Automatic defrosting system in active cooling suitcase

Abstract

The present disclosure provides systems and methods for automatic defrosting of an actively cooled suitcase. In some embodiments, a method of operating an active cooling vessel includes determining to initiate a defrost cycle for the active cooling vessel; deactivating a cooling system of the active cooling vessel; activating a defrost heater of the active cooling vessel; determining to deactivate the defrost heater of the active cooling vessel; setting the defrost heater to maintain the temperature of the heat receiver system at a threshold; waiting for a set duration to allow the melted frost to drop into the collection tray; and activating the cooling system of the active cooling vessel.

Description

[0001] Related applications

[0002] This application claims the benefit of provisional patent application serial number 63 / 528,475, filed on July 24, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally pertains to temperature-controlled environments. Background Technology

[0004] Solid-state refrigeration systems use heat exchangers (called "acceptors") to transfer heat from the conditioned air and the thermoelectric cooling unit. The conditioned air in a freezer case can trap moisture from ambient air or from the food stored in the case. Because the dew point of the acceptor heat exchanger in a freezer case is almost always lower than that of the ambient air or the air that retains moisture evaporated from the food, the moisture will naturally condense and then freeze on the acceptor heat exchanger.

[0005] A defrost heater and operating cycle are needed to melt the frost that gradually accumulates on the receiver heat exchanger in the refrigeration unit's carrying case during normal operation. This is helpful because the receiver heat exchanger becomes significantly inefficient at higher frost levels.

[0006] Under normal suitcase operation, moisture inside the suitcase condenses and freezes on the surface of the receiver heat exchanger. This moisture comes from many sources, such as an open lid, leaking gaskets, and moisture-rich food stored in the suitcase.

[0007] At low frost levels (mass <50 g), there is a negligible impact on suitcase performance. However, once the frost mass exceeds this level, it begins to act as an insulating covering on the heat exchanger. This significantly reduces the coefficient of performance of the refrigeration system and ultimately causes the suitcase to fail to maintain its setpoint temperature even under maximum power input to the thermoelectric module.

[0008] At some point, the receiver heat exchanger becomes completely blocked by frost, and the airflow through the heat exchanger is reduced, thus hindering the suitcase's proper cooling performance. Summary of the Invention

[0009] This disclosure provides systems and methods for automatically defrosting an actively cooled suitcase. In some embodiments, a method of operating an actively cooled container includes: determining to start a defrost cycle for the actively cooled container; disabling the cooling system of the actively cooled container; activating the defrost heater of the actively cooled container; determining to deactivate the defrost heater of the actively cooled container; setting the defrost heater to maintain the temperature of the heat receiver system at a threshold; waiting for a set duration to allow melted frost to drip into a collection tray; and activating the cooling system of the actively cooled container.

[0010] In some embodiments, the method further includes: deactivating one or more fans of the active cooling container. In some embodiments, the method further includes: after waiting for a set duration: activating one or more fans of the active cooling container. In some embodiments, activating one or more fans includes: activating one or more fans of the heat receiver system in response to determining that the temperature of the heat receiver system is at or below a set threshold temperature. In some embodiments, the set threshold temperature is zero degrees Celsius.

[0011] In some embodiments, determining to deactivate the defrost heater includes one or more of the following: determining that the defrost heater has been activated for a predetermined amount of time; and determining that the temperature of the heat receiver system exceeds a set threshold.

[0012] In some embodiments, determining to begin a defrost cycle includes one or more of the following: reaching the time elapsed since a previous defrost; determining that the difference between the receiver temperature and the chamber temperature exceeds a specified value; determining that the ratio of the lid-open duration to subsequent full-power operation exceeds a specified value; determining the relative humidity of the actively cooled container; and determining the quality of the frost on the current heat exchanger.

[0013] In some embodiments, the method further includes: activating an alarm indicating that frost may have accumulated. In some embodiments, the method further includes: determining that a threshold number of defrosting cycles have been performed. In some embodiments, the method further includes: ensuring that the temperature of the actively cooled container does not rise above an allowable limit.

[0014] Those skilled in the art will understand the scope of this disclosure and recognize other aspects of it after reading the following detailed description of preferred embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0016] Figures 1A to 1D The use of portable, stand-alone refrigeration or freezing systems coupled with integrated automated control and monitoring was demonstrated;

[0017] Figure 2 as well as Figure 3A and Figure 3B An example embodiment of an active cooler according to embodiments of the present disclosure is shown;

[0018] Figure 4 Systems including active coolers according to some embodiments of the present disclosure are shown;

[0019] Figure 5 Examples of suitcases as discussed in this article are shown;

[0020] Figure 6A and Figure 6B The exhibition showcased different types of suitcases that can be used in refrigerated or frozen models;

[0021] Figure 7 An exploded view of the suitcase, including the thermoelectric unit as discussed herein, is shown.

