RS60088B1 - Defrosting method and device for refrigerating or air conditioning apparatus - Google Patents

Description

DESCRIPTION

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a defrosting process and a device, especially for an air cooling and air conditioning apparatus.

[0002] As is known, the formation of frost or ice on the surfaces for heat exchange when they come into contact with moist air in air cooling and air conditioning devices, including heat pumps (air evaporators and air coolers) that work on the basis of single-phase and two-phase fluids, which will be briefly referred to as "evaporators" in the following text, causes a progressive deterioration of the characteristics of the said apparatus, with negative consequences on the energy performance of the systems in which the said apparatus is installed.

[0003] In order to limit the negative impact of frost or ice, the prior art provides for the implementation of defrosting procedures on different types of evaporators (electric, water, with hot gas and so on) to re-establish the operating conditions of a clean evaporator.

[0004] In such previous use, it is intended that the defrost operation cycles are performed at constant time intervals, determined by the system operator (for example, a defrost operation every 6 hours) regardless of the effective need to perform such a defrost operation, or after a predetermined number of hours of operation of the evaporator.

[0005] The execution of the work cycle of defrosting, if it is not really necessary, includes obvious disadvantages, both in terms of energy consumption (in addition to the loss of energy necessary for the execution of the defrosting procedure, it is also necessary to take into account the fact that a significant part of the thermal energy used for defrosting is emitted into the environment for cooling and, accordingly, must be removed with additional energy consumption), and in terms of cooling characteristics, because, as is obvious, during the work cycle of defrosting, no cooling power and, accordingly, it is necessary to increase it, the total cooling energy remains the same, the installed cooling power.

[0006] Significant energy disadvantages are also involved since the defrosting operation is performed with a delay compared to the optimal defrosting period, this causes the evaporator to work in poor operating conditions, which consequently worsens the COP (coefficient of performance, eng. COP - coefficient of performance) of the cooling/heat pump operating cycle.

[0007] In several approaches there have been attempts to provide an "intelligent" or smart defrosting device, i.e. a device intended to determine the optimal time for executing the defrosting operation, independent of the time elapsed since the previous defrosting operation cycle.

[0008] EP0147825A2 relates to a defrost control system for heat pump cooling. US3299237A describes a defrost control device. KR100685767B1 deals with a fan system and method for compensating for heat loss due to defrosting. J P2011247525A describes a cooling device.

[0009] The published paper "Effects of under-relaxation factors on turbulent flow simulations, R.M. Barron et al, Int. J. Numer. Meth. Fluids 2003", in Table I on page 927, provides a "range of safe and recommended values of under-relaxation factors" which are between 0 and 1.

[00010] The presented application refers to solving the previously mentioned problems by applying new solutions specifically intended to overcome the previously mentioned shortcomings.

DESCRIPTION OF THE INVENTION

[00011] Accordingly, the aim of the presented invention is to provide a defrosting procedure and a device that is adapted to perform the defrosting operation, always in the optimal defrosting time, while preventing the evaporator from operating in suboptimal operating conditions, that is, with a suboptimal COP of the cooling/heat pump operating cycle.

[00012] Within the previously mentioned purpose, the main objective of the presented invention is to provide such a procedure and device for defrosting that can be applied to any type of evaporator, regardless of the characteristics or power of the evaporator, the cooling liquid used and the operating conditions of the said evaporator, the number of compressors with which it is connected, the number of evaporators placed in parallel connection, and so on.

[00013] Another object of the present invention is to provide a method and apparatus of the type described above, as previously stated, allowing the user to optionally change the preset value of the defrost cycle time, based on the user's specific requirements.

[00014] Another object of the presented invention is to provide a method and a device of the type described above, as previously stated, adapted to detect and signal any operating errors, or stoppage conditions, for example due to damage or failure of one or more components of the defrosting device, for example the drive fans.

[00015] Another object of the present invention is to provide such a defrosting method and device which is designed to correctly detect and signal a possible lack of operation, for example due to damage or other malfunctions of one or more heating resistors.

