AU2013357622A1

AU2013357622A1 - Heating device and method for operating same

Info

Publication number: AU2013357622A1
Application number: AU2013357622A
Authority: AU
Inventors: Jose Corte-Real; Joao POTRA
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2012-12-13
Filing date: 2013-11-28
Publication date: 2015-07-30
Anticipated expiration: 2033-11-28
Also published as: AU2013357622B2; EP2932165B1; DE102012024347A1; EP2932165A1; WO2014090582A1; US20150330662A1

Abstract

The invention relates to a heating device (1) comprising a fluid reservoir (2), a heat exchanger (3), the supply line (4) of which is hydraulically connected to the fluid reservoir (2) geodesically deeper than its return line (5), and comprising a pump (6), which is arranged in the supply line (4) or in the return line (5), a bypass (7) being hydraulically connected to the supply line (4) and to the return line (5), the bypass (7) bypassing the heat exchanger (3) and the pump (6), and a three-way valve (8) being arranged in the connection of the bypass (7) to the supply line (4) or in the connection of the bypass (7) to the return line (5). In a method for operating the heating device (1), a first fluid temperature (T1) is determined in the return line (5) between the heat exchanger (3) and the bypass (7) and is compared to a desired temperature (TS). If the first fluid temperature (T1) is lower than the desired temperature (TS), the three-way valve (8) is switched to a first switch position (S1), in which the bypass (7) is at least partially opened. If the first fluid temperature (T1) is higher than the desired temperature (TS), a second switch position (S2) is selected, in which the bypass (7) is closed.

