KR20130129722A - Method for installation of open loop type geothermal exchanger using incasing covered with water expansion material - Google Patents

Abstract

The present invention relates to a construction method of an open loop type geothermal exchanger, which completely cuts off the gap formed between the inner wall of a borehole and an inner casing pipe by simply installing the water expandable inner casing, which is formed by forming a water expandable material and a coating film on the outer surface of a pipe body, on the inner wall of the borehole; and remarkably reduces construction time and costs by not requiring a process for filling the gap.

Description

TECHNICAL FIELD OF INSTALLATION OF OPEN LOOP TYPE GEOTHERMAL EXCHANGER USING INCASING COVERED WITH WATER EXPANSION MATERIAL}

The present invention relates to an open loop type underground heat exchanger using an underground heat source, and more particularly, to a construction method of an open type underground heat exchanger for filling voids formed between an inner wall of a borehole and an outer wall of an encasing.

SCW (Standing Column Well) underground heat exchanger is an open type, as disclosed in Korean Patent Nos. 10-0675257, 10-0717391 and 10-07955336, to form artificial vertical wells with bore holes in the rock layers. And inserting a medium (such as groundwater or externally injected water) so that the geothermal heat can be obtained or discharged from the well, and then the medium is sent to a ground heat pump through an underwater pump installed and connected to a pump pipe. The heat exchange medium is again made of a structure that is recovered to the well via a return pipe.

However, until now, artificial vertical wells for implementing an open type underground heat exchanger, as shown in FIG. 1 (a), simply use the boreholes 5 in the underground rock layer 3 or use them, or FIG. 1 (b). Similarly, in addition to the out casing 4 for preventing the disintegration of the soil layer 1 during the excavation, a separate tube (in casing 10) has been embedded and used in the inner wall of the bore hole 5.

When the borehole itself is used as a well for obtaining heat sources, cracks or weak layers formed in the rock layers are depressed to prevent the flow of fluid (medium), and in the case of boreholes in which no groundwater exists, the medium is leaked and is always replenished. There is a problem that is needed.

In order to replenish the medium inside the well, and to fix the casing or leaking problems of the well by putting an in casing on the inner wall of the borehole, the present inventors have a geothermal energy heat exchange system having a groundwater replenishment device (Korean Patent No. 10-0576394 Has been developed.

As presented in Korean Patent No. 10-0576394, when the casing is embedded in the inner wall of the borehole, not only the groundwater inflow by the vein layer of the rock but also the outflow of the medium does not occur.

However, a gap 40 exists between the inner wall of the bore hole and the outer wall of the encasing, resulting in a problem that the thermal conductivity between the rock layer on which the bore hole is formed and the medium in the encasing falls.

The gap 40 generated between the inner wall of the bore hole and the outer wall of the encasing can be solved by filling with a grouting filler having good heat transfer characteristics.

By the way, the method of filling the entire bore hole except the geothermal transport pipe as a grouting filler in the hermetic heat exchanger using a pressure pump is known, but it can be applied as a method for filling the grouting filler in a narrow gap between the bore hole and the in casing. There is no problem.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a construction method of an open type underground heat exchanger using a water expansion encasing formed a water expansion member and a coating film on the outer peripheral surface of the tube.

In order to achieve the above object, the construction method of the open-type underground heat exchanger according to the present invention comprises the step of forming a bore hole of a predetermined depth in the ground, and inserting and installing an encasing in the bore hole inner wall In the construction method of the heat exchanger, the encasing, the tube body is inserted into the borehole inner wall; A water expandable member coated on the outer circumferential surface of the tube with a predetermined thickness; And a coating film formed on the upper front surface of the water-expandable member.

Here, the water-expandable member is another feature of the construction method of the open type underground heat exchanger according to the present invention that is applied to the entire outer peripheral surface of the tube.

The water-expandable member is formed of a material containing bentonite and silica sand, and the coating film is formed of a material including a natural adhesive that can be decomposed by reacting with water or moisture. With other features.

