GB2528173A

GB2528173A - Thermodynamic boiler

Info

Publication number: GB2528173A
Application number: GB1511035.6A
Authority: GB
Inventors: Mihai Radulescu; Cã Dric Teuillieres
Original assignee: Electricite de France SA
Current assignee: Electricite de France SA
Priority date: 2014-06-25
Filing date: 2015-06-23
Publication date: 2016-01-13
Also published as: FR3022989B1; FR3022989A1; GB201511035D0

Abstract

The thermodynamic boiler 1 comprises a tank 2 filled with sanitary hot water (SHW). The tank is coupled to a heat pump 3 arranged to heat the SHW. A surface of the tank is at least partially covered by a first layer of thermal insulation 24 and a jacket 5 filled with a heat transfer fluid such as industrial water or a water-glycol mixture is in thermal communication with the first layer to recover heat energy dissipated through the first layer from SHW in the tank. The jacket is connected to a heat exchanger 60 so that heat recovered from the first layer by the heat transfer fluid may be passed to a refrigerant of the heat pump. In a first preferable embodiment the heat exchanger is provided between an evaporator 34 and compressor 31 of the heat pump so that heat lost through the first layer is used to increase the co-efficient of performance of the heat pump. In second and third preferable embodiments the heat exchanger is a fluid/air heat exchanger (61, figure 4) that heats air passing over the evaporator or a spraying device (62, figure 5) that sprays heat transfer fluid over the evaporator.

Description

I

GENERAL TECHNICAL FIELD

The present invention relates to a thermodynamic boiler comprising a tank for storing sanitary hot water (designated hereafter as coupled with a heat pump (designated hereafter as HP), the HP allowing heating or at the very least pre-heating of the SHW contained in the tank.

STATE OF THE ART

The large majority of thermodynamic boilers use outdoor air as a heat source, also designated as a "cold source".

Two types of thermodynamic boilers in which the cold source of the HP is outdoor air, are today available on the market.

The first type, schematically illustrated in the appended Fig. 1, is designated as a "one-piece thermodynamic boiler".

In Fig. 1, it may be seen that that this boiler comprises a tank B and a heat pump HP. The tank is connected at its base, to an outer cold water supply source CW and at its upper portion, to a duct for distributing SHW in the building in which this boiler is located. An electric resistor R placed in the tank B allows heating of the water therein.

The HP conventionalLy comprises an evaporator, a compressor, a condenser and an expansion valve, (not shown in the figure), successively mounted on a refrigerant fluid circuit C which connects them together.

Circulation of the refrigerant fluid is ensured by the compressor.

A sheath G is mounted on the HP and gives the possibility of ensuring circulation of air at the evaporator of the HP, so that the calories recovered from the outdoor air allow heating of the refrigerant fluid circulating at the evaporator.

In the large majority of the cases, the condenser is formed with a pipe inside which circulates the refrigerant fluid, this pipe being wound around the tank B, in contact with its outer wall, and under a layer of insulation material (not shown in the figure). Heat exchange occurs at the condenser and has the effect of heating the SHW contained in the tank, thereby reducing the need to resort to the use of the electric resistor R. If the initial location of the tank B of the boiler is not near an outwardly facing wall of the building, installing the thermodynamic boiler is S difficult since the sheath G has to cross several walls before attaining an outer wall. A boiler designated as a "split thermodynamic boiler" is then used, illustrated in the appended Fig. 2. The same elements as those of Fig. 1 bear the same numerical references.

This boiler is different from the earlier one in that the HP is installed outside the building. The calories recovered by exchange with the outdoor air are conveyed via the refrigerant fluid circuit C to the outer wall of the tank B, in order to heat the contents thereof. It is seen that there are head losses inside the refrigerant fluid circuit C, and that the latter depend on the distance between the HP and the tank B. Both types of the aforementioned thermodynamic boilers further have the same drawbacks.

