Graphene modified high-density polyethylene pipe for ground source heat pump system

Abstract

The invention provides a graphene modified high-density polyethylene pipe for a ground source heat pump system. A preparation method of the graphene modified high-density polyethylene pipe comprises the following steps: S1, raw material selection and pretreatment; s2, mixing and dispersing; s3, extrusion molding; and S4, post-treatment and quality control. The preparation method has the beneficial effects that through performance research on the HDPE pipe, on the premise that the strength, thickness and pressure bearing capacity of the pipe are not reduced, graphene or a modified nano material is added, the heat conductivity coefficient of the pipe is increased, and therefore the heat exchange efficiency of the pipe is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene pipes, and particularly relates to a graphene-modified high-density polyethylene pipe for a ground source heat pump system. Background Art

[0002] A ground source heat pump system is a heating and air conditioning system that uses rock and soil, groundwater, or surface water as a low-temperature heat source and consists of a water source heat pump unit, a geothermal energy exchange system, and a building interior system. Its working principle is based on heat pump technology, that is, using a heat pump to do work to make heat flow from a low-temperature medium to a high-temperature medium. In winter, the heat pump absorbs heat from the underground low-temperature heat source and elevates it to high-temperature thermal energy through a heat pump cycle to supply heating to the building interior; in summer, the heat pump discharges the heat in the building to the underground low-temperature heat source to achieve a refrigeration effect.

[0003] Currently, the high-density polyethylene (HDPE) pipes used in ground source heat pump systems have a low thermal conductivity, which is the link with the largest thermal resistance in the entire ground temperature field heat exchange system, affecting the heat exchange efficiency and increasing the application cost. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a graphene-modified high-density polyethylene pipe for a ground source heat pump system.

[0005] The specific scheme is as follows: A graphene-modified high-density polyethylene pipe for a ground source heat pump system, characterized by comprising the following steps: S1. Raw material selection and pretreatment; S2. Mixing and dispersion; S3. Extrusion molding; S4. Post-treatment and quality control.

[0006] As a further improvement of the present invention, the step S1 includes the following steps: S11. Select HDPE raw materials with a melt index MI in the range of 2 - 20 g / 10 min. Among them, for thin-walled pipes, select HDPE raw materials with a higher melt index; for thick-walled pipes, HDPE raw materials with a lower melt index can be selected; and the density of HDPE is between 0.940 - 0.965 g / cm³ to ensure that the pipes have good physical properties and chemical stability; S12. Dry the HDPE raw materials to remove moisture and volatile substances and reserve them. Among them, the drying temperature is controlled at 60 - 80 °C, and the drying time is not less than 4 hours; S13. Select graphene with a purity higher than 95% and a thermal conductivity not lower than 2000 W / mK, or select modified nanomaterials such as alumina (Al 2 O 3, aluminum nitride (AlN), etc., and they are surface-modified to improve their compatibility with HDPE; among them, the particle size of graphene or modified nanomaterials is controlled within 5 - 50 nm to ensure their uniform dispersion in HDPE; S14. Dry and remove impurities from graphene or modified nanomaterials and set them aside to avoid affecting the properties of the composite material.

[0007] As a further improvement of the present invention, the step S2 includes the following steps: S21. Use a high-speed mixer to mix the pretreated HDPE raw material with graphene or modified nanomaterials. The rotation speed of the mixer is controlled within 500 - 1500 rpm; the mixing time is not less than 15 minutes to ensure that HDPE and graphene or modified nanomaterials can be fully and evenly mixed; the mixing temperature is controlled between 160 - 180 °C to avoid overheating and degradation of the materials; S22. Use an ultrasonic disperser for dispersion. The frequency of the ultrasonic wave is controlled within 20 - 40 kHz, the power is controlled within 1000 - 3000 W, and the dispersion time is not less than 30 minutes to ensure the uniform dispersion of graphene or nanoparticles in HDPE.

[0008] As a further improvement of the present invention, in the step S22, the dispersant is selected from non-ionic surfactants or polymer compatibilizers, and the dosage of the dispersant is 1 - 5% of the mass of graphene or nanomaterials.

