DE102005044029B3 - Heat pump for heating water for heating purposes comprises a coolant circuit operated in the supercritical region and having a de-super heater, a vaporizer, a compressor and a throttle valve and a control unit - Google Patents

Abstract

Heat pump comprises a coolant circuit operated in the supercritical region and having a de-super heater (E), a vaporizer (V), a compressor (K) and a throttle valve (DO) and a control unit (R) for controlling the throttle valve depending on the pressure on the high pressure side of the coolant circuit. Preferred Features: The control unit controls the throttle valve when the coolant is in the coolant circuit outside of the permission super heating. The coolant circuit is formed as a carbon dioxide coolant circuit. A pressure sensor is arranged in the coolant circuit to measure the high pressure.

Description

The present application relates to a heat pump. Heat pumps for heating heating water have been produced for years and marketed accordingly. The provision of heat to heat pumps is done by the condensation of refrigerant under high pressure and thus at a high temperature, while the heat is delivered to a heat transfer medium such as heating water. In the case of refrigerants which release their heat in the supercritical region, for example in the case of CO ₂ , a high-pressure control is usually used, since for each operating point an optimum high pressure is present which provides an optimum coefficient of performance. Here, a liquid separator is typically installed in the refrigerant circuit after the evaporator. The gaseous refrigerant is overheated after exiting the liquid separator before entering the compressor, such overheating not being controlled. With subcritical heat release of the refrigerant, the high pressure sets depending on the refrigerant and corresponding media, the size of the heat exchanger and the heat sink temperature. Typically, overheating control takes place to ensure optimum utilization of the evaporator.

DE 103 05 947 A1 shows an expansion device for an air conditioner in which a sliding seat valve is provided to control the high pressure level. This is to control or regulate the control of the throttling of the refrigerant on the high pressure side of the thermodynamic refrigeration process, so that the specific cooling capacity of the air conditioner can be varied. Thus, a release of heat in the supercritical region can be adjusted independently of the temperature.

DE 199 32 468 A1 shows a supercritical refrigerant circuit which is provided with a second pressure reducing means. Thus, the pressure from the refrigerant in a second evaporator is reduced, and the supercritical refrigerant cycle can regulate the pressure reduction valves without delay.

EP 1 355 207 A1 shows a method for operating a compression refrigeration system, wherein the opening degree of the expansion valve, ie the throttle point, and the power of the compressor are controlled as manipulated variables. The deviation of the controlled variables from their nominal value is at least approximately compensated by previously determined decoupling functions.

Out EP 604 417 B1 is a high-pressure control of a trans-critical refrigerant circuit known with a refrigerant receiver in the refrigerant circuit is known, is buffered with the refrigerant and the liquid phase of the refrigerant is deposited so as not to damage the compressor. The cycle is pressure controlled.

Out DE 100 61 545 A1 a method for refrigerant charge monitoring is known. During commissioning of filling quantity monitoring, the refrigerant superheating is detected at the evaporator and, in the event of excessive overheating, closed on an underfilling. At standstill, the pressure and temperature of the refrigerant are detected and closed on a faulty filling when the pressure is below a minimum pressure value or the temperature is above a maximum saturation temperature and the pressure outside a predetermined target pressure range.

From the EP 3 44 397 A2 is a climatic test chamber with a refrigerant circuit known. The circuit is controlled via a shut-off valve on the input side of the heat exchanger. The shut-off valve is a motor-driven, quasi-steady expansion valve. On the pressure side of the compressor, a condensation pressure sensor is arranged.

It Object of the present invention to provide a heat pump, in the it is ensured that only gaseous refrigerant enters the compressor enters and thus prevents liquid refrigerant from entering the compressor entry.

These Task is by a heat pump according to claim 1 solved.

Consequently becomes a heat pump with a refrigerant circuit provided, which in the supercritical Area is operated. In the refrigerant circuit is a desuperheater, an evaporator, a compressor and a throttle body intended. The heat pump further comprises a control unit for controlling the throttle body in dependence a pressure on the high pressure side of the refrigerant circuit, when a permissible overheating of the refrigerant is available. If the refrigerant in the refrigerant circuit outside permissible overheating is located, the control unit controls the throttle body in dependence a first temperature before the compressor.

According to one Aspect of the present invention controls the control unit Throttle body in dependence the actual overheating, if the refrigerant in the refrigerant circuit outside permissible overheating located.

According to another aspect of the present According to the invention, the refrigerant circuit is a transcritical operated circuit. In a further advantageous embodiment, CO _{2 is used} as a refrigerant.

Further Embodiments of the invention are the subject of the dependent claims.

following the invention is with reference to the accompanying drawings explained in more detail.

1 shows a schematic representation of a block diagram of a heat pump according to the present invention,

2 shows a schematic representation of the control of the heat pump of 1 , and

3 shows a lg p, h diagram of in 2 shown scheme.

1 shows a block diagram of a heat pump according to the first embodiment. The heat pump WP in this case has a desuperheater E, an evaporator V, a throttle body DO and a regulator R. Optionally, the heat pump may have a filter F between the throttle body DO and the desuperheater E. Between the evaporator V and the desuperheater E, a compressor or a compressor K is provided. Between the evaporator V and the throttle body DO, a first pressure p ₀₁ and a first temperature T ₁ are optionally detected. Between the evaporator V and the compressor K, a second pressure p ₀₂ and a second temperature T _{2 is} detected. Furthermore, behind the compressor K, a third pressure p _e1 and a third temperature T _v2 are detected. Between the desuperheater E and the throttle body DO, a fourth pressure p _e2 and a fourth temperature T _e2 are detected. The pressures and temperatures can be detected by means of suitable sensors. Between the compressor K and the throttle body DO, the high pressure side of the circuit is provided. The pressure behind the compressor K is for example 80 bar.

