WO2018105629A1

WO2018105629A1 - Large-tube horizontally-inclined convection-type ground heat exchanger, large-tube horizontally-inclined convection-type ground heat exchanging device, and installation method therefor

Info

Publication number: WO2018105629A1
Application number: PCT/JP2017/043711
Authority: WO
Inventors: 久生山野辺
Original assignee: 久生山野辺
Priority date: 2016-12-05
Filing date: 2017-12-05
Publication date: 2018-06-14
Also published as: JP2018091559A; JP6170228B1

Abstract

Provided is a ground heat exchanger that improves heat-transfer efficiency from the earth, is smaller in size, occupies less surface area, has reduced installation costs and operation costs, and can be installed in a narrow piece of land.　A large-tube horizontally-inclined convection-type ground heat exchanger according to the present invention is characterized in that: said ground heat exchanger is a straight metal tube embedded in the ground in an inclined and horizontal manner; both ends of said straight tube are respectively closed off by two end surfaces perpendicular to the long axis thereof; an upper portion of an upper end surface provided to the higher of the two end surfaces and a lower portion of a lower end surface provided to the lower of the two end surfaces are respectively provided with an upper-portion heat medium port and a lower-portion heat medium port; the cross-sectional area of the interior of said straight tube is 314 cm² or more; the ratio of the distance and height difference between the upper end surface and the lower end surface is in the range of 3:1 to 100:1; and a concrete layer or mortar layer is provided around said straight tube.

Description

Horizontally inclined convection type underground heat exchanger with large horizontal pipe, horizontal inclined type convective underground heat exchanger for horizontal pipe, and installation method thereof

TECHNICAL FIELD The present invention relates to a thick horizontal tube inclined convection type underground heat exchanger, a large horizontal tube inclined convection type underground heat exchanger, and an installation method thereof, and more specifically, a unit of an underground heat exchanger. Large pipe horizontal inclined convection type underground heat exchanger, large pipe horizontal inclined convection type ground, with increased heat exchange per length and reduced equipment footprint, installation cost, and operating cost The present invention relates to an intermediate heat exchange device and an installation method thereof.

In recent years, as one of the renewable energies, use of geothermal heat to transfer heat energy from the ground by circulating a primary heat medium such as water, brine, antifreeze, ethanol, carbon dioxide, etc. in a pipe buried underground A closed line type geothermal heat pump system is attracting attention, which includes a heat exchanger and uses the ground heat energy possessed by the ground by moving it to the secondary heat exchanger.

This geothermal heat pump can extract more heat energy than the power consumed by the system from the ground and supply it to the loader, and the consumed ground heat energy is replenished from the ground. It is a use and has the feature that pollution to the natural environment does not occur.

In addition, compared to solar and wind power generation, which are renewable energies, are greatly affected by weather, seasons, and sunshine hours, the heat pump system using geothermal heat has a substantially constant temperature throughout the year. Since it is not affected by the weather, it has the feature that it can be operated stably throughout the year.

The heat exchanger using underground heat can be roughly divided into, for example, a vertical type in which a heat exchange pipe having a diameter of 34 mm is inserted 50 to 150 m into the ground, and a horizontal type in which a heat exchange pipe is provided horizontally at a few meters underground, There are two types. In the United States, systems using horizontal underground heat exchangers have become popular for general housing. However, in order to provide a horizontal underground heat exchanger using a conventional pipe having a diameter of 34 mm, a large area is required.

On the other hand, in Japan, where the land is small, vertical type underground exchangers have been mainly used in the past, but there is a problem that a great deal of cost is required to dig deep vertical holes in the ground. An underground heat exchanger with a large horizontal pipe type heat exchanger that can be installed even in a small land has been disclosed, but an underground heat exchanger using a large-diameter pipe has a water layer with a different temperature difference inside the pipe. As a result, the heat transfer efficiency was lowered and the performance was not satisfactory (for example, see Patent Document 1). In order to increase the heat transfer efficiency, it is necessary to provide fins and stirring means in the pipe (for example, see Patent Document 2).

Furthermore, the heat pump system using geothermal heat has a problem that the thermal resistance in heat conduction of energy from the ground to the heat medium is large. In order to cope with this problem, a ground heat heat pump system (see, for example, cited document 3) in which a hole excavated for inserting a pipe of a vertical heat exchanger is backfilled with concrete has been disclosed. This system could increase the amount of heat exchange per unit, but it could not reduce the installation costs.

