A defrosting system

Abstract

In a defrosting system for refrigeration device, an evaporator unit includes a first (110) and a second (120) evaporator coil. A processing unit (108) obtains or acquires temperature values (130,140) corresponding to the first and second evaporator coils, and based on a calculated indicator corresponding to a temperature difference between air provided to the first evaporator coil and air output from the second evaporator coil, selectively switches between cooling and defrosting operational modes. During the cooling operational mode, the first evaporator coil is configured to operate at a first temperature and the second evaporator coil is configured to operate at a second temperature that is less than the first temperature. During the defrosting operational mode, the first evaporator coil continues to operate at the first temperature, while the second evaporator coil is allowed to increase in temperature toward or to the first temperature to thereby melt ice formed on the second evaporator coil.

Description

[0001] A DEFROSTING SYSTEM

[0002] Technical Field

[0003] The present disclosure relates to a defrosting system applicable to refrigeration devices. More particularly, the defrosting system provides improved timing to selectively switch between a cooling operational mode and a defrosting mode.

[0004] Background

[0005] Cooling system such as refrigeration devices generally encounter an issue with excessive ice formation on an evaporator coil after carrying out a cooling operation over a particular period of time. One of the causes leading to such ice formation is associated with the moisture present in the air around the evaporator coil coming into contact with the colder surface of the evaporator coil, which subsequently condenses the moisture into water that forms into an accumulation of ice. The ice built up around the evaporator coil inevitably hinders the heat exchange process with the air in an area requiring cooling, thus reducing the efficiency of the refrigeration device.

[0006] In order to restore heat exchange efficiency, the refrigeration device must be defrosted from time to time to melt the ice off of the evaporator coil, typically according to a predetermined schedule performed by a controller or processing unit / processor of the refrigeration device. More particularly, conventional refrigeration devices are scheduled to halt, shut down, or stop a cooling operation, and switch to a defrosting operation or mode to allow sufficient time for melting of the ice. During cooling operation shutdown, the refrigeration device needs to wait until the surface of the evaporator coil reaches a higher temperature adequate for the ice to thaw and corresponding water to drain away from the evaporator coil. Yet, such an approach suffers a serious drawback resulting in temporary loss of cooling capacity within the refrigeration device. Moreover, temporary loss of cooling capacity during the halt or shut down of the cooling operation elevates the temperature of the goods stored inside the refrigeration device, which can adversely impact the quality or freshness of the products stored in the refrigeration device. Additionally, defrosting by way of halting or shutting down the cooling operation can be considered a waste of time and energy as extra energy has to be spent for bringing the refrigeration device back to a desired cooling state at an intended cooling temperature. In view of the aforementioned shortcomings, effort has been put into developing ways to manage defrosting sessions in refrigeration devices. For instance, Japanese patent application no. 2000283575 discloses a refrigeration system with prolonged period between each defrosting session such that better energy consumption can be attained. This refrigeration system employs a valve control means to close a secondary solenoid valve, according to a preset schedule, in a liquid refrigerant pipeline regulating a volume of a refrigerant entering into a downstream side cooler throughout a normal cooling operation. Through the preset schedule, the refrigeration system is able extend the time span between each defrosting session, aiming to obtain better energy efficiency. Still, this refrigeration system fails to take into account the temperature of the air in within the refrigeration system, and merely operates following the preset schedule. Consequently, this refrigeration system may undergo unnecessary or too frequent defrosting cycles, resulting in inadequate overall cooling operation.

[0007] There is a need for a defrosting system or a refrigeration device with a defrosting system capable of identifying or determining an improved, near-optimal, or essentially best timing for performing a defrosting process while intelligently taking into account air temperature fluctuation(s) within the refrigeration device.

[0008] Summary

[0009] The present disclosure and the invention defined by the claims corresponding thereto aim to provide a defrosting system for refrigeration devices or apparatuses that can improve the efficiency of one or more refrigeration device cooling operations, sessions, or intervals. More specifically, a defrosting system in accordance with an embodiment of the present disclosure derives or operates in accordance with a calculated indicator to determine an improved, near- optimal, or essentially best timing to perform a defrosting session between successive (e.g., two or more) cooling sessions, operations, or intervals. Such a defrosting system automatically accounts for dynamic air temperature fluctuation(s) within an evaporator unit associatable or associated with the refrigeration device.

