A method for operating a cooling system

Abstract

A cooling system comprising cooling apparatus and a volume to be cooled by the apparatus The cooling apparatus comprises a compressor, a condenser unit, an expansion valve and an evaporator unit. A central processing unit is provided. The system further comprises a first temperature sensor and a second temperature sensor, with the first temperature sensor and the second temperature sensor being arranged to determine the superheat in the evaporator unit. The central processing unit receives information regarding the superheat in the evaporator unit and controls the compressor according to the received information.

Description

[0001] A Cooling System

[0002] Field of the Invention

[0003] This invention relates to a cooling system, and, more particularly to a refrigeration system.

[0004] Background to the Invention

[0005] Cooling systems, including cold rooms, freezers, and refrigerators, are essential in various industries and households. These systems often consume significant amounts of energy, oftentimes accounting for up to 60% of the energy demand in some installations.

[0006] Hitherto, cooling systems operate continuously to maintain a desired temperature, leading to high energy consumption and increased operational costs. Existing technologies often rely on general-purpose analogue-to-digital converters in onboard microprocessors for sensor data acquisition, which can lead to less accurate readings and inefficient system operation. Such systems typically employ return-air and space-air temperatures to control the operation of the cooling system; however, this approach does not provide a comprehensive picture of the thermodynamics within the system.

[0007] An example of this is shown in W02014030083 (Agile 8 Consulting Ltd), wherein the air-in temperature and the air-out temperature are monitored. In this system, the compressor is turned off for periods of time in order to improve efficiency. Whilst this system does reduce power consumption over more conventional systems, there are still aspects that are inefficient. For example, the monitoring of air temperatures can lead to suboptimal control of the compressor and fans, resulting in higher energy consumption and less efficient cooling performance. Some arrangements currently employ an air temperature sensor that stops a compressor when the temperature is at 2 degrees. The arrangement further uses a 2 degree differential, which means that when the temperature warms to 4 degrees, at which time the compress is restarted; however, due to the lag period between sensing the air temperature and then performing the starting or stopping of the compressor, there is a relatively large variation in the temperature in the volume being cooled. Subsequently, the temperature in the cooled volume can reach 5 degrees or may be cooled to 1 degree. Whilst in many situations this would not be a concern, in others it can be very important. Furthermore, energy is wasted in cooling the volume more than is actually required. During the operation of such a system, the expansion valve is kept open.

[0008] In view of the above, there remains a need for a more efficient cooling and refrigeration system that can reduce energy consumption without compromising the cooling performance.

[0009] Summary of the Invention

[0010] Accordingly, the present invention is directed to a method of operating a cooling system, the cooling system comprising cooling apparatus and a volume to be cooled, wherein: the cooling apparatus comprises: a compressor; a condenser unit; an expansion valve; and an evaporator unit; and a central processing unit or processing circuitry, wherein the system further comprises a first temperature sensor and a second temperature sensor; and wherein the first temperature sensor and the second temperature sensor are arranged to determine the superheat in the evaporator unit, with the central processor receiving information regarding the superheat in the evaporator unit and controlling the compressor and / or expansion valve according to the received information. The present invention provides a method of operating a cooling system that leverages precise sensor technology and advanced algorithms to improve operation and efficiency. Incorporating sensors that measure the temperature of coolant passing into and out of the evaporator, in addition to the space temperature, provides a more accurate understanding of the thermodynamics of the system. As such, operating the system with such improved data can lead to significant reductions in energy consumption and operational costs whilst improving cooling performance.

