Method of controlling defrosting of an air handling system

Abstract

A computer system comprising processing circuitry (31) configured to evaluate a defrosting event (90) in an air handling system (1), wherein the processing circuitry (31) is further configured to: receive upstream pressure data (51) of an exhaust air part (11) of the air handling system (1) after the defrosting event (90); receive downstream pressure data (52) of the exhaust air part (11) after the defrosting event (90); determine a pressure drop (50) of the exhaust air part (11) based on the upstream pressure data (51) and the downstream pressure data (52) after the defrosting event (90); evaluate the defrosting event (90) at least based on the determined pressure drop (50); and adapting the length of the defrosting event (90) based on said evaluation.

Description

[0001] METHOD OF CONTROLLING DEFROSTING OF AN AIR HANDLING SYSTEM

[0002] TECHNICAL FIELD

[0003] The present invention relates in general to the field of air handling systems. More specifically, the present invention relates to a method of controlling defrosting of an air handling system and an associated computer system.

[0004] BACKGROUND

[0005] It is well known that air conditioning systems are in need of defrosting as the outdoor ambient temperature drops during the colder months of the year. This is because the moisture in the air begins to freeze on the heat exchanger. As a result, a defrost cycle is triggered to avoid build-up of ice on the heat exchanger, which would otherwise impair the function of the air handling system (also referred to as an air treatment system) in terms of decreased efficiency.

[0006] Several variants for controlling defrosting of air treatment systems have been proposed over the years, see for instance EP2546581B1. However, there is always room for improvements.

[0007] SUMMARY

[0008] An object of the present invention is to solve or at least mitigate the problems related to prior art. This object is achieved by means of the technique set forth in the appended independent claims; preferred embodiments being defined in the related dependent claims.

[0009] In a first aspect, a computer system comprising processing circuitry configured to evaluate a defrosting event in an air handling system is provided. The processing circuitry is further configured to receive upstream pressure data of an exhaust air part of the air handling system after the defrosting event, receive downstream pressure data of the exhaust air part after the defrosting event, determine a pressure drop of the exhaust air part based on the upstream pressure data and the downstream pressure data after the defrosting event, evaluate the defrosting event at least based on the determined pressure drop, and controlling the length of the defrosting event based on said evaluation. A technical benefit may be that the defrosting event is optimized based on the current operating conditions. Yet a further technical benefit may include optimizing the defrosting process based on real-time pressure data, leading to improved system efficiency and reduced energy consumption compared to static defrosting methods.

[0010] In one embodiment, the evaluation is further based on statistical and / or historical data of previous defrosting events. A technical benefit may include enhancing the accuracy of defrosting evaluations by incorporating historical data, which allows for more informed adjustments and prevents unnecessary defrosting cycles.

[0011] In one embodiment, the evaluation is further based on time data of previous defrosting events. A technical benefit may include utilizing time data to better predict defrosting needs, thereby reducing wear on system components by avoiding excessive defrosting.

[0012] In one embodiment, the evaluation further comprises determining whether a desired level of defrosting has been reached. A technical benefit may include ensuring that defrosting is only considered complete when a desired level is achieved, thereby maintaining optimal heat exchanger performance and energy efficiency.

[0013] In one embodiment, controlling the length of the defrosting event comprises adapting the length to be either shorten or lengthen. A technical benefit may include dynamically adjusting the defrosting duration to suit current conditions, which can extend the system's lifespan and improve overall performance.

[0014] In one embodiment, the evaluation further comprises determining whether a desired level of defrosting has been reached, and wherein upon determining that a desired level of defrosting has not been reached the processing circuitry is configured to lengthen the length of the defrosting event. A technical benefit may include dynamically adjusting the defrosting duration to suit current conditions, which can extend the system's lifespan and improve overall performance.

[0015] In one embodiment, the evaluation further comprises determining whether a desired level of defrosting has been reached, wherein upon determining that a desired level of defrosting has been reached in the current defrosting event, the processing circuitry is configured to shorten the length of the defrosting event. A technical benefit may include reducing unnecessary energy use by shortening the defrosting cycle once the desired level is reached, thus optimizing operational costs.

[0016] In one embodiment, the evaluation further is based on statistical and / or historical data of previous defrosting events, and wherein upon determining that a desired level of defrosting has been reached in the current defrosting event, the processing circuitry is further configured to determine if desired level of defrosting has been reached in a predetermined number of defrosting events, in a sequence of previous defrosting events, and if so, the processing circuitry is configured to shorten the length of the defrosting event. A technical benefit may include leveraging statistical data to identify consistent defrosting success, enabling the system to progressively reduce cycle times and improve efficiency.