Description

Translation from German WO 2014/090582 Al PCT/EP2013/074951 Heating Device and Method for Operating Same The invention relates to a heating device as per the generic part of claim 1 and a method for operating it as per claim 6. Various heating devices for heating a fluid in a fluid reservoir - e.g. to 5 provide a store of hot water - are known in the art. In one variant, the fluid in the reservoir is heated by means of a heat exchanger. In another variant, fluid at a cooler temperature is first drawn from a lower region of the fluid reservoir and is then heated outside of the reservoir, after which it is conducted back into an upper region of the fluid 10 reservoir. Because the fluid's density is temperature-dependent, thermal layering occurs in the fluid reservoir, from hot at the top to cold at the bottom. To move the water through the heat exchanger, a pump is needed in the heat exchanger's flow line or return line. A problem here is that, for fluid to be able to be drawn off by a user, the is fluid in the upper region of the fluid reservoir needs to be at a certain, set temperature. If the fluid flowing in the flow line to the heat exchanger is very cold, the temperature in the return line will still be below the set temperature. It will therefore take a relatively long time before there is fluid in the fluid reservoir's draw-off region at the desired, set temperature. This 20 is inconvenient for the user. Furthermore, the temperature of the fluid in the draw-off region may rise to above the set temperature, if the fluid in the flow line to the heat exchanger is already relatively warm. This can lead to scalding and other harm. Admittedly, these problems can be avoided by adjusting the heating power at the heat exchanger; but 25 nevertheless, heating devices such as heat pumps are at their most efficient at a particular heating power. Operating them at other than that 2 WO 2014/0090582 Al PCT/EP2013/074951 optimal level will lead to increased costs, and is not environmentally friendly. The objective of the invention is therefore to overcome the drawbacks of the prior art by providing a heating device, and a method for operating it, 5 such that the heating device will operate at high efficiency and, at the same time, fluid at a set temperature will always be available from the fluid reservoir. Attention should also be paid to simplicity, low production costs, and operational reliability. According to the invention, this is achieved with the features of claims 1 10 and 6. Beneficial further developments are to be found in the dependent claims. In a heating device with a fluid reservoir, and with - a heat exchanger, whose flow line is hydraulically connected to the fluid reservoir at a geodetically-lower level than its return line is, and is - a pump, mounted in the flow line or the return line, the invention features: - a bypass, which is hydraulically connected to the flow line and the return line, and which bypasses the heat exchanger and the pump, and - a three-way valve, provided in the connection of the bypass to the flow 20 line or in the connection of the bypass to the return line. The arrangement according to the invention, with the three-way valve and the bypass, is now suitable for heating up fluid circulating through the bypass so as to bring it up to a set temperature. The fluid is not conducted back into the fluid reservoir until the fluid has reached the set 25 temperature. Due to thermal layering, fluid at the set temperature, on 3 WO 2014/0090582 Al PCT/EP2013/074951 arriving in the fluid reservoir, forms a layer in the upper, draw-off region of the fluid reservoir. In this way, a heat source associated with the heat exchanger can always work at its optimal operational level, thereby ensuring low operating costs, high efficiency, and high environmental 5 friendliness. Furthermore, the components required, such as the three way valve and the bypass, are relatively low in cost compared with the heating device's running costs and overall costs. The heat exchanger is preferably located outside of the fluid reservoir. This enables various heat sources, for example fossil-fuel-fired heating devices, heat pumps, and 10 solar thermal energy plants, to be coupled to the heat exchanger in an uncomplicated manner. The bypass too should be arranged outside of the fluid reservoir, so as to be readily accessible. For the same reason, the pump and/or the three-way valve should be located outside of the fluid reservoir. 15 In a further development of the invention, the heat exchanger is a condenser of a heat pump. Heat pumps in particular have an optimal operating band that is very narrow. With the three-way valve and bypass of the present invention, the heat pump can, however, always be operated at its optimal level, without this leading to deviations from the set 20 temperature. To permit automated operation of the heating device, the three-way valve is controllable, in a variant of the invention. The three-way valve can thus be automated, and therefore conveniently switched to different valve settings. 25 In a further development of the heating device, a first temperature sensor, for detecting a first fluid temperature in the return line, is provided in the return line, between the heat exchanger and the bypass. Based on the 4 WO 2014/0090582 Al PCT/EP2013/074951 detected first fluid temperature, the three-way valve can be switched promptly, thereby maintaining the set temperature continuously. In a further development of the heating device, the return line opens into a geodetically-upper draw-off region in the fluid reservoir. In addition, a 5 second temperature sensor may be provided there, to detect a second fluid temperature, in the draw-off region. Feeding into the upper region prevents convection currents from occurring inside the fluid reservoir; and therefore, the temperature layers of the fluid will be clearly separated from one another. As a result, the heating-device's efficiency is high, because 10 the fluid in the flow line is as cool as possible, and thus, there is a maximal temperature difference in the heat exchanger. With this in mind, it is particularly favourable if the flow line is connected to the fluid reservoir at a geodetically low level. In order to prevent fluid from flowing back out of the fluid reservoir and is into the return line no matter what the mounting position and operating situation, a nonreturn valve can be provided in the return line, between the fluid reservoir and the bypass. This is particularly advisable if settings of the three-way valve are provided in which the bypass is only partly opened. 20 Also, in a variant of the invention, the three-way valve is actuated by a control unit that has a set temperature stored in it. This control unit is connected, for data communication, to the first temperature sensor. Such a control unit is particularly suitable for automated operation of the heating device, because it is able to adjust the three-way valve according to the 25 set temperature. The invention also relates to a method for operating a heating device of the kind described above, in which the pump is activated so as to run fluid 5 WO 2014/0090582 Al PCT/EP2013/074951 through the heat exchanger, and heat is transferred to the fluid, in the heat exchanger. In the return line, between the heat exchanger and the bypass, a first fluid temperature is determined, and this is then compared with a set temperature. If the first fluid temperature is lower than the set 5 temperature, then the three-way valve gets switched to a first valve setting, in which the bypass is at least partly open. If, on the other hand, the first fluid temperature is higher than the set temperature, then the three-way valve gets switched to a second valve-setting, in which the bypass is closed. 10 With the inventive method, it is now possible to always heat the fluid up to the set temperature, irrespective of the heating power and the consequent amount of heat transferred to the fluid in the heat exchanger. A heat source, and hence the entire heating device, can therefore always be operated at the most environmentally-friendly and cost-effective operating is level. By partly opening the bypass, the fluid in the flow line can be continuously preheated and, at the same time, fluid at the set temperature will be fed continuously into the fluid reservoir. This means that the fluid heated to the set temperature is apportioned volumetrically, by the three-way valve, 20 to the bypass on the one hand and to the return line running to the fluid reservoir on the other hand. In a further development of the inventive method, the pump is deactivated if a third fluid temperature, in the flow line, before the bypass, is higher than the set temperature. If this is in fact the case, then the fluid in the 25 fluid reservoir - to as far down as the flow line's intake level - will already have been heated to the set temperature, and cannot be heated any further. The above-mentioned deactivation results in efficient operation of the heating device.

