CH699989B1 - domestic heating installation equipped with a heat pump. - Google Patents

Abstract

In a domestic heating installation (1) operating with a heat pump (6), a heat pipe (7) extending hot gases at the outlet of the compressor (6a) to another thermal receiver makes it possible to take off some of the hot gases. of their energy and thus achieve heating of higher temperature without encumbering the overall energy efficiency of the installation.

Description

The invention relates to a stationary heating system operating with a heat pump. Heat pumps are increasingly used for heating buildings because of their energy efficiency. These make it possible to extract water, air or any other thermal reserve from the heat which, in the majority of the cases, is restored at higher temperature to water which circulates then in a circuit of heater. The latter can be a network of pipes embedded in a screed or radiators for example. As the temperature setpoint for this water influences the energy efficiency of the heat pump, it is generally tried to keep it as low as possible, which is why space heating heat pumps are preferably coupled to a heat distribution network. floor heat, called low temperature. Typically, such a method of heat distribution provides the heating function with a water whose temperature varies between 28 ° C and 35 ° C, for which situation the heat pump is performing.

The performance of the heat pump is often measured by a coefficient called coefficient of performance (COP) and defined by the ratio between the power produced in the form of heat and the electrical power consumed. This ratio is dependent on several factors whose essential factor is the operating temperature. Indeed, the efficiency of a heat pump decreases with the temperature difference that it must provide. It is therefore clear that heating with a heat pump will be all the more efficient as the temperature of the source is high and the outlet temperature is low. Typically, the value of this coefficient may vary depending on the nature of the installation and the source and output temperatures between 2 and 7.

A heat pump installed for space heating can parallel serve for heating domestic hot water. As the temperature set point for domestic hot water production is higher - around 65 ° C - the coefficient of performance falls and the overall performance of the plant suffers. It remains above 1, which corresponds to heating by a simple electrical resistance dipped in water, the energy gain remains large enough to justify the installation. Heat pumps available on the market therefore have special equipment to perform these two functions. In such an installation, where the heat pump is used for space heating and domestic hot water production, the energy content of domestic hot water production becomes even greater than the heating requirement of the domestic hot water. local is small. This is increasingly the case in single-family houses because they are increasingly isolated while the consumption of domestic hot water does not decrease.

The object of the invention is to provide an arrangement improving the overall energy efficiency of a stationary heat pump heating system ensuring on the one hand the heating of the premises and on the other hand the production of hot water. Such an installation therefore comprises at least one heat pump and a thermal reserve for domestic hot water, this reserve can be the same domestic hot water or a thermal mass to which, by a heat exchanger, the water intended for the needs Sanitary takes its heat.

Heat pumps, regardless of the source from which the calories are taken, have in common to have a compressor. This one has the role of compressing a gas which, at high pressure, cools and condenses (it is the phase where heat is supplied to the installation) before being relaxed and then evaporated (this is the phase where heat is taken from the outside environment). At the outlet of the compressor, the gas is at a high pressure but also at an elevated temperature which can, depending on the nature of the installation, be approximately 85 ° C. Under this pressure, the gas, according to its nature, must first cool before it can condense. The energy that the gas can return to the system is therefore contained partly as a sensible heat in the superheated gas and partly as latent heat, the latter part being the largest. Ideally, the energy contained in the form of sensible heat in the superheated gases should be used for the "high temperature" application (in the aforementioned case for domestic hot water) while the remaining energy would remain available for the "low temperature" application (in the aforementioned case for space heating).

[0006] Patent GB 720 779 A proposes the integration of a heat pump in a water tank. In such a tank, the temperature of the water varies according to its position inside it. Indeed, the cold water is more dense, it is naturally down while the hottest water is in the upper part of the tank. Such tanks are being used more and more today. Often, in order not to impose on him movements that would lead to mixing water of different temperatures, this water is not used as domestic hot water but as a thermal reserve crossed by a tank or pipe in which the water circulates to the sanitary application. In patent GB 720 779 A, the superheated gases leaving the compressor will logically cool in the upper part of the tank before going to condense in the intermediate part. Such integration, if it is judicious from a thermal point of view, nevertheless has drawbacks, such as that of access to the compressor in case of problems or that of having a very specific tank construction.

