CN-121993910-A - Heat exchange system, filling process and evaluation method for biomineralization cementing backfill body buried pipe

CN121993910ACN 121993910 ACN121993910 ACN 121993910ACN-121993910-A

Abstract

The invention provides a heat exchange system, a filling process and an evaluation method of a biological mineralized cemented backfill body buried pipe, relates to the field of ground source heat pump engineering and geotechnical engineering reinforcement, and aims at solving the problems of unstable heat conduction performance, easiness in cracking, poor compactness and the like of traditional cement-based and bentonite-based backfill materials. The system comprises a water-proof heat-insulating box body, a drainage assembly, a backfill body and a heat exchange assembly, wherein the filling process comprises the steps of (1) EICP preparing treatment liquid, (2) treating sand of the backfill body, (3) paving the drainage assembly and the heat exchange assembly, (4) filling the backfill body, and evaluating through heat exchange quantity and energy efficiency coefficient of a buried pipe unit well depth. The invention is based on the environment-friendly EICP technology, uses soybean urease to hydrolyze urea to generate NH 4 + and CO 3 2‑ , and then reacts with an external calcium source to form calcium carbonate precipitate, and calcium carbonate crystals not only can bond soil particles, but also can construct more heat conduction paths, thereby remarkably improving the heat conductivity coefficient of backfill materials.

Inventors

CHEN NAN
HUANG MING
ZHENG WENJIE
CUI MINGJUAN
YANG QIANRU
DONG YILI
Chen Manqin

Assignees

福州大学

Dates

Publication Date: 20260508
Application Date: 20260403

Claims (10)

