WO1981000444A1

WO1981000444A1 - Underground tank used as a water supply tank for heat pumps

Info

Publication number: WO1981000444A1
Application number: PCT/EP1980/000064
Authority: WO
Inventors: L Reitmaier
Original assignee: L Reitmaier
Priority date: 1979-08-06
Filing date: 1980-07-30
Publication date: 1981-02-19
Also published as: BR8008779A; IT1132341B; EP0032935A1; GR69747B; ES8102741A1; YU194480A; IT8024037A0; ES494033A0; JPS56501103A

Abstract

A heat pump (2) intended for heating is connected to an underground water supply tank (10). This tank is heat insulated by a hard foam layer (16). The fluid returned from the heat pump runs through a bundle of tubes (17) coiled on the hard foam layer (16). The tubes (17) bring the return fluid in contact with the earth so that the cold return fluid heats up to the mean temperature of the surrounding earth before it returns to the water supply tank (10).

Description

Feed water tank for heat pumps designed as an underground tank.

The invention relates to a feed water tank designed as an underground tank for heat pumps of a heating system, in which the outside of the tank is provided with a layer of heat-insulating material, in particular a rigid foam.

In heating systems with a heat pump, it is known that the feed water of the heat pump is heated up via a heat exchanger or directly into a solar circuit. The heated water can be fed directly to the heat pump. To increase the heat capacity and heating time, however, excess heated water is led into a feed water tank, from which the heat pump can draw in if necessary. To save water, the heat pump fluid is usually conducted in a closed circuit. When the term "water" is used below, it means any pluid suitable as a heat carrier, ie water or refrigerant or other known pluids with additives.

It is known to heat the feed fluid of the heat pump via other, in particular natural, heat sources than the solar radiation. So large coils have already been laid at a sufficient depth in the ground in order to supply the heat pump with geothermal energy. The return fluid from the heat pump is fed to the pipe system laid in the ground for reheating. Hybrid systems are also already known in which the heat pump can extract heat from various natural heat sources and possibly also from an additional heater, with an automatic device switching the feed circuit from one heat transfer medium to the other or combining both. There is an unlimited amount of heat available in geothermal energy. For practical use, especially for private heating purposes, however, large exposed areas are required, which are required for laying the pipe systems in the ground. Existing gardens or crops must be destroyed in order to subsequently lay such coils. In addition, there is the risk of frost damage in very harsh winters in a large-scale arrangement despite being laid sufficiently deep, whereby it should be noted that the return water from the heat pump has cooled considerably.

It is an object of the invention to develop a feed water tank of the type specified in the introduction in such a way that it offers the possibility of the heat pump in a simple and inexpensive manner over long periods of time and without the need for maintenance

This object is achieved in that the heat-insulating layer of the underground tank is surrounded by a fluid-flowable element and this element is encased by a jacket made of a mechanically resistant material with good thermal conductivity, the element through which the fluid flows between the return of the heat pump the feed water tank can be switched on in terms of flow.

The feed water tank can advantageously, as in conventional systems, also serve as a storage tank for feed fluid warmed up by other, in particular natural, heat sources. This fluid can draw the heat pump as feed fluid from the feed water tank to bridge heating times in which the natural heat source, e.g. from a solar circuit, heat is not available or is not available in sufficient quantities.

The invention now provides that the return water of the heat pump is first brought into intimate heat transfer contact with the ground to absorb heat from the ground. The return water is then returned to the feed water tank. The arrangement is extremely space-saving and simple, can be prefabricated in the factory and installed in the ground without extensive earthwork. The return fluid is in thermal contact with the ground via the mechanical protective jacket. As a good heat conductor, this ensures thermal contact between the element through which it flows and the ground. At the same time, it protects the feed water tank and the element through which the fluid flows both against mechanical influences and against the chemical and physical influences of the surrounding earth. In particular, the load of the container is transferred to the supporting soil via the protective jacket. Concrete has proven to be a very cheap and effective material for the protective jacket, with which the feed water container, the insulating layer thereon and the coil, preferably wound as a coil or hose, and embedded by the fluid, are embedded. The concrete can additionally be roughened on its outside, at least in the outer area it can be porous or it can be provided with ribs in order to increase the heat transfer. The concrete can also have admixtures that increase the thermal conductivity.