[0010] An object of the present disclosure is directed to a defrosting system configured to determine or measure a temperature difference between incoming air before the incoming air passes across or through a first evaporator coil, and outgoing air after the outgoing air passes across or through a second evaporator coil of an evaporator unit having multiple evaporator coils. The derived temperature difference corresponds to or serves as a calculated indicator by which the defrosting system can be selectively transitioned between a cooling and defrosting modes of operation, e.g., in a successive manner.

[0011] An object of the present disclosure is to extend or prolong a duration between two consecutive defrosting sessions, providing a longer cooling session, by determining an improved timing to initiate and / or cease a defrosting session based on a calculated indicator or parameter derived from a temperature difference between a stream of air traveling to, into, or through a first evaporator coil and a stream of air passing through, out of, or away from a second evaporator coil of an evaporator unit of the defrosting system.

[0012] An object of the present disclosure is to provide a defrosting system in which cooling operation can be provided by the first evaporator coil during a defrosting session while the second evaporator coil operates without being entirely shut down during or throughout the defrosting session. Because cooling operations are not completely shut down during the defrosting session, a refrigeration device equipped with a defrosting system in accordance with an embodiment of the present disclosure needs less energy to bring the temperature within a cold storage space of the refrigeration device back to an intended cooling state or cooling temperature after a transition from a defrosting mode of operation back to a cooling mode of operation.

[0013] One of the objects of the present disclosure is to provide a refrigeration device or apparatus incorporated with a defrosting system in accordance with an embodiment of the present disclosure.

[0014] At least one of the preceding objects is met, in whole or in part, by way of one or more embodiments in accordance with the present disclosure, in which:

[0015] A defrosting system for a refrigeration device includes: an evaporator unit configured receive refrigerant from an expansion device unit, and configurable or configured to evaporate received refrigerant and deliver evaporated refrigerant to a compressor; a temperature detector unit; and a processing unit, wherein: the evaporator unit is installable or installed external to an internal storage compartment of a cabinet of the refrigeration device; the evaporator unit includes a first evaporator coil and a second evaporator coil; the first evaporator coil is configured to operate at a first temperature and the second evaporator coil is configured to operate at a second temperature which is lower than the first temperature during a cooling mode of operation, and the second evaporator coil is configured to operate at a second temperature that increases toward or to the first temperature during a defrosting mode of operation; the temperature detector unit includes a first temperature detector corresponding to an air inlet side of the first evaporator coil and is configured to detect a return air temperature from the cabinet, and a second temperature detector corresponding to an air outlet side of the second evaporator coil and is configured to detect a supply air temperature provided to the cabinet; and the processing unit is configured to obtain or acquire temperature values from the first and second temperature detectors, and is configured to calculate a temperature difference between the return air temperature and the supply air temperature, and compare the temperature difference with a first threshold value to selectively switch the defrosting system between the cooling mode of operation and the defrosting mode of operation based on the calculated temperature difference.

[0016] The first temperature is correlated with or corresponds to a surface temperature of the first evaporator coil, the second temperature is correlated with or corresponds to a surface temperature of the second evaporator coil, and the processor is configured to enable the second temperature to increase toward or to the first temperature during the defrosting mode.

[0017] The processor can be configured to control a first volume of refrigerant entering into the first evaporator coil and a second volume of refrigerant entering into second evaporator coil by way of a first expansion valve and a second expansion valve of the expansion valve unit to thereby regulate the surface temperature of the first evaporator coil and the surface temperature of the second evaporator coil, respectively.

[0018] The processor is configured to switch the second evaporator coil from the cooling mode of operation to the defrosting mode of operation in the event that the temperature difference exceeds the first threshold value. The first threshold value can be between 1 and 2.5, for instance, depending upon the embodiment details / evaporating design.

[0019] The first evaporator coil and the second evaporator coil are typically arranged in series or sequential airflow, such that air flowing through the evaporator unit flows across the first evaporator coil before flowing across the second evaporator coil. During the cooling mode of operation, a surface of the first evaporator coil can be configured to have a temperature between 1°C to -0.5°C, and a surface of the second evaporator coil can be configured to have a temperature between -5 to -15°C.

