A method for preventing secondary icing of heat pipes of air energy heat pumps

Abstract

The present invention provides a method for preventing secondary freezing of an air-energy heat pump heat pipe, comprising a gravity heat pipe arranged on the lower side of a main frame support of an air-energy heat pump group; the gravity heat pipe comprises a heat pipe condensation section, a heat pipe insulation section and a heat pipe evaporation section from top to bottom; the heat pipe condensation section is arranged above the ground surface; the heat pipe insulation section is arranged in a frozen soil layer; the heat pipe evaporation section is arranged in a constant temperature soil layer, an annular fin is arranged on the heat pipe condensation section, a drainage cushion layer is arranged above the ground surface, a heat storage hydrophobic sand and gravel layer is arranged above the drainage cushion layer, the lower section of the heat pipe condensation section is located in the heat storage hydrophobic sand and gravel layer, and the upper section of the heat pipe condensation section is located in the bottom space on the lower side of the main frame support of the air-energy heat pump group. The present invention has the characteristics of reasonable design and zero energy consumption in solving the problem of secondary freezing of condensed water in the bottom space of an air-energy heat pump.

Description

Technical Field

[0001] The invention relates to a method for preventing secondary icing of an air energy heat pump heat pipe, and relates to the technical field of heating, ventilation and air conditioning heat pumps. Background Art

[0002] During the heating process in the cold northern regions, air-energy heat pumps are affected by temperature and air humidity, and are in the melting and defrosting process for about 10%-15% of the time. After defrosting, a large amount of condensed water will drip to the bottom of the host under the influence of gravity. Under the influence of low temperature, it has not had time to flow away, and will condense into ice crystals or ice crystal waterfalls at the bottom of the host for the second time, and will continue to accumulate, directly forming a thick ice layer at the bottom of the cluster, which will affect the heating operation of the host in severe cases. The air-energy heat pump heating cluster formed by the centralized installation of multiple hosts is affected by the "cold island effect", especially in extreme weather such as rainy and snowy weather and freezing rain in the cold northern regions. The defrosting is more frequent and the water accumulation is worse, and the freezing at the bottom of the air-energy heat pump is even worse. In actual engineering applications, the secondary freezing of the condensed water at the bottom of the cluster is more serious. At present, the common practice in the industry is to add electric heating cables to prevent secondary freezing at the bottom of the heat pump (there are safety hazards and power consumption problems), and more artificial physical methods are used to remove ice according to the freezing situation to ensure the safe and stable operation of the air-energy heat pump host, which also wastes a lot of manpower and financial resources. The problem of ice formation in the bottom space of the main unit seriously affects the stable heating operation of air-energy heat pumps in the north. It is a problem that the air-energy heat pump industry must face and solve. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preventing secondary freezing of air energy heat pump heat pipes by providing a method with reasonable design and zero energy consumption to solve the freezing problem at the bottom of air energy heat pumps.

[0004] In order to achieve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for preventing secondary icing of an air energy heat pump heat pipe comprises the following steps:

[0006] S1: Site measurement, layout and positioning; determine the orientation and spacing according to the X and Y axis lines of the general design drawing based on the site conditions, and position on site by wedging positioning piles;

[0007] S2: Hole-making process: Use hydraulic down-the-hole hammer drill to drill holes, and use high-pressure air as drilling power and slag removal means;

[0008] S3: Gravity heat pipe assembly: Use a vacuum unit to evacuate the inside of the welded and sealed gravity heat pipe shell, then fill it with an appropriate amount of working liquid, and then perform cold welding and ultrasonic welding to seal it;

[0009] S4: Gravity heat pipe installation: vertically install the assembled gravity heat pipe into the drilled hole in step S2;

[0010] S5: filling with fine sand: filling fine sand between the bare pipe and the drilled hole gap of the evaporation section of the gravity heat pipe to form a fine sand filling layer;

[0011] S6: Drainage cushion pouring: pour the drainage cushion with cement on the ground surface. The drainage cushion is mainly used to facilitate the condensed water to flow from high to low to the ground surface and into the drainage ditch;

[0012] S7: Laying of heat storage hydrophobic gravel layer: Laying of heat storage hydrophobic gravel layer on the drainage cushion layer, wherein the heat storage hydrophobic gravel layer is mainly a mixture of coarse and fine gravel.

[0013] Furthermore, the gravity heat pipe comprises, from top to bottom, a heat pipe condensation section, a heat pipe insulation section and a heat pipe evaporation section; the heat pipe condensation section is arranged above the ground surface; the heat pipe insulation section is arranged in the frozen soil layer; and the heat pipe evaporation section is arranged in the constant temperature soil layer.

[0014] Furthermore, an annular fin is provided on the condensing section of the heat pipe.

