JP2014185822A - Geothermal heat utilization heat exchanger and heat pump system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical buried geothermal heat exchanger which can shorten boring depth to the extent of a fraction of the boring depth of the conventional long-size vertical buried geothermal heat exchanger and can reduce the boring cost drastically, while providing heat exchange efficiency equal to the heat exchange efficiency of the conventional long-size vertical buried geothermal heat exchanger or more, and to provide a heat pump using the vertical buried geothermal heat exchanger.SOLUTION: A geothermal heat exchanger is provided with a geothermal heat exchange structure formed by using at least three fluid paths made of resin which have outward path for causing circulation fluid to flow from ground surface side toward under ground and a return path for causing the fluid passing through the outward path to flow from the under ground toward the ground surface side, as a fluid path for causing the circulation fluid to be exchanged with geothermal heat in a heat exchange region formed from the ground surface to vertically under side.

Description

  The present invention relates to a vertical buried underground heat exchanger and a heat pump system using the same. More specifically, the present invention relates to an underground heat exchanger having an underground heat exchange structure formed from a plurality of resin fluid paths and a heat pump system using the underground heat exchanger.

  The underground temperature is almost constant at 10 to 15 ° C. throughout the year, and is lower in summer and higher in winter than the outside air temperature. Therefore, in order to use the temperature difference from the outside air, a heat exchanger is buried in the ground and the ground heat is collected and used as a heat source. Proposals have been made.

  This underground heat utilization technology uses ground heat, which is almost constant in the ground, to perform heat exchange. In the winter, it is used as a high-temperature energy source for heating or for melting snow. Heat can be collected and used. In summer, geothermal heat can be used as a heat source for cooling as low-temperature energy. Geothermal heat is an efficient heat source because its temperature is more stable than the atmosphere, and it is a heat source that generates less carbon dioxide. Has been.

  As such a ground heat utilization system, a system in which a heat exchange tube is installed vertically in the ground is known. The underground heat exchange tube system installed vertically has the characteristics that the ground surface area occupied for installation is small and the heat loss of the ground surface is small. As an underground heat exchange tube system installed vertically, one or two sets of steel U-shaped pipes with a diameter of several tens of millimeters or plastic U-shaped pipes are inserted into vertical excavation holes, and the surrounding soil material (grouting material) ). For example, Patent Document 1 proposes to use a U-shaped tube in which the lower ends of parallel straight tube portions communicate with each other as a U-shaped tube.

  However, in order to efficiently use the underground heat in the vertically installed underground heat exchange tube system, it is necessary to embed the heat exchange tube deep into the ground, and the drilling depth for embedment is several tens of meters. A depth of ~ 100m was required. Therefore, the long vertical buried underground heat exchanger has a problem that the excavation cost is high and the installation cost is high.

  Therefore, a proposal has been made to reduce the drilling cost by making the drilling depth shallower. For example, Patent Document 2 proposes that one of the U-shaped tubes embedded vertically is a spiral fluid path. However, in order to form a spiral fluid path, complicated and precise forming of the pipe is required, which increases the manufacturing cost. In addition, if the fluid path is spiral, the vertical distance between the spiral fluid paths is narrow. There is a problem that the efficiency of heat exchange with the ground does not increase relative to the length of the fluid path.

Japanese Patent Laid-Open No. 11-182943 JP 2007-315742 A

  The present invention solves the above-mentioned conventional problems, and shortens the drilling depth to about a fraction of that while realizing a heat exchange efficiency equal to or higher than that of a known long vertical buried underground heat exchanger. An object of the present invention is to provide a vertical buried underground heat exchange structure that can reduce excavation costs.

  The present invention is embedded in the same heat exchange region formed downward from the ground. As a fluid path for exchanging the circulating fluid to the ground, a resin fluid path having a forward path for flowing the circulating fluid from the ground side toward the ground and a return path for flowing the fluid passing through the forward path from the ground toward the ground side A ground heat exchanger having a ground heat exchange structure formed by using at least three is provided.

  The above-described underground heat exchanger, in which the underground heat exchange structure includes an interval holding member that holds the interval of the fluid path at a predetermined interval, is a preferred aspect of the present invention.

