EP4027082A1

EP4027082A1 - Method of actuation of a refrigeration apparatus and refrigeration apparatus

Info

Publication number: EP4027082A1
Application number: EP21217458.5A
Authority: EP
Inventors: Luca Mattiello; Willy MUVEGI
Original assignee: Carel Industries SpA
Current assignee: Carel Industries SpA
Priority date: 2021-01-07
Filing date: 2021-12-23
Publication date: 2022-07-13
Also published as: IT202100000182A1

Abstract

Described is a method of operating a refrigeration apparatus (10) equipped with a refrigerated compartment (11) and a cold exchanger (12) and configured to absorb heat from inside the refrigerated compartment (11) according to a reference parameter.

The method comprises:
- a step A wherein the reference parameter is set to a first value;
- a step B wherein the reference parameter is set to a second value lower than the first value;
- a step C wherein the cold exchanger (12) is heated to defrost it.

Step B precedes step C and the second value of the reference parameter is set in such a way that during step C an ambient temperature Ta detected in the refrigerated compartment (11) does not exceed an upper threshold value Tmax.

Description

TECHNICAL FIELD

This invention relates to a method of activating a refrigeration apparatus and to a refrigeration apparatus designed for operating according to the method. In particular, the invention allows the energy consumption of a refrigeration apparatus to be optimised by optimising the temperature control of the refrigerated compartment of the refrigeration apparatus.

BACKGROUND ART

Refrigeration apparatuses are currently known for storing consumer products, such as for example food products.
Such refrigeration apparatuses have a refrigerated compartment designed for housing products to be kept at a storage temperature.
The UNI-EN-ISO 23953 standard is taken as a reference as it is specific for refrigeration apparatuses designed for the display and sale of products. The standard defines environmental test conditions of the refrigeration apparatus and reference thermal conditions of the interior of the refrigerated compartment, which must be met during the test in order to be able to declare the refrigeration apparatus suitable for the intended use.
These thermal conditions vary according to the intended use to be certified for the refrigeration apparatus. For example, they are less strict for a refrigeration apparatus that is to be declared intended for the cooling of beverages, more strict if the designated destination is the refrigeration of dairy products and even stricter if the destination to be declared is the storage of frozen products.
In particular, in the case of storing frozen products, it is necessary that, during a predefined test period, the temperature of the products inside the refrigerated compartment does not exceed an upper thermal threshold, which can be for example -15°C, and falls below a lower thermal threshold, for example -18°C.
In other words, an apparatus passes a test based on these thermal conditions if test probes arranged inside the refrigerated compartment detect a temperature trend that is always maintained between the upper thermal threshold and the lower thermal threshold, falling at least one time during the test period, below the lower thermal threshold.
These conditions must be met during the entire test period, which must also include the defrosting step of the refrigeration apparatus during which, therefore, the temperature detected by the test probes must not exceed the upper thermal threshold.
During the defrosting step, the refrigeration action of the refrigeration apparatus is interrupted and the cold exchanger, or evaporator, which is in thermal communication with the refrigerated compartment, to cool it, can be heated to remove the frost that has formed on the interface surface between the latter and the refrigerated compartment.
During this defrosting step it is clear that the temperature inside the refrigerated compartment rises.
For this reason, the temperature inside the refrigerated compartment of known refrigeration apparatuses is currently controlled in such a way as to take into account the temperature rise that occurs in the defrosting step.
In other words, once the operating parameters of the machine have been predefined in order to obtain an effective defrosting, the reference value of the temperature inside the refrigerated compartment is set in such a way that the temperature increase resulting from the defrosting step is not sufficient to bring the temperature of the products contained in the refrigerated compartment above the upper thermal threshold.
In other words, a reference temperature value of the refrigerated compartment is set sufficiently low so that, following the temperature increase due to the execution of the defrosting step, the actual temperature of the refrigerated compartment does not exceed the upper thermal threshold.