[0015] Furthermore, an air energy heat pump group main unit bracket is arranged above the heat pipe condensation section, the lower section of the heat pipe condensation section is located in the heat storage hydrophobic gravel layer, and the upper section of the heat pipe condensation section is located in the bottom space on the lower side of the air energy heat pump group main unit bracket.

[0016] Furthermore, the length of the heat pipe condensation section is less than 60 cm.

[0017] Furthermore, the length of the upper section of the heat pipe condensation section accounts for 20-40% of the length of the heat pipe condensation section.

[0018] Furthermore, the heat pipe insulation section passes through the frozen soil layer and extends downward for more than 0.5 m.

[0019] Furthermore, the thermal storage hydrophobic gravel layer mainly adopts a mixture of coarse and fine gravel, with a mass ratio of 40% pebbles and 60% fine sand.

[0020] The beneficial effects of adopting the above technical solution are:

[0021] The soil temperature below the frozen soil layer is generally above 10°C and stable. The present invention uses several gravity heat pipes buried at the bottom of the main engine to absorb heat from the "high temperature" soil below the frozen soil layer, and then releases heat from the heat pipe condensation section at the bottom of the air-energy heat pump group, maintaining part of the temperature and the space at the bottom of the main engine at a temperature field state above 0°C, so that the water flowing down from the air-energy heat pump main engine during the defrosting process always remains in liquid form and flows away. Several gravity heat pipes are installed in the bottom area of ​​the air-energy heat pump main engine, and a gravity heat pipe array is arranged at the bottom of the heat pump group. The heat pipe evaporation section is buried within 10 meters below the local maximum frozen soil layer, and the heat pump condensation section is located at the bottom of the heat pump group main engine and the bracket and is exposed to the ground. The heat pipe condensation section is a structure with annular fins as heat exchange fins to enhance heat exchange. 70% of the total length of the heat pipe condensation section exposed above the ground is buried in a heat storage hydrophobic layer composed of pebbles (coarse) stones + fine sand. The heat storage hydrophobic layer covers the evaporation section of the heat pipe and is composed of 40% pebbles (coarse) stones and 60% fine sand by mass. 30% of the total length of the heat pipe condensation section is exposed to the upper space of the heat storage hydrophobic gravel layer 3. 70% of the total length of the heat pipe condensation section is buried in the heat storage hydrophobic layer composed of sand and gravel. The cobblestone (coarse) stone structure creates water gaps, which is conducive to the flow, penetration and enhanced heat exchange effect of defrosting condensed water; 60% of the fine sand in the heat storage hydrophobic layer fills the cobblestone (coarse) stone gaps, which is conducive to the heat conduction of heat pipe condensation. The heat pipe evaporation section has annular heat exchange fins, which are covered by the heat storage hydrophobic layer for about 70% of the condensation section length. The released heat is stored by the sand and stone layer of the heat storage hydrophobic layer and maintained above 0℃, so as to ensure that the condensed water of the heat pump defrost is maintained in liquid state above 0℃ and flows away. The more defrosting water in the heat pump, the greater the temperature difference between the condensation section and the evaporation section of the heat pipe, and the better the heat exchange efficiency of the heat pipe. Even in extreme cases of freezing rain, the microenvironment state of the bottom space of the heat pump can still be maintained above 0℃. The condensing section of the heat pipe is in the form of a heat exchange fin structure to enhance the condensation heat exchange effect. The evaporation section is a light pipe, which is convenient for construction and burial in the soil, and fine sand with a high thermal conductivity is filled between the light pipe and the soil pores and cracks in the evaporation section to ensure the evaporation heat absorption effect of the gravity heat pipe. 20-40% of the total length of the heat pipe evaporation section is exposed to the heat storage hydrophobic layer, and the heat pipe condensation section can be used for direct heat exchange to prevent a small amount of ice waterfalls from occurring under extreme conditions. At the same time, supercooled water is preheated and infiltrated into the sand and gravel of the heat storage hydrophobic layer for further insulation and heat absorption to prevent the defrosting condensed water of the air-to-energy heat pump from freezing again at the bottom of the base. The heat storage technology does not consume any additional energy and can maintain a microenvironment above 0°C at the bottom space of the air-to-energy heat pump base. The heat pipe is used to take "heat" from the soil, which is an active way of melting ice to prevent secondary freezing. The phenomenon of secondary freezing of condensed water in the bottom space of the air-to-energy heat pump is eliminated from the source, solving the technical problem of partial freezing of the air-to-energy heat pump affecting heating operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the present invention;

[0023] Figure 2 It is a schematic diagram of the side cross-sectional structure of the present invention;