[0020] The processing unit can resume or reestablish the cooling mode of operation upon determining that the calculated indicator is less than or equal to a second threshold value, which is less than the first threshold value. The second threshold value can be between 0.3 and 0.7, for instance, depending upon embodiment details / evaporating design.

[0021] During the defrosting mode of operation, the first evaporator continues to cool air passing thereacross; and the second evaporator coil can operate without being entirely shut down during or throughout the defrosting mode of operation.

[0022] Brief Description of The Drawings

[0023] Fig. la is a schematic drawing showing portions of a defrosting system in accordance with an embodiment of the present disclosure, and a refrigeration device associated therewith.

[0024] Fig lb is a schematic drawing of portions of a refrigeration device in accordance with an embodiment of the present disclosure, which includes or is equipped with a defrosting system in accordance with an embodiment of the present disclosure.

[0025] Fig. 2 is a schematic drawing showing a manner of measuring a first temperature corresponding to incoming air prior to arrival of the incoming air at a first evaporator coil, and measuring a second temperature corresponding to supply air corresponding to a second evaporator coil in accordance with an embodiment of the present disclosure.

[0026] Fig. 3 is a graph showing a manner in which a defrosting system in accordance with an embodiment of the present disclosure can initiate and stop a defrosting session in view of a temperature difference detected between a stream of incoming air and a stream of supply air.

[0027] Fig. 4 is a graph showing pressure changes associated with operational modes, namely a cooling mode of operation corresponding to a cooling session and a defrosting mode of operation corresponding to a defrosting session. Fig. 5a is a graph showing differences in temperature fluctuations inside a storage compartment of a refrigeration device having a defrosting system in accordance with an embodiment of the present disclosure and configured to provide smart defrost operation based on a calculated indicator, compared to a conventional refrigeration device having a conventional defrosting system configured to provide conventional air static defrost operation.

[0028] Fig. 5b is a graph showing differences in a second expansion valve suction pressure fluctuations corresponding to a refrigeration device having a defrosting system in accordance with an embodiment of the present disclosure and configured to provide smart defrost operation based on a calculated indicator, compared to an expansion valve suction pressure fluctuation corresponding to a conventional refrigeration device having a conventional defrosting system and configured to provide conventional air static defrost operation.

[0029] Detailed Description

[0030] The disclosure herein is described according to particular representative or preferred embodiments corresponding to the accompanying description and drawings. However, it is to be understood that such embodiments are provided for purpose of understanding, and it is envisioned that individuals having ordinary skill in the relevant art may devise various modifications to such embodiments without departing from the scope of the appended claims.

[0031] As used herein, the terms “approximately” or "about", in the context of concentrations of components, conditions, other measurement values, etc., means + / - 5% of the stated value, or + / - 4% of the stated value, or + / - 3% of the stated value, or + / - 2% of the stated value, or + / - 1% of the stated value, or + / - 0.5% of the stated value, or + / - 0% of the stated value.

[0032] The term “refrigeration device” or “refrigeration apparatus” herein can refer to a cooling machine having a thermally insulated storage compartment within a cabinet, which is configured to carry, contain, or store goods, e.g., food or food products, at an intended or desired temperature, such as a temperature close to or below 0°C; and an electromechanical arrangement associated with or around the cabinet and which is configured to carry out heat exchange operations between an environment external to the cabinet and an environment, e.g., a spatial volume, inside the compartment. Fig. la is a schematic drawing showing portions of a conventional defrosting system associated with or incorporated into a refrigeration device or apparatus. The conventional defrosting system provides a single evaporator coil configured to evaporate refrigerant from an expansion device, and deliver the evaporated refrigerant to a compressor, in a manner readily understood by individuals having ordinary skill in the relevant art. Such individuals will further understand that the compressor is fluidically coupled to a condenser.

[0033] Aspects of particular embodiments of the present disclosure address at least one aspect, problem, limitation, and / or disadvantage associated with existing or conventional defrosting systems or modules, e.g., which are associated with or used in refrigeration devices or systems.

