GROUT MATERIAL FOR HEAT TRANSFER

Abstract

A grout material for heat transfer according to the present invention comprises a sand particle; and an outer layer coated on the surface of individual sand particle, wherein the outer layer is composed of a mixture of graphite powder and a hydraulic inorganic binder.

A method for producing the grout material for heat transfer according to the present invention comprises the steps of: mixing graphite powder and a hydraulic inorganic binder; coating the mixture of graphite powder and the hydraulic inorganic binder on the outer surface of the sand particles while stirring the sand particles by spraying water; curing the hydraulic inorganic binder on the sand particles on which the mixture of graphite powder and the hydraulic inorganic binder is coated; and drying the sand particles on which the mixture of graphite powder and the hydraulic inorganic binder is coated.

The grout material for heat transfer is mixed with the mixture of water and bentonite powder to form a slurry and is used for a grouting process in which the prepared slurry is injected to give water-proof property to the grout material for heat transfer.

Claims

1. A grout material for heat transfer comprising: a sand particle; and an outer layer coated on the surface of an individual sand particle, wherein the outer layer is composed of a mixture of graphite powder and a hydraulic inorganic binder.

2. The grout material for heat transfer according to claim 1, wherein the hydraulic inorganic binder is selected from the group consisting of cement, gypsum, and sodium silicate.

3. The grout material for heat transfer according to claim 2, wherein the hydraulic inorganic binder is cement.

4. The grout material for heat transfer according to claim 2, wherein the cement is an alumina-based rapid setting cement.

5. The grout material for heat transfer according to claim 1, wherein the graphite powder in the outer layer is 0.1 to 10 wt. % based on the weight of the sand particle.

6. The grout material for heat transfer according to claim 1, wherein the hydraulic inorganic binder in the outer layer is 1 to 10 wt. % based on the weight of the sand particle.

7. A method for producing the grout material for heat transfer according to claim 1 comprising the steps of: mixing graphite powder and a hydraulic inorganic binder; coating the mixture of graphite powder and the hydraulic inorganic binder on the outer surface of the sand particles while stirring the sand particles by spraying water; curing the hydraulic inorganic binder the sand particles on which the mixture of graphite powder and the hydraulic inorganic binder is coated; and drying the sand particles on which the mixture of graphite powder and the hydraulic inorganic binder is coated.

8. A method of grouting process comprising the steps of: mixing water and bentonite powder and forming bentonite slurry; making the mixture slurry of the bentonite slurry and the grout material for heat transfer according to claim 1; and injecting the mixture slurry into the boreholes to give water-proof property to the grout material for heat transfer.

9. The method of grouting process according to claim 8, wherein the mixing ratio of the grout material for heat transfer and bentonite powder is 5:1 to 8:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other aspects, features, and advantages of certain preferred embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0033] FIG. 1 is a cross-sectional view of a grout material for heat transfer according to the present invention;

[0034] FIG. 2 is a photograph showing the dried state of the grout material for heat transfer according to the present invention; and,

[0035] FIG. 3 is a photograph showing the mixed state of the grout material for heat transfer according to the present invention with water to form mixture slurry.

DETAILED DESCRIPTION

[0036] In this specification, the expressions “have”, “includes”, “comprises”, etc. refer to the presence of a feature and do not preclude the presence of additional features.

[0037] All terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art.

[0038] Commonly used predefined terms may be construed as having the same or similar meaning as the contextual meanings of the related art and are not to be construed as an ideal or overly formal sense unless expressly defined to the contrary herein. In some cases, the terms defined herein may not be construed to exclude embodiments of the present invention.

[0039] The advantages and features of the present invention and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various other forms, and the present embodiments have only the purpose of thorough disclosure of the present invention.

[0040] FIG. 1 is a diagram showing a cross-section of a grout material for heat transfer 1 according to the present invention, the grout material for heat transfer 1 is composed of a sand particle 2 and an outer layer 3 coated on the sand particle 2.

