JP2015055365A - Heat collecting pipe for underground thermal heat pump system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat collecting pipe for an underground thermal heat pump system of which construction cost is reduced and heat exchange efficiency is improved.SOLUTION: A heat collecting pipe 3 shows a double pipe structure comprising an outer pipe 11 and an inner pipe 12. The outer pipe 11 is made of metal and the inner pipe 12 is made of resin. There is provided a flow passage where after heat medium flows in the inner pipe 12, the heat medium is returned back through a heat collecting passage 13 between the outer pipe 11 and the inner pipe 12. It is satisfactory that a punched hole diameter of a vertical hole 2 so as to cause the heat collecting pipe 3 to be laid in the ground is slightly larger than an outer circumference of the outer pipe 11, and the punched vertical hole 2 can be utilized effectively, so that a construction cost for punching the vertical hole 2 can be reduced. Since metal with higher coefficient of thermal conductivity as compared with that of resin is used as a material for the outer pipe 11, the underground heat is transmitted efficiently to the heat medium and much amount of underground thermal energy can be collected. In turn, since the inner pipe 12 is made of resin, thermal giving or receiving amount between the heat medium flowing in the inner pipe and the heat medium flowing in the heat collecting passage 13 is quite low, it is possible to keep a high heat exchange efficiency.

Description

  The present invention relates to a heat collecting tube for a geothermal heat pump system that uses thermal energy extracted by a heat collecting tube disposed in the ground for air conditioning, snow melting, floor heating, and the like.

In recent years, cooling and heating systems, snow melting systems, hot water supply systems, floor heating systems, etc. that use geothermal heat have been actively installed due to advantages such as the use of natural energy, suppression of CO ₂ emissions, environmental conservation, and energy saving. .

  The system using the underground heat extracts a portion of the ground, for example, 10 to 100 m of thermal energy (about 15 to 18 ° C.) by a heat exchanger and uses it for various applications.

  Conventionally, as the heat collection tube, for example, as shown in Patent Documents 1 to 3 below, by connecting the lower ends of two straight tubes arranged in parallel, one is a U-shape with the other as a forward path and the other as a return path Many pipes are used. As the material of the heat collecting tube, a resin material such as polyethylene having excellent corrosion resistance is mainly used.

  Further, for example, in Patent Documents 2 and 3 below, two forward pipes and two return pipes are provided for one vertical hole in order to obtain a large ground heat transfer area by one drilling. In this way, two U-shaped pipes are integrated and arranged. As a result, a large heat exchange area can be obtained by drilling one vertical hole.

JP-A 61-272592 Japanese Patent Application Laid-Open No. 11-182942 JP 2012-127116 A

  However, in the thing of the said patent documents 1-3, since the two straight pipes are arranged in parallel as a heat collection pipe and it is formed in the U shape which made the lower end communicate, it is necessary to make the drilling diameter of a vertical hole large. There was a problem that the construction cost for drilling the vertical holes increased. For example, when a pipe with a nominal diameter of 25A is used, the product width including the U-shaped joint at the lower end is about 84 mm. Therefore, it is necessary to drill with a diameter slightly larger than this in order to allow room for insertion of the heat collecting pipe. It was. Further, when two sets of U-shaped pipes are integrated and arranged as in Patent Documents 2 and 3, a diameter 1.2 to 1.3 times larger than this is required, which is about 105 mm. A drilling diameter is required.

  In addition, in the conventional heat collecting tube, a resin made of polyethylene or the like is often used in consideration of corrosion resistance when placed in the ground for a long period of time, but the heat conductivity of polyethylene resin is 0. .46-0.50 W / mK and quite small. For this reason, heat exchange with the ground was not performed efficiently, and the recovery efficiency of heat energy was poor.

  Then, the main subject of this invention is providing the heat-collecting pipe | tube for underground heat pump systems which reduced the construction cost and improved the heat exchange efficiency.