[0022] Figure 8 A front view of a defrost heater on a receiver heat exchanger according to some embodiments is shown;

[0023] Figure 9 An isometric view of a defrost heater on a receiver heat exchanger according to some embodiments is shown;

[0024] Figure 10 An exploded assembly view of a defrost heater on a receiver heat exchanger in a suitcase chamber according to some embodiments is shown.

[0025] Figure 11 An undisassembled, assembled view of a defrost heater on a receiver heat exchanger in a suitcase chamber according to some embodiments is shown; and

[0026] Figure 12 An overview of the system and key components according to some embodiments is shown. Detailed Implementation

[0027] The embodiments described below illustrate the necessary information to enable those skilled in the art to practice the embodiments and demonstrate the best manner in which the embodiments are practiced. Those skilled in the art will understand the concepts of this disclosure and recognize the application of these concepts not specifically set forth herein when reading the following description in conjunction with the accompanying drawings. It should be understood that these concepts and applications fall within the scope of this disclosure and the appended claims.

[0028] Last-mile food delivery requires the use of vans or similar vehicles for temperature-controlled transport of perishable foods. To achieve temperature control, refrigerated or frozen cargo boxes can be installed in vans (e.g., cargo trucks) or box trucks.

[0029] These suitcases use an active heat pump to extract heat from the enclosed chamber and release it into the surrounding air. The hot air must be removed from the van to ensure optimal operation of the crates.

[0030] These suitcases require electricity during transport to maintain food safety requirements for perishable consumer goods. The electrical system needs to meet (and / or maintain) the correct temperature necessary for the suitcases to operate.

[0031] Figures 1A to 1D The use of portable, stand-alone refrigeration or freezing systems coupled with integrated automated control and monitoring is demonstrated.

[0032] Figure 2 as well as Figure 3A and Figure 3B An example embodiment of an active cooler according to embodiments of the present disclosure is shown.

[0033] Figure 4 A system including an active cooler is shown according to some embodiments of the present disclosure.

[0034] For further details, interested readers may refer to U.S. Provisional Patent Application Serial No. 62 / 953,771 entitled “THERMOELECTRIC REFRIGERATED / FROZEN PRODUCT STORAGE AND TRANSPORTATION COOLER”; U.S. Patent Application Serial No. 17 / 135,420 entitled “THERMOELECTRIC REFRIGERATED / FROZEN PRODUCT STORAGE AND TRANSPORTATION COOLER”, now U.S. Patent Application Publication No. 2021 / 0199353 A1; and International Patent Application Serial No. PCT / US2020 / 067172 entitled “THERMOELECTRIC REFRIGERATED / FROZEN PRODUCT STORAGE AND TRANSPORTATION COOLER”, now International Patent Publication No. WO 2021 / 134068. These applications are hereby incorporated herein by reference in their entirety.

[0035] Figure 5 An example of a suitcase, as discussed in this article, is shown. Figure 6A and Figure 6B The exhibition showcased different types of suitcases that can be used in refrigerated or frozen models. Figure 7 An exploded view of the suitcase, including the thermoelectric unit as discussed herein, is shown.

[0036] Figure 8 A front view of a defrost heater on a receiver heat exchanger according to some embodiments is shown. Figure 9 An isometric view of a defrost heater on a receiver heat exchanger according to some embodiments is shown. Figure 10 An exploded assembly view of a defrost heater on a receiver heat exchanger in a suitcase chamber, according to some embodiments, is shown. Figure 11 An undisassembled, assembled view of a defrost heater on a receiver heat exchanger in a suitcase chamber, according to some embodiments, is shown. Figure 12 An overview of the system and key components according to some embodiments is shown.

[0037] In some embodiments, the automatic defrosting system is implemented in an actively cooled suitcase, achieving three key objectives in mitigating the described frosting problem:

[0038] 1. Always keep the frost on the receiver heat exchanger to less than 50 grams to prevent complete frost formation and the corresponding decrease in cooling performance.

[0039] 2. The operation of target number 1 above is implemented automatically, running in the background, with little or no impact on normal cold chain operations.

[0040] 3. To provide a convenient means of removing and treating water / ice that naturally accumulates in a suitcase during normal operation.

[0041] Defrosting heater specifications

[0042] Defrosting of the receiver heat exchanger is achieved by supplying power to the conductors (or array of conductors) of a resistance heater attached to the rear surface of the receiver heat sink. When energized, the heater raises the temperature of the heat sink well above freezing to melt the accumulated frost.

[0043] The following is a summary of the characteristics of the defrost heater. Ideally, the listed resistivity should be achieved using a nickel-chromium 80 alloy (nickel to chromium ratio of 4:1). 60 watts is chosen as the target power level because it provides a good balance between minimizing the time required to run the defrost cycle and the heat loss associated with using a higher power level.

