CN115012404B - Heat transfer enhanced prefabricated spiral energy pile and construction method thereof - Google Patents

Abstract

The invention relates to the technical field of buried pipes of novel ground source heat pump systems, in particular to a heat transfer enhanced prefabricated spiral energy pile and a construction method thereof. The heat transfer enhancement type prefabricated spiral energy pile comprises a pile cap, a pile body, spiral blades, pile shoes and heat exchange pipes in the pile body; the pile cap and the pile shoe are respectively welded with two ends of the pile body and are centered, wherein a groove is reserved in the center of the top surface of the pile cap, and a block is arranged in the groove; two holes are reserved on two sides of the groove for the heat exchange tube to pass through; the pile shoe is a conical shoe body, and raised threads are distributed on the surface of the shoe body; the pile body is a precast reinforced concrete pile, the spiral blades and the embedded bars at the pile side are welded together and cling to the surface of the pile side; filling materials are filled between the helical blades and the pile body; the helical blade is formed by welding a plurality of helical sections along the length direction of the pile; the spiral section of heat exchange tube is bound outside the steel reinforcement cage, and the outlet section is bound inside the steel reinforcement cage.

Description

A heat transfer enhanced prefabricated spiral energy pile and construction method thereof

Technical Field

The present invention relates to the technical field of buried pipes of a novel ground source heat pump system, and in particular to the technical field of ground source heat pumps suitable for building heating and cooling, and in particular to a heat transfer enhanced prefabricated spiral energy pile and a construction method thereof.

Background Art

The ground source heat pump system mainly includes a ground pipe heat exchanger and a heat pump system, which is a common method for exploiting shallow geothermal energy contained in the soil. The ground pipe heat exchanger is a geothermal energy extraction device formed by drilling holes in the soil, setting heat exchange pipes in the holes, and backfilling the holes. It uses the temperature difference between the soil and the atmosphere to achieve energy exchange between the soil and the atmosphere in winter and summer. However, the high drilling cost and large land use space of the ground pipe heat exchanger will limit the promotion and application of ground source heat pump technology.

The Chinese utility model patent No. 201620263236.9, entitled "Hot Cone Spiral Energy Pile Heat Exchange Tube", discloses a hollow cone spiral energy pile heat exchange tube, which consists of three parts: an inlet pipe section, a spiral pipe section and an outlet pipe section connected in sequence. The heat exchange tubes are arranged in a tapered manner and the spiral tubes are staggered, which can reduce the intensity of thermal interference and increase the heat transfer capacity. The Chinese utility model patent No. 200810159583.7, entitled "Pile-buried spiral tube ground source heat pump system and heat transfer model of its geothermal heat exchanger", discloses a pile-buried spiral tube ground source heat pump system and heat transfer model of its geothermal heat exchanger, which includes a geothermal heat exchanger, which is connected to an air conditioning heat pump system through a pipeline, and the air conditioning heat pump system is connected to a delivery and terminal system to a building, and there are multiple geothermal heat exchangers, each of which is composed of a building pile foundation and a spiral tube buried in the pile foundation to form a pile-buried spiral tube geothermal heat exchanger. By proposing a solid cylindrical heat source model, two analytical solutions of the heat transfer model were obtained using the Green's function method. By establishing a heat transfer model, various parameters of the pile-buried spiral tube geothermal heat exchanger and their effects on the heat transfer capacity were analyzed.

The heat exchange efficiency of a heat exchanger is proportional to the size of the heat exchange surface (i.e., the contact surface between the heat exchanger and the surrounding environment). However, in the prior art, most energy piles adopt a cylindrical geometric structure, which results in a limited heat exchange surface between the energy pile and the surrounding soil, thereby limiting the heat exchange efficiency of the energy pile. Therefore, it is necessary to propose a new type of energy pile that can effectively increase the heat exchange surface between the energy pile and the soil, thereby greatly improving the heat exchange efficiency of the energy pile.

Summary of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings and defects, and solve the problem of low heat exchange efficiency caused by the small contact area between the traditional energy pile and the soil; the present invention proposes a heat transfer enhanced prefabricated spiral energy pile and its construction method. The spiral energy pile is formed by welding the spiral blades and the pile body with steel bars, and the spiral blades are distributed on the surface of the spiral pile body, so that the contact area between the pile body and the surrounding soil is increased, and a solution with good bearing performance and high heat exchange efficiency is achieved.