  The above-mentioned underground heat exchanger in which the fluid path serving as the forward path or the return path maintains an interval of at least 7 cm between the adjacent fluid path serving as the forward path or the return path is a preferred embodiment of the present invention.

  The above-mentioned underground heat exchanger in which the contact points of the forward path and the return path of the resin fluid path are in regions where the depths are substantially the same and the resin fluid paths intersect in plan view is a preferred aspect of the present invention. .

  The present invention also provides a geothermal heat pump system having the above-described underground heat exchanger as a heat exchange device.

According to the present invention, the depth of drilling can be reduced to a fraction of that while realizing a heat exchange efficiency equal to or greater than that of a long vertical buried underground heat exchanger, and the excavation cost can be greatly reduced. A vertical buried underground heat exchanger is provided.
When using a vertical buried underground heat exchanger as a heat exchanger for a load device such as a heat pump, a significant percentage of the installation cost is excavation cost for installing the underground heat exchanger. Therefore, the installation cost can be greatly reduced.
The present invention provides a heat pump using a vertical buried underground heat exchanger that can significantly reduce excavation costs while realizing a heat exchange efficiency equal to or higher than that of a long vertical buried underground heat exchanger. .

It is the schematic which shows the structure of the vertical burying type underground heat exchanger of this invention. It is a schematic sectional drawing in AA of FIG. 1 of the underground heat exchange structure of this invention. It is a photograph which shows the outline of the cross | intersection part of the resin-made fluid paths of this invention. It is a photograph which shows the whole underground heat exchange structure of this invention. It is the schematic which shows the heat pump using the vertical burying type underground heat exchanger of this invention.

  The present invention is embedded in a heat exchange region formed downward from the ground. As a fluid path for exchanging the circulating fluid to the ground, a resin fluid path having a forward path for flowing the circulating fluid from the ground side toward the ground and a return path for flowing the fluid passing through the forward path from the ground toward the ground side The underground heat exchanger provided with the underground heat exchange structure formed by using at least three is provided.

The heat exchanging region of the present invention is a region in which a hole excavated downward from the ground surface is backfilled with a filler such as a soil material. The excavation hole is an underground hole that has been backfilled with filler after an underground heat exchange structure is installed in a hole formed by a conventionally known method such as drilling by boring or drilling using a screw auger. This is a region where heat exchange is performed.
As the filler, it is preferable to use a material having good material thermal conductivity. For example, the filler is composed of a material containing at least one selected from excavated soil, sandy soil, gravelly soil, organic soil, gravel and crushed stone. Soil materials are preferably used. In the heat exchange area, rainwater and groundwater flowing in the ground permeate between the filler particles filled in the excavation part, and the groundwater promotes heat exchange between the underground heat exchanger and the ground.

  The resin-made fluid path is a fluid path that allows a circulating fluid such as antifreeze (brine) and water to flow and exchange heat with underground heat, and exchanges the circulating fluid with ground heat. The resin-made fluid path of the present invention is a fluid path for exchanging the circulating fluid with respect to the ground, an outward path for flowing the circulating fluid from the ground side toward the ground, and a fluid passing through the forward path from the ground toward the ground side. It has a return path to flow, and is preferably a tubular body.

Examples of the resin constituting the resin fluid path include polyolefins such as polyethylene, polypropylene, and polybutene, polyvinyl chloride, and polyamide. Of these, polyolefin pipes, particularly ethylene pipes are particularly preferred.
The contact point between the resin fluid path forward path and the return path may be via an elbow, but a U-shaped tube having lower ends communicating with each other is preferable.

The underground heat exchange structure of the present invention is desirably formed using at least 3, preferably 3 to 6, more preferably 3 or 4, and particularly 4 resin fluid paths.
In the present invention, the forward path and the return path of the resin fluid path constituting the underground heat exchanging structure are installed with an interval between the forward path and the return path of the adjacent resin fluid paths at a predetermined value or more. It is preferable.