JP 2006-220402 A JP 2009-287914 A Japanese Patent No. 5590365

The present invention has been devised to solve such a problem, and provides a ground heat exchanger having a large heat conduction amount per unit pipe length by improving the heat transfer efficiency from soil to a heat medium, and is narrow. The objective is to provide a convection type underground heat exchanger that can be installed at low cost even on land.
Moreover, this invention makes it a subject to provide the underground heat exchange apparatus which reduced the installation cost and the operating cost by reducing the apparatus in size.
Furthermore, this invention makes it a subject to provide the installation method of the underground heat exchange apparatus with a simple installation operation and low installation cost in order to solve the said subject.

The present invention has been made in order to solve the above-mentioned problems, and the thick tube horizontal inclined convection type underground heat exchanger according to the present invention is a metal that is inclined, horizontally placed, and buried in the ground. This straight pipe is sealed at the two end faces intersecting the major axis at both ends, and is provided on the upper end face provided on the higher end face and on the lower end face. Upper and lower heating medium inlets and lower heating medium inlets and outlets are respectively provided at the lower part of the lower end surface, the cross-sectional area inside the straight pipe is not less than the area of a circle with a diameter of 29 cm, the distance between the upper end surface and the lower end surface, The ratio of the diameter of a circle having the same area as the cross-sectional area inside the tube is in the range of 3: 1 to 100: 1, the distance between the upper end surface and the lower end surface, and the height difference between the upper end surface and the lower end surface And a ratio of 3: 1 to 100: 1, and a concrete layer or a mortar layer was provided around the straight pipe And wherein the door.

In the straight pipe, it is preferable that the ratio of the distance between the upper end face and the lower end face and the diameter of a circle having the same area as the cross-sectional area inside the straight pipe is in the range of 3: 1 to 100: 1.

The concrete layer or mortar layer preferably has a thickness of 100 mm or more.
The straight pipe may have a distance of 1 to 10 m from the ground surface to the lowest part of the straight pipe.

The installation method of the horizontal pipe inclination type convection type underground heat exchanger which concerns on this invention is the process which excavates a hole, and installs the straight pipe of any one of Claim 1 thru | or 3 in the bottom part of a hole And a step of refilling the hole with concrete or mortar to a predetermined depth to provide a concrete layer or a mortar layer, and a step of refilling the hole with soil.

Moreover, the thick pipe horizontal inclination type | mold convection type underground heat exchanger of this invention is 1 or more of the large pipe horizontal inclination type | mold convection type underground heat exchanger of any one of Claims 1 thru | or 4, A heat medium and a liquid feeding means for circulating the heat medium; and a secondary heat exchanger that communicates with the underground heat exchanger and circulates the heat medium to absorb or / and discharge heat energy. Can be provided.

The liquid feeding means is capable of switching between the heat medium flowing from the upper heat medium inlet / outlet of the underground heat exchanger toward the lower heat medium inlet / outlet and the liquid feeding from the lower heat medium inlet / outlet toward the upper heat medium inlet / outlet. It is preferable that

The large horizontal tube inclined convection type underground heat exchanger according to the present invention is horizontally inclined so that the ratio between the distance between the upper end surface and the lower end surface and the height difference is 3: 1 to 100: 1. By providing / discharging the heat medium by providing a heat medium inlet / outlet at the upper part and the lower part of the lower end surface, convection is generated inside the horizontally inclined straight pipe, and the heat medium is agitated. The heat transfer efficiency increased because the tube wall and the heat medium contacted with relative speed.

Moreover, since the straight pipe portion is made of metal and the concrete or mortar layer is backfilled around the straight pipe portion of the present invention, the air between the soil and the heat medium is eliminated. Since the heat transfer resistance is small and it is a thick tube and has a wide heat transfer area, a high amount of underground heat exchange can be ensured.

Since the underground heat exchanger of the present invention is a horizontal type, the depth of the hole from the top of the straight pipe to the ground surface is only 1 to 10 m, so the installation cost when installing the vertical type underground heat exchanger The cost for drilling holes that occupy most of the area can be greatly reduced.
Moreover, since a high underground heat exchange amount can be ensured, the apparatus can be reduced in size, and installation costs and operation costs can be reduced.

According to an embodiment of the present application, the large horizontal tube inclined convection type underground heat exchanger of the present invention has a heat transfer amount of 14.4 per unit length compared to a conventional thin tube horizontal type underground heat exchanger. . In other words, the 11 m long horizontal tube inclined convection type underground heat exchanger of this embodiment corresponds to a conventional thin tube horizontal type underground heat exchanger having a cooling pipe of 158.4 m in length. It will be.
As a result, it is possible to provide a horizontal underground heat exchanger at low cost even on a small area of land, and to reduce the operating cost.

