GB2534664A - Food temperature simulation - Google Patents

Abstract

A method 500 of deriving a set of predefined values simulating food temperature for each of at least two foodstuffs is provided. Each foodstuff is selected and placed in an environment, a temperature within the environment being controllable 510. Initial temperatures inside and outside the foodstuff are measured 520. A step change in the temperature of the environment is applied 530. The resulting changes over time of the temperature inside and outside the foodstuff are measured 540. A functional and temporal relationship between the temperatures inside and outside the foodstuff is derived and stored 550. The temperature within a foodstuff at a time point can be estimated by retrieving a stored set of predefined values and applying the relationship for the foodstuff to a temperature measured outside the foodstuff over a time period.

Description

Food temperature simulation

Field of the Invention

The invention concerns a food temperature simulation, enabling energy saving for a refrigeration system for cooling food in a refrigerated enclosure.

Background

Food refrigeration systems are designed to keep food cooler than the prevailing temperature at the location where the refrigeration system is situated. Common food refrigeration systems have the following components: (i) A refrigerated enclosure; (H) A compressor, providing cooling fluid for cooling food in the refrigerated enclosure; (Hi) A motor for driving the compressor; and (iv) A motor controller, for cycling the motor on and off as required.

The motor controller may comprise electronic microprocessor control circuitry. The control circuitry may typically respond to a temperature measurement. The temperature 20 measurement is provided by a temperature sensor located within the enclosure, and the measurement value depends on the air temperature within the enclosure.

Compressor motors have high current demands. In many food refrigeration systems, some of the waste heat from the motor of the compressor tends to heat up the cooled enclosure. This heat itself then also has to be removed by further operation of the compressor. The resulting systems are expensive to run, and may suffer high levels of compressor wear.

The temperature of the air in the refrigerated enclosure may be a highly inaccurate measure of the temperature within food items inside the refrigerated enclosure. For example, access to the refrigerated enclosure is typically achieved simply by opening a door to the enclosure. However, the cooled air in the enclosure may be lost whilst the door is opened, even if the door is then closed within substantially less than a minute. Air that enters the enclosure whilst the door is open is likely to be at the prevailing temperature at the location where the refrigeration system is situated. If the refrigeration system is in a kitchen, for example, then the air entering the refrigerated enclosure may be tens of degrees warmer than the temperature of the air in the enclosure, prior to opening the door.

As a consequence of the entry into the refrigerated enclosure of this warmer air, the temperature sensor located within the enclosure may provide a measurement showing that the air temperature within the enclosure has risen beyond an acceptable limit. This will then cause the compressor to start. However, in reality, the thermal inertia of food in the refrigerated enclosure and the thermal mass of the enclosure's walls would mean that the actual temperature of the food is affected almost imperceptibly by the entry of this warmer air. Without operation of the compressor, the air within the refrigerated enclosure would quickly have returned to a temperature only very slightly above that of the air in the enclosure prior to the door being opened. Prior art systems have, therefore, sought ways to avoid the compressor being activated when the only temperature change that occurs is a temporary rise in the temperature of the air within the refrigerated enclosure.

The underlying approach of known arrangements is therefore an attempt to provide a temperature controlled environment. The main aim is to keep stored 'products' at a predetermined target temperature, without being overly reactive to changes in transient air temperatures. The products may be food, chemicals or equipment. However in the case of refrigeration and freezer cabinets, what determines when the thermostat energizes the compressor is too often still at least partially the 'air' temperature, as opposed to the temperature of the stored products. Warm air entering a cabinet will actually contain very little energy relative to the mass of the latent cooling inside the chilled environment. However this rapid change of air temperature is often all that is required to cause the compressor to start another cycle, often needlessly.

Known approaches have included providing a temperature sensor within the refrigerated enclosure, the temperature sensor being surrounded by a body that has much greater density than air. The body's mass then provides thermal inertia. The temperature sensor's temperature will not rise to the temperature of warmer air introduced temporarily into the enclosure. An example of a body used to surround a temperature sensor is a copper tube that has been filled with oil and sealed at each end. Another example is a wax-based food simulant. These arrangements can lead to a compressor cycling on less frequently, without any risk to the condition of the food items in the refrigerated enclosure.

An example of a known system is shown by CA-A-2696059. The thermal sensor of CA-A-2696059 is located within in a body of cheesewax. The cheesewax prevents the temperature of the temperature sensor rising significantly, when a cooled unit in which the sensor is located is opened. Another arrangement is known from GB-A-2465019. In GB '019, an attempt is made to improve the composition of the body that surrounds the temperature sensor. The body surrounding a temperature sensor in GB '019 is made of a solid wax in which are distributed gas-filled polymeric particles. DE-A-3032864 shows another example of a food simulant.