[0034] According to an aspect of the present disclosure, a defrosting system configurable or configured to operate in association with or be incorporated into a refrigeration device or apparatus includes: an evaporator unit providing multiple evaporator coils, e.g., at least two evaporator coils arranged or disposed in tandem or serially, and which is configured to evaporate refrigerant received from a multiple expansion devices, e.g., expansion valves, and deliver evaporated refrigerant to a compressor; multiple temperature detectors or sensors disposed relative to the multiple evaporator coils and configured to detect, sense, or measure multiple temperatures, e.g., multiple temperature signals or values, associated with or corresponding to the multiple evaporator coils; and at least one processing unit or processor, e.g., a data processing unit or processor providing a microcontroller or microprocessor, configured to automatically determine whether / when to transition from a cooling mode or full cooling mode of operation to a defrosting mode of operation, and configured to automatically determine whether / when to halt the defrosting mode of operation (and transition back to a cooling mode or full cooling mode of operation), based on the detected or sensed temperatures. The processing unit(s) can be configurable or configured to selectively manage or control the operation of the compressor based on the aforementioned detected or sensed temperatures. Particular representative aspects of a defrosting system associated with or incorporated into a refrigeration device or apparatus in accordance with some representative embodiments of the present disclosure are shown in Fig. lb.

[0035] As indicated in Fig. lb, an evaporator unit (105) can be provided or installed in association with a cabinet of a refrigeration device or apparatus, for instance, relative to an external or exterior portion or side of the cabinet. The evaporator unit (105) includes a first evaporator coil or latent coil (110), and a second evaporator coil or sensible coil (120). The terms “first evaporator”, “latent coil”, and / or “first evaporator coil module” may be used interchangeably with the term “first evaporator coil”, and refer to an evaporator coil configured to perform latent cooling of air in a refrigeration device or apparatus provided with a defrosting system in accordance with an embodiment of the present disclosure. The terms “second evaporator”, “sensible coil”, and / or “second evaporator coil module” may be used interchangeably with the term “second evaporator coil”, and refer to an evaporator coil configured to perform sensible cooling of air in a refrigeration device or apparatus provided with a defrosting system in accordance with an embodiment of the present disclosure.

[0036] The cabinet includes a storage compartment enclosing an internal cooling space containing a volume of air to be cooled by way of heat exchange with the environment exterior to the cabinet. A partition maybe established within the refrigeration device to substantially separate the internal cooling space from an outer cooling space, in which some of the modules of the refrigeration devices can reside. The air within the compartment can typically circulate through the outer cooling space, passing across or through the first (110) and second evaporator coils (120) such that the air is cooled towards or to an intended or desired temperature before being channelled or directed back into the internal cooling space. In some embodiments, one or more air blowers or fans may be positioned around the entrance or exit of the outer cooling space to facilitate air movement through the outer cooling space.

[0037] During a cooling mode of operation, and possibly during at least portions of a defrosting mode of operation, the first evaporator coil (110) is configured to operate at a first temperature, and the second evaporator coil (120) configured to operate at a second temperature which is lower than the first temperature. A first temperature detector (130) is installed at an air inlet side of the first evaporator coil (110) and is configured to measure a return air temperature corresponding to air returned to the evaporator unit (105) from a first portion of the cabinet, such as the outer cooling space; and a second temperature detector (140) is installed at an air outlet side of the second evaporator coil (120) and is configured to measure a supply air temperature corresponding to air directed or provided to or supplied into a second portion of the cabinet, such as the internal cooling space. The first evaporator coil (110) and the second evaporator coil (120) can be or are typically arranged in tandem, e.g., relative to or within an outer cooling space associated with or corresponding to the cabinet, such that the air flow, e.g., the incoming air or air stream flowing into the evaporator unit (105) reaches the first evaporator coil (110) before reaching the second evaporator coil (120).

[0038] The defrosting system includes a processing unit (108) configurable or configured to operate in signal communication with the first and second temperature detectors or sensors (130, 140). The processing unit (108) is configured to calculate a temperature difference between the return air temperature and the supply air temperature and compare the temperature difference with a first selectable, programmable, or predetermined value, e.g., a first threshold value, to selectively activate the defrosting system, such that the defrosting system selectively transitions into a defrosting mode of operation during a defrosting session. The processing unit (108) can be configured to operate based on the execution of a set or sequence of program instructions stored in a processing unit readable or computer readable medium such as memory accessible to or associated with the processing unit (108), in a manner individuals having ordinary skill in the relevant art will readily comprehend.