[0017] In one embodiment, the evaluation further is based on statistical and / or historical data of previous defrosting events, and wherein upon determining that a desired level of defrosting has been reached in the current defrosting event, the processing circuitry is further configured to determine if desired level of defrosting has been reached in a predetermined number of defrosting events, during a time period, and if so, the processing circuitry is configured to shorten the length of the defrosting event. A technical benefit may include analyzing past defrosting success over time to intelligently adjust future cycle durations, enhancing system reliability and energy conservation.

[0018] In a second aspect, an air handling system is provided. The air handling system comprises a computer system according to the first aspect. A technical benefit may include integrating an intelligent computer system into the air handling unit, which enhances the system's adaptability to varying environmental conditions.

[0019] In one example, the air handling system further comprises a heat exchanger comprising an exhaust air part and a supply air part, wherein the heat exchanger is configured to transfer heat from warm exhaust air, that flows into the system through the exhaust air part, to cold supply air, that flows into the system through the supply air part, a bypass, and a damper arrangement, configured to open and close the bypass and the supply air part on an upstream side the supply air part. In a third aspect, a computer-implemented method is provided. The computer- implemented method comprises receiving upstream pressure data of an exhaust air part of the air handling system after the defrosting event, receiving downstream pressure data of the exhaust air part after the defrosting event, determining a pressure drop of the exhaust air part based on the upstream pressure data and the downstream pressure data after the defrosting event, evaluating the defrosting event at least based on the determined pressure drop, and controlling the length of the defrosting event based on said evaluation.

[0020] In a fourth aspect, a computer program product is provided comprising program code for performing, when executed by the processing circuitry, the method of the third aspect.

[0021] In a fifth aspect, a non-transitory computer-readable storage medium is provided comprising instructions, which when executed by the processing circuitry, cause the processing circuitry to perform the method of the third aspect.

[0022] It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. All terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [element, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of the element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments. FIGS. 1A-D are different views of an air handling system, where FIG. 1A is a side view, FIGS. 1B-C are isometric views and FIG. ID is a view of a damper of the air handling system.

[0025] FIGS. 2A-B are schematic views of an air treatment system according to two examples.

[0026] FIGS. 3A-B are schematic views of the functionality of a computer system according to examples.

[0027] FIG. 4 is a schematic view of the functionality of an air handling system according to one example.

[0028] FIGS. 5A-B are schematic illustrations of a method of controlling defrosting of the air handling system;

[0029] FIGS. 6A-B are schematic illustrations of a method of controlling defrosting of the air handling system;

[0030] FIG. 6 is a schematic view of the functionality of a computer system according to an example; and

[0031] FIG. 7 is a schematic view of the functionality of a computer system according to an example.

[0032] DETAILED DESCRIPTION OF EMBODIMENTS

[0033] Embodiments of the invention will now be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

[0034] FIG. 1 shows an air handling system 1, also referred to as an air treatment system or air handling unit. The system 1 has an interior part 2, a center part 3 and an exterior part 4. The center part 3 includes a heat exchanger 10 that is configured to transfer heat from warm exhaust air W to cold supply air C. The warm exhaust air W flows into the system 1 via a filter unit 5 arranged in an exhaust air passage 6 of the interior part 2 and out from the system 1 via an exhaust air fan 7 in the exterior part 4. There between, the warm exhaust air W passes an exhaust air part 11 of the heat exchanger 10. Correspondingly, the cold supply air C flows into the system 1 via a corresponding filter unit 5’ arranged in a supply air passage 8 of the exterior part 4 and out from the system 1 via a supply air fan 9 in the interior part 2. There between, the cold supply air C passes a supply air part 12 of the heat exchanger 10. The supply air part 12 is separated from the exhaust air part 11.

[0035] Cold supply air C can also flow through a bypass 13 instead of through the heat exchanger 10. The bypass 13 is preferably provided in the center part 3 of the air treatment system 1 and is configured to communicate with the supply air passage 8 and the supply air fan 9. Moreover, the bypass 13 communicates with the supply air passage 8 upstream of the supply air part 12, and with the supply air fan 9 downstream of the supply air part 12.

[0036] A damper arrangement 20 is provided upstream of the supply air part 12 of the heat exchanger 10. The damper arrangement 20, also referred to as a damper 20, is divided into at least two parts, such as three parts 21-23. The parts 21-23 are preferably individually controllable.

[0037] The first part 21 can be operated in three different ways. Alternative (A) to prevent or stop supply air C from flowing into the bypass 13, alternative (B) to allow a predetermined throttled inflow of supply air C into the bypass 13, or alternative (C) to allow an unthrottled inflow of supply air C into the bypass 13.