  If the distance between the fluid paths is too short, the amount of filler in the heat exchange region to be heat exchange will be relatively small, and the heat exchange efficiency may be reduced. In a conventionally known vertical buried type underground heat exchanger, one fluid path is usually laid, but it is also proposed to lay two fluid paths in the laying region (for example, Patent Document 2). FIG. 4). However, in the laying method as in the patent document, since the distance between the fluid paths is shortened, it is difficult to improve the total heat exchange efficiency when the total extension distance of the fluid paths is increased.

  The present invention provides a ground heat exchange structure that obtains a predetermined total heat exchange efficiency by extending the total extension distance of the fluid path by using at least three resin fluid paths. With such an underground heat exchange structure, even if the drilling depth is shortened to about a fraction, heat exchange efficiency equal to or higher than that of conventional long vertical buried underground heat exchangers can be realized. This makes it possible to provide a vertical buried underground heat exchanger that significantly reduces drilling costs.

  In the present invention, the distance between the forward path and the return path of the resin fluid paths adjacent to each other is preferably 7 cm or more, preferably the distance between the pipe centers. Are preferably installed at intervals of about 9 cm, more preferably about 11 cm or more.

  In order to set the interval between the resin fluid paths to a predetermined value or more, an interval holding member can be used. There is no restriction | limiting in particular in the shape of a space | interval holding member, What is necessary is just a shape which can achieve a predetermined objective. For example, one having a holder extending from the circular base material surrounding three or more resin-made fluid paths to each forward path and return path of the resin-made fluid path may be adopted.

  When forming the underground heat exchange structure with three or more resin fluid paths, each resin fluid path may be configured in an arbitrary positional relationship, but there are contact points between the forward path and the return path of the resin fluid path. It is convenient in terms of handling and embedding work of the underground heat exchange structure that the resin fluid paths intersect with each other in a plan view because the depths are in substantially the same region. Such an underground heat exchange structure in which a spacing member is installed at a predetermined position in a resin fluid passage in a positional relationship is excellent in workability and can obtain stable underground heat exchange efficiency. Become.

  The underground heat exchanger using the underground heat exchange structure composed of three or more resin fluid passages according to the present invention is wider than the conventionally known vertical buried type underground heat exchanger in the surface occupation area. Become. For example, in a conventionally known underground underground heat exchanger, if a hole having a diameter of about 15 cm is drilled, it is considered that a hole having a diameter of about 25 to 30 cm is required to implement the present invention. Since the amount of filler for heat exchange in the underground heat exchange area is increased and the total extension distance of the resin fluid path can be increased, the conventional long shape can be achieved even if the drilling depth is reduced to a fraction. A heat transfer efficiency equivalent to or better than that of a vertical buried underground heat exchanger can be realized, and a vertical buried underground heat exchanger with a drastic reduction in excavation costs will be realized.

  The circulating fluid in the resin fluid path of the present invention enters from the inlet of the fluid path and exits from the outlet through the return path, but in the summer, the underground temperature is constant and lower than the outside air temperature on the ground. The circulating fluid is cooled in the underground heat exchange region to become a circulating fluid of approximately 15 ° C., and becomes a circulating fluid warmed to the underground temperature in the underground heat exchange region in winter.

  In the underground heat exchange structure of the present invention, there are fluid path end portions serving as inlets and outlets of the circulating fluid in the fluid paths according to the number of resin fluid paths used. Each inlet fluid path end and outlet fluid path end may form a plurality of independent fluid circulation systems, or may communicate with each other to form a single fluid circulation system. When communicating to form one fluid circulation system, a plurality of inlet fluid passage end portions and outlet fluid passage end portions are respectively formed into one tube using members such as a T-shaped tube, a coupling tube, and a header. Can be connected.

  Hereinafter, the present invention will be described with reference to the drawings. The specific example described below is a case where the underground heat exchange structure is formed by four resin fluid paths.

  FIG. 1 shows an example of a vertical buried underground heat exchanger 1 according to the present invention. In FIG. 1, a ground heat exchanging structure 2 consisting of four U-shaped pipes made of straight resin pipes 3 forming a forward path and a return path of circulating fluid is installed and filled in a borehole drilled downward from the ground surface 10. A state of being backfilled with the material 11 is shown. The U-shaped pipe composed of four straight resin pipes 3 is installed so that the resin pipes intersect each other in plan view near the lower end of the drilling hole. In the underground heat exchanging structure 2 in FIG. 1, a spacing member 5 is provided at a predetermined position.