[0039] An electromechanical arrangement of the refrigeration device includes particular interconnected modules or units configured to enable the defrosting system to identify an improved, near-optimum, or essentially best timing to initiate a defrosting session, e.g., which temporarily interrupts a current cooling session, or which is interposed between two cooling session time intervals. In various embodiments, the multi-evaporator coil configuration or setup enables the defrosting system or a refrigeration device equipped therewith to switch between the defrosting mode and the cooling mode using the second evaporator coil (120) without disrupting or halting normal or approximately normal operation of the first evaporator coil (110), e.g., during the defrosting mode the first evaporator coil (110) continues to provide evaporated refrigerant to a compressor (150). Moreover, during or throughout the defrosting mode, the operation of second evaporator coil (120) is not or need not be entirely shut down, such that during or throughout the defrosting mode the second evaporator coil (120) can continue to provide at least some evaporated refrigerant to the compressor (150).

[0040] The first evaporator coil (110) and second evaporator coil (120) may be fabricated with heat exchange elements, structures, or features such as outwardly protruding fins to increase the surface area contacting the incoming air, in a manner readily understood by individuals having ordinary skill in the relevant art. The incoming air brought into contact with the first evaporator coil (110) and second evaporator coil (120) is subsequently discharged from the second evaporator coil (120) as supply air, which is directed back into the internal cooling space to keep the goods stored therein cool. The first evaporator coil (110) and the second evaporator coil (120) are configured to reduce humidity of the incoming air, and adjust the temperature of the supply air within an intended temperature range or toward or to an intended or desired target temperature or temperature setpoint to facilitate or enable the preservation of the goods housed in the cabinet.

[0041] As indicated above, the surface of the second evaporator coil (120) is configured to have a second temperature which is lower than a first temperature of the surface of the first evaporator coil (110) throughout an operational or cooling mode of the evaporator unit (105). The surface temperature of the first evaporator coil (110) may be set at the first temperature, such as approximately 2 to -2°C, while the surface temperature of the second evaporator coil (120) is set at the second temperature such as approximately -5 to -15°C during the operational or cooling mode. Still more particularly, in some embodiments the first temperature and the second temperature are maintained at approximately 0°C and -10°C, respectively. The first evaporator coil (110) dehumidifies and pre-cools the incoming air, and initially brings the incoming air temperature towards or to the first temperature; then the second evaporator coil (120) further significantly reduces the temperature of the air that has passed across or through the first evaporator coil (110) from the first temperature towards or to the second temperature before discharging the further cooled air as the supply air. Thus, a refrigeration device or apparatus in accordance with an embodiment of the present disclosure which carries or is integrated with a defrosting system in accordance with an embodiment of the present disclosure provides at least two-stage cooling during a normal cooling mode of operation or cooling session.

[0042] Pursuant to additional details and / or other embodiments, the first temperature detector (130) and the second temperature detector (140) are deployed near or proximate or adjacent to the first evaporator coil (110) and the second evaporator coil (120), respectively. The first temperature detector (130) and the second temperature detector (140) are configured to measure a temperature of the incoming air (Kin) and a temperature of the supply air (Kout), respectively. Typically, the first temperature detector (130) is located at a position such that the temperature of the incoming air can be measured prior to crossing the first evaporator coil (110), and the second temperature detector (140) is deployed downstream of the second evaporator coil (120) to detect the temperature of the supply air that has passed across or through each of the first and the second evaporator coils (110, 120). It can be noted that in certain embodiments, the defrosting system can further include a third temperature detector or sensor (not shown) positioned to measure a third air temperature such as an intermediate temperature (Kint) of air that has passed across the surface of the first evaporator coil (110) but which has not yet passed across the surface of the second evaporator coil (120). The defrosting system’s processing unit (108) may utilize Kint for deriving the calculated indicator in association with or in addition to the temperature difference (Kdif) of the incoming air and the supply air to determine or decide the timing of commencing and / or terminating a defrosting session.

