Patent Description:
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 <NUM> 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 -<NUM>, and falls below a lower thermal threshold, for example -<NUM>.

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.

The documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT> and <CIT> disclose respective methods of activating a refrigeration apparatus.

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.

With particular reference to <FIG>, the numeral <NUM> indicates in its entirety a refrigeration apparatus equipped with a refrigerated compartment <NUM> and a cold exchanger <NUM> which is in thermal communication with the refrigerated compartment <NUM> to refrigerate it.

The refrigeration apparatus <NUM> is configured to absorb heat from the inside of the refrigerated compartment <NUM>, by means of the cold exchanger <NUM>, 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 <NUM>, and depends on the relative intended use.

The refrigeration apparatus <NUM> can comprise a first temperature sensor <NUM> located inside the refrigerated compartment <NUM> and be configured or programmed to carry out a cooling action of the refrigerated compartment <NUM> designed to bring the ambient temperature Ta of the refrigerated compartment <NUM>, measured for example by the first temperature sensor <NUM>, to a value equal to the temperature set-point Tsp, except for any deviation.

The refrigeration apparatus <NUM> can comprise a refrigeration unit <NUM> with vapour compression which can use as a refrigerant fluid for example propane or, according to a different example, carbon dioxide.

The cold exchanger <NUM> can be included in the refrigeration unit <NUM>.

The latter can comprise in succession to the cold exchanger <NUM>, a compressor <NUM>, a hot exchanger <NUM> designed for dissipating the heat absorbed by the cold exchanger <NUM> and an expansion unit <NUM> connected in turn to the cold exchanger, to form a ring to actuate a refrigeration cycle.

The hot exchanger <NUM> can be connected to a water loop <NUM> 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 <NUM>.

The refrigeration unit apparatus <NUM> can comprise a controller, not shown, connected to the first temperature sensor <NUM> and programmed to activate the refrigeration unit <NUM> so as to absorb heat from the refrigerated compartment <NUM> to bring the ambient temperature Ta to tend towards or follow the value of the temperature set-point Tsp.

The refrigeration apparatus <NUM> can also comprise a second temperature sensor <NUM> located downstream of the cold exchanger <NUM> to detect a superheat temperature Tsh from which it is possible to calculate the superheat SH, known in the jargon as superheat, of the refrigerant fluid with respect to the evaporation temperature at the cold exchanger <NUM>.

In other words, the superheat SH is calculated as the difference between the superheat temperature Tsh and the evaporation temperature of the refrigerant fluid at the outlet of the cold exchanger, measured at the inlet of the compressor <NUM> 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 <NUM> so that the superheat SH tends towards or follows a superheat value of the set-point SHsp. The refrigerated compartment <NUM> can be opened and closed, for example by being provided with at least one door <NUM> designed to close or open an opening <NUM> of the refrigerated compartment <NUM> to allow a user to access the interior of the latter in order to take out/introduce products.

Furthermore, the refrigeration apparatus <NUM> can comprise lighting means, not illustrated, designed for illuminating the interior of the refrigerated compartment <NUM>, 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 -<NUM>, and falls at least once below a lower threshold Tmin, which can be equal to -<NUM>.

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 <NUM> 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 <NUM>, and the temperature set-point Tsp.

The value of the superheat set-point SHsp can be varied by the controller on the basis of an energy optimisation algorithm of the refrigeration unit <NUM>. In particular, the invention relates to a method of activating a refrigeration apparatus <NUM>, for example as described above, configured to absorb heat from the inside of the refrigerated compartment <NUM> by means of the cold exchanger <NUM>, as a function of a reference parameter, the method comprising:.

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 <NUM> does not exceed an upper threshold value Tmax. The reference parameter is the superheat set-point SHsp.

Thanks to the activation method according to the invention, in practice the temperature inside the refrigerated compartment <NUM> is lowered, varying the reference parameter, in such a way that the heating aimed at defrosting the cold exchanger <NUM> does not raise the temperature of the refrigerated compartment <NUM> 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 <NUM> 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 <NUM> 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 <NUM> in step C.

Clearly, the ambient temperature Ta can preferably mean the temperature of a product placed inside the refrigerated compartment <NUM> 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 - <NUM>, the second value equal to -<NUM> with the duration of step B for example equal to <NUM> hours with conditions external to the refrigeration apparatus <NUM> which can be, for example, <NUM> of ambient temperature with <NUM>% 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 superheat setpoint SHsp (or of the heat request) is made with respect to step A, which corresponds to a lowering of this setpoint.

According to preferred variants, in step B it is possible to foresee the variation of both the temperature setpoint Tsp and the superheat setpoint SHsp with respect to step A, differently from each other.

By appropriately adjusting, according to the operating parameters of the refrigeration apparatus, the temperature Tsp and superheat SHsp set points, it is possible to regulate 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 duration of each step.

Consequently, the method according to the invention, in addition to allowing the ambient temperature Ta detected in the refrigerated compartment <NUM> 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 and superheat 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 <NUM>.

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 <NUM> could be measured by a third temperature sensor <NUM> which can be positioned and/or configured to measure a temperature of the cold exchanger <NUM> or of an area of the refrigerated compartment <NUM> in the vicinity of the cold exchanger <NUM> 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 <NUM> 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 <NUM> 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 <NUM> and to delay the execution of step C for a safety time margin following the detection of an opening of the refrigerated compartment <NUM>, for example of an opening of its door <NUM>, and/or to inhibit the execution of step C if the second temperature set point value Tsp is not reached and possibly maintained for a predetermined period during a predefined time interval before a scheduled execution of step C.

The variation of the superheat 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 superheat 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 <NUM> 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 <NUM>, 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 nighttime hours or, depending on the specific installation of the refrigeration apparatus <NUM>, during one or more periods of the day in which access by users to the refrigerated compartment <NUM>, 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 <NUM> can comprise a sensor for detecting when the refrigerated compartment <NUM> 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 <NUM> recorded during operation of the refrigeration apparatus <NUM>.

Step C can be performed at a predefined time of day that can possibly be adjusted.

The refrigeration apparatus <NUM> 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 <NUM> and the refrigerated compartment <NUM>, to estimate the presence and/or a quantity of frost present on the cold exchanger <NUM>.

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 <NUM> 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 <NUM>, 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 superheat set-point SHsp can be set equal to a fixed value, possibly adjustable, or it can be automatically set by the refrigeration apparatus <NUM> according to the working conditions of the refrigeration apparatus <NUM> itself, and possibly according to an algorithm for optimising the operating efficiency of the refrigeration apparatus <NUM> or for minimising its energy consumption.

Clearly, part of the invention is a refrigeration apparatus <NUM> configured or programmed to implement an activation method as described above.

With particular reference to the diagram in <FIG>, this shows an example of a temporal trend, over <NUM> hours, of a day of operation of the refrigeration apparatus <NUM> wherein:.

The refrigeration apparatus <NUM> 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 <NUM> 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.

Claim 1:
Method of activating a refrigeration apparatus (<NUM>) equipped with a refrigerated compartment (<NUM>) and a cold exchanger (<NUM>) and configured to absorb heat from the inside of said refrigerated compartment (<NUM>), by means of said cold exchanger (<NUM>), 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 (<NUM>) 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 (<NUM>) does not exceed an upper threshold value Tmax;
characterized in that said reference parameter is
- a superheating set-point SHsp; wherein said refrigeration apparatus (<NUM>) comprises a vapour compression refrigeration unit (<NUM>) which includes said cold exchanger (<NUM>) and is configured to operate in such a way as to equal said superheating set-point SHsp with its own superheating SH.