[0038] The second part 22 can in turn be operated in two ways. Alternative (D) to prevent supply air C from flowing into a first half 14 of the supply air part 12 of the heat exchanger 10, or alternative (E) to allow an unthrottled inflow of supply air C into the first half 14 of the supply air part 12.

[0039] Finally, also the third part 23 can be operated in two ways. Alternative (F) to prevent supply air C from flowing into a second half 15 of the supply air part 12 of the heat exchanger 10, or alternative (G) to allow an unthrottled inflow of supply air C into the second half 15 of the supply air part 12. All parts 21-23 of the damper 20 can be individually controlled, for instance by an actuator. They may be opened or closed fully or partly, for instance via blades that are controlled by the actuator.

[0040] In its normal position, i.e. under normal heat exchange, the supply air part 12 is fully open and the bypass 13 is closed by the damper 20. Furthermore, a certain predetermined pressure drop is present across the exhaust air part 11.

[0041] In one embodiment, the air treatment system 1 comprises a heat exchanger 10 comprising an exhaust air part 11 and a supply air part 12, wherein the heat exchanger 10 is configured to transfer heat from warm exhaust air W, that flows into the system 1 through the exhaust air part 11, to cold supply air C, that flows into the system 1 through the supply air part 12. The air treatment system 1 further comprises a bypass 13, and a damper arrangement 20, configured to open and close the bypass 13 and the supply air part 12 on an upstream side the supply air part 12, wherein the damper arrangement 20 comprises three parts 21-23. The first part 21 is adapted to prevent supply air C from flowing into the bypass 13, to allow a predetermined throttled inflow of supply air C into the bypass 13 or to allow an unthrottled inflow of supply air C into the bypass 13. The second part 22 is adapted to prevent supply air I from flowing into in a first half 14 of the supply air section 12 of the heat exchanger 10 or to allow an unthrottled inflow of supply air C into said first half 14. The third part 23 is adapted to prevent supply air C from flowing into a second half 15 of the supply air section 12 of the heat exchanger 10 or to allow an unthrottled inflow of supply air C into said second half 15. In its normal position, in one example, the system 1 works with a pressure drop across an exhaust air part 11 of a heat exchanger 10 and with a fully closed bypass 13 and a fully open supply air part 12. The pressure drop may be a predetermined pressure drop. In one example, the system 1 works with a pressure drop that is measured during dry non-condensing conditions. In one example, the pressure drop is measured individually for each unit in dry non-condensing conditions and saved in a memory. This data may then be used to determine the one or more threshold values.

[0042] In one example, the system 1 further comprises an exhaust air passage 6 and an exhaust air fan 7, wherein heat transferred from the warm exhaust air W flows into the system 1 via the exhaust air passage 6 and out from the system 1 via the exhaust air fan 7, and there between passes through the exhaust air part 11.

[0043] In one example, the system 1 further comprises a supply air passage 8 and a supply air fan 9, wherein the cold supply air C flows into the system 1 via the supply air passage 8 and out from the system 1 via the supply air fan 9 and there between passes through the supply air part 12.

[0044] In one example, the supply air part 12 is separate from the exhaust air part 11.

[0045] Turning to FIG. 2A, a schematic illustration of the air treatment system 1 is shown. The air treatment system 1 comprises a heat exchanger 10, a bypass 13 and a damper arrangement 20. The damper arrangement 20 comprises a first part 21 and a second part 22. In an optional embodiment the damper further comprises a third part 23. The system 1 further comprises a computer system 30.

[0046] The computer system 30 may be implemented as one or more processors (CPU) or programmable logic circuits (PLC), which is connected to or comprises a memory 32. The memory 32 may be implemented using any commonly known technology for computer-readable memories such as ROM, RAM, SRAM, DRAM, CMOS, FLASH, DDR, SDRAM or some other memory technology. The memory 32 may be configured to store data relating to the operation of the heat exchanger and / or the air handling unit. The computer system 30 may be arranged as a part of a computer system or as a separate unit being in communication with a computer system.

[0047] In one embodiment the computer system 30 further comprises or is connected to a communication interface 34. The communication interface may for example be a wireless radio frequency interface such as a WiFi link or short-range communication technologies such as short-range standards IEEE 802.11, IEEE 802.15, ZigBee, WirelessHART, WIFI and Bluetooth® to name a few. Moreover, communications may also be based on transferring data via loT-services (Internet of Things). In different embodiments of the invention, different loT-protocols may be utilized. For instance, protocols include, but are not limited to Bluetooth®, WiFi, ZigBee, MQTT loT, CoAP, DDS, NFC, AMQP, LoRaWAN, RFID, Z-Wave, Sigfox, Thread, EnOcean, celluarly based communication protocols, or any combination thereof. The computer system 30 may be a cloud-computing system 30 being included in a distributed cloud network widely and publicly available, or limited to an enterprise cloud. For instance, cloud-computing technologies include, but are not limited to Amazon EC2, Google App Engine, Firebase or Apple iCloud.