[0041] As the sand used for the grout material for heat transfer 1 of the present invention, river sand collected from a river or crushed sand obtained by crushing silica rock can be used. Although the shape of the river sand is relatively close to a spherical shape, it often contains organic material and other minerals, so it must be washed, separated, and classified (sieved). Though the shape of the crushed sand is sharp, and irregular compared to that of river sand, washing and/or separating processes are not required and only sieving is required.

[0042] The size of sand that can be used is No. 2 (4-8 mesh 4.75-2.36 mm) or No. 3 (8-12 mesh 2.36-1.70 mm), but not limited thereto.

[0043] In the present invention, a grout material for heat transfer 1 is prepared by coating an outer layer 3 composed of a mixture of a hydraulic inorganic binder 4 and graphite powder 5 on the outside surface of the sand particle 2.

[0044] The hydraulic inorganic binder 4 which is used in the outer layer 3 is selected from the group consisting of cement, gypsum, or sodium silicate, preferably cement, and most preferably alumina-based rapid setting cement.

[0045] To manufacture the grout material for heat transfer 1 which has the above configuration, river sand or crushed sand described above is prepared at first.

[0046] Next, a mixture for coating the outer layer 3 is formed by mixing the hydraulic inorganic binder 4 and graphite powder 5.

[0047] Though there is no particular limitation on the hydraulic inorganic binder 4 and graphite powder 5 constituting the outer layer 3, in the case of graphite, the thermal conductivity of the grout depends on the content of the graphite, but the manufacturing cost also increases accordingly, and the thermal conductivity is not proportional to the content of graphite. Preferably, the content of graphite powder 5 in the outer layer 3 is 0.1 to 10 wt. % based on the weight of the sand particles 2.

[0048] It is preferable that the hydraulic inorganic binder 4 in the outer layer is 1 to 10 wt. % based on the weight of the sand particles 2.

[0049] The mixture for coating outer layer 3, which is formed by mixing the hydraulic inorganic binder 4 and graphite powder 5 as described, and sand particles 2 are placed in an industrial mixer and stirred while the mixture of graphite powder 5 and the hydraulic inorganic binder 4 is coated on the sand particles 2.

[0050] Thereafter, water is sprayed on the sand particles 2 on which the mixture of the hydraulic inorganic binder 4 and graphite powder 5 are coated as the outer layer 2, and the hydraulic inorganic binder 4 in the outer layer 2 is formed. If the inorganic binder 4 is set in this way, even if the grout material for transfer is mixed with water and bentonite slurry during the subsequent grouting process and injected into underground heat exchangers, the graphite powder dispersed in the hydraulic inorganic binder is not easily separated. Therefore, the separation phenomenon due to the difference in specific gravity between the grout materials is significantly reduced.

[0051] The grout material for heat transfer 1 formed as described above can be used in the construction site after a drying treatment.

[0052] FIG. 2 shows the grout material for heat transfer 1 according to the present invention which is manufactured through the process as above.

[0053] A method of grouting process using the grout material for heat transfer 1, which is prepared as described above for the injection process into the underground boreholes, will be described.

[0054] Two important functions in the grouting process for an underground boreholes are heat transfer and the water-proof property. In the conventional grouting process for underground boreholes construction, bentonite slurry has been used for water-proof despite that the thermal conductivity of bentonite is low. According to the present invention, the grout material for heat transfer with high thermal conductivity is used, therefore, the heat transfer is already secured satisfactorily, and the second function of the grout material, namely water-proof property can be controlled by changing the composition and content of the bentonite slurry as required in the construction site before the injection process.

[0055] In the grouting process according to the present invention, water and bentonite powder are mixed at first. Then, the above bentonite slurry is again mixed with the grout material for heat transfer 1 according to the present invention to form a mixture slurry as shown in FIG. 3. This slurry thus formed is injected into the underground boreholes during construction.

[0056] In this specification, the present invention and its advantages have been described with reference to a specific embodiment. However, it will be apparent to those of ordinary skill in the art that various modifications and changes can be made without departing from the scope of the present invention as described in the claims below. Accordingly, the specification and drawings are to be regarded as examples of the invention rather than limitations. All such possible modifications should be made within the scope of the present invention.