DE3023769A1 - Heat pump changeover system for defrosting - opens valve parallel to expansion valve before operating changeover valve - Google Patents

Abstract

The changeover system is for a heat pump with evaporator, compressor, condenser, expansion valve and changeover valve. The latter converts the evaporator used when heating into a condenser and the condenser into an evaporator, being particularly for defrosting the evaporator. At a set time before operation of the changeover valve (5) a valve (11) connected in parallel with the expansion valve (12) is opened, this time being so calculated that the liquid refrigerating medium from the condenser (6) is transferred into the evaporator (1) under the effect of the pressure difference between the suction and discharge sides of the compressor (4). The changeover valve is operated when this action is complete.

Description

STIEBEL ELTRON GmbH & Co. Kü

6/20/1980 file

Procedure for switching a heat pump

The invention relates to a method for switching a heat pump with an evaporator, a compressor, a Condenser, an expansion valve and a reversing valve, after which the evaporator of the heating mode is switched over as a condenser and the condenser of the heating mode works as an evaporator, in particular for Defrosting the evaporator.

In the literature reference "Handbuch der Kältetechnik" ® there is a refrigerant switch valve of a heat pump described. The switching process of this reversing valve runs as a function of the pressure difference between the suction side and the pressure side of the compressor. at "soft" switching is possible with small differential pressures. At higher differential pressures, for example above 10 bar, such reversing valves switch almost suddenly. When switching over, steam can enter the suction

Springer Verlag 1969

Volume 6 / Part A, pages 509 and 510

130062/0300

line of the compressor flow because the pressure side of the refrigerant circuit practically suddenly becomes the suction side. This is what is in the condenser liquid refrigerant relaxes, so that a refrigerant vapor cloud arises that are not completely kept away from the compressor by a liquid separator can be. It thus gets into the compressor and can lead to damage there, which reduces the The life of the compressor motor.

The object of the invention is to propose a method of the type mentioned at the outset which reduces the risk is that liquid refrigerant gets into the compressor.

According to the invention, the above object is achieved in that a period of time (Urasehaltphase) before switching over the Reversing valve a valve connected in parallel to the expansion valve is opened and that the period of time is so is dimensioned that from the condenser liquid refrigerant under the pressure difference between the suction side and Pressure side of the compressor is conveyed into the evaporator, and that only then the reversing valve is actuated. This ensures that before the suction side of the compressor via the reversing valve to the condenser of the heating operation is connected, from which liquid refrigerant is pressed into the evaporator of the heating operation, which works as a condenser after switching the reversing valve. It can then be in the condenser after switching

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^f 3023768

of the reversing valve containing no liquid droplets There is a cloud of vapor that could get into the compressor. This is therefore before a liquid precipitate largely protected.

Another advantage of this process is that the liquefied material containing a certain amount of residual heat Refrigerant that is pressed from the condenser into the evaporator then defrosts in the evaporator favored.

It has been shown that a duration of the switching phase in the order of magnitude between 5 and 12 seconds is sufficient is.

In a preferred embodiment of the invention, there remains a further valve in series with the expansion valve opened during the switchover phase and is only closed afterwards.

In an embodiment of the invention, when the reversing valve is switched back to heating mode, the valve is initially closed and then the other valve is opened. Before switching on the heating again, drove, after the end of the defrosting process in the evaporator Any refrigerant present is extracted until the desired pressure is reached on the pressure side. Have more accurate measurements show that this intermediate phase is not necessary.

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Further refinements of the invention emerge from the following description of an exemplary embodiment. In the drawing show:

Figure 1 an air / water heat pump in heating mode, Figure 2 the heat pump during the switchover phase · Figure 3 the heat pump in defrost mode and

FIG. 4 shows the heat pump in an intermediate phase between defrosting and heating.