[0009] As a further improvement of the present invention, the step S3 includes the following steps: S31. Before feeding the uniformly mixed material into the extruder, perform preheating treatment; S32. Feed the preheated material into the extruder for extrusion; S33. The extruded pipe passes through a cooling water tank for cooling and shaping to ensure the stability of the size and shape of the pipe.

[0010] As a further improvement of the present invention, the ratio of the length to the diameter of the extruder screw is between 20 - 40, and the length of the cooling water tank is 1.50 - 2 times the length of the pipe to ensure uniform cooling of the pipe. The water temperature of the cooling water tank is controlled between 20 - 30 °C, and the water flow rate is controlled between 0.5 - 1.5 m / s to avoid deformation or distortion.

[0011] As a further improvement of the present invention, the step S4 includes the following steps: S41. Cut the shaped pipe to the required length; S42. Perform quality inspection on the cut pipe, including tests on thermal conductivity, physical properties, and appearance quality inspection; S43. Package the qualified pipes and store them in a dry, ventilated and light-proof environment to ensure their long-term storage performance.

[0012] As a further improvement of the present invention, in step S42, a thermal conductivity tester is used to test the thermal conductivity, the test temperature is controlled between 20 and 30 °C, and the test result is not lower than 98% of the expected value; a universal material testing machine is used to test the physical properties, and the test speed is controlled between 5 and 50 mm / min; the appearance quality inspection test includes surface flatness, color uniformity, no cracks, and no bubbles.

[0013] The beneficial effects of the present invention are as follows: By studying the performance of HDPE pipes, graphene or modified nano-materials are added without reducing the pipe strength, thickness, and pressure-bearing capacity, thereby improving the thermal conductivity of the pipes and effectively enhancing their heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the present invention.

[0015] Figure 2 is a detailed flow chart of step S1 of the present invention.

[0016] Figure 3 is a detailed flow chart of step S2 of the present invention.

[0017] Figure 4 is a detailed flow chart of step S3 of the present invention.

[0018] Figure 5 is a detailed flow chart of step S4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following further clarifies the present invention in conjunction with the specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Embodiment 1

[0020] As shown in the figure, this embodiment provides a graphene-modified high-density polyethylene pipe for a ground source heat pump system, including the following steps: S1. Raw material selection and pretreatment; S2. Mixing and dispersion; S3. Extrusion molding; S4. Post-treatment and quality control.

[0021] In this embodiment, step S1 includes the following steps: S11. Select HDPE raw materials with a melt index MI in the range of 2 / 10 min. Among them, for thin-walled pipes, select HDPE raw materials with a higher melt index; for thick-walled pipes, HDPE raw materials with a lower melt index can be selected; and the density of HDPE is between 0.965 g / cm³ to ensure that the pipes have good physical properties and chemical stability; S12. Dry the HDPE raw materials to remove moisture and volatile substances and set aside. Among them, the drying temperature is controlled at 60 °C and the drying time is not less than 4 hours; S13. Select graphene with a purity higher than 95% and a thermal conductivity not lower than 2000 W / mK, or select modified nanomaterials such as alumina (Al 2 O 3 ), aluminum nitride (AlN), etc. with a thermal conductivity not lower than 20 W / mK, and its surface is modified to improve its compatibility with HDPE; among them, the particle size of graphene or modified nanomaterials is controlled at 50 nm to ensure its uniform dispersion in HDPE; S14. Dry and remove impurities from graphene or modified nanomaterials and set aside to avoid affecting the performance of the composite material.

[0022] In this embodiment, the step S2 includes the following steps: S21. Use a high-speed mixer to mix the pretreated HDPE raw materials with graphene or modified nanomaterials. The rotation speed of the mixer is controlled at 500 rpm; the mixing time is not less than 15 minutes to ensure that the HDPE and graphene or modified nanomaterials can be fully and evenly mixed; the mixing temperature is controlled between 180 °C to avoid overheating and degradation of the materials; S22. Use an ultrasonic disperser for dispersion. The frequency of the ultrasonic wave is controlled at 20 kHz, the power is controlled at 3000 W, and the dispersion time is not less than 30 minutes to ensure the uniform dispersion of graphene or nanoparticles in HDPE.