[0044]

[0045] Features of defrosting heaters

[0046] Main control scheme

[0047] The main control scheme / algorithm used for the defrosting cycle includes one or more of the following:

[0048] 1. Begin defrosting when the time elapsed since the last defrost has been reached (every 8-10 hours).

[0049] 2. Turn off thermoelectric cooling operation.

[0050] 3. Turn off the fan.

[0051] 4. Set the defrost heater duty cycle (80%-100% of total power).

[0052] 5. Turn on the defrost heater for the set duration (10-20 minutes).

[0053] 6. The defrost heater will be turned off when either of the following two conditions is met: the duration reaches the set amount (10-20 minutes) or the receiver temperature exceeds the set threshold (30°C).

[0054] 7. Set the defrost heater to maintain the receiver temperature at the threshold (30°C).

[0055] 8. Wait for the set duration (5 minutes) to allow the melted frost to drip into the collection tray.

[0056] 9. Turn on the exhaust fan.

[0057] 10. Turn on the cooling operation.

[0058] 11. After the receiver temperature drops below the set threshold (°C), turn on the receiver fan.

[0059] The air temperature around the receiver fan and the fan's control are crucial for minimizing the temperature rise of food in the suitcase. If the fan is turned on immediately after defrosting and heating, hot air will blow onto the food. If the fan remains on for an extended period, the food will heat up due to the lack of cool air circulation.

[0060] Additional control scheme parameters

[0061] Further refinement of the defrosting control scheme can be achieved by monitoring key operating parameters and adjusting the defrosting cycle steps accordingly to match the real-time operating conditions of the ACT in the field. These parameters include, but are not limited to:

[0062] Monitoring T 接受器 (Receiver temperature) and T 控制 The difference between (chamber temperatures). When this difference exceeds a specified value, the risk of impending frost is high and can be used to trigger an immediate defrost cycle instead of waiting for the next scheduled cycle. It can also issue an alert to the customer or customer service indicating that manual intervention is required to empty the ice tray or alleviate excessive moisture usage / conditions.

[0063] Monitor the ratio of lid-open duration to subsequent full-power operation. When this ratio exceeds a specified value, the risk of impending frost is high and can be used to trigger an immediate defrost cycle instead of waiting for the next scheduled cycle. It can also issue alerts to customers or customer service indicating the need for manual intervention to empty the ice tray or alleviate excessive moisture usage / conditions.

[0064] The aforementioned warning parameters can trigger a frost relief "limp mode" to reduce thermal power and raise the suitcase's temperature setpoint to a value higher than normal (but not exceeding the maximum food safety value), maintaining this temperature until the risk of frost formation decreases. This mode enhances the periodic defrosting cycle as an additional protection against complete frost buildup, especially in cases of excessive moisture accumulation. In extreme cases where frost formation does occur, this mode also keeps the suitcase's temperature and power under control until manual relief can be completed, thus preventing uncontrolled operation due to unpredictable power and temperature fluctuations.

[0065] Having the ability to measure the relative humidity (RH) added to the control system, an alternative embodiment of the control algorithm could be:

[0066] ○Time since the last defrost, t 上次

[0067] ○ Total time the lid has been open since the last defrost, t 盖子开启

[0068] ○Ambient relative humidity, RH

[0069] If (t) 上次 +t 盖子开启 If *RH*k)>X days, then defrosting will occur.

[0070] k will be an adjustable factor based on the degree of impact of lid opening as determined in the tests. The number of days X will also be adjusted based on the observed rate of frost buildup.

[0071] Please note that control schemes based on directly sensing the quality of frost on heat exchangers have been abandoned due to excessive cost and complexity.

[0072] Impact on food load

[0073] To prevent disruptions to cold chain operations, a defrosting cycle can and should be run while the food is still in the carrying case. To ensure that the food temperature does not rise above the permissible limit (-16°C, t>1 hour), short and regular defrosting intervals are defined in the above control scheme.

[0074] Remove the refrozen ice from the suitcase.

[0075] During a defrost cycle, frost on the receiver heat exchanger melts and drips, collecting in a well (or trough) at the bottom of the suitcase's internal chamber. During normal operation of the suitcase, the water will refreeze into ice in this well. After a certain number of defrost cycles have occurred, it is necessary to remove this ice.

[0076] A water / ice collection well is placed below the receiver heat exchanger to capture melted water. The well is smooth and washable, meeting food safety requirements. A removable ice tray is fitted inside the well to retain the water / ice, preventing it from spreading to the floor of the storage compartment and allowing for easy removal of the ice from the carrying case. After a certain number of defrosting cycles have been reached, controls in the carrying case can create a notification or alarm instructing maintenance personnel to manually remove the tray and dispose of the ice. The alert can be issued via an onboard IoT system or by utilizing lights or indicators on the carrying case's display itself. The worker will remove the ice from the tray and then place the tray back into the carrying case for further defrosting cycles.