First of all, the performance of a thermodynamic boiler strongly depends on the temperature of the outdoor air. In winter, or as soon as the outdoor air is too cold, for example as soon as it attains a temperature of less than -5C, the HP cannot be used because the outdoor air does not give the possibility of providing calories. It is then necessary to use the electric resistor R for producing sanitary hot water. The result of this is an overall yield of the boiler clearly less than in the case when the outdoor air is warmer.

Further, the SHW is stored in the tank B for rather long periods of time. Now, heat energy losses are noticed at the tank, related to the fact that the heat crosses the wall of the tank B and then the layer of the thermal insulation material placed around the tank, so as to be dissipated in the ambient air of the room where the tank B is Located.

These heat losses of the tank B also strongly reduce the overall performance of the thermodynamic boiler.

PRESENTATION OF THE INVENTION

The object of the invention is to provide a thermodynamic boiler for which the heat energy losses of the SHW storage tank, are no longer lost but on the contrary recovered and upgraded, in order to improve the coefficient of performance (COP) of the boiler. This performance coefficient is defined as the amount of heat produced over the amount of consumed electricity.

The object of the invention is also to more specifically improve the performances of the HP associated with the tank.

S For this purpose, the invention relates to a thermodynamic boiler comprising a tank for storing sanitary hot water, coupled with a heat pump which allows the sanitary hot water contained in said storage tank to be heated up, the storage tank being surrounded over at least one portion of its surface with a Layer of thermal insulation material.

According to the invention, this boiler comprises a jacket, filled with a heat transfer fluid and in thermal communication with said thermal insulation material layer in order to recover the heat energy given off by the latter, this jacket being connected to a heat exchanger device allowing transfer of the heat of said heat transfer fluid to the refrigerant fluid of the heat pump.

According to other advantageous and non-limiting features of the invention, taken alone or in combination: -said jacket is positioned outside and in contact with said thermal insulation material layer; -the heat exchanger device is a heat transfer fluid/refrigerant fluid exchanger, such as an exchanger with plates, positioned on the refrigerant fluid circuit of the heat pump, downstream from the evaporator and upstream from the compressor of this heat pump and this heat transfer fluid/refrigerant fluid exchanger is connected to the jacket through a circuit provided with a driving pump; -the heat exchanger device is a heat transfer fluid/air exchanger, coupled with the evaporator of the heat pump which forms an air/refrigerant fluid exchanger, this heat transfer fluid/air exchanger being positioned in the air intake of said evaporator and being connected to the jacket through a circuit provided with a driving pump; -the air is outdoor air and the heat transfer fluid/air exchanger is positioned in the outdoor air intake of said evaporator; -the heat exchanger device is a spraying device coupled with the evaporator of the heat pump, this spraying device being connected to the jacket via a first valve, such as a solenoid valve, and allows spraying of the fins of the evaporator of the heat pump with the heat transfer fluid of the jacket, said evaporator forming an air/refrigerant fluid exchanger; -the jacket is connected to the water supply network via a second S valve, such as a solenoid valve; -a sensor measuring the temperature of the water of the jacket is positioned between the jacket and the heat exchanger device; -a sensor measuring the temperature of the air supplying the evaporator of the heat pump is positioned at the air intake of the evaporator; -at least one of the elements selected from among the first valve, the second valve, the driving pump, the sensor measuring the temperature of the water of the jacket and the sensor measuring the temperature of the air supplying the evaporator of the heat pump is controlled by a central control unit which also controls operation of the heat pump; -the boiler comprises a second layer of a thermal insulation material, positioned on the outside of the jacket and in contact with the outer wall of the latter; and -it comprises an additional reservoir in heat transfer fluid communication with said jacket.

PRESENTATION OF THE FIGURES

Other features and advantages of the invention will become apparent from the description which will now be made thereof, with reference to the appended drawings, which illustrate, as an indication and not as a limitation, a possible embodiment.