[0023] In this embodiment, the dispersant in the step S22 is selected as a non-ionic surfactant or a polymer compatibilizer, and the dosage of the dispersant is 1% of the mass of graphene or nanomaterials.

[0024] In this embodiment, the step S3 includes the following steps: S31. Before feeding the uniformly mixed material into the extruder, perform preheating treatment; S32. Feed the preheated material into the extruder for extrusion; S33. The extruded pipe is cooled and shaped through a cooling water tank to ensure the stability of the size and shape of the pipe.

[0025] In this embodiment, the ratio of the length to the diameter of the extruder screw is between 40, and the length of the cooling water tank is 1.50 times the length of the pipe to ensure uniform cooling of the pipe. The water temperature in the cooling water tank is controlled at 30°C, and the water flow rate is controlled at 0.5 m / s to avoid deformation or distortion.

[0026] In this embodiment, step S4 includes the following steps: S41. Cut the shaped pipe to the required length; S42. Conduct quality inspection on the cut pipe, including tests on thermal conductivity, physical properties, and appearance quality inspection; S43. Package the qualified pipes and store them in a dry, ventilated, and light-proof environment to ensure their long-term storage performance.

[0027] In this embodiment, in step S42, a thermal conductivity tester is used to test the thermal conductivity, the test temperature is controlled between 30°C, and the test result is not lower than 98% of the expected value; a universal material testing machine is used to test the physical properties, and the test speed is controlled at 5 mm / min; the appearance quality inspection test includes surface flatness, color uniformity, no cracks, and no bubbles. Embodiment 2

[0028] This embodiment provides a graphene-modified high-density polyethylene pipe for a ground source heat pump system, including the following steps: S1. Raw material selection and pretreatment; S2. Mixing and dispersion; S3. Extrusion molding; S4. Post-treatment and quality control.

[0029] In this embodiment, step S1 includes the following steps: S11. Select HDPE raw materials with a melt index MI in the range of 20 g / 10 min. Among them, for thin-walled pipes, select HDPE raw materials with a higher melt index; for thick-walled pipes, HDPE raw materials with a lower melt index can be selected; and the density of HDPE is between 0.940 g / cm³ to ensure that the pipe has good physical properties and chemical stability; S12. Dry the HDPE raw materials to remove moisture and volatile substances and set aside. Among them, the drying temperature is controlled at 80°C, and the drying time is not less than 4 hours; S13. Select graphene with a purity higher than 95% and a thermal conductivity not lower than 2000 W / mK, or select modified nanomaterials such as alumina (Al 2 O 3, aluminum nitride (AlN), etc., and they are surface-modified to improve their compatibility with HDPE; among them, the particle size of graphene or modified nanomaterials is controlled within 5 nm to ensure their uniform dispersion in HDPE; S14. Dry and remove impurities from the graphene or modified nanomaterials and set them aside to avoid affecting the properties of the composite material.

[0030] In this embodiment, the step S2 includes the following steps: S21. Use a high-speed mixer to mix the pretreated HDPE raw material with graphene or modified nanomaterials. The rotation speed of the mixer is controlled at 1500 rpm; the mixing time is not less than 15 minutes to ensure that HDPE and graphene or modified nanomaterials can be fully and evenly mixed; the mixing temperature is controlled between 160 °C to avoid overheating and degradation of the materials; S22. Use an ultrasonic disperser for dispersion. The frequency of the ultrasonic wave is controlled at 40 kHz, the power is controlled at 1000 W, and the dispersion time is not less than 30 minutes to ensure the uniform dispersion of graphene or nanoparticles in HDPE.

[0031] In this embodiment, the dispersant selected in the step S22 is a non-ionic surfactant or a polymer compatibilizer, and the dosage of the dispersant is 5% of the mass of the graphene or nanomaterials.

[0032] In this embodiment, the step S3 includes the following steps: S31. Before feeding the uniformly mixed material into the extruder, perform a preheating treatment; S32. Feed the preheated material into the extruder for extrusion; S33. The extruded pipe passes through a cooling water tank for cooling and shaping to ensure the stability of the size and shape of the pipe.