It is a longitudinal cross-sectional view along the long axis of the thick pipe horizontal inclination type | formula convection type | mold underground heat exchanger by one Example of this invention. FIG. 2 is a cross-sectional view taken along the line aa in FIG. 1. It is a schematic diagram of the convection which arises when a heat medium is cooled / heated by the underground heat exchanger of this invention. It is a schematic diagram of the convection which arises when a heat medium is heated / cooled by the underground heat exchanger of this invention. It is process drawing which shows the installation method of the thick pipe horizontal inclination type | formula convection type | mold underground heat exchanger by one Example of this invention. It is a block diagram of the thick pipe horizontal inclination type | formula convection type | mold underground heat exchange apparatus by one Example of this invention. It is a graph of the average temperature of the heat-medium inlet and outlet of the underground heat exchanger from which the internal diameter of the pipe | tube of this invention differs. It is a graph which compares the heat transfer amount of the underground heat exchanger with an internal diameter of 500 mm of this invention, and the thin tube horizontal type underground heat exchanger of a prior art. Heat medium inlet temperature and outlet of a horizontal tube inclined convection type underground heat exchanger having an inner diameter of 500 mm and a length of 11 m, and a conventional thin tube horizontal type underground heat exchanger having an inner diameter of 34 mm and a length of 11 m It is the figure which compared the average value with temperature.

Since the heat transfer amount of the underground heat exchanger is proportional to the heat transfer area, it is fundamental to expand the heat transfer area in order to increase the heat transfer amount. However, since the vertical underground heat exchanger uses, for example, a thin tube with an inner diameter of 34 mm, in order to obtain a sufficient heat transfer area, it has been necessary to excavate to a depth of 50 to 150 m underground.
In addition, the biggest problem with underground heat exchangers is the high installation cost. And most of the installation cost of the vertical underground heat exchanger was occupied by excavation costs.

The inventor has paid attention to a large horizontal pipe type heat exchanger, which has been neglected in the past because of low heat transfer efficiency, in order to reduce the installation price of the underground heat exchanger. And when the heat exchange pipe was tilted slightly from the horizontal and placed horizontally, the material of the underground heat exchanger was made of metal, and the surroundings of the heat exchanger were backfilled with concrete to increase the heat transfer efficiency from the soil, Surprisingly, a strong convection of the heat medium is generated inside the heat exchanger, the heat medium is agitated, and a relative flow velocity with the tube wall due to the convection is generated, so that the heat transfer is further improved, and the concrete layer Alternatively, the present inventors have found that extremely effective heat exchange between the soil and the heat medium is performed through the mortar layer and the metal pipe wall, and the heat transfer amount of the underground heat exchanger is dramatically increased.

[Ground heat exchanger]
FIG. 1 is a longitudinal sectional view taken along the major axis of a horizontally inclined convection type underground heat exchanger according to one embodiment of the present invention, and FIG. 2 is a transverse sectional view thereof.
As shown in FIGS. 1 and 2, the large horizontal tube inclined convection type underground heat exchanger 10 according to the present invention is horizontally inclined and embedded in the ground so that one end is higher than the other end. A straight metal pipe 11, an upper end face 12 that seals the higher end face of the straight pipe 11, a lower end face 13 that closes the lower end face, and an upper heat medium inlet / outlet provided above the upper end face 12 14, a lower heat medium inlet / outlet 15 provided at the lower portion of the lower end surface 13, and a concrete layer or a mortar layer 15 provided so as to surround the outside of the straight pipe 11.

Here, the reason for using metal for the straight pipe 11 is to reduce the resistance of energy transfer from the soil to the heat medium. The type of metal to be used is not particularly limited as long as it has high thermal conductivity and sufficient rigidity, but preferable examples include iron, steel, and stainless steel. Iron and steel can be used after being rust-proofed. In the case of a closed line type underground heat exchanger, the initial corrosion proceeds, but thereafter, the oxidizing component contained in the heat medium is consumed, so that the corrosion does not proceed thereafter.
The cross-sectional shape of the straight pipe 11 is not particularly limited as long as it can be used in the present invention, and may include, for example, a circular shape, a square shape, a rhombus shape, an oval shape, or the like. Specifically, it is preferable to use a circular pipe that is inexpensive, easily available, and excellent in mechanical strength.

Furthermore, conventionally, since the underground heat exchanger was backfilled with soil, sand, silica sand, etc., air could not be excluded from the backfilled part, and the energy from the soil to the heat medium was caused by the air. It was a great resistance to transmission. In the present invention, in order to prevent air from being mixed in, it is preferable that a concrete layer or a mortar layer is poured around the straight pipe 11 to be backfilled and solidified to exclude air.