[0024] Among them, 1. gravity heat pipe, 101. heat pipe condensation section, 102. heat pipe evaporation section, 103. heat pipe insulation section, 2. constant temperature soil layer, 201. frozen soil layer, 202. drainage cushion layer, 203. ground surface, 3. heat storage and hydrophobic gravel layer, 4. main unit bracket of air energy heat pump group, 401. bottom space, 5. fine sand filling layer. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] As attached Figure 1-2 As shown, this embodiment provides a method for preventing secondary icing of an air energy heat pump heat pipe, which is characterized in that it includes the following steps:

[0027] S1: Site measurement, layout and positioning; determine the orientation and spacing according to the X and Y axis lines of the general design drawing based on the site conditions, and position on site by wedging positioning piles;

[0028] S2: Hole-making process: Use hydraulic down-the-hole hammer drill to drill holes, and use high-pressure air as drilling power and slag removal means;

[0029] S3: Gravity heat pipe assembly: Use a vacuum unit to evacuate the inside of the welded and sealed gravity heat pipe shell, then fill it with an appropriate amount of working liquid, and then perform cold welding and ultrasonic welding to seal it;

[0030] S4: Gravity heat pipe installation: vertically install the assembled gravity heat pipe into the drilled hole in step S2;

[0031] S5: filling with fine sand: filling fine sand between the bare pipe and the drilled hole gap of the evaporation section of the gravity heat pipe to form a fine sand filling layer;

[0032] S6: Drainage cushion pouring: pour the drainage cushion with cement on the ground surface. The drainage cushion is mainly used to facilitate the condensed water to flow from high to low to the ground surface and into the drainage ditch;

[0033] S7: Laying of heat storage hydrophobic gravel layer: Laying of heat storage hydrophobic gravel layer on the drainage cushion layer, wherein the heat storage hydrophobic gravel layer is mainly a mixture of coarse and fine gravel.

[0034] In the S2 hole-forming process, a hydraulic down-the-hole hammer drill is used to drill holes, and the down-the-hole hammer casing and pipe drilling construction technology is applied. The following points should be paid attention to: when drilling in loose or broken strata, it is advisable to use small drilling pressure and large air volume as the main method, and at the same time, the casing follows the specification parameters of the wall protection, and mud is poured into the well for wall protection while drilling; when drilling in hard soil and rock formations, impact and rotary composite drilling is adopted, and high-frequency vibration down-the-hole hammer is used to break the rock; when encountering large hard rocks that are difficult to drill with pipes during the drilling process, the down-the-hole hammer should be lowered into the casing, and an eccentric hammer should be used. The specification parameters of low speed and high drilling pressure should be adopted as the main method to crush or drill through the rocks before drilling with pipes; when the hole collapses and cannot be drilled during the drilling process, it is necessary to release Slow down the drilling speed and repeat the impact static pressure and pipe drilling. If the drill pipe shakes violently or lags periodically during drilling, it means that a broken zone or a large crack has been encountered. The drill tool should be lifted immediately and then slowly lowered to pass through the area with a lower drilling pressure to prevent accidents such as drill pipe breakage. When the drilling is completed, the hole depth and inclination should be checked. After meeting the requirements, the hole should be blown with high-pressure air. After cleaning the dust in the hole, the gravity heat pipe 1 should be installed as soon as possible. Strict inspection should be carried out. Only after passing the inspection can it be filled with fine sand, and the casing should be pulled out while the sand is added. Before pulling out the pipe, first level the hole mouth so that the rock surface at the hole mouth is perpendicular to the axis of the casing, and then set up a simple scaffold to fix the pipe pulling machine. The center line of the pipe pulling machine should coincide with the axis of the casing.

[0035] An air energy heat pump group mainframe support 4 is arranged on the upper side of the gravity heat pipe 1, and a bottom space 401 is formed between the air energy heat pump group mainframe support 4 and the heat storage hydrophobic gravel layer 3. The gravity heat pipe 1 is composed of a heat pipe condensation section 101, a heat pipe insulation section 103 and a heat pipe evaporation section 102 from top to bottom; an annular fin is arranged on the heat pipe condensation section 101, and the heat pipe is a carbon steel gravity heat pipe with a corrosion-resistant coating on the surface, and the outer diameter is usually 25mm / 32mm. The gravity heat pipe 1 is filled with a low boiling point working medium, and the internal vacuum It is a typical integral gravity heat pipe with a capillary wick. It is a high-efficiency heat transfer element. The gravity heat pipe 1 evacuates the interior and fills it with a certain amount of working liquid. The liquid circulates repeatedly in the internal phase change process of evaporation-condensation, and continuously transfers the heat of the evaporation section to the condensation section, thereby completing the heat transfer process of transporting heat. The gravity heat pipe 1 applies the principle of relying on gravity to make the condensate flow back to the evaporation section: the working medium is filled into the tube shell that is evacuated to a high vacuum, and then it is sealed. One end is the evaporation section, and the other end is the cooling section. When one end is heated, the liquid working medium absorbs heat and vaporizes into steam, and the steam flows to the other end, where it is cooled to release latent heat of vaporization and condense into liquid. Under the action of gravity (or capillary force along the porous material), the liquid flows back to the evaporation end and vaporizes again, and this cycle is repeated to continuously transfer heat from one end to the other. The present invention does not consume any additional energy and can maintain a microenvironment of the bottom space of the air-to-heat pump base above 0°C. It uses heat pipes to take "heat" from the soil, which is an active way of melting ice to prevent secondary freezing. It eliminates the phenomenon of secondary freezing of condensed water in the bottom space of the air-to-heat pump from the source, and solves the technical problem of partial freezing of the air-to-heat pump affecting the heating operation.