The inventors have recognized and addressed shortcomings of prior art approaches, such as those illustrated by the thermal sensor of CA-A-2696059 and the alternative arrangement known from GB-A-2465019. If a typical refrigeration air temperature sensor of the prior art is covered with an increased mass like a copper tube filled with oil and sealed at each end, or a wax based food simulant, then the compressor will cycle less often with the potential of little or no adverse reaction to the stored 'food'. The inventors have recognized limitations of these prior art approaches that include use of only a standard material compound, such as a 'lump of wax'. In prior art systems, there is no possibility to vary the performance of the lump of wax. The inventors have foreseen the use of a 're-programmable' system, with options for various stored products in different types of refrigerated cabinets, such as drinks cabinets, dairy produce cabinets or frozen foods cabinets having different thermal mass. Many stored products, such as types of food with totally different thermal characteristics, can be better approximated with the present invention. The inventors have also realized that prior art systems did not offer the possibility of directly switching the compressor, and bypassing the analogue thermostat. For this further reason, the efficiency of prior art systems is severely restricted by the limitations of the 'host' incumbent thermostat, i.e. the installed thermostat. With prior art systems, calibration could prove very difficult, and it was not easy to verify equipment performance.

The inventors have recognized further shortcomings of known systems. The operation of hermetically sealed ac induction motor driven compressors is governed by specific laws of thermodynamics. For example, in order to remove heat energy from a designated space, a proportional amount of energy has to be expended to move the heat', heat being energy in motion. This applies to a refrigerator, freezer cabinet or air-conditioned room. However, the expended energy in known systems is a problem, since it leads to that energy itself needing to be removed from the space. Heat is extracted from the air through a heat transfer (diabatic) process. However, energy cannot be created or destroyed. So any excess current that is absorbed by the motor within the process will be converted to another form. The excess current is any energy or current over and above the absolute minimum that would be required to do the job of work in a perfectly efficient system. After being converted to heat, the excess current will in effect be reintroduced back into the system in the form of counterproductive additional 'heat'. The more the compressor runs and draws excess current, the more heat is introduced back into the system, creating a further isentropic effect. In a hermetically sealed compressor, any heat goes into the refrigerant coolant first, before it is dissipated into the ambient air in the designated space.

Summary of the Invention

In accordance with a first aspect of the invention, a method of deriving a set of predefined values simulating food temperature is provided, having the steps of appended claim 1. Further preferred steps and features are provided, as detailed in dependent claims 2-4. Using the set of predefined values, a method of estimating the temperature within a foodstuff at a time point is provided.

The invention provides the ability to digitally mimic the diabatic rate of various foods and products, and select these at site level. The invention will achieve savings from both accurate food temperature sensing and optimization of a compressor motor. In addition, due to the synergistic relationship of these two features, observation has shown that the energy saving produced by optimization of the compressor will be increased in percentage terms, as a result of the way in which the invention changes compressor cycles.

Some or all of the following advantages may result from the apparatus and methods of the invention: (i) Compressor start-ups are reduced, by ensuring that the compressor is only energized when a real demand is detected via the food mimicking digital thermostat.

(ii) Compressor life can be extended, and the maintenance costs reduced. This is 10 achieved by reducing both the frequency of start-ups, and the amount of wasted heat from the compressor that needs to be removed.

Monitoring and recording of 'food' temperature may be carried out remotely via the world-wide web. Reports can then be provided, via Enigin's 'Eniscope' (RTM) system.

Brief Description of the Drawings

Figure 1 illustrates a schematic perspective view of part of a refrigeration system.

Figure 2 illustrates an example of a sensor arrangement for simulating food temperature.

Figure 3 illustrates an embodiment of a force-cooled food refrigeration system.

Figure 4 shows an embodiment of a control arrangement for the refrigeration system.

Figure 5 illustrates a method of deriving a set of predefined values simulating food temperature in accordance with the invention.

Figure 6 illustrates three possible measurements derived in accordance with the method of figure 5.

Figure 7 illustrates a complete refrigeration system.

Figure 8 provides a comparative example of graphs that show the recorded motor load profiles for a compressor operating without the invention, and a compressor run using the arrangement of the invention.

Figure 9 provides another example of graphs that show the recorded motor load profiles for a compressor operating without the invention, and a compressor run using the arrangement of the invention.

Figure 10 illustrates a further embodiment of a force-cooled food refrigeration system.

Detailed Description

The inventors have realized that prior art systems show several limitations. They use a standard material for the body that surrounds the temperature sensor as the sole indicator of food temperature. As a consequence, they can only provide vague temperature estimates for differing types of foodstuff in a designated enclosed space. They may also be limited to a particular size of food item in the enclosed space, and to the items of foodstuff being either wrapped or unwrapped. In addition, the efficiency of prior art systems is limited to the performance provided by an analogue thermostat, which switches the compressor on and off. Calibration can prove very difficult, and it is not easy to verify equipment performance.

The present invention provides an energy efficiency methodology for optimizing, constantly monitoring and improving the performance of compressors utilized operationally to provide force-cooled refrigeration.

The invention incorporates a combination of electronic microprocessor control circuitry with software algorithms designed to deliver improved energy efficiency and control. An Eniscope Real-time Energy Management System may also provide intelligent feedback on system performance. Variables monitored may include compressor run-time, frequency of cycles and overall energy demand.

The invention may significantly reduce the current absorbed by a compressor motor. This will lead to: (i) Improved performance; (H) Extended equipment lifetimes; and (iii) Reduced energy consumption.

The force-cooled food refrigeration system comprises a compressor for supplying cooling fluid, which cools food in an enclosure of the refrigeration system. A module for simulating food temperature is located in the enclosure. The module comprises a food simulant body in contact with a first temperature sensor, the first temperature sensor within the module being configured to provide a first signal indicative of food temperature within the enclosure.