SUMMARY OF THE INVENTION

The problem underlying the invention is that of improving the energy efficiency of traditional apparatuses, ensuring that even after the defrosting step has been carried out, the actual temperature of the refrigerated compartment does not exceed the upper thermal threshold.
The object of the invention is to provide a method for activating a refrigeration apparatus and a refrigeration apparatus which solve this problem.
Within this object, an aim of the invention is to provide a method of activating a refrigeration apparatus and a refrigeration apparatus which allows a temperature set-point for the refrigerated compartment to be fixed which is on average higher than in traditional solutions, whilst respecting the thermal conditions imposed by the above-mentioned standard.
Another aim of the invention consists in proposing a method for activating a refrigeration unit apparatus and a refrigeration unit apparatus which allow better energy yields to be obtained.
This object, as well as these and other aims which will emerge more fully below, are achieved by a method of activating a refrigeration apparatus and by a refrigeration apparatus according to the appended independent claims. Detailed features of a method of activating a refrigeration apparatus and a refrigeration apparatus according to the invention are indicated in the dependent claims.
Further features and advantages of the invention will emerge more fully from the description of a preferred but not exclusive embodiment of a method of activating a refrigeration apparatus and a refrigeration apparatus according to the invention, illustrated by way of non-limiting example in the accompanying drawings listed below.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a simplified diagram of a refrigeration apparatus according to the present invention; and
Figure 2 illustrates a simplified diagram of a temporal trend representing the operation of a refrigeration apparatus activated in accordance with an activation method according to the invention.

DETAILED DESCRIPTION

With particular reference to Figure 1, the numeral 10 indicates in its entirety a refrigeration apparatus equipped with a refrigerated compartment 11 and a cold exchanger 12 which is in thermal communication with the refrigerated compartment 11 to refrigerate it.
The refrigeration apparatus 10 is configured to absorb heat from the inside of the refrigerated compartment 11, by means of the cold exchanger 12, as a function of a temperature set-point Tsp. The temperature set-point Tsp is intended to be the operating temperature of the refrigerated compartment 11, and depends on the relative intended use.
The refrigeration apparatus 10 can comprise a first temperature sensor 13 located inside the refrigerated compartment 11 and be configured or programmed to carry out a cooling action of the refrigerated compartment 11 designed to bring the ambient temperature Ta of the refrigerated compartment 11, measured for example by the first temperature sensor 13, to a value equal to the temperature set-point Tsp, except for any deviation.
The refrigeration apparatus 10 can comprise a refrigeration unit 14 with vapour compression which can use as a refrigerant fluid for example propane or, according to a different example, carbon dioxide.
The cold exchanger 12 can be included in the refrigeration unit 14.
The latter can comprise in succession to the cold exchanger 12, a compressor 15, a hot exchanger 16 designed for dissipating the heat absorbed by the cold exchanger 12 and an expansion unit 17 connected in turn to the cold exchanger, to form a ring to actuate a refrigeration cycle.
The hot exchanger 16 can be connected to a water loop 18 to exchange heat with a cooling liquid, otherwise it can be cooled by convection, natural or forced, dissipating heat directly into the environment surrounding the refrigeration apparatus 10.
The refrigeration unit apparatus 10 can comprise a controller, not shown, connected to the first temperature sensor 13 and programmed to activate the refrigeration unit 14 so as to absorb heat from the refrigerated compartment 11 to bring the ambient temperature Ta to tend towards or follow the value of the temperature set-point Tsp.
The refrigeration apparatus 10 can also comprise a second temperature sensor 19 located downstream of the cold exchanger 12 to detect a superheating temperature Tsh from which it is possible to calculate the superheating SH, known in the jargon as superheat, of the refrigerant fluid with respect to the evaporation temperature at the cold exchanger 12.
In other words, the superheating SH is calculated as the difference between the superheating temperature Tsh and the evaporation temperature of the refrigerant fluid at the outlet of the cold exchanger, measured at the inlet of the compressor 15 or, in any case, upstream of the latter.
The evaporation temperature can be measured indirectly, by measuring the pressure of the refrigerant fluid and applying formulas and principles known in the prior art.
The controller can be configured to activate the refrigeration unit 14 so that the superheating SH tends towards or follows a superheating value of the set-point SHsp.
The refrigerated compartment 11 can be opened and closed, for example by being provided with at least one door 20 designed to close or open an opening 21 of the refrigerated compartment 11 to allow a user to access the interior of the latter in order to take out/introduce products.
Furthermore, the refrigeration apparatus 10 can comprise lighting means, not illustrated, designed for illuminating the interior of the refrigerated compartment 11, for example located inside the latter and preferably comprising LEDs or consisting of the latter in order to limit heating, which, in use, can occur in the refrigerated compartment.
The controller can be configured to automatically turn off and turn on the lighting means at preset times, possibly adjustable by an operator, or - for example - following the detection of the approach of a user which can be detected by a motion or proximity sensor with which the refrigeration apparatus can be equipped.
The controller can be configured to operate the refrigeration apparatus in order to regulate the temperature set-point Tsp so that within a period of one day the ambient temperature Ta in the refrigerated compartment never rises above a higher threshold Tmax, for example equal to -15°C, and falls at least once below a lower threshold Tmin, which can be equal to -18°C.
Naturally, the temperature set-point Tsp is different from the upper threshold temperature Tmax, in particular it is lower than Tmax.
The cooling action carried out by the refrigeration unit 14 controlled by the controller can be operated according to a feedback algorithm based on the difference between the ambient temperature Ta, detected in the refrigerated compartment 11, and the temperature set-point Tsp.
The value of the superheating set-point SHsp can be varied by the controller on the basis of an energy optimisation algorithm of the refrigeration unit 14. In particular, the invention relates to a method of activating a refrigeration apparatus 10, for example as described above, configured to absorb heat from the inside of the refrigerated compartment 11 by means of the cold exchanger 12, as a function of a reference parameter, the method comprising:

a step A wherein the reference parameter is set to a first value;
a step B wherein the reference parameter is set to a second value lower than the first value (step B is therefore also called pre-cooling step);
a step C wherein the cold exchanger 12 is heated to defrost it.

Step B precedes step C and the second value of the reference parameter is set in such a way that, during step C, the ambient temperature Ta detected in the refrigerated compartment 11 does not exceed an upper threshold value Tmax. The reference parameter is chosen from:

the temperature set-point Tsp;
the superheating set-point SHsp.

Thanks to the activation method according to the invention, in practice the temperature inside the refrigerated compartment 11 is lowered, varying the reference parameter, in such a way that the heating aimed at defrosting the cold exchanger 12 does not raise the temperature of the refrigerated compartment 11 above the upper threshold value Tmax.
In other words, according to the activation method in accordance with the invention, a thermal flywheel effect is generated in the refrigerated compartment 11 which in this way, even after or during step C, of defrosting, does not heat up excessively, that is, it does not allow the products contained in it to heat up in an unacceptable manner.
Thanks to the activation method, during step A the temperature of the refrigerated compartment 11 can be kept at a higher value than what would be necessary to prevent the ambient temperature Ta from exceeding the upper threshold value Tmax if step C was not preceded by step B.
The duration of step B and the difference between the first value and the second value of the reference parameter, as well as the magnitude of the first value of the reference parameter itself, can be defined according to the contingent requirements of implementation of the invention and may possibly be automatically set by the controller according to an algorithm for optimising the operation of the refrigeration unit that minimises the energy consumption, whilst obtaining an effective defrosting of the cold exchanger 12 in step C.
Clearly, the ambient temperature Ta can preferably mean the temperature of a product placed inside the refrigerated compartment 11 and not necessarily the measured temperature of the air contained therein.
By way of example, the first value of the temperature set-point Tsp can be - 18°C, the second value equal to -21°C with the duration of step B for example equal to 10 hours with conditions external to the refrigeration apparatus 10 which can be, for example, 25°C of ambient temperature with 60% relative humidity.
In order to optimise the thermal flywheel effect, step C can start at the end of step B, that is, immediately following the latter.
That is to say, step B can be performed immediately before step C.
In other words, it is clear that step B prior to the defrosting is performed by setting a different working point of the compressor compared to that of the standard operation envisaged in step A. Therefore, in step B, before the start of defrosting step C, a variation of the temperature/superheating setpoints Tsp, SHsp (or of the heat request) can be made with respect to step A, which preferably corresponds to a lowering of these setpoints.
According to preferred variants, in step B it is possible to foresee the variation of only one of the temperature/superheating setpoints Tsp, SHsp with respect to step A (for example, a lowering or raising of the superheating setpoint SHsp only), or a variation of both (increase or decrease) differently from each other.
By appropriately adjusting, according to the operating parameters of the refrigeration apparatus, the temperature Tsp and superheating SHsp set points, it is possible to calibrate the best working condition of the compressor (as regards the suction part) both for step A (normal operation of the apparatus) and for step B (pre-cooling), together with the length of stay involved in each step.
Consequently, the method according to the invention, in addition to allowing the ambient temperature Ta detected in the refrigerated compartment 11 to be maintained lower than the upper threshold value Tmax during the defrosting, also allows a further advantage to be achieved from the energy point of view.
In fact, the pre-cooling step B is not intended as a mere forcing of the compressor operation - by timing or by lowering the shutdown threshold, neglecting the thermal request - but it is an integral part of the operation of the refrigeration apparatus, which provides for a setting up of the operating parameters, such as temperature Tsp/superheating SHsp set-points and duration of step B itself, according to the conditions of best energy yield.
In accordance with the present operating method, a target value To can be set for a reference temperature, greater than the second value of the temperature set-point Tsp, and step C can be terminated when the reference temperature reaches the target value To, or when it is not greater than the target To value for a predefined target time interval, or if a predefined maximum time duration of step C is reached.
The reference temperature can be a temperature measured on or near the cold exchanger, for example by means of a third temperature sensor 22.
Or, the reference temperature can be the ambient temperature Ta.
