Ground heat exchanger

Abstract

To provide an underground heat exchanger which can increase a flow rate of a heating medium at least in one pipe out of an outgoing pipe and a returning pipe, without performing special processing such as joining a pipe in the middle of a path of the heating medium, and which can improve heat conversion efficiency.SOLUTION: In an underground heat exchanger 10, a heating medium S is circulated in a pipe buried to a deep layer part H underground, and heat exchange is performed with the ground 1, and it includes: an outgoing pipe 11 for flowing the heating medium S to the deep layer part H side; and a return pipe 12 for flowing the heating medium S which has reached the deep layer part H side going through the outgoing pipe 11 to an earth surface 1a side. At least one pipe out of the outgoing pipe 11 and the return pipe 12 includes an insertion pipe 13 at a position corresponding to a shallow layer part L underground inside.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ground heat exchanger that performs heat exchange with the ground.

Background Art

[0002] U-shaped ground heat exchangers are widely adopted. A heat medium such as water is circulated in a pipe buried in the ground to dissipate the heat discharged from an air conditioner or the like, or to extract the heat from the ground and supply it to the air conditioner, thereby efficiently operating the air conditioner. As this type of ground heat exchanger, for example, there is one described in Patent Document 1. The ground heat exchanger described in Patent Document 1 constitutes a U-shaped pipe with a forward pipe, a return pipe, and a U-shaped bent pipe disposed in the ground. Then, a part of the return pipe is reduced in diameter to increase the flow rate of the heat medium in the return pipe, and the reduced-diameter portion of the return pipe is surrounded by a heat insulating material to improve the heat conversion efficiency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional ground heat exchanger, by reducing the diameter of a part of the return pipe, the flow rate of the heat medium in the return pipe can be increased. However, in order to improve the heat conversion efficiency, a heat insulating material surrounding the reduced-diameter portion of the return pipe is indispensable, which increases the cost accordingly.

[0005] Therefore, the present invention has been made to solve the above-described problems, and it is possible to directly use a widely used U-shaped pipe, and without joining the pipes in the middle or performing special processing, the flow rate of the heat medium in at least one of the forward pipe and the return pipe can be increased, and an object of the present invention is to provide a ground heat exchanger capable of obtaining a heat insulation effect without using a heat insulating material.

Means for Solving the Problems

[0006] The present invention is a ground heat exchanger that circulates a heat medium inside a pipe buried to a deep part of the ground and performs heat exchange with the ground. The ground heat exchanger includes a forward pipe for flowing the heat medium toward the deep part side, a return pipe for flowing the heat medium that has reached the deep part side through the forward pipe toward the ground surface side, and a connecting pipe that connects an end portion in the pipe axis direction of the forward pipe and an end portion in the pipe axis direction of the return pipe with a predetermined interval therebetween. At least one of the forward pipe and the return pipe is characterized by having an insertion pipe at a position corresponding to a shallow part of the ground inside.

Effects of the Invention

[0007] According to the present invention, by inserting an insertion pipe at a position corresponding to a shallow part of the ground inside at least one of the forward pipe and the return pipe, without joining the pipes in the middle of the heat medium path or performing special processing, the flow rate of the heat medium in at least one of the forward pipe and the return pipe can be increased, and the heat transfer rate can be reduced to obtain a heat insulation effect. Thereby, the heat conversion efficiency of the ground heat exchanger can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] FIG. 1 is a side view showing a ground heat exchanger according to the first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the portion indicated by reference sign A in FIG. 1.

[0011] As shown in FIG. 1, the ground heat exchanger 10 circulates a heat medium S inside a U-shaped pipe composed of a forward pipe 11, a return pipe 12, and a connecting pipe 14 buried to the deep part H of the ground, and performs heat exchange with the ground 1. Here, a liquid such as water or antifreeze is used as the heat medium S. That is, the ground heat exchanger 10 circulates a heat medium S such as water in a U-shaped pipe buried in the ground, radiates the heat discharged from an air conditioner or the like, or extracts the heat from the ground and supplies it to the air conditioner, thereby efficiently operating the air conditioner. In FIG. 1, reference sign H indicates a deep part about 10 m or deeper where the temperature of the ground is constant throughout the year, and reference sign L indicates a shallow part shallower than 3 m where the temperature of the ground is likely to change seasonally.

[0012] As shown in FIG. 1, the forward pipe 11 is for flowing the heat medium S toward the deep part H of the ground 1, and is formed in a cylindrical shape made of high-density polyethylene having high long-term hydrostatic strength.