  The drilling hole in FIG. 1 is excavated to a depth of 30 m, and the underground heat exchange structure 2 is formed by four U-shaped pipes made of polyethylene pipe having an outer diameter of 17 mm as a resin pipe and an inner diameter of 12.2 mm. Therefore, the total length of the circulating fluid path of the underground heat exchange structure 2 is 240 m.

  In the underground heat exchange structure 2 of FIG. 1, each of the outward paths of the U-shaped pipe composed of four straight resin pipes 3 is communicated by the header 4. In addition, the U-tube return paths communicate with each other through a header 4. The underground heat exchange structure 2 in FIG. 1 is communicated by a header to form one fluid circulation system.

  FIG. 2 shows a cross-sectional view of the underground heat exchange structure 2 shown in FIG. In FIG. 2, two U-shaped tubes forming the underground heat exchanging structure 2 are provided in total by a tube holding portion 8 connected to the arm portion 7 installed on the circular frame 6 of the interval holding member 5. It is fixed at a location by the tube spacing member 5. The resin pipes constituting each U-shaped pipe serve as a forward path and a return path of the circulating fluid. For example, if the resin pipe 3-1 is the forward path, the resin pipe 3-2 communicating with it is the return path.

The shape of the pipe interval holding member is not limited to that shown in FIG. 2, but the pipe interval holding member allows the fluid path serving as each forward path or return path of the resin pipe to be close to the contact point between the forward path and the return path, Since a distance of at least 7 cm is maintained between adjacent forward or return fluid paths, good heat exchange efficiency with the underground heat is realized.
As shown in FIG. 2, if three resin fluid paths are arranged on the circumference of approximately equal intervals between the forward path and the return path of each resin fluid path, and the diameter of the circumference is 30 cm, The distance between the fluid path serving as the forward path or the return path and the fluid path serving as the forward path or the return path adjacent to each other is approximately 15 cm.

  FIG. 3 is a photograph showing a state near the bottom of the underground heat exchange structure 2. Each U-shaped pipe made of four straight resin pipes 3 from FIG. 3 intersects in plan view, and two U-shaped pipes are fixed by the pipe interval holding member 5 at a total of 8 positions. I understand well. FIG. 4 is a photograph showing the overall state of the underground heat exchange structure. A header is used at the end of the underground heat exchange structure in FIG.

FIG. 5 is a schematic view of a heat pump system using geothermal heat having the vertical buried underground heat exchanger of the present invention as a geothermal heat exchange device. FIG. 9 shows the operation status of the geothermal heat pump system in winter. Circulating fluids such as antifreeze (brine) and water circulate in the fluid path of the underground heat exchange structure.
In the winter season, the circulating fluid heated to the ground temperature in the ground heat heat exchange region 12 is guided to the heat exchanger A (evaporating part) 93 in the peat pump 9, and heat is taken away by heat exchange with the heat medium. As a result, the temperature drops and the heat medium evaporates due to endotherm. The circulating fluid that has been led to the heat pump 9 and whose temperature has dropped returns to the underground heat exchange region 2 again. At this time, since the underground temperature is higher in the constant temperature state than the outside air temperature on the ground, when the circulating fluid is fed into the ground from the ground side, it is collected and heated in the underground heat exchange area and circulated. It will circulate through the fluid circulation system 91 to the heat exchanger A93 in the peat pump.

The heat medium evaporated in the heat exchanger A of the peat pump enters the heat exchanger B (condensing unit) 94 through the compressor 95. A secondary heat storage medium that circulates in the heat dissipation system is guided to the heat exchanger B, and heat is released from the heat medium by heat exchange, so that the temperature of the secondary heat storage medium rises. The heat medium whose temperature has decreased due to heat dissipation circulates again to the heat exchanger A93 to exchange heat with the circulating fluid.
The secondary heat storage medium whose temperature has increased reaches the heat dissipation system 97 through the secondary heat storage medium circulation system 92, and a desired heating function is obtained. Examples of the heat dissipation system include floor heating, a fan coil unit, a snow melting panel, a snow melting heat radiation pipe, and the like. The heat dissipation system is also a circulation loop, and the secondary heat storage medium that has released heat in the heat dissipation system is again led to the heat exchanger B (refrigerant condensing unit) 94 by the secondary heat storage medium circulation system 92 and heated, It is supplied again to the heat dissipation system.
In each circulation system, a pump is installed for fluid circulation, but the pump is not shown in FIG.