[0077] The dish can be made of a flexible material, such as silicone rubber, which can be peeled off from refrozen ice. Alternatively, a harder plastic that allows twisting to release ice from the dish can be used.

[0078] The ice tray can be configured with features such as contact switches or sensors to indicate its presence in the suitcase and to allow or disable operation with or without the tray.

[0079] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of this disclosure. All such improvements and modifications are considered to be within the scope of the concepts disclosed herein.

Claims

1. A method of operating an actively cooled container, the method comprising: The defrosting cycle for the active cooling container is initiated. Discontinue the cooling system of the active cooling container; Start the defrost heater of the active cooling container; Determine to disable the defrost heater of the active cooling container; The defrost heater is configured to maintain the temperature of the heat receiver system at a threshold. Wait for the set duration to allow the melting frost to drip into the collection tray; as well as Start the cooling system of the active cooling container.

2. The method according to claim 1, further comprising: Disconnect one or more fans from the active cooling container.

3. The method according to any one of claims 1 to 2, further comprising: After waiting for the set duration: Start one or more fans of the active cooling container.

4. The method of claim 3, wherein starting the one or more fans comprises: In response to determining that the temperature of the heat receiver system is at or below a set threshold temperature, one or more fans of the heat receiver system are activated.

5. The method according to claim 4, wherein the set threshold temperature is zero degrees Celsius.

6. The method according to any one of claims 1 to 5, wherein determining to deactivate the defrost heater comprises one or more of the following: It has been determined that the defrosting heater has been activated for a predetermined period of time; It was determined that the temperature of the heat receiver system exceeded a set threshold.

7. The method according to any one of claims 1 to 5, wherein determining the start of the defrosting cycle comprises one or more of the following: The time elapsed since the previous defrost; Determine that the difference between the receiver temperature and the chamber temperature exceeds a specified value; Determine if the ratio of the duration of lid opening to subsequent full-power operation exceeds a specified value; Determine the relative humidity of the active cooling container; as well as Determine the quality of the frost on the current heat exchanger.

8. The method according to any one of claims 1 to 7, further comprising: The system activates an alert indicating that frost may have accumulated.

9. The method according to any one of claims 1 to 8, further comprising: Determine that the defrost cycle has been executed for the threshold number of times.

10. The method according to any one of claims 1 to 9, further comprising: Ensure that the temperature of the active cooling container does not rise above the permissible limit.

11. An active cooling container, comprising: Cooling system; One or more fans; Collection disk; and Controller; the controller is operable to: The defrosting cycle for the active cooling container is initiated. Discontinue the cooling system of the active cooling container; Start the defrost heater of the active cooling container; Determine to disable the defrost heater of the active cooling container; The defrost heater is configured to maintain the temperature of the heat receiver system at a threshold. Wait for a set duration to allow the melting frost to drip into the collection tray; as well as Start the cooling system of the active cooling container.

12. The method of claim 11, wherein the controller is further operable to: Disconnect one or more fans from the active cooling container.

13. The method according to any one of claims 11 to 12, wherein the controller is further operable to: after waiting for the set duration: Start one or more fans of the active cooling container.

14. The method of claim 13, wherein being operable to start the one or more fans includes being operable to: In response to determining that the temperature of the heat receiver system is at or below a set threshold temperature, one or more fans of the heat receiver system are activated.

15. The method of claim 14, wherein the set threshold temperature is zero degrees Celsius.

16. The method according to any one of claims 11 to 15, wherein operability to determine deactivation of the defrost heater comprises: Capable of operating to perform one or more of the following: It has been determined that the defrosting heater has been activated for a predetermined period of time; It was determined that the temperature of the heat receiver system exceeded a set threshold.

17. The method according to any one of claims 11 to 15, wherein being operable to determine the start of a defrosting cycle comprises: Capable of operating to perform one or more of the following: The time elapsed since the previous defrost; Determine that the difference between the receiver temperature and the chamber temperature exceeds a specified value; Determine if the ratio of the duration of lid opening to subsequent full-power operation exceeds a specified value; Determine the relative humidity of the active cooling container; as well as Determine the quality of the frost on the current heat exchanger.

18. The method according to any one of claims 11 to 17, wherein the controller is further operable to: The system activates an alert indicating that frost may have accumulated.

19. The method according to any one of claims 11 to 18, wherein the controller is further operable to: Determine that the defrost cycle has been executed for the threshold number of times.

20. The method according to any one of claims 11 to 19, wherein the controller is further operable to: Ensure that the temperature of the active cooling container does not rise above the permissible limit.

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