[0033] In this embodiment, the ratio of the length to the diameter of the extruder screw is between 20, and the length of the cooling water tank is twice the length of the pipe to ensure uniform cooling of the pipe. The water temperature of the cooling water tank is controlled at 20 °C, and the water flow rate is controlled at 1.5 m / s to avoid deformation or distortion.

[0034] In this embodiment, the step S4 includes the following steps: S41. Cut the shaped pipe to the required length; S42. Conduct quality inspection on the cut pipe, including tests on thermal conductivity, physical properties, and appearance quality inspection; S43. Package the qualified pipes and store them in a dry, ventilated, and light-proof environment to ensure their long-term storage performance.

[0035] In this embodiment, in step S42, a thermal conductivity tester is used to test the thermal conductivity. The test temperature is controlled between 20°C, and the test result is not lower than 98% of the expected value. A universal material testing machine is used to test the physical properties, and the test speed is controlled at 50 mm / min. The appearance quality inspection test includes surface flatness, color uniformity, no cracks, and no bubbles. Example 3

[0036] This embodiment provides a graphene-modified high-density polyethylene pipe for a ground source heat pump system, which includes the following steps: S1. Raw material selection and pretreatment; S2. Mixing and dispersion; S3. Extrusion molding; S4. Post-treatment and quality control.

[0037] In this embodiment, step S1 includes the following steps: S11. Select HDPE raw materials with a melt index MI in the range of 10 g / 10 min. Among them, for thin-walled pipes, HDPE raw materials with a higher melt index are selected; for thick-walled pipes, HDPE raw materials with a lower melt index can be selected. And the density of HDPE is between 0.955 g / cm³ to ensure that the pipe has good physical properties and chemical stability; S12. Dry the HDPE raw materials to remove moisture and volatile substances and set aside. Among them, the drying temperature is controlled at 70°C, and the drying time is not less than 4 hours; S13. Select graphene with a purity higher than 95% and a thermal conductivity not lower than 2000 W / mK, or select modified nanomaterials such as alumina (Al 2 O 3 ), aluminum nitride (AlN), etc., with a thermal conductivity not lower than 20 W / mK, and its surface is modified to improve its compatibility with HDPE; among them, the particle size of graphene or modified nanomaterials is controlled at 20 nm to ensure its uniform dispersion in HDPE; S14. Dry and remove impurities from the graphene or modified nanomaterials and set aside to avoid affecting the performance of the composite material.

[0038] In this embodiment, step S2 includes the following steps: S21. Use a high-speed mixer to mix the pretreated HDPE raw materials with graphene or modified nanomaterials. The rotation speed of the mixer is controlled at 800 rpm; the mixing time is not less than 15 minutes to ensure that the HDPE and graphene or modified nanomaterials can be fully mixed evenly; the mixing temperature is controlled between 170°C to avoid material overheating and degradation; S22. Disperse using an ultrasonic disperser, controlling the ultrasonic frequency at 30 kHz, the power at 2000 W, and the dispersion time to be no less than 30 minutes to ensure the uniform dispersion of graphene or nanoparticles in HDPE.

[0039] In this embodiment, in step S22, the dispersant is selected from non-ionic surfactants or polymer compatibilizers, and the dosage of the dispersant is 3% of the mass of graphene or nanomaterials.

[0040] In this embodiment, step S3 includes the following steps: S31. Before feeding the uniformly mixed material into the extruder, perform preheating treatment. S32. Feed the preheated material into the extruder for extrusion. S33. The extruded pipe passes through a cooling water tank for cooling and shaping to ensure the stability of the pipe's size and shape.

[0041] In this embodiment, the ratio of the length to the diameter of the extruder screw is between 30, and the length of the cooling water tank is 1.7 times the length of the pipe to ensure uniform cooling of the pipe. The water temperature in the cooling water tank is controlled at 25°C, and the water flow rate is controlled at 1.1 m / s to avoid deformation or distortion.

[0042] In this embodiment, step S4 includes the following steps: S41. Cut the shaped pipe to the required length. S42. Conduct quality inspections on the cut pipes, including tests for thermal conductivity, physical properties, and appearance quality inspections. S43. Package the qualified pipes and store them in a dry, ventilated, and light-proof environment to ensure their long-term storage performance.