6 WO 2014/0090582 Al PCT/EP2013/074951 If a heat source is coupled exclusively to the heat exchanger, then this heat source should likewise be deactivated. Alternatively, activation of the pump can be made dependent upon the temperature of the fluid in fluid reservoir at the flow line's intake level. If the temperature drops a certain 5 amount below the set temperature, activation is brought about. To keep the number of temperature sensors small, it is therefore appropriate to mount the third temperature sensor at the flow line's intake level. In a variant of the invention that is simple from a control-engineering viewpoint, the bypass is fully opened when the three-way valve is 10 switched to its first valve-setting. In this way, the fluid will circulate entirely through the bypass until the fluid gets up to the set temperature. Then, it will be conducted through the return line, into the fluid reservoir, to be followed by a flow of cooler fluid that will, here again, circulate entirely through the bypass until it reaches the set temperature. 15 There is a further development of the inventive method, whose purpose is to prevent the three-way valve from switching rapidly from one setting to another: when the three-way valve is switched between valve-settings, a hysteresis is taken into account, so that the fluid temperature must always have departed from the set temperature by a certain amount before the 20 valve-setting can be changed. It is not always necessary to provide fluid at the set temperature, in the fluid reservoir. Therefore, the method can be extended such that, as a matter of priority ranking, the three-way valve will be switched to the second valve-setting when it is not necessary to maintain the set 25 temperature in a geodetically-upper draw-off region in the fluid reservoir. For this, the user may determine the times of the day when an increased level of comfort - with fluid at exactly the set temperature - is required. At other times of the day, no fluid will be circulated through the bypass, 7 WO 2014/0090582 Al PCT/EP2013/074951 and therefore fluid at as low as possible a temperature will be conducted through the heat exchanger. Therefore, there will be a large temperature difference in the heat exchanger, and consequently the efficiency of the heating device will be particularly high. 5 The drawings show examples of the invention: Fig. 1 shows a heating device, with a three-way valve - switched to a first setting - between the bypass and the return line; Fig. 2 shows a detail of the heating device in Fig. 1, but with the three way valve switched to its second setting; 10 Fig. 3 shows a heating device, with a three-way valve - switched to a first setting - between the bypass and the flow line; and Fig. 4 shows a detail of the heating device in Fig. 3, but with the three way valve switched to its second setting. In Fig. 1, there is a heating device 1, which has a fluid reservoir 2 filled is with fluid F. Fluid F can be drawn off, through draw-off line 30, from a draw-off region situated in the geodetically-upper end of the fluid reservoir 2. A second temperature sensor 12 is provided there, to detect a second fluid temperature T2, in the draw-off region 9. A feed line 31 feeds in at the geodetically-lower end of the fluid reservoir 2. Fluid F flows in through the 20 feed line 30, when fluid is drawn off through the draw-off line 30. In addition, the heating device 1 has a heat exchanger 3. The flow line 4 to this heat exchanger 3 is hydraulically connected to the fluid reservoir 2 at a geodetically-lower level than its return line 5 is. In particular, the return line 5 opens into the fluid reservoir 2 in a geodetically-upper region 25 thereof. On the other hand, the flow line 4 opens into the fluid reservoir 2 in the geodetically-lower region thereof.

