EP0142663A2 - Defrost control method and device for heat pumps - Google Patents

Defrost control method and device for heat pumps Download PDF

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Publication number
EP0142663A2
EP0142663A2 EP84111031A EP84111031A EP0142663A2 EP 0142663 A2 EP0142663 A2 EP 0142663A2 EP 84111031 A EP84111031 A EP 84111031A EP 84111031 A EP84111031 A EP 84111031A EP 0142663 A2 EP0142663 A2 EP 0142663A2
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EP
European Patent Office
Prior art keywords
temperature
signal
temperature difference
evaporator
defrosting
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Granted
Application number
EP84111031A
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German (de)
French (fr)
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EP0142663B1 (en
EP0142663A3 (en
Inventor
Karl Ing. grad. Mötz
Friedrich Jobst
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MT Aerospace AG
Original Assignee
MAN Maschinenfabrik Augsburg Nuernberg AG
MAN Technologie AG
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Priority to AT84111031T priority Critical patent/ATE38555T1/en
Publication of EP0142663A2 publication Critical patent/EP0142663A2/en
Publication of EP0142663A3 publication Critical patent/EP0142663A3/en
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Publication of EP0142663B1 publication Critical patent/EP0142663B1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/002—Defroster control
    • F25D21/006—Defroster control with electronic control circuits

Definitions

  • the invention relates to a method for defrosting heat pumps, in which the defrosting process is controlled as a function of the temperature difference between the evaporator temperature and the ambient temperature of the evaporator.
  • the object of the invention is to develop a method in which the defrosting process takes place as close as possible to the defrosting time actually required.
  • the setpoint temperature difference is varied according to the ambient temperature and thus adapted to the evaporator behavior. This creates a reliable control in which unnecessary defrosting is prevented and, on the other hand, the defrosting is initiated in good time to ensure the economical operation of the heat pump.
  • the setpoint temperature difference is preferably changed continuously as a function of the outside temperature or the ambient temperature of the evaporator. However, it is also possible to use a step-by-step control of the target temperature difference.
  • the initiation of the defrosting process is blocked at evaporator temperatures above 0 ° C. This reliably prevents unnecessary defrosting if, at such evaporator temperatures, the actual temperature difference exceeds the target value calculated from the current ambient temperature.
  • the defrosting process is carried out as quickly as possible, so as to keep the switch-off pauses of the heat pump as short as possible.
  • selectable different defrost signals are emitted according to a predetermined criterion, with which different defrosting processes can be initiated.
  • the defrost signals can preferably be made dependent on the ambient or supply air temperature of the evaporator.
  • the criterion can be chosen such that at an ambient temperature above about 3 - C is a defrost initiated by ambient air 5 *
  • the invention extends to an apparatus for performing the method, with the features characterized in claim 6.
  • Fig. 1 the heating circuit of a compression heat pump 10 is shown, which from an evaporator 11 for receiving the energy Q from the ambient air 12, a compressor 13, which compresses the refrigerant vapor from the evaporator 11 and a condenser 14, to which one Consumer 15 is connected.
  • a defrost controller 16 which receives the signals from an evaporator temperature sensor 17 and an ambient temperature sensor 18 and outputs a signal to an actuator 19 when defrosting is required. With the actuator 19, the compressor 13 is switched off and thus the defrosting process is initiated.
  • the defrosting process can also be initiated in other ways, such as by reversing or diverting the refrigerant flow.
  • a comparator 21 which is subject to hysteresis, the actual temperature difference signal ⁇ T thus formed is compared with a target temperature difference signal AT which is generated by a target value generator 22 as a function of the ambient temperature. Is the measured temperature difference ⁇ T higher than the calculated target values! , then the comparator 21 outputs a signal 23 with which the actuator 19 is activated to initiate the defrosting process.
  • the defrosting process ends when the temperature difference ⁇ T has decreased accordingly.
  • This straight line is shown at 32 in FIG. 2.
  • FIG. 3 shows a block diagram of a second exemplary embodiment of a defrost controller 40.
  • the defrost regulator 4o is fed by a direct current source 41, the output voltage of which is stabilized and filtered in a reference voltage generator 42.
  • Defrost controller 40 is also connected to ambient temperature sensor 18 and evaporator temperature sensor 17.
  • the sensors 17 and 18 are fed by a voltage source 47, which transforms the reference voltage U into a predetermined sensor voltage U.
  • the temperature signals 43 and 45 generated by the sensors 17, 18 are adapted and standardized to the voltage level of the circuit in amplifiers 50 and 51, respectively.
  • the amplified voltage signals 52 and 53 are processed to form four command signals 54 to 57 in the defrost controller 40.
  • the setpoint temperature difference ⁇ T s is generated by a function generator 62, namely from the current ambient temperature signal 52 and an externally adjustable voltage value 63 from a potentiometer 64, which corresponds to the temperature difference adapted for the respective application.
  • the target temperature difference is formed as a linear function according to curve 32.
  • the slope K of this function is variable here.
  • the command signal 54 generated in this way gives the commands "switch on defrost" or "end defrost".
  • the switching process for the defrosting process is, however, output by means of two logic AND links 65 and 66 as a function of further signals, namely the command signals 55 to 57.
  • the command signals 55 indicate whether the evaporator temperature is greater or less than 0 ° C., and they are generated by comparing the evaporator temperature signal 53 with a voltage value U corresponding to 0 ° C. in a comparator 71, which is also subject to hysteresis.
  • the command signals 56 and 57 are external temperature-dependent signals, which are generated by comparing the ambient temperature signal 52 with a voltage U k associated with a corresponding temperature in a third comparator 72, which is subject to hysteresis, and are reversed by means of a non-element 73.
  • Different defrosting processes can be initiated with these outside temperature-dependent command signals 56 and 57, each of which is entered into one of the logic AND linkages 65 and 66, respectively.
  • the outside temperature T a and the evaporator temperature T k are measured continuously and the setpoint T s is calculated continuously.
  • the comparator 61 If the temperature difference AT between the measured values exceeds the target value ⁇ T s , the comparator 61 outputs the defrost signal 54, which is received in both links 65 and 66. However, the logic AND logic operation 65 will only output a switching signal 74 if it simultaneously receives the signal 55 T k ⁇ 0 ° C. and the signal 56 namely T a ⁇ T uk (for example T a less than 5'C). As a result, a first switching process is carried out, for example switching off the heat pump operation and switching on the hot gas defrost.
  • the second link 66 will output a switching signal 75 with which, for example, only the heat pump operation is switched off.
  • the defrost controller 40 can be designed, for example, as shown in FIG. 4, the voltage signals required in each case being determined using appropriately designed voltage dividers.
  • a relay 80 which can be controlled by the comparator 72 and which connects the line for the command signal 54 to the output 74 or 75 for the switching signals, depending on the ambient temperature, is provided for switching between the defrosting processes which can be initiated before the defrost signals 74 or 75.
  • the command signal 55 for the 0 ° C evaporator temperature changeover is linked to the setpoint signal ⁇ T s and compared in comparator 61 'to form the command signal 54' with the actual value ⁇ T.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Defrosting Systems (AREA)
  • Air Conditioning Control Device (AREA)