The technical solutions adopted to achieve the purpose of the present invention are as follows:

A heat transfer enhanced prefabricated spiral energy pile, comprising a pile cap, a pile body, spiral blades, a pile shoe and a heat exchange tube in the pile body; the pile cap and the pile shoe are respectively welded to the two ends of the pile body, and the three are aligned, wherein a groove is reserved at the center of the top surface of the pile cap, and a block is arranged in the groove; two holes are reserved on both sides of the groove for the heat exchange tube to pass through, and the diameter of the pile cap is the same as the diameter of the pile body; the pile shoe is a conical shoe body, the surface of the shoe body is provided with raised threads, and the maximum diameter of the shoe body is the same as the diameter of the pile body.

The pile body is a prefabricated reinforced concrete pile. During prefabrication, embedded steel bars are arranged on the side surface of the pile, welded to the pile body steel cage and extending out of the side surface of the pile; the embedded steel bars are arranged on the path of the spiral blades.

The spiral blade is welded to the pre-buried steel bar on the pile side and is close to the pile side surface; a filler is filled between the spiral blade and the pile body; and the spiral blade is welded from a plurality of spiral segments along the length direction of the pile.

The heat exchange tube consists of an inlet section, a spiral section and an outlet section. The spiral section is spiral in shape, and the inlet section and the outlet section are straight tubes. The spiral section is tied to the outside of the steel cage, and the outlet section is tied to the inside of the steel cage. The ends of the inlet section and the outlet section pass through the reserved holes of the pile cap.

Furthermore, the pile cap, block and spiral blade are made of steel.

Furthermore, the filler at the contact surface between the pile body and the spiral blade is made of concrete with good heat conductivity or silicone grease with high thermal conductivity.

Furthermore, the contact surfaces of the block and the pile cap are bonded by PVC glue or HY-106AB glue.

Furthermore, the length of the block is 400 mm to 800 mm, and the length of the embedded pile cap is 200 mm to 400 mm.

Furthermore, the pile cap has a thickness of 1000 mm to 1500 mm.

Furthermore, the diameter of the reserved hole is not less than the diameter of the heat exchange tube.

Furthermore, the spiral blade has a spiral section of 0° to 360°, is welded from several spiral sections along the length of the pile, has a thickness of 30mm to 40mm, a pitch of 200mm to 400mm, and a width not less than 0.1 times the diameter of the pile body.

Furthermore, the heat exchange tube is made of HDPE heat exchange tube with high thermal conductivity and good isothermal property.

Furthermore, the outer diameter of the heat exchange tube is 19 mm to 38 mm, the wall thickness is 2 mm to 2.5 mm, and the pitch of the spiral section is 300 mm to 500 mm.

The above-mentioned construction method of the heat transfer enhanced prefabricated spiral energy pile comprises the following steps:

1) Investigate and analyze the geological conditions of the slope, conduct engineering geological exploration and design, analyze the stability of buildings around the site, and determine the design depth and pile diameter;

2) Proper leveling and compaction shall be performed in the entire area within the construction scope or on the pile foundation entry and exit site and movement route;

3) According to the geological exploration data provided by the design department and different geological conditions, select appropriate mud density, mud viscosity and different drilling speeds;

4) Pre-fabricate the spiral energy pile according to the design plan:

4-1) Make a steel cage according to the designed depth and pile diameter, weld the steel cage and embedded steel bars, tie the spiral section of the heat exchange tube to the outside of the steel cage, and tie the outlet section to the inside of the steel cage;

4-2) Make a pile body template with reserved holes, place the steel cage in the middle and then splice the pile body;

4-3) Pour concrete inside the assembled pile formwork;

4-4) Connecting the top of the pile body and the pile cap with the groove by welding, and embedding the block in the groove of the pile cap;

4-5) The outer wall of the pile body is connected to the embedded steel bars and the spiral blades by welding, and the gaps are filled with fillers;

4-6) Connect the bottom of the pile body and the top of the pile shoe by welding;

5) Lay the track according to the construction requirements, select the location to set up the pile driver and equipment, connect the water and power supply to test the machine, and move the pile driver to the pile position;

6) Connecting with a pile driver capable of performing spinning through the block at the center of the pile cap;

7) Drill to the designed depth according to the scheme designed in step 1);

Furthermore, the drilling depth is 10m to 20m, and the pile diameter is 600mm to 1000mm.

Beneficial effects of the present invention:

Compared with traditional energy piles, the present invention has the following technical advantages:

(1) Combining the pile foundation with the buried pipe of the ground source heat pump can play the dual role of extracting shallow underground geothermal heat and bearing the building load. At the same time, it can avoid the high drilling cost and large space occupied by the buried pipe heat exchanger, and has good economic benefits.