[0011] Thus, the present invention is able to control a cooling system by monitoring the superheat and associated change in temperature, or “delta-T”, of the coolant as it passes through the evaporator unit. This measurement of the relevant temperatures allows the central processing unit to be employed to determine when the evaporator unit is at maximum cooling capacity. Once the cooling capacity is determined, the central processing unit can control the compressor, preferably disabling it for a period, to make the system more efficient. The refrigerant potential in the evaporator is determined and the compressor can be operated accordingly, maintaining the temperature within a set range, whilst using less energy. A particular advantage of the present invention is that the timing of the shutdown of the compressor is based upon the evaporator superheat reaching an optimal plateau, then using the energy in the evaporator to remove the heat, then, prior to the refrigerant being fully used in the evaporator, the compressor is restarted, and the evaporator is refilled with refrigerant. As a result, the system can allow the refrigerant in the evaporator to be fully utilized, thereby improving its efficiency. The system can use an air sensor to monitor the volume to be cooled, and the system can be started using such a sensor, with subsequent operation employing the determination of the superheat. This allows the coolant to be used more effectively to maintain the temperature of the cooled volume whilst reducing energy consumption by deactivating the compressor.

[0012] Unlike some known systems, which stop the compressor based on the space or air outlet from the evaporator reaching a set temperature point, this present invention controls the compressor based on the cooling capacity of the evaporator, thereby reducing the lag period between the air temperature being detected and the cooling system operating that is common in existing systems. This can be determined by monitoring the superheat in the evaporator, which is to say, the temperature difference between the evaporator inlet and outlet coolant temperatures, or by using either the coolant inlet temperature or the coolant outlet temperature individually. The device can restrict the flow of further coolant to the evaporator unit, through restriction of the expansion valve or by reducing, or stopping, the compressor. Thus, when the evaporator reaches its maximum cooling capacity, the flow of further coolant can be throttled, reduced or stopped. Thus, the system of the present invention can provide important information regarding the cooling capacity, or cooling potential, of the coolant in the evaporator, and by sensing the coolant in and coolant out temperatures of the evaporator the present invention can improve the efficiency of the cooling process. In one arrangement, the compressor can be switched off using the superheat calculation and to allow the system to cool down to a specific set point, rather than running the compressor right down to a specific set point. Thus, using the superheat calculation, the compressor can be shut off, and the system continues to cool the volume.

[0013] Preferably, a digital potentiometer is provided, with an air temperature sensor signal of the refrigeration system passing through the digital potentiometer to the central processing unit. The central processing unit can adjust the resistance in the potentiometer to operate the cooling system. In one arrangement the digital potentiometer used to make the system think that the temperature is 2 degrees hotter or colder than the measured value, which allows the system to turn on, or off, in a more efficient manner, although it will be understood that this set point is adjustable. The control on the digital potentiometer may be aligned to above or below a set point, depending upon the system. For example, the control on the digital potentiometer may be programmed to be 0.5°C above or below a set point, or 4°C above or below the set point, depending upon the system; however, the volume being heated or cooled will maintain a set point to which it is programmed.

[0014] By adjusting the system by two degrees, the compressor can be run in a more efficient manner by triggering it to turn on, or off. The actual temperature is still monitored as a failsafe; however, the system can be used to predict when there is sufficient coolant in the system to maintain the desired temperature. Thus, the method of the present invention can provide improved, or optimized, refrigeration energy consumption. This may be achieved through the steps of: monitoring thermistor voltages using unity-gain buffers, which may be greater than 100MQ impedance; analyzing the delta-T, or superheat, patterns using algorithms; determining optimization zones through statistical analysis; injecting variable resistance via digital potentiometer and relay; and implementing predictive compressor control. This allows the compressor to be disengaged, or turned off, at appropriate times to allow the refrigerant to be used whilst maintaining the temperature within a set range.

[0015] Advantageously, the control system comprises a dual-channel digital potentiometer, a solid-state relay and / or a failsafe mechanism, which may include a timer. Further failsafe mechanisms may be provided, including temperature limit protection, power failure defaults to bypass the control system and a manual override capability.

[0016] A combination of monitoring the superheat in the system and having a digital potentiometer connected in series with an air temperature thermistor can allow the compressor to be operated in a more efficient and effective manner, thereby reducing the energy requirements for the cooling system.

[0017] Artificial intelligence modelling can be used to analyse the thermodynamic data in order to predict when the cooling system has sufficient cooling capacity, or potential, to reduce the compressor speed, or stop the compressor, whilst maintaining the temperature in the space within an acceptable range. The compressor may be controlled by a relay to control the compressor power supply in a binary manner, on or off, or a control can be used to provide more flexibility in controlling the speed of the compressor and the degree to which the expansion valve is opened.