Abstract

1. A defrosting control method for heat pumps, a defrosting operation being controlled in dependence upon the temperature difference between the evaporator temperature and the ambient or supply air temperature of the evaporator, the actual temperature difference (DELTA T) being compared with a set-value temperature difference (DELTA Tm ) which varies in dependence upon the ambient or supply air temperature (Tm ), a defrosting signal being delivered on the basis of such comparison when the actual temperature difference exceeds the set-value temperature difference, characterised in that the continuously detected actual value signals of the ambient or supply air temperature (Tm ) and the evaporator temperature (Tk ) are supplied to a subtractor (60) determining the temperature difference DELTA T = Tm -Tk , the actual value signal (Tm ) is also supplied to a function former (62) which forms the set-value temperature difference (DELTA Tm ) from the actual-value signal (Tm ) and an adjusted temperature difference signal (Uv ), the actual-temperature difference signal (DELTA T) output by the subtractor (60) and the set-value temperature difference signal (DELTA Tm ) output by the function former (62) are supplied to a hysteretic comparator (61) which when DELTA T > DELTA Tm produces an output signal transmitted as first instruction signal (54) to a facility (65, 66) for triggering different defrosting signals, the actual value signal (Tm ) is also supplied to a hysteretic comparator (72) and compared therein with a signal (Uk ) corresponding to a fixed temperature above 0 degree C, more particularly 5 degrees C, and an output signal supplied as second instruction signal (56, 57 respectively) to the facility (65, 66) is produced, the actual value signal (Tk ) is supplied to a hysteretic comparator (71) and compared therein with a signal (Uo ) corresponding to a temperature of 0 degree C, and only when (Tk ) is below 0 degree C is an output signal produced which is supplied as third instruction signal (55) to the facility (65, 66) and when the first instruction signal (54) and the third instruction signal (55), the latter signalling a temperature Tk < 0 degree C, are present, the facility (65, 66) : a) if the second instruction signal (56, 57 respectively) signals a temperature Tm < Tuk , triggers a switching process whereby the heat pump drive is stopped and accelerated defrosting with heating gas is started or b) if the second instruction signal (56, 57 respectively) signals a temperature Tm > Tuk triggers a switching process whereby the heat pump drive is stopped and a normal defrosting process started.

Description

Die Erfindung bezieht sich auf ein Verfahren zur Abtauregelung von Wärmepumpen, bei dem der Abtauvorgang in Abhängigkeit von der Temperaturdifferenz zwischen der Verdampfertemperatur und der Umgebungstemperatur des Verdampfers gesteuert wird.The invention relates to a method for defrosting heat pumps, in which the defrosting process is controlled as a function of the temperature difference between the evaporator temperature and the ambient temperature of the evaporator.

Es ist bekannt, daß bei einer mit Umgebungsluft als Energiequelle arbeitenden Wärmepumpe die Luftfeuchtigkeit auf der Verdampferoberfläche kondensiert und ge- friert, wenn die Verdampfertemperatur unterhalb 0°C ist. Es ist daher erforderlich diese Vereisung zu überwachen und gegebenenfalls Abtaumaßnahmen einzuleiten.It is known that when operating with ambient air as an energy source heat pump, the humidity condensed on the evaporator surface and ge - freezes when the evaporator temperature below 0 ° C. It is therefore necessary to monitor this icing and to initiate defrosting measures if necessary.

Aus der US-PS 3,950,962 ist eine Abtauregelung bekannt, bei der zur Bestimmung des Abtaubeginns die Temperatur am Verdampfer und die der Zuluft zum Verdampfer gemessen und deren Differenz überwacht wird. Wird eine fest vorgegebene Temperaturdifferenz überschritten, so folgert man, daß dies infolge eines durch Vereisung der Oberflächen verringerten Warmeüberganges hervorgerufen wird. Es wird somit bei Oberschreitung des vorgegebenen Soll-Temperaturdifferenzwertes der Abtauvorgang eingeleitet.From US Pat. No. 3,950,962 a defrost control is known in which the temperature at the evaporator and that of the supply air to the evaporator are measured and their difference is monitored to determine the start of the defrost. If a predetermined temperature difference is exceeded, it is concluded that this is caused by a reduced heat transfer due to icing of the surfaces. The defrosting process is thus initiated if the specified target temperature difference value is exceeded.