(2) The traditional energy pile is replaced by a spiral energy pile with spiral blades. The spiral energy pile can be screwed into the surrounding soil. The spiral blades increase the contact area between the pile body and the surrounding soil, thereby increasing the heat exchange rate between the heat exchange liquid and the surrounding soil, improving the heat exchange rate, and better realizing the sustainable use of energy.

(3) During the prefabrication process, fillers are used to fill the gap between the spiral blade and the pile body, which can not only connect the spiral blade and the pile body into one, but also reduce the heat loss during the transfer process. By arranging fillers between the pile cap and the block, the block is firmly placed on the pile cap, avoiding the displacement caused by the drilling of the spiral pile during the construction process, resulting in the separation of the pile driver and the spiral pile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a heat transfer enhanced prefabricated spiral energy pile of the present invention;

FIG2 is a schematic diagram of the pile shoe of FIG1 ;

FIG3 is a plan view of the pile cap of FIG1 ;

Fig. 4 is an enlarged schematic diagram of the A-A section of Fig. 1;

FIG5 is a schematic diagram of a heat exchange tube of the present invention;

FIG6( a ) is a schematic diagram of a spiral blade of the present invention;

Fig. 6(b) is a schematic diagram of the embedded steel bars of the present invention;

FIG. 6( c ) is a schematic diagram of a single screw pile segment of the present invention.

In the figure: 1 block, 2 pile cap, 3 spiral blades, 4 filler, 5 pile body, 6 heat exchange tube, 7 pile shoe, 8 embedded steel bars.

DETAILED DESCRIPTION

The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

As shown in FIG. 1 and FIG. 4 , a heat transfer enhanced prefabricated spiral energy pile of the present invention comprises a pile cap 2 , a pile body 5 , spiral blades 3 , a heat exchange tube 6 in the pile body, and a pile shoe 7 .

As shown in FIG3 , the pile cap 2 is made of steel and is strictly aligned with the original pile. A square groove is reserved in the center of the pile cap 2, in which a block 1 is arranged, and circular holes are reserved on both sides. The pile cap 2 is welded to the pile body 5 .

The pile body 5 is a prefabricated reinforced concrete pile, and during prefabrication, embedded steel bars 8 are arranged on the pile side surface, welded together with the pile body steel cage and extending out of the pile side surface. The embedded steel bars 8 are arranged in the path of the spiral blades 3 .

As shown in Fig. 6(a) to Fig. 6(c), the spiral blade 3 is made of steel and welded to the pre-embedded steel bar 8 on the pile side, close to the pile side surface. The spiral blade 3 is welded from a plurality of spiral segments along the length of the pile.

As shown in FIG. 5 , the heat exchange tube 6 is composed of an inlet section, a spiral section and an outlet section. The spiral section is in a spiral shape, and the inlet section and the outlet section are straight tubes.

As shown in FIG. 2 , the pile shoe 7 is a conical shoe body with raised threads on the surface of the shoe body. The maximum diameter of the shoe body is the same as the diameter of the pile body 5 . The pile body 5 and the pile shoe 7 are connected by welding.

The square steel block is strictly aligned with the pile cap, and the square steel block is embedded in the groove of the pile cap, and the contact surfaces of the two are bonded by PVC glue or HY-106AB glue.

The block 1 is a square steel block with a length of 400 mm to 800 mm, and the length of the embedded pile cap 2 is 200 mm to 400 mm.

The pile cap 2 and the pile body 5 are strictly aligned.

The pile cap 2 has a diameter of 1d, where d is the diameter of the pile body 5, and a thickness of 1000 mm to 1500 mm.

The diameter of the reserved hole is not less than the diameter of the heat exchange tube.

The spiral blade 3 is made of steel material with good thermal conductivity, with 0°～360° as a spiral segment, and several spiral segments are welded along the length of the pile, with a thickness of 30mm～40mm, a pitch of 200mm～400mm, and a width not less than 0.1 times the diameter.

The heat exchange tube 6 is made of HDPE heat exchange tube with high thermal conductivity and good isothermal property. The spiral section is tied to the outside of the steel cage, and the outlet section is tied to the inside of the steel cage and passes through the reserved hole of the pile cap.

The heat exchange tube 6 has an outer diameter of 19 mm to 38 mm, a wall thickness of 2 mm to 2.5 mm, and a helical pitch of 300 mm to 500 mm.

Compared with traditional energy piles, the heat transfer enhanced prefabricated spiral energy pile increases the heat exchange area by arranging spiral blades, thereby enhancing the heat exchange between the pile and the soil. The enhanced heat exchange will produce additional thermal strain, resulting in an increase in the displacement and settlement of the energy pile. The burial of the spiral blades in the soil also effectively increases the contact area. By increasing the contact area, the displacement and settlement caused by heat exchange can be effectively reduced.