In these drawings: -Figs. 1 and 2 are diagrams illustrating thermodynamic boilers according to the state of the art, -Figs. 3 to 5 are diagrams illustrating three different embodiments of the thermodynamic boiler according to the invention, and -Fig. 6 is a diagram illustrating a thermodynamic boiler known from the state of the art, but modified so as to operate according to the invention. )

DETAILED DESCRIPTION

A first embodiment of the invention wilt now be described in S connection with Fig. 3.

In this figure, a thermodynamic boiler 1 may be seen, comprising a tank 2, coupted with a HP 3, the tatter being controtted by a centrat controt unit 4.

The tank 2 comprises a walt 21 which detimits a chamber 20, inside which is stored the sanitary hot water SHW.

This tank 2 is connected, at its lower portion, to a cold water suppty duct 22, itsetf connected to the cotd water distribution network.

The tank 2 is also connected, at its upper portion, to a SHW distribution duct 23, connected to different drawing-off points, not shown in the figure.

The tank 2 may atso be equipped with an etectric resistor for additionat heating, positioned inside the chamber 20, preferabty in its tower portion, this resistor not being itlustrated in the figure.

The walt 21 of the tank is preferabty surrounded on the totatity or quasi-totatity of its outer surface, with a layer of a thermat insutation materiat 24 which has the function of timiting thermal tosses of the tank 2.

Conventionalty, the HP 3 comprises a compressor 31, a condenser 32, an expansion vatve 33 and an evaporator 34, mounted in series on a refrigerant fluid circuit 35.

According to a first atternative embodiment, (as ittustrated in Fig. 3), the condenser 32 comprises a pipe 320, positioned around at least one portion of the watt 21 of the tank 2, more specificatty between this watt 21 and the insutation materiat tayer 24. This pipe 320 is for exampte wound heticalty around the tank 2.

A second atternative embodiment of the condenser 32 may atso be used. This atternative is only ittustrated in Figs. 4 and 5 for simptification purposes.

In this case, the condenser 32 is a refrigerant ftuid/SHW heat exchanger and it is connected via an intet duct 201 and an outlet duct 202 inside the chamber 20. A pump 203 preferably placed on the duct 201 attows SHW to circulate in the condenser 32 where it is heated up. The pump 203 is controlled by the central unit 4.

Operation of the HP is the following.

The air A is used here as a!cold source, and the calories S recovered in this air A are transferred to the refrigerant fluid, in the evaporator 34, by heat exchange between the air A and the fins and portions of the circuit of the evaporator inside of which circulates the refrigerant fluid. This has the effect of vaporizing the refrigerant fluid which is found at low pressure. In the compressor 31, the refrigerant fluid is compressed and its temperature increases.

When the fluid reaches the condenser 32, it releases the calories, by heat exchange, which has the effect of heating up the SHW contained in the tank 2. At the outlet of the condenser 32, the cooled refrigerant fluid has returned to the liquid state, and it then enters the expansion valve 33 where it returns to a low pressure and low temperature, before beginning a new heat exchange cycle again.

The air is preferably outdoor air (from the outside of the building).

The air of a non-heated room of the building or air extracted from this building by the ventilation may also be used.

According to the invention, and in order to reduce the thermal losses, the tank 2 and its thermal insulation layer 24 are surrounded by a jacket 5. This jacket 5 comprises two walls, an inner one and an outer one, spaced apart from each other so as to make an enclosure between them which contains a heat transfer fluid. The inner wall of the jacket is in contact with the layer of the thermal insulation material 24.

This heat transfer fluid is preferably "industrial" water, i.e. unsuitable for consumption and which cannot be used as sanitary water. Other heat transfer fluids may also be contemplated, for example glycolated water (a water-glycol mixture).

The jacket 5 is connected, via a duct 51 equipped with a pump for driving the heat transfer fluid 52, to a heat exchanger device 6 which allows transfer of the heat of the heat transfer fluid circulating inside the jacket 5, to the refrigerant fluid of the HP 3.

