DE102004010066B4 - Defrosting procedure for a heat pump - Google Patents

Abstract

Method for defrosting an evaporator of a heat pump circuit, with defrosting by means of circuit reversal and the condenser threatens to freeze in reverse circuit operation, characterized in that if the condenser (2) is threatened with freezing, the heat pump circuit is switched from reverse cycle operation to heat pump operation and the evaporator (4) is switched over by a Bypass (7) hot gas is supplied.

Description

The invention relates to a method for defrosting an evaporator of a heat pump circuit, defrosting by means of circuit reversal and the risk of freezing of the condenser of the heat pump operation in circuit reversal operation.

In the DE 198 32 682 C2 describes a defrosting device for carrying out such a method. The defrosting device is equipped with a circulating refrigerant, with a refrigerant circuit reversing circuit and a first expansion valve in a heating circuit and a second expansion valve in a defrosting circuit. Defrosting is improved by the fact that a refrigerant collector is connected in front of the first expansion valve in the heating circuit.

In addition to this possibility of defrosting by reversing the circle, the DE 198 32 682 C2 also referred to the possibility of hot gas defrosting.

U.S. 6,013,294 shows a heat pump that implements both cycle reversal and defrosting by means of hot gas supply through a bypass for defrosting an evaporator, with the initially preferred defrosting using hot gas only being switched to cycle reversing mode if the defrosting using hot gas does not achieve the desired result.

The defrosting of air-charged, icy evaporators by means of reverse circuit is energetically more efficient than defrosting by means of hot gas, since with reverse circuit defrosting heat is used for defrosting that was generated with a coefficient of performance> 1. This heat is provided by water, for example in the case of an air / water heat pump. A critical condition arises when the water is cooled down to near freezing point during defrosting by reversing the circle and the condenser of the heat pump can then freeze. In order to avoid this, according to the prior art, defrosting is ended when this critical case occurs. This is unfavorable because it is not certain that the evaporator is actually completely defrosted when this condition occurs.

The object of the invention is to propose a method of the type mentioned at the beginning in which defrosting is energetically efficient and does not have to be ended prematurely.

According to the invention, the above object is achieved by the features of claim 1.

The possibilities of defrosting by reversing the cycle and hot gas are combined. Defrosting takes place primarily by reversing the circle. If there are operating states in reverse cycle mode in which the condenser threatens to freeze, then defrosting is continued by hot gas defrosting. Trouble-free and energetically efficient defrosting is therefore guaranteed.

In a preferred development of the invention, the refrigerant-side pressure or the water-side temperature is monitored in order to detect the impending freezing of the condenser.

Further advantageous configurations of the invention emerge from the subclaims and the following description of an exemplary embodiment. The figure shows an air / water heat pump schematically.

A compressor is located in a heat pump circuit (see figure) 1 , a liquefier 2 , two anti-parallel connected throttle organs 3 , 3 ' , an evaporator 4th with fan 5 and a 4-2-way valve 6th . From the outlet of the compressor 1 to the evaporator 4th performs a bypass 7th into which a solenoid valve 8th is switched. The condenser is in the heat pump circuit 2 a pressure switch 9 intended. In the water circuit of the condenser 2 temperature monitor 10 .

The compressor 1 is, for example, a scroll compressor, a single-stage or two-stage reciprocating compressor or a rotary piston compressor. As throttle organs 3 , 3 ' thermostatic or electronic expansion valves can be used. HFC refrigerants, hydrocarbons or CO ₂ , for example, are used as refrigerants.

• Ist der Verdampfer 4 nach einer gewissen Zeit des Wärmepumpenbetriebs vereist oder bereift, dann wird dies über an sich bekannte Mittel in üblicher Weise festgestellt. Durch Umschalten des 4-2-Wegeventils 6 wird der Kreislauf des Wärmepumpenkreises umgekehrt. Dadurch verflüssigt sich Kältemittel im Verdampfer 4 und verdampft im Verflüssiger 2. Der Verdampfer 4 taut dabei ab.

The function of the device described is essentially as follows:

• Is the vaporizer 4th If the heat pump has been in operation for a certain period of time, it is iced up or frosted, then this is determined in the usual way using means known per se. By switching the 4-2-way valve 6th the circuit of the heat pump circuit is reversed. This causes refrigerant to liquefy in the evaporator 4th and evaporates in the condenser 2 . The evaporator 4th defrosts.

Via the pressure switch 9 or the temperature monitor 10 is monitored when the water in the condenser 2 threatens to freeze. If the water is expected to freeze within a short period of time, the 4-2-way valve is operated by a control system (not shown) 6th switched back to heat pump operation and the solenoid valve 8th opens, causing the compressor 1 Hot gas through the bypass 7th directly into the evaporator 4th presses. This is now defrosted further without the condenser freezing 2 is to be feared.

Claims (8)

A method for defrosting an evaporator of a heat pump circuit, with defrosting by means of circuit reversal and the condenser threatening to freeze in reverse circuit operation, characterized in that if the condenser (2) is threatened with freezing, the heat pump circuit is switched from reverse circuit operation to heat pump operation and the evaporator (4) is switched over by a Bypass (7) hot gas is supplied. Procedure according to Claim 1 , characterized in that the refrigerant-side pressure is monitored to detect the threat of freezing of the condenser (2). Procedure according to Claim 2 , characterized in that the temperature of the heat transfer medium, in particular water, of the condenser (2) is monitored in order to detect the threat of freezing of the condenser (2). Method according to one of the preceding claims, characterized in that a solenoid valve (8) of the bypass (7) is switched to supply the hot gas to the evaporator (4). Method according to one of the preceding claims, characterized in that the heat pump circuit is that of an air / water heat pump. Method according to one of the preceding claims, characterized in that a scroll compressor, a single-stage or two-stage reciprocating piston compressor or a single-stage or two-stage rotary piston compressor is used as the compressor (1). Method according to one of the preceding claims, characterized in that a thermostatic or electronic expansion valve is used as the throttle element (3, 3 '). Method according to one of the preceding claims, characterized in that an HFC refrigerant or hydrocarbons or carbon dioxide are used as the refrigerant.

Images