing computing hardware of container refrigeration systems by loading the set of program instructions, or ACT+ routine/software, into a microprocessor of the computing hardware.

Furthermore, the ACT+ software may conveniently be distributed through digital communications networks or on digital data media including suitable data carriers such as CD-ROMs. DVDs, flash memory sticks etc. In step 301 , the microprocessor of the temperature control system acquires temperature data for all three temperature probes (Fig. 1 - P1 , P2 and P3). This may either be done by polling the temperature probes for new probe temperature data or by the temperature probes being configured to voluntarily transmitting the new probe temperature data to the microprocessor. In step 303, the microprocessor compares a current duration of the cold treatment to the previously entered target treatment time, i.e. the duration of the cold treatment protocol. If the current duration of the cold treatment is less than the target treatment time, the microprocessor proceeds to step 305 wherein individual probe temperature data are compared and the hottest temperature probe identified together with corresponding probe temperature, if the current duration of the cold treatment exceeds the target treatment time, the microprocessor proceeds to step 325 wherein the cold treatment is terminated and a recorded electronic temperature record or ACT+ record transmitted to an authority in the discharge port or country in step 327.

Subsequently, or concurrently, the microprocessor initializes a heat-up process of the commodity load where under the load temperature follows a gradually increasing temperature segment 56 of the temperature profile 52 as explained in further detail below in connection with Figs. 4 and 5. In step 307, the microprocessor compares the probe temperature of the hottest probe to the protocol temperature, Tprotocol, and if the latter is exceed, the microprocessor proceeds to step 323 where a failure indicator is recorded to the ACT+ record as described above. On the other hand, if the probe temperature is below the probe temperature in step 307, the microprocessor proceeds to step 309 and tests whether, the probe temperature exceeds the setpoint temperature, Tsetpoint, with more than a small temperature amount, preferably less than 0.3 degree C such as 0.1 degree C. If the outcome of this comparison is negative (N), the microprocessor proceeds to step 311 and determines whether the probe temperature lies more than a small temperature amount, preferably less than 0.3 degree C such as 0.1 degree C, below the setpoint temperature, Tsetpoint. If the outcome of this

comparison is also negative (N), the microprocessor can conclude that the probe temperature of the hottest probe, and therefore the highest commodity load temperature, lies inside a narrow temperature band of +/- 0.1 degree C around the setpoint temperature and no corrective action in terms of altering the supply air temperature and/or the airflow is required. Accordingly, the microprocessor returns to step 301 and awaits receipt of new probe temperature data. On the other hand if the microprocessor in step 309 determines that the probe temperature exceeds the setpoint temperature, Tsetpoint, with more than 0.1 degree C, the microprocessor proceeds to step 315 where the supply air temperature is decremented by a fixed amount such as 0.1 degree C to counteract the detected too high load temperature. In the alternative, the supply air temperature may be maintained and the air flow of the cooled air increased a certain amount for example by changing a speed setting of the evaporator fan to improve air circulation within the transport volume. After the supply air temperature has been decremented (or air flow increased), the microprocessor proceeds to step 317 where the supply air temperature is compared to the previously entered minimum supply air temperature, Tsup-min. If the supply air temperature is higher than the minimum supply air temperature, the microprocessor returns to step 301 and awaits receipt of new probe temperature data. On the other hand, if the supply air temperature is equal to or below the minimum supply air temperature, the microprocessor maintains the supply air temperature for a predetermined period of time such as between 2 and 24 hours for example about 6 hours in step 319. Thereafter, the microprocessor acquires new probe temperature data and if the load temperature exceeds the protocol temperature, in step 321 , despite the prolonged time period with the supply air temperature held at the minimum supply air temperature, the procedure proceeds to step 323 where the failure indicator is recorded to the ACT+ record. On the other hand if the load temperature as indicated by the probe temperature is lower than the protocol temperature, in step 321 , the procedure returns to step 303 where norma! ACT operation continues as described above.

Fig. 4 is a flow chart illustrating program steps executed by the

microprocessor of the temperature control system during execution of the previously-mentioned heat-up procedure of the commodity load after successful completion of the ACT+ protocol, i.e. subsequent to step 328 of Fig. 3. During the heat-up process of the commodity load the load

temperature follows a third segment (56 of Fig. 5) of the temperature profile (50 of Fig. 5) with gradually increasing temperature. The purpose of the heat- up process is to maintain the fruit of the commodity load by storage at a normal temperate level such as between 0.0 and 30.0 degree C, preferably between 3 and degree C depending on the specific type of fruit or fruits of the commodity load.