Here, the straight pipe 11 of the large horizontal tube inclined convection type underground heat exchanger 10 has an elevation difference H between the upper end surface 12 and the lower end surface 13 and a distance L between the upper end surface 12 and the lower end surface 13. The ratio is preferably in the range of 1: 3 to 1: 100, and more preferably in the range of 1: 5 to 1:50. If the ratio is less than 1: 3, the convection of the heat medium may not be sufficiently developed and the stirring effect may be insufficient. If the ratio exceeds 1: 100, the inclination is too small and convection of the heat medium is generated. There are times when you can't.

The straight pipe 11 of the present invention has a diameter W of a circle having the same area as the cross-sectional area of the plane orthogonal to the long axis (that is, a circle having the same area as the area of the upper end surface 12 or the lower end surface 13), The ratio of the distance L between the upper end surface 12 and the lower end surface 13 is preferably in the range of 1: 3 to 1: 100, and more preferably in the range of 1: 5 to 1:50. If the ratio is less than 1: 3, convection does not develop sufficiently, and the stirring effect by convection may be insufficient. If it exceeds 1: 100, the straight pipe 11 becomes too thin and the heat medium 20 In some cases, the internal resistance becomes large and convection of a heat medium having sufficient strength cannot be generated.

Furthermore, in the present invention, the inner diameter W of a circle having the same area as the upper end surface 12 and the lower end surface 13 is preferably 200 mm or more, and more preferably 290 mm or more. When the inner diameter of the circle is less than 200 mm, the internal resistance of the heat medium 20 increases, and convection of the heat medium having sufficient strength may not be caused.

Furthermore, it is preferable that the concrete layer or the mortar layer surrounding the straight pipe 11 of the present invention has an average thickness of 100 mm or more. If the average thickness of the concrete layer or the mortar layer is less than 100 mm, the resistance of the energy transfer between the soil and the heat medium 12 is too large, and sufficient energy transfer cannot be performed. And the convection of the heat medium having sufficient strength may not be caused.
In addition, since soft soil containing a lot of air has low thermal conductivity, thicker concrete layers or mortar layers are preferred when installing underground heat exchangers. Is expensive. The optimum concrete or mortar layer thickness depends on the situation of the installation site.

Furthermore, in the straight 11 pipe of the present invention, the distance from the ground surface to the lowest part of the straight pipe can be 1 to 10 m, more preferably 1.5 to 7 m, and most preferably 2 to 5 m. Can be mentioned.
When the distance from the ground surface to the lowest part of the straight pipe is less than 1 m, the temperature stability of the underground heat exchanger and the energy supply capacity of the soil may not be sufficient. From the viewpoint of the performance of the underground heat exchanger, it is better that the depth of filling is deeper, but even if the depth exceeds 10 m, the improvement of the performance of the underground heat exchanger corresponding to the increase in excavation costs is not seen. Is not preferable.

[Convection]
The present invention generates a strong convection of the heat medium inside the heat exchanger to stir the heat medium, and generates a relative flow velocity with the tube wall due to the convection to improve heat transfer and The amount of heat transferred from the heat exchanger has been dramatically increased.
FIG. 3 is a schematic diagram of convection that occurs when the heat medium is cooled by the underground heat exchanger of the present invention.
As shown in FIG. 3, according to one embodiment of the present invention, the heated heat medium 20 a supplied from the upper heat medium inlet / outlet 14 of the underground heat exchanger 10 is near the upper end surface 12 of the straight pipe 11. It cools in contact with the tube wall 17a and becomes a downward flow 21a along the tube wall 17a, and a lower laminar flow 22 along the downward slope of the bottom of the straight tube 11 is generated. The lower laminar flow 22 is combined with the downward flow 21 on the entire surface of the tube wall 17 to increase the flow velocity and flow rate, and is further cooled to reach the lower end surface 13, and a part of the heat flow is cooled from the lower heat medium inlet / outlet 15. It is taken out as 20b. On the other hand, the remaining portion of the lower laminar flow 22 collides with the lower end surface 13 and becomes an inverted upward flow 23. The reverse upward flow 23 is sucked by the negative pressure for replenishing the heat medium to the downward flow 21 along the entire surface of the tube wall 17 to generate an upper laminar flow 24, thereby forming a stable convection and the heat medium 20. Is stirred.