Obwohl diese Methode bei der bekannnten Vorrichtung für eine Wärmepumpe vorgesehen ist, hat sie sich jedoch nur für die Anwendungsfälle bewährt, bei denen die Zulufttemperatur nahezu konstant bleibt, wie z.B. in Kühlräumen. Es hat sich nämlich gezeigt, daß bei der bekannten Abtaumethode bei höherer Umgebungstemperatur des Verdampfers unnötig oft abgetaut wird, während bei niedrigen Umgebungstemperaturen die Abtauung viel zu spät eingeleitet wird.Although this method is intended for the known device for a heat pump, it has only proven itself for the applications in which the supply air temperature remains almost constant, e.g. in cold rooms. It has been shown that, in the known defrosting method, defrosting takes place unnecessarily often at a higher ambient temperature of the evaporator, while defrosting is initiated far too late at low ambient temperatures.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zu entwickeln, bei dem der Abtauvorgang möglichst nahe zum tatsächlich erforderlichen Abtauzeitpunkt erfolgt.The object of the invention is to develop a method in which the defrosting process takes place as close as possible to the defrosting time actually required.

Die Aufgabe ist durch die im Anspruch 1 gekennzeichneten Maßnahmen gelöst.The object is achieved by the measures characterized in claim 1.

Dieser Lösung liegt die Erkenntnis zugrunde, daß bei Außenluft-Wärmepumpen eine Vereisung von der kältesten Außentemperatur bis zu Temperaturen oberhalb von 0°C auftreten kann. Aufgrund des etwa konstanten bzw. bei fallender Außentemperatur abnehmenden Volumenstromes des durch den Verdampfer fließenden Kältemittels tritt bei hoher Außen- bzw. Umgebungstemperatur bzw. Verdampfungstemperatur wegen der Dampfdichte eine hohe Kälteleistung auf, während die Kälteleistung bei fallender Umgebungstemperatur stark abfällt. Deshalb ist bei einem gegebenen Verdampfer schon im nicht vereisten Zustand die Temperaturdifferenz zwischen Zuluft und Verdampfung bei hohen Umgebungstemperaturen wesentlich höher (zweibis dreifach) als bei niedrigen.This solution is based on the knowledge that in the case of outside air heat pumps, icing from the coldest outside temperature to temperatures above 0 ° C can occur. Due to the approximately constant or decreasing volume flow of the refrigerant flowing through the evaporator when the outside temperature drops, a high cooling capacity occurs at a high outside or ambient temperature or evaporation temperature due to the vapor density, while the cooling capacity drops sharply when the ambient temperature falls. For a given evaporator, therefore, the temperature difference between the supply air and evaporation is much higher (two to three times) than at low temperatures, even at high ambient temperatures.

Bei dem erfindungsgemaßen Verfahren wird die Solltemperaturdifferenz entsprechend der Umgebungstemperatur variiert und damit an das Verdampferverhalten angepaßt. Hierdurch ist eine zuverlässige Regelung geschaffen, bei der unnötige Abtauvorgänge verhindert und andererseits zur Wahrung des wirtschaftlichen Betriebes der Wärmepumpe die Abtauvorgänge rechtzeitig eingeleitet werden. Die Solltemperaturdifferenz wird vorzugsweise kontinuierlich in Abhängigkeit von der Außentemperatur bzw. der Umgebungstemperatur des Verdampfers verändert. Es ist aber auch möglich, eine stufenweise Regelung der Solltemperaturdifferenz anzuwenden.In the method according to the invention, the setpoint temperature difference is varied according to the ambient temperature and thus adapted to the evaporator behavior. This creates a reliable control in which unnecessary defrosting is prevented and, on the other hand, the defrosting is initiated in good time to ensure the economical operation of the heat pump. The setpoint temperature difference is preferably changed continuously as a function of the outside temperature or the ambient temperature of the evaporator. However, it is also possible to use a step-by-step control of the target temperature difference.

Gemäß einer weiteren Ausgestaltung der Erfindung wird die Einleitung des Abtauvorganges bei Verdampfertemperaturen oberhalb 0°C gesperrt. Hierdurch wird ein unnötiges Abtauen zuverlässig verhindert, wenn bei derartigen Verdampfertemperaturen die Ist-Temperaturdifferenz den aus der momentanen Umgebungstemperatur errechneten Sollwert übersteigt.According to a further embodiment of the invention, the initiation of the defrosting process is blocked at evaporator temperatures above 0 ° C. This reliably prevents unnecessary defrosting if, at such evaporator temperatures, the actual temperature difference exceeds the target value calculated from the current ambient temperature.