The flowed-through element can consist of metal or of another sufficiently thermally conductive material, such as plastic. The element is preferably designed as a layer of tube or tube bundles, the tube windings being wound tightly onto the heat-insulating rigid foam. With a sufficient size of the feed water tank and with a sufficient winding length, it can be ensured that even very cold return water warms up to the average earth temperature in a frost-proof depth. In this way, geothermal energy can be introduced into the heat circuit of the heat pump in a simple but, above all, space-saving manner. The fluid in the Feed water tank is preferably water provided with an antifreeze. Preferably, a plurality of hermetically sealed small containers, in particular spherical, made of elastically stretchable material can be provided in the interior of this water filling, which contain a pressure-resistant liquid that is not protected against frost, such as water without anti-freeze. Through this training, the heat can be removed from the feed water by utilizing the water provided in the small containers when the water freezes, thus achieving a better effectiveness of the arrangement.

The measures according to the invention are suitable for any type of feed water tank designed as an underground tank. A container shape is preferred which offers a sufficiently large surface area for winding the flowable element. Elongated cylindrical containers are preferred, since they also considerably facilitate the application of the rigid foam, but above all the winding up of the coils. The coils: can be wound onto the rigid foam by machine. The elongated container can be installed horizontally in the ground. This arrangement has the advantage that, with sufficient length and sufficient capacity, the excavation pit need only have a limited depth. In many cases, however, the elongated container is preferably installed vertically. As a result, a much greater depth of the excavation pit is required, but the transverse dimensions of the excavation pit in the area of the earth's surface can be kept very small, so that this type of installation is particularly suitable for retrofitting the underground tank.

In both cases, it can be particularly advantageous if the feed water tank or at least parts of it are sunk into the normal groundwater area.

Instead of concrete, you can also use it as an external mechanical protective jacket other thermally conductive and mechanically strong materials can be used. Concrete has proven to be particularly suitable for reasons of strength, thermal conductivity, the possibility of adding admixtures, for reasons of cost and for reasons of high resistance to physical and chemical influences in the ground.

If, in a preferred embodiment, the elongated tank is arranged upright and installed, it preferably has at its lower end a base which projects downward from the tank bottom. This has the advantage that the load of the container and its load can be placed directly on the supporting floor in a much more reliable manner and with the relief of the hard foam layer, the pipe coils and the jacket. In addition, the installation depth can be increased as the base extends into greater depths of the ground. This has the advantage that the location of flowed elements can also be provided over the greater part of the height of the base. The vertical installation enables an excavation pit of small transverse dimensions. Without changing the dimensions of the actual container, the length of the structural unit can be influenced via the pedestal in such a way that at least the pedestal extends into areas of the normal groundwater level. The base also gives you the option of significantly increasing the total length and contact area of the flowed elements with the ground. This type of installation therefore offers a particularly high heat absorption capacity in confined spaces.

To facilitate installation, the standing installation unit can be designed to have a conically decreasing diameter, at least in the area of the base, so that the formwork-free installation of the excavation pit, even with a large installation depth, and easy installation of the installation unit. The formation of the foot area also offers the possibility of between the foot and the actual container to arrange at least parts of the pipe windings exposed, since they can be accommodated in the space between the container and the foot with adequate protection. Of course, this is only possible if the pipe coil is made of a resistant material and there is no fear that corrosion of the pipe coil can be expected from the groundwater or surrounding soil. The coils can vary in shape and material in the various areas of the length of the structural unit.

The invention is explained in more detail below with the aid of a schematic drawing using two exemplary embodiments.

Show it:

Fig. 1 shows a portion of a hori zontally arranged feed water tank designed as an underground tank according to the invention with the associated facilities and

Fig. 2 shows a vertical section through a preferred embodiment of the underground tank.

In Fig. 1, 1 indicates a solar circuit, which is representative of other natural heat sources via an inlet line 5 and a feed water line 4, directly or indirectly connected to the feed water inlet line 7 or the feed water return line 6 of a heat pump 2. This can be driven by a motor 3. A heat exchanger can be arranged between the circuit of the natural heat source and the circuit of the heat pump. Instead of water, any other fluid suitable for this purpose can be provided as a heat carrier. The line connections can be switched by valves 8 and 9. A riser 12 is connected to the feed line 7 of the heat pump 2, which is led through the cover 14 of the dome 13, which has thermal insulation 15, of an underground tank 10 installed sufficiently deeply sunk in the ground into the interior of the underground tank designed as a feed water container. The heat pump can therefore Remove fluid directly from the line 4 connected to the solar system 1 or directly from the feed water tank 10 via the riser 12. Instead of the feed line 7, the line 4 can also be connected to the filling line 11 projecting into the feed water container, so that the fluid heated in the solar system 1 can be stored in the feed water container 10 and removed from the heat pump 2 via the riser 12 if necessary.