The occurrence of such convection is that during the operation of the underground heat exchanger 10, the surface temperature of the straight pipe is almost the same in all of the vicinity of the upper heat medium inlet / outlet 14, the central part, and the lower heat medium inlet / outlet 15. However, it was confirmed that when the operation was stopped, the temperature in the vicinity of the upper heat medium inlet / outlet 14 increased and the temperature in the lower heat medium inlet / outlet 15 decreased.

FIG. 4 is an estimation diagram of convection that occurs when the heat medium is heated by the underground heat exchanger of the present invention.
As shown in FIG. 4, according to another embodiment of the present invention, the cooled heat medium 20 b supplied from the lower heat medium inlet / outlet 15 of the underground heat exchanger 10 is near the lower end surface 13 of the straight pipe 11. The tube wall 17b is heated in contact with the tube wall 17b and becomes an upward flow 25b along the tube wall 17b, resulting in an upper laminar flow 24 along the upward slope of the top of the straight tube 11. The upper laminar flow 24 is combined with the upward flow 25 of the entire tube wall 17 to increase the flow velocity and flow rate, and is further heated to reach the upper end surface 12, and a part of the heat flow is heated from the upper heat medium inlet / outlet 14. It is taken out as 20a. On the other hand, the remaining portion of the upper laminar flow 24 collides with the upper end surface 12 to become a reverse descending flow 26, and the reverse descending flow 26 is a negative pressure for supplying the heat medium 20 to the upward flow 25 along the entire tube wall 17. And the lower laminar flow 22 is generated, thereby forming a stable convection and stirring the heat medium 20.

The main starting force that generates convection is the lower laminar flow 22 toward the lower end surface 13 along the inclination of the straight pipe 11 when the heat medium 20 is cooled, and the straight pipe when the heat medium 20 is used. It is estimated that the upper laminar flow is directed toward the upper end surface 12 along the inclination of 11.
In the case of cooling / heating the heat medium shown in FIG. 3, the heated heat medium is supplied from the upper heat medium inlet / outlet, the cooled heat medium is taken out from the lower heat medium inlet / outlet, and the heat medium shown in FIG. 4 is heated. In the case of cooling / cooling, an example is shown in which the cooled heat medium is supplied from the lower heat medium inlet / outlet and the heated heat medium is taken out from the upper heat medium inlet / outlet. However, the direction in which the heat medium is supplied to and extracted from the underground heat exchanger 10 is not limited to the above example.

[Installation method]
FIG. 5 is a process diagram showing a method for installing the horizontal inclined convection type underground heat exchanger of the present invention.
As shown in FIG. 5, the method for installing the large horizontal tube inclined convection type underground heat exchanger of the present invention includes a step of excavating a hole as a first step. Here, the foundation can be provided with concrete or mortar before entering the second step.

Next, as a second step, the straight pipe, which is the main part of the underground heat exchanger, is installed with an inclination in which the ratio between the distance between the upper end surface and the lower end surface and the height difference is 3: 1 to 100: 1. To do. In the first step, a hole with a predetermined slope can be dug in advance.
In the straight pipe, the ratio of the distance between the upper end surface and the lower end surface and the inner diameter of a circle having the same area as the cross-sectional area of the surface orthogonal to the long axis may be in the range of 3: 1 to 100: 1. it can. The straight pipe may have an inner diameter of the circle of 200 mm or more.

Next, as a third step, the hole in which the straight pipe is installed is backfilled with a concrete layer or mortar to form a concrete layer or mortar layer, taking care not to allow air to enter. The concrete layer or the mortar layer preferably has an average thickness of 100 mm or more.
Next, as a fourth step, the hole is backfilled with soil to complete the underground heat exchanger of the present invention.
The ground heat exchanger installation method of the present invention is to backfill the hole with a concrete layer or mortar to a predetermined depth in order to exclude air between the main body portion of the ground heat exchanger and the soil portion. It is characterized by.

[Ground heat exchanger]
FIG. 6 is a configuration diagram of a large horizontal tube inclined convection type underground heat exchanger according to an embodiment of the present invention.
As shown in FIG. 6, the large horizontal tube inclined convection type underground heat exchanger 1 of the present invention includes one or more large horizontal tube inclined convection type underground heat exchangers 10 and a secondary side heat exchange. The container 30 and the liquid feeding means 40 are provided to supply energy to the working machine 50.
The laterally inclined convection type underground heat exchange device 1 of the present invention includes an upper heat medium inlet / outlet 14 and a lower heat medium inlet / outlet 15 of the underground heat exchanger 10 and a heat medium of the secondary heat exchanger 30. It is preferable that the inlet /

outlet ports

32, 33 are in communication with a liquid supply pipe 33, and a closed-line geothermal heat pump device in which the liquid supply means 40 is provided on the heat medium pipe 33.

