METHOD FOR OPERATING A HEAT GENERATOR

Abstract

A method for operating a heat generator (1, 12) comprises providing a set heat quantity Qsoll in a hydraulic circuit; acquiring a first actual temperature T1 of a heating circuit medium in the circuit; acquiring a second actual temperature T2 at a second time t2, determining a temperature rise T as a difference between the second actual temperature T2 and the first actual temperature T1; acquiring a heat quantity Qzu introduced into the hydraulic circuit; determining a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise T and the introduced heat quantity Qzu; and operating the heat generator (1, 12) as a function of the determined set temperature Tsoll.

Claims

1. A method for operating a heating system for heating and/or cooling a building with a heat pump which heats a fluid heating circuit medium which circulates in a hydraulic circuit, wherein the circuit has a load, a buffer and the heat pump which are connected to one another via lines, wherein the method comprises the following steps: providing a set heat quantity Qsoll in the hydraulic circuit; acquiring a first actual temperature T1 of the heating circuit medium at a first time t1; acquiring a second actual temperature T2 of the heating circuit medium at a second time t2 which lies after the first time t1 by a predefined time period t; determining a temperature rise T as a difference between the second actual temperature T2 and the first actual temperature T1; acquiring a heat quantity Qzu introduced into the hydraulic circuit by the heat pump during the time period t; determining a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise T and the introduced heat quantity Qzu; and operating the heat pump as a function of the determined set temperature Tsoll.

2. The method according to claim 1, wherein the actual temperature of the heating circuit medium is measured between the buffer and the load.

3. The method according to claim 1, wherein: the load is a refrigerant circuit of a heat pump; and the heating circuit medium flows through a heat exchanger of the heat pump in order to transfer heat to the refrigerant.

4. The method according to claim 3, further comprising: carrying out a charging operation of the buffer until a current actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll; and carrying out a defrosting operation for defrosting an evaporator of the heat pump.

5. The method according to claim 3, wherein the predefined set heat quantity Qsoll is determined as a function of an external temperature and a device type of the heat pump.

6. The method according to claim 1, wherein the heat pump is operated with maximum heating power until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll.

7. The method according to claim 6, further comprising: determining a heating power required to reach the set temperature Tsoll; and if the required heating power is greater than the maximum heating power of the heat pump, operating an additional heat generator for heating the heating circuit medium.

8. The method according to claim 1, further comprising: providing a minimum temperature Tmin for the heating circuit medium; and determining the set temperature Tsoll of the heating circuit medium as a function of the minimum temperature Tmin.

9. A heating system for heating and/or cooling a building, comprising: a hydraulic circuit with a load and a buffer which are connected to one another via lines, wherein a fluid heating circuit medium circulates in the hydraulic circuit; a heat pump which is arranged in the circuit and is configured to heat the heating circuit medium; a temperature sensor which is arranged in the hydraulic circuit and is configured to acquire an actual temperature of the heating circuit medium; and a control device for controlling the heat pump, wherein the control device is configured to: provide a set heat quantity Qsoll in the hydraulic circuit; acquire a first actual temperature T1 of the heating circuit medium at a first time t1; acquire a second actual temperature T2 of the heating circuit medium at a second time t2 which lies after the first time t1 by a predefined time period t; determine a temperature rise T as a difference between the second actual temperature T2 and the first actual temperature T1; acquire a heat quantity Qzu introduced into the hydraulic circuit by the heat pump during the time period t; determine a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise T and the introduced heat quantity Qzu; and operate the heat pump as a function of the determined set temperature Tsoll.

10. The heating system according to claim 9, wherein the temperature sensor is arranged between the buffer and the load.

11. The heating system according to claim 9, wherein: the load is a refrigerant circuit of a heat pump in the heating system; and the heating circuit medium flows through a heat exchanger of the heat pump in order to transfer heat to the refrigerant.

12. The heating system according to claim 11, wherein the control device is further configured to: carry out a charging operation of the buffer until a current actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll; and carry out a defrosting operation for defrosting an evaporator of the heat pump.

