Backfill material for buried pipe of ground-source heat pump system, and backfilling method thereof

A soil source heat pump, system-based technology, applied in the direction of filling, etc., can solve the problems of shrinking prone to a large number of cracks, low heat transfer capacity, reduced heat transfer effect, etc., to achieve low heat transfer time constant, low economic cost, and heat transfer. Efficiency-enhancing effect

Inactive Publication Date: 2013-11-20
HUNAN ZHONGBO ENERGY TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Mortar concrete is suitable for places with low water content, and places with high water content have low permeability, which reduces the heat transfer effect
The thermal conductivity of bentonite-based backfill is low, and in the case of drying and water loss, severe shrinkage is prone to a large number of cracks

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] Embodiment 1: hard rock mass, such as marble (hardness coefficient f=8), its water content is lower than 5% (mass), selects the coarse sand of 0.6mm, the superabsorbent resin that adopts is methyl methacrylate, The proportion of ordinary sand and resin is 10:1. After backfilling, its thermal conductivity is not lower than that of the surrounding rock mass. Compared with cement-based backfill, the thermal conductivity is increased by 20%. Compared with bentonite-based backfill, Thermal conductivity increased by 25%.

Embodiment 2

[0020] Example 2: general soil geological conditions, such as hardened clay (hardness coefficient f=1.5), its water content is about 45% (mass), select 0.35mm fine sand, and the super absorbent resin used is cross-linked polyacrylic acid The proportion of sodium, ordinary sand and resin is 13:1. After backfilling, its thermal conductivity is much higher than that of the surrounding soil, and its moisture content is also much higher than that of the surrounding soil. After testing, compared with cement-based backfill, the thermal conductivity is increased by 45%, and compared with bentonite-based backfill, the thermal conductivity is increased by 30%.

Embodiment 3

[0021] Embodiment 3: For clayey soil (hardness coefficient f=1), high water content area (water content higher than 60% (mass)), select 0.3mm fine sand, the superabsorbent resin that adopts is methyl methacrylate , the ratio of ordinary sand to resin is 15:1, and its thermal conductivity is not lower than that of the surrounding rock mass. Compared with cement-based backfill, the thermal conductivity is increased by 25%, and compared with bentonite-based backfill, the thermal conductivity is improved. 31%.

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PUM

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Abstract

The invention discloses a backfill material for buried pipe of ground-source heat pump system and a backfilling method of the backfill material. The backfill material is prepared by steps of mixing normal sands and non-degradable polymer type polyacrylic acid series super absorbent resin according to a volume ratio of 10:1-15:1, stirring and standing. The method comprises the following steps of: firstly determining the type of normal sands according to the type of rock and soil body of a soil source, then, according to the moisture content and the thermal conductivity of the soil source, mixing the normal sands and the non-degradable polymer type polyacrylic acid series super absorbent resin according to the volume ratio of 10:1-15:1, stirring and standing, and finally backfilling. The backfill material provided by the invention has short thermal storage time and low heat transfer time coefficient, so that the heat conducting effect of the backfill material is improved. According to the method, when the normal sands are mixed with the super absorbent resin, the water penetrability is improved, the mobility of water in gaps of sands is promoted, and the heat transfer efficiency of the backfill material is enhanced.

Description

technical field [0001] The invention relates to a backfill material, in particular to a backfill material used for buried pipes of a soil source heat pump system. Background technique [0002] The early backfill materials mostly used a mixture of bentonite and water inherited from the geological drilling process. The thermal conductivity of this backfill material is only about 0.65-0.9W / (m·K), which is far lower than that of the rock and soil layer. (1.7 W / (m·K)~3.4 W / (m·K)), and this kind of backfill material is easy to dry and shrink and cause it to fall off from the U-shaped tube, which has an adverse effect on heat transfer and greatly affects the performance of the heat exchanger. [0003] In recent years, the research on enhanced heat transfer backfill materials has gradually become a hot spot. P. Kavanaugh and L. Allan believed that enhanced heat transfer backfill materials can greatly improve the heat transfer capacity of drilling heat exchangers compared with trad...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B26/06E02D17/18
Inventor 蔡博康书硕马子龙旷正伟
Owner HUNAN ZHONGBO ENERGY TECH
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