1. A heat exchange system of a biomineralization cementing backfill body buried pipe is characterized by comprising The waterproof insulation box body comprises a box body and a box cover, wherein the waterproof insulation box body sequentially comprises an impermeable film layer and an insulation board layer from the inner surface to the outer surface, and the inner surface of the insulation box body is also paved with inner geotextile; The drainage assembly comprises a plurality of drainage pipes, one end of each drainage pipe is positioned at the inner bottom of the waterproof insulation box body, the other end of each drainage pipe is connected with a drainage pump, the drainage pump is positioned outside the waterproof insulation box body, the drainage pipe positioned at the inner bottom of the waterproof insulation box body is a flower pipe, and the outside of the drainage pipe is wrapped with filter cloth; The backfill body comprises a plurality of sand and stone permeable layers, the sand and stone permeable layers are paved in the box body from bottom to top, each layer of sand and stone permeable layer is paved, the sand and stone permeable layer is paved after EICP treatment liquid is sprayed, and the sand and stone permeable layer comprises sand soaked in EICP treatment liquid; the heat exchange assembly comprises a heat exchange tube, the heat exchange tube is paved in the middle of the backfill body, an inlet and an outlet of the heat exchange tube are connected with a constant temperature circulating water tank, and temperature sensors are arranged on the inlet and the outlet of the heat exchange tube.
2. The system of claim 1, wherein the outer surface of the insulation box is coated with an outer geotextile.
3. The system of claim 1, wherein the barrier film layer is a waterproof plastic film layer and the heat preservation plate layer is a foam plate layer.
4. The system of claim 1, wherein the inner diameter of the tube is 4 cm, and a plurality of drain holes are formed in the tube.
5. The system of claim 1, wherein the drainage pump is a vacuum pump and the filter cloth is gauze.
6. The system of claim 1 wherein each of said sand permeable layers has a height of less than 200mm and said sand has a particle size of less than 1mm.
7. The system of claim 1, wherein the heat exchange tube is a U-shaped or wave-shaped tube, the heat exchange tube is a HDPE tube, the inlet and the outlet of the heat exchange tube are connected with the constant temperature circulating water tank through connecting pipes, and the heat exchange tube is wrapped with heat preservation cotton at the part outside the water insulation heat preservation box and the connecting pipes.
8. A filling process for a biomineralization cementitious backfill body buried pipe heat exchange system as set forth in any one of claims 1 to 7, comprising the steps of: (1) EICP treatment fluid configuration Mixing soybean powder and water according to a mass ratio of 1:10, adding 0.05mol of calcium chloride into each liter of solution, stirring, adding epsilon-polylysine hydrochloride into soybean powder suspension according to a mass ratio of 0.8g/kg after stirring, continuously stirring, standing at room temperature for layering, and taking supernatant fluid to obtain a soybean urease solution; mixing calcium chloride with molar concentration of 2.0 mol/L and urea according to volume ratio of 1:1 to obtain cementing liquid; Mixing the soybean urease solution and the cementing liquid according to the volume ratio of 1:1 to obtain EICP treatment liquid; (2) Sand treatment of backfill Pouring EICP treatment fluid into sand of a backfill body, fully stirring and soaking, wherein the grain diameter of the sand is smaller than 1mm; (3) Drainage assembly and heat exchange assembly laying Laying geotechnical cloth in the box body, laying a flower pipe part of a drain pipe above the geotechnical cloth in the inner bottom of the box body, wrapping filter cloth outside the flower pipe, extending the other end of the drain pipe out of the box body and connecting with a liquid discharge pump, connecting an inlet and an outlet of a heat exchange pipe with a constant temperature circulating water tank, installing temperature sensors on the inlet and the outlet of the heat exchange pipe, inserting the middle part of the heat exchange pipe into the middle of the box body, and wrapping heat preservation cotton outside the water-proof heat preservation box body by the part of the heat exchange pipe; (4) Filling of backfill bodies Filling the soaked sand in the step (2) into a box body in a layered manner, wherein each layer is a sand-stone permeable layer, the height of each sand-stone permeable layer is less than 200mm, spraying EICP treatment liquid on the surface after filling one sand-stone permeable layer, starting a liquid discharge pump to discharge liquid, filling the next sand-stone permeable layer after spraying EICP treatment liquid until filling is completed, paving geotextile on the upper surface of the backfill body, and covering and fixing a box cover.
9. The process of claim 1, wherein in step (1), after calcium chloride is added, stirring is carried out for 40: 40 min at a rotation speed of 200 rpm/min, stirring is continued for 5 minutes after epsilon-polylysine hydrochloride is added, a soybean urease solution is stood for 8 hours at room temperature for layering, calcium chloride and urea with molar concentrations of 2.0: 2.0 mol/L are stood until the temperature is consistent with the room temperature, then the calcium chloride is mixed according to a volume ratio of 1:1, a large amount of heat influence on the configuration concentration is prevented from being released by dissolving the calcium chloride in water, in step (2), after ICP cementing liquid is poured into sand of a backfill body, the backfill body is fully stirred and soaked for 1 hour, in step (3), an inlet and an outlet of a heat exchange tube are connected with a constant-temperature circulating water tank through a connecting pipe, and finally geotextile is covered outside the waterproof heat insulation tank in step (4).
10. An evaluation method for the biomineralization cementing backfill body buried pipe heat exchange system according to any one of claims 1 to 7, wherein the evaluation method is characterized in that the heat exchange amount and the energy efficiency coefficient of the buried pipe unit well depth are used for evaluation, and the heat exchange amount formula of the buried pipe unit well depth is as follows: Wherein q is heat exchange amount (W/m) of unit well depth of the buried pipe, G is fluid mass flow (kg/s) in the heat exchange pipe, C p is fluid mass specific heat capacity (J/(kg-K)) in the heat exchange pipe, t in 、t out is water temperature (DEG C) at an inlet and an outlet of the heat exchange pipe, and L is the buried depth (m) of the heat exchange pipe; The energy efficiency coefficient formula is as follows: Wherein t in 、t out is the inlet and outlet water temperature of the heat exchange tube, t ave is the average inlet and outlet water temperature of the heat exchange tube, and t 0 is the initial temperature of the backfill body; And calculating the heat exchange quantity and the energy efficiency coefficient of the unit well depth to evaluate the performance of the biomineralization cementing backfill body buried pipe heat exchange system.