Es ist ferner für den kontinuierlichen Betrieb einer Wärmepumpe wünschenswert, daß der Abtäuvorgang möglichst rasch durchgeführt wird, um somit die Abschaltpausen der Wärmepumpe möglichst klein zu halten. Hierzu wird vorgeschlagen, daß nach einem vorbestimmten Kriterium wählbare unterschiedliche Abtausignale abgegeben werden, mit denen unterschiedliche Abtauprozesse eingeleitet werden können. Die Abtausignale können vorzugsweise von der Umgebungs- bzw. Zulufttemperatur des Verdampfers abhängig gemacht werden. Gemäß einer weiteren Ausgestaltung der Erfindung kann das Kriterium so gewählt werden, daß bei einer Umgebungstemperatur oberhalb etwa 3 - 5*C eine Abtauung durch Umgebungsluft eingeleitet wird,It is also desirable for the continuous operation of a heat pump that the defrosting process is carried out as quickly as possible, so as to keep the switch-off pauses of the heat pump as short as possible. For this purpose, it is proposed that selectable different defrost signals are emitted according to a predetermined criterion, with which different defrosting processes can be initiated. The defrost signals can preferably be made dependent on the ambient or supply air temperature of the evaporator. According to a further embodiment of the invention, the criterion can be chosen such that at an ambient temperature above about 3 - C is a defrost initiated by ambient air 5 *

wobei lediglich der Kältemittelkreislauf der Wärmepumpe entweder abgeschaltet oder umgeleitet wird und die Verdampferlüfter weiter in Betrieb bleiben, während bei Temperaturen unterhalb 5°C ein Abtausignal abgegeben wird, mit dem Heißgas an die Verdampfer geleitet wird.only the refrigerant circuit of the heat pump is either switched off or diverted and the evaporator fans continue to operate, while at temperatures below 5 ° C a defrost signal is emitted with which the hot gas is directed to the evaporators.

Die Erfindung erstreckt sich auf eine Vorrichtung zur Durchführung des Verfahrens, mit den im Anspruch 6 gekennzeichneten Merkmalen.The invention extends to an apparatus for performing the method, with the features characterized in claim 6.

Das Verfahren und die Vorrichtung gemäß der Erfindung wird anhand der in den Zeichnungen schematisch dargestellten Ausführungsbeispielen näher erläutert.

  • Fig. 1 zeigt ein erstes Ausführungsbeispiel,
  • Fig. 2 ein Temperaturdiagramm,
  • Fig. 3 ein zweites Ausführungsbeispiel und
  • Fig. 4 eine detaillierte Schaltung zum Ausführungsbeispiel gemäß Fig. 3.
The method and the device according to the invention are explained in more detail with reference to the exemplary embodiments schematically illustrated in the drawings.
  • 1 shows a first embodiment,
  • 2 is a temperature diagram,
  • Fig. 3 shows a second embodiment and
  • 4 shows a detailed circuit for the exemplary embodiment according to FIG. 3.

In Fig. 1 ist der Heizkreis einer Kompressions-Wärmepumpe 10 dargestellt, die aus einem Verdampfer 11 zur Aufnahme der Energie Q aus der Umgebungsluft 12, einem Verdichter 13, der den Kältemitteldampf aus den Verdampfer 11 verdichtet und einem Verflüssiger 14 zuleitet, an dem ein Verbraucher 15 angeschlossen ist.In Fig. 1, the heating circuit of a compression heat pump 10 is shown, which from an evaporator 11 for receiving the energy Q from the ambient air 12, a compressor 13, which compresses the refrigerant vapor from the evaporator 11 and a condenser 14, to which one Consumer 15 is connected.

Es ist bekannt, daß ein der Außenluft 12 ausgesetzter Verdampfer aufgrund der Luftfeuchtigkeit an der Außenflache vereist, wenn die Verdampfertemperatur Tk bzw. die Temperatur der Verdampferoberfläche einen Wert unterhalb des Gefrierpunktes hat. Um einen Abtauvorgang bei Bedarf automatisch einzuleiten, ist bei dem Ausführungbeispiel gemäß Fig. 1 ein Abtauregler 16 vorgesehen, der die Signale eines Verdampfer-Temperaturfühlers 17 und eines Umgebungstemperaturfühlers 18 empfängt und bei Abtaubedarf ein Signal an ein Stellglied 19 ausgibt. Mit dem Stellglied 19 wird der Verdichter 13 ausgeschaltet und damit der Abtauvorgang eingeleitet. Der Abtauvorgang kann auch auf andere Weise eingeleitet werden, wie z.B. durch Umkehrung oder Umleitung des Kältemittelstromes.It is known that the outside air iced 12 exposed evaporator due to the humidity on the outer surface when the V erdampfertemperatur T k and the temperature of the evaporator surface has a value below the freezing point. In order to initiate a defrosting process automatically, if necessary, is the example 1, a defrost controller 16 is provided, which receives the signals from an evaporator temperature sensor 17 and an ambient temperature sensor 18 and outputs a signal to an actuator 19 when defrosting is required. With the actuator 19, the compressor 13 is switched off and thus the defrosting process is initiated. The defrosting process can also be initiated in other ways, such as by reversing or diverting the refrigerant flow.

Der Abtauregler 16 enthält einen Differenzbildner 20, mit dem die Temperatudifferenz ΔT=Ta-Tk gebildet wird, wobei Ta die Umgebungstemperatur ist. In einem hysteresebehafteten Komparator 21 wird das so gebildete Ist--Temperaturdifferenz-Signal ΔT mit einem Soll-Temperaturdifferenz-Signal A T verglichen, das von einem Sollwertbildner 22 in Abhängigkeit von der Umgebungstemperatur erzeugt wird. Ist die gemessene Temperaturdifferenz ΔT höher als der entsprechend errechnete Sollwerte! , dann gibt der Komparator 21 ein Signal 23 aus, mit dem zur Einleitung des Abtauvorganges das Stellglied 19 aktiviert wird. Bei Fortschreiten des Abtauvorganges wird der Abtauvorgang beendet, wenn die Temperaturdifferenz ΔT entsprechend abgesunken ist.The defrost controller 16 contains a difference former 20, with which the temperature difference ΔT = T a -T k is formed, where T a is the ambient temperature. In a comparator 21 which is subject to hysteresis, the actual temperature difference signal ΔT thus formed is compared with a target temperature difference signal AT which is generated by a target value generator 22 as a function of the ambient temperature. Is the measured temperature difference ΔT higher than the calculated target values! , then the comparator 21 outputs a signal 23 with which the actuator 19 is activated to initiate the defrosting process. When the defrosting process continues, the defrosting process ends when the temperature difference ΔT has decreased accordingly.

