EP2366968A2 - Method and device for thawing an evaporator of a heat pump device - Google Patents

Abstract

The method involves determining and storing temperatures of air stream and coolant passing through an evaporator (16) by a temperature sensor (20) and an evaporator temperature sensor (18) at or directly after characteristic time point such as after completing a thawing process. Temperature difference of the temperatures of the air stream and the coolant is determined and stored, and the thawing process is triggered by a controller (21) when actual temperature difference and actual coolant temperature exceed a sum of the temperature difference and constants. An independent claim is also included for a device for thawing an evaporator comprising a determining unit and a memory unit for determining and storing temperatures of air stream and coolant passing through the evaporator at or directly after characteristic time point such as after completing a thawing process.

Description

The invention relates to a method for defrosting an evaporator according to claim 1, an apparatus for defrosting an evaporator according to claim 13 and a heat pump apparatus according to claim 14.

Evaporators, in particular of air-water heat pumps, must be defrosted after a certain period of operation due to frost formation during operation (heating and / or service water operation). The defrosting process can according to the prior art, periodically, after expiration of a time-out, upon reaching a certain air-side pressure loss due to icing (a differential pressure measurement), the achievement of a certain current consumption of a fan motor due to icing (for example, according to DE 311 08 50 A1 ), due to an icing due to changing optical signal (for example, according to DD 22 63 55 A1 ) or by reaching a temperature difference between an air intake temperature and a refrigerant temperature (either before or after the evaporator) in response to an outside temperature (for example, according to FIG DE 35 09 664 A1 ) to be activated.

A defrosting operation may, according to the prior art, by the passage of a time-out, the reaching of a refrigerant temperature (either before or after the evaporator; DE 35 09 664 A1 ) by obtaining a fin temperature at the lower end of fins of an evaporator installed at a horizontal angle with respect to the horizontal (as shown in FIG DE 35 09 664 A1 ) or by a due of molten ice changing optical signal (for example according to DD 22 63 55 A1 ) are disabled.

In general, to provide the defrost energy, the existing compressor or an electric heating element (for example mounted in the evaporator) is needed. When defrosting energy is provided by the compressor, defrosting is usually accomplished by process reversal or by so-called hot gas defrosting. Such defrosting is also referred to below as "active defrosting". In such Aktiv Abtauung comparatively much electrical energy is needed. Heat pumps are also known in the prior art which, as an alternative to an active defrost, defrost the evaporator as a function of the outside temperature with the aid of an air stream flowing through the evaporator (defrosting of nature, for example according to US Pat DE 10 2006 024 871 A1 ).

Overall, it is considered problematic in the prior art that the defrost of the evaporator is complicated and less efficient, in particular that the choice of the time of activation of the defrosting leads to a less efficient operation of a corresponding system.

It is an object of the present invention to propose a method and a device for defrosting an evaporator, wherein a comparatively efficient work should be made possible and in particular the choice of the time of activation of the defrosting process should be such that a comparatively high efficiency can be achieved.

This object is achieved by a method for defrosting an evaporator according to claim 1, an apparatus for defrosting an evaporator according to claim 13 and a heat pump apparatus according to claim 14.

In particular, the object is achieved by a method for defrosting an evaporator of a heat pump device, in particular an air-water heat pump device, wherein at or immediately after a characteristic time, in particular a termination of a defrosting, a temperature T _{L, 0} of the evaporator passing Air flow and a refrigerant temperature T _{K, 0 are} determined and stored, wherein a temperature difference .DELTA.T ₀ from the temperature T _{L, 0} of the evaporator passing air flow and the refrigerant temperature T _{K, 0} determined and stored, wherein a defrosting operation is initiated when a current temperature difference ΔT _act from the temperature T _{K, akt} the sum of the temperature difference .DELTA.T ₀ and a constant (A, B) exceeds.