The operation of the pump 52 is controlled by the central control unit 4.

The heat exchanger device 6 is further connected through a return duct 53 to the jacket 5, preferably at a point located at the lower portion of the tatter. The duct 51, as for it, is preferably connected to the upper portion of the jacket 5.

In the embodiment illustrated in Fig. 3, this heat exchanger device 6 is a heat exchanger 60, for example with plates, inside which direct heat S exchange is carried out through a wall which is in contact on one side with the refrigerant fluid of the circuit 35 of the HP and on the other side with the heat transfer fluid of the circuit of the jacket 5.

This heat exchanger 60 is positioned on the refrigerant fluid circuit of the HP, downstream from the evaporator 34 and upstream from the compressor 31, relatively to the direction of circulation of the refrigerant fluid inside the circuit 35.

The operation of the boiler 1 is described hereafter.

The jacket 5 is in contact with the thermal insulation layer 24, so as to be in thermal communication with the latter. Calories (thermal losses) pass through the insulation layer 24. They are recovered by the heat transfer fluid contained in the jacket 5. This heat transfer fluid slowly warms up by a few degrees so as to be stabilized around a temperature which is preferably of the order of about 25CC. This warm heat transfer fluid circulates in the exchanger 60, where it transfers its calories to the refrigerant fluid 35 which has itself already recovered some from the cold source, at the evaporator 34.

Preferably, a temperature sensor 54 is installed on the heat transfer fluid circuit, outside the jacket 5, still preferably upstream from the pump 52. This temperature sensor 54 gives the possibiLity of measuring the temperature of the heat transfer fluid at the outlet of the jacket 5, and this sensor 54 sends the value of the measured temperature to the central control unit 4.

Also preferably, another temperature sensor 340, placed at the inlet of the evaporator 34, gives the possibility of measuring the temperature of the in-flowing air. This sensor also sends this piece of information to the central control unit 4.

The central control unit 4 is equipped with a program which allows comparison of the values of the temperatures provided by the sensors 54 and 340.

When the temperature of the heat transfer fluid measured by the sensor 54 is higher than the (outdoor) air temperature, the centraL unit 4 starts the pump 52, so that heat exchange may be carried out at the exchanger 60.

S

Conversely, if the temperature measured by the sensor 54 is tower than the temperature of the outdoor air measured by the sensor 340, the centrat unit 4 then orders stopping of the pump 52, so as not to degrade the operation of the HP 3 and not to coot the refrigerant ftuid or risk icing up of the heat transfer S ftuid.

Preferabty, when the sensor 54 sends to the centrat unit 4, information relating to the fact that the temperature of the heat transfer fluid is below a threshotd value, (for exampte about 10°C), the central unit 4 atso stops operation of the pump 52, in order to avoid continuing to coot the heat transfer ftuid and to then increase the thermat losses of the tank 2.

A second embodiment of the invention witl now be described in connection with Fig. 4. The same elements as those of the embodiment of Fig. 3 bear the same numericat references and witt therefore not be described again in detail.

The thermodynamic boiter of Fig. 4 differs from that of Fig. 3 by its heat exchanger device 6.

This device 6 is a heat transfer ftuidlair exchanger 61, coupted with the evaporator 34 which is an air/refrigerant ftuid exchanger. The exchanger 61 is placed at the air intake of the evaporator 34.

The heat exchanger 61 is preferabty a tubutar exchanger notabty a tubular exchanger with fins. It gives the possibitity of achieving heat exchange between the heat transfer fluid from the jacket 5 and the air which penetrates into the evaporator 34, in order to preheat the latter, before it enters the evaporator 34. The thereby pre-heated air witl then transfer its catories to the refrigerant ftuid circutating in the circuit 35 of the HP 3.

This second embodiment also has the advantage of being able to be instatted, as a refurbishment, on an existing thermodynamic boiter. This possibitity is ittustrated in Fig. 6. The etements identicat with those of Fig. 4 bear the same numericat references.