13. The heating system according to claim 11, further comprising an external temperature sensor for measuring an external temperature, wherein the control device is configured to determine the predefined set heat quantity Qsoll as a function of the external temperature and a device type of the heat pump.

14. The heating system according to claim 9, wherein the control device is configured to operate the heat pump with maximum heating power until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll.

15. The heating system according to claim 14, further comprising: an additional heat generator for heating the heating circuit medium, wherein the control device is further configured to: determine a heating power required to reach the set temperature Tsoll; and if the required heating power is greater than the maximum heating power of the heat pump, operate the additional heat generator for heating the heating circuit medium.

16. The heating system according to claim 9, wherein the control device is further configured to: provide a minimum temperature Tmin for the heating circuit medium; and determine the set temperature Tsoll of the heating circuit medium as a function of the minimum temperature Tmin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantageous refinements are described in more detail below on the basis of an exemplary embodiment which is illustrated in the drawings but to which the invention is not restricted.

[0045] In the drawings:

[0046] FIG. 1 illustrates a generic heat pump system.

[0047] FIG. 2 illustrates a heat pump system according to a first exemplary embodiment of the present invention.

[0048] FIG. 3 illustrates a heat pump system according to a second exemplary embodiment of the present invention.

[0049] FIG. 4 shows a diagram which describes a dependence of the defrost energy on the external temperature.

DETAILED DESCRIPTION OF THE INVENTION ON THE BASIS OF EXEMPLARY EMBODIMENTS

[0050] In the following description of a preferred embodiment of the present invention, identical reference signs denote identical or comparable components.

[0051] FIG. 2 illustrates an exemplary embodiment of a heating system 10 according to the invention for a building. The heating system 10 according to the invention is constructed in a similar manner to the known heat pump system 10 of FIG. 1. Identical reference signs denote identical or similar constituent parts here.

[0052] The heating system 10 of FIG. 2 comprises a heat pump 1 which is designed as a monoblock heat pump. The individual components of the heat pump 1 such as, for example, the evaporator 5, the refrigerant circuit and the heat exchanger 6 are arranged in the outdoor unit ODU of the heat pump 1 and are not shown in FIG. 2.

[0053] In contrast to the heat pump 1 of FIG. 1, in which the heat exchanger 6 is arranged in the indoor unit IDU, this component is located in the outdoor unit ODU in the case of the heat pump 1 of FIG. 2. Otherwise, the construction of the heating system 10 in FIG. 2 is substantially identical to FIG. 1.

[0054] The heating system 10 can be operated in particular in one of three operating modes. A first operating mode is the normal operation or heating operation, in which the heat pump 1 provides heat for the heat sink 2. A second operating mode is the buffer charging operation, in which the heat pump 1 provides heat for loading the buffer 3. A third operating mode is the defrosting operation, in which the heat pump 1 is operated in reverse operation for defrosting and absorbs the heat stored in the buffer 3.

[0055] According to a preferred embodiment, the charging of the buffer 3 can also be carried out in parallel with the heating operation. This can also be interpreted as a fourth operating mode, in which the heat pump 1 is preferably operated with maximum heating power.

[0056] In the case of typical arrangements of monoblock heat pumps outside buildings, the length of the feed line VL and the return line RL between the buffer 3 and the heat pump 1 can be approximately 2 meters to 25 meters, preferably approximately 6 meters to approximately 20 meters. It should be noted that the length of the lines is not shown true to scale in FIG. 2.

[0057] The capacity of the buffer 3, which preferably serves exclusively for storing heat for the defrosting process, is approximately 10 liters to approximately 20 liters. As a result of the total length of the lines between the buffer 3 and the heat exchanger 6 of the heat pump 1 of approximately 4 meters to approximately 50 meters, preferably of approximately 12 meters to approximately 40 meters, the thermal mass of the heating circuit medium located in the lines and the thermal mass of the lines and the internals themselves cannot be neglected compared with the volume of the buffer 3. In addition, the total thermal mass of the hydraulic circuit can also comprise heat losses which cannot be quantified precisely a priori.

