阅读说明：本技术 一种增强换热的方法 (Method for enhancing heat exchange ) 是由 田斌守 邵继新 夏斌 司双龙 冯启彪 蔺瑞山 杨海鸿 王本明 梁斌 雷海涛 于 2020-03-10 设计创作，主要内容包括：本发明涉及一种增强换热的方法,包括以下步骤：⑴按设计要求钻地热井；⑵在处于地表以下增温层的外层套管的外表面部分涂覆增强换热材料,使其与外层套管形成一个整体,并随外层套管一起下到地热井内；⑶将内层套管放入外层套管中,使内层套管与外层套管形成同轴双层套管；⑷当下管结束后,根据打井时地层含水情况,在外层套管外表面与钻孔间的缝隙处慢慢注水,边观察边注入,使增强换热材料浸水6~8h后开始膨胀再固化；⑸换热介质由外层套管注入,并通过外层套管与地下高温岩体进行换热后,由内层套管输送至地面。本发明以同轴套管的外层套管作用换热管,有效增加了换热管与高温岩体间的接触面积和换热系数,提高了换热效率,并增加了单井的取热量。(The invention relates to a method for enhancing heat exchange, which comprises the following steps of ⑴ drilling a geothermal well according to design requirements, ⑵ coating an enhanced heat exchange material on the outer surface part of an outer sleeve of a temperature raising layer below the ground surface to form a whole with the outer sleeve, and putting the enhanced heat exchange material into the geothermal well along with the outer sleeve, ⑶ putting the inner sleeve into the outer sleeve to form a coaxial double-layer sleeve with the outer sleeve, ⑷ slowly injecting water into a gap between the outer surface of the outer sleeve and a drill hole according to the water containing condition of the underground layer when a well is drilled after the end of the lower sleeve, and observing and injecting the water to ensure that the enhanced heat exchange material is soaked in the water for 6-8 h and then expands and solidifies, ⑸ injecting a heat exchange medium into the outer sleeve, and carrying out heat exchange with underground high-temperature rock mass through the outer sleeve, and then conveying the underground high-temperature rock mass to the ground through the inner sleeve.)

1. A method of enhancing heat exchange comprising the steps of:

⑴ drilling geothermal wells as required by design;

⑵ coating the outer surface of the outer casing (2) of the temperature-increasing layer (8) below the surface with a heat exchange enhancing material (4) so that it is integral with the outer casing (2) and is lowered with the outer casing (2) into the geothermal well;

⑶ putting an inner sleeve (1) into the outer sleeve (2) to form a coaxial double-layer sleeve by the inner sleeve (1) and the outer sleeve (2);

⑷ after the down pipe is finished, according to the water containing condition of the ground layer when the well is drilled, slowly injecting water into the gap between the outer surface of the outer casing (2) and the drilled hole while observing, so that the reinforced heat exchange material (4) begins to expand and solidify after being soaked for 6-8 hours;

⑸ heat exchange medium is injected from the outer casing (2), and after heat exchange is carried out between the outer casing (2) and the underground high-temperature rock (5), the heat exchange medium is conveyed to the ground by the inner casing (1).

2. The method of claim 1, wherein the heat exchange enhancing material (4) of step ⑵ is a time-lapse expansion-cured material having a thermal conductivity greater than 2.0W/(m.K).

3. A method of enhanced heat transfer as claimed in claim 1 wherein said step ⑵ is replaced by coating the outer surface portion of the outer casing (2) in the temperature-increasing layer (8) below the surface of the earth with the enhanced heat transfer material (4) and coating the outer surface portion of the outer casing (2) in the temperature-changing layer (6) and the temperature-maintaining layer (7) below the surface of the earth with the enhanced heat transfer material (4), the enhanced heat transfer material (3) and the outer casing (2) together to be integrated and run down into the geothermal well with the outer casing (2).

4. The method for enhancing heat exchange of claim 1, wherein the step ⑷ is replaced by a method that after the down pipe is finished, water is slowly injected into the gap between the outer surface of the outer casing (2) and the drilled hole according to the water content of the well-digging stratum, the water is injected while observing, and the heat exchange enhancing material (4) and the heat insulation enhancing material (3) begin to expand and solidify after being soaked in water for 6-8 hours.

5. A method of enhancing heat exchange as claimed in claim 3 or claim 4, wherein: the reinforced heat-insulating material (3) is a time-delay expansion curing material with the heat conductivity coefficient smaller than that of soil below the earth surface after expansion curing.

Technical Field

The invention relates to the technical field of development and utilization of middle-deep geothermal energy, in particular to a method for enhancing heat exchange.

Background

Geothermal energy is a clean and pollution-free new energy source, and has huge reserves, wide distribution and great development potential. China is rich in geothermal resources, mainly medium-low temperature resources, and has more than 4000 hot water points (including hot springs, drill holes and pit hot water) with water temperature of more than 25 ℃ which are found in China and are widely distributed.