[0018] The system can be adapted, through monitoring of data and, preferably, using artificial intelligence, to calculate the timing required to turn off the compressor whilst leaving sufficient refrigerant to continue cooling to the desired temperature. For example, the system can be set to aim for a consistent temperature of 2 degrees, and, monitoring the historic temperature data, the compressor can be stopped when the temperature in the volume being cooled reaches 2.5 degrees, because the refrigerant in the system continues to be used to take the volume to 2 degrees. In this system, the refrigerant continues to draw heat from the volume being cooled after the compressor is turned off, thereby, reducing the time for which the compressor is operating.

[0019] Preferably, the first fluid temperature sensor is arranged to monitor the temperature of the fluid at the evaporator inlet, and the second fluid temperature sensor is arranged to monitor the temperature of the fluid evaporator outlet, so that the superheat is determined from the two sensed temperatures. The first temperature sensor and the second temperature sensor are, preferably, positioned on the evaporator conduits, the first temperature sensor arranged between the expansion valve and the evaporator unit (coolant inlet), and the second temperature sensor arranged on the evaporator outlet (coolant outlet). These temperature sensors measure the coolant inlet and outlet temperatures, which can then be used to calculate the superheat, which is to say, the temperature difference across the evaporator. The superheat measurement, or either the coolant inlet or outlet temperature individually, can indicate when the evaporator has reached its maximum cooling capacity. When the maximum cooling capacity is reached, the compressor can be stopped based on this measurement, rather than waiting for the surrounding air to reach a specific set temperature point, which improves energy efficiency. Thus, the present invention monitors the superheat in the evaporator unit by measuring the temperature of the coolant entering the evaporator unit and measuring the temperature of the coolant exiting the evaporator unit. This provides a number of advantages over monitoring the temperature of the air entering the evaporator unit and the temperature of the air leaving the evaporator unit. For example, whilst the air temperature can be a useful reading in the system, there is a lag period between the evaporator unit cooling the air in the system, and the measurement of the temperature of the cooled air. Therefore, by the time that the air temperature has been measured, the potential of the coolant in the evaporator has already changed. This lag time in knowing the status of the coolant means that the compressor is operated for longer than needed. The present invention provides a way to address this problem with existing arrangements.

[0020] A liquid line temperature sensor may be provided. The liquid line temperature should be close to the ambient temperature, which is, preferably also monitored. Deviations from the anticipated temperature may indicate a problem with the condenser unit, for example, a blockage or a faulty fan. It is advantageous that the compressor can be slowed, but preferably stopped, in order to save energy. Whilst the compressor may be slowed in some arrangements, it can, additionally, be stopped. By knowing the cooling capacity in the evaporator, due to direct measurement of the coolant temperature, the compressor can be stopped earlier than by measuring the air temperatures. The coolant remaining in the evaporator can then be employed to continue the cooling process whilst the compressor remains off. By using the coolant fully, the risk of liquid returning to the condenser unit is reduced. Additionally, or alternatively, the system of the present invention can reduce the load on the compressor by adjusting the expansion valve to a lower, or its minimum, setting, thereby allowing the stored refrigerant in the evaporator to be fully utilized without stopping the compressor. In an inverter-driven compressor, a relay can be used to slow the compressor speed during this process.

[0021] Advantageously, the expansion valve is an electronic expansion valve that is controlled by the central processing unit, based upon information received regarding the measured superheat. As will be appreciated, an electronic expansion valve can be used to adjust the amount of coolant fed into the evaporator. In the present system, rather than stepping the electronic expansion valve, to throttle the fluid flow, the valve can be closed, because the amount of coolant in the system is sufficient to continue the cooling process without requiring further coolant to be provided. The evaporator is filled, and the compressor can be turned off and the expansion valve can be closed. Again, this reduces the energy requirements of the system.