An essential idea of the invention is that the defrosting process is only initiated when the following condition is met: ΔT _act ≥ ΔT ₀ + Y. Y is a constant and is also referred to below as A or B, depending on the context. Y is in particular independent of the outside temperature. The temperature difference ΔT ₀ (= T _{L, 0} -T _{K, 0} ) is independent at least from the current outside temperature. Thus, the temperature difference ΔT _act (= T _{L, 0} - T _{K, act} ) is independent of the current outside temperature. This has the consequence that the activation of the defrosting takes place at a time that is particularly favorable in terms of efficiency. In the prior art - as far as a temperature difference was determined at all - this was always dependent on the outside temperature with the result that the activation of the defrosting event possibly took place even if the outside temperature changed accordingly, without a defrost was really necessary. Conversely, in the prior art (due to a fluctuating outside temperature) there is the possibility that an activation, even if it would be useful or necessary, is omitted. A core idea of the invention thus already consists in the fact that the temperature difference is determined independently of the current outside temperature. The constant Y or A or B may, for example, be at least 1 K, preferably at least 2 K, more preferably at least 3 K, even more preferably at least 5 K, even more preferably 10K, even more preferably at least 20K.

A new determination of the temperature difference ΔT ₀ can be made after another (in particular after each further) successful defrost. However, such a determination can also be carried out after a certain number (possibly constant number) of defrosting operations. The above-defined condition for initiating the defrosting operation is generally not intended (but in particular) to exclude that defrosting is also initiated by other conditions. Furthermore, it is generally not (but in particular) excluded that a defrosting process is initiated only if another criterion or more criteria are met.

The fact that in the described method, the initiation of the defrost is independent of the outside temperature, it is ensured that the corresponding heat pump device is operated only (maximum) as long as it in terms of plant efficiency is favorable. In particular, the compressor run time between two regular defrosts is essentially neither too short nor too long. Furthermore, it can be ensured by the method that sufficient defrost energy is available in the case of an active defrost.

Preferably, during / immediately after switching off a compressor of the heat pump device and / or ending a heat request, for example by a heating and / or service water, the current temperature difference .DELTA.T _act determined, wherein a defrosting process is initiated when the current temperature difference .DELTA.T _act the sum from the temperature difference ΔT ₀ and the constant exceeds. The shutdown of a compressor or the termination of a heat request initiates a downtime, which can be "used" by the proposed determination of the current temperature difference ΔT _act, if necessary, to an efficient defrosting. The defrosting process thus takes place in particular when the heat pump device is basically required (or only to a small extent). According to a more general idea, "termination of a heat demand" can thus also be understood as a reduced heat requirement, which is characterized, for example, by a decrease of at least 50%, preferably at least 80%, more preferably at least 90%, compared with a previous heat requirement.

The defrosting operation may be carried out, at least in part, by an active defrosting operation (in particular by process reversal) and / or a hot gas defrosting operation, and / or a natural defrosting operation. Since a natural defrost only a fan (fan) is in operation, the cost of electrical energy in this defrosting method is much lower than in the Aktiv Abtauung.

Preferably, a defrosting operation, in particular a Naturabtauvorgang, preferably in a downtime (only) initiated when the original temperature T _{L, 0 of} the air flow and / or a current temperature T _{L / akt of} the air flow to be determined exceeds a predetermined value T _{L, before} ,

According to an independent aspect, the above object is achieved by a method for defrosting an evaporator of a heat pump device, in particular an air-water heat pump device, wherein a Naturabtauvorgang is initiated in a downtime when a current temperature to be determined T _{L, akt of} the air flow is a predetermined value T _{L, before} exceeds. The value T _{L, akt} can for example at least 1 ° C, preferably at least 2 ° C, more preferably at least 3 ° C, even more preferably at least 5 ° C, even more preferably at least 10 ° C, even more preferably at least 20 ° C.

With the method of natural defrosting (possibly in addition to a regular natural defrosting) in the downtime of the heat pump, the iced evaporator can be completely defrosted, or at least a partial defrosting can be achieved. By (partial) defrosting the iced evaporator (evaporator register) during downtime, the compressor run times between two "regular" defrosts can be increased, resulting in an increase in plant efficiency. The nature defrosting method has the further advantage that during the defrosting process no energy needs to be withdrawn from the heating system to which the heat pump supplies energy during a heating operation.

In a specific embodiment of the method, at least two different defrosting methods, such as, for example, active defrosting and natural defrosting, are used. As a further method, a natural defrost can be used during downtime. As a result, the method is relatively variable, which leads to an increase in efficiency.

