ITMI20150564A1 - DEFROST PROCESS AND DEVICE, IN PARTICULAR FOR REFRIGERATION AND AIR CONDITIONING EQUIPMENT - Google Patents

Description

Description of the Patent for Industrial Invention entitled: "DEFROST PROCESS AND DEVICE, IN PARTICULAR FOR REFRIGERATION AND AIR CONDITIONING EQUIPMENT"

DESCRIPTION

The present invention relates to a defrosting process and device in particular for refrigeration and air conditioning appliances.

How ? known, the formation of frost on the heat exchange surfaces in contact with the humid air of appliances intended for refrigeration and air conditioning, including heat pumps (air-evaporators and air-coolers) with single-phase and two-phase fluids , later called for brevity? "evaporators", causes a progressive deterioration of the performance of the appliances themselves, with negative consequences on the energy performance of the systems in which the appliances are installed.

To limit the negative influence of frost,? it is customary to provide for different types of evaporator defrosting methods (electric, water, hot gas, etc.) with restoration of the operating conditions of the clean evaporator.

In current use? the defrost cycles are expected to take place at constant time intervals, which can be set by the operator (for example, a defrost every 6 hours) regardless of the actual need? to carry out this defrost, or after a predetermined number of evaporator operating hours.

Carrying out a defrosting cycle, without it being required, involves obvious penalties, both in terms of energy consumption (in addition to the waste of energy required by the defrost) it must be considered that a large part of the thermal energy used to defrost ends up in the environment. to be refrigerated and must therefore be removed, with further energy consumption, both in terms of refrigeration performance, since? obviously during the defrost cycle no cooling capacity is produced and, therefore, the installed cooling capacity must be increased for the same overall cooling energy.

Significant energy disadvantages are also had when defrosting occurs later than the optimal time, since? there? it forces the evaporator to operate in poor conditions, with consequent worse COP (performance coefficients) of the refrigeration / heat pump cycle.

There are several proposals for making an "intelligent" defroster, that is, a device capable of determining when? the optimal time to defrost, regardless of the time interval elapsed since the previous defrost cycle.

The present application forms part of this trend with innovative ideas which allow the previous drawbacks to be eliminated.

What? the task of the present invention? that of realizing a defrosting procedure and device capable of carrying out defrosting always at an optimal moment, preventing the evaporator from operating in non-optimal conditions, that is? with non-optimal performance coefficients of the refrigeration / heat pump cycle.

Within the scope of this task, a main object of the present invention? that of realizing a process and a defrosting device that can be applied to any type of evaporator, regardless of its potential, the refrigerant fluid used and the operating conditions in which it works, the number of compressors with which? interfaced, by the number of evaporators in parallel and so on? Street.

A further object of the present invention? that of providing a method and a device of the type indicated, allowing the user to vary the pre-set value of the time of the defrosting cycle according to the needs of the user himself.

A further object of the present invention? that of realizing a method and a device of the indicated type capable of determining and signaling any operating defects, or non-functioning, for example due to failures or malfunctions of one or more? components of the appliance to be defrosted, such as fans.

A further object of the present invention? that of realizing a process and a defroster device capable of determining and signaling any non-functioning, for example due to failures or other malfunctions of one or more? heating resistors.

A further object of the present invention? that of realizing a defrosting process that can be carried out with a reduced number of hardware means easily commercially available to ensure extremely safe and reliable operation of the refrigeration appliance and / or the like.

A further object of the present invention? to create an intelligent defroster device which does not require almost? maintenance.

Not the last object of the present invention? to create an intelligent defroster device that does not require any calibration n? by the evaporator manufacturer n? by the installer or user.

According to the present invention, the aforementioned aim and objects, as well as further objects, which will appear more clearly clear hereinafter, are achieved by a method and a defrosting device in particular for refrigeration and air conditioning appliances, according to the attached claims.

Additional characteristics and advantages of the process and of the device according to the present invention will be more apparent. evident hereinafter from the following detailed description of a preferred embodiment thereof, illustrated, by way of example but not of limitation, in the accompanying drawings, in which:

Figure 1 represents a flow chart of the defrosting process of the present invention;

Figures 2 and 2A show air pressure sensor means constituting an integral part of the inventive device and applied to a generic refrigeration / or air conditioning appliance whose defrosting must be periodically carried out;

Figure 2B? a general view illustrating the main hardware components of the inventive device;

figure 3? a schematic view illustrating a shielded pressure tap assembly included in the smart defroster device of the present invention;

Figures 3A and 3B schematically illustrate a preferred positioning of end defrost sensors, for example on a refrigeration appliance.