Embodiment 1:

A construction method for a heat transfer enhanced prefabricated spiral energy pile comprises the following steps:

1) Investigate and analyze the geological conditions of the slope, conduct engineering geological exploration and design, analyze the stability of the buildings around the site, and determine the designed drilling depth and drilling diameter. In this embodiment, the pile body 5 has a diameter of 600mm and a designed depth of 12m.

2) Proper leveling and compaction shall be carried out in the entire area within the construction scope or on the pile foundation entry and exit site and movement route.

3) According to the geological exploration data provided by the design department and different geological conditions, appropriate mud density, mud viscosity and different drilling speeds are selected. In this embodiment, the mud density is 1.1, the viscosity is 18 Pa.s, and the drilling speed is 1.4 m/min.

4) Pre-fabricate the spiral energy pile according to the design plan:

4-1) A steel cage is made according to the designed depth and the diameter of the pile body 5, and the steel cage and the embedded steel bars 8 are welded. The spiral section of the heat exchange tube 6 is tied to the outside of the steel cage, and the outlet section is tied to the inside of the steel cage. The HDPE heat exchange tube 6 is arranged inside the pile body 5 of the spiral energy pile, and the outer diameter of the heat exchange tube 6 is 25mm, the wall thickness of the heat exchange tube 6 is 2.3mm, and the distance between the heat exchange tubes 6 is 200mm.

4-2) Make a template with reserved holes, place the steel cage in the middle and then splice the template.

4-3) Pour concrete into the assembled formwork.

4-4) Connect the top of the pile body 5 and the pile cap 2 with a square groove by welding, and embed the block 1 in the groove of the pile cap 2. The size of the block 1 is 400 mm. The diameter of the pile cap 2 is 600 mm. The block 1 is embedded in the pile cap 200 mm;

4-5) The outer wall of the pile body 5 is connected to the spiral blade 3 by welding the embedded steel bars 8. The embedded steel bars extend 200 mm from the concrete surface of the pile side;

4-6) Connecting the bottom of the pile body 5 and the top of the pile shoe 7 by welding;

5) Lay the track according to the construction requirements, select the location to set up the pile driver and equipment, connect the water and power supply for testing, and move the pile driver to the pile position.

6) The block 1 at the center of the pile cap 2 is connected to a connector with a square groove and a pile driver capable of performing spinning.

7) Drill to the designed depth according to the plan designed in step 1).

Example 2

A construction method for a heat transfer enhanced prefabricated spiral energy pile comprises the following steps:

1) Investigate and analyze the geological conditions of the slope, conduct engineering geological exploration and design, analyze the stability of the buildings around the site, and determine the designed drilling depth and drilling diameter. In this embodiment, the pile body 5 has a diameter of 800mm and a designed depth of 14m.

2) Proper leveling and compaction shall be carried out in the entire area within the construction scope or on the pile foundation entry and exit site and movement route.

3) According to the geological exploration data provided by the design department, according to different geological conditions, select appropriate mud density, mud viscosity and different drilling speeds. In this embodiment, the mud density is 1.2, the viscosity is 17Pa.s, and the drilling speed is 1.2m/min.

4) Pre-fabricate the spiral energy pile according to the design plan:

4-1) A steel cage is made according to the designed depth and the diameter of the pile body 5, and the steel cage and the embedded steel bars 8 are welded. The spiral section of the heat exchange tube 6 is tied to the outside of the steel cage, and the outlet section is tied to the inside of the steel cage. The HDPE heat exchange tube 6 is arranged inside the pile body 5 of the spiral energy pile, and the outer diameter of the heat exchange tube 6 is 25mm, the wall thickness of the heat exchange tube 6 is 2.5mm, and the distance between the heat exchange tubes 6 is 300mm.

4-2) Make a template with reserved holes, place the steel cage in the middle and then splice the template.

4-3) Pour concrete into the assembled formwork.

4-4) Connect the top of the pile body 5 and the pile cap 2 with a square groove by welding, and embed the block 1 in the groove of the pile cap 2. The size of the block 1 is 600 mm. The diameter of the pile cap 2 is 800 mm. The block 1 is embedded in the pile cap 300 mm;

4-5) The outer wall of the pile body 5 is connected to the spiral blade 3 by welding the embedded steel bars 8. The embedded steel bars extend 300 mm from the concrete surface of the pile side;

4-6) Connecting the bottom of the pile body 5 and the top of the pile shoe 7 by welding;

5) Lay the track according to the construction requirements, select the location to set up the pile driver and equipment, connect the water and power supply for testing, and move the pile driver to the pile position.

