GB2356725A

GB2356725A - Refrigerator monitoring and alarm system

Info

Publication number: GB2356725A
Application number: GB9927972A
Authority: GB
Inventors: Neil Rothwell; Paul John Gildea; Eric John Atherton
Original assignee: DATA DETECTION DYNAMICS Ltd; Plus Design Ltd
Current assignee: DATA DETECTION DYNAMICS Ltd; Plus Design Ltd
Priority date: 1999-11-29
Filing date: 1999-11-29
Publication date: 2001-05-30
Also published as: GB9927972D0

Description

2356725 REFRIGERATION PROTECTION SYSTEM Refrigeration has become a key

element in the supply chains of various industries. Examples of such industries are the food and drug industries, which involve storage, transport and, where appropriate, display for sale of foods, drugs, vaccines and other temperature-sensitive products. In particular, due to serious health and safety implications, there are now strict regulations in force regarding the maximum temperature at which frozen and chilled foods can be stored. If these temperatures are exceeded, due to refrigeration failure or overload, entire consignments, or cabinets, of food have to be condemned at considerable economic cost and inconvenience.

In many countries, it is mandatory to have a refrigeration monitoring system in place to detect when the temperature in refrigeration units has exceeded certain levels. Such systems are well known and in everyday use. Monitoring systems can also be connected up to the telephone network, to remotely signal a refrigeration failure, as disclosed in for example, US4482785. The monitoring of refrigerated vehicles is also important as disclosed in, for example, US4385289.

It is important to note that these prior art systems detect when a failure has occurred, and the temperature has exceeded a certain threshold. This serves to alert the refrigeration operator of the situation, but often does not prevent the economic cost and inconvenience of re-stocking all the products in the failed refrigeration unit, as the critical upper temperature limit has already been or will quickly be exceeded.

It is an object of the present invention to provide a means for predicting a forthcoming refrigeration failure before it occurs. Such'prediction enables timely remedial action to be taken before the cabinet, vehicle, or other refrigeration unit, reaches the critical upper temperature limit at which the perishable contents have to be condemned. It will be immediately apparent that the predictive nature of the current invention prevents considerable economic loss.

According to one aspect, the present invention provides a protection system for preventing failure of a refrigeration unit, comprising:

2 (a) internal temperature monitoring means for monitoring the internal temperature of the refrigeration unit; (b) one or more second monitoring means adapted to monitor parameter(s) being indicative of subsequent increases in the internal temperature and so being predictive of failure of the refrigeration unit; and (c) alarm means adapted to be activated by either the internal temperature monitoring means, or the one or more second monitoring means, when the internal temperature or other parameter(s) indicate subsequent failure of the refrigeration unit.

In one embodiment, the one or more operation parameters may relate to the electrical supply of a refrigeration fan system. In large refrigeration systems, a central refrigeration plant provides refrigerant to coolers in the remote cabinets. In each remote cabinet, fans are used to create airflow over these coolers. Often several fans serve one cabinet, and the loss of one fan is not immediately critical (although the accumulative build up of ice during the cool/defrost cycles can later lead to a temperature alarm condition.) Since the voltage and current of the electrical supply to the cabinet can be monitored, the power to the cabinet can be computed, using well-known methods. If a fan is blocked, or a fan motor fails, the power to the cabinet changes from normal operating levels, which may be taken as being indicative of potential failure of the cabinet, and an alarm can be generated. This alarm can be sent to a remote call centre via a telecommunications network to trigger a response from a service engineer. A timely response from the service engineer can restore the cabinet fan system to full efficiency before the cabinet temperature rises, and so prevent the loss of perishable product in the cabinet.

The one or more operation parameters may also typically relate to a refrigeration compressor of the refrigeration unit. Such parameters may include vibration levels, refrigerant levels, and compressor motor voltage, current and power consumption. A rise in vibration levels may indicate impending mechanical failure that requires urgent 3 investigation. Trends in power levels and refrigerant levels may indicate that the refrigeration system is approaching capacity limits, well before these limits are actually reached. The importance of being able to predict a forthcoming over-load situation is that preventative action can be taken before freezer cabinet temperatures begin to rise or to rise too far.

The one or more operation parameters may also, in a further embodiment, relate to the total energy required to perform a defrost cycle for the refrigeration unit, particularly a freezer cabinet. This total energy is closely related to the amount of ice build-up in the freezer cabinet prior to the defrost cycle, and is a useful indication of the condition of the refrigeration system.