[0013] As shown in FIGS. 1 and 2, the return pipe 12 is for flowing the heat medium S that has reached the deep part H side through the forward pipe 11 toward the ground surface 1a side, and is formed in a cylindrical shape made of high-density polyethylene having high long-term hydrostatic strength. Further, the return pipe 12 has an insertion pipe 13 at a position corresponding to the shallow part L inside the ground. That is, the return pipe 12 inserts the insertion pipe 13 to a location (position) that is easily affected by the temperature change of the outside air near the ground surface or its vicinity, or a location (position) that is easily affected by the temperature of the heat medium S in the forward pipe 11.

[0014] Since the insertion pipe 13 is required to have a low thermal conductivity and sufficient durability, it is formed in a cylindrical shape made of high-density polyethylene having a high long-term hydrostatic pressure strength, which is the same material as the return pipe 12, and is fixed inside the return pipe 12 by adhesion of an adhesive (not shown). Further, the outer diameter of the insertion pipe 13 is substantially equal to the inner diameter of the return pipe 12, and may be slightly smaller than the inner diameter of the return pipe 12 so as not to hinder insertion. In this case, in order to make the outer periphery of the insertion pipe 13 be inserted into the inner periphery of the return pipe 12 with almost no gap, an adhesive is applied to the outer periphery of the insertion pipe 13, and the insertion pipe 13 is inserted and fixed to a position corresponding to the shallow layer portion L in the ground inside the return pipe 12 before the adhesive dries. That is, the positions of the upper end portion (the other end portion in the pipe axis direction) 12a of the return pipe 12 and the upper end portion (the other end portion in the pipe axis direction) 13a of the insertion pipe 13 are aligned, and the insertion pipe 13 is fixed so as not to fall downward from inside the return pipe 12. Further, a conical surface (inclined surface) 13b for heat medium rectification is formed at the lower end portion of the insertion pipe 13.

[0015] As shown in FIG. 1, the connecting pipe 14 is formed in a U shape in a cylindrical shape made of high-density polyethylene having a high long-term hydrostatic pressure strength, and connects the lower end portion (the end portion in the pipe axis direction) 11b of the supply pipe 11 and the lower end portion (the end portion in the pipe axis direction) 12b of the return pipe 12 with a predetermined interval therebetween. In addition, when the supply pipe 11 and the return pipe 12 are integrally formed in a U shape, the connecting pipe 14 becomes a connecting portion.

[0016] As shown in FIG. 1, the U-shaped ground heat exchanger 10 is inserted into the excavation hole 2 vertically formed in the ground 1, and a filler 3 such as sand is filled between the excavation hole 2 and the ground heat exchanger 10. Thereby, heat exchange is performed between the heat medium S of the ground heat exchanger 10 and the ground 1 through the filler 3.

[0017] According to the ground heat exchanger 10 of the first embodiment as described above, by inserting the insertion pipe 13 at a position corresponding to the shallow layer portion L in the ground inside the return pipe 12, it is possible to connect the pipes in the middle of the path of the heat medium S, or to increase the flow rate of the heat medium S in the return pipe 12 without performing special processing on the return pipe 12.

[0018] Furthermore, by inserting the insertion pipe 13 at a position corresponding to the shallow layer L in the ground within the return pipe 12 and increasing the wall thickness of the insertion pipe 13, the heat insulation effect is enhanced, heat loss can be reduced, and the heat insulation effect can be further increased without using a conventional heat insulating material. As a result, the heat conversion efficiency of the ground heat exchanger 10 can be further improved. In addition, by forming a conical surface 13b for heat medium rectification at the lower end of the insertion pipe 13, the heat medium S can be smoothly flowed to the opening side above the return pipe 12. Furthermore, by inserting the insertion pipe 13 into the return pipe 12, the curling at the shallow layer L is alleviated, and the connection work of the pipes on the ground becomes easier.

[0019] FIG. 3(a) is an enlarged cross-sectional view corresponding to the portion indicated by reference numeral A in FIG. 1 of the ground heat exchanger according to the second embodiment of the present invention, and FIG. 3(b) is an enlarged cross-sectional view corresponding to the portion indicated by reference numeral A in FIG. 1 of a modified example of the ground heat exchanger.

[0020] The ground heat exchanger 10 according to this second embodiment is different from that of the first embodiment in that the convex portion 13c provided at the upper end portion 13a of the insertion pipe 13 is locked to the concave portion 12c provided at the upper end portion 12a of the return pipe 12 to fix the insertion pipe 13 within the return pipe 12. Since other configurations are the same as those of the first embodiment, the same reference numerals are assigned to the same components and detailed descriptions are omitted.