[0058] In order to be able to carry out a defrosting process of the heat pump 1 as efficiently as possible, it is advantageous to know the set heat quantity Qsoll required for this purpose as precisely as possible. In addition, it is desirable to adjust the heat quantity introduced into the hydraulic circuit as precisely as possible to the set heat quantity Qsoll.

[0059] If the heating system 10 is operated in an operating state for defrosting the heat pump 1, firstly the hydraulic circuit including buffer 3 is loaded with the required set heat quantity Qsoll. For this purpose, in a first step, the heat sink 2 with the heating circuit 2.1 and the hot water store 2.2 can be separated from the hydraulic circuit via the valve 4.

[0060] In a next step, a first return line temperature T1 of the heating circuit medium is acquired at a first time t1. After a predefined time period t, a second return line temperature T2 of the heating circuit medium is acquired at a second time t2. The predefined time period t can be, for example, 60 to 600 seconds, preferably 60 to 180 seconds. Further preferably, the predefined time period t is approximately 120 seconds.

[0061] In order to acquire the return line temperatures, a return line temperature sensor 11 is arranged in the return line RL between the buffer 3 and the heat pump 1. In addition, further temperature sensors can be arranged in the heating system 10 (not shown), for example in the buffer 3 and/or in the feed line VL.

[0062] Subsequently, a temperature rise T is calculated as a difference between the second return line temperature T2 and the first return line temperature T1 via equation (1). A set temperature Tsoll of the heating circuit medium can then be calculated via equations (2) and (3).

[0063] Since the losses and the total volume of heating circuit medium in the hydraulic circuit can change, the set temperature Tsoll is preferably determined again before each defrosting operation or at the beginning of each loading operation of the buffer 3. In particular, the heat losses of the hydraulic circuit can change, for example, as a function of the external temperature, with the result that the total thermal mass can therefore also change.

[0064] As the only heat generator, the heating system 10 of FIG. 2 comprises the heat pump 1 itself. That is to say that the heat pump 1 generates the heat during the charging of the buffer 3. In the defrosting operation, by contrast, the heat pump 1 is the load to which the heat is transferred from the buffer 3 or from the entire hydraulic circuit. Therefore, the heat pump 1 initially generates the heat during the charging of the buffer 3, which heat is used later for defrosting the heat pump 1.

[0065] In preferred embodiments, the heat pump 1 can have an additional auxiliary heat generator, for example an internal electrical heating rod (not shown), which can likewise be arranged in the outdoor unit ODU.

[0066] The operation of charging the buffer 3 is completed when the measured return line temperature is equal to or greater than the calculated set temperature Tsoll. For safety purposes, a limit value which lies above the set temperature Tsoll by 1 or 2 K can additionally be defined. As soon as the limit value is reached, the defrosting operation can be started.

[0067] FIG. 3 shows a second exemplary embodiment of a heating system 10 according to the invention. The heating system 10 of the second exemplary embodiment comprises, in addition to the heat pump 1, at least one second heat generator 12. The second heat generator 12 can be, for example, an external peak-load boiler which is operated with gas as fuel. Alternative examples of the second heat generator 12 comprise a gas heating boiler, an oil boiler, a combined heat and power plant, a fuel cell, a solar thermal unit or other devices which can provide heat to the heating medium. The further heat generator can also be designated as external heat generator since it is not an internal constituent part of the heat pump.

[0068] According to a preferred embodiment, the second heat generator 12 can be an electrical heat generator such as, for example, a heating rod or the like. In preferred embodiments, two additional heat generators 12 can also be provided in the heating system 10.

[0069] The second heat generator 12 can be used during the charging of the buffer 3 for providing additional heat in the event that the heat pump 1 alone cannot provide sufficient heat to reach the predefined set temperature Tsoll. During the defrosting operation, the second heat generator 12 can therefore support the charging of the buffer 3 with heat.