The present invention thus relates to a stationary heating installation comprising a heat pump, a first heat sink and a second heat sink in which a heat pipe couples the heat pump with the second heat sink so as to extract calories from the gases. hot exhaust from the compressor of the heat pump and transmit them to said second heat sink.

A principle of the invention is therefore a coupling by a heat pipe between the heat pump for heating premises and an application requiring a higher temperature, such as a domestic hot water tank or a container for heating. water traveled by a heat exchanger for heating sanitary water.

As is known, a heat pipe is a very simple and effective device in the form of closed pipe containing a liquid filling determined allowing a large heat transmission by evaporation of the liquid. Such a heat pipe, with the hot source at the bottom and the thermal receiver at the top, has the advantage of functioning as a thermal diode, that is to say, to mainly transmit the calories only in the direction of the hot source towards the thermal receiver and to prevent, with thermal conductions, a transfer of calories from the thermal receiver if the temperature thereof is greater than that of the hot source. Since the transmission of calories is made from the moment when the liquid in contact with the hot source can boil, such a heat pipe also has the advantage of transmitting heat to the heat sink only as long as the temperature of the hot source is greater than a certain threshold, this threshold being adjustable by the pressure or, for a given pressure, determined by the nature of the liquid.

The coupling proposed in the context of this invention allows to take the hot source - in this case the compressed gas output of the compressor - only part of the calories (those stored as heat at high temperature) , to transmit them to a thermal receiver and to leave the rest of the calories available for another application - in this case heating the premises. This coupling thus allows a heat source to feed two different consumers, one of which receives heat only if, simultaneously, its temperature is lower than that of the hot source and the temperature of the hot source exceeds one threshold.

In a preferred embodiment, the invention can be used to obtain domestic hot water by taking a portion of the calories at the compressor output of a heat pump for heating a home. The advantages of the invention are as follows:

[0012] the overall efficiency of the installation is improved,

[0013] obtaining domestic hot water does not require a complex and controlled installation,

[0014] the efficiency of the compressor becomes a secondary criterion,

- The amount of heat taken for heating domestic hot water can be adjusted.

The following description, with reference to the accompanying drawing, all given by way of non-limiting example, will explain how the invention can be achieved.

FIG. 1 shows a schematic section of a stationary heating installation according to the invention. The reference numeral [1] designates the second thermal receiver intended to receive part of the heat pump's calories [6]. The second receiver is thermally isolated from the outside by an insulating envelope [5] and contains a mushroom-shaped reservoir [2] inside which the water intended for sanitary use is located. The sanitary water enters the tank via the inlet pipe [3a] and comes out, after having been heated by a water bath, through the outlet pipe [3b] situated at the top of the tank. The tank [2] is immersed in a container. In this configuration, the water [4] enveloping the tank [2] and being inside the container is never set in motion and the stratification of the water is well respected. The hottest water is at the top and the coldest water at the bottom. This explains the reason of the shape given preferentially to the tank [2]: the larger volume in the upper part makes it possible to store a certain reserve of domestic hot water ready to be used. It goes without saying that several other types of tanks (such as for example a tubular coil) are also suitable for carrying out the invention.