Preferably, when the temperature T _L of the air stream passing through the evaporator is exceeded _, a natural defrosting takes place via a first predetermined threshold value T _{G, 1} and / or if the temperature T _L falls below one or more predetermined threshold values T _{G, 1,} an active defrost occurs. This ensures that the respective defrosting method (active defrosting or natural defrosting) takes place when suitable external conditions are present. In particular, it is exploited that natural defrosting is only favorable if the outside temperatures are not too low. Overall, this measure increases the efficiency of the process. The limit value T _{G, 1} may, for example, be at least 2 ° C., preferably at least 5 ° C., more preferably at least 10 ° C., even more preferably at least 15 ° C., even more preferably at least 20 ° C., even more preferably at least 25 ° C. ,

Preferably, a defrosting operation takes place, in particular a natural defrosting operation (only) when the temperature T _L remains below a second predetermined threshold value T _{G, 2} . Preferably, this predetermined threshold T _{G, 2 is} a temperature at which a Icing of the evaporator no longer takes place. This can avoid unnecessary defrosting, which increases the efficiency of the process. The limit value T _{G, 2} may, for example, be at least 5 ° C., preferably at least 8 ° C., more preferably at least 15 ° C., even more preferably at least 19 ° C., even more preferably at least 25 ° C., even more preferably at least 30 ° C. ,

In particular, a defrosting operation, in particular an active defrosting operation, upon reaching a certain refrigerant pipe temperature, in particular fin temperature, terminated and / or a defrosting, in particular a Naturabtauvorgang, by reaching a predetermined difference between the temperature T _{L of} the air flow and the refrigerant piping temperature, in particular fin temperature ends. This can increase efficiency.

In a further embodiment, a defrosting process, in particular a natural defrosting process, which is carried out in particular during a standstill period, can be ended by a heat request and / or a service water request. In particular, the natural defrosting operation may also be terminated prior to complete defrosting. This can improve the availability of heat and / or service water. Overall, this improves efficiency.

The defrosting process can be initiated immediately or delayed. "Immediate" in this context means that the occurrence of another condition (or other conditions) is not required before the defrosting process is initiated. Accordingly, "delayed" means that there must be other conditions, such as the passage of a certain time or the fulfillment of certain parameters.

Preferably, a buffer memory and a heating system is provided, wherein the defrosting process, in particular immediately (or immediately), is started when the buffer memory has reached a predetermined temperature. In an alternative embodiment, the heat pump after reaching the condition that the current temperature difference .DELTA.T _akt exceeds the sum of the temperature difference .DELTA.T ₀ and the constant, for a predetermined time (for example, at least 1 min., Preferably at least 10 min.) In one Heating mode operated. This can provide sufficient defrosting energy, which increases efficiency.

The above object is achieved independently by a device for defrosting an evaporator of a heat pump device, in particular an air-water heat pump device, preferably for carrying out the method according to one of the preceding claims, a determination unit and a storage unit is provided to / immediately after Characteristic time, in particular a termination of a defrosting, a temperature T _L , ₀ of the evaporator passing air flow and a refrigerant temperature T _K , ₀ to determine and store and by a temperature difference .DELTA.T ₀ from the temperature T _{L, 0} of the evaporator passing air flow and determine and store the refrigerant temperature T _{K, 0} , wherein a control unit is provided and configured to initiate a defrost operation when a current temperature difference ΔT _act from the temperature T _{L, 0} and a current refrigerant temperature T _{K, akt} the sum of the tem temperature difference ΔT ₀ and a constant (A, B) exceeds. With regard to the advantages, reference is made to the method described above.

The determination unit and / or the memory unit may be part of the control unit or integrated in it. The device may comprise temperature meters and other measuring devices, for example, to determine the temperatures T _{L, 0} , T _{K, 0} or T _{K, akt} . In the control unit programs can be stored for control. In the determination unit programs may be deposited for determination.

The control or determination unit can be designed such that during / immediately after switching off a compressor of the heat pump and / or the termination of a heat request, for example by a heater and / or service water, the current temperature difference .DELTA.T _{act is} determined, wherein a defrost is initiated when the current temperature difference .DELTA.T _akt exceeds the sum of the temperature difference .DELTA.T ₀ and a constant. An active defrosting device and / or a nature defrosting device may be provided. In particular, a device for process reversal and / or for hot gas defrosting can be provided.