[00016] Another object of the present invention is to provide such a defrosting procedure that can be performed with a small number of hardware operating means that are readily commercially available to ensure a very safe and reliable operation of a refrigeration device and/or the like.

[00017] Another object of the present invention is to provide such an intelligent defrosting device that requires almost no maintenance.

[00018] Another additional object of the present invention is to provide such an intelligent defrosting device that does not require any calibration by either the vaporizer manufacturer or the installation operator or the user.

[00019] In accordance with the presented invention, the aforementioned purpose and goals, as well as other goals that will become clearer in the following text, are achieved by a process and device for defrosting, especially for air cooling and air conditioning devices, in accordance with the attached patent claims.

BRIEF DESCRIPTION OF THE DRAFT PICTURES

[00020] Additional features and advantages of the method and device according to the presented invention will become clearer in the following text on the basis of a detailed explanation of the preferred embodiment that follows, which is illustrated, with the help of an illustrative but not limiting example, in the accompanying drawings, where:

Figure 1 shows a flowchart of the defrosting procedure in accordance with the presented invention;

Figures 2 and 2A show the air pressure reading means that form an integral part of the innovative device and are applied to a general refrigeration and/or air conditioning device in which a defrosting procedure must be performed periodically;

Figure 2B provides a schematic representation of the main hardware components of the innovative device;

Fig. 3 provides an additional schematic representation of a screened manometer assembly that is part of an intelligent defrosting device in accordance with the presented invention;

Figures 3A and 3B provide schematic views of the preferred location of the defrost end sensors, for example on a chiller.

DESCRIPTION OF PREFERRED EMBODIMENTS

[00021] With reference to figure 1, the following text will describe the main working steps of the innovative management procedure associated with the innovative defrosting device.

[00022] In accordance with the presented invention, the measurement by managing the logical means for selecting the time in which the work cycle of defrosting is started, represents the pressure difference between the environment to be cooled and that which is measured at the corresponding point of the evaporator.

[00023] For example, for an evaporator that includes a plurality of fans for suction/delivery of air, that parameter is the pressure existing in the plenum or the negative/positive pressure of the chamber located before/after the exchange heat battery, the pressure difference of which is measured by the corresponding pressure difference sensor.

[00024] In accordance with the presented invention, the value of the pressure difference measured by the corresponding pressure sensor is stored here at the moment when the fans of the cooling device are restarted after the operation cycle of defrosting, and a change of this signal occurs during the operation time (as ice or frost is formed, the pressure signal will increase due to the increased aerodynamic resistance that needs to be compensated by the air fans).

[00025] Referring again to Figure 1, in operation step SO the pressure difference is obtained with the battery in a clean state, while in operation step S1 the pressure difference is measured.

[00026] If the answer in step S1 is NO, the flow of the diagram goes to the time step of operation S2 (alarm state).

[00027] If the answer in operation step S1 is YES, then it is determined, in operation step S3, whether the pressure difference is greater than or equal to the pressure difference threshold.

[00028] If the answer is NO, the flow returns to operation step S1.

[00029] If the answer is YES, the flow goes to step S4, where the fans are put in the OFF state, while the defrost resistors are switched to the ON status or under power, and the compressor is switched to the OFF state.

[00030] As shown, in operation step S4, step S2 related to time operation (alarm condition) is also running.

[00031] From step S4, the flow goes to step S5, where the final defrosting temperature is measured.

[00032] From step S5 the flow passes, if the answer is NO, to the step of the defrosting period S6.

[00033] Conversely, if the answer is YES, the flow from step S5 passes to step S7, where it is determined whether the final defrosting temperature is greater than or equal to the set final defrosting temperature.

[00034] If the answer is NO, from step S7 the flow returns to step S5.

[00035] If the answer is YES, from step S7 the flow goes to step S'7, where the fans are in the ON state, the heating resistors are OFF, the compressor is ON, and the defrost time and the value of ΔPfsbrins are stored.

[00036] From operation step S'7, the flow passes to operation step S8.

[00037] In this step S8 it is determined whether the defrosting time differs from the target or desired defrosting time.