And, the thickness of the water expansion member is 1/7 to 1/3 of the distance between the inner wall of the bore hole and the outer peripheral surface of the tube, the water expansion member is formed of bentonite and silica sand, bentonite 80 ~ 90% by weight and 10-20% by weight of silica sand was mixed with water and then applied to the outer circumferential surface of the tube, and the water was evaporated and solidified to have a thickness of the water-expandable member. It features.

In addition, the coating film is formed of any one material selected from starch, glue and casein is another feature of the construction method of the open-type underground heat exchanger according to the present invention.

The construction method of the open type underground heat exchanger according to the present invention uses water expansion encasing in which the water expansion member and the coating film are formed on the outer circumferential surface of the tube, thereby simply installing the water expansion encasing according to the present invention on the inner wall of the borehole. It is possible to completely block the voids generated between the inner wall of the hole and the outer wall of the encasing tube, and there is an effect of not having to perform a separate process for filling the voids, thereby dramatically reducing the overall construction time and construction cost.

1 is a cross-sectional view showing a vertical well of the conventional open type underground heat exchanger, (a) is a case using the borehole itself as a well, (b) is a separate pipe (in casing) in the borehole inner wall This is the case.
Figure 2 is a vertical cross-sectional view showing an encasing structure for an open type underground heat exchanger according to an embodiment of the present invention.
Figure 3 is a horizontal cross-sectional view showing an encasing structure for an open type underground heat exchanger according to an embodiment of the present invention.
4 to 7 is a vertical cross-sectional view of each step showing a part of the construction method of the open-type underground heat exchanger according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

2 and 3 illustrate a vertical cross-sectional view and a horizontal cross-sectional view, respectively, for showing an open casing structure for an open type underground heat exchanger according to an embodiment of the present invention, and FIGS. 4 to 7 are views according to an embodiment of the present invention. The vertical cross section of each step which shows a part of construction method of an open type underground heat exchanger.

The construction method of the open-type underground heat exchanger according to an embodiment of the present invention is basically, as shown in FIG. 4, forming a bore hole 5 having a predetermined depth in the ground, and as shown in FIG. 5, on the inner wall of the bore hole. It is configured to include the step of inserting the encasing 100.

Here, the encasing 100, as shown in Fig. 2, the tubular body 10 is inserted into the inner wall of the bore hole (5); A water expandable member 20 coated on the outer circumferential surface of the tube with a predetermined thickness; And a coating film 30 formed on the upper front surface of the water expanding member.

In addition, the tubular body 10 is an impervious tube, and as shown in FIG. 7, a heat exchange medium is held inward, and the water pump 70 is provided in the medium and the pump pipe 50 surrounded by the heat insulating member 60. ) Will be located. Of course, the opening 52 is formed at the bottom of the pumping pipe 50 to allow the inflow of the medium.

The water-expandable member 20 may be formed of any material as long as the water-expandable member 20 has the property of absorbing and expanding moisture, and may include known bentonite, particularly sodium bentonite.

Sodium Bentonite is montmorillonite, in which Na ions are adsorbed on the bentonite surface as exchange ions, and are known to be more water-expandable than other bentonites. In other words, high-quality sodium bentonite reacts with water, expanding 13 to 16 times its original volume and absorbing water up to 5 times its weight.

In addition, the coating film 30, as shown in Figure 2, is coated on the upper front surface of the water-expandable member 20, which is the encasing 100 according to the present embodiment, as shown in Figure 5, the borehole ( 5) When the insert is installed in the borehole 5, the water expansion member 20 is grounded in the borehole 5 as well as the purpose of preventing the water expansion member 20 from falling off due to partial friction with the inner wall of the bore hole 5, etc. 20) is to prevent the expansion immediately.

However, since the coating film 30 is completely inserted into the bore hole 5 according to the present embodiment, after a predetermined time, ground water accumulated in the bore hole 5 or water injected from the outside or It should be formed of a material that can react with water to decompose or crack.