The reference numeral [6] indicates the heat pump for space heating. This can be decomposed into a compressor [6a], a second non-detailed part [6b] comprising among others the expander and the evaporator and a third non-detailed part [6c] constituting the first thermal receiver and allowing the heating of the premises. . The gas compressed by the compressor circulates in a duct [13] which passes through an exchanger [7a] forming part of the heat pipe [7]. The heat pipe is surrounded by insulation [10] not completely represented, so as not to lose the calories to the outside. The heat pipe [7] is partially filled, for example by means of a nozzle not shown, with a liquid [8] and a gas [14] at an adjustable pressure via a nozzle [11]. The upper part of the heat pipe consists of a blind pipe whose first part is thermally insulated from the outside and the second part of which penetrates the container [1a] to bathe in the water [4]. The container [1a] can also be equipped with an electrical resistance [15] or additional exchangers, such as for example an exchanger [12] which can be an exchanger for solar heat inputs. This last possibility represents an optimal solution to avoid starting the heat pump in summer. The skilled person may consider other variants such as for example a connection between the portion [6c] and the container [1a] to use water [4] - preferably that located in the middle or low parts due to temperature - as a thermal buffer for space heating.

When the heat pump is turned on for space heating, the compressor [6a] compresses the gas that enters the exchanger [7a] of the heat pipe under high pressure and at high temperature. The liquid [8], heated by the gas, reaches its boiling point and begins to boil. Its vapor then fills the tube [9] and, if the temperature of the water [4] surrounding the tube [9] allows it, condenses in the part of the tube immersed in the container [1a]. The condensed liquid then falls by gravity into the exchanger [7a].

The temperature from which the heat pipe must begin to transfer calories is determined by the nature of the fluids [8] and [14] (to a lesser extent) and by the pressure inside the heat pipe. Many combinations are possible and may be chosen by those skilled in the art. A possible combination is for example to take for liquid [8] acetone which boils under atmospheric pressure at 56 ° C, for gas [14] an inert gas such as carbon dioxide or nitrogen, and to wedge the internal pressure in the heat pipe at 56 ° C to 1 bar. Another possible and interesting combination for its simplicity is to use as liquid [8] water and to have as gas [14] air. Thus, it is sufficient, through the tip [11], to produce a certain depression to choose the temperature threshold from which the heat pipe operates. For example, if a vacuum pump connected to the nozzle [11] is used to bring the air pressure [14] to 100 mbar at room temperature, the water will start boiling from 45 ° C. The pressure inside the heat pipe may be monitored at any time by the addition of a pressure gauge [17] on the heat pipe or any other part connected to it. The person skilled in the art will have no difficulty in determining the parameters allowing the operation most appropriate to the situation.

In a preferred embodiment, the exchanger [7a] of the heat pipe must be placed lower than the septum passage between the pipe [9] and the container [1]. Thus, the return of the liquid [8] after condensation is done alone by simple gravity. However, one can imagine using a more advanced heat pipe, as it exists, allowing thanks to capillary fibers inside of it to raise a liquid against the gravity. In this case, the exchanger [7a] could very well be located at the same altitude or higher than the bulkhead crossing between the pipe [9] and the container [1a].

In a preferred embodiment, the portion [6c] of the heat pump is connected to the container [1a]. Thus, the volume of water [4] can serve as heat buffer to the heat pump and it can be started even when space heating is not requested but the price of the current is cheaper ( during the night for example). Part of the energy is then used to heat the upper part of the container [1a] for domestic hot water, and another part of the energy is used to heat the middle or lower part of the container [1a]. In this embodiment, the inputs [16b] and output [16a] connect the container [1a] with the heat pump, and more particularly its portion [6c].

If the temperature of the water surrounding the part of the tube [9] immersed in the container is higher than that of the vapor inside the tube [9], then the condensation inside this it can not happen. The pressure in the tube will then rise and the boiling temperature of the liquid [8] will rise to possibly reach and then exceed the temperature of the water surrounding the portion of the tube [9] immersed in the container. From there, the heat pipe will be functional again. If the boiling temperature fails to exceed the temperature of the water surrounding the portion of the immersed tube [9], which can occur if the water [4] has been heated by the submerged resistor, for example [15]. ], then the heat pipe will stop working and will stabilize at a temperature almost equal to the exit temperature of the gas output compressor. The pressure inside the heat pipe will then be the pressure for which the liquid [8] boils at the temperature of the gas output of the compressor. If under these conditions the liquid [8] is for example water and the gas output of the compressor reaches 85 ° C, the pressure inside the heat pipe will be less than 1 bar. Such pressure does not represent any security risk.