Description

Heat exchange system, filling process and evaluation method for biomineralization cementing backfill body buried pipe Technical Field The invention relates to the technical field of ground source heat pump engineering and geotechnical engineering reinforcement, in particular to a biomineralization cementing backfill body buried pipe heat exchange system, a filling process and an evaluation method. Background The ground source heat pump system is a technology for supplying energy to a building by using shallow geothermal energy, and through a heat exchange tube buried in a stratum, a circulating medium (usually water) in the tube exchanges heat with surrounding rock-soil bodies, so that refrigeration in summer and heating in winter are realized. The system mainly comprises a buried pipe heat exchanger system, a ground source heat pump host system and an indoor air conditioner terminal system. The ground heat exchanger is used as a core component of the system, and the heat exchange efficiency of the ground heat exchanger and surrounding backfill materials directly influences the operation performance of the whole system. In conventional energy underground structures, backfill materials are reinforced with cement-based or bentonite-based gellants. The cement-based material has higher heat conductivity coefficient and compressive strength, but the heat conductivity is obviously influenced by the water-cement ratio, and the bentonite-based material (such as bentonite mortar) can be used as backfill, but is easy to crack and shrink under the condition of water loss, so that the heat conductivity is seriously influenced. Therefore, the development of the ground source heat pump system which is green, environment-friendly, efficient and convenient to construct has important significance for promoting the sustainable development and practical engineering application of the energy underground structure. Disclosure of Invention The invention provides a heat exchange system, a filling process and an evaluation method for a ground buried pipe of a biomineralization cementing backfill body, which solve the problems of unstable heat conduction, easiness in cracking, poor compactness and the like of a traditional ground source heat pump system which adopts cement-based and bentonite-based backfill materials. The technical scheme of the invention is as follows: The invention firstly provides a ground buried pipe heat exchange system of a biological mineralized cemented backfill body, which comprises a water insulation and heat preservation box body, a drainage assembly, a backfill body and a heat exchange assembly, wherein the water insulation and heat preservation box body comprises a box body and a box cover, the water insulation and heat preservation box body sequentially comprises an impermeable membrane layer and a heat preservation plate layer from the inner surface to the outer surface, inner geotechnical cloth is further paved on the inner surface of the heat insulation and heat preservation box body, the drainage assembly comprises a plurality of drainage pipes, one ends of the drainage pipes are positioned at the inner bottom of the water insulation and heat preservation box body, the other ends of the drainage pipes are connected with a drainage pump, the drainage pump is positioned outside the water insulation and heat preservation box body, the drainage pipes positioned at the inner bottom of the water insulation and heat preservation box body are flower pipes, filter cloth is wrapped outside the drainage pipes, the backfill body comprises a plurality of layers of sand and stone water permeable layers, each layer is paved in the box body from bottom to top, each sand water permeable layer is paved with EICP of treatment liquid, the sand water permeable layer comprises a sand heat exchange pipe soaked with EICP treatment liquid, the heat exchange pipe is paved in the middle of the backfill body, an inlet and an outlet of the heat exchange pipe are connected with the heat exchange pipe, and a temperature sensor is arranged on the inlet and outlet of the heat exchange pipe. Further, an outer geotextile is laid on the outer surface of the heat-insulating water-separating tank body. Furthermore, the seepage-proofing film layer is a waterproof plastic film layer, and the heat-insulating board layer is a foam board layer. Further, the inner diameter of the flower pipe is 4 cm, and a plurality of water draining holes are formed in the flower pipe. Further, the liquid discharge pump is a vacuum slurry pump, and the filter cloth is gauze. Further, the height of each sand-stone permeable layer is less than 200mm, and the particle size of sand is less than 1mm. Further, the part of the heat exchange tube located in the waterproof heat insulation box body is a U-shaped or wave-shaped tube, the heat exchange tube is an HDPE tube, the inlet and the outlet of the heat exchange tube are connected with the constant temperature