  In the summer, the temperature of the circulating fluid rises as the circulating fluid of approximately 15 ° C. takes heat away from the heat exchanger in the heat exchanger in the peat pump. The circulating fluid whose temperature has been increased by being guided to the heat pump returns to the underground heat heat exchange region again. At this time, since the underground temperature is constant and lower than the outside air temperature on the ground, when the circulating fluid is fed from the ground side into the ground, it is cooled in the underground heat exchange region and circulated again to the heat exchanger. It will be.

  The heat medium cooled by the circulating fluid in the peat pump enters the heat exchanger through the expansion valve and takes heat from the secondary heat storage medium. The heat medium whose temperature has risen is circulated again to the heat exchanger, and heat is taken from the circulating fluid to exchange heat with the underground heat. The cooled heat medium reaches the heat dissipation system through the pipe, and a desired cooling function is obtained. The heat dissipation system is also a circulation loop, and the secondary heat storage medium whose temperature has increased in the heat dissipation system is again guided to the heat exchanger B (refrigerant condensing unit), cooled, and supplied to the heat dissipation system again.

According to the present invention, the depth of drilling can be reduced to a fraction of that while realizing a heat exchange efficiency equal to or greater than that of a long vertical buried underground heat exchanger, and the excavation cost can be greatly reduced. A vertical buried underground heat exchanger is provided.
When using a vertical buried underground heat exchanger as a heat exchanger for a load device such as a heat pump, a significant percentage of the installation cost is excavation cost for installing the underground heat exchanger. Therefore, the installation cost can be greatly reduced.
The present invention provides a heat pump using a vertical buried underground heat exchanger that can significantly reduce excavation costs while realizing a heat exchange efficiency equal to or higher than that of a long vertical buried underground heat exchanger. .

1. 1. Vertical buried underground heat exchanger 2. Underground heat exchange structure Resin pipe 3-1. Outward path 3-2. Return way4. Header 5. 5. Spacing member Frame 7. Arm part 8. 8. Tube holding part Heat pump 91. Circulating fluid circulation system 92.2 Secondary heat storage medium circulation system 93. Heat exchanger A
94. Heat exchanger B
95. Compressor 96. Expansion valve 97. Heat dissipation system 10. Surface 11. Filler 12. Underground heat exchange a. Circulating fluid inlet b. Circulating fluid outlet

Claims (7)

  In the heat exchange area formed vertically below the ground, as the fluid path for exchanging the circulating fluid to the ground, the forward path for flowing the circulating fluid from the surface side to the ground and the fluid that has passed the forward path from the ground to the ground A ground heat exchanger having a ground heat exchange structure formed by using at least three resin fluid paths having a return path flowing toward the front side.   The underground heat exchanger according to claim 1, wherein the underground heat exchange structure includes an interval holding member that holds an interval between the fluid paths at a predetermined interval.   3. The underground heat exchange according to claim 1, wherein the fluid path serving as the forward path or the return path maintains an interval of at least 7 cm between adjacent fluid paths serving as the forward path or the return path. vessel.   The number of the resin-made fluid paths which form the said underground heat exchange structure is 3-5, The underground heat exchanger in any one of Claims 1-3 characterized by the above-mentioned.   The contact point of each forward path and the return path of the resin fluid path is in a region where the depth is substantially the same, and each resin fluid path intersects in plan view. Underground heat exchanger.   The underground heat exchanger according to any one of claims 1 to 5, wherein the resin fluid path is a U-shaped pipe made of a straight resin pipe.   A heat pump system using geothermal heat having the underground heat exchanger according to any one of claims 1 to 6 as a heat exchange device.