Even if the immersion of the heat pipe in the second thermal receiver is a preferred arrangement, it can very well be imagined, in the context of the invention, that the heat pipe does not cross the wall of the thermal receiver but that the calories released by condensation in the heat pipe are transmitted by conduction to the wall of the second thermal receiver (and thence to the contents) through direct contact with the heat pipe. The latter then remains outside the contents of the second thermal receiver. Such an arrangement may be of interest for heating a container in which the lamination of the water contained therein is not particularly desired. In practice, the upper part of the heat pipe may for example be welded to a portion of the outer surface of the second thermal receiver or directly end in a closed volume in contact with the wall of the second thermal receiver or forming a wall common with the second thermal receiver (for example a pocket under the second thermal receiver). Those skilled in the art will not be able to find many variants without departing from the scope of the present invention.

If, for the purposes of a specific installation, it is desired to be able to prevent the heat pipe from transmitting calories, it can be imagined that it is for example equipped with a valve to close it or that an intermediate device for retaining heat. water is added to prevent the condensed liquid from returning to the bottom of the heat pipe. The latter can also be simply emptied temporarily.

In order to increase the thermal reserve capacity of the container [1a], it is also possible to leave immersed in suspension in the water [4] pockets [18] containing a fusible material at a temperature of the order of 60 ° C, such as wax or paraffin. The heat is then stored as latent heat and returned to water as soon as its temperature falls below the melting temperature. Ideally, these pockets will have a lower density than water so that they tend to stay in the upper part of the container [1a], where the desired temperature is greatest.

Claims (9)

Stationary heating plant comprising a heat pump [6], a first heat receiver [6c] connected to this heat pump [6], and a second heat receiver [1] in which a heat pipe [7] couples the pump heat [6] with the second heat receiver [1] so as to extract heat from the hot gases exiting the compressor of the heat pump and to transmit them to said second thermal receiver [1]. 2. Installation according to claim 1 wherein the first thermal receiver [6c] is a space heating water circuit and the second thermal receiver [1] is constituted by a container [1a] and its thermal insulation [5] and containing hot water for direct use as domestic hot water or for heating domestic hot water via a tank [2]. 3. Installation according to claim 2 wherein the container [1a] is filled with water from the space heating water circuit [6c]. 4. Installation according to claim 1 wherein the heat pipe is constituted by a pipe [9] connected at its base to an exchanger [7a] receiving the calories of the compressed gas leaving the compressor [6a] of the heat pump [6] and whose upper terminal part is blind and immersed in water [4] of the second thermal receiver [1]. 5. Installation according to claim 1 wherein the heat pipe is constituted by a pipe [9] connected at its base to an exchanger [7a] receiving the calories of the compressed gas leaving the compressor [6a] of the heat pump [6] and whose upper part is such that the calories restored by the condensation in the heat pipe [7] are transmitted by conduction to a portion of the outer surface of the second thermal receiver [1] and not directly to its contents. 6. Installation according to claim 4 wherein a tip [11] connected to the heat pipe [7] allows to connect a pump for varying the pressure inside the heat pipe. 7. Installation according to claim 2 wherein the water container [1a] is further equipped with a submerged heat exchanger [12] for solar heat inputs and / or a booster electrical resistance [15]. 8. Installation according to claim 1 wherein the heat pipe [7] is thermally insulated from the outside. 9. Installation according to claim 1, wherein pockets [18] containing a fusible material at a temperature below 80 ° C are immersed in the second heat receiver [1] for storing heat in the form of latent heat and restore it. to water as soon as its temperature drops below the melting temperature.