In order to solve the above-mentioned problem, as the present invention according to claim 1, a heat collection tube used in a heat pump system using underground heat,
The heat collection tube has a double tube structure composed of an outer tube and an inner tube, the outer tube is made of metal, the inner tube is made of resin, and a heat medium passes through the inner tube. There is provided a heat collecting pipe for a ground heat pump system, characterized in that a flow path returning through a space between the outer pipe and the inner pipe is formed after distribution.

  In the invention of claim 1, the heat collecting pipe for collecting the heat energy in the ground as the underground heat exchanger has a double structure composed of the outer pipe and the inner pipe, and the outer pipe is made of metal. The inner tube is made of resin. In this heat collecting pipe, since a flow path is formed in which the heat medium flows through the inside of the inner pipe and then returned through the space between the outer pipe and the inner pipe, the supply side (inner pipe) Compared with the heat collection side (outer tube), the surface area in contact with the heat medium becomes larger, which is more advantageous for heat collection. Further, when a metal is used as the outer tube, the thermal conductivity of the metal (16.0 W / mK in the case of SUS304 stainless steel) is the thermal conductivity of the polyethylene resin (0.46 to 0.50 W / mK). Since the value is much higher than that of, the underground heat can be efficiently transferred to the heating medium, and more underground heat energy can be collected. On the other hand, since the inner tube is made of resin, heat exchange between the heat medium flowing through the inner tube and the heat medium flowing through the space between the inner tube and the outer tube is negligible. Efficiency can be maintained.

  Thus, since the heat collection efficiency is higher than that of the conventional one, it is possible to reduce the number of the entire heat collection tubes. Therefore, the construction cost of the vertical hole for laying the heat collection tube can be reduced. In addition, since the heat collecting pipe has a double pipe structure consisting of an outer pipe and an inner pipe, the diameter of the vertical hole to be drilled may be slightly larger than the outer circumference of the outer pipe, and the drilled vertical hole is wasted. Therefore, the construction cost for drilling the vertical hole can be reduced.

  According to a second aspect of the present invention, there is provided the heat collecting pipe for a geothermal heat pump system according to the first aspect, wherein the outer pipe is made of a metal having corrosion resistance or a metal subjected to a corrosion resistance treatment.

  In the invention according to claim 2, the outer tube is subjected to corrosion resistance treatment such as application of a rust preventive agent, resin coating, corrosion-resistant sheath coating, amorphous metal coating on the outer surface of a metal having corrosion resistance such as stainless steel or amorphous metal. By being made of metal, it has excellent corrosion resistance and can withstand long-term use.

  As a third aspect of the present invention according to claim 3, the cross-sectional area of the space between the outer tube and the inner tube is formed larger than the cross-sectional area inside the inner tube. A heat collection tube for a thermal heat pump system is provided.

  In the invention according to claim 3, the flow rate of the heat medium flowing through the inside of the inner pipe is formed by making the cross-sectional area of the space between the outer pipe and the inner pipe larger than the cross-sectional area inside the inner pipe. Accordingly, the flow rate of the heat medium flowing through the space between the outer tube and the inner tube becomes slower, so that more heat exchange is performed between the underground and the heat medium.

  According to a fourth aspect of the present invention, there is provided a heat collecting pipe for a geothermal heat pump system according to any one of the first to third aspects, wherein the outer pipe is a corrugated pipe.

  In the invention according to claim 4, by using a corrugated tube whose surface is corrugated as the outer tube, the contact area between the underground and the outer tube is increased, the heat exchange efficiency is increased, and the crustal deformation It is easy to cope with.

  As described above in detail, according to the present invention, in the heat collecting pipe used in the heat pump system using underground heat, the construction cost of the heat collecting pipe can be reduced and the heat exchange efficiency is improved.

1 is a configuration diagram of a geothermal heat pump system 1 according to the present invention. 3 is a longitudinal sectional view of a heat collecting tube 3. FIG. It is a cross-sectional view (III-III line arrow view of FIG. 2) of the heat collecting tube 3. It is a partially broken front view which shows the heat collection pipe | tube 3 concerning the other form example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  A geothermal heat pump system 1 according to the present invention is a heat pump system using geothermal heat as a heat source. In such a heat pump system, since the temperature of the ground changes and is stable throughout the year compared to the outside air temperature, it can be used as a heat source in the summer and as a heat source in the winter, and it is more energy efficient than air-based heat sources. At the same time, since heat is not discharged to the outside air, the heat island phenomenon can be reduced.