A jacket 5 is positioned around the tank 2 and around the thermat insutation layer 24, not shown in Fig. 6. This jacket 5 does not necessarity cover the whote of the outer surface of the tank 2.

The heat exchanger device 61 is positioned in the sheath 37 for supptying outdoor air connected to the HP 3. Finalty the jacket 5 is connected to the exchanger 61, as described eartier. The operation is the same.

A third embodiment will now be described in connection with Fig. 5. The elements identical with those of the embodiments of Figs. 3 and 4 bear the same numerical references.

The thermodynamic boiler 1 differs from the previous ones by its S heat exchanger device 6. In this case, the device 6 is a spraying device 62, coupled with the evaporator 34. The device 62, such as a spray attachment, gives the possibility of spraying the fins or the tubes of the evaporator 34 inside which circulates the refrigerant fluid 35, by means of the heat transfer fluid from the jackets.

Further, a solenoid valve 55 is advantageously positioned on the duct 51 which connects the jacket 5 to the device 62. This solenoid valve 55 is driven by the central control unit 4.

Further, the jacket 5 is connected, preferably at its lower end, to a cold water supply duct 56, connected to the water supply network. This water is the heat transfer fluid.

When the sensor 340 measuring the temperature of the outdoor air detects that this area is particularly cold, i.e. below a threshold value, for example YC, it sends this information to the central unit 4. It is also possible to provide a humidity sensor for the air entering the evaporator 34, this sensor, not shown in the figures, also sending back information on the hygrometry level to the central unit 4.

When the air is below the threshold temperature, the central unit 4 may then act on the solenoid valve 55 to allow passing of the water towards the spraying device 62, as well as on the solenoid valve 57 for allowing a new supply of water to the jacket 5.

The spraying device 62 also allows de-icing of the fins of the evaporator 34.

The overall performance of the HP is improved, since there is no need to use the compressor 31 for carrying out de-icing.

For the different embodiments which have just been described, it is possible according to one alternative to add an additional layer of insulation material, referenced as 25, positioned on the outside of the jacket 5 and in contact with the outer wall of the latter. This layer 25 is only illustrated in Fig. 4 for simplification purposes.

In this case, the tank 2 of the thermodynamic boiler has double insulation and the jacket 5 recovers almost the whole of the thermal losses.

Also, for the different embodiments which have just been described, it is possible to vary the heat transfer fluid volume contained in the jacket 5. To do this, and in order not to increase the thickness of the jacket 5, it is possible to provide an additional reservoir 50, preferably in the upper portion S of the jacket, as illustrated in Fig. 4.

The volume of the jacket 5 and of the reservoir 50 may be adapted in order to increase the performances of the thermodynamic boiler 1. It will be noted that a jacket 5 of small volume more rapidly increases its temperature but stores less heat. On the other hand, a jacket 5 of larger volume, or even equipped with the reservoir 50, gives the possibility of storing more calories, but it takes more time to heat up and capture the calories from the tank 2.

The device according to the invention has many advantages.

Regardless of the embodiment used, the jacket 5 is at atmospheric pressure and does not require a complex structure or the use of sophisticated materials resisting to high pressures.

The performance of a thermodynamic boiler, measured by its performance coefficient (COP), is strongly related to the temperature of the cold source (the outdoor air here). The heat exchanges between the heat transfer fluid contained in the jacket 5 on the one hand and the refrigerant fluid of the circuit 35 or else the outdoor air penetrating into the evaporator 34 on the other hand are increased by the temperature difference between the heat transfer fluid and the refrigerant fluid or the air.

The useful heat of the jacket 5 is therefore more used when the temperature of the outdoor air is low and therefore at the moment when the performance coefficient of the HP is precisely low.

Finally, it will be noted, that in the first two embodiments, the pump 52 of the circuit of the jacket 5 is started at the same time as the HP, (via the central unit 4). The head losses inside the heat transfer fluid circuit are therefore very small and so also the electricity consumption of the pump 52.