By the configuration as described above, when the total diameter is smaller than the borehole 5 inner diameter, the encasing 100 according to the present embodiment can be easily inserted and installed as shown in FIG. 5, and the encasing 100 is provided. Thereafter, the coating film 30 is decomposed or cracked by water or moisture in the bore hole 5, and the water-expandable member 20 expands in response to water or moisture in the bore hole 5, As shown in FIG. 7, the gap 40 between the tubular body 10 and the borehole 5 is easily blocked completely.

6 is a step of inserting and installing the encasing 100 in the borehole inner wall, as shown in FIG. 5, after which the water pump 70 is provided and inserts and installs the pumping pipe 50 surrounded by the heat insulating member 60. Although it is shown, this may be installed with the step of inserting the casing 100 or after the air gap 42 is completely filled with the casing 100 according to the present embodiment as shown in FIG. 7.

Therefore, the construction method of the open type underground heat exchanger according to the present embodiment uses the water expansion encasing 100 having the water expansion member 20 and the coating film 30 formed on the outer circumferential surface of the tubular body 10, thereby providing the borehole 5. By simply installing the water expansion encasing 100 according to the present embodiment on the inner wall, it is possible to completely block the voids 40 formed between the inner wall of the bore hole 5 and the encasing tube 10. The advantage of not having to proceed with a separate process to fill the total construction time and construction costs can be significantly reduced.

Hereinafter, embodiments that can implement the encasing 100 according to the above embodiment in more detail will be described.

First, the water-expandable member 20 may be applied only to a specific portion of the tubular body 10, but is preferably applied to the portion inserted into the bore hole 5 or the entire outer peripheral surface.

In addition, the material of the water-expandable member 20 may further include a material capable of increasing thermal conductivity, for example, silica sand (silica sand) in addition to the bentonite mentioned above.

At this time, the amount of bentonite to be partially reduced and the amount of silica sand can be added is determined in consideration of the thickness of the water-expandable member 20 and the gap (pore, 40) between the inner wall of the bore hole 5 and the outer peripheral surface of the tube body 10. It is preferable to.

Since the thickness of the coating film 30 is extremely thin compared to the thickness of the water expansion member 20 (the thickness of the coating film is 20 to 100/100 of the thickness of the water expansion member), the encasing 100 according to the above embodiment is In order to be easily inserted into the bore hole 5 without any problem, the thickness of the water-expandable member 20 is 1/7 to 1/3 of the distance between the inner wall of the bore hole 5 and the outer circumferential surface of the tube body 10. And more preferably 1/5.

When the thickness of the water-expandable member 20 is smaller than 1/7 of the distance between the inner wall of the bore hole 5 and the outer circumferential surface of the tubular body 10, the encasing 100 is easily inserted into the bore hole 5. However, due to the water-expansion limit of the mixed bentonite, it is difficult to completely fill the voids 40, and in particular, if there are cracks or irregularities in the rock constituting the borehole 5 wall, it remains as an empty space and reduces the overall thermal conductivity. However, if the gap between the inner wall and the outer circumferential surface of the tubular body 10 is larger than 1/3, the insertion of the bore hole 5 is difficult, and the water-expandable member 20 is peeled off due to rock fragments remaining on the inner wall of the bore hole. There is a problem that the increased portion is not achieved the original desired effect, that is, the purpose of filling the gap 40 completely without a gap.

As described above, when the thickness of the water-expandable member 20 is 1/7 to 1/3 of the distance between the inner wall of the bore hole 5 and the outer circumferential surface of the tube body 10, bentonite 80 to 90% by weight and silica It is preferable to mix the sand 10 to 20% by weight so that the water-expandable member 20 is formed.

This is because when the silica sand content is less than 10% by weight, the thermal conductivity increase effect is insignificant. However, when the silica sand content is more than 20% by weight, the bentonite content is reduced, making it difficult to completely fill the pores 40.

The mixing ratio for forming the water-expandable member 20 is more preferably 85% by weight of bentonite, 15% by weight of silica sand.