[0070] If, for example, the limit value or the set temperature Tsoll is not reached during the charging of the buffer 3, the second heat generator 12 can be actuated in order to provide additional heat. In this case, the second heat generator 12 can be operated, for example, with a predefined heating power, preferably with maximum heating power. According to a preferred embodiment, the heating power of the second heat generator 12 can be calculated or predefined as a function of a predefined charging duration of the buffer 3.

[0071] The second heat generator 12 is preferably operated with a minimum required heating power. In order to determine this heating power, a gradient of a temperature development of the buffer 3 can be predefined. The actually occurring gradient of the temperature can be measured during the charging of the buffer 3 and can be compared with the set gradient. If the measured gradient is lower than the predefined gradient, the second heat generator 12 can be correspondingly switched on.

[0072] The reaching of the limit value or of the set temperature Tsoll can be checked, for example, after the expiry of a predefined time period. Alternatively, the heating power required to reach the limit value or the set temperature Tsoll can be calculated in advance, so that this heating power can be applied for a calculated time period.

[0073] The heat quantity Qzu introduced during the time interval t can be determined by integrating the heating power. The applied heating power dQzu/dt can be known, for example, as a predefined value of the heat pump 1 and/or of the second heat generator 12. In this case, knowledge of the fluid used as heating circuit medium is not necessary.

[0074] Alternatively, the applied heating power dQzu/dt can be calculated on the basis of the mass of the heating circuit medium. For this purpose, the thermodynamic properties, such as, for example, the density and the heat capacity of the fluid used as heating circuit medium, have to be known. According to a preferred embodiment, water is used as heating circuit medium. The heating power can then be expressed by the following formula:

[00004]$\begin{array}{cc}d\mathrm{Qzu}/\mathrm{dt}=\left(c.Math.\mathrm{dm}/\mathrm{dt}.Math.T^{*}\right)& \left(4\right)\end{array}$

[0075] The mass flow dm/dt can be determined with the aid of a flowmeter 13 which is arranged upstream of the second heat generator 12 in the feed line. The temperature difference T* is determined as a difference between the return line temperature measured by the temperature sensor 11 and a temperature measured by a second temperature sensor 11 which is arranged upstream of the valve 4.

[0076] The heat power dQzu/dt introduced into the heating circuit medium can be calculated with respect to the total thermal mass on the basis of equation (4) via the heat capacity c and the measured mass flow dm/dt and the measured temperature difference T* and an empirically determined coefficient .

[0077] FIG. 4 shows a diagram which describes a dependence of the defrost energy on the external temperature. The defrost energy is the heat quantity required for defrosting the evaporator 5 and corresponds to the setpoint heat quantity Qsoll. It can be seen on the basis of FIG. 4 that the defrost energy Qsoll required for defrosting becomes higher as the external temperature falls. For example, at an external temperature T1 a defrost energy Q1 is required which is higher than the defrost energy Q2 at an external temperature T2>T1.

[0078] FIG. 4 is merely an example of how the heat quantity can depend on the external temperature. The heat quantity can also be dependent, for example, on the air humidity, the installation location of the ODU, the wind speed etc. The functional relationship can therefore also be different from that in FIG. 4 and in particular does not have to be a straight line.

[0079] In general, the set heat quantity Qsoll can be dependent on the device type of the heat pump 1. In particular, the defrost energy or set heat quantity Qsoll can be dependent on the dimensions of the components of the heat pump, in particular of the evaporator 5, of the heat exchanger 6 and/or of the refrigerant circuit and the like. Furthermore, the set heat quantity Qsoll can be dependent on the heat capacity or on the total thermal mass of the refrigerant or of the refrigerant circuit.

[0080] The order of magnitude of the set heat quantity Qsoll can be in the range of a few megajoules, for example.

[0081] The features disclosed in the preceding description, the claims and the drawings can be significant both individually and in any desired combination for the realization of the invention in its various refinements.