[0022] The electronic expansion valves can be controlled through the implementation of an algorithm that can employ Pulse Width Modulation (PWM), or chunked duty cycle signalling. This control can be used to provide granular control over the flow of the refrigerant. An algorithm can adjust the percentage of coolant flow based on the thermodynamics of the system, thereby improving cooling efficiency and energy usage.

[0023] The algorithm can modulate the opening and closing of the electronic expansion valve, controlling the flow of refrigerant with high precision. By adjusting the duty cycle, the system can fine-tune the amount of refrigerant entering the evaporator, ensuring optimal superheat and improving overall efficiency. This granular control can be used to maintain the desired cooling performance while reducing energy consumption. The system can be used to continuously adjust the valve position based on real-time data from the sensors of the system, thus allowing for a dynamic response to changing conditions within the cooling system.

[0024] Preferably, a least one further sensor is provided to measure at least one of a group comprising: ambient temperature within the volume; a temperature of a product contained within the volume; the refrigerant liquid line; ambient temperature external of the volume being cooled; temperature in the space that is distal from the evaporator; door temperature; compressor temperature; and refrigerant suction pressure. By providing inputs from at least one further sensor, the system can be made more efficient. Furthermore, problems in the system can be detected by, for example, monitoring the space being cooled and / or a product within the cooled space. The incorporation of the temperature sensors at both the coolant in and coolant out points of the evaporator, in addition to the space temperature, provides information that can be used to determine the coolant potential in the evaporator unit. In turn, this can allow a more efficient operation of the system, ensuring that the coolant is used effectively, in turn leading to significant reductions in energy consumption and reduced wear and tear on parts. Ambient temperature may also be useful in determining the best operation of the compressor to ensure that the condenser is operating. It is envisaged that the arrangement may comprise four, six or eight sensor inputs, although it will be appreciated that more or fewer may be used.

[0025] A transducer may be used to measure the suction pressure in the system. The information from the transducer may be provided to the central processing unit, wherein it may be used in the control of the expansion valve. Adjustment of the expansion valve can assist with ensuring that the coolant is fully used in the evaporator.

[0026] In one embodiment, the system further comprises evaporator fans, wherein the fans are controlled by the central processing unit. The provision of evaporator fans can assist with the flow of air and improving the cooling process. The fans can be controlled by the central processing unit to adjust the air flow through the evaporator, thereby adjusting the cooling rate of the space being cooled. The evaporator fans can be controlled by the central processing unit, allow them to turn off at a predetermined period of time after the compressor is turned off, for example, 30 seconds after, although it will be understood that this timing can be adjusted as required. Additionally, a setting within the control of the system can allow, and preferably ensure, that the fans start before the compressor starts, ensuring uniform temperature distribution and preventing liquid refrigerant from returning to the compressor. These features increase the time it takes for the space to heat up to a compressor cut-in set temperature, thereby reducing the frequency of compressor restarts, which saves energy, and extends the lifespan of the compressor and other parts in the system.

[0027] The method of operating a cooling system herein senses when the superheat is above a predetermined superheat temperature, and so the compressor is stopped to conserve energy. The method determines the maximum cooling capacity of coolant in the evaporator, so that the compressor can be stopped with sufficient coolant in the evaporator to allow the system to continue to cool, without using excess energy. In the present invention, an air sensor in the space to be cooled can be used to start the compressor, and when the evaporator is full of refrigerant, the compressor can be turned off whilst the system uses that refrigerant. The time where the compressor is off may be either for a set period, such as 3 minutes, or once the refrigerant is used and a sensor detects that either the coolant is used or the volume starts to heat up, the system restarts the compressor.

[0028] It is advantageous that the compressor is restarted after a time delay and / or the superheat passing under the predetermined threshold. The compressor can be turned off for a predetermined period of time, or when the superheat of the coolant crosses a known threshold. By controlling the system in this way, energy is saved by having the compressor turned off whilst the coolant in the system is used to continue the cooling process. When the capacity of the coolant is reduced the compressor can be restarted to supply more coolant to the evaporator.