Aufgrund von Messungen und Rechnungen konnte die Funktion ΔT=f(Ta) der Temperaturdifferenz zwischen Verdampfungs-und Außentemperatur in Abhängigkeit von der Außentemperatur ermittelt werden, die einen in Fig. 2 mit der Ziffer 30 gekennzeichneten Verlauf hat. Diese Funktion ΔT=f(Ta) kann in erster Näherung durch eine Gerade 31 a (ΔT'=kTa) ersetzt werden. Die Gerade 31 entspricht somit etwa der Funktion ΔT=f(Ta), wenn keine Vereisung am Verdampfer 11 stattfindet. Durch Bereifung des Verdampfers vergrößert sich jedoch die Temperaturdifferenz ΔT um einen Wert a, der in etwa auch linear mit der Umgebungstemperatur Ta ansteigt. Damit kann eine lineare Änderung des Sollwertes T mit der Außentemperatur Ta vorgesehen werden, die gegenüber der Geraden 31 um einen Temperaturdifferenzwert a verschoben ist und gegebenenfalls eine größere Steigerung hat. Diese Gerade ist mit Ziffer 32 in Fig. 2 dargestellt.On the basis of measurements and calculations, the function ΔT = f (T a ) of the temperature difference between the evaporation temperature and the outside temperature as a function of the outside temperature could be determined, which has a curve marked with the number 30 in FIG. 2. This function ΔT = f (T a ) can be replaced in a first approximation by a straight line 31 a (ΔT '= kT a ). The straight line 31 thus corresponds approximately to the function ΔT = f (T a ) if there is no icing on the evaporator 11. If the evaporator is fitted with tires, however, the temperature difference ΔT increases a value a which also increases approximately linearly with the ambient temperature T a . In this way, a linear change in the target value T with the outside temperature T a can be provided, which is shifted by a temperature difference value a with respect to the straight line 31 and may have a greater increase. This straight line is shown at 32 in FIG. 2.

In Fig. 3 ist ein Blockschaltbild eines zweiten Ausführungsbeispieles eines Abtaureglers 40 dargestellt. Der Abtauregler 4o wird von einer Gleichstromquelle 41 gespeist, deren Ausgangsspannung in einem Referenzspannungs-Erzeuger 42 stabilisiert und gefiltert wird. Ferner ist der Abtauregler 40 an den Umgebungstemperatur-Sensor 18 sowie den Verdampfertemperatur-Sensor 17 angeschlossen. Die Sensoren 17 und 18 werden von einer Spannungsquelle 47 gespeist, die die Referenzspannung U in eine vorbestimmte Sensorspannung U transformiert.FIG. 3 shows a block diagram of a second exemplary embodiment of a defrost controller 40. The defrost regulator 4o is fed by a direct current source 41, the output voltage of which is stabilized and filtered in a reference voltage generator 42. Defrost controller 40 is also connected to ambient temperature sensor 18 and evaporator temperature sensor 17. The sensors 17 and 18 are fed by a voltage source 47, which transforms the reference voltage U into a predetermined sensor voltage U.

Die von den Meßfühlern 17, 18 erzeugten Temperatursignale 43 und 45 werden jeweils in Verstärkern 50 bzw. 51 dem Spannungsniveau der Schaltung angepaßt und normiert. Die verstärkten Spannungssignale 52 und 53 werden zur Bildung von vier Kommandosignalen 54 bis 57 im Abtauregler 40 verareitet. Zum einen wird, wie in Beispiel gemäß Fig. 1, mit einem Differenzbildner 60 die Temperaturdifferenz ΔT=Ta-Tk gebildet, die zur Erzeugung des ersten Kommandosignales 54 mittels eines hysteresebehafteten Komparators 61 mit der Soll-Temperaturdifferenz ΔTs verglichen. Die Soll-Temperatur- differenzΔTs wird von einem Funktionsbildner 62 erzeugt und zwar aus dem momentanen Umgebungstemperatursignal 52 und einem extern einstellbaren Spannungswert 63 aus einem Potentiometer 64, der der für den jeweiligen Anwendungsfall angepaßten Temperaturrdifferenz entspricht.The temperature signals 43 and 45 generated by the sensors 17, 18 are adapted and standardized to the voltage level of the circuit in amplifiers 50 and 51, respectively. The amplified voltage signals 52 and 53 are processed to form four command signals 54 to 57 in the defrost controller 40. On the one hand, as in the example according to FIG. 1, the temperature difference ΔT = T a -T k is formed with a difference former 60, which is compared with the target temperature difference ΔT s to generate the first command signal 54 by means of a hysteresis comparator 61. The setpoint temperature difference ΔT s is generated by a function generator 62, namely from the current ambient temperature signal 52 and an externally adjustable voltage value 63 from a potentiometer 64, which corresponds to the temperature difference adapted for the respective application.

Die Soll-Temperaturdifferenz wird in erster Naherung als eine lineare Funktion gemäß Kurve 32 gebildet. Die Steigung K dieser Funktion ist hierbei variabel. Das so erzeugte Kommandosignal 54 gibt die Befehle "Abtauvorgang einschalten" bzw. "Abtauvorgang beenden".In a first approximation, the target temperature difference is formed as a linear function according to curve 32. The slope K of this function is variable here. The command signal 54 generated in this way gives the commands "switch on defrost" or "end defrost".