The feed water tank 10 can be made of metal or plastic. It preferably has a length that is large compared to its diameter. In the exemplary embodiment according to FIG. 1, its axis is arranged horizontally. A sufficiently thick layer of, for example, 10 cm of a heat-insulating material, in particular hard foam, is provided on its outside, which can be foamed directly onto the feed water tank jacket. The thickness is such that the heat losses from the feed water tank are negligible.

A layer of elements through which a fluid can flow is arranged directly on the outside of the hard foam layer 16. It can be a ring jacket of small thickness. However, the layer preferably consists of tube or hose bundles 17 wound onto the hard foam layer 16. These can consist of metal or of a sufficiently thermally conductive plastic. The dimensions of the pipes or hoses and their winding density on the hard foam layer 16 are selected so that optimum heat absorption from the surrounding earth takes place through the heat transfer fluid flowing through the elements.

The flowable elements wound on the rigid foam 16 are connected on the one hand via line 19 to the valve 8, so that the return fluid from the line 6 of the heat pump 2 is introduced directly into the flowable elements 17 can be. The other end of the flowable elements 17 is connected to the filling line 11 via a branch line 20, so that the return fluid can enter the feed water tank after the geothermal energy has been absorbed. Practical tests have shown that even with long operating times of the heat pump 2 and greatly reduced temperature of the return fluid in the line 6 of the heat pump, the fluid heats up as it flows through the elements 17 to close to the mean ambient temperature of the ground. As a result, during the corresponding switching of the feed fluid circuit, geothermal heat is continuously fed into the feed water tank, from which the heat pump can take advantage of this heat.

It is essential for trouble-free operation over years of use that the elements through which the fluid can flow are protected against any mechanical, chemical or physical interference. An outer protective jacket 18 made of mechanically strong and sufficiently thermally conductive material is used for this purpose. The jacket can be made of plastic, provided that appropriate measures, e.g. a certain porosity, sufficient thermal conductivity is ensured. However, the jacket 18 preferably consists of a concrete. Fillers can be mixed with this to improve the thermal conductivity. The concrete can also be porous to absorb a certain amount of moisture. To enlarge the outer peripheral surface, the outer surface can also be roughened or provided with ribs or the like.

The feed water tank described can be prefabricated in the form shown in the factory and easily installed as a unit sunk sufficiently deep into the ground, the construction pit required for this having only a relatively small surface area. Installation in a depth corresponding to the normal groundwater area can be particularly advantageous. In order to be able to utilize the heat released during the freezing of water via the heat pump, the feed water container can be filled with water provided with antifreeze and a plurality of small containers 25, in particular spherical, can be inserted into this filling. These small containers are filled with water without antifreeze and are hermetically and pressure-resistant and, if necessary, elastically expandable, so that the heat can be removed from the feed water container to below freezing point.

Fig. 2 shows a preferred embodiment of an underground tank in the form of a structural unit which can be prefabricated in the factory and lowered into an excavation pit. The unit is labeled 101. The elongated feed water tank 102 is arranged upright and installed in this embodiment. All the necessary connections, only one of which is shown, are routed into the interior of the container through the upper container lid. This may also include cables for monitoring devices. In the illustration, only the filling line 111 is shown, which is connected to the return line 107 connected to the heat pump. A foot section of a noticeable height is connected to the closed bottom of the feed water tank 102. In the example shown, this can consist of a cylinder 104 welded to the bottom of the feed water container, which has a base plate 105 at its lower free end. The feed water tank is continuously thermally insulated from the outside via a hard foam layer 103. A pipe winding 108 with relatively narrow turns is wound onto this hard foam layer 103. All pipe turns are only indicated in section in the right half of the figure. These pipe turns are connected to the return line 7 of the heat pump at the upper end of the feed water tank. The pipe windings continue in the area of the foot section in the form of a tight winding pack 109. This preferably takes up the entire free space between the bottom of the container and the stand plate 105. The lower end of these turns is led upward again with a few turns 110 of a high gradient and connected to the filling line 111 of the feed water tank.