[0048] Hence, in the example of FIG. 2A, the computer system 30 is integrated into the air treatment system 1. In an optional example, as shown in FIG. 2B, the computer system 30 is external of the air treatment system 1. The air treatment system 1 may comprise a controller 29 that is in operative communication with the computer system 30. As would be understood by a person skilled in the art, the functionalities described to the internal computer system can be applied to the external computer system as well.

[0049] FIGS. 3A-B are illustrative examples of the functionality of the computer system 30. The computer system 30 is configured to receive upstream pressure data 51. The computer system 30 is further configured to receive downstream pressure data 52. The downstream or upstream pressure data may be determined by any pressure sensor known in the art. In an alternative embodiment, the computer system 30 is configured to receive pressure differential data, indicative of the pressure difference between the upstream pressure data 51 and the downstream pressure data 52. The pressure differential data may be determined by a differential pressure sensor, and / or multiple pressure sensors. The computer system 30 may be configured to determine a pressure drop 50 based on the upstream pressure data 51 and the downstream pressure data 52. Based on the determined pressure drop 50, the computer system 30 may transmit a defrosting cycle signal 61 to initiate a defrosting event.

[0050] The upstream pressure data 51 may be pressure data upstream of an exhaust air part 11 of the air treatment system 1. The downstream pressure data 52 may be pressure data downstream of an exhaust air part 11 of the air treatment system 1.

[0051] In FIG. 4, a schematic view of the functionality of an air treatment system according to one example is illustrated, wherein the air treatment system 1 may be operated in a defrosting event 90 or in normal operation 92. A defrosting event 90 may comprise a timed defrosting cycle, which is divided into two consecutive periods, namely a first period, during which an inflow of supply air C into the bypass 13 is partially throttled, an inflow of supply air C into the first half 14 of the supply air part 12 of the heat exchanger 10 is stopped and an inflow of supply air C into the other half 15 of the supply air part 12 of the heat exchanger 10 is unthrottled, and a second period, during which an inflow of supply air C into the bypass 13 is partially throttled, an inflow of supply air C into the first half 14 of the supply air part 12 of the heat exchanger 10 is unthrottled, and an inflow of supply air C into the other half 15 of the supply air part 12 of the heat exchanger 10 is stopped. A normal operation 92 may comprise normal heat exchange functionality.

[0052] Once the defrosting event 90 is completed, the computer system 30 is configured to determine the pressure drop 50. The computer system 30 is configured to perform a defrosting evaluation 60. The computer system 30 then evaluates if the defrosting event was sufficient. The evaluation is preferably based on said pressure drop 50. In one example, the computer system 30 is configured to perform a defrosting evaluation 60 by comparing the determined pressure drop 50 against a predetermined threshold value 61.

[0053] In one example, the defrosting event 90 is sufficient or successful if the air treatment system 1 is defrosted. In one example, the defrosting event 90 is sufficient or successful if the pressure drop 50 in the air treatment system 1 is below a predetermined threshold. The predetermined threshold may in some examples be referred to as a level. The pressure drop may indicate a successful defrosting event 90 as the predetermined threshold indicates a pressure measured during dry conditions. Stated differently, if the pressure drop reaches to or below a level as indicated by the predetermined threshold, the pressure is at it would be in dry conditions or at a level based thereon. Therefore, this pressure drop indicates a successful defrosting event 90. Notably, the predetermined threshold typically does not match the pressure drop during dry conditions. Rather, it is a predetermined threshold at a predetermined value based thereon. In an alternative example, a successful defrosting event is sufficient or successful if the pressure drop 50 is within an interval.

[0054] If the computer system 30 determines that the defrosting event 90 was sufficient or successful, the computer system 30 continues to detect an increased pressure drop according to its normal operation mode 92. The defrosting event 90 is thus finished. In one example, the computer system 30 is configured to store the details of the defrosting event 90. The details of the defrosting event 90 may relate to defrosting time, ambient data, pressure data, time of the day, time of the year, etc..

[0055] The computer system 30 may further be configured to evaluate the historical / statistical data relating to previous defrosting events 90. If the computer system 30 determines that the defrosting event 90 was sufficient, in a predetermined number of times in a sequence, the computer system 30 adapts the length of the defrosting event 90. In other words, if the computer system 30 determines that the pressure drop, after a defrosting event 90, is below the predetermined threshold value 61, in a predetermined number of times in a sequence the computer system 30 adapts the length of the defrosting event 90. The length of the defrosting event 90 is shortened. In other words, the defrosting event 90 is shorter in time.