Der Schaltprozeß für den Abtauvorgang wird jedoch mittels zwei Logisch-UND-Verknüpfungen 65 und 66 in Abhängigkeit von weiteren Signalen, nämlich den Kommmandosignalen 55 bis 57 ausgegeben.The switching process for the defrosting process is, however, output by means of two logic AND links 65 and 66 as a function of further signals, namely the command signals 55 to 57.

Die Kommandosignale 55 geben an, ob die Verdampfertemperatur größer oder kleiner als 0°C ist, und sie werden durch Vergleich des Verdampfertemperatur-Signales 53 mit einer dem 0°C entsprechenden Spannungswert U in einem ebenfalls hysteresebehafteten Komparator 71 erzeugt.The command signals 55 indicate whether the evaporator temperature is greater or less than 0 ° C., and they are generated by comparing the evaporator temperature signal 53 with a voltage value U corresponding to 0 ° C. in a comparator 71, which is also subject to hysteresis.

Die Kommandosignale 56 und 57 sind äußentemperaturabhängige Signale, die durch den Vergleich des Umgebungstemperatursignales 52 mit einer einer entsprechenden Temperatur zugeordneten Spannung Uk in einem dritten hysteresebehafteten Komparator 72 erzeugt werden und mittels eines Nicht-Gliedes 73 gegeneinander umgekehrt werden. Mit diesen außentemperaturäbhängigen Kommandosignalen 56 und 57, die jeweils einer der Logisch-UND-Verknüpfung 65 bzw. 66 eingegeben werden, können unterschiedliche Abtauvorgänge eingleitet werden. So läßt sich beispielsweise bei unterschiedlichen Außentemperaturen entweder lediglich der Wärmepumpenbetrieb ausschalten und bei einer anderen Temperatur zusätzlich ein Heißluftgebläse einschalten. Für diesen Fall kann Uk für eine Außentemperatur Tuk=5°C entsprechend ausgelegt werden.The command signals 56 and 57 are external temperature-dependent signals, which are generated by comparing the ambient temperature signal 52 with a voltage U k associated with a corresponding temperature in a third comparator 72, which is subject to hysteresis, and are reversed by means of a non-element 73. Different defrosting processes can be initiated with these outside temperature-dependent command signals 56 and 57, each of which is entered into one of the logic AND linkages 65 and 66, respectively. For example, at different outside temperatures, either only the heat pump operation can be switched off and a hot air blower can also be switched on at a different temperature. In this case, U k can be designed accordingly for an outside temperature T uk = 5 ° C.

Die Außentemperatur Ta und die Verdampfertemperatur Tk werden kontinuierlich gemessen und der Sollwert Ts kontinuierlich berechnet.The outside temperature T a and the evaporator temperature T k are measured continuously and the setpoint T s is calculated continuously.

Obersteigt die Temperaturdifferenz AT zwischen den Meßwerten den SollwertΔTs so gibt der Komparator 61 das Abtausignal 54 ab, das in beiden Verknüpfungen 65 und 66 eingeht. Die Logisch-UND-Verknüfung 65 wird jedoch nur dann ein Schaltsignal 74 ausgeben, wenn sie gleichzeitig das Signal 55 Tk<0°C sowie das Signal 56 nämlich Ta<Tuk (beispielsweise Ta kleiner als 5'C) erhält. Hierdurch wird ein erster Schaltprozeß durchgeführt, z.B. Abschalten des Wärmepumpenbetriebes und Einschalten der Heißgasabtauung.If the temperature difference AT between the measured values exceeds the target value ΔT s , the comparator 61 outputs the defrost signal 54, which is received in both links 65 and 66. However, the logic AND logic operation 65 will only output a switching signal 74 if it simultaneously receives the signal 55 T k <0 ° C. and the signal 56 namely T a <T uk (for example T a less than 5'C). As a result, a first switching process is carried out, for example switching off the heat pump operation and switching on the hot gas defrost.

Ist hingegen die Außentemperatur Ta höher als der gegebene Wert Tuk so wird die zweite Verknüpfung 66 ein Schaltsignal 75 ausgeben, mit dem beispielsweise lediglich der Wärmepumpenbetrieb ausgeschaltet wird.If, on the other hand, the outside temperature T a is higher than the given value T uk , the second link 66 will output a switching signal 75 with which, for example, only the heat pump operation is switched off.

Wenn die Verdampfertemperatur den Gefrierpunkt überschreitet, dann besteht keine Gefahr einer Vereisung des Verdampfers 11. In diesem Fall werden keine Signale 55 ausgegeben, so daß die Verknüpfungen 65 und 66 nicht durchgeschaltet werden und ein Abtauvorgang unterbleibt, auch wenn die TemperaturdifferenzΔT größer ist alsΔTs.If the evaporator temperature exceeds the freezing point, there is no danger of icing of the evaporator 11. In this case, no signals 55 are output, so that the connections 65 and 66 are not switched through and defrosting does not take place, even if the temperature difference ΔT is greater than ΔT s .

Der Abtauregler 40 kann beispielsweise, wie in Fig. 4 dargestellt, ausgebildet werden, wobei mit entsprechend ausgelegten Spannungsteilern die jeweils erforderlichen Spannungssignale bestimmt werden. Für die Umschaltung zwischen den vor den Abtausignalen 74 oder 75 einleitbaren Abtauprozessen ist ein vom Komparator 72 ansteuerbares Relais 80 vorgesehen, der über einen Schalter 81 die Leitung für das Kommandosignal 54 je nach der Umgebungstemperatur an den Ausgang 74 oder 75 für die Schaltsignale anschließt.The defrost controller 40 can be designed, for example, as shown in FIG. 4, the voltage signals required in each case being determined using appropriately designed voltage dividers. A relay 80 which can be controlled by the comparator 72 and which connects the line for the command signal 54 to the output 74 or 75 for the switching signals, depending on the ambient temperature, is provided for switching between the defrosting processes which can be initiated before the defrost signals 74 or 75.