The force-cooled food refrigeration system also comprises a second temperature sensor. The second temperature sensor is configured to provide a second signal that is a measure of the profile of the rise and fall of ambient temperature within the enclosure.

A storage module stores at least two sets of predefined values. A first set of predefined values digitally simulates the temperatures that a first foodstuff attains within the enclosure under a first range of operating conditions of the refrigeration system. A second set of predefined values digitally simulates the temperatures that a second foodstuff attains within the enclosure under a second range of operating conditions of the refrigeration system. The operating conditions stored as part of each set of predefined values may comprise measurements of temperatures attained in a food simulant, and air temperature measurements for air in a refrigerated enclosure, under test conditions.

A control system comprises a motor control subsystem for controlling the operation of the motor of the compressor. A logic module of the control system is configured to drive the motor control subsystem to activate or deactivate the motor on the basis of: the signal indicative of food temperature; the second signal; and one of the first or second sets of predefined values, the set of predefined values being selected to match or approximate the temperatures that a foodstuff currently in the enclosure will attain. The motor control subsystem is configured to regulate the voltage applied to the motor when the compressor is operating and a load on the compressor varies, whereby in operation the voltage applied to the motor is regulated to be the minimum value that provides synchronous rotation of the motor. The voltage applied to the compressor just matches an instantaneous load on the compressor. This operating condition improves the power factor and efficiency of the motor, during its lightly loaded phase of each duty cycle.

The force-cooled food refrigeration system may further comprise a third temperature sensor providing a third signal, the third signal being a measure of an operating temperature of a motor of the compressor. A metering subsystem may then capture data comprising a record of at least the third signal and times when the compressor is active, and export the data to a monitoring unit for verification of equipment use and/or energy use.

The refrigeration system may be applied in a wide variety of settings. These may include commercial refrigerated cabinets, such as those found in supermarkets, convenience stores, freezer centres, public houses, restaurants, hotels and garage forecourts. High specification domestic refrigerators may also benefit from the invention.

Various aspects of the refrigeration system solve the specific disadvantages that the inventors have identified with prior art systems. A series of software options can be formulated from measuring and recording the thermal characteristics of differing products and foods in real-time. These measurements can be made in a real-life analogue environment. The measurements are then mimicked with sets of predefined values, which may be held as software algorithms. The predefined values can be selected for use in the refrigeration system in dependence on a particular foodstuff that is currently in the refrigerated enclosure of the refrigeration system. This selection may be by means of a remote control and display. The predefined values may mimick the temperature response of different sized quantities of a particular foodstuff, such as a 0.5 kg, 1 kg or 2kg block. The refrigeration system may hold predefined values for many different foodstuffs. Alternatively or in addition, the predefined values may be representative of certain classes or states of food, e.g. solid, powder, liquid.

Figure 1 illustrates a schematic perspective view of part of a refrigeration system 100. A refrigerated enclosure 110 is shown with two shelves 112, 114.

Food stuff 120 is shown as a large block. Three smaller blocks of the food stuff are shown at 122, 124, 126. A module for simulating food temperature 130 is located in the refrigerated enclosure 110. Module 130 may be connected by wire to a logic module of the control system, or may be wirelessly linked to the logic module. In an alternative to the arrangement shown in figure 1, module 130 may be removably attached to the interior of the refrigerated enclosure 110, or one of shelves 112, 114.

Figure 2 illustrates an example of a sensor arrangement 200 for simulating food temperature.

A wall 210 is shown, which creates an enclosed volume 220. Within enclosed volume 220 are simulant 230 and a temperature sensor 240. Simulant 230 maybe based on a 'cheese wax' type material. Optional additional elements may modify the thermal characteristics of simulant 230, in order to better simulate a particular type or size of foodstuff. The rounded outer surface of enclosure 220 may facilitate easier cleaning of module 210.

Temperature sensor 240 is located within the simulant 230. Mechanical support and guidance when inserting temperature sensor 240 are provided by guidance mechanisms 250. Guidance mechanisms 250 project from the inner surface of wall 210. End stop 252 and restraint 254 may also help to ensure that the temperature sensor is held securely at the correct position against the wall of enclosure 220. An electrical cable 260 joins the temperature sensor 240 at interface 262.

Temperature sensor 240 constitutes the first temperature sensor of the invention. Temperature sensor 240 may be a therm istor. The output signal from temperature sensor 240 may be digitised, and recorded. In operation, the first temperature T1 is sensed by temperature sensor 240. The value of first temperature T1 sensed by temperature sensor 240 will depend on the thickness and material of simulant 230. Another factor is the thickness and material of wall 210.

Simulant 230 may fill all of the space within enclosed volume 220 that is not taken up by temperature sensor 240, guidance mechanisms 250, end stop 252 and restraint 254. Such an arrangement may further serve to support and protect temperature sensor 240.

An exemplary set of dimensions for sensor arrangement 200 are: length 100mm; diameter in one plane 50mm; diameter in perpendicular plane 30mm. However, a wide range of other physical sizes for sensor arrangement 200 are also foreseen.

Figure 3 illustrates a force-cooled food refrigeration system 300. A chilled space 310 is shown. Chilled space 310 may be equipped with internal structure, such as shelves 112, 114 shown in figure 1.

A compressor 320 supplies a coolant fluid via a 'hot gas' line 322 to a condenser 330.