The ambient temperature Ta, in general, instead of being measured by the first temperature sensor 13 could be measured by a third temperature sensor 22 which can be positioned and/or configured to measure a temperature of the cold exchanger 12 or of an area of the refrigerated compartment 11 in the vicinity of the cold exchanger 12 itself. The second value of the temperature set-point Tsp and/or a duration of the second step B can be chosen according to the operating data of the refrigeration apparatus 10 and in such a way that, during step C, the ambient temperature Ta reaches a maximum value which is less than the upper threshold value Tmax by a difference equal to a predefined safety deviation.
The extent of the safety deviation can be defined in such a way as to ensure that fluctuations in the operation of the refrigeration unit, for example due to the introduction of non-cooled products into the refrigerated compartment 11 before the start of step C, do not bring the ambient temperature Ta to exceed the upper threshold value Tmax.
The controller can be configured to detect, for example by means of a closing sensor, the opening and closing of the refrigerated compartment 11 and to delay the execution of step C for a safety time margin following the detection of an opening of the refrigerated compartment 11, for example of an opening of its door 20, and/or to inhibit the execution of step C if the second temperature setpoint value Tsp is not reached and possibly maintained for a predetermined period during a predefined time interval before a scheduled execution of step C. Even if the reference parameter is the temperature set-point Tsp, the refrigeration unit 14 can be configured to operate in such a way as to equal with its own superheating SH a superheating set-point SHsp where in the first step A, the superheating set-point SHsp can be set to a higher value and in step B the superheating set-point SHsp can be set to a lower value which is less than said upper value.
The variation of the superheating set-point SHsp between the upper value and the lower value can be carried out not in conjunction with the respective steps A and B, that is, the superheating set-point SHsp can be set to the higher value and changed to the lower value and vice versa independently from the execution of steps A and B.
In this way the cooling of the refrigerated compartment 11 can occur more quickly, thus being able to reduce the duration of step B to obtain the desired thermal flywheel effect to be exploited in step C.
The activation method according to the invention can provide a daytime operating mode and a night-time operating mode for the refrigeration apparatus 10, wherein step B and step C are performed exclusively in the night-time operating mode.
The night-time operating mode can provide for the lighting means - if foreseen - to be switched off and they can be programmed to be activated during the night-time hours or, depending on the specific installation of the refrigeration apparatus 10, during one or more periods of the day in which access by users to the refrigerated compartment 11, for example to introduce or remove products, is absent or infrequent with respect to the remainder of the day.
A switch between daytime operation mode and night-time operation mode can be set at pre-set times of the day, which can be adjusted if necessary.
The refrigeration apparatus 10 can comprise a sensor for detecting when the refrigerated compartment 11 is open and when it is closed and can be configured to automatically set times for switching between the daytime operating mode and the night-time operating mode based on opening data of the refrigerated compartment 11 recorded during operation of the refrigeration apparatus 10.
Step C can be performed at a predefined time of day that can possibly be adjusted.
The refrigeration apparatus 10 can be configured to set an execution time for step C according to parameters suitable for quantifying a transmission of heat between the cold exchanger 12 and the refrigerated compartment 11, to estimate the presence and/or a quantity of frost present on the cold exchanger 12.
The execution of step C can be programmed to be carried out several times a day or at intervals of several days where the frequency of execution of step C, and any step B that precedes it, can be automatically programmed based on operation data of the refrigeration apparatus 10 itself so as to minimise its energy consumption.
In general, step B can be performed at a predefined time of day that can be adjusted, or it can be performed at a time of day set automatically by the refrigeration apparatus 10, according to a time of execution of step C.
A difference between said first value and said second value of the temperature set-point Tsp and/or a difference between said upper value and said lower value of the superheating set-point SHsp can be set equal to a fixed value, possibly adjustable, or it can be automatically set by the refrigeration apparatus 10 according to the working conditions of the refrigeration apparatus 10 itself, and possibly according to an algorithm for optimising the operating efficiency of the refrigeration apparatus 10 or for minimising its energy consumption.
Clearly, part of the invention is a refrigeration apparatus 10 configured or programmed to implement an activation method as described above.
With particular reference to the diagram in Figure 2, this shows an example of a temporal trend, over 24 hours, of a day of operation of the refrigeration apparatus 10 wherein:

a possible trend of activation and deactivation of the lighting means can be represented by the line D;
a possible trend of a signal for detecting the opening and closing of the refrigerated compartment 11 can be exemplified by the line E;
the execution of defrosting step C can be exemplified by the line F;
the trend of the temperature set-point Tsp can be exemplified by the line G, wherein the temperature set-point Tsp is exemplified as variable between two values indicated as Tsp1 and Tsp2;
the trend of the superheating set-point SHsp can be exemplified by the line H, wherein the superheating set-point SHsp is exemplified as variable between two values indicated as SHsp 1 and SHsp 2.

The refrigeration apparatus 10 can for example consist of a refrigerator cabinet, a cabinet for frozen foods, a refrigerated display unit equipped with closing doors, such as a bottle cooler, or closing curtains, particularly usable in supermarkets or, in general, in food retail outlets.
The refrigeration apparatus 10 can also consist of a refrigerated automatic vending machine, for the distribution of food and/or drinks.
It can therefore be understood how a method of activating a refrigeration apparatus and a refrigeration apparatus which implements it, according to the invention, achieves the set aims and objectives in particular by allowing the energy consumption to be reduced whilst maintaining a temperature profile inside the refrigerated compartment that meets the relevant standard.
In particular, a method of activating a refrigeration apparatus and a refrigeration apparatus that implements it, according to the invention, allows a temperature to be maintained inside the refrigerated compartment which is on average higher than that which is maintained in traditional refrigeration apparatuses operating in same working conditions.
The invention thus conceived is susceptible to numerous modifications and variations, all of which fall within the scope of protection of the attached claims. Further, all details may be replaced by other technically equivalent elements. Where the operating and technical features mentioned are followed by signs or reference numbers, the signs or reference numbers have been used only with the aim of increasing the intelligibility of the description and claims themselves and, consequently, they do not constitute in any way a limitation to the interpretation of each element identified, purely by way of example, by the signs or reference numerals.