[0043] Further referring to Fig. lb, a manifold (170) is configured to circulate refrigerant through the various components, e.g., including the heat exchange related components, of the refrigeration device to support or enable a defrosting session controlled by the defrosting system. It can be noted that the first evaporator coil (110) and the second evaporator coil (120) are fluidically coupled or connected to the manifold (170) in a parallel manner for refrigerant circulation, and the first evaporator coil (110) and the second evaporator coil (120) are physically arranged in tandem to cool the air passing thereby, thereacross, or therethrough.

[0044] A first electronic expansion valve (EEV) (210) corresponding to the first evaporator coil (110) and a second EEV (220) corresponding to the second evaporator coil (120) are respectively disposed upstream, e.g., immediately upstream, of the first evaporator coil (110) and the second evaporator coil (120), and are configurable or configured to expand and channel the refrigerant into the first evaporator coil (110) and the second evaporator coil (120) according to programmable or predetermined parameters or settings with respect to flow rate, pressure, volume, etc. . .The first EEV (210) and the second EEF (220) can be in signal communication with and regulated or controlled by the processing unit (108).

[0045] The manifold (170) includes portions configured to exit from the first evaporator coil (110) and the second evaporator coil (120), and is configured converge to an input of a compressor (150). More particularly, the compressor (150) fluidically couples to the manifold (170) to receive refrigerant from the first evaporator coil (110) and the second evaporator coil (120). The compressor (150) compresses the refrigerant to generate a pressurized refrigerant that is guided into a condenser (160) located external to the cabinet. The condenser (160) is located downstream of the compressor (150) and is fluidically coupled or connected to the manifold (170) to receive the pressurized refrigerant from the compressor (150), after which the refrigerant is directed from the condenser (160) toward the first EEV (210) and the second EEV (220) and then toward evaporator coil (110) and the second evaporator coil (120). The condenser (160) is configured to dissipate heat from the pressurized refrigerant to the environment exterior to the compartment. With respect to the refrigerant circulating manifold (170) and the refrigerant flow therein, the first EEV (210) and the second EEV (220) are disposed upstream of the first evaporator coil (110) and the second evaporator coil (120), respectively, and are configured to manage or establish the pressure and volume of the refrigerant entering the first and second evaporator coils (110, 120). The first temperature and the second temperature can be adjusted or varied by way of regulating the volume, pressure, and / or flow rate of the refrigerant entering into the first evaporator coil (110) and the second evaporator coil (120).

[0046] In accordance with various embodiments of the disclosed system, the processing unit (108) associated with or implemented in the refrigeration device or the defrosting system is configured to reduce or minimize the frequency of defrosting sessions, e.g., minimizing or eliminating unnecessary defrosting sessions, and / or recognize the best times and / or conditions to carry out defrosting sessions. The processing unit (108) is configured to repeatedly or recurrently receive or acquire signals or data corresponding to Kin and Kout respectively corresponding to the first temperature detector (130) and the second temperature detector (140), and is configured to determine a temperature difference (Kdif) between Kin and Kout. In a number of embodiments, the temperature difference is the calculated indicator that the processing unit (108) utilizes to selectively control the operation of the defrosting system. The processing unit (108) is configurable or configured to switch from a normal operational mode such as a cooling mode of operation to a defrosting mode of operation in response to determining that the calculated indicator or Kdif exceeds a first selectable, programmable, or predetermined value, such as a first threshold value.

[0047] It can be noted that the first temperature is substantially the saturated temperature of the moisture in the air, and the second temperature is lower than the first temperature; hence, ice is formed only on the second evaporator coil (120). During a defrosting session corresponding to the defrosting mode, the cooling operation of the first evaporator coil (110) can remain uninterrupted while ice formed on the second evaporator coil (120) melts. The first evaporator coil (110) can thus remain operational or working throughout a defrosting session, and can continue to provide an intended or adequate level of cooling for the compartment during the defrosting session. To melt the ice around the second evaporator coil (120), the processing unit (108) is configured to increase or allow the increase of the second temperature associated with or corresponding to the surface of the second evaporator coil (120) to the first temperature, at which point the ice formed on the second evaporator coil (120) begins melting. In several embodiments, the second temperature is not or need not be raised greater than the first temperature.