[0056] The number of times in a sequence may be any suitable number. In one nonlimiting example, the number is 2 - 5 times. However, other intervals are also possible.

[0057] If the computer system 30 determines that the pressure drop has not been reached, after a defrosting event 90, the computer system 30 adapts the length of the defrosting event 90. The length of the defrosting event 90 is lengthened. In other words, the defrosting event 90 is longer in time. In other words, if the computer system 30 determines that the defrosting event 90 was insufficient, the computer system 30 adapts the length of the defrosting event 90.

[0058] The computer system 30 may further be configured to evaluate the historical / statistical data relating to previous defrosting events 90. In one example, if the computer system 30 determines that the pressure drop have not been reached, after a defrosting event 90, in a predetermined number of times in a sequence, the computer system 30 adapts the length of the defrosting event 90.

[0059] In one example, if the computer system 30 determines that the pressure drop have not been reached, after a defrosting event 90, in a predetermined number of times during a time interval, the computer system 30 adapts the length of the defrosting event 90.

[0060] The "desired level of defrosting" may be defined as the specific state where the air handling system is effectively cleared of ice accumulation that could hinder its performance. This state is quantitatively assessed by measuring the pressure drop across the exhaust air part of the heat exchanger. The desired level of defrosting is achieved when this pressure drop reaches or falls below a predetermined threshold, established based on pressure readings taken under dry, non-condensing conditions, which serve as a baseline for successful defrosting. In certain embodiments, the desired level may be characterized by a pressure drop within a specific range, ensuring the heat exchanger operates efficiently without unnecessary defrosting cycles. Additional operational parameters, such as ambient temperature, humidity levels, and airflow rates, may also influence the desired level, enabling the evaluation to adapt the defrosting process to current environmental conditions.

[0061] Following a defrosting event, the computer system conducts a defrosting evaluation by comparing the measured pressure drop against the predetermined threshold. If the pressure drop is at or below this threshold, the defrosting event is deemed successful, indicating that the desired level has been reached. If not, the system is configured to automatically adjust the duration of subsequent defrosting events, maintaining optimal performance while minimizing energy consumption and system wear. To enhance the evaluation's accuracy, historical and statistical data from previous defrosting events may be analyzed. This data aids in refining the threshold levels and adapting the system to varying operational conditions, ensuring that the desired level of defrosting is consistently achieved.

[0062] The adaptation of the length of the defrosting event allows the system to dynamically adjust to varying operational conditions to ensure optimal performance. The computer system may employ various criteria to determine when and how to adjust the defrosting cycle duration. Primarily, the adjustment is based on the pressure drop measured across the exhaust air part of the heat exchanger. When this pressure drop deviates from a predetermined threshold, it signals that the previous defrosting event may have been either insufficient or overly extensive. Environmental conditions may also play a role in this adaptive process. Factors such as ambient temperature, humidity levels, and airflow rates may be continuously monitored to provide context for the pressure drop readings. For instance, during periods of high humidity or lower ambient temperatures, the system might anticipate more rapid ice formation, prompting it to extend the defrosting cycle proactively. Conversely, in drier, warmer conditions, the system may decide to shorten the defrosting cycle if the pressure drop indicates that less ice has formed. Additionally, the system may incorporate historical and statistical data from previous defrosting events to refine its adaptive logic. By analyzing past performance under similar conditions, the system can predict the necessary adjustments more accurately, thereby optimizing defrosting efficiency and minimizing energy consumption.

[0063] In one example, the computer system 30 further comprises an alarm function for providing feedback to the user based on the evaluation of a defrosting event 90. The alarm signal may for example be transmitted upon determining that a predetermined number of defrosting events have been unsuccessful / unsatisfactory. The alarm signal may be configured to provide urgent feedback to the user of the system 1. The alarm signal is intended to notify users promptly, allowing for timely intervention to prevent potential inefficiencies or issues within the system. The alarm function can be tailored to suit different user environments and preferences through various alert methods. These may include auditory signals, such as a siren or beep, to draw immediate attention, and visual signals, such as blinking lights or a change in display color, to clearly indicate an alert status. For environments where noise may interfere with auditory signals, haptic feedback, like vibrations, could be employed, especially in portable devices or control panels. Additionally, although less common, olfactory signals might be utilized in specific industrial settings for enhanced efficacy. The alarm may for example be a loud sound, a blinking lamp, a bright color or the like.