[00038] If the answer is YES, the flow goes to step S9, where the change in pressure difference ΔPsoglia is determined.

[00039] From step S9, the flow goes to step S3.

[00040] If the response in step S8 is NO, the flow returns to the pressure difference measurement step S1.

[00041] Therefore, from the foregoing description of Figure 1, it should be apparent that, advantageously, the pressure differential increase that activates the start of the defrost cycle is self-calibrating based on the following sequence of operations:

1. in the first operating cycle, it is assumed that the preset percentage increase of the value with the evaporator in a defrosted state (stored in the memory during the entire lifetime of the evaporator or until the moment when a new measurement is made) on the traditional preset value (for example 60% of the value if the apparatus is in a clean state) of the pressure difference determines the start of the first defrosting operation.

2. the time required to execute the defrosting process is measured.

In accordance with an additional aspect of the present invention, the end of the defrosting operation is determined when a fixed and preset temperature value is reached, measured by additional suitable temperature sensors arranged at a plurality of convenient places on the evaporator, for example at the bend of the evaporator circuit and on the upper part of the ribbed section on the distributor side and so on, as will be described in more detail below.

The attainment of the aforementioned temperature should be confirmed by all sensors, with the last sensor reaching that value determining the end of the defrost time.

3. The defrost time determined in the previous step, in paragraph 2, is compared to the preset value and, based on the "continuation" or tracking algorithm, the preset differential pressure value is changed, said continuation algorithm according to the present invention:

where is:

defrosting = removing ice or frost

k = under-relaxation factor

4. The start of the next defrost cycle is determined when a new increased pressure difference value is reached.

5. The defrosting time is then measured and, based on the continuation algorithm, a new pressure difference value is determined that determines the start of defrosting operations.

6. Then, operating steps 4 and 5 continue continuously throughout the entire life of the evaporator.

[00042] In accordance with an additional aspect of the presented invention, the intelligent defrosting device executes, under the control of the innovative procedure, a series of control operations, which are accompanied by alarm signals associated with the operation of the evaporator during the defrosting step, using the operating logic schedules described below.

[00043] In this connection, it is necessary to point out that all stated values and/or numerous parameters are only indicative, since their selection will depend on the specific application.

3'. Alarm operating logic

[00044] These logic means ensure the execution of a series of check operations, which are accompanied by alarm signals, which are related to the operating status of the evaporator during the defrosting step.

[00045] In particular, during such a defrosting step, the subsequent working status of the following components is monitored: a) air fans; b) electrical resistance of defrosting (or other defrosting devices); c) any irregular ice formations at the end of the defrosting operation.

[00046] Below are indicated, by way of example only, alarms that are preferably incorporated into the evaporator monitoring system:

ΔP> 0 during defrost operation (air fan is ON during defrost) Malfunction of NTC probe: because the difference between them exceeds 50°C

ΔP after the i-th defrost < ΔP with a clean battery x 0.80

ΔP after i-th defrost > ΔP with clean battery x 1.20

Resistance malfunction: defrost time > maximum time (eg 45 minutes) Fan malfunction: ΔP after i-th defrost = 0 (tolerance ± 3 Pa) and pressure sensor malfunction L>AP=0.

4'. Means of "security" logic

[00047] The safety logic means will be used in the case when ΔPsoglia> fan ΔPmax, i.e. when the threshold ΔP, which varies in the convergent cycle, exceeds the maximum value ΔP that can be achieved by the air fan connected to a given exchange battery.

[00048] In this case, the threshold value is never reached, and accordingly the defrost operation cannot be activated.

[00049] Another case in which the threshold ΔP cannot be reached is when an excessively high desired defrost time value is set.

[00050] In this case, the innovative procedure will consist of the steps:

Value storage No.10 ΔWritten x-th time (for example 60 seconds)

Performing the X1 average operation

Storage of the value of the next No. 10 ΔWrite every x-th time (for example 60 seconds).