[0048] It can be noted that the processing unit (108) can selectively or programmably regulate or establish the suction pressure at the first evaporator coil (110) by way of controlling the first EEV (210), and can selectively or programmably regulate or establish the suction pressure at the second evaporator coil (120) by way of controlling the second EEV (220). The processing unit (108) can thus respectively manage or control a first volume and pressure of refrigerant entering into the first evaporator coil (110) and a second volume and pressure of refrigerant entering the second evaporator coil (120) through the first EEV (210) and the second EEV (220), respectively, to regulate the first temperature corresponding to the surface of the first evaporator coil (110) and second temperature corresponding to the second evaporator coil (120), respectively. Correspondingly, one of the ways to increase or raise the second temperature without shutting down, e.g., entirely shutting down, the operation of the second evaporator coil (120) is by increasing a suction pressure at the second evaporator coil (120), for instance, in a manner indicated in Fig. 4. During a defrosting session in which the evaporator unit (105) operates in the defrosting mode, the processing unit (108) can manage or control a second suction pressure at the second evaporator coil (120) such that it is similar or nearly or essentially equal to a first suction pressure at the first evaporator coil (110), resulting in escalation of the second temperature toward or to the first temperature.

[0049] Prior to commencement of the defrosting mode in which the second temperature corresponding to the second evaporator coil (120) is increased or allowed to increase, the processing unit (108) is configured to repeatedly or recurrently collect or acquire Kin and Kout values from the first temperature detector (130) and the second temperature detector (140), respectively. The processing unit (108) repeatedly or recurrently determines or derives Kdif from these Kin and Kout values, and compares Kdif values with the first thoreshold value. Once the processing unit (108) determines that one or more Kdif values (e.g., an average or a maximum of n successive Kdif values) are equal to or exceed the first threshold value, the processing unit (108) is configured to switch the second evaporator coil (120) from its normal cooling mode to the defrosting mode. More specifically, the processing unit (108) can communicate with the second EEV (220) to establish or drive the second suction pressure at the second evaporator coil (120) up to a level generally near or approximately or essentially equal to the first suction pressure at the first evaporator coil (110). By adjusting, e.g., increasing, the second suction pressure, the second temperature of the second evaporator coil (120) inevitably rises toward or to the first temperature, which causes ice formed on the second evaporator coil to melt and corresponding water to drain off. In a number of embodiments, the first threshold value is between 1 and 2.5.

[0050] To attain optimal cooling in the refrigeration device, it is important or essential for the defrosting system to recognize the best timing switch from a defrosting session to or back to a normal cooling session. The processing unit (108) repeatedly or recurrently obtains Kin and Kout values from the first (130) and second temperature detectors (140), respectively, during the duration of the defrosting session to determine derive Kdif, and also recurrently or repeatedly compares Kdif values with a second selectable, programmable, or predetermined value, such as a second threshold value. In the event that one or more Kdif values (e.g., an average or a maximum of n successive Kdif values) become less than or equal to the second threshold value, the processing unit (108) is configured to switch or transition the second evaporator coil (120) back to a cooling mode of operation to reestablish or resume a cooling session. The processing unit (108) can control the second EEV (220) to reduce the suction pressure in the second evaporator coil (120), thus reducing the second temperature corresponding to the surface of the second evaporator coil (120), thereby transitioning the second evaporator coil (120) from a defrosting state to a cooling state, e.g., from its defrosting mode of operation to its normal cooling mode of operation. In several embodiments, the second threshold value is between 0.3 to 0.7. Both first predetermined value and second predetermined value can be different from the abovementioned ranges, depending on embodiment details and / or the overall properties and performance of the refrigeration device.

[0051] With reference to Fig. 5a and Fig. 5b, an embodiment of a defrosting system in accordance with the present disclosure provides a refrigeration device with a “smart defrost” mode of operation that is significantly more stable in terms of temperature fluctuation and suction pressure fluctuation compared to a conventional defrosting system that provides an “air static defrost” mode of operation in a conventional refrigeration device. With a multi-evaporator defroster in accordance with an embodiment of the present disclosure, a refrigeration device exhibits more stable suction pressure in each individual evaporator coil, leading to significantly less fluctuation in the cooling temperature of the storage compartment. Significantly more stable storage compartment temperature means reduced energy consumption, as well as better preservation of the goods stored in the refrigeration device. It was found by the inventor that first evaporator coil (110) and the second evaporator coil (120) can be configured to have a capacity ratio between 40 / 60 and 30 / 70 to yield significantly improved or best cooling and defrosting performance in a refrigeration device.