Claims

A method of activating a refrigeration apparatus (10) equipped with a refrigerated compartment (11) and a cold exchanger (12) and configured to absorb heat from the inside of said refrigerated compartment (11), by means of said cold exchanger (12), according to a reference parameter;
said method providing:
- a step A wherein said reference parameter is set to a first value;

- a step B wherein said reference parameter is set to a second value lower than said first value;

- a step C wherein said cold exchanger (12) is heated to defrost it;

wherein said step B precedes said step C and said second value of said reference parameter is set in such a way that during said step C an ambient temperature Ta detected in said refrigerated compartment (11) does not exceed an upper threshold value Tmax;

where said reference parameter is chosen from:
- a temperature set-point Tsp;

- a superheating set-point SHsp wherein said refrigeration apparatus (10) comprises a vapour compression refrigeration unit (14) which includes said cold exchanger (12) and is configured to operate in such a way as to equal said superheating set-point SHsp with its own superheating SH.
The method according to claim 1 wherein said step C begins at the end of said step B.
The method according to any one of the previous claims, wherein a target value To greater than said second value of said temperature set-point Tsp is set and said step C ends when a reference temperature reaches said target value To, wherein said reference temperature can be called ambient temperature Ta, or wherein said reference temperature is not higher than said target value To for a predefined target time interval or when an overall duration of said step C reaches a predefined maximum time.
The method according to the preceding claim, wherein said reference temperature is measured on or near the cold exchanger.
The method according to one of the preceding claims, wherein said second value of said reference parameter and/or a duration of said second step B are selected as a function of operating data of said refrigeration apparatus (10) and in such a way that during said step C said ambient temperature Ta reaches a maximum value which is less than said upper threshold value Tmax by a difference equal to a predefined safety deviation.
The method according to any one of the preceding claims, wherein said refrigeration apparatus (10) comprises a refrigeration unit (14) with vapour compression which comprises said cold exchanger (12) and is configured to operate in such a way as to equal with its own superheating SH a superheating set-point Shsp wherein, if said reference parameter is said temperature set-point Tsp, in said first step A said superheating set-point SHsp is set at a higher value and in said second step B said superheating set-point SHsp is set to a lower value which is less than said upper value.
The method according to any one of the preceding claims, wherein a daytime operation mode and a night-time operation mode are provided for said refrigeration apparatus (10) wherein said steps B and C are performed exclusively in said night-time operation mode.
Method according to the preceding claim, wherein a switch between said daytime operating mode and said night-time operating mode is set at pre-set times of the day, possibly adjustable, or said refrigerated compartment (11) can be opened and closed and said refrigeration apparatus (10) comprises a sensor to detect when said refrigerated compartment (11) is open and when it is closed and is configured to automatically set switching times between said daytime operating mode and said night-time operating mode as a function of the opening data of said refrigerated compartment (11) recorded during the operation of said refrigeration apparatus (10).
The method according to any one of the preceding claims, wherein said step C is performed at a predefined time of day, possibly adjustable, or said refrigeration apparatus (10) is configured to set an execution time for said step C according to parameters suitable for quantifying a transmission of heat between said cold exchanger (12) and said refrigerated compartment (11) to estimate a presence and/or a quantity of frost present on said cold exchanger (12).
The method according to the preceding claim, wherein said step B is carried out at a predefined time of the day, possibly adjustable, or is carried out at a time of day set automatically by said refrigeration apparatus (10) according to a time of execution of said step C.
The method according to any one of the preceding claims, wherein a difference between said first value and said second value, of said temperature set-point Tsp, and/or a difference between said upper value and said lower value of said superheating set-point SHsp, is set to a fixed value, possibly adjustable, or it is automatically set by said refrigeration apparatus (10) according to the working conditions of the refrigeration apparatus (10) and possibly according to an algorithm for optimizing the operating efficiency of the refrigeration apparatus (10).
A refrigeration apparatus (10) equipped with a refrigerated compartment (11) and with a cold exchanger (12) which is in thermal communication with said refrigerated compartment (11) to refrigerate it; said refrigeration apparatus (10) being configured to absorb heat from inside said refrigerated compartment (11), by means of said cold exchanger (12), as a function of a temperature set-point Tsp; said refrigeration apparatus (10) being configured or programmed to implement an actuation method according to any one of the preceding claims.