The control or determination unit can / can be configured such that the defrosting process, in particular a Naturabtauvorgang, preferably in a downtime (only) is initiated when the original temperature T _{L, 0 of} the air flow and / or a current temperature to be determined T _{L, act of} the air flow exceeds a predetermined value T _{L, before} . At least two different defrosting devices can be used, such as an active defrosting device and a nature defrosting device, be used. The control or the determination unit can / can be designed such that when exceeding the temperature T _{L of} the air flow over a first, predetermined threshold T _{G, 1 is} a natural defrosting and / or at a temperature below a predetermined temperature T _L Limit value T _{G, 1} an active defrost, in particular via process reversal occurs. The control or determination unit may be designed such that a defrosting process, in particular a Naturabtauvorgang (only) takes place when the temperature T _L remains below a second predetermined threshold value T _{G, 2} .

At least one sensor may be provided for determining a temperature of a cooking medium, in particular a fin temperature, wherein the control or determination unit is / are such that a defrosting operation, in particular an active defrosting operation, is terminated upon reaching the predetermined refrigerant piping temperature, in particular the fin temperature, and / or a defrosting, in particular a Naturabtauvorgang, by reaching a predetermined temperature difference between the temperature T _{L of} the air flow and the refrigerant piping temperature, in particular fin temperature is terminated.

Preferably, detection means are provided for determining that a heat request and / or service water request has ended, wherein the control or determination unit is / are designed such that a defrosting process, in particular a natural defrosting operation, which is carried out during a standstill time, by a heat request and / or dhw request is terminated.

In a preferred embodiment, the device comprises a buffer memory and a heating system, wherein the control or determination unit is / are designed such that the defrosting process is initiated when the buffer memory has reached a predetermined temperature.

The device may also include a heating system independently of the provision of a buffer memory.

The above object is achieved by a heat pump device, in particular air-water heat pump device comprising a device for defrosting the evaporator of the type described above.

Further embodiments emerge from the subclaims. The invention will also be described in terms of further features and advantages based on embodiments, which are explained in more detail with reference to the drawings.

Fig. 1

eine schematische Darstellung des Verlaufes der aktuellen Temperaturdifferenz ΔT_akt und des COP in Abhängigkeit von der Zeit;

Fig. 2

eine schematische Darstellung einer Wärmepumpenvorrichtung; und

Fig. 3

ein Flussdiagramm zur Steuerung der Einleitung eines Abtauvorgangs.

Hereby show:

Fig. 1

a schematic representation of the course of the current temperature difference ΔT _act and the COP as a function of time;

Fig. 2

a schematic representation of a heat pump device; and

Fig. 3

a flow chart for controlling the initiation of a defrosting process.

In the following description, the same reference numerals are used for the same and like parts.

Fig. 1 shows the course of the current temperature difference ΔT _act and the COP (= Coefficient of Performance; The current temperature difference ΔT _act is formed from the temperature T _{L, 0} and a current refrigerant temperature (in the present case after the evaporator, suction gas temperature) T _{K, act} . The temperature T _{L, 0} is the temperature of an air flow passing through the evaporator (in the present case the outside temperature) at a starting time, which is defined in more detail by the arrow 10. In the concrete case, the characteristic time defined by the case 10 may correspond to the time of termination of a defrosting operation.

As Fig. 1 can be taken, the temperature of the refrigerant after completion of a defrosting process is almost constant for a while and then drops (due to icing of the evaporator).

After a time indicated by an arrow 11, the refrigerant temperature or the temperature difference .DELTA.T _{akt has reached} the sum of the temperature difference .DELTA.T ₀ and a constant Y. At or immediately after this time, a defrosting process is initiated.