From the second temperature T ₀₂ and the second pressure p ₀₂ , overheating ΔT _U (ΔT _U = T ₀₂ -T (p ₀₂ )) can be calculated. Based on the measured second pressure p ₀₂ can be based on the in 3 shown diagram, a temperature to be determined, which corresponds to this pressure. Thus, the superheating ΔT _{Ü is determined} from the actual temperature T ₀₂ and the calculated temperature T (p ₀₂ ). To control this overheating, the cross section in the throttle body DO can be changed. Here, a change in the cross section of the throttle body DO causes a change in the refrigerant mass flow m _KM , which in turn can influence the overheating. With the change in the refrigerant mass flow m _KM , a change of the high pressure, ie the third and fourth pressure p _e1 , p _{e2 is} effected. A small change of the refrigerant mass flow m _KM causes a large change of the high pressure P _e2, that is, the third and fourth pressure, while only a slight change in the overheating .DELTA.T _Ü is effected. If a regulation of the overheating ΔT _Ü within a band is tolerated, the second pressure p _{02 can} be regulated exactly.

2 shows a control of the heat pump according to 1 , Here are three different areas shown. The first area B1 represents an area with too little overheating, while the second area B2 represents a permissible overheating, in which a high pressure control is possible. The third area B3 represents an area with too great an overheating. In this case, regulation of the high pressure is only possible in the second area B2. Within this range, a regulation of the high pressure takes place by changing the cross section in the throttle body DO. However, leaving this range of allowable overheating, such as when overheating becomes too low, introduces the risk of liquid refrigerant entering the compressor. To prevent this, the throttle body must be closed further to bring the refrigerant back into the desired overheating range. Thus, a control is outside the allowable overheating depending on the actual overheating.

If the refrigerant in the area of too much overheating enters, d. H. if the overheating the permissible Range in too high temperature differences has left working the chiller increasingly uneconomical. To prevent this, the regulation of overheating and the setting of the throttle body DO directly according to Temperature performed.

Thus, a regulation or control of in 1 Heat pump shown by a combination of an overheat control by a high pressure control, as long as a permissible overheating is present, while a temperature control is performed when the range of allowable overheating is left.

In the 1 Heat pump shown preferably has a filled with CO ₂ refrigerant circuit, which operates in the supercritical region. To control overheating, two different parameters are used. In the range of permissible overheating, high-pressure regulation takes place, which takes place, for example, on the basis of the pressure sensors p _e1 or p _e2 . When the high pressure increases, the throttle body DO is further closed, while the throttle body is opened further when the high pressure drops. This regulation or control takes place as long as the superheating ΔT _{Ü is} within the permissible range. Within the permissible range, regulation of the throttling element thus takes place as a function of the pressure, as long as certain temperature values are maintained.

3 shows a representation of the allowable overheating band in a lg p, h diagram. The range of the slight overheating here represents the range B1, the range of permissible overheating the range B2, and the range of excessive overheating represents the range B3. In the range B1, the throttle body DO is closed, and there is a control according to the Temperature. In the area B3, the overheating is too strong, and the throttle body DO is opened, that is, there is a control according to the temperature. In the area B2, however, the overheating is in the allowable range, and there is a regulation according to the high pressure.

Claims (6)

heat pump, With a refrigerant circuit, which in the supercritical area is operated, and which a desuperheater (E), an evaporator (V), a compressor (K) and a throttle body (DO), and one Control unit (R) for controlling the throttle body (DO) in dependence a first pressure on the high pressure side of the refrigerant circuit, if a permissible overheating of the refrigerant in the refrigerant circuit is present, and for controlling the throttle body (DO) depending a first temperature before the compressor (K) when the refrigerant in the refrigerant circuit outside permissible overheating located. heat pump according to claim 1, wherein the control unit (R) is designed to the throttle body (DO) depending the actual overheating to control when the refrigerant in the refrigerant circuit outside permissible overheating located. Heat pump according to one of claims 1 or 2, wherein the refrigerant circuit is configured as a CO ₂ -Kältemittelkreislauf. Heat pump according to one of the preceding claims, wherein in the refrigerant circuit at least one pressure sensor (p _e1 , p _e2 ) is provided for measuring a high pressure, wherein the control unit (R) is adapted to the throttle body (DO) as a function of the at least one High-pressure sensor (p _e1 , p _e2 ) to control measured high pressure when the refrigerant in the refrigerant circuit in a permissible overheating, with a regulation depending on the actual overheating takes place when the refrigerant in the refrigerant circuit is outside the allowable overheating. Refrigerant circulation, which in the supercritical area is operated with a desuperheater (E), an evaporator (V), a compressor (K) and a throttle body (DO), and one Control unit (R) for controlling the throttle body (DO) in dependence a first pressure on the high pressure side of the refrigerant circuit, if a permissible overheating of the refrigerant in the refrigerant circuit is present, and for controlling the throttle body (DO) depending a first temperature before the compressor (K) when the refrigerant in the refrigerant circuit outside permissible overheating located. Method of controlling a heat pump, one in supercritical Area operated refrigerant circuit with a desuperheater (E), an evaporator (V), a compressor (K) and a throttle body (DO), comprising the steps of: Taxes the throttle body (DO) depending a first pressure on the high pressure side of the refrigerant circuit, if the refrigerant in a permissible overheating located, and Control of the throttle body (DO) depending on a first temperature before the compressor (K) when the refrigerant in the refrigerant circuit outside permissible overheating located.