[0064] In one embodiment the alarm function further comprises a communication interface for contacting the user with important information. For instance, alerts could be delivered as text messages, emails, or app-based notifications to a mobile phone, tablet, or any connected device, which is particularly beneficial for users managing multiple systems or not in close proximity to the air handling system. The communication interface may be a wireless radio frequency interface such as a Bluetooth™ or a WiFi (IEEE802.1 lb standard) link. The communication interface may also be a wired interface. The communication interface may be configured to send an alarm as a text-message, Bluetooth signal, email or the like to the user informing him / her of the detected condition. The communication interface may be configured to send information regarding a defrosting event to a mobile communications terminal of a user. The mobile communications terminal may be a mobile phone, a tablet computer, a personal digital assistant, a media player, a location finding device or generally any hand-held, user-carried or user-worn device capable of communicating with other devices.

[0065] FIGS. 5 A and 5B shows illustrative examples of a computer implemented method. In the example of FIG. 5 A, the method comprises receiving 102 upstream pressure data 51 of an exhaust air part 11 of the air treatment system 1 after the defrosting event 90 and receiving 104 downstream pressure data 52 of the exhaust air part 11 after the defrosting event 90. The method further comprises determining 106 a pressure drop 50 of the exhaust air part 11 based on the upstream pressure data 51 and the downstream pressure data 52 after the defrosting event 90 and evaluating 108 the defrosting event 90 at least based on the determined pressure drop 50. The method further comprises controlling 110 the length of the defrosting event 90 based on said evaluation.

[0066] FIG. 5B shows an example where the method further comprises obtaining 107 time data, statistical data and / or historical data of the defrosting event 90. The evaluation step 108 further comprises evaluating the pressure drop 50 as well as one or more of: time data, statistical data and historical data of the defrosting event 90. The step of controlling the defrosting event 90 comprises alternating the time of the defrosting event 90. The method may comprise shortening 110a the length of the defrosting event 90 or lengthen 110b the length of the defrosting event 90.

[0067] In the below, an example of controlling a defrosting event 90 is described.

[0068] The method optionally comprises a non-illustrated step of measuring the pressure upstream of the exhaust air part 11.

[0069] The method comprises receiving 102 the upstream data 51. In some examples, the method comprises receiving 102 upstream pressure data from a sensor or a communications unit connected to the sensor.

[0070] The method optionally comprises a non-illustrated step of measuring the downstream pressure of the exhaust air part 11, preferably before the exhaust air fan. The method comprises receiving 104 the downstream data 52. In some examples, the method comprises receiving 102 upstream pressure data from a sensor, or a communications unit connected to the sensor.

[0071] The method further determining 106 the pressure drop across the exhaust air part 11. In some embodiments, the determining 106 comprises calculating the difference between the received data from steps 102 and 104.

[0072] If it is determined that there is an increased pressure drop as compared to the predetermined value of the normal mode, the method continues by;

[0073] Evaluating 108 a defrosting event, the evaluating comprising performing a timed defrosting cycle, which is divided into two consecutive periods; a first period and a second period. During the first period, an inflow of supply air C into the bypass 13 is partially throttled, an inflow of supply air C into the first half 14 of the supply air part 12 is stopped and an inflow of supply air C into the other half 15 of the supply air part 12 is unthrottled. During the second period, an inflow of supply air C into the bypass 13 is partially throttled, an inflow of supply air C into the first half 14 of the supply air part 12 is unthrottled, and an inflow of supply air C into the other half 15 of the supply air part 12 is stopped.

[0074] After the defrosting cycle has been performed:

[0075] The evaluating 108 may further comprise re-measuring the pressure drop across the exhaust air part 11 of the heat exchanger 10 (step S20 corresponds to the combination of steps S1-S10), and,

[0076] The evaluating 108 may yet further comprise determining whether a desired level of defrosting has been reached. The desired level of defrosting may correspond to a predetermined pressure drop level that lies within a predetermined pressure drop value range.

[0077] Optionally, if the predetermined pressure drop level has not been reached; repeating the timed defrosting cycle described above, directly or after a stabilization period, by a new time period changed to a longer time period.