Defrosting is thus initiated in particular if the temperature difference ΔT _akt during the runtime of the compressor results in a value which results from the sum of the temperature difference ΔT ₀ and a constant A. On the other hand, a defrosting process preferably initiated if the temperature difference .DELTA.T _nude compressor switched off ₀ to a value of a constant exceeds the temperature difference AT B and / or the outside temperature (or temperature of the evaporator passing air stream T _{L, 0)} is above a predetermined threshold. The constant B may have the same value as the constant A, but also be larger (for example at least 1 K, preferably at least 3 K) or preferably smaller (for example at least 1 K, preferably at least 3 K). By querying whether the stored value of the temperature difference ΔT _{0 is} exceeded by the value of the constant B at the beginning of a standstill time (ie after switching off the compressor), it can be ensured that a significant icing of the evaporator (or evaporator register) is present, which can justify the initiation of a defrosting operation, in particular by defrosting nature, during a standstill period. The so initiated defrosting, especially natural defrosting, can be stopped by renewed heat or hot water request, even if the defrosting process is not yet completed.

Fig. 2 shows a heat pump device comprising a refrigerant circuit 12, which is flowed through during operation of a refrigerant. The refrigerant circuit comprises a compressor 13, a condenser 14, an expansion valve 15 and an evaporator 16. At an evaporator outlet 17, an evaporator temperature sensor 18 is arranged to detect a temperature of the refrigerant at the evaporator outlet 17.

The evaporator 16 can be acted upon by a fan 19 with an air flow. The temperature of the airflow may be measured by a temperature sensor 20.

The measured values of the evaporator temperature sensor 18 and the temperature sensor 20 can be stored in a control unit 21 and processed.

A natural defrost can be done by means of the blower 19. For example, an active defrost may be (not in Fig. 2 shown) take place in that a circulation reversal is formed. The circulation reversal may, for example, be controlled by the control unit 21 and / or comprise a four-way valve.

Fig. 3 shows a flow chart for (preferably automatic) control of a defrosting operation. First, the condition of the compressor is detected. Is the compressor "On", it is next determined whether the current temperature difference ΔT _akt ≥ the sum of the original temperature difference .DELTA.T ₀ and the constant A is. If this is not the case, then no defrosting takes place. If this is the case, it is next determined whether the temperature of the air flow T _L passing through the evaporator is greater than a first threshold value T _{G, 1} . If this is not the case, then a Aktivabtauvorgang takes place. If this is the case, it is optionally checked whether the temperature of the air flow is greater than a second limit value T _{G, 2} . If this is not the case, then no defrosting takes place. If this is the case, then a Naturabtauvorgang takes place.

If it is determined that the compressor is "off" or if the heat pump is at a standstill, then it is determined whether the current temperature difference ΔT _{akt is} greater than the original temperature difference ΔT ₀ plus a constant B. If this is not the case, then no defrosting takes place; if this is the case, a natural defrosting process takes place if a third limit value T _{G, 3 is} exceeded. The limit value T _{G, 3} can be different or identical to the limit values T _{G, 1} or T _{G, 2} .

In particular, the comparison with the second threshold T _{G, 2} can be omitted. The values for the constants A and B may for example be at least 1 Kelvin, preferably at least 2 Kelvin, more preferably at least 3 Kelvin, even more preferably at least 5 Kelvin, even more preferably at least 10 Kelvin, even more preferably at least 20 Kelvin and / or for example at most 40 Kelvin, preferably at most 30 Kelvin, more preferably at most 20 Kelvin, even more preferably at most 10 Kelvin, even more preferably at most 5 Kelvin, even more preferably at most 3 Kelvin.

According to a general idea claimed independently, it may be decided, depending on the temperature T _L (or outside temperature), before initiating a defrosting operation, with which defrosting method (active or natural defrosting) the defrosting operation is to be performed. If the temperature T _L falls below a certain value, active defrosting takes place, for example via process reversal. If the outside temperature or the temperature T _L exceeds a certain value, defrosting takes place. From a certain outside temperature, defrosting is preferably no longer initiated, since at certain outside temperatures icing of the evaporator no longer has to be possible.

It should be noted at this point that all the above-described parts taken alone and in any combination, in particular the details shown in the drawings, are claimed as essential to the invention. Variations thereof are familiar to the person skilled in the art.