8 WO 2014/0090582 Al PCT/EP2013/074951 There is a pump 6 in the flow line 4, to move the fluid F onward. In addition, there is a bypass 7, which is hydraulically connected to the flow line 4 and the return line 5, and which bypasses the heat exchanger 3 and the pump 6. A controllable three-way valve 8 is provided in the connection 5 between the bypass 7 and the return line 5. The heat exchanger 3, three-way valve 8, and bypass 7, are situated outside of the fluid reservoir 2. Between the heat exchanger 3 and the bypass 7, there is, in the vicinity of the return line 5, a first temperature sensor 11, for detecting a first fluid temperature T1 in the return line 5. 10 It will also be noticed that the heat exchanger 3 is a condenser 21 for a heat pump 20. This heat pump 20 comprises a heat-pump circuit for a refrigerant K. The condenser 21 and an evaporator 22 are integrated into said heat-pump circuit. Upstream of the condenser 21 (in terms of the refrigerant's direction of flow), there is a compressor 23; and downstream is of the condenser 21, there is an expansion valve 24. Thus, the refrigerant K and the fluid F flow through the condenser 21 in opposite directions, with the refrigerant K transferring heat to the fluid F. The three-way valve 8 is controlled by a control unit 10, which has a set temperature TS stored in it. There is a data-communications connection 20 from the control unit 10 to the first temperature sensor 11, to determine the setting S1, S2 (for S2, see Fig. 2) to which the valve is switched. The control unit 10 is also connected to the compressor 23 of the heat pump 20, and to the pump 6, the second temperature sensor 12, and a third temperature sensor 14. The third temperature sensor 14 serves to detect 25 the third fluid temperature T3, in the flow line 4, before the bypass 7. Instead of being in the position shown, i.e. outside of the fluid reservoir 2, the third temperature sensor 14 may be positioned in the region of the flow line's intake opening.