Performing the X2average operation

COMPARISON OF TWO AVERAGE VALUES:

if X1<X2 negative steering (rising curve)

VARIABLE VALUE A=0

if X1>X2 is positive steering (downward curve)

VARIABLE VALUE A=1

Repeating previous operations No. 3 times

If No. 3 A of the next value reached is equal to 1, then check ΔPi:

if ΔPi/ΔPbattery pulita> 1.6, then perform the defrost operation and check the defrost time:

if Tsbrinam> TTarget, then reduce TTarget(for example -5 minutes)

if Tsbrinam≤ TTarget, then restart with basic logic

if ΔPi/ΔPbatteria pulita≤ 1.6 then restart with basic logic

If No. 3 A of the next value reached is not equal to 1, then continue working with the basic logic.

[00051] Referring to Figures 2, 2A and 2B, there is shown here a possible way of applying the intelligent defrosting device of the present invention to an apparatus, for example a refrigeration apparatus, which is generally indicated by the reference numeral 100.

[00052] Figures 2 and 2A, respectively, show two sides of the refrigeration apparatus, including the sensor means of the innovative device.

[00053] The previously shown schematic images are included here only to show a very simple and quick way of placing the aforementioned sensors and their reduced number, especially some differential pressure sensors and end of defrost sensors.

[00054] Referring to Figure 2B, the main hardware components of the smart defroster of the present invention are shown.

[00055] In Figure 2B, arrow A indicates air flow, dotted half-circle line 101 indicates fan coil assembly; letters T1, T2 and T3 indicate temperature sensors; 102 shows a device for measuring the pressure difference; 103 shows a pressure probe; 104 shows the control panel; arrow F1 indicates the power supply of the control panel 104; arrow F2 indicates the output drive signal; the mark T4 indicates an additional temperature sensor.

[00056] Figures 3 through 3B illustrate additional hardware components of an intelligent defrosting device in accordance with the present invention.

[00057] In particular, the main hardware component here is the screened pressure gauge assembly 105, which conveniently uses a membrane 106, for example consisting of commercially available GORE-TEX® material.

[00058] The pressure gauge assembly 105 additionally includes an anti-turbulence cover 107 .

[00059] Figures 3A and 3B provide a schematic representation of the end of defrost sensors which are generally designated by the reference letters T4, T1, T2, T3.

[00060] Figure 3B is a left front view of Figure 3A.

[00061] Figures 3A and 3B give a clear view of the possible positions of the end of defrost sensors T4, T1, T2, T3, which are located at the bending part of the cooling circuit, in the upper central position on the distributor side (0) and inside the ribbed section at the diagonal position T1, T2, T3.

[00062] Figures 3, 3A and 3B also clearly show that the defrosting device 100 of the present invention contains a small number of hardware components that, in addition to reducing the cost of the device, allow said device to be almost maintenance-free.

[00063] Based on the foregoing description, it should be obvious that the presented invention fully achieves its intended purpose and goals.

[00064] In fact, the invention provided an "intelligent" defrosting procedure and an "intelligent" defrosting device, which can always perform the defrosting operation at the optimal defrosting time, thus preventing the evaporator from operating in suboptimal operating conditions, ie. with sub-optimal coefficients of the cooling/heating pump cycle characteristics.

[00065] An additional advantage of the method and device according to the presented invention is that the intelligent defrosting device in question can be applied to any type of evaporator, regardless of their power or used coolant and operating conditions.

[00066] Another advantage of the present invention is that the operator can optionally change the preset value of the defrost time, based on the operator's requirements.

[00067] Since the invention has been described in relation to the currently preferred embodiment of the innovative method and device, it should be apparent that this invention is susceptible to modifications and variations, all of which fall within the scope of the invention.

[00068] For example, since the innovative method and device described here are used in air cooling and/or air conditioning devices, they can obviously be used in other devices for the formation of frost or ice, where the ice, for the sake of efficient and optimal operation of the device, must be quickly removed, for example devices that work on the basis of suction air or air supplied on the exchange battery, as well as for all types of air fans (either axial or centrifugal type, and so on).

[00069] Then, the purpose of the invention should be as defined by the claims that follow, rather than as previously described.