  Specifically, as shown in FIG. 1, the structure of the main underground heat pump system 1 is laid in a vertical hole 2 drilled in the ground, and a heat collecting pipe 3 for exchanging heat with the ground, and the above-described sampling. Heat exchange is performed between the heat exchanger 4 that exchanges heat with the heat medium that has passed through the heat pipe 3, the compressor 5, and the heat medium that flows through the indoor load 8 such as an air conditioner or a floor heater. It mainly comprises a heat exchanger 6 to be performed and an expansion valve 7.

  The heat exchanger 4, the compressor 5, the heat exchanger 6 and the expansion valve 7 are connected by piping, and a working fluid such as water or antifreeze that circulates these is enclosed. In addition, the heat collecting pipe 3 and the heat exchanger 4 are connected by piping, and a heat medium such as water or antifreeze liquid circulating through them is enclosed, and a pump 9 for circulating the heat medium is disposed in the middle of the heat collecting pipe 3 and the heat exchanger 4. It is installed. Furthermore, the indoor load 8 and the heat exchanger 6 are connected by piping, and a heat medium such as water and antifreeze liquid circulating through them is enclosed, and a pump 10 for circulating the heat medium in the middle is provided. It is arranged.

  In summer, the heat collecting pipe 3 takes out the cold in the ground (releases heat into the ground), the heat exchanger 4 acts as a condenser, and the heat exchanger 6 acts as an evaporator, The working fluid of the heat pump is circulated in the order of heat exchanger 4 (condenser) → expansion valve 7 → heat exchanger 6 (evaporator) → compressor 5, and cold energy is utilized at the indoor load 8. In the winter season, heat is extracted from the ground by the heat collecting tube 3, the heat exchanger 4 acts as an evaporator, the heat exchanger 6 acts as a condenser, and the working fluid of the heat pump is used as the heat exchanger 4 (Evaporator) → Compressor 5 → Heat exchanger 6 (Condenser) → Expansion valve 7 are circulated in this order, and the indoor load 8 uses the heat.

  The vertical hole 2 is a hole which is drilled substantially vertically from the ground surface by a rotary drilling device in which the tip of the bit rotates or a hybrid drilling device to which vibration is added. As the drill device, one having a digging depth of about 50 m to 150 m is used, and the vertical hole 2 having a depth of about 20 m to 100 m is excavated.

  In order to lay the heat collecting pipe 3 in the vertical hole 2, after the vertical hole 2 is drilled, the heat collecting pipe 3 is inserted, and if necessary, the periphery thereof is filled with a filler G such as soil or grout material. To do.

  The perforation diameter of the vertical hole 2 may be formed with a diameter slightly larger than the diameter of the outer tube 11, and specifically with a diameter of about 2 mm to 10 mm. Compared with a conventional U-shaped heat exchange pipe having a flow path cross-sectional area of approximately the same as the main heat collecting pipe 3, the bore diameter of the vertical hole can be reduced to about half. Construction costs for drilling can be reduced.

  As shown in FIGS. 2 and 3, the heat collecting tube 3 has a coaxial double tube structure including an outer tube 11 and an inner tube 12. Most of the heat collecting tubes 3 are embedded in the vertical holes 2 and their upper ends extend from the ground surface.

  The outer tube 11 is made of metal. As a result, since the thermal conductivity of the metal is much higher than that of the resin, the underground heat can be collected efficiently. As the metal, it is desirable to use a metal having corrosion resistance or a metal having at least an outer surface subjected to corrosion resistance treatment. Examples of the corrosion-resistant metal include stainless steel and amorphous metal. As the stainless steel, SUS304, SUS316, SUS410S, or the like can be used. In the case of SUS304, the thermal conductivity of stainless steel is 16.0 W / mK at a temperature of 300 K, which is about 32 to 35 times higher than that of high-density polyethylene (0.46 to 0.50 W / mK). Indicates the value. Therefore, by making the outer tube 11 in direct contact with the ground made of stainless steel, the heat exchange efficiency between the ground and the heat medium flowing in the interior is increased. The amorphous metal is an amorphous metal in which atoms are randomly arranged, and has particularly excellent properties in corrosion resistance.