[0078] If the pressure drop level has been reached several times in a row, the method comprises controlling 110 the defrosting cycle by shortening 110a the length of the defrosting event or lengthening 110b the length of the defrosting event. In one example, the method of controlling defrosting of an air treatment system 1 includes the general steps of: measuring a pressure drop on the heat exchanger to determine a reference value,

[0079] - based on the reference value, o determining the limits for a permissible pressure increase, and o determining what an approved defrosting means in terms of pressure

[0080] - when the upper limit for permissible pressure increase is reached, a defrosting cycle is activated, i.e. o the first part 21 of the damper 20 is closed and the bypass 13 is opened slightly to compensate for the increased pressure drop. o After a predetermined time period, the first part 21 opens again while the adjacent part 22 is closed for an equal period of time. o The above steps are repeated through as many parts 21-23 as necessary. In one example, the pressure drop limits are flow-dependent. In one example, when all parts 21-23 have been passed through, all parts 21-23 are opened and the bypass 13 is closed, and a step of checking whether the pressure has fallen below the approved defrosting level (which is also flow dependent) is performed. If the approved level has not been reached after a defrosting cycle, the defrosting is repeated again, i.e. the first part 21 closes, the bypass 13 opens slightly, etc.

[0081] In one example, several unsatisfactory defrosting cycles in a row result in an alarm. The optional alarm function has been previously described. The alarm function may result in a termination of the process.

[0082] In one example, if the pressure is below the approved level, full recycling of hot air / energy continues until the maximum allowable pressure drop increase is reached again, which then triggers a new defrosting cycle.

[0083] In one example, the method described above may also be referred to as an unintelligent adaptive control mechanism. The idea is to have a modulated defrosting mechanism that is performed over at least two mechanical defrosting sections, such as over three or more mechanical defrosting sections 21-23.

[0084] The time periods described above may be applied as follows; o Defrosting for a predetermined time period, such as during 6 min o Determining whether the unit is sufficiently defrosted. If the answer is YES, the defrosting is shut down. If the answer is NO, another time period is added, such as a period of 1 min. o After the preceding check and possible further defrosting period, determining, once again, whether the unit is sufficiently defrosted, and so on.

[0085] In the case where there are three individually controllable defrosting sections 21-23, the first defrosting section 21 may be defrosted for 6 min. Next, the second defrosting section 22 may be defrosted for 6 min. This is in contrast to prior art examples that make use of four defrosting periods, which is much more cumbersome. The simplified design proposed in the description above is simpler and more efficient.

[0086] FIG. 6A shows an example of a defrosting sequence with two recycling parts. In FIG. 6A the pressure 1 & 2 are measured pressure drop across the heat exchanger, S. A.x is the Damper actuator for heat exchange having fixed levels when defrosting, S.B.x is the Damper actuator for bypass having adjustable level when defrosting, Tl-3 is the adjustable time (60-600s). If defrosting is repeated and lasts a total of > 3h, an alarm may be activated.

[0087] FIG. 6B shows an example of a defrosting sequence with two recycling parts. In FIG. 6B, the pressure 1 & 2 are measured pressure drop across the heat exchanger, S. A.x is the damper actuator for heat exchange having fixed levels when defrosting, S.B.x is the damper actuator for bypass having adjustable level when defrosting, Tl-3 is and adjustable time (60-600s). If defrosting is repeated and lasts a total of > 3h, an alarm may be activated.

[0088] It should be noted that in the specific examples of FIGS. 6A-B, the computer system is not configured to shorten the defrosting event 90 upon successful defrosting events. However, as would be readily understood, these steps could be added to the method described in FIGS 6A-B.

[0089] As shown in FIG. 7, the computer system 30 may be configured to receive different kinds of data. The data may for example relate to one or more of: indoor temperature 72, outdoor temperature 73, humidity 74 (indoor and / or outdoor), light levels 75, energy prices 76, weather forecast data 77, precipitation 78 outside, time data 79, pressure data, RPM data, air flow data (such as for example air flow or mass flow), power, torque, effect data, statistical and / or historical information. The time data may relate to time of the day, and / or the time of the week, month or year. The pressure data may be pressure data indicating the pressure in various parts of the air treatment system such as the exhaust air part, and the outdoor / indoor pressure. The RPM data may indicate the current RPM of a fan in the air treatment system. The air flow data may be indicative of the airflow through the air treatment system. The effect data may be indicative of the current energy or effect usage of the air treatment system. The data is preferably obtained by a sensor, either locally arranged in the computer system 30 or external of the system. The data may further be received from a communication interface.