1

Claims (10)

PATENT CLAIMS 1. A method for controlling an intelligent defrosting device, in particular for refrigeration, air conditioners, heat pumps and evaporators, wherein said device is placed in a cooling environment, wherein said method comprises steps for measuring the pressure in said cooling environment; measuring the pressure at a preset point on the evaporator and selecting a time to start the defrost cycle, when the pressure difference between the pressure of said environment to be cooled, and when said preset point of said evaporator exceeds a preset pressure threshold, characterized in that said method comprises the step of initiating the start of the defrost cycle based on a self-calibrating increase in pressure difference in the following order of steps: a) assuming, in the first cycle, the set percentage increase in the value of the pressure difference with the evaporator in a defrosted state, whereby this specified value is retained in the memory during the entire lifetime of the apparatus, or until the time in which the new value is stored in the specified memory, to a preset traditional value of the pressure difference, for example 60%, determines the beginning of the specified first defrosting cycle; b) measuring the time required for the defrosting operation, whereby the end of said defrosting operation is determined when a preset value of the steady temperature is reached; c) comparing the defrost time determined in said step b) with the preset value, and modifying, based on the tracking algorithm, the preset pressure difference value, wherein said tracking algorithm is expressed as: where k = under-relaxation factor d) starting the next defrosting cycle when a new value of pressure difference increase is reached; e) measuring the defrosting time and determining, based on the specified monitoring algorithm, the new value of the pressure difference that determines the start of defrosting operations; f) repeating steps d) and e) throughout the entire working life of said evaporator. 2. The method of claim 1, wherein said pressure at said point of said evaporator, for said evaporator including a suction/supply fan (101), is the pressure existing in a pressurized/unpressurized plenum, before/after the exchange heat battery. 3. The method, in accordance with patent claim 1, characterized in that said method contains the step of measuring said pressure difference using a pressure difference sensor. 4. The method, in accordance with patent claim 1, characterized in that said method contains the steps of the method of measuring the value of the pressure difference measured by said sensor (102) for measuring the pressure difference at the moment when said fans are restarted after the end of the defrosting cycle and the signal variations that follow over time. 5. The method according to patent claim 1, characterized in that the specified preset traditional value basically corresponds to 60% of the value, in the case of a clean state of the apparatus, of the differential pressure that determines the beginning of the first defrosting cycle. 6. The method, in accordance with patent claim 1, characterized in that said fixed temperature value is preset and measured by temperature sensors (T1, T2, T3, T4) distributed in several places on the evaporator, where several points are preferably located at the bending point of the evaporator circuit, in the central/high position on the distribution side and in the ribbed compartment in a diagonal position. 7. The method, in accordance with patent claim 5, characterized in that the detection of reaching the specified temperature is carried out using all sensors, whereby the last sensor reaches the specified value that determines the end of defrosting. 8. An intelligent defrosting device is made to carry out the process according to patent claim 1, in particular for a refrigeration or air conditioning device, said device includes at least an evaporator, said defrosting device includes basic logic means operatively connected to alarm means and safety logic means, characterized in that said device additionally comprises a pressure difference sensor operatively connected to said device to trigger the basic logic means to initiate a defrost cycle of said apparatus, when the pressure difference between the pressure of the environment to be cooled and the pressure measured at set point of said vaporizer, exceeds a preset threshold, said device further comprising a control board (104) for performing said steps (a) to (f). 9. An intelligent defrosting device according to claim 8, characterized in that said means of safety logic are adapted to operate when the pressure difference threshold, which varies in the convergence cycle, exceeds the maximum value of the pressure difference that can be achieved by the fan connected to the preset exchange battery. 10. An intelligent defrosting device, in accordance with patent claim 8, characterized in that said device additionally comprises a screened pressure gauge assembly (105), including filter membrane means (106) and anti-turbulence cover means (107), and said sensors include pressure difference sensors (102) and end-of-defrost sensors which are preferably located on the cooling circuit curve; in a high central position on the distribution side and inside the ribbed section in a diagonal position. 1