  Further, when the outer tube 11 is made of stainless steel and disposed in the ground for a long time, corrosion of the outer tube 11 becomes a problem. Therefore, it is desirable to subject the outer surface of the outer tube 11 to corrosion resistance. Examples of the anticorrosion treatment include application of a rust preventive agent, resin coating, anticorrosion sheath coating, and amorphous metal coating.

  Further, as the outer tube 11, as shown in FIG. 4, a stainless corrugated tube can be used. Since the corrugated tube has a cross-sectional shape with a corrugated surface, the contact area between the underground and the outer tube 11 is increased compared to a straight tube with a flat surface, and the heat exchange efficiency can be increased. At the same time, it becomes easy to cope with crustal deformation and the like by deforming the outer tube 11.

  The outer diameter of the outer tube 11 is 32 mm to 60.5 mm, preferably 45 mm to 50 mm. The thickness is 0.8 mm to 4 mm, preferably 1 mm to 1.5 mm.

  The lower end of the outer tube 11 is closed by a bottom plate 11 a made of the same material as the outer tube 11. On the other hand, an L-shaped elbow portion 11b is formed at the upper end, and an opening for inserting the inner tube 12 is provided at the upper end.

  As the inner tube 12, for example, a resin tube of high density polyethylene having a nominal diameter of 20A to 25A (outer diameter of 27 mm to 34 mm) is preferably used. It is also possible to use resin pipes such as cross-linked polyethylene, polypropylene, and polybuden.

  A space having a predetermined separation width S is provided between the outer surface of the inner tube 12 and the inner surface of the outer tube 11, and this space is a heat collecting path 13 in which heat exchange between the circulating heat medium and the ground is performed. It has become.

  The lower end of the inner tube 12 is held in a floating state with a predetermined height from the bottom plate 11a of the outer tube 11 by a support 12a. The support 12a is composed of a ring-shaped support portion 12b that opens at the center that supports the peripheral end portion of the inner tube 12, and a leg portion 12c that is erected at a predetermined height from the bottom plate 11a of the outer tube 11. ing. By disposing the support base 12a, the heat medium flowing through the inner pipe 12 is supplied to the outer pipe 11 at the lower end of the inner pipe 12, and the heat collecting path 13 between the outer pipe 11 and the inner pipe 12 is supplied. You will be able to enter. The height of the lower end of the inner tube 12 from the bottom plate 11a is preferably equal to or larger than the separation width S of the heat collecting passage 13 and smaller than the inner diameter of the inner tube 12.

  In addition, a plurality of center risers 14 at a predetermined pitch in the axial direction with respect to the outer periphery of the inner tube 12 so that the inner tube 12 can be disposed without being displaced substantially coaxially with respect to the outer tube 11. 14 are preferably arranged. As shown in FIG. 3, the center riser 14 has a ring portion 14 a that is externally fitted to the inner tube 12, and protrudes in the radial direction on the peripheral surface thereof, and is arranged at substantially equal intervals with a circumferential interval. The three spacer portions 14b, 14b,... The arrangement pitch in the axial direction is 1 m to 10 m, preferably 1 m to 5 m. The center riser 14 is fixed to at least the inner tube 12 with an adhesive or the like. Moreover, it is preferable to fix the front-end | tip of the spacer part 14b with the adhesive agent etc. with respect to the outer tube | pipe 11. FIG.