[0021] In the ground heat exchanger 10 according to this second embodiment, as shown in FIG. 3(a), by locking the convex portion 13c of the insertion pipe 13 to the concave portion 12c of the return pipe 12 to fix the insertion pipe 13 within the return pipe 12, the same operations and effects as those of the first embodiment are achieved. In particular, by the engagement between the concave portion 12c and the convex portion 13c, the insertion pipe 13 can be reliably prevented from falling off.

[0022] Also, as in the modified example shown in FIG. 3(b), a concave portion 12c having an inclined surface 12d may be provided at the upper end portion 12a of the return pipe 12, a convex portion 13c having an inclined surface 12d may be provided at the upper end portion 13a of the insertion pipe 13, and the insertion pipe 13 may be fixed within the return pipe 12 by bringing the inclined surfaces 12d and 13d into contact (locking).

[0023] FIG. 4 is an enlarged cross-sectional view corresponding to the portion denoted by reference numeral A in FIG. 1 of the ground heat exchanger according to the third embodiment of the present invention.

[0024] The ground heat exchanger 10 of this third embodiment is different from that of the first embodiment in that the wall thickness of the insertion pipe 13 is formed thicker as it approaches the ground surface 1a side. Since other configurations are the same as those of the first embodiment, the same reference numerals are assigned to the same components and detailed descriptions thereof are omitted.

[0025] In the ground heat exchanger 10 of this third embodiment, the wall thickness of the insertion pipe 13 is formed thicker as it approaches the ground surface 1a side (the inner peripheral surface 13e of the insertion pipe 13 is formed in a conical surface shape with a smaller diameter upward), so that the same operations and effects as those of the first embodiment are achieved. That is, the inner diameter of the insertion pipe 13 is determined by the required flow rate of the heat medium S, but since it is more easily affected by the outside air temperature as it approaches the ground surface 1a side, the inner diameter is gradually narrowed toward the ground surface 1a side.

[0026] In addition, according to each of the above embodiments, the forward pipe, the return pipe, the insertion pipe, and the connecting pipe are made of high-density polyethylene, but their materials are not limited to this. For example, thermoplastic resins such as normal-density polyethylene may be used, or materials other than resins may also be used. Further, since the insertion pipe is stored inside the return pipe, the deterioration factors from the outside of the insertion pipe are fewer than those of the return pipe, so it may be made of relatively inexpensive vinyl chloride resin.

[0027] Further, according to the first embodiment, the insertion pipe is fixed by adhering it to the inside of the return pipe with an adhesive, but the insertion pipe may be fixed inside the return pipe by heat welding.

[0028] Furthermore, according to each of the above embodiments, the insertion pipe is inserted into the return pipe of the ground heat exchanger, but the insertion pipe may be applied to other than the return pipe, such as the forward pipe, the double pipe, the spiral tube, etc.

Explanation of Reference Numerals

[0029] 1 Ground 1a Ground surface 10 Ground heat exchanger 11 Forward pipe 11b Lower end (end in the pipe axis direction) 12 Return pipe 12a Upper end (the other end in the pipe axis direction) 12b Lower end (end in the pipe axis direction) 12c Concave portion 13 Insertion pipe 13a Upper end (the other end in the pipe axis direction) 13b Conical surface (inclined surface) 13c Protrusion 14 Connecting pipe S Heat medium H Deep underground layer L Shallow underground layer

Claims

1. A ground heat exchanger that circulates a heat medium inside a pipe buried to a deep part underground and performs heat exchange with the ground, A forward pipe for flowing the heat medium to the deep part side, A return pipe for flowing the heat medium that has reached the deep part side through the forward pipe to the ground surface side, and is provided with, At least one of the forward pipe and the return pipe has an insertion pipe at a position corresponding to the shallow part of the underground inside, The ground heat exchanger is characterized in that the wall thickness of the insertion pipe is formed thicker as it approaches the ground surface side.

2. The ground heat exchanger according to Claim 1, The insertion pipe is fixed inside at least one of the forward pipe and the return pipe by adhesion or heat welding. The ground heat exchanger is characterized by this.

3. The ground heat exchanger according to Claim 1, At least one of the forward pipe and the return pipe is provided with a recess at the other end in the pipe axis direction, The insertion pipe is provided with a convex portion that is locked to the recess at the other end in the pipe axis direction. The ground heat exchanger is characterized by this.

4. The ground heat exchanger according to Claim 1, The insertion pipe is provided with an inclined surface for heat medium rectification at the end in the pipe axis direction. The ground heat exchanger is characterized by this.

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