See arrow A for the direction of supply of coolant fluid, after leaving compressor 320.

Electrical power to drive a motor 324 of the compressor is provided by power input 326.

The output of condenser 330 is a provided via 'liquid line' 332 to an expansion device 334. See arrow B. Expansion device 334 supplies an evaporator 340 located within chilled space 310. See arrow C. Evaporation of coolant fluid within evaporator 340 acts to reduce the temperature within chilled space 310. Fluid leaving the evaporator 340 returns via 'suction line' 342 to compressor 320. See arrow D. Foodstuff 350 may correspond, for example, to one or more of blocks 120, 122, 124 or 126 of figure 1. A second foodstuff 352 may be the same foodstuff as first foodstuff 350, or be different. Foodstuffs 350 and 352 may also be of different sizes.

Food simulant 360 is shown schematically, and may correspond to that shown in figure 2. A first temperature sensor 362 is located within the food simulant 360, and measures first temperature Ti. A second temperature sensor 370 is also located within the refrigerated enclosure 310, and measures second temperature T2 of the air inside refrigerated enclosure 310. Although generally indicated as ovals, the temperature sensors may, for example, be thermistors.

Third temperature sensor 328 measures the temperature of the motor 324. Fourth temperature sensor 380 measures the temperature of air outside refrigerated enclosure 310.

Temperatures are measured as follows: (i) First temperature T1 is the temperature of the food simulant material. First temperature T1 is measured by first temperature sensor 362, which may correspond to temperature sensor 240 in figure 2.

(H) Second temperature T2 is a measured temperature of the air inside refrigerated enclosure 310.

(iii) Third temperature T3 is a measured temperature of motor 324 of the compressor 320. This temperature serves both to build up a historical record of operating temperatures T3, and provide advanced warning of unusual operation of the motor 324.

(iv) Fourth temperature T4 is the temperature of the ambient air at the location where the refrigeration system is located. Fourth temperature T4 also provides part of a historical record, which in turn helps predict the expected operating time and temperatures of the motor 324 for current values of fourth temperature T4.

Figure 4 shows a control arrangement 400 for the refrigeration system. Control arrangement 400 includes a storage module 410 and a control system 450.

Storage module 410 stores multiple sets of predefined values. Each of the sets of predefined values simulates the temperatures that a different foodstuff attains within the refrigerated enclosure, under a different range of operating conditions of the refrigeration system. There may be many different sets of predefined values, for different foodstuffs. There may be many sets of predefined values for one foodstuff, or type of foodstuff, under different ranges of operating conditions of the refrigeration system. Figure 4 shows a first set of predefined values 412 and a second set of predefined values 414 in storage module 410.

Control system 450 comprises a motor control subsystem 460 for controlling the operation of the motor 424 of the compressor. Motor 424 is a hermetically sealed AC induction motor, with waste heat from the motor at least partially entering the refrigerated enclosure or leaking to the coolant fluid.

Control system 450 also comprises logic module 470. Logic module 470 of the control system 450 is configured to drive the motor control subsystem 460 to activate or deactivate the motor 424 on the basis of the first signal indicative of food temperature T1, the second signal indicative of temperature T2, and one of the first 412 or second 414 sets of predefined values. The particular set of predefined values is selected to match or approximate the temperatures that a foodstuff currently in the enclosure will attain. Logic module 470 ensures soft-start of a motor cycle. Motor control subsystem 460 provides only sufficient voltage to motor 424 to keep a coolant fluid moving in the coolant loop 322, 332, 342 of the food refrigeration system 300, after an optimum suction gas pressure has been attained in the coolant loop.

Motor control subsystem 460 is configured to regulate the voltage applied to motor 424 when the compressor is operating and a load on the compressor varies. This regulation is such that, in operation, the voltage applied to motor 424 is regulated to be the minimum value that provides synchronous rotation of the motor.

Metering subsystem 480 receives data from motor 424 and motor control subsystem 460. Comparison module 482 may receive data from metering subsystem 480. Metering subsystem 480 may carry out all or some of: (i) Capturing data, the data comprising a record of at least the third signal indicative of the motor temperature T3, and times when the compressor is active; (H) Exporting the data to a remote monitoring unit for verification of equipment use and/or energy use; (iii) Capturing and exporting the second signal indicative of the ambient temperature T2 within the enclosure, and the fourth signal indicative of the temperature T4 where the refrigeration system is located, as part of the data.

Metering subsystem 480 develops a historical record of operating characteristics of motor 424. The historical record comprises a proportion of time for which motor 424 is switched on, the first signal indicative of food temperature Ti, and the second, third and fourth signals. Metering subsystem 480 detects an abnormal function of motor 424, based on an increase in the proportion of time for which motor 424 is switched on, above an 'expected' proportion of time. The expected proportion of time is predicted from the historical record of the proportion of time for which motor 424 is switched on for various values of the first temperature T1, and the second, third and fourth signals.

Metering subsystem 480 is configured to capture data on voltage, current, power factor and power quality for the motor operation. Comparison module 482 provides summary information based on at least one of voltage, current, power factor and power quality for the operation of motor 424. Comparison module 482 derives the number of motor cycles, motor run time, and power consumption of motor 424.