Das Kommandosignal 55 für die 0°C Verdampfertemperatur-Umschaltung wird mit dem Sollwert-Signal ΔTs verknüpft und im Komparator 61' zur Bildung des Kommandosignales 54' mit dem IstwertΔT verglichen.The command signal 55 for the 0 ° C evaporator temperature changeover is linked to the setpoint signal ΔT s and compared in comparator 61 'to form the command signal 54' with the actual value ΔT.

Claims (8)

1. Verfahren zur Abtauregelung von Wärmepumpen, bei dem der Abtauvorgang in Abhängigkeit der Temperaturdifferenz zwischen der Verdampfertemperatur und der Umgebungstemperatur bzw. Zulufttemperatur des Verdampfers gesteuert wird, dadurch gekennzeichnet, daß die Ist-Temperaturdifferenz (ΔT) mit einem Soll-Temperaturdifferenzwert (ΔTs) verglichen wird, der in Abhängigkeit der Umgebungstemperatur (Ta) und gegebenenfalls der Verdampfertemperatur (Tk) verändert wird, und daß aufgrund des Vergleiches ein Abtausignal abgegeben wird, wenn die Ist-Temperaturdifferenz die Soll-Temperaturdifferenz übersteigt.1. A method for defrosting heat pumps, in which the defrosting process is controlled as a function of the temperature difference between the evaporator temperature and the ambient temperature or supply air temperature of the evaporator, characterized in that the actual temperature difference (ΔT) with a target temperature difference value (ΔT s ) is compared, which is changed as a function of the ambient temperature (T a ) and possibly the evaporator temperature (T k ), and that, based on the comparison, a defrost signal is emitted if the actual temperature difference exceeds the target temperature difference. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß eine Einleitung des Abtauvorganges bei Verdampfertemperaturen oberhalb 0°C gesperrt wird.2. The method according to claim 1, characterized in that an initiation of the defrosting process at evaporator temperatures above 0 ° C is blocked. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß nach einem vorbestimmten Kriterium wählbare unterschiedliche Abtausignale (74, 75) abgegeben werden.3. The method according to claim 1 or 2, characterized in that selectable different defrost signals (74, 75) are emitted according to a predetermined criterion. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß die Abtausignale (74, 75) in Abhängigkeit der Umgebungstemperatur variiert werden.4. The method according to claim 3, characterized in that the defrost signals (74, 75) are varied depending on the ambient temperature. 5. Verfahren nach Anspruch 3 oder 4, dadurch gekennzeichnet, daß bei Umgebungstemperaturen unterhalb 3 - 5°C ein Abtausignal abgegeben wird, mit dem eine Heißgasabtauung eingeschaltet wird.5. The method according to claim 3 or 4, characterized in that at ambient temperatures below 3 - 5 ° C, a defrost signal is given, with which a hot gas defrost is switched on. 6. Vorrichtung zur Durchführung des Verfahrens gemäß Anspruch 1, mit einem Temperaturmeßfühler für die Verdampfertemperatur und einem Temperaturmeßfühler für die Umgebungsluft des Verdampfers, dadurch gekennzeichnet, daß ein mit den beiden Meßfühlern (17, 18) verbundener Differenzbildner (20, 60) und mit dem Umgebungsluft-Temperaturfühler (18) verbundener Sollwertbildner (22, 62) vorgesehen sind, deren Ausgänge an einem hysteresebehafteten Komparator (21, 61) angeschlossen sind, dessen Ausgang (23, 54) mit einem Stellglied (19) zur Einleitung des Abtauvorganges verbindbar ist.6. Apparatus for carrying out the method according to claim 1, with a temperature sensor for the evaporator temperature and a temperature sensor for the ambient air of the evaporator, characterized in that a difference former (20, 60) connected to the two sensors (17, 18) and with the Ambient air temperature sensor (18) connected setpoint generator (22, 62) are provided, the outputs of which are connected to a hysteresis comparator (21, 61), the output (23, 54) of which can be connected to an actuator (19) to initiate the defrosting process. 7. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, daß ein zweiter Komparator (71) vorgesehen ist, der das Signal (53) des Verdampfer-Temperaturfühlers (17) mit einem der Temperatur 0°C entsprechenden Signal (70) vergleicht, und daß eine Logisch-UND-Verknüpfung (65 bzw. 66) vorgesehen ist, die die Ausgangssignale der beiden Komparatoren (61, 71) empfängt, und bei logisch gleichen Komparatorsignalen (54, 55) ein Abtausignal (74, 75) abgibt.7. The device according to claim 6, characterized in that a second comparator (71) is provided, which compares the signal (53) of the evaporator temperature sensor (17) with a temperature (0 ° C) corresponding signal (70), and that one Logic-AND linkage (65 or 66) is provided, which receives the output signals of the two comparators (61, 71), and outputs a defrost signal (74, 75) in the case of logically identical comparator signals (54, 55). 8. Vorrichtung nach Anspruch 6 oder 7, dadurch gekennzeichnet, daß ein dritter Komparator (72) vorgesehen ist, der das Signal (52) des UmgebungsTemperaturfühlers (18) mit einem Signal (Uk) vergleicht, das einer konstanten Temperatur, insbesondere etwa 5°C entspricht.8. Apparatus according to claim 6 or 7, characterized in that a third comparator (72) is provided which compares the signal (52) of the ambient temperature sensor (18) with a signal (U k ) which is a constant temperature, in particular about 5 ° C corresponds.
EP84111031A 1983-09-20 1984-09-15 Defrost control method and device for heat pumps Expired EP0142663B1 (en)

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AT84111031T ATE38555T1 (en) 1983-09-20 1984-09-15 METHOD AND DEVICE FOR DEFROST CONTROL OF HEAT PUMPS.