[0029] The system of the present invention may be used for in water cooling systems, refrigerators, particularly walk-in refrigerators, and heating and air conditioning systems. These systems may be particularly useful in the field of food and beverage storage, hospitality and supermarkets. Similarly, the arrangement may be employed in relation to transport refrigeration, for example, variable temperature vehicles, in data cooling centres and pharmaceutical cold storage.

[0030] The present system may provide energy savings of up to 45%, compared with existing stock controllers and systems.

[0031] A cooling system in accordance with the present invention may be provided with communications module, either wired or wireless. Such a module can allow local or remote monitoring and control or adjustment of the system. For example, the system may provide information to a software application, an Internet-based interface and building management systems. It will be appreciated that the arrangement can allow for alerts and / or alarms to be set that will alert a user to any concerns.

[0032] Relays can be provided in the system, particular on the important components, such as the compressor unit, evaporator unit, expansion valve and fans. This may assist with more precise control of the system.

[0033] The central processing unit may be provided with diagnostic systems, thereby allowing it to monitor and diagnose any problems in the refrigeration system. Thus, if one of the sensors detects a parameter that is outside a set range, an alert can be generated.

[0034] Similarly, the system can be constantly monitored to detect improvements, which, when coupled with artificial intelligence, can increase the efficiency further.

[0035] Unlike traditional systems that use fixed set point algorithms, the present invention reduced energy consumption by providing non-invasive monitoring, adaptive learning and fail-safe control mechanisms.

[0036] Thus, the present invention extends to a control module for controlling a cooling system, in which the control module is provided with circuity and is adapted to control the system, as described herein. The system of the present invention monitors and records operational parameters to establish patterns that are specific to the system. These patterns and parameters can then be used as part of a machine learning, or artificial intelligence system, to provide an improved control system for a specific installation. As all systems operate in different ways, due to various reasons such as the ambient temperature and the efficiency of the seals and the cooling system, where the system can learn the idiosyncrasies of the system, a cooling plan can be created for that specific arrangement, because upon using the superheat in the system.

[0037] The learning algorithm can begin to improve, or optimize, the system within two full cooling cycles. During these cycles, and subsequent cycles, the system can collect operating temperatures, including the maximum and minimum operating temperatures, compressor duty cycles, temperature change rates within the volume to be cooled and the superheat (delta-T) measurements. Using that information, potentially with further monitored parameters, the system can undertake statistical analysis to determine temperature setpoints, cycle duration patterns, temperature decay rates and the operational temperatures. The upper operating limit, which may be the detected set point minus the standard deviation, which is to say, the upper zone boundary is the setpoint adjusted downward by the measured temperature variation. Similarly, the lower zone boundary limit may be taken as the observed minimum temperature plus a safety margin of two or three degrees. Subsequently, the system can be better understood by the control system so that cooling rates, cycle patterns and recovery times can be determined more accurately. This allows the system to learn an efficient way to run the system. After the initial learning stages, the system can continue to monitor changes in parameters and so can adapt accordingly. For example, the system may observe load changes and events such as door openings and the frequency thereof during the day, and the system can be run more effectively to compensate for periods where more demand is required. Thus, the dynamic modelling continues during operation so that adaptive algorithms can be employed to adapt the refrigeration system to work with operational situations whilst also keeping the cooled volume within a desirable range. As such, the system provides a predictive model of the cooling demand and adjusts the superheat and compressor operation accordingly, with the compressor being turned off for periods where it can, thereby saving energy. Non-invasive monitoring can be achieved by monitoring exiting thermistor circuits using high-impedance unity gain buffers, which does not interfere with the existing circuit. This allows the system to be monitored without affecting the existing thermistor. The system can derive temperature readings from existing thermistor voltage dividers, thereby reducing or eliminating the need for physical sensor installation.

[0038] In one arrangement a digital potentiometer-based resistance injection with relay isolation for temperature offset control can be used.

[0039] Brief Description of the Drawing

[0040] An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawing, which shows a system in accordance with the present invention.