6) The square steel block in the center of the pile cap is connected to a connector with a square groove and a pile driver capable of spinning.

7) Drill to the designed depth according to the plan designed in step 1).

Claims (4)

1. A heat transfer enhanced prefabricated spiral energy pile, characterized in that the heat transfer enhanced prefabricated spiral energy pile comprises a pile cap, a pile body, spiral blades, a pile shoe and a heat exchange tube in the pile body; the pile cap and the pile shoe are respectively welded to the two ends of the pile body, and the three are aligned, wherein a groove is reserved at the center of the top surface of the pile cap, and a block is arranged in the groove; two holes are reserved on both sides of the groove for the heat exchange tube to pass through, and the diameter of the pile cap is the same as the diameter of the pile body; the pile shoe is a conical shoe body, and the surface of the shoe body is provided with raised threads, and the maximum diameter of the shoe body is the same as the diameter of the pile body; The pile body is a prefabricated reinforced concrete pile. During prefabrication, embedded steel bars are arranged on the side surface of the pile, welded together with the pile body steel cage and extending out of the side surface of the pile; the embedded steel bars are arranged on the path of the spiral blades; The spiral blade is welded to the pre-buried steel bar on the pile side and is close to the pile side surface; a filler is filled between the spiral blade and the pile body; the spiral blade is welded by a plurality of spiral segments along the length direction of the pile; The heat exchange tube consists of an inlet section, a spiral section and an outlet section. The spiral section is spiral-shaped, and the inlet section and the outlet section are straight tubes. The spiral section is tied to the outside of the steel cage, and the outlet section is tied to the inside of the steel cage. The ends of the inlet section and the outlet section pass through the reserved holes of the pile cap. The pile cap, block and spiral blade are made of steel; the heat exchange tube is made of HDPE heat exchange tube; The filler at the contact surface between the pile body and the spiral blade is silicone grease; the contact surface between the block and the pile cap is bonded by PVC glue or HY-106AB glue; The spiral blades are welded together along the length of the pile, with 0° to 360° as one spiral section, and have a thickness of 30mm to 40mm, a pitch of 200mm to 400mm, and a width not less than 0.1 times the diameter of the pile body; the outer diameter of the heat exchange tube is 19mm to 38mm, the wall thickness is 2mm to 2.5mm, and the spiral section pitch is 300mm to 500mm. 2. According to claim 1, a heat transfer enhanced prefabricated spiral energy pile is characterized in that the length of the block is 400mm to 800mm, the length of the embedded pile cap is 200mm to 400mm; the thickness of the pile cap is 1000mm to 1500mm; the diameter of the reserved hole is not less than the diameter of the heat exchange tube. 3. The construction method of a heat transfer enhanced prefabricated spiral energy pile according to claim 1 or 2, characterized in that it comprises the following steps: 1) Investigate and analyze the geological conditions of the slope, conduct engineering geological exploration and design, analyze the stability of buildings around the site, and determine the design depth and pile diameter; 2) Level and compact the entire area within the construction scope or the pile foundation entry and exit site and movement route; 3) According to the geological exploration data provided by the design department and different geological conditions, select mud density, mud viscosity and different drilling speeds; 4) Pre-fabricate the spiral energy pile according to the design plan: 4-1) Make a steel cage according to the designed depth and pile diameter, weld the steel cage and embedded steel bars, tie the spiral section of the heat exchange tube to the outside of the steel cage, and tie the outlet section to the inside of the steel cage; 4-2) Make a pile body template with reserved holes, place the steel cage in the middle and then splice the pile body template; 4-3) Pour concrete inside the assembled pile formwork; 4-4) Connect the top of the pile body and the pile cap with a groove by welding, and embed the block in the groove of the pile cap; 4-5) The outer wall of the pile body is connected to the embedded steel bars and spiral blades by welding, and the gaps are filled with fillers; 4-6) Connect the bottom of the pile body and the top of the pile shoe by welding; 5) Lay the track according to the construction requirements, select the location to set up the pile driver and equipment, connect the water and power supply to test the machine, and move the pile driver to the pile position; 6) Connecting with a pile driver capable of spinning through the block at the center of the pile cap; 7) Drill to the designed depth according to the plan designed in step 1). 4. The construction method of a heat transfer enhanced prefabricated spiral energy pile according to claim 3 is characterized in that the drilling depth is 10m to 20m and the pile body diameter is 600mm to 1000mm.