The heat-up process commences at step 401 and proceeds to step 403 wherein the supply air temperature is increased by a predetermined amount or step for example between 0.2 and 0.8 degree C such as about 0.55 degree C. In step 405, the microprocessor of the temperature control system acquires temperature data for all three temperature probes (Fig. 1 - P1 , P2 and P3) in the previously described manner. The microprocessor proceeds to step 407 wherein individual probe temperature data are compared and the hottest temperature probe determined together with corresponding load temperature, Tprobe, indicated by the hottest probe. In step 409, the

microprocessor compares the acquired Tprobe, with a final setpoint

temperature or cargo setpoint, Tfl_nai. If T_pr0be exceeds or equals the cargo setpoint, the procedure proceeds to step 41 1 where the microprocessor stops any further increase of the supply air temperature by maintaining a current supply air temperature so as to keep the load temperature at its current level. In step 4 3, the heat-up procedure is terminated and the microprocessor may jump to another temperature control program specified by the temperature control system for normal operation of the automated container refrigeration system temperature.

If Tprob_G is smaller than the cargo setpoint in step 409, the procedure returns to step 403 to increase the suppiy air temperature by another step or amount, preferably after a certain delay period or time. The delay period may be set to a value between 2 and 12 hours such as between 4 and 8 hours to ensure that a previous increase of the supply air temperature has led to a

corresponding and essentially stable increase of the load temperature.

Fig. 5 illustrates a predetermined temperature profile 50 for the previously described automated cold treatment protocol applied to the fruits of the commodity load. The predetermined temperature profile 50 comprises four segments or temperature segments 52, 54, 56 and 58 which may have been defined by the previously mentioned manual entry of parameters. An actual load temperature over time is indicated by dotted line 55. The previously mentioned protocol and setpoint temperatures, Tprotocol and Tsetpoint, respectively, are indicated on the y-axis. In the present embodiment, the protocol temperature is set to minus 0.2 and the setpoint temperature to minus 0.7 degree C. The relatively small difference between the setpoint and protocol temperatures is possible due to the rapid automated control of the load temperature provided by the present embodiment of the invention. Time points indicated by t1 and t2 on the x-axis mark on-set and termination points of the ACT+ protocol. Consequently, the difference between t1 and t2 indicates the cold treatment time period which typically lies between 14 and 22 days depending on nature and origin of the fruit to be treated. As illustrated, the time segment 54 of the temperature profile 50 between t1 and t2 indicates a constant set-point temperature of minus 0.7 degree C. A first time segment 52 of the temperature profile 50 specifies a gradual decrease of temperature over time until the set-point temperature is reached at t1 .

A third time segment 56 of the temperature profile 50 specifies a gradual increase of load temperature over time during the previously described heat- up procedure until the final setpoint temperature or cargo setpoint, T_fj_nai is reached. Thereafter, during a constant temperature fourth segment 58 of the temperature profile, the commodity load temperature is maintained

essentially constant for a residual transport time of the refrigerated container.

The actual load temperature over time, as represented by the hottest temperature probe, is indicated by dotted line 55. As illustrated, the actual load temperature is capable of following the predetermined temperature profile 50 within a narrow temperature interval of about +/- 0.2 or +/-0.3 degree C, in particular in connection with the cold treatment during the second time segment 54. The close correspondence between the actual load temperature 55 and the predetermined temperature profile 50 is made possible due to the small and rapid corrective steps made to the supply air temperature by the automated temperature control system to compensate for very small temperature deviations, such about 0.1 degree C, between the measured load temperature and the setpoint temperature as described above in connection with Fig. 3.

Claims

1. An automated container refrigeration system comprising:

- a container comprising a transport volume,

- a cooling unit configured to control air temperature within the transport volume by discharging cooled air with a supply air temperature into the transport volume in accordance with control signals supplied by a

temperature control system,

- a first temperature probe insertable into fruit pulp of a commodity load arranged within the transport volume,

- the first temperature probe being operatively connected to the temperature control system for supplying a load temperature thereto,

- the temperature control system being adapted to adjust the supply air temperature over time so that the load temperature follows a predetermined temperature profile.