Metering subsystem 480 and comparison module 482 together comprise a motor monitoring subsystem. However, the separate functions of metering subsystem 480 and comparison module 482 may be combined into a single subsystem, and they are illustrated as separate elements in figure 4 for ease of explanation. Based on the data and historical records derived from them, the motor monitoring subsystem provides preemptive maintenance alerts and/or indicates an imminent failure of motor 424. The motor monitoring subsystem may indicate an imminent failure of the motor, when: (i) The fourth signal indicates that the ambient temperature has not significantly increased; (H) A target temperature of the enclosure remains fixed; and yet (Hi) In comparison to a prediction of what would be necessary for these conditions, based on the record of historical data, the motor is one of: running hotter, drawing more current and/or running for longer periods.

A set of circumstances such as (i)-(iH) above allows the motor monitoring subsystem to detect that the refrigeration system 300 is working under duress, and/or that an imminent failure can be expected. This condition can thus be investigated before there is inevitable mechanical failure of the compressor with potential loss of foodstuffs, and an unwelcome and potentially dangerous increase in the temperature of the stored food while the problem remains undetected.

A communication module 484 reports via the internet to a remote monitoring station for display, any or all of: (i) The data from the metering subsystem; (H) At least one of the summary information, the voltage, current, power factor or power quality for the motor operation.

The remote monitoring station may then display instantaneous and historical values for the reported parameters.

The present invention may also provide a visual simultaneous digital readout of both the cabinet 'air' temperature T2 and the mimiced 'food' temperature Ti. A proprietary hand held meter can be plugged into the sensor housing inside the cabinet to cross check, verify and recalibrate the settings as required.

None of the cited prior art patent applications enabled direct switching of the compressor or any optimizing of the current drawn by the compressor. So, in prior art systems, the compressor is either switched on or off by the incumbent analogue thermostat, with no intelligent digital control being provided. Furthermore, in prior art systems, there was no inherent digital element that could meter, process and record all the salient parameters affecting equipment performance. However, this can be done with the present invention.

Motor control subsystem 460 will reduce the number of times the compressor starts, in comparison to prior art systems. The number of motor starts, depending on the thermal dynamics of the stored products, may be reduced by up to 50%. At the same time, an optimum longer, deeper 'ideal' cooling cycle will be provided, as determined for the type of stored product. The overall effect of this feature is to reduce energy consumption and extend equipment life.

Motor control subsystem 460 may act to extend a period of operation of the motor, after an optimum suction gas pressure has been attained in a coolant loop of the refrigeration system. The period of operation of motor 424 may then extend beyond the period required to just ensure that a threshold temperature of stored food has been reached, thereby increasing the proportion of the compressor operating time for which the compressor is in a lightly loaded operational phase.

In the field of motor control technology, it is known that a reduction of the terminal voltage by a fixed amount on an ac induction motor that is less than 70% loaded will typically achieve a beneficial reduction in the amount of current drawn. Also, it is known that if the current being drawn can be reduced without slowing the motor down, this will ensure that a greater amount of the current being absorbed will be converted to a job of work' rather than being dissipated as 'heat'. The problem with existing technologies when applied to refrigeration systems is that a hermetically sealed refrigeration compressor is housed within the refrigerant coolant. The compressor has unique operational characteristics during its duty cycle, which prior art systems cannot detect or respond to. The inventors have realized that the compressor motor should only be optimized at specific stages within the cooling cycle. The optimization can be based on: a combined feedback loop from the temperature at up to four points; reactive power; line current; and suction gas pressure, as evidenced by changes in current and reactive power. This optimization is dynamic, rather than employing an arbitrary time delay or fixed reduction in current or voltage as in known systems.

Both the electricity supply on the National Grid and the load on the motor may alter continually, based on a large number of variables. So an arbitrary fixed reduction in the current supplied does not deliver optimum benefits. Furthermore, there is also great cost in providing prior art motor control systems, which involve high production and installation costs in relation to the energy savings that they can deliver.

The control system 400 provides a significantly better level of control. The motor control achieved takes into account the varying duty cycle of the compressor motor 424. This is achieved by constantly calculating the demand on the system and delivering the appropriate amount of current. The current is that which maintains the correct amount of excitation between the motor stator and rotor, so as to maintain full motor speed throughout the duty cycle. Another significant benefit is that, by eliminating excess current that would otherwise convert to 'heat' within the hermetically sealed compressor casing, further isentropic benefits are delivered.

The invention therefore addresses four distinct problems with just one turnkey solution. The advantages achieved may be some or all of: (i) The compressor cycles less often, to maintain any given target temperature; (H) The compressor consumes the minimum necessary current at each stage of every cooling cycle, unlike known systems; (Hi) Future malfunctions of the compressor can be flagged to the owner/operator; (iv) Precise remote monitoring of the parameters that impact on energy efficiency and performance of the equipment is possible, so as to be able to provide benchmarking and implement energy reduction programmes.

Figure 5 illustrates a method 500 of deriving a set of predefined values simulating food 10 temperature in accordance with an embodiment of the invention.

For each of at least two foodstuffs, a foodstuff is selected at step 510. The foodstuff is placed in an environment, a temperature within the environment being controllable. At 520, temperature T1a inside the foodstuff and temperature T2a outside the foodstuff are 15 measured.

At step 530, a step change in the temperature T2a of the environment is applied. At step 540, the resulting changes over time of the temperature Tla inside the foodstuff and the temperature T2a outside the foodstuff are measured.