Further, the liquid feeding means 40 of the present invention feeds the heat medium from the upper heat medium inlet / outlet 14 to the lower heat medium inlet / outlet 15 of the underground heat exchanger 10 and from the lower heat medium inlet / outlet 15 to the upper heat medium inlet / outlet 14. It is preferable that the liquid feeding in the direction can be switched.
Further, the liquid feeding means 40 of the present invention can feed liquid from only the lower heat medium inlet / outlet 15 or only from the direction of the upper heat medium inlet / outlet 14.

Furthermore, the large horizontal tube inclined convection type underground heat exchanger 1 of the present invention can include two or more large horizontal tube inclined convection type underground heat exchangers 10. The large horizontal tube inclined convection type underground heat exchanger 10 can be installed in parallel with each of the upper heat medium inlet / outlet 14 and the lower heat medium inlet / outlet 15 of each heat exchanger communicating with each other. .
Further, the two or more thick pipe horizontal inclined convection type underground heat exchangers 10 are respectively connected to the upper heat medium inlet / outlet port 14 of each of the thick pipe horizontal inclined convection type underground heat exchangers 10 and the adjacent large pipes. The lower heating medium inlet / outlet port 15 of the horizontally inclined convection type underground heat exchanger 10 can be communicated with one line in series.

Example 1
An upper end surface 12 and a lower end surface 13 are attached to and sealed at both ends of a steel pipe having an inner diameter of 500 mm and a length of 11 m, and an upper heat medium inlet / outlet 14 and a lower heat medium inlet / outlet 15 are respectively connected to the uppermost portion of the upper end surface 12 and the lowermost portion of the lower end surface 13. The straight pipe 11 having an inner diameter of 500 mm was manufactured.
Next, a hole having a width of 1300 mm, a length of 12 m, and a depth of 1700 mm was excavated on the ground, and 100 mm thick concrete was poured into the bottom of the hole and solidified. Next, the straight pipe 11 having an inner diameter of 500 mm was installed in the hole so that the upper end face 12 was higher than the lower end face 13 by 250 mm.
Next, the ready-mixed concrete was poured from the ground surface to 650 mm so that bubbles would not enter and solidified, and then the remainder of the hole was backfilled with soil to produce the underground heat exchanger 10 of Example 1.

(Example 2)
An upper end surface 12 and a lower end surface 13 are attached and sealed at both ends of a steel pipe having an inner diameter of 290 mm and a length of 11 m, and an upper heat medium inlet / outlet 14 and a lower heat medium inlet / outlet are respectively provided at the uppermost portion of the upper end surface 12 and the lowermost portion of the lower end surface 13. A straight tube 11 having an inner diameter of 290 mm and projecting 15 was manufactured.
Next, a hole having a width of 1100 mm, a length of 12 m, and a depth of 1700 mm was excavated on the ground, and 100 mm thick ready-mixed concrete was poured into the bottom of the hole and solidified. Next, the straight pipe 11 having an inner diameter of 290 mm was installed in the hole so that the upper end surface 12 was higher than the lower end surface 13 by 250 mm.
Next, the ready-mixed concrete was poured from the ground surface to 670 mm with care so that bubbles do not enter and solidified, and then the remaining holes were backfilled with soil to produce the underground heat exchanger 10 of Example 2.

(Example 3)
An upper end surface 12 and a lower end surface 13 are attached and sealed at both ends of a steel pipe having an inner diameter of 200 mm and a length of 11 m, and an upper heat medium inlet / outlet 14 and a lower heat medium are respectively provided at the uppermost portion of the upper end surface 12 and the lowermost portion of the lower end surface 13. A straight pipe 11 having an inner diameter of 200 mm and having an inlet / outlet 15 protruding therefrom was manufactured.
Next, a hole having a width of 1000 mm, a length of 12 m, and a depth of 1700 mm was excavated on the ground, and 100 mm thick raw concrete was poured into the bottom of the hole to be solidified. The straight pipe 11 having an inner diameter of 200 mm was installed in the hole so that the upper end surface 12 was higher than the lower end surface 13 by 250 mm.
Next, the ready-mixed concrete was poured from the ground surface to 680 mm with care so that bubbles do not enter and solidified, and then the remaining holes were backfilled with soil to produce the underground heat exchanger 10 of Example 3.