Claims

CLAIMS1. A thermodynamic boiLer (1) comprising a tank for storing sanitary hot water (2), coupLed with a heat pump (3) which aLLows the sanitary hot water contained in said storage tank (2) to be heated up, the storage tank (2) being surrounded on at Least one portion of its surface with a Layer of a thermaL insuLation materiaL (24), characterized in that it comprises a jacket (5), filLed with a heat transfer fluid and in thermaL communication with said thermaL insuLation materiaL Layer (24) in order to recover the heat energy given off by the Latter, and in that this jacket (5) is connected to a heat exchanger device (6) aLlowing transfer of the heat of said heat transfer fLuid to the refrigerant fluid of the heat pump (3).
2. The thermodynamic boiLer (1) according to cLaim 1, characterized in that said jacket (5) is positioned on the outside and in contact with said thermal insuLation materiaL layer (24).
3. The thermodynamic boiler (1) according to claim 1 or 2, characterized in that the heat exchanger device (6) is a heat transfer fLuid/refrigerant fluid exchanger (60), such as an exchanger with pLates, positioned on the refrigerant fLuid circuit (35) of the heat pump (3), downstream from the evaporator (34) and upstream from the compressor (31) of this heat pump and in that this heat transfer fluid/refrigerant fLuid exchanger (60) is connected to the jacket (5) through a circuit (51, 53) provided with a driving pump (52).
4. The thermodynamic boiler (1) according to claim 1 or 2, characterized in that the heat exchanger device (6) is a heat transfer fLuid/air exchanger (61), coupled with the evaporator (34) of the heat pump (3) which forms an air/refrigerant fLuid exchanger, this heat transfer fLuid/air exchanger (61) being positioned in the air intake of said evaporator (34) and being connected to the jacket (5) through a circuit (51, 53) provided with a driving pump (52).
5. The thermodynamic boiLer (1) according to cLaim 4, characterized in that the air is outdoor air and in that the heat transfer fLuid/air exchanger (61) is positioned in the outdoor air intake of said evaporator (34).
6. The thermodynamic boiler (1) according to claim 1 or 2, characterized in that the heat exchanger device (6) is a spraying device (62), coupLed with the evaporator (34) of the heat pump, this spraying device (62) being connected to the jacket (5) via a first vaLve (55), such as a soLenoid vaLve, and aLLows spraying of the fins of the evaporator (34) of the heat pump (3) with the heat transfer fluid of the jacket (5), said evaporator (34) forming an airlrefrigerant fluid exchanger.
7. The thermodynamic boiler (1) according to claim 6, characterized in that the jacket (5) is connected to the water supply network, via a S second valve (57), such as a solenoid valve.
8. The thermodynamic boiler (1) according to one of the preceding claims, characterized in that a sensor (54) measuring the temperature of the water of the jacket is positioned between the jacket (5) and the heat exchanger device (6).
9. The thermodynamic boiler (1) according to one of the preceding claims, characterized in that a sensor (340) measuring the temperature of the air supplying to the evaporator (34) of the heat pump is positioned at the air intake of the evaporator.
1O.The thermodynamic boiler (1) according to at least one of claims 4, 6, 7, 8 or 9, characterized in that at least one of the elements selected from among the first valve (55), the second valve (57), the driving pump (52), the sensor (54) measuring the temperature of the water of the jacket and the sensor (340) measuring the temperature of the air supplying to the evaporator of the heat pump is controlled by a central control unit (4) which also controls operation of the heat pump (3).
11. The thermodynamic boiler (1) according to one of the preceding claims, characterized in that it comprises a second layer of a thermal insulation material (25), positioned on the outside of the jacket (5) and in contact with the outer wall of the latter.
12. The thermodynamic boiler (1) according to one of the preceding claims, characterized in that it comprises an additional reservoir (50) in heat transfer fluid communication with said jacket (5).