At step 550, a functional and temporal relationship between the temperature Ti a inside the foodstuff and the temperature T2a outside the foodstuff are derived and stored.

Figure 6 illustrates three possible measurements derived in accordance with the method of figure 5.

In the upper trace of Figure 6, a graph of temperature T (y-axis) versus time t (x-axis) is provided. At time t1, the air temperature within a refrigerated enclosure is changed to a value T2atesti. Trace 610 shows the change to the air temperature T2a. The trace 620 shows the resulting change to the temperature T1a of a first temperature sensor arranged as shown in figure 2. Trace 620 is the trace referred to in step 540 of figure 5, and allows the functional relationship between the temperature within the food simulant and an external applied environmental temperature to be captured and stored. This functional relationship provides a set of predefined values for the refrigerated system to use.

In the middle trace of Figure 6, another graph of temperature T (y-axis) versus time t (x-axis) is provided. At time t1, the air temperature within the refrigerated enclosure is changed to a value T2atest2 that th t exceeds test temperature T2atesti in the upper trace of figure 6. Trace 630 shows the change to the air temperature T2a. The trace 640 shows the resulting change to the temperature T1a of the first temperature sensor arranged as shown in figure 2. The food simulant surrounding the temperature sensor may be the same size and consistency as that used in the text shown by the upper trace in figure 6. Trace 640 is a second functional relationship that provides a further set of predefined values for the refrigerated system to use.

In the lower trace of Figure 6, another graph of temperature T (y-axis) versus time t (x-axis) is provided. At time t1, the air temperature within the refrigerated enclosure is changed to a value T2atest3. At time t2, the air temperature within the refrigerated enclosure is changed back to its initial value. Trace 650 shows the change to the air temperature T2a. The trace 660 shows the resulting change to the temperature T1a of the first temperature sensor arranged as shown in figure 2. The food simulant surrounding the temperature sensor may be the same size and consistency as that used in the text shown by the upper and middle traces in figure 6. However, the size or consistency may be different. Trace 660 is a third functional relationship that provides a further set of predefined values for the refrigerated system to use. The lower trace serves to illustrate that various test conditions may be selected, in order to derive sets of predefined values for storage in storage element 410, such as shown at 412 and 414 in figure 4.

When a particular foodstuff needs to be simulated, the stored functional relationships derived as shown in figures 5 and 6 are retrieved. They can then be applied 'in reverse' to the measured temperature T2 of the air surrounding the surrounding the foodstuff, thus deriving the temperature inside the foodstuff without actually measuring it directly. In practice, a number of similar foodstuffs can be measured and an average function stored for that range of foodstuffs. A limited number of functions can then be saved for use over a very broad range of foodstuffs. Alternatively, bespoke functions can be saved for individual sized amounts of many foodstuffs. Thus the precision of the temperature control provided by the refrigeration system of the invention can be increased by storing sets of values for more foodstuffs, and more samples of different sizes of each foodstuff.

The method therefore may be used to derive at least two separate sets of predefined values for one foodstuff, each of the separate sets being derived for the foodstuff using different values of the step change in the temperature of the environment. This method can be performed for at least two similar foodstuffs, which make up a range of foodstuffs. An average function can be derived and stored for the range of foodstuffs. Once predefined values have been derived in this fashion, a method of estimating the temperature within a foodstuff at a time point comprises retrieving at least one of the sets of predefined values providing a functional and temporal relationship for a foodstuff. The temperature within the foodstuff at the time point can then be derived by applying the functional and temporal relationship for the foodstuff to a temperature measured outside the foodstuff, over a time period preceding the time point. The temperature T1 is of course also available in a deployed system.

Figure 7 illustrates a complete refrigeration system 700 in accordance with the invention. Refrigeration system 700 uses the same temperature variables T1-T4 as described with reference to figure 3.

Refrigerated enclosure 710 provides a chilled space that contains food simulant 712.

Refrigerated enclosure 710 also contains goods to be kept chilled, which are not shown on figure 7. A first temperature sensor 714 within food simulant 712 provides a first signal as a measurement of first temperature T1. Second temperature sensor 716 provides a second signal, which is indicative of the ambient temperature T2 within refrigerated enclosure 710.

Compressor motor 720 is provided with a motor temperature sensor 722. Motor temperature sensor 722 provides a third signal, which is indicative of the motor temperature T3. An ambient temperature sensor 724 provides a fourth signal, which is indicative of an ambient temperature T4 outside the refrigerated enclosure.

The signals indicative of each of T1 -T4 are supplied to temperature control logic 730.

Control strategy logic 740 also receives an input from food temperature simulator 718.

Food temperature simulator 718 may provide a simulation of the actual food temperature, based on the actual measurement of the ambient air temperature T2 within refrigerated enclosure 710 and one or more sets of stored values obtained as shown in figures 5 and 6.

Control strategy logic 740 provides overall motor control, via motor control logic 750 and firing control 752. Motor control logic 750 receives an input from energy sensing circuitry 754. Energy sensing circuitry 754 is in turn connected to coil 756, which may implement intelligent motor energy control ('iMEC') in motor 720. A bypass relay 755 may be connected in parallel to energy sensing circuitry 754. Bypass relay 755, if used, allows motor control logic 750 to directly switch motor 720.