In addition, in order to solidify the water-expandable member 20 to the above-described thickness of the tubular body 10, bentonite and silica sand of the blending ratio are mixed with water, and then coated on the outer peripheral surface of the tubular body, and the water is evaporated. Will be worn.

Here, the content of water added in the process of mixing bentonite and silica sand is important. When water and bentonite are mixed, it becomes a thick gel phase and has a viscosity. Too much water makes it difficult for the bentonite to swell completely and to be dried in the next step. However, if too little water, only some bentonite swells and is difficult to apply.

Therefore, when the bentonite is blended, water is preferably added in an amount of 2 to 3 parts by weight, and the mixture is stirred and mixed at 300 rpm or more, and then applied to the outer circumferential surface of the tubular body 10, and the water is evaporated. The thickness of the water expandable member 20 is solidified so that the thickness of the water-expandable member 20 is 1/7 to 1/3 of the gap 40.

At this time, the soaked bentonite has a thixotropy, and if it does not flow, the viscosity becomes high and becomes a gel state of solid state, and when it flows at a high speed, the viscosity becomes low and becomes a sol state of liquid phase. It is easy to apply to (10) and after being applied, the fluidity is low so that the gel phase becomes easier the next drying process.

Next, the coating film 30, as described above, after the predetermined time passes after the encasing 100 is completely inserted into the borehole 5, water or water injected from the groundwater or externally accumulated in the borehole 5 Any material can be used as long as it can be decomposed or cracked by reaction with water, but is preferably formed of a material including a natural adhesive that can be decomposed by reacting with water or moisture.

Here, what can be used as the natural adhesive may be starch, glue and casein. In particular, in order to obtain the function (characteristic) of the coating film 30, it is preferable to use casein which is vegetable starch, animal glue and animal protein. They have the adhesive properties of the re-wetting type, so that the adhesive force is restored only by the moisture, and if the moisture is maintained, the solid phase characteristic is changed to the fluidized phase, thereby causing a gap, thereby functioning according to the purpose of the embodiment.

In addition, since the construction method of the unexplained open ground heat exchanger is generally known steps, the description thereof is omitted.

Configuration of each embodiment described above is presented as an example, various modifications are possible based on this, but will fall within the scope of the present invention as long as it is within the scope of the technical spirit described in the claims.

1: soil layer
2: boundary layer
3: rock formation
4: out casing
5: bore hole
10: tube
20: water expansion member
30: coating film
40, 42: void
50: pump
52: opening sphere
60: insulation member
70: submersible pump
100: encasing

Claims (5)

In the construction method of the open underground heat exchanger comprising the step of forming a bore hole having a predetermined depth in the ground, and inserting the casing into the inner wall of the bore hole,
The ingaking,
Pipe body inserted into the borehole inner wall;
A water expandable member coated on the outer circumferential surface of the tube with a predetermined thickness; And
Construction method of the open-type underground heat exchanger comprising a coating film formed on the upper front surface of the water expansion member.
The method of claim 1,
The water expansion member is a construction method of the open type underground heat exchanger, characterized in that applied to the entire outer peripheral surface of the tube.
3. The method according to claim 1 or 2,
The water expansion member is formed of a material including bentonite and silica sand,
The coating film is a construction method of an open ground heat exchanger, characterized in that formed of a material containing a natural adhesive that can be decomposed by reacting with water or moisture.
The method of claim 3, wherein
The thickness of the water expansion member is 1/7 to 1/3 of the interval between the inner wall of the bore hole and the outer peripheral surface of the tube,
The water-expansion member is formed of bentonite and silica sand, mixed with 80 to 90% by weight of bentonite and 10 to 20% by weight of silica sand with water and then applied to the outer peripheral surface of the tube, the water is evaporated to A construction method of an open type underground heat exchanger, characterized in that the solidified to a thickness.
5. The method of claim 4,
The coating film is a construction method of an open-type underground heat exchanger, characterized in that formed of any one selected from starch, glue, casein and shellac.

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