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EP0164948A2 (en) * 1984-06-12 1985-12-18 York International Corporation Control system and method for defrosting the outdoor coil of a heat pump
DE3539817A1 (en) * 1985-11-09 1987-05-14 Licentia Gmbh Method for metrologically determining, displaying and/or evaluating the icing occurring on the cooling plates of an air cooler
EP0272196A2 (en) * 1986-12-17 1988-06-22 Carrier Corporation Outdoor ambient temperature controlled heat-pump system
EP0285690A1 (en) * 1987-04-08 1988-10-12 Viessmann Werke GmbH & Co. Process and apparatus for the temperature dependent defrosting of cooling plants according to demand
GB2340922A (en) * 1998-08-31 2000-03-01 Daewoo Electronics Co Ltd Refrigerator defrost controlling method
WO2001022014A1 (en) * 1999-09-24 2001-03-29 Arçelik A.S. Defrost control
EP1134519A2 (en) * 2000-03-15 2001-09-19 Carrier Corporation Method and system for defrost control on reversible heat pumps
WO2002035165A1 (en) * 2000-10-27 2002-05-02 BSH Bosch und Siemens Hausgeräte GmbH Refrigerating device with an automatic defrosting system
EP1591736A1 (en) * 2004-04-30 2005-11-02 Lg Electronics Inc. Defrosting method for an air conditioner
EP2717002A1 (en) * 2012-10-08 2014-04-09 Emerson Climate Technologies GmbH Method for determining thaw times
CN111076364A (en) * 2019-12-25 2020-04-28 珠海格力电器股份有限公司 Heat exchanger assembly, air conditioner and air conditioner control method
DE102020123960A1 (en) 2020-09-15 2022-03-17 Viessmann Werke Gmbh & Co Kg Method for operating a heat pump and heat pump

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US4882908A (en) * 1987-07-17 1989-11-28 Ranco Incorporated Demand defrost control method and apparatus
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Cited By (19)

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Publication number Priority date Publication date Assignee Title
EP0164948B1 (en) * 1984-06-12 1989-07-19 York International Corporation Control system and method for defrosting the outdoor coil of a heat pump
EP0164948A2 (en) * 1984-06-12 1985-12-18 York International Corporation Control system and method for defrosting the outdoor coil of a heat pump
DE3539817A1 (en) * 1985-11-09 1987-05-14 Licentia Gmbh Method for metrologically determining, displaying and/or evaluating the icing occurring on the cooling plates of an air cooler
EP0272196A2 (en) * 1986-12-17 1988-06-22 Carrier Corporation Outdoor ambient temperature controlled heat-pump system
EP0272196A3 (en) * 1986-12-17 1988-08-31 Carrier Corporation Outdoor ambient temperature determination outdoor ambient temperature determination
EP0285690A1 (en) * 1987-04-08 1988-10-12 Viessmann Werke GmbH & Co. Process and apparatus for the temperature dependent defrosting of cooling plants according to demand
GB2340922B (en) * 1998-08-31 2003-01-08 Daewoo Electronics Co Ltd Refrigerator defrost controlling method
GB2340922A (en) * 1998-08-31 2000-03-01 Daewoo Electronics Co Ltd Refrigerator defrost controlling method
WO2001022014A1 (en) * 1999-09-24 2001-03-29 Arçelik A.S. Defrost control
EP1134519A2 (en) * 2000-03-15 2001-09-19 Carrier Corporation Method and system for defrost control on reversible heat pumps
EP1134519A3 (en) * 2000-03-15 2002-04-10 Carrier Corporation Method and system for defrost control on reversible heat pumps
CN100340829C (en) * 2000-03-15 2007-10-03 开利公司 Method and system for control of defrosting reversible heat pump
WO2002035165A1 (en) * 2000-10-27 2002-05-02 BSH Bosch und Siemens Hausgeräte GmbH Refrigerating device with an automatic defrosting system
CN1471622B (en) * 2000-10-27 2010-05-26 Bsh博施及西门子家用器具有限公司 Refrigerating device with an automatic defrosting function
EP1591736A1 (en) * 2004-04-30 2005-11-02 Lg Electronics Inc. Defrosting method for an air conditioner
EP2717002A1 (en) * 2012-10-08 2014-04-09 Emerson Climate Technologies GmbH Method for determining thaw times
CN111076364A (en) * 2019-12-25 2020-04-28 珠海格力电器股份有限公司 Heat exchanger assembly, air conditioner and air conditioner control method
DE102020123960A1 (en) 2020-09-15 2022-03-17 Viessmann Werke Gmbh & Co Kg Method for operating a heat pump and heat pump
DE102020123960B4 (en) 2020-09-15 2023-07-27 Viessmann Climate Solutions Se Method for operating a heat pump and heat pump

Also Published As

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DE3475100D1 (en) 1988-12-15
DE3333907C2 (en) 1988-05-11
DE3333907A1 (en) 1985-04-04
EP0142663B1 (en) 1988-11-09
EP0142663A3 (en) 1985-07-03
ATE38555T1 (en) 1988-11-15

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