Fan control logic 758 is also fed from control strategy logic 740. Metering subsystem 760 provides inputs to control strategy logic 740.

Display processor 770 drives local display 772. Display 772 provides feedback and operating information to a local user, who may operate keypad/keyboard 774 or other input devices. Enigin's 'Eniscope' connection 780 leads to an Eniscope hub, which exports data to the internet for remote surveillance.

In the arrangement according to figure 7, the refrigeration system exports data to Enigin's 'Eniscope' system. Thus the metering subsystem 760 and control strategy logic 740 contain within them on-board metering elements with the ability to connect directly to an Eniscope Real-time Energy Management System via connection 780 and the hub.

See also communication module 484 in figure 4. This configuration allows information relating to the operation of the compressor and plant to be exported to the world wide web, for remote analysis and trouble-shooting. A refrigeration system anywhere in the world can thus be monitored and analysed from any location where Enigin's 'Eniscope' system is installed.

A feature of the invention is that it monitors four temperature points that directly affect the performance of the compressor. These are food simulant temperature T1, internal cabinet air temperature T2, compressor run temperature T3 and ambient air temperature T4. In addition, information is captured on the number of cycles, run time, and power consumption so as to provide preemptive maintenance alerts.

Known systems were able to record and display the temperature of cabinets. This function could even be performed remotely, which would alert engineers to the fact that a compressor had already failed. Such failure would become apparent due to a corresponding rise in cabinet temperature after the compressor failure. This known technology only alerts an engineer once the malfunction has already occurred. It was often then too late to save either the equipment, through pre-emptive maintenance, or the stored produce. With some known systems, bacterially contaminated food might have been served to the general public, after the motor had failed but before the problem had been detected.

The main benefit of being able to predict motor failure with the invention is realizable because the monitoring subsystem can re-use the significant amount of information it has captured while controlling and optimizing the compressor. This captured data is used to create a norm' or benchmark' for the running of a given piece of equipment, i.e. a motor in use in a particular refrigeration system, based on its own unique historical record. If at some later stage the compressor has to work harder to achieve the same job of work, and/or runs hotter as a consequence, the monitoring subsystem or remote circuitry can alert the owner before the equipment fails. When the monitoring subsystem is able to connect to Enigin's Eniscope system, all of the functionality and performance of the plant can be reported in real time and checked in an historical analysis portal.

There is prior art relating to the granular metering of individual circuits, and potentially 30 remote appliances. However, the known arrangements simply record and export data. They are not located within or beside the compressor and do not provide a component part of an energy saving device. One known arrangement is shown by W02012059737.

Figure 8 provides an example of graphs that show the recorded motor load profiles for a prior art arrangement and that of the invention.

The traces of figure 8 cover 24 hours of operation. The upper trace of Figure 8 shows the percentage of maximum power at which a compressor will operate, without the invention. The lower trace illustrates the operation of a compressor run using the invention, for comparable operating conditions. In the lower trace, the peak power does not reach that in the upper trace. There may be more operations of the motor, but they are at a more constant power level, with longer periods when the motor is not switched on.

Figure 9 provides another example of graphs that show the recorded motor load profiles for a prior art arrangement and that of the invention.

The traces of figure 9 cover 5 days of operation. The upper trace of Figure 9 shows operation of the compressor, without the invention. The lower trace illustrates the operation of a compressor run using the invention, for comparable operating conditions. In the lower trace, there is considerably less temperature fluctuation.

In summary, the invention comprises a single refrigeration system that may be 'web-enabled' via Enigin's 'Eniscope'. It is a unique total solution for refrigerated equipment. The invention provides: i) An intelligent dynamic motor optimizer, with specific design features to maximize efficiency on hermetically sealed compressors; ii) An accurate food simulant digital thermostat; iii) A monitor and Eniscope enabled energy meter element; iv) A single set of circuitry to implement all the above functionality. The algorithms for acting on the temperature reference points (intelligence) may be embedded in software within the invention, or provided in an application specific integrated circuit (ASIC).

The invention builds on the realization that the temperature change that occurs in the 'air', when a door of a refrigerated enclosure is opened, will be at a totally different rate of change than the change that would occur within the mass of the food within the enclosure, over a longer time period. Here the refrigerated enclosure may be a cabinet of a commercial refrigerator. The rates of change are plotted using the principles of thermodynamic entropy and the method of figure 5 explained above. The known technology simply avoided the issue, by providing a thermal mass to act as a buffer.

The thermal mass stopped the probe thermostat responding to sudden unwelcome and short term air temperature changes. However the invention mimics what happens in the analogue world, i.e. within the 'food' inside a cabinet, using digital analysis and prediction. The intelligent digital thermostat element of the invention will know the difference, and decide using algorithms based on both time and temperature change profile whether or not it is time to energise the compressor motor.

Because the compressor is controlled in effect by an 'intelligent electronic switch', the compressor motor can be started and stopped via the on-board triac. This on/off switching is based on internal 'food simulant' temperature calculated by the microprocessor and sensed by the first temperature sensor, which may be a therm istor. This approach will automatically soft-start the compressor, thereby reducing peak demand. In addition, the approach results in cooler and quieter running of the motor, with a much improved power factor. This reduces any reactive power charges. By reducing waste heat, the invention also potentially reduces the ambient temperature around the cabinet, which further lightens the load on the compressor (isentropic effect).