Doing now more? particularly with reference to Figure 1, the main steps of the inventive process controlling the related inventive defroster device will be illustrated.

According to the present invention, the measure that governs the logic for choosing the moment in which the defrost cycle begins? the pressure difference between the environment to be refrigerated and that measured in a suitable point of the evaporator.

For example, for an evaporator with suction / delivery fans? the pressure existing in the plenum or chamber in depression / pressure downstream / upstream of the heat exchange coil, what difference? measured by a special differential pressure sensor.

According to the invention, the value of the differential pressure measured by a special sensor is stored at the instant in which the fans of the chiller appliance are restarted after the end of the defrost cycle and the evolution of this signal is followed over time (as the of the frost the pressure signal increases due to the increased aerodynamic resistance that the fans must overcome).

Returning to Figure 1, in step SO the pressure difference is acquired with the battery clean, while in step S1 the pressure difference is measured.

If the answer to step S1? No, then the flow goes to step S2 of timed operation (alarm condition).

If the answer in step S1? S ?, then it is determined, in step S3, whether the pressure difference? greater than or equal to a threshold pressure difference.

If the answer? No, the flow returns to step S1.

If the answer? Yes, the flow goes to step S4, where the fans are placed in the OFF or switched off state, while the defrost heaters are placed in the ON state or switched on and the compressor? placed in the OFF state.

As can be seen, step S2 relating to timed operation (alarm condition) also flows into step S4.

From step S4 the flow goes to step S5, where the defrost end temperature measurement is carried out.

From step S5 the flow goes to, in the case of response No, to step S6 of timed defrost.

Conversely, if the answer? Yes, from step S5 the flow goes to step S7 where it is determined whether the defrost end temperature? higher than or equal to the set defrost end temperature.

If the answer? No, from step S7 the flow returns to step S5.

If the answer? s? from step S7 the flow goes to step S'7 in which the fans are ON, the heaters OFF, the compressor ON and in which the defrost time is stored? and is also stored

APfsbrin.

From step S'7 the flow goes to step S8.

In step S8, it is determined whether the defrost time? different from the Target or desired defrost time.

If the answer? Yes, the flow goes to program S9 where the variation of the pressure difference S9 is determined.

From step S9 the flow goes to step S3.

If the answer in step S8? No, the flow returns to pressure difference measurement step S1.

What? will you understand? from the previous description of Figure 1 that, advantageously, the increase of the differential pressure which activates the start of the defrost cycle? self-calibrated according to the following sequence:

1. at the first cycle a pre-assigned percentage increase is assumed in the value with the battery clean (remembered in memory for the entire life of the evaporator or until a new storage is made) on a pre-set conservative value (for example 60% of the value when the appliance is clean) of differential pressure which determines the start of the first defrost cycle.

2. measure the time required for the defrost operation.

According to a further peculiar aspect of the invention, the end of the defrosting operation? determined upon reaching a fixed and pre-set temperature value measured by additional special temperature sensors positioned in pi? suitable points of the evaporator, (for example on a curve of the evaporating circuit and on the upper part of the finned pack on the collector side, etc. as will be further described below).

Reaching this temperature will have to? be verified by all sensors, the last sensor reaching the value determining the end of the defrost.

3. The defrost time determined in the previous step of point 2 is compared with the pre-set value, and based on a "tracking" algorithm, the pre-assigned differential pressure value is changed. Which tracking algorithm?, according to the invention:

in which:

defrosting = defrosting

K = Under-relaxation factor

4. The start of the next defrost cycle? determined by the achievement of the new differential pressure increase value.

5. The defrost time is measured and the new differential pressure value is determined on the basis of the tracking algorithm, which determines the start of the defrosting operations.

6. Continue with phases 4 and 5 for the entire operating life of the evaporator.

According to a further aspect of the present invention, the intelligent defrosting device, controlled by the inventive method, carries out a series of controls followed by alarm signals on the operating status of the evaporator during the defrosting phase, using the logical operational configurations described below. .

In this regard, it must be borne in mind that all the values and / or numerical parameters mentioned are only indicative, since? their choice will depend? specific application.

3 '. Alarm intervention logic:

This logic provides for a series of checks, followed by alarm signals, on the operating status of the evaporator during the defrost phase.