  In the heat collecting tube 3 having the above configuration, as shown in FIG. 1, the heat medium is supplied from the upper end of the inner tube 12 to the inside of the inner tube 12 by the pump 9, and the inside of the inner tube 12 faces the lower end. After distribution, a flow path is formed that is supplied from the lower end of the inner pipe 12 to the outer pipe 11 and is returned to the heat exchanger 4 through the space between the outer pipe 11 and the inner pipe 12 (heat collection path 13). Therefore, the heat collection side (outer tube 11) has a larger surface area in contact with the heat medium than the supply side (inner tube 12), which is more advantageous for heat collection. At this time, since a metal is used as the outer tube 11, for example, in the case of SUS304 stainless steel, the thermal conductivity is 16.0 W / mK, which is much higher than that of polyethylene resin (0.46 to 0.50 W / mK). Since it is a high value, it becomes easier for the underground heat to be transferred to the heat medium flowing through the heat collecting path 13 through the outer tube 11, so that more heat energy in the ground is collected by the heat medium flowing through the heat collecting path 13. become. On the other hand, since the inner tube 12 is made of resin, heat is transferred between the heat medium flowing inside the inner tube 12 and the heat medium flowing through the heat collecting path 13 between the inner tube 12 and the outer tube 11. Therefore, the high heat recovery efficiency of the heat medium flowing through the heat collecting path 13 can be maintained.

  Thus, since the amount of heat recovered per one heat collection tube 3 can be increased, the number of constructions of the entire heat collection tube 3 can be reduced, and the construction cost for drilling the vertical holes 2 can be greatly reduced. It also has the advantage of. Further, since the heat collecting tube 3 has a double tube structure composed of the outer tube 11 and the inner tube 12, the diameter of the vertical hole 2 to be drilled may be slightly larger than the outer diameter of the outer tube 11, and the hole is drilled. Since the vertical hole 2 can be effectively used without waste, the construction cost for drilling the vertical hole 2 can be reduced.

Incidentally, the cross-sectional area _{A 2} of the space (Tonetsuro 13) between the outer tube 11 and inner tube 12 is preferably larger than the inner tube 12 inside the cross-sectional area _{A 1 (A} 2> A ₁ ). As a result, the flow rate of the heat medium flowing through the heat collecting path 13 between the outer tube 11 and the inner tube 12 is relatively slower than the flow rate of the heat medium flowing through the inner tube 12, so And more heat exchange between the heat transfer medium and the heat medium. The cross-sectional area ratio A ₂ / A ₁ is preferably about 1.2 to 1.5.

  In addition, in order to prevent heat exchange with the ground or outside air near the ground surface that is easily affected by the heat of the outside air, the portion of the outer pipe 11 protruding from the ground and the vicinity of the ground surface that is easily affected by the outside air It is possible to take measures to make it difficult for heat conduction to occur by configuring the buried portion of the resin with resin instead of stainless steel, or by coating the outer surface of the stainless steel outer tube 11 with a heat insulating material or applying a thick resin coating. it can.

  DESCRIPTION OF SYMBOLS 1 ... Geothermal heat pump system, 2 ... Vertical hole, 3 ... Heat collection pipe, 4 ... Heat exchanger, 5 ... Compressor, 6 ... Heat exchanger, 7 ... Expansion valve, 8 ... Indoor load, 9 * 10 ... Pump, 11 ... Outer pipe, 12 ... Inner pipe, 13 ... Heat collection path, 14 ... Center riser

Claims (4)

A heat collection tube used in a heat pump system using geothermal heat,
The heat collection tube has a double tube structure composed of an outer tube and an inner tube, the outer tube is made of metal, the inner tube is made of resin, and a heat medium passes through the inner tube. A heat collecting pipe for a geothermal heat pump system, wherein a flow path returning through a space between the outer pipe and the inner pipe after being circulated is formed.   The heat collecting pipe for a geothermal heat pump system according to claim 1, wherein the outer pipe is made of a metal having corrosion resistance or a metal subjected to a corrosion resistance treatment.   The heat collecting pipe for a geothermal heat pump system according to any one of claims 1 and 2, wherein a cross-sectional area of a space between the outer pipe and the inner pipe is formed larger than a cross-sectional area inside the inner pipe.   The said outer pipe | tube consists of corrugated pipe | tubes, The heat collecting pipe | tube for underground heat pump systems in any one of Claims 1-3.

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