As explained with reference to figures 1-7, the refrigeration system is notable for: (i) Digital software programed to mimic the thermal characteristics of a particular stored product or food.

(H) Control hardware circuitry and unique software algorithms designed to optimize the efficiency of a hermetically sealed compressor motor, during each phase of the cooling cycle.

(Hi) Metering technology designed to work in conjunction with Enigin's Eniscope system, so as to be able to monitor and benchmark equipment performance and provide energy efficiency data in real-time via the internet.

(iv) All of the above in one simple turnkey solution providing a unique synergistic combination of advantages in a very cost effective and convenient solution.

Bespoke digital values and/or algorithms can be provided, designed to replicate the thermal characteristics of differing foods and products as they absorb energy (heat) in response to significant changes in ambient air temperature. Control hardware and software algorithms are designed to control the flow of current (and consequential heat) within a hermetically sealed ac induction motor. This control applies to various load changes during each cooling cycle. A metering subsystem is specifically designed to work in conjunction with Enigin's Eniscope Real-time Energy Management System. All of these elements may be provided in one simple enclosure that will fit within an existing system with the minimum of installation time.

The invention may be provided as a bespoke refrigeration system. However, the invention may be used as a 'retro fit' on existing equipment. The invention could be incorporated, by an original equipment manufacturer, as an enhancement to control circuitry on generic equipment, e.g. motor compressors. The invention may draw information from a variety of designs of 'food simulant blocks' that are therm istor based, and then use the data to control compressor cycles. Although the invention is designed to work with Enigin's 'Eniscope', it could be configured to work equally well on other proprietary Building Energy Management Systems (BEMS) to provide salient energy management and equipment performance data. This may be done either locally, or via the internet. However, the invention does not need to record and export information, in order to provide significant benefits to compressor driven plant. Each feature of the invention works together to provide a synergistic and holistic solution. Any feature deployed independently could provide significant improvements and benefits to refrigeration plant. Having the option to 'mimic' and select various food characteristics is beneficial but this is not essential to the functionality of the invention and stored values for an averaged 'typical' food simulant software program would be enough to provide significant benefits over known systems.

A generic hand-held digital meter can be connected to the sensor housing, as a convenient way to ensure correct calibration. However, this is not essential to the performance of the invention. While preferred, it is not essential to the invention to be able to remotely display either or both of the air or food mimicking temperature.

In the embodiments of the invention described thus far, the sensor arrangement of figure 2 is used. In those embodiments, temperature sensor 240 of figure 2 or 362 of figure 3 provides the first signal referred to in appended claim 1.

Figure 10 illustrates a further embodiment of a force-cooled food refrigeration system 1000 in accordance with the invention, which does not use the temperature sensor 240 of figure 2 or 362 of figure 3. The reference numbers on figure 10 correspond to the similarly numbered references on figure 3. However, in figure 10, there is no simulant body or first temperature sensor corresponding to references 360 and 362 of figure 3.

The force-cooled food refrigeration system 1000 of figure 10 does employ one temperature sensor 1070 within enclosure 1010. Temperature sensor 1070 is configured to provide a signal, the signal being a measure of ambient temperature within the enclosure 1010.

The embodiment of figure 10 employs at least two sets of predefined values, which are predetermined digital values for the temperatures attained within one or more foodstuffs. Each set of predefined values simulates the temperatures that a foodstuff 1050, 1052 will attain within enclosure 1010 under different ranges of ambient temperatures, as measured by temperature sensor 1070 in enclosure 1010. A particular set of the predefined values will be selected for a particular foodstuff, and/or for particular package sizes of foodstuff, when that foodstuff and/or package size is placed in the enclosure 1010.

With the embodiment of figure 10, the control system is able to control the operation of the motor of the compressor as described with reference to figures 2-9. However, the control system is configured to drive the motor control subsystem without receiving a real-time signal indicating the actual measured temperature within a simulated foodstuff in the enclosure 1010 of the refrigeration system 1000, i.e. without a temperature measurement such as that provided by temperature sensor 240 of figure 2 or temperature sensor 362 in figure 3.

The sets of digital predefined values of temperatures may however initially be obtained by means of temperature sensors located in real or simulated foodstuffs, for various ambient temperatures within a test enclosure or a real refrigerated enclosure 1010. Subsequently, in use of the force-cooled food refrigeration system 1000 of figure 10, the sets of digital predefined values of temperatures are then sufficient to estimate the temperature within actual foodstuffs 1050 and 1052 that are present in enclosure 1010. This estimation is based only on a measure of the development of the ambient temperature with time, from temperature sensor 1070.

The advantage of the force-cooled food refrigeration system 1000 of figure 10 is that there is no need to provide a food simulant body and a temperature sensor within that body, in deployed systems. This may provide one or more of the following advantages: (i) Allowing extra space with the refrigerated enclosure 1010; (ii) Less vulnerability to component damage; (iii) An easier enclosure 1010 to clean; (iv) No need to provide a mounting bracket with enclosure 1010 to mount a food simulant body, as may be commonly done with the embodiment of figure 3.

Temperature sensor 1080 may be provided to measure the temperature outside enclosure 1010. Temperature sensor 1028 may be provided to measure the temperature of motor 1024. These signals may be used as described previously for the signals from the corresponding temperature sensors of figure 3.