Preferably, a processor (typically either a desk top computer or microprocessor) receives information from both the operation parameter inputs for operation parameters other than the freezer cabinet temperature, as well as, the freezer cabinet temperature itself. Such a processor may be characterised by an ability to predict a freezer cabinet over-temperature condition by analysing the trends in the operation parameters. The processor may "learn" the desired response by analysing large amounts of historical data, using "fuzzy logic" techniques, well known to those skilled in the art.

Alternatively, the processor may contain rules and algorithms that are devised by an expert operator, after reviewing historical results, and analysing the dynamics of the refrigeration system, these rules and algorithms being then programmed into the processor. Alternatively, the processor may contain a mathematical model of the refrigeration system, the current state of this model being continuously updated from the real parameters sensed by the processor. In this case, the processor repeatedly runs the model forward faster than "real lime", to obtain a prediction of the freezer cabinet temperature in the future. It is important to note that the processor may be located close to the freezer itself, or may in fact be a remote computer connected to the freezer via a telecommunications network.

The present invention also provides, according to a second aspect, a method of protecting a refrigeration unit comprising monitoring the internal temperature of the unit 4 and one or more other parameters being indicative of subsequent increases in internal temperature, and activating an alarm when the internal temperature or other parameter(s) indicate subsequent failure of the refrigeration unit.

Other preferred features of the invention will be apparent from the following description and from the subsidiary claims of the specification.

The invention will now be further described, merely by way of example, by reference to the accompanying drawings, in which:

Figure I is a diagrammatic representation of two freezer cabinets provided with a protection system according to a preferred example of the invention, Figure 2 shows a remote computer connected to the protection system of Figure 1, and Figure 3 is a typical graph of temperature against time when a fault develops in one of the freezer cabinets.

Referring initially to Figure 1, this shows two freezer cabinets 10, that are.cooled by a refrigeration plant 11 which consists of a motor, compressor, and condenser system. Coolant flows from the refrigeration plant 11 to the freezer cabinets 10 via pipes 12. The refrigeration plant 11 receives power from a mains supply point 13 via mains cables 14 through a refrigeration processor 15.

Each freezer cabinet 10 contains fans 16 that receive power from a mains supply point 17 via mains cables 18 through a freezer processor 19.

The refrigeration processor 15 monitors an external temperature sensor 20, a compressor temperature sensor 21, a compressor vibration sensor 22 and a refrigerant level sensor 23. The processor 15 also monitors the supply current and voltage to the refrigeration plant 11 and computes the instantaneous power and power factor. The readings from these sensors 20-23 together with the computed instantaneous power and power factor, are herein collectively designated the refrigeration plant process parameters.

The freezer processors 19 monitor external temperature sensors 24, freezer cabinet temperature sensors 25 and ambient humidity sensors 26. Each freezer processor 19 also monitors the supply current and voltage to the fans inside its freezer cabinet 10 and computes the fan instantaneous power and power factor. The readings from these sensors 24-26, together with the fan computed instantaneous power and power factor, will collectively be designated the freezer cabinets process parameters.

The freezer processors 19 send the freezer cabinet process parameters to the refrigeration processor 15 through a digital communications cable 27.

The refrigeration processor 15 sends the freezer cabinet process parameters from the freezer processors 19 and also the refrigeration plant process parameters, to a remote computer 30 via modems 31 and 32 (see additionally Figure 2.). The computer is connected to an alarm system 33.

The remote computer 30 builds a database of freezer cabinet process parameters and refrigeration plant process parameters over a period of several weeks or months. Preferably, this period contains a range of external temperature and humidity conditions, so that the performance of the refrigeration plant and freezer cabinets can be observed under different ambient conditions. In addition, deliberate faults, such as disconnected fans 16 in the freezer cabinets 10 and blocked fans 16 in the freezer cabinets 10 are temporarily introduced, and the response of the freezer cabinet process parameters and refrigeration plant process parameters are observed and recorded in the database. The database is then analysed by a refrigeration expert, who sets normal operating limits for the refrigeration plant process parameters and the freezer cabinet process parameters. These normal operating limits may be dependent on external temperature and humidity. The remote computer 30 is next programmed to continually monitor the freezer cabinet process parameters and the refrigeration plant process parameters against the normal operating limits set by the refrigeration expert. The remote computer 30 is also programmed to activate the alarm system 33 should 6 these said process parameters trend outside the said normal operating limits. In the event that the alarm system 33 is activated, a refrigeration expert can be notified to analyse the current state of the said process parameters, and notify a service engineer to visit the site of the refrigeration plant 11 and freezer cabinets 10 to effect a repair.