9 WO 2014/0090582 Al PCT/EP2013/074951 The control unit 10 is therefore suitable for implementing a method for operating the heating device 1 in which the pump 6 is first activated, causing fluid (F) to flow through the heat exchanger 3. The control unit 10 also activates the compressor 23 of the heat pump 20. In the heat 5 exchanger 3, which is at the pressure of the compressor 23, the refrigerant K, raised thereby to a high temperature, transfers heat to the fluid F. By means of the first temperature sensor 11, the control unit 10 determines the first fluid temperature T1, in the return line 5, between the heat exchanger 3 and the bypass 7. This first fluid temperature T1 is then 10 compared with the stored set temperature TS. Based on the result of this comparison, the control unit 10 switches the three-way valve 8 to a first valve-setting S1 if the first fluid temperature T1 is lower than the set temperature TS. With the first valve-setting S1, shown in Fig. 1, the bypass 7 is completely open. On the other hand, the is section of the return line 5 that opens into the fluid reservoir 2 is completely closed off by the three-way valve 8. Accordingly, the fluid F circulates through the bypass 7 and the heat exchanger 3. If, however, the first fluid temperature T1 is higher than the set temperature TS, then the control unit 10 will switch the three-way valve 8 20 to a second valve-setting S2, as can be seen in Fig. 2, which is a detail A from Fig.1 but showing the second valve-setting S2, instead of the first valve-setting S1 shown in Fig. 1. In the second valve-setting S2, the bypass 7 is closed. Then, the fluid F, heated up to the set temperature TS, is conducted into the draw-off region 9 of the fluid reservoir 2; and is 25 followed by cooler fluid F flowing - through the flow line 4 - from the fluid reservoir 2. Advantageously, the control unit takes a hysteresis into account when the three-way valve switches over between valve-settings S1 and S2, in order 10 WO 2014/0090582 Al PCT/EP2013/074951 to prevent rapid switching back and forth in the event that the first fluid temperature T1 drifts around the set temperature TS. In addition, the pump 6 can be deactivated by means of the control unit 10, when the third fluid temperature T3 - in the flow line 4, before the 5 bypass 7 - is higher than the set temperature TS. In addition, switching of the three-way valve 8 to the second valve-setting S2 may be accorded priority ranking, when maintenance of the set temperature TS in the draw-off region 9 is not required. For this, the user can store time-periods in the control unit 10. 10 Fig. 4 shows a detail B from the heating device 1 shown in Fig. 3. The heating device 1 in Fig. 3 largely corresponds to that shown in Fig. 1, except that, in the form of embodiment shown in Fig. 3, the three-way valve 8 is provided in the connection between the bypass 7 and the flow line 4. Moreover, there is an additional non-return valve 13 in the return is line 5, between the fluid reservoir 2 and the bypass 7. In Fig. 4, like in Fig. 2, the three-way valve 8 is shown in its second valve setting S2, in which the bypass 7 is, here again, entirely blocked by the three-way valve 8. In Fig. 3, unlike in Fig. 1, the bypass 7 is only partly open with the three 20 way valve in its first valve-setting S1. At the same time, the part of the flow line 4 leading from the fluid reservoir 2 to the three-way valve 8 is at least partly open. Therefore, in the three-way valve 8, the heated fluid F from the bypass 7 becomes mixed with the cool fluid F from the flow line 4; and, in the first valve-setting S1, the control unit 10 regulates the three 25 way valve 8 in such a way that the fluid F in the return line 5 is maintained continuously at the set temperature TS.

11 WO 2014/0090582 Al PCT/EP2013/074951 Claims 1. A heating device (1) with a fluid reservoir (2), and with: - a heat exchanger (3) whose flow line (4) is hydraulically connected to the fluid reservoir (2) at a geodetically-lower level than its return 5 line (5) is, and - a pump (6) mounted in the flow line (4) or in the return line (5); characterised in that a bypass (7) is provided, which is hydraulically connected to the flow line (4) and the return line (5), and which bypasses the heat 10 exchanger (3) and the pump (6), and a three-way valve (8) is provided in the connection of the bypass (7) to the flow line (4) or in the connection of the bypass (7) to the return line (5). 2. A heating device (1) as claimed in claim 1, 15 characterised in that the heat exchanger (3) is a condenser (21) of a heat pump (20). 3. A heating device (1) as claimed in claim 1 or 2, characterised in that the three-way valve (8) is controllable. 4. A heating device (1) as claimed in any of the above claims, 20 characterised in that a first temperature sensor 11 is provided in the return line (5), between the heat exchanger (3) and the bypass (7), to detect a first fluid temperature 11, in the return line (5).

12 WO 2014/0090582 Al PCT/EP2013/074951 5. A heating device (1) as claimed in claim 4, characterised in that the three-way valve (8) is actuated by a control unit (10) which has a set temperature stored in it and which is connected, for data communication, to the first temperature sensor (11). 5 6. A method for operating a heating device (1) as claimed in any of claims 1 to 5, characterised by the following steps: a) activating the pump (6) and running fluid (F) through the heat exchanger (3), 10 b) transferring heat to the fluid (F), in the heat exchanger (3), c) determining a first fluid temperature (T1), in the return line (5), between the heat exchanger (3) and the bypass (7), d) comparing the first fluid temperature (T1) with a set temperature (TS), is el) switching the three-way valve (8) to a first valve-setting (Si), in which the bypass (7) is at least partly open, if the first fluid temperature (T1) is lower than the set temperature (TS), and e2) switching the three-way valve (8) to a second valve-setting (S2), in which the bypass (7) is closed off, if the first fluid temperature 20 (T1) is higher than the set temperature (TS). 7. The method as claimed in claim 6, characterised by the following step: f) deactivating the pump (6) if a third fluid temperature (T3), in the flow line (4), before the bypass (7), is higher than the set 25 temperature (TS).