[0052] It is to be understood that the present disclosure may be embodied in other specific forms and is not limited to the embodiments described above. While features, aspects, and / or advantages associated with certain embodiments have been described above, other embodiments may also exhibit such features, aspects, and / or advantages, and not all embodiments need necessarily exhibit such features, aspects, and / or advantages to fall within the scope of the present disclosure and / or the corresponding claims. It will be appreciated by a person of ordinary skill in the art that one or more disclosed structures, components, or alternatives thereof can be desirably combined into alternative structures, components, and / or applications. In addition, various modifications, alterations, and / or improvements may be made to various embodiments by a person having ordinary skill in the relevant art while remaining within the scope of the present disclosure, which is limited only by the following claims.

Claims

Claims1. A defrosting system for a refrigeration device, comprising: an evaporator unit configured to receive refrigerant from an expansion device unit, and configurable or configured to evaporate received refrigerant and deliver evaporated refrigerant to a compressor; a temperature detector unit; and a processing unit, wherein: the evaporator unit is installable or installed external to an internal storage compartment of a cabinet of the refrigeration device; the evaporator unit includes a first evaporator coil and a second evaporator coil; the first evaporator coil is configured to operate at a first temperature and the second evaporator coil is configured to operate at a second temperature which is lower than the first temperature during a cooling mode of operation, and the second evaporator coil is configured to operate at a second temperature that increases toward or to the first temperature during a defrosting mode of operation; the temperature detector unit includes a first temperature detector corresponding to an air inlet side of the first evaporator coil and is configured to detect a return air temperature from the cabinet, and a second temperature detector corresponding to an air outlet side of the second evaporator coil and is configured to detect a supply air temperature provided to the cabinet; and the processing unit is configured to obtain or acquire temperature values from the first and second temperature detectors, and is configured to calculate a temperature difference between the return air temperature and the supply air temperature, and compare the temperature difference with a first threshold value to selectively switch the defrosting system between the cooling mode of operation and the defrosting mode of operation based on the calculated temperature difference.

2. The defrosting system of claim 1, wherein the first temperature is correlated with or corresponds to a surface temperature of the first evaporator coil, the second temperature is correlated with or corresponds to a surface temperature of the second evaporator coil, and the processor is configured to enable the second temperature to increase toward or to the first temperature during the defrosting mode.

3. The defrosting system of claim 2, wherein the processor is configured to control a first volume of refrigerant entering into the first evaporator coil and a second volume of refrigerant entering into second evaporator coil by way of a first expansion valve and a second expansion valve of the expansion valve unit to thereby regulate the surface temperature of the first evaporator coil and the surface temperature of the second evaporator coil, respectively.

4. The defrosting system of claim 1, wherein the processor is configured to switch the second evaporator coil from the cooling mode of operation to the defrosting mode of operation in the event that the temperature difference exceeds the first threshold value.

5. The defrosting system of claim 4, wherein the first threshold value is between 1 and 2.5.

6. The defrosting system of claim 1, wherein the first evaporator coil and the second evaporator coil are arranged in tandem such that air flowing through the evaporator unit flows across the first evaporator coil before flowing across the second evaporator coil.

7. The defrosting system of claim 4, wherein during the cooling mode of operation a surface of the first evaporator coil is configured to have a temperature between 1°C to -0.5°C, and a surface of the second evaporator coil is configured to have a temperature between -5 to - 15°C.

8. The defrosting system of claim 4, wherein the processing unit resumes or reestablishes the cooling mode of operation upon determining that the calculated indicator is less than or equal to a second threshold value, which is less than the first threshold value.

9. The defrosting system of claim 9, wherein the second threshold value is between 0.3 and 0.7.

10. The defrosting system of claim 2, wherein the first evaporator continues to cool air passing thereacross and the second evaporator coil operates without being entirely shut down during or throughout the defrosting mode of operation.

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