It is particularly important to note that because many process parameters are monitored by the remote computer 30, in addition to the freezer cabinet temperature sensor 25, it is possible to detect alarm conditions that will lead to a critical rise in temperature in one of the freezer cabinets 10 some time before the actual temperature in the freezer cabinets 10 rises to a level that will lead to a loss of perishable produce stored in the freezer cabinets 10.

Figure 3 shows a graph of temperature on the vertical axis against time on the horizontal axis for one of the freezer cabinets 10. The steady temperature upper trace 40 on the graph is the critical maximum temperature level of the cabinet 10; if this is exceeded, the contents of the cabinet 10 have to be destroyed.

The trace 41 starting below the upper trace 40 is the actual temperature in the cabinet 10, which suddenly at 42 starts to rise steadily to cross the upper trace 40 at crossover point 43.

The reason for the rising temperature was, in this example, the failure of a cooling fan, which is shown by the lower trace 44 of the power used by the cooling fans on the same time axis. The drop in power at 45 marks the reduction in power consumption arising from that fan no longer working.

The graph shows that the loss of a fan at point A in time initially has a negligible effect on the temperature of the cabinet. Monitoring the cabinet temperature alone would only give the period from a point B in time, when a temperature rise can first be sensed, to a point C in time of the crossover point 43, for repairs to the failed fan to be effected and the contents of the freezer saved. Monitoring the fan power in accordance with this invention would give the much longer period from point A to point C to repair the fan.

7 Optionally, once sufficient experience has been obtained, and the database stored on remote computer 30 is considered adequate, the said normal operating limits for said process parameters can be downloaded from remote computer 30 to the processor 15. Once this has taken place, the processor 15 need only communicate with the remote computer 30 occasionally, or by exception when an alarm condition occurs, with a consequent saving on telecommunications costs.

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Claims

1. A protection system for preventing failure of a refrigeration unit, comprising:

(a) internal temperature monitoring means for monitoring the internal temperature of the refrigeration unit; (b) one or more second monitoring means adapted to monitor parameter(s) being indicative of subsequent increases in the internal temperature and so being predictive of failure of the refrigeration unit; and (c) alarm means adapted to be activated by either the internal temperature monitoring means, or the one or more second monitoring means, when the internal temperature or other parameter(s) indicate subsequent failure of the refrigeration unit.

2. A protection system as claimed in Claim 1, wherein the one or more second monitoring means is adapted to measure any one or more of:

(a) electrical power supplied to a refrigeration fan system; (a) the function of a refrigeration compressor of the refrigeration unit; (b) the total energy required to perform a defrost cycle for the refrigeration unit; (c) the voltage and/or current and/or power consumption of the refrigeration unit; (d) the degree of vibration of the refrigeration unit; and (e) the level of refrigerant of the refrigeration unit.

3. A protection system according to any one of the preceding claims, wherein the alarm means includes a computer programme adapted to receive data relating to the internal temperature or other parameter(s) and adapted to predict failure of the refrigeration unit from said data.

4. A protection system according to any one of the preceding claims wherein the refrigeration unit is a freezer unit.

5. A protection system according to any one of the preceding claims wherein the refrigeration unit is stationary or mobile.

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6. A protection system according to any one of the preceding claims wherein the refrigeration unit is a refrigerator including freezer storage.

7. A refrigeration unit comprises a protection system according to any one of the preceding claims.

8. A protection system, or a refrigeration unit comprising such a system, substantially as hereinbefore described with referende to, and/or as shown in, the accompanying drawing.

9. A method of protecting a refrigeration unit comprising monitoring the internal temperature of the unit and one or more other parameters being indicative of subsequent increases in internal temperature, and activating an alarm when the internal temperature or other parameter(s) indicate subsequent failure of the refrigeration unit.

10. A method of protecting a refrigeration unit according to Claim 9 wherein said one or more other parameters include:

(a) electrical power supplied to a refrigeration fan system; (b) the function of a refrigeration compressor of the refrigeration unit; (c) the total energy required to perform a defrost cycle for the refrigeration unit; (d) the voltage and/or current and/or power consumption of the refrigeration unit; (e) the degree of vibration of the refrigeration unit; and (f) the level of refrigerant of the refrigeration unit.

1 1.A method of protecting a refrigeration unit substantially as hereinbefore described with reference to the accompanying drawings.