13 WO 2014/0090582 Al PCT/EP2013/074951 8. The method as claimed in claim 6 or 7, wherein, in the three-way valve's first valve-setting (Si), the bypass (7) is completely opened. 9. The method as claimed in any of claims 6 to 8, 5 wherein, when the three-way valve (8) is switched between valve-settings (S1, S2), a hysteresis is taken into account. 10. The method as claimed in any of claims 6 to 9, characterised by the following step: g) priority ranking is accorded to switching the three-way valve (8) 10 to the second valve-setting (S2) when it is not necessary to maintain the set temperature (TS) in a geodetically-upper draw off region (9) in the fluid reservoir (2).

Claims

1. A heating device (1) with a fluid reservoir (2), and with: - a heat exchanger (3) whose flow line (4) is hydraulically connected to the fluid reservoir (2) at a geodetically-lower level than its return 5 line (5) is, and - a pump (6) mounted in the flow line (4) or in the return line (5); characterised in that a bypass (7) is provided, which is hydraulically connected to the flow line (4) and the return line (5), and which bypasses the heat 10 exchanger (3) and the pump (6), and a three-way valve (8) is provided in the connection of the bypass (7) to the flow line (4) or in the connection of the bypass (7) to the return line (5).

2. A heating device (1) as claimed in claim 1, 15 characterised in that the heat exchanger (3) is a condenser (21) of a heat pump (20).

3. A heating device (1) as claimed in claim 1 or 2, characterised in that the three-way valve (8) is controllable.

4. A heating device (1) as claimed in any of the above claims, 20 characterised in that a first temperature sensor 11 is provided in the return line (5), between the heat exchanger (3) and the bypass (7), to detect a first fluid temperature 11, in the return line (5). 12 WO 2014/0090582 Al PCT/EP2013/074951

5. A heating device (1) as claimed in claim 4, characterised in that the three-way valve (8) is actuated by a control unit (10) which has a set temperature stored in it and which is connected, for data communication, to the first temperature sensor (11). 5

6. A method for operating a heating device (1) as claimed in any of claims 1 to 5, characterised by the following steps: a) activating the pump (6) and running fluid (F) through the heat exchanger (3), 10 b) transferring heat to the fluid (F), in the heat exchanger (3), c) determining a first fluid temperature (T1), in the return line (5), between the heat exchanger (3) and the bypass (7), d) comparing the first fluid temperature (T1) with a set temperature (TS), is el) switching the three-way valve (8) to a first valve-setting (Si), in which the bypass (7) is at least partly open, if the first fluid temperature (T1) is lower than the set temperature (TS), and e2) switching the three-way valve (8) to a second valve-setting (S2), in which the bypass (7) is closed off, if the first fluid temperature 20 (T1) is higher than the set temperature (TS).

7. The method as claimed in claim 6, characterised by the following step: f) deactivating the pump (6) if a third fluid temperature (T3), in the flow line (4), before the bypass (7), is higher than the set 25 temperature (TS). 13 WO 2014/0090582 Al PCT/EP2013/074951

8. The method as claimed in claim 6 or 7, wherein, in the three-way valve's first valve-setting (Si), the bypass (7) is completely opened.

9. The method as claimed in any of claims 6 to 8, 5 wherein, when the three-way valve (8) is switched between valve-settings (S1, S2), a hysteresis is taken into account.

10. The method as claimed in any of claims 6 to 9, characterised by the following step: g) priority ranking is accorded to switching the three-way valve (8) 10 to the second valve-setting (S2) when it is not necessary to maintain the set temperature (TS) in a geodetically-upper draw off region (9) in the fluid reservoir (2).