[0090] The computer system 30 may comprise at least one computing device or electronic device capable of including firmware, hardware, and / or executing software instructions to implement the functionality described herein. The computer system

[0091] 30 may include processing circuitry 31 (e.g., processing circuitry including one or more processor devices or control units), a storage unit 32, and a system bus. The computer system 30 may include at least one computing device having the processing circuitry

[0092] 31. The system bus provides an interface for system components including, but not limited to, the storage unit 32 and the processing circuitry 31. The processing circuitry

[0093] 31 may include any number of hardware components for conducting data or signal processing or for executing computer code stored in storage unit 32. The processing circuitry 31 may, for example, include a general-purpose processor, an application specific processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a circuit containing processing components, a group of distributed processing components, a group of distributed computers configured for processing, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processing circuitry 31 may further include computer executable code that controls operation of the programmable device. The storage unit 31 may be run on a cloud-computing platform, and connection may be established using DBaaS (Database-as-a-service). For instance, the storage unit 31 may be deployed as a SQL data model such as MySQL, PostgreSQL or Oracle RDBMS. Alternatively, deployments based on NoSQL data models such as MongoDB, Hadoop or Apache Cassandra may be used. DBaaS technologies include, but are not limited to Amazon Aurora, EnterpriseDB, Oracle Database Cloud Service or Google Cloud. Preferably, the storage unit 31 is deployed on the same platform as the computer system 30 deployment given that the computer system 30 is deployed in such a system.

[0094] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

CLAIMS1. A computer system comprising processing circuitry (31) configured to evaluate a defrosting event (90) in an air handling system (1), wherein the processing circuitry (31) is further configured to: receive upstream pressure data (51) of an exhaust air part (11) of the air handling system (1) after the defrosting event (90); receive downstream pressure data (52) of the exhaust air part (11) after the defrosting event (90); determine a pressure drop (50) of the exhaust air part (11) based on the upstream pressure data (51) and the downstream pressure data (52) after the defrosting event (90); evaluate the defrosting event (90) at least based on the determined pressure drop (50); and controlling the length of the defrosting event (90) based on said evaluation.

2. A computer system according to claim 1, wherein the evaluation is further based on statistical and / or historical data of previous defrosting events (90).

3. A computer system according to claim 1 or 2, wherein the evaluation is further based on time data of previous defrosting events (90).

4. A computer system according to any of claim 1 - 3, wherein the evaluation further comprises determining whether a desired level of defrosting has been reached.

5. A computer system according to any of claim 1 - 4, wherein controlling the length of the defrosting event (90) comprises adapting the length to be either shorten or lengthen.

6. A computer system according to any of claim 1 - 5, wherein the evaluation further comprises determining whether a desired level of defrosting has been reached, andwherein upon determining that a desired level of defrosting has not been reached the processing circuitry (31) is configured to lengthen the length of the defrosting event.

7. A computer system according to any of claim 1 - 6, wherein the evaluation further comprises determining whether a desired level of defrosting has been reached, wherein upon determining that a desired level of defrosting has been reached in the current defrosting event (90), the processing circuitry (31) is configured to shorten the length of the defrosting event.

8. A computer system according to claim 7, wherein the evaluation further is based on statistical and / or historical data of previous defrosting events (90), and wherein upon determining that a desired level of defrosting has been reached in the current defrosting event (90), the processing circuitry (31) is further configured to determine if desired level of defrosting has been reached in a predetermined number of defrosting events (90), in a sequence of previous defrosting events (90), and if so, the processing circuitry (31) is configured to shorten the length of the defrosting event.

9. A computer system according to claim 7, wherein the evaluation further is based on statistical and / or historical data of previous defrosting events (90), and wherein upon determining that a desired level of defrosting has been reached in the current defrosting event (90), the processing circuitry (31) is further configured to determine if desired level of defrosting has been reached in a predetermined number of defrosting events (90), during a time period, and if so, the processing circuitry (31) is configured to shorten the length of the defrosting event.

10. An air handling system (1) comprising a computer system (30) according to any of claim 1-9.

11. The air handling system (1) of claim 10, further comprising a heat exchanger (10) comprising an exhaust air part (11) and a supply air part (12), wherein the heat exchanger (10) is configured to transfer heat from warm exhaust air (W), that flows intothe system (1) through the exhaust air part (11)), to cold supply air (C), that flows into the system (1) through the supply air part (12), a bypass (13), and a damper arrangement (20), configured to open and close the bypass (13) and the supply air part (12) on an upstream side the supply air part (12).

12. A computer-implemented method, comprising: receiving (102) upstream pressure data (51) of an exhaust air part (11) of the air handling system (1) after the defrosting event (90); receiving (104) downstream pressure data (52) of the exhaust air part (11) after the defrosting event (90); determining (106) a pressure drop (50) of the exhaust air part (11) based on the upstream pressure data (51) and the downstream pressure data (52) after the defrosting event (90); evaluating (108) the defrosting event (90) at least based on the determined pressure drop (50); controlling (110) the length of the defrosting event (90) based on said evaluation.

13. A computer program product comprising program code for performing, when executed by the processing circuitry, the method of claim 12.

14. A non-transitory computer-readable storage medium comprising instructions, which when executed by the processing circuitry, cause the processing circuitry to perform the method of claim 12.

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