[0041] Detailed Description of Exemplary Embodiments

[0042] Figure 1 shows a cooling system 10. The cooling system 10 comprises an internal unit 12 and an external unit 14, with conduits connecting the two. The internal unit 12 is positioned within the space to be cooled, and the external unit is arranged outside the space to be cooled. It will be appreciated that these units 12 / 14 will be spaced apart and that they are shown close together in the figure for ease of understanding.

[0043] The internal unit 12 is arranged to cool a space, or volume, in which it is arranged. To that end, the internal unit comprises an electronic expansion valve 16 that is connected via a fluid conduit 18 to an evaporator coil 20. The evaporator coil 18 is then connected via a fluid conduit 22 to a compressor 24, with the compressor 24 being arranged in the external unit. The compressor 24 can pass fluid via a fluid conduit 26 to a condenser coil 28. The condenser coil 28 then feeds fluid to the electronic expansion valve 16 through a conduit 30. An evaporator fan 32 is provided in the internal unit 12, with the evaporator fan 32 being arranged to drive air over the evaporator coil 20. Similarly, in the external unit 14, a condenser fan 34 is arranged to driver ambient air over the condenser coil 28. The arrows in the accompanying figure show airflow through the internal unit 12 and the external unit 14.

[0044] Various sensors are provided throughout the system. Importantly, a fluid-in sensor 40 is provided to monitor the fluid passing from the electronic expansion valve 16 to the evaporator coil 20. This fluid-in sensor is, preferably, arrange in the conduit 18 and can be used to monitor the temperature of the fluid therein. A fluid-out sensor 42 is arranged in the conduit 22 between the evaporator coil 20 and the compressor 24. It will be appreciated that the fluid-out sensor 42 will be positioned close to the fluid exit of the evaporator coil 20 in order to monitor the temperature of the fluid leaving the evaporator coil 20.

[0045] A first space sensor 44 is positioned in the space that is being cooled. This first space sensor 44 is arranged to monitor the temperature within the space, and it may, optionally also monitor humidity and other parameters, in order to ensure that the cooling process is operating correctly and that the climate is within intended ranges. Similarly, a product temperature sensor 46 may be placed within the space to be cooled, so that the temperature of a product within the space is also monitored. The product temperature sensor 46 may be placed within glycol-filled container to imitate a product within the cooled space. A second space sensor 48 is provided within the space being cooled, the second space sensor 48 being arranged in a position distal from the first space sensor 44. Having two space sensors 44 / 48 allows the monitoring of the temperature and, optionally other parameters, within the space to detect any anomalies, for example a failure of fans within the space to distribute the cooled air more evenly.

[0046] A liquid line sensor 50 is arranged in the conduit 30, with the liquid line sensor 30 monitoring the temperature of the liquid within the conduit 30.

[0047] Additionally, a compressor sensor 52 is arranged on the compressor 24 to monitor the temperature and performance of the compressor 24. An ambient air sensor 54 may also be provided to monitor the ambident temperature around the external unit 14. The room or area in which the system is operating can be monitored to ensure that the condenser 28 is efficiently ventilated. Monitoring the ambient temperature can also ensure that they system is working effectively and does not overheat.

[0048] A door sensor (not shown) can be provided to monitor when a door to the space has been opened, and, potentially, not properly closed.

[0049] The fluid conduit 30 is provided with a solenoid valve 56. When the solenoid valve 56 is closed, the flow of coolant is halted.

[0050] A central processing unit 60, and associated processing circuity, is connected to the active parts of the system 10, and the sensors in the system 10 feed into the central processing unit.