In recent years, with the increasing environmental pressure, the demand for geothermal energy utilization is rapidly increasing, and there are two main ways of direct utilization and indirect utilization: the direct utilization is to extract underground hot water to utilize the geothermal energy, and has the defects of difficult recharge, high recharge cost, polluted underground water resources, sunken foundations and the like. The indirect utilization is to take out geothermal energy for utilization through a heat exchange device, the indirect utilization is to drill a well to a certain depth underground, a double-layer sleeve is put into the well, an outer pipe is in contact with a high-temperature rock mass underground, a heat exchange medium is injected from the outer pipe, an inner pipe flows out, and the geothermal energy is continuously output to the ground through the cyclic reciprocation of the heat exchange medium, so that the technology is a new technology for 'taking heat without taking water'. According to the temperature change condition of the heat exchange medium in the heat exchange system, the temperature of the heat exchange medium in the temperature changing layer and the constant temperature layer is higher than the temperature of soil, so that in order to reduce heat loss, the heat preservation of the section of pipeline is enhanced, and the heat loss in the heat exchange medium to the soil is reduced to the maximum extent; in the temperature increasing layer, the temperature of the heat exchange medium is lower than that of the rock stratum, and heat needs to be exchanged from the rock stratum to the heat exchange medium, so that the heat conductivity coefficient of the pipeline is increased, and heat exchange is enhanced. However, because the heat exchange system is drilled and then a pipeline is put into the well, the surface of the underground heat exchange pipe is difficult to be completely and tightly contacted with a soil layer and a high-temperature rock mass, and a gap exists, so that the heat loss in the heat preservation section is increased; the heat exchange area between the rock stratum and the outer sleeve in the heat exchange section is limited, the heat exchange resistance is large, and the heat exchange efficiency is low.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for enhancing heat exchange, which increases the contact area and improves the heat exchange efficiency.

In order to solve the above problems, the method for enhancing heat exchange of the present invention comprises the following steps:

⑴ drilling geothermal wells as required by design;

⑵ coating the outer surface of the outer casing of the temperature increasing layer below the surface with heat exchange enhancing material to form a whole with the outer casing and to be lowered into the geothermal well together with the outer casing;

⑶ placing an inner sleeve into the outer sleeve to form a coaxial double-layer sleeve;

⑷ after the down pipe is finished, according to the water containing condition of the ground layer when the well is drilled, slowly injecting water into the gap between the outer surface of the outer casing and the drilled hole while observing, so that the reinforced heat exchange material begins to expand and solidify after being soaked in water for 6-8 hours;

⑸ heat exchange medium is injected from the outer casing pipe, and after heat exchange is carried out between the outer casing pipe and the underground high-temperature rock mass, the heat exchange medium is conveyed to the ground by the inner casing pipe.

The heat exchange enhancing material in the step ⑵ is a time-delay expansion curing material with a thermal conductivity coefficient larger than 2.0W/(m.K).

Step ⑵ is replaced by applying a heat exchange enhancing material to the outer surface portion of the outer casing in the temperature increasing layer below the surface of the earth and applying a heat insulating enhancing material to the outer surface portions of the outer casing in the temperature changing layer and the temperature constant layer below the surface of the earth such that the heat exchange enhancing material, the heat insulating enhancing material and the outer casing form a unitary body and are lowered into the geothermal well with the outer casing.

And the step ⑷ is replaced by a method that after the down pipe is finished, water is slowly injected into a gap between the outer surface of the outer casing and the drilled hole according to the water containing condition of the ground layer during well drilling, the water is injected while observing, and the reinforced heat exchange material and the reinforced heat insulation material begin to expand and then solidify after being soaked for 6-8 hours.

The reinforced heat insulation material is a time-delay expansion curing material with the heat conductivity coefficient smaller than that of soil below the ground surface after expansion curing.

Compared with the prior art, the invention has the following advantages:

1. because the outer sleeve of the coaxial sleeve acts on the heat exchange tube, the outer surface of the outer sleeve is coated with the enhanced heat exchange section of the enhanced heat exchange material, and meanwhile, the enhanced heat exchange material is a time-delay expansion curing material with the heat conductivity coefficient larger than 2.0W/(m.K), the contact area and the heat exchange coefficient between the heat exchange tube and the high-temperature rock mass are effectively increased, the heat exchange efficiency is improved, and the heat taking amount of a single well is increased.

2. The invention is provided with the heat preservation section with the reinforced heat preservation material, thereby reducing the heat loss of the heat exchange medium in the outer layer sleeve through the temperature change layer and the constant temperature layer section below the earth surface and enhancing the heat preservation property.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is another schematic structural diagram of the present invention.

In the figure: 1-inner layer sleeve; 2-outer casing; 3-reinforcing heat-insulating material; 4-heat exchange enhancing material; 5-high temperature rock mass; 6-temperature changing layer; 7-a constant temperature layer; 8-a temperature increasing layer; 9-heat preservation section; 10-enhancement of the heat exchange section.

Detailed Description