The height 116 of the base 106 is dimensioned as a function of the installation depth 114 of the upper side of the installation unit 101 below the surface of the earth and as a function of the height 115 of the feed water tank itself, so that when installed in a construction pit, the foot area extends as far as possible into the usual one Groundwater sticks out. With 117 the soil layer supporting the structural unit is designated.

At least above the height of the feed water tank, the pipe windings are embedded in a jacket 105 made of mechanically resistant material. If this coat is made of concrete, it can have a thickness of about 15 cm. With correspondingly favorable conditions and appropriate choice of material, the pipe windings 109 can be arranged exposed in the foot area so that they are in free contact with the groundwater. There is no fear of mechanical stress on the lines 109 in this area, since they are arranged in a protected manner in the annular space between the bottom of the container and the standing plate. For reasons of long operating times without maintenance, however, it is recommended to also embed the pipe windings 109 in a concrete jacket 125 or the like. If the stand extends into the groundwater, it can be advantageous to make it permeable to the groundwater. For this purpose, windows or channels 112 can be provided in the foot section, which are in flow connection with a central opening 113 of the foot. Instead of the pipes 109 in the foot section, other flowable elements or chamber sections can also be provided in the foot section.

The standing arrangement according to FIG. 2 offers the advantage of being large Installation depth with small surface dimensions of the excavation pit required for installation. The embodiment is therefore particularly suitable for retrofitting, in which existing systems, such as gardens, crops or the like, are only slightly affected. In order to further facilitate installation, the foot section 106 is conically tapered downwards. The entire structural unit including the feed water container 102 can also be designed to taper downward.

The arrangement described in FIG. 1 or 2 can optionally also be used for cooling rooms in summer. For this purpose, the arrangement described, consisting of the feed water tank and the pipe batches wound on it, can be connected directly to a heating system (not shown), which is supplied with heat in cold times via the heat pump, so that the usual heating system is removed from the rooms in hot times Absorb heat and release it to the surrounding earth via the fluid and the underground tank. This will significantly expand the benefits of the new underground tank.

Claims

Expectations

1. As an underground tank trained feed water tank for heat pumps of a heating system, in particular for residential purposes, in which the tank outside with a layer of a heat-insulating material, in particular a rigid foam, is seen ver, characterized in that one of one on the heat-insulating layer (16) of the underground tank Fluid-flowable element (17) of a heat absorption device is applied and this is encased by a jacket (18) made of a mechanically resistant material with good thermal conductivity, the fluid-flowable element (17) flowing between the return (6, 19) of the heat pump ( 2) and the underground tank (10) can be switched on.

2. Feed water tank according to claim 1, d a d u r c h g e k e n e z e i c h n e t that one or more layers of a pipe or hose winding (17) through which the fluid can flow are wound onto the layer (16).

3 «Feed water tank according to claim 1 or 2, so that the element (17) through which the fluid flows is enclosed by a concrete jacket (18).

4. feed water tank according to one or more of claims 1 to 3, d a d u r c h g e k e n n z e i c h n e t that the element (17) through which the fluid can flow can optionally be connected to the heat pump return line (6, 19).

5. feed water tank according to one or more of claims 1 to 4, characterized in that the filling space of the container with a freeze protected against Ge freezing fluid and several in this one filled sealed small containers (25) is filled, in which a freezable liquid is provided.

6. feed water tank according to one or more of claims 1 to 5, characterized in that the elongated tank (102) is arranged upright and is provided at its lower end with a base (106) projecting downward from the tank bottom, the position of flowable elements ( 108) preferably also extends over the greater part of the height (116) of the base.

7. feed water tank according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the base (106) is designed for a flow of ground water or the like. Opened (112, 113).

8. feed water tank according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the pipe windings or the like. In the foot section from the outside are freely flowable through the groundwater.

9. feed water tank according to claim 7, so that the foot section has a casing made of mechanically resistant material, in which openings or windows (112, 113) are provided.

10. feed water tank according to one or more of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the flow-through elements from the foot portion (106) in the jacket (105) to the ceiling portion (103) returned and there are connected to the tank fill line (111).