(Comparative Example 1)
An upper end surface 12 and a lower end surface 13 are attached and sealed to both ends of a steel pipe having an inner diameter of 68 mm and a length of 11 m, and an upper heat medium inlet / outlet 14 and a lower heat medium inlet / outlet are respectively provided at the uppermost portion of the upper end surface 12 and the lowermost portion of the lower end surface 13. The straight pipe 11 having an inner diameter of 68 mm was manufactured by projecting 15.
Next, a hole having a width of 900 mm, a length of 12 m, and a depth of 1700 mm was excavated on the ground, and 100 mm thick ready-mixed concrete was poured into the bottom of the hole and solidified. In the hole, the straight pipe 11 having an inner diameter of 64 mm was installed so as to be inclined so that the upper end surface 12 was higher than the lower end surface 13 by 250 mm.
Next, after pouring the ready-mixed concrete up to 1.2 m from the ground surface with care so as not to enter air bubbles and solidifying it, the remaining holes were backfilled with soil to produce the underground heat exchanger 10 of Comparative Example 2. did.

(Comparative Example 2)
As in Comparative Example 1, the underground heat exchanger 10 of Comparative Example 3 was manufactured using a steel pipe having an inner diameter of 34 mm and a length of 11 m.
(Comparative Example 3)
A hole having a width of 4.0 m, a length of 11 m, and a depth of 1.7 m was excavated on the ground, and 100 mm thick ready-mixed concrete was poured into the bottom and solidified. Further, a steel pipe having a length of 30 m, an inner diameter of 34 mm, and a pipe wall thickness of 1 mm is bent into “self” shape at four locations, and the interval between the tubes and the interval between the tube and the earth wall of the hole are 1. Install it at 0 m, install heat medium entrances at both ends, and pouring the ready-mixed concrete from above to 1.2 m from the ground with care not to allow air bubbles to enter, solidify the remaining holes The ground heat exchanger of Comparative Example 1 Example 1 was manufactured by backfilling with soil.

[Test example]
(Test method)
The thick pipe horizontal inclination type convection type underground heat exchange apparatus shown in FIG. 6 is used, except that a water tank is used as the secondary heat exchanger 30 and a 3 KW electric heater is used as the working machine 50, and the liquid feeding means 40 is used. Then, 30 L of water was fed every minute, and the cooling test of the heat medium as shown in FIG. 3 was performed, and the circulating water temperature passing through the upper heat medium inlet / outlet 14 and the lower heat medium inlet / outlet 15 was measured.

(Test Example 1) Regarding the pipe diameter Using the underground heat exchangers of Examples 1 to 3 and Comparative Examples 1 and 2, a cooling test of the secondary heat exchanger 30 was performed, and the upper heat medium inlet / outlet 14 and the lower heat medium The temperature of circulating water passing through the entrance / exit 15 was measured. Table 1 shows the average values of the outlet and the entrance, and FIG. 7 shows the graph.

As shown in FIG. 7, the underground heat exchanger using the underground heat exchanger having an inner diameter of 500 mm according to the first embodiment and the underground heat exchanger using the underground heat exchanger having an inner diameter of 290 mm according to the second embodiment are very A large amount of heat exchange was shown, and the average circulating water temperature after 12 hours was 6.8 ° C. in Example 1 and 12.2 ° C. in Example 1. Both showed sufficient cooling power.
In Example 3, the average circulating water temperature after 3 hours was 39.3 ° C., but it was judged that it could be used for a load smaller than the 3 KW electric heater of this test example.
Comparative Example 1 using an underground heat exchanger having an inner diameter of 68 mm and Comparative Example 2 using an underground heat exchanger using an underground heat exchanger having an inner diameter of 34 mm lacked the amount of heat exchange.

(Test example 2) Comparison between a thick tube horizontal inclined convection type underground heat exchanger (Example 1) having an inner diameter of 500 mm and a conventional thin tube type horizontal underground heat exchanger (Comparative Example 3) having an inner diameter of 34 mm The underground heat exchange apparatus using the underground heat exchanger having the inner diameter of 500 mm and the length of 11 m of Example 1 and the comparative example 3 of the thick tube horizontal inclined convection type underground heat exchange apparatus shown in FIG. Comparison was made with a prior art thin tube horizontal underground heat exchanger with an inner diameter of 34 mm and a length of 30 m.
The measured values of the heat medium inlet temperature and the outlet temperature of Example 1 and Comparative Example 3 and their rising temperatures are shown in Table 2, and the graph is shown in FIG.