During defrost, the operating status is monitored: a) of the fan; b) electric defrost heaters (or other defrost devices); c) of possible anomalous formation of frost at the end of defrosting.

Below are indicated, by way of example, the alarms preferably inserted in the system, to monitor the operation of the evaporator:

DP> 0 during defrost (fan ON during defrost)

NTC probe failure: when their difference exceeds 50 ° C

DP after i-th defrost <DP clean battery x 0.80

DP after i-th defrost> DP clean coil x 1, 20 Resistance failure: Defrost time> Maximum time (e.g. 45 min)

Fan Failure: DP after i-th defrost = 0 (tolerance? 3 Pa) (and Pressure Sensor Failure L> DP = 0.

4 '. "Security" logic

The safety logic intervenes when there is the case in which the Dpsoglia> Dp max fan), that is? when the threshold DP, which varies in the cici? convergence, exceeds the maximum DP value that can be reached by the fan coupled to a certain exchange coil.

In this case, the threshold value would never be reached, so defrosting will not be able to? never be activated.

Another case in which the threshold DP could be unattainable,? when a target value of the defrosting time is set too high.

In this case the inventive process includes the steps of:

Store value of n? 10 DPi every x time (e.g. 60s) Carry out the average X1

Store value of successive n? 10 DPi every x time (e.g. 60s) Carry out the average X2

COMPARE THE TWO AVERAGES:

if X1 <X2 negative control (rising curve)

VARIABLE VALUE A = 0

if X1> X2 positive control (descent curve)

VARIABLE VALUE A = 1

Repeat the previous operations for n? 3 times

If n? 3 successive values of A equal to 1, then check DPi:

if DPi / DP clean coil> 1, 6 then defrost and check the time:

if <T> defrost> <? > Target then reduce the target (e.g. -5 minutes)

if <T> defrost <<T> arget then restart with basic logic

if D Pi / D Pbatteria points <1, 6 then restart with basic logic

If you don't get n? 3 successive values of A equal to 1, then continue with basic logic.

Referring now to Figures 2, 2A and 2B therein? illustrated a possible modality? application of the intelligent defroster device of the present invention on an appliance, for example a refrigerator, generally indicated by the reference number 100.

Figures 2 and 2A respectively represent the two sides of the chiller appliance with the sensor means of the inventive device installed.

These figures, however schematic, have been accused simply to illustrate the simplicity? and speed? installation of these sensors and the reduced number of them, that is, in particular, some differential pressure sensors and end defrost sensors.

With reference to Figure 2B, it represents the main hardware components of the intelligent defroster device of the invention.

In this figure 2B, the arrow A indicates the air flow, the semicircular dashed line 101 indicates a fan-coil assembly; the letters T1, T2 and T3 indicate temperature sensors; 102 indicates a differential pressure meter; 103 indicates a pressure probe; 104 indicates a control panel; arrow F1 indicates the power supply of the control panel 104, arrow F2 indicates the output command signal; reference T4 indicates an additional temperature sensor.

Figures 3 to 3B illustrate further hardware components of the intelligent defroster device of the present invention.

Specifically, a major hardware component of it? a shielded pressure take-off assembly 105, advantageously using a membrane 106, for example constituted by the commercially available Goratex material.

The pressure take-off assembly 105 also includes an anti-turbulence cover 107.

Figures 3A and 3B schematically show end defrost sensors, generally indicated by the numbers T4, T1, T2, T3.

Figure 3B? a front left side view of figure 3A.

From Figures 3A and 3B? possible to note the possible positions of the end defrost sensors T4, T1, T2, T3 and what? on a curved portion of the refrigeration circuit, in a central high position on the collector side (0) and inside the bedded pack in a diagonal T1, T2, T3 position.

Also from Figures 3, 3A and 3B it is evident that the defroster device 100 of the present invention includes a reduced number of hardware components which, in addition to reducing the cost of the device itself, also make s? that it is almost? maintenance free.

From the above it can be seen that the present invention fully achieves the intended aim and objects.

In fact, the invention has provided an "intelligent" defrosting procedure and device capable of carrying out defrosting always in correspondence with an optimal defrosting moment. not to force the evaporator to operate in non-optimal conditions and what? with non-optimal coefficients of performance of the refrigeration / heat pump cycle.

A further advantage of the method and device of the present invention? that the intelligent defroster device can? be applied on any type of evaporator, regardless of its potential? o the refrigerant fluid used and the operating conditions in which it works.