[0051] Whilst the system 10 is running, the central processing unit 60 constantly monitors the information from the sensors. In particular, the fluid-in sensor 40 and the fluid out sensor 42, which are arranged to monitor the temperature of the fluid entering and leaving the evaporator unit 20. From the readings supplied from these sensors 40 / 42, the superheat across the evaporator unit 20 is calculated. Knowing the coolant and its properties, the central processing unit 60 can calculate when the evaporator unit 20 reaches its maximum cooling capacity, which is to say, the evaporator unit 20 is essentially full, or close to full, of coolant. At this time, the central processing unit 60 can reduce the flow of coolant to the into the evaporator unit 20. This reduction in fluid flow can be undertaken by slowing or stopping the compressor 24, reducing the flow of fluid through the electronic expansion valve 16 and / or closing the solenoid valve 56. The space continues to be cooled by the coolant that is already in the evaporator 20. This allows the coolant to be fully utilized before more coolant is supplied. In the meantime, a reduction in the compressor 24 speed reduces the power consumption and wear on the parts of the compressor 24. During operation, the central processing unit 60, which can include an artificial intelligence module, continuously analyses data from the sensors and transducers, including suction pressure, to adjust the pulse wave modulation settings of the electronic expansion valve 16. This constant monitoring and adjustment allows the electronic expansion valve 16 to modulate precisely in response to changing conditions, thereby improving energy efficiency and cooling performance. The use of a relay for pulse wave modulation control of the electronic expansion valve 16 enables finer control over refrigerant flow compared with existing systems.

[0052] The system 10 can stop the compressor 24 when the temperature in the space drops below a predetermined temperature, and when an upper threshold in the superheat is reached, both of which can be set by a user. In some arrangements, the compressor must have run for at least a predetermined period of time, for example, three minutes before it can be turned off again.

[0053] Once the space temperature rises above a set temperature, and when a lower threshold for the superheat is reached, the compressor 24 is restarted. The compressor should be stopped for a predetermined period of time, for example, three minutes, before being restarted. The delay can assist with avoiding short cycling and maintaining efficient cooling conditions within the space.

[0054] As a comparison between existing systems and the present invention, a system such as that described in W02014030083 will have a 2°C setpoint. This means that the system will aim to keep a temperature between 2°C and 4°C. Thus, the temperature of the air outlet of the evaporator is monitored, and when it reaches 2°C, the compressor is stopped; however, the coolant in the system may continue to cool the air to lower than 2°C. This may be problematic for spaces where the temperature should not be lower than °C. When the outlet air temperature is detected to be 4°C, the compressor is restarted; however, there will be a lag period between the compressor restarting and the coolant starting to cool the outlet air again, thereby risking the system going above 4°C. Whilst the set points could be adjusted, this can lead to undesirable fluctuations in temperature. The present system can stop the compressor when the refrigerant potential is determined to keep cooling the system to 2°C. Thus, the system of the present invention can, for example, turn off the compressor at 2.5°C, because the evaporator unit will continue to cool the system down to 2°C without the compressor operating. This means that the system can turn off the compressor 0.5°C sooner than the prior art arrangement. This improves efficiency in the system, and reduces wear and tear on the parts. The result is that the arrangement uses less energy and can last for longer without parts needing replacement. A more accurate temperature control can be achieved.

[0055] In one arrangement, unity gain buffers connect to existing thermistor leads and a digital potentiometer is connected in series thereto. A learning phase is undertaken in which two full cooling cycles ae completed, which allows initial characterisation of the system. A predictive control model is then created based upon the learned cycle, and using the central processing unit, the model being stored in non-volatile memory. As the system is then run, the system is constantly monitored to learn further patterns, and the model is adapted to changes and patterns. At the same time, continuous boundary checking is undertaken, with automatic engagement or disengagement to ensure that predetermined temperature thresholds are not exceeded.

[0056] The system of the present invention can employ algorithmic decision logic. In this way, there arrangement can monitor the temperature of the thermistor, and when temperature approaches 80% of optimization temperature zone width, the system can prepare a resistance injection. When the thermal inertia calculation indicates sufficient cooling capacity within the evaporator, the system initiates a shutdown process for the compressor.

[0057] The system can be used to monitor the temperature trend and rate of change within the volume to be cooled. Subsequently, the system can calculate the remaining thermal capacity in the refrigeration system, based on historical decay patterns and, preferably, taking into account monitored events. As such, an optimal resistance value can be determined between 0 and lOOkQ, advantageously in 256 steps, in order to obtain a target offset. The relay can be engaged and the calculated resistance applied. The system can then monitor the response and adjust the resistance or disengage, as needed in order to obtain the desired cooling level.