2. An automated container refrigeration system according to claim 1 , wherein the predetermined temperature profile comprises:

- a second segment where the load temperature is maintained at the treatment setpoint temperature over a predetermined treatment time period, and optionally,

- a third segment with gradually increasing air temperature over time until the load temperature reaches a final setpoint temperature.

3. An automated container refrigeration system according to claim 2, wherein the treatment setpoint temperature, during the second segment, is set to be a predetermined amount below a protocol temperature specified by an agricultural authority for the commodity load;

- the predetermined amount being between 0.2 and 0.5 degree Celsius.

4. An automated container refrigeration system according to any of the preceding claims, wherein the temperature control system is arranged within the cooling unit.

5. An automated container refrigeration system according to any of the preceding claims, wherein the temperature control system comprises a remote processor, such as a processor in an on-ship or on-shore control center, coupled to the cooling unit through a bi-directional data

communication link,

- the remote processor being programmed to generate the control signals based on load temperatures received through the bi-directional data communication link. 6. An automated container refrigeration system according to any of the preceding claims, wherein the temperature control system is further adapted to:

- comparing the supply air temperature to a minimum supply air temperature, Tsup-min,

- if the supply air temperature is equal to or lower than the minimum supply air temperature, stop further decrease of the supply air temperature and maintain the supply air temperature for a predetermined time period.

7. An automated container refrigeration system according to any of the preceding claims, wherein the temperature control system is configured to adjust the air temperature by changing a flow rate of the cooled air.

8. An automated container refrigeration system according to any of the preceding claims, wherein the temperature control system is configured to logging load temperatures measured by the temperature probe to an electronic temperature record of the temperature control system.

9. An automated container refrigeration system according to claim 8, wherein the temperature control system is configured to transmitting the electronic temperature record to an authority in the discharge or destination port or country after completion of the second segment of the temperature profile. 0. A method of automatically controlling temperature of a commodity load, the method comprising steps of:

- discharging the cooled air into the transport volume to control air temperature inside the transport volume,

- transmitting the load temperature to the temperature control system,

predetermined temperature profile.

11. A method of controlling a temperature of a commodity load according to claim 0, comprising a further step of:

- maintaining the load temperature substantially at the treatment setpoint temperature over a predetermined treatment time period.

12. A method of controlling a temperature of a commodity load according to claim 11 , comprising a further step of:

- after expiry of predetermined treatment time period, gradually increasing the air temperature until the load temperature reaches a final setpoint temperature.

13. A method of controlling a temperature of a commodity load according to claim 11 or 12, comprising a further step of:

- setting the treatment setpoint temperature in accordance with a protocol temperature specified by an agricultural authority for the commodity load.

14. A method of controlling a temperature of a commodity load according to claim 13, wherein the treatment setpoint temperature is set to a

predetermined amount below the protocol temperature;

- the predetermined temperature amount being between 0.1 and 0.5 degree Celsius, more preferably between 0.2 and 0.4 degree Celsius.

15. A method of controlling a temperature of a commodity load of a refrigerated container according to any of claims 10- 4, comprising a further step of:

- changing a flow rate of the cooled air to adjust the air temperature.

16. A method of controlling a temperature of a commodity load according to any of claims 13-15, comprising a further step of:

- if the supply air temperature is equal to or lower than the minimum supply air temperature, stop further lowering of the supply air temperature and maintaining the supply air temperature for a predetermined time period.

17. A method of controlling a temperature of a commodity load according to claim 16, comprising a further step of:

- monitoring the load temperature after the air temperature equals the minimum setpoint air temperature,

- comparing the load temperature with the protocol temperature,

- recording a treatment failure indicator in the temperature control system if the load temperature exceeds the protocol temperature.

18. A method of controlling a temperature of a commodity load according to any of claims 10-17, comprising a further step of:

- logging load temperatures measured by the temperature probe to an electronic temperature record of the temperature control system.

19. A method of controlling a temperature of a commodity load according to claim 18, comprising a further step of:

- after completion of the predetermined treatment time period, transmitting the electronic temperature record to an authority in the discharge or destination port or country, 20. A method of controiling a temperature of a commodity load according to any of claims 10-19, comprising further steps of:

- selecting the highest one of the load temperature, the second load temperature and the third load temperature as representative of the load temperature.