[0043] In this embodiment, in step S42, a thermal conductivity tester is used for thermal conductivity testing, the test temperature is controlled between 25°C, and the test result is not less than 98% of the expected value; a universal material testing machine is used for physical property testing, and the test speed is controlled at 20 mm / min; the appearance quality inspection test includes surface flatness, color uniformity, no cracks, and no bubbles.

[0044] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A graphene-modified high-density polyethylene pipe for a ground-source heat pump system, characterized in that: The following steps are involved: S1. Raw material selection and pretreatment; S2. Mixing and dispersion; S3, extrusion molding; S4, post-processing and quality control.

2. The graphene-modified high-density polyethylene pipe for a ground source heat pump system according to claim 1, characterized in that: The step S1 comprises the following steps: S11. Select HDPE raw materials with a melt index MI in the range of 2 to 20 g / 10 min. For thin-walled pipes, select HDPE raw materials with a higher melt index; for thick-walled pipes, select HDPE raw materials with a lower melt index; and the density of HDPE is between 0.940 and 0.965 g / cm³; S12, drying the HDPE raw material to remove moisture and volatile substances therein and prepare it for standby use, wherein the drying temperature is controlled at 60-80° C. and the drying time is not less than 4 hours; S13. Select graphene with a purity higher than 95% and a thermal conductivity of not less than 2000W / mK, or select modified nanomaterials with a thermal conductivity of not less than 20W / mK, which have undergone surface modification; the particle size of the graphene or modified nanomaterials is controlled to be 5 to 50nm; S14, drying and removing impurities from the graphene or modified nanomaterials for later use.

3. The graphene-modified high-density polyethylene pipe for a ground-source heat pump system according to claim 1, characterized in that: The step S2 comprises the following steps: S21, using a high-speed mixer to mix the pretreated HDPE raw material with graphene or modified nanomaterials, the speed of the mixer is controlled at 500-1500 rpm; the mixing time is not less than 15 minutes; the mixing temperature is controlled at 160-180° C.; S22. Use an ultrasonic disperser for dispersion, control the frequency of the ultrasonic wave at 20-40kHz, the power at 1000-3000W, and the dispersion time at least 30 minutes.

4. The graphene-modified high-density polyethylene pipe for a ground source heat pump system according to claim 3, characterized in that: In the step S22, the dispersant is selected from a nonionic surfactant or a polymer compatibilizer, and the amount of the dispersant is 1-5% of the mass of the graphene or nanomaterial.

5. The graphene-modified high-density polyethylene pipe for a ground-source heat pump system according to claim 1, characterized in that: The step S3 comprises the following steps: S31, preheating the mixed material before feeding it into the extruder; S32, sending the preheated material into an extruder for extrusion; S33. The extruded pipe is cooled and shaped in a cooling water tank to ensure the stability of the size and shape of the pipe.

6. The graphene-modified high-density polyethylene pipe for a ground-source heat pump system according to claim 5, characterized in that: The aspect ratio of the extruder screw is between 20 and 40, the length of the cooling water tank is 1.50 to 2 times the length of the pipe, the water temperature of the cooling water tank is controlled at 20 to 30° C., and the water flow rate is controlled at 0.5 to 1.5 m / s.

7. The graphene-modified high-density polyethylene pipe for a ground-source heat pump system according to claim 1, characterized in that: The step S4 comprises the following steps: S41, cutting the shaped pipe according to the required length; S42. Conduct quality inspection on the cut pipes, including tests on thermal conductivity, physical properties, and appearance quality inspection; S43. Package qualified pipes and store them in a dry, ventilated and light-proof environment.

8. The graphene-modified high-density polyethylene pipe for a ground-source heat pump system according to claim 7, characterized in that: In step S42, a thermal conductivity tester is used to test the thermal conductivity coefficient, the test temperature is controlled between 20 and 30°C, and the test result is not less than 98% of the expected value; a universal material testing machine is used to test the physical properties, and the test speed is controlled between 5 and 50 mm / min; the appearance quality inspection test includes surface flatness, color uniformity, and the absence of cracks and bubbles.

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