Still a further advantage of the present invention? that the operator can? vary the pre-set value of the defrost cycle time as desired, according to your needs.

Bench? the present invention has been described with reference to a currently preferred embodiment of the inventive method and device, it must be borne in mind that the invention? susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

For example, bench? the inventive method and device have been described used in refrigeration / or air conditioning appliances, they can obviously also be used in other frost forming appliances which, for an efficient and optimal operation of the appliance itself, must be promptly eliminated, for example appliances with suction or delivery air on the exchange coil, as well as? for each type of fans (axial, centrifugal, etc.).

It is therefore intended that the inventive scope of the present invention is defined, rather than by the preceding description, by the following claims.

Claims (10)

R I V E N D I C A Z I O N I 1. Control process of an intelligent defroster device, in particular for refrigeration appliances, air conditioning, heat pumps and evaporators, said appliances being installed in an environment to be refrigerated, characterized by including the steps of measuring the pressure in said environment to be refrigerated; measure the pressure at a predetermined point of said evaporator, and choose the starting time of the defrosting cycle when the pressure difference between the pressure of said environment to be refrigerated and that at said predetermined point of said evaporator exceeds a predetermined pressure threshold . 2. Process according to claim 1, characterized by the fact that the pressure in said predetermined point of the evaporator, for a said evaporator with a fan in the suction delivery,? the pressure existing in the plenum in depression / pressure downstream / upstream of the heat exchange coil. 3. Method according to claim 1, characterized in that said pressure difference is measured by means of a differential pressure sensor. 4. Process according to any one of the preceding claims, characterized in that it comprises the steps of storing a differential pressure value measured by said differential pressure measurement sensor at the instant in which said fans are restarted after the end of a cycle of defrost and to follow the evolution of this signal over time. 5. Process according to any one of the preceding claims, characterized in that it includes the step of activating the start of the defrost cycle on the basis of a differential pressure increase self-calibrated by means of the following sequence of steps: a) assume, in correspondence with a first cycle, a pre-assigned percentage increase of the value with clean battery, said value being kept in the memory for the entire life of the operator or until a new memorization is performed, on a value pre-set conservative differential pressure, determining the start of said first frosting cycle; b) measuring the time necessary for the defrosting operation, the end of the defrosting operation being determined when a fixed pre-set temperature value is reached; c) compare the defrost time determined in said phase 2) with the pre-set value and modify, on the basis of a tracking algorithm? the pre-assigned differential pressure value, said tracking algorithm being expressed by: where k = under-relaxation factor; d) start a subsequent frost cycle when the new differential pressure increase value is reached; e) measuring the defrosting time and determining, on the basis of said tracking algorithm, a new differential pressure value which determines the start of the frosting operations; f) repeating said steps d) and e) for the entire operating life of said evaporator. 6. Process according to any one of the preceding claims, characterized in that said preset conservative value substantially corresponds to 60% of the value of the differential pressure when the appliance is clean, which determines the start of the first frosting cycle. 7. Process according to any one of the preceding claims, characterized in that said fixed temperature value? pre-set and measured by temperature sensors positioned at various points of the evaporator, said various points being preferably on a curve of an evaporation circuit, in a central / high position on the collector side and inside a bedded pack in diagonal position. 8. Process according to any one of the preceding claims, characterized in that detecting the reaching of said temperature? implemented by all sensors, the last sensor reaching said value determining the end of the defrost. 9. Intelligent defroster device, in particular for a refrigeration or air conditioning appliance, said appliance including at least one evaporator, said defroster device including basic logic means operatively connected to alarm intervention logic means, and to logic means of safety, further characterized in that it comprises differential pressure sensor means functionally connectable to said apparatus for driving said basic logic means for starting a frosting cycle of said apparatus when a pressure difference between the pressure of an environment to be refrigerated and the pressure measured at a given point of said evaporator exceeds a predetermined threshold. 10. Intelligent defroster device, according to the preceding claim, characterized in that said safety logic means are able to intervene when the threshold pressure difference, which varies in a convergence cycle, exceeds the maximum pressure difference value that can be reached by a fan coupled to a predetermined exchange battery. 1 1. Intelligent defroster device, according to claims 9 and 10, characterized in that it comprises a shielded pressure tapping assembly, including filter membrane means and anti-tubulence cover means, and in that the sensors include differential pressure and pressure sensors. end defrost which are preferably positioned on a curve of a refrigeration circuit; in a high central position on the collectors side and inside a packet laid in a diagonal position.