As shown in Table 2 and FIG. 8, the underground heat exchanger with an inner diameter of 500 mm of Example 1 showed a heat exchange capability far superior to the conventional thin tube horizontal underground heat exchanger. However, the conventional horizontal tube horizontal heat exchanger of Comparative Example 3 has insufficient cooling capacity with respect to the 3 KW electric heater.

(Test Example 3)
FIG. 9 shows a thick tube horizontal inclined convection type underground heat exchanger having an inner diameter of 500 mm and a length of 11 m, and a conventional narrow tube horizontal underground heat exchanger of Comparative Example 2 having an inner diameter of 34 mm and a length of 11 m, It is the graph which compared the average value with the heat-medium inlet temperature of this, and outlet temperature.
As shown in FIG. 9, the temperature rise value of Example 1 is 5.60 ° C. and the temperature rise value of Comparative Example 1 is 80.68 ° C. Since the tube lengths of the underground heat exchanger 1 and Comparative Example 1 are the same, the heat transfer amount per unit tube length of Example 1 is 14.4 times the heat transfer amount of Comparative Example 1. If a simplified proportional calculation is performed, the underground heat exchanger having a length of 11 m in Example 1 corresponds to a underground heat exchanger having an inner diameter of 34 mm and a length of 158.4 meters. .
If the large horizontal tube inclined convection type underground heat exchanger of the present invention is used, it is possible to install a horizontal underground heat exchanger even in a narrow land.

As mentioned above, although preferred embodiment regarding this invention was described, this invention is not limited to the said embodiment, All the changes in the range which does not deviate from the technical scope to which this invention belongs are included.

DESCRIPTION OF SYMBOLS 1 Thick pipe horizontal inclination type convection type underground heat exchanger 10 Thick pipe horizontal inclination type convection type underground heat exchange apparatus 11 Straight pipe 12 Upper end surface 13 Lower end surface 14 Upper heat-medium inlet / outlet 15 Upper heat-medium inlet / outlet 16 Concrete layer Or mortar layer 17 Pipe wall 18 Soil 20 Heat medium 21 Downflow 22 Lower laminar flow 23 Reversed upflow 24 Upper laminar flow 25 Upflow 26 Reversed downflow 30

Secondary heat exchanger

31, 32 Secondary heat exchanger inlet / outlet 33 Feeding Liquid tube 40 Liquid feeding means 50 Working machine

Claims

A metal straight pipe that is tilted, placed horizontally, and buried in the ground,
The straight pipe is sealed with two end faces whose both ends intersect the long axis,
An upper heat medium inlet / outlet and a lower heat medium inlet / outlet are provided on each of an upper part of an upper end face provided on the higher end face and a lower part of a lower end face provided on the lower end face,
The cross-sectional area inside the straight pipe is equal to or greater than the area of a circle having a diameter of 29 cm, the cross-sectional area inside the straight pipe;
The ratio of the distance between the upper end surface and the lower end surface and the diameter of a circle having the same area as the cross-sectional area inside the straight pipe is in the range of 3: 1 to 100: 1,
The ratio between the distance between the upper end surface and the lower end surface and the height difference between the upper end surface and the lower end surface is in the range of 3: 1 to 100: 1;
A thick pipe horizontal inclined convection type underground heat exchanger, wherein a concrete layer or a mortar layer is provided around the straight pipe.
The thick pipe horizontal inclined convection type underground heat exchanger according to claim 1, wherein the concrete layer or the mortar layer has a thickness of 100 mm or more.
3. The large horizontal pipe inclined convection type underground heat exchanger according to claim 1 or 2, wherein the straight pipe has a distance of 1 to 10 m from the ground surface to the lowest part of the straight pipe.
Drilling holes,
Installing the straight pipe according to any one of claims 1 to 3 at the bottom of the hole;
Refilling the hole with concrete or mortar to a predetermined depth to provide a concrete layer or mortar layer;
The process of filling the hole back with soil,
The installation method of the horizontal pipe inclined type convection type underground heat exchanger characterized by having.
One or more of the large horizontal tube inclined convection type underground heat exchanger according to any one of claims 1 to 3,
A heat medium and liquid feeding means for circulating the heat medium;
A secondary side heat exchanger that communicates with the underground heat exchanger and that circulates the heat medium and absorbs and / or exhausts heat energy;
A thick pipe horizontal inclined convection type underground heat exchange device comprising:
The liquid feeding means feeds the heat medium from the upper heat medium inlet / outlet of the underground heat exchanger toward the lower heat medium inlet / outlet and the liquid feeding from the lower heat medium inlet / outlet toward the upper heat medium inlet / outlet. The thick tube horizontal inclined convection type underground heat exchange device according to claim 5, which is switchable.