Special anti-cracking bentonite-based composite drill hole backfill material for ground source heat pump

Abstract

The invention relates to a special anti-cracking bentonite-based composite drill hole backfill material for a ground source heat pump. The special anti-cracking bentonite-based composite drill hole backfill material comprises the following components in parts by weight: 200 parts of bentonite, 800 parts of quartz sand and 0.9 kg / m<3> of motar / concrete crack-resistant fibers. The special anti-cracking bentonite-based composite drill hole backfill material disclosed by the invention can be used for improving a large quantity of cracks caused by intergranular cohesion change and nonuniform expansion and contraction in the drying and wetting circulating process of a bentonite-quartz sand type drill hole backfill material and preventing the surface water from being downwards infiltrated by closely filling a drill hole. The special anti-cracking bentonite-based composite drill hole backfill material disclosed by the invention can be used for reducing the heat resistance inside the drill hole due to good engineering characteristic when adopted for filling the drill hole, and can be used for reducing the depth of the drill hole and the length of a U-shaped pipe, thus reducing the initial assembly cost of the ground source heat pump and being contribute to the popularization and application of a ground source heat pump air-conditioning system which is low in energy consumption and environmentally friendly.

Description

technical field [0001] The invention belongs to the technical field of energy-saving and environment-friendly building materials and ground-source heat pump systems, and specifically relates to a crack-resistant bentonite-based composite drilling grouting backfill material for vertically buried pipe ground-source heat pumps. Background technique [0002] Shallow geothermal energy, as a clean and renewable energy source, does not produce greenhouse gases and various smoke and dust when utilized, and has zero pollution emissions, directly improving the air quality in the applicable area. The ground source heat pump is a kind of heat pump that utilizes shallow geothermal energy and flows through the closed underground pipe heat exchanger through the circulating fluid to realize the heat transfer between the system and the earth, which not only keeps the ground water heat pump using the earth as a cold and heat source It is a high-efficiency, energy-saving and environment-friend...

AI Technical Summary

Problems solved by technology

At present, commonly used drilling backfill materials are bentonite-fine sand (or cement) mixed slurry, cement-quartz sand-fine sand mixed slurry, ordinary cement or drilling cuttings, etc. The thermal conductivity of this backfill material is generally lower than 1.0W / (m·K), and it is easy to dry and shrink, crack and produce cracks, resulting in the backfill of the borehole is not dense, thereby reducing the thermal conductivity of the backfill material of the borehole and causing an increase in contact thermal resistance, which directly affects the heat transfer of the buried pipe heat exchanger. thermal performance

[0004] However, in practical engineering applications, due to the different temperature of the fluid in the two branches of the vertical U-shaped pipe, the lateral heat transfer between the two pipes will occur through the soil between the boreholes, resulting in a thermal short circuit, which will affect the heat transfer capacity of the entire buried pipe heat exchanger.

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