LIST OF REFERENCE NUMBERS

10

arrow

11

arrow

12

Refrigerant circulation

13

compressor

14

condenser

15

expansion valve

16

Evaporator

17

evaporator outlet

18

Evaporator temperature sensor

19

fan

20

temperature sensor

21

control unit

Claims (14)

Method for defrosting an evaporator (16) of a heat pump device, in particular an air-water heat pump device,
wherein a temperature T _{L, 0 of} an air flow passing through the evaporator (16) and a refrigerant temperature T _{K, 0 are} determined and stored at or immediately after a characteristic time, in particular a termination of a defrosting operation,
wherein a temperature difference ΔT ₀ from the temperature T _{L, 0} of the evaporator (16) passing air flow and the refrigerant temperature T _{K, 0 is} determined and stored, and
wherein a defrosting operation is initiated when a current temperature difference ΔT _act from the temperature T _{L, 0} and a current refrigerant temperature T _{K, akt} exceeds the sum of the temperature difference ΔT ₀ and a constant (Y, A, B). A method for defrosting an evaporator according to claim 1,
characterized in that
during or immediately after switching off a compressor (13) of the heat pump and / or the termination of a heat request, for example by a heater and / or service water, the current temperature difference .DELTA.T _{act is} determined, wherein a defrosting process is initiated when the current temperature difference ΔT _act exceeds the sum of the temperature difference ΔT ₀ and a constant (Y, A, B). A method for defrosting an evaporator according to one of claims 1 or 2,
characterized in that
the defrosting process takes place at least partly by an active defrosting process, in particular by process reversal and / or a hot gas defrosting process and / or a natural defrosting process. Method according to one of the preceding claims,
characterized in that
the defrosting process, in particular a Naturabtauvorgang, preferably in a downtime, is initiated when the original temperature T _{L, 0} and / or a current temperature to be determined T _{L, akt of} the air flow exceeds a predetermined value T _{L, before} . A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
at least two different defrosting methods, such as active defrosting and natural defrosting, are used. A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
upon exceeding the temperature T _{L of} the air flow over a first, predetermined limit value T _G, a natural defrosting takes place and / or if the temperature T _L falls below a predetermined threshold value T _G, an active defrost occurs, in particular via process reversal , A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
A defrosting operation, in particular a natural defrosting operation, takes place when the temperature T _L remains below a second predetermined threshold value T _{G, 2} . A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
a defrosting operation, in particular an active defrosting operation, upon reaching a predetermined refrigerant piping temperature, in particular fin temperature, is terminated and / or a defrosting operation, in particular a Naturabtauvorgang, by reaching a predetermined temperature difference between the temperature T _{L of} the air flow and the refrigerant piping temperature, in particular fin temperature is terminated. A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
a defrosting operation, in particular a natural defrosting operation, which is preferably carried out during a standstill time, is terminated by a heat request and / or service water request. A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
the defrosting process is initiated immediately or delayed if the current temperature difference ΔT _akt exceeds the sum of the temperature difference ΔT ₀ and the constants (Y, A, B). A method for defrosting an evaporator according to any one of the preceding claims,
characterized in that
a buffer memory and a heating system are provided, wherein the defrosting process is initiated immediately when the buffer memory has reached a predetermined temperature. A method for defrosting an evaporator (16) according to one of the preceding
Claims,
characterized in that
the heat pump device after reaching the condition that the current temperature difference ΔT _act the sum of the temperature difference .DELTA.T ₀ and the Constants (Y, A, B), is still operated for a predetermined time in a heating mode. Device for defrosting an evaporator (16) of a heat pump device, in particular an air-water heat pump device, preferably for carrying out the method according to one of the preceding claims,
characterized in that
a determination unit and a storage unit are designed and provided to determine and at or immediately after a characteristic time, in particular a termination of a defrosting operation, a temperature T _{L, 0 of} an air flow passing through the evaporator (16) and a refrigerant temperature T _{K, 0} and to determine and store a temperature difference ΔT ₀ from the temperature T _{L, 0} of the air flow passing through the evaporator (16) and the refrigerant temperature T _{K, 0}
wherein a control unit is provided and adapted to initiate a defrost operation, when a current temperature difference ΔT _act from the temperature T _{L, 0} and a current refrigerant temperature T _{K, akt} the sum of the temperature difference .DELTA.T ₀ and a constant (Y, A, B ) exceeds. Heat pump device, in particular an air-water heat pump device, comprising an apparatus according to claim 13, preferably for carrying out the method according to one of claims 1 to 12.

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