[0058] When the compressor is disengaged, a dynamic resistance control may be used, in which the control system continuously calculates the exact resistance required to maintain a target temperature offset, which may be 2°C below actual detected temperature. The control system can then dynamically adjust the digital potentiometer setting to hold this precise offset, increasing the resistance if the offset decreases in order to avoid compressor re-engagement, and reducing resistance if the offset increases, thereby preventing temperature alarms. This closed-loop control maintains the equipment’s perceived temperature at a specific target point throughout the optimization cycle, ensuring the system operates within safe bounds without triggering protective functions.

[0059] In one arrangement, when a learning confidence score is calculated, which is based upon the accuracy of the model compared with the measured parameters. Where the learning confidence score is less than 70%, the system can be allowed to continue without intervention to that the system can obtain more information, and the model can be adapted to more accurately reflect the measured values.

[0060] Where a digital potentiometer is used, the device may be chosen to be a dual channel potentiometer that has a range of approximately lOOk in 256 steps. The digital potentiometer may have a wiper resistance, or inherent resistance, of approximately 52Q, but, preferably, less than 125Q.

[0061] The present invention can provide an energy-efficiency control arrangement that can be used to reduce compressor runtime in refrigeration systems. This can be achieved by detecting the point of peak evaporator efficiency using superheat measurements, the temperature of the volume being cooled and, in some arrangements, the temperature of a product that is being cooled. The system can operate by cutting power to the compressor and / or a solenoid or electronic expansion valve, which may be at a time before the same event would occur normally, or where the speed of the compressor would be reduced, rather than the compressor being disengaged. A resulting benefit is that the system of the present invention uses the latent energy in the evaporator to maintain the space temperature, thereby reducing the operating time of the compressor and saving energy.

[0062] The present invention is, preferably, able to be retrofitted or can be non-integrated installed. The arrangement does not seek to maintain superheat or liquid line temperature or pressure operation, but rather to intelligently stop the compressor when the set parameters are met.

[0063] It will be understood where figures are used herein, for example, 2 degrees Celsius, this is given as an example only and other temperatures may be used, for example, 3°C or 4°C or, when used in an air conditioning system, 18°C or 20°C.

[0064] Features of one or more embodiment described herein may be incorporated into a different embodiment and non-essential features may be omitted. For example, in one arrangement, sensors that are not essential, for example, the second space sensor or the product temperature sensor, may not be present in the system.

Claims

Claims1. A method of operating a cooling system, the cooling system comprising cooling apparatus and a volume to be cooled, wherein: the cooling apparatus includes: a compressor; a condenser unit; an expansion valve; and an evaporator unit; and a central processing unit (processing circuitry), wherein the system further comprises a first temperature sensor and a second temperature sensor; wherein the first temperature sensor and the second temperature sensor are arranged to determine the superheat in the evaporator unit, with the central processing unit receiving information regarding the superheat in the evaporator unit and controlling the compressor and / or expansion valve according to the received information; and wherein, the superheat in the evaporator is monitored, and when the sensed superheat is above a predetermined superheat temperature, the compressor is stopped.

2. A method according to claim 1, wherein: the first fluid temperature sensor is arranged to monitor the temperature of the fluid at the evaporator inlet; and the second fluid temperature sensor is arranged to monitor the temperature of the fluid evaporator outlet; and wherein the superheat is determined from the two sensed temperatures.

3. A method according to any preceding claim, wherein the expansion valve is an electronic expansion valve that is controlled by the central processing unit, based upon information received regarding the measured superheat.

4. A method according to any preceding claim, wherein, a least one further sensor is provided to measure at least one of a group comprising: ambient temperature within the volume; a temperature of a product contained within the volume; the refrigerant liquid line; ambient temperature external of the volume being cooled; and refrigerant suction pressure.

5. A cooling system according to any preceding claim, wherein, the system further comprises evaporator fans, wherein the fans are controlled by the central processing unit.

6. A method of operating a cooling system according to claim 1, wherein the compressor is restarted after a time delay and / or the superheat passing under the predetermined threshold.

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