The heat pump has an evaporator 1 with a fan 2, a liquid separator 3 »a compressor 4, a reversing valve 5 and a condenser 6. Xn the condenser 6 is a coil of heat exchangers Useful water circuit with a flow line 7 and a return line 8 arranged «

A valve arrangement is provided between the condenser 6 and the evaporator 1. A check valve 10 is parallel to a throttle element 9. This parallel connection is in series with a further parallel connection of a solenoid valve 11 with a series connection of an expansion valve 12, a sight glass 13, a filter dryer Ik and another solenoid valve

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As usual, in heating mode (see Figure i), the refrigerant is evaporated in the evaporator 1 while absorbing heat and is sucked in via the liquid separator 3 by the compressor h and fed under pressure to the condenser 6 it liquefies. The liquefied refrigerant reaches the evaporator again via the check valve 10, the open solenoid valve 15 and the expansion valve 12, in which the pressure is reduced. The solenoid valve 11 is closed «

At low outside temperatures below + 7 C, frost can build up on the evaporator «This must then be defrosted. The level of frost on the evaporator can be determined with sensors. If the evaporator has to be defrosted, a switching phase (see FIG. 2) is first switched on before switching on the actual defrosting process (see FIG. 2) Non-return valve 10 pressed liquid refrigerant from the condenser 6 into the evaporator 1 «The pressure difference between the suction side of the compressor h and its pressure side is reduced« This is achieved after about 5 to 12 seconds «

The reversing valve 5 is then switched over (see FIG. 3) and the solenoid valve 15 is closed.

The suction side of the compressor k is only now connected to the condenser 6 via the liquid separator 3.

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Since when switching the reversing valve 5 at most one there is a small pressure difference between the suction side and the pressure side of the compressor 4 and the liquid Refrigerant is essentially removed from the condenser 6, there can be no refrigerant vapor cloud form that could get into the compressor 4. In defrosting operation, the compressor 4 sucks under the effect of the useful cycle in the condenser 6 into the gas phase evaporated refrigerant and conveys this with an increase in temperature in the evaporator 1, in which thereby the frosting is removed. A bypass 16 below of the evaporator 1 favors its defrosting. The defrosted water reaches a condensate drain pan 17. The refrigerant liquefies in the evaporator 1 and passes through the solenoid valve 11 and the throttle element back into the condenser 6.

After the defrosting process has been completed, the heat pump can be switched back to heating mode, for which purpose the Reversing valve 5 switched over, the solenoid valve 11 closed and the solenoid valve 15 is opened.

Before switching back to heating mode, only the reversing valve 5 can initially be switched over and that Solenoid valve 11 are closed, the solenoid valve 15 initially remaining closed (see FIG. 4). It is thus initially sucked out of the evaporator 1 via the liquid separator 3 refrigerant, wherein

in
the compressor 4 to the condenser 6 the desired

Working pressure builds up.

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Claims (3)

6/20/1980 claims ^f X, J Method for switching a heat pump with an evaporator, a compressor, a condenser, an expansion valve and a reversing valve, after which the heating mode evaporator works as a condenser and the heating mode condenser works as an evaporator, in particular for defrosting the evaporator characterized in that a period of time (Umsehaltphase) before switching the reversing valve (5) a valve (11) connected in parallel to the expansion valve (12) is opened and that the period of time is such that liquid refrigerant from the condenser (6) is below the pressure difference between Suction side and pressure side of the compressor (k) is conveyed into the evaporator (i) and that only then is the reversing valve (5) actuated. 2. The method according to claim 1, characterized in that that the time span is about 5 to 12 seconds. 3. The method according to claim 1 or 2, characterized in that one in series with the expansion valve (12) lying further valve (15) during the period (Switching phase) remains open and is then closed. k. The method of claim 3 _t characterized in that closed to the heating operation, the valve (11) first when shifting of the reversing valve (5) and then the further valve is opened (15). 130062/0300 3Q2376I 5 · Valve arrangement between the condenser and the evaporator for carrying out the method according to a of the preceding claims, characterized in that a parallel connection of a throttle member (9) for the defrosting operation and a check valve (1O) in series with a parallel connection of the valve (11) and a series connection of the expansion valve (12) and the further valve (15) is located.