[0036] The heat pipe condensation section 101 is arranged above the ground surface 203; the heat pipe insulation section 103 is arranged in the frozen soil layer 201; the heat pipe evaporation section 102 is arranged in the constant temperature soil layer 2, and a drainage cushion layer 202 is arranged above the ground surface 203. The drainage cushion layer 202 is a cement casting layer and is slightly higher than the ground surface 203, so as to facilitate the condensed water to be discharged from the high drainage cushion layer 202 to the ground surface 203 and flow into the drainage ditch.

[0037] A heat storage hydrophobic gravel layer 3 is arranged above the drainage cushion layer 202, and the lower section of the heat pipe condensation section 101 is located in the heat storage hydrophobic gravel layer 3. The heat storage hydrophobic gravel layer 3 is covered with a mixture of coarse and fine gravel, and the mass ratio of 40% pebbles (coarse) and 60% fine sand constitutes the heat storage hydrophobic gravel layer 3. 70% of the total length of the heat pipe condensation section is buried in the heat storage hydrophobic layer composed of sand and gravel. Pebbles (coarse) stones form water gaps, which is conducive to the flow, penetration and enhanced heat exchange effect of defrosting condensed water; 60% of fine sand in the heat storage hydrophobic layer fills the gaps of pebbles (coarse) stones, which is conducive to the heat conduction of heat pipe condensation. The heat pipe evaporation section has annular heat exchange fins, which is covered by the heat storage hydrophobic layer for about 60-80% of the condensation section length. The released heat is stored by the sand and gravel layer of the heat storage hydrophobic layer and maintained above 0°C, so as to ensure that the condensed water of the heat pump defrosting is above 0°C, maintained in liquid state and flows away. The more defrost water in the heat pump, the greater the temperature difference between the condensation section and the evaporation section of the heat pipe, the higher the heat exchange efficiency of the heat pipe. Even in extreme conditions of freezing rain, the microenvironment at the bottom of the heat pump can still be kept above 0°C.

[0038] The upper section of the heat pipe condensation section 101 is located at the bottom space 401 on the lower side of the main frame bracket 4 of the air energy heat pump group. The length of the heat pipe condensation section 101 is less than 60 cm. The upper section of the heat pipe condensation section 101 accounts for 20-40% of the length of the heat pipe condensation section 101. Part of the heat pipe condensation section 101 is exposed to the heat storage hydrophobic layer. The heat pipe condensation section can be used for direct heat exchange to prevent a small amount of ice waterfalls from occurring under extreme working conditions. At the same time, supercooled water is preheated and infiltrated into the sand and gravel of the heat storage hydrophobic layer for further insulation and heat absorption, so as to prevent the air energy heat pump defrosting condensed water from freezing again at the bottom of the base.

[0039] The heat pipe condensation section is a structural form with annular heat exchange fins as heat exchange fins, which enhances the condensation heat exchange effect. The evaporation section is a light pipe, which is conducive to construction and burial in the soil. The heat pipe insulation section 103 passes through the frozen soil layer 201 and extends downward for more than 0.5m. The heat pipe evaporation section 102 is buried in the constant temperature soil layer 2 for a length of more than 10m. A fine sand filling layer 5 is arranged between the heat pipe evaporation section 102 and the constant temperature soil layer 2. The fine sand filling layer 5 is fine sand with a high thermal conductivity filled between the light pipe of the evaporation section and the soil pores and cracks to ensure the evaporation heat absorption effect of the gravity heat pipe, which is conducive to evaporation heat exchange between the heat pipe evaporation section 102 and the constant temperature soil layer 2.

[0040] The specific heat exchange working process is as follows:

[0041] The soil temperature below the frozen soil layer is constant and generally above 10°C. The gravity heat pipe 1 is a highly efficient heat transfer element. The heat pipe evaporation section 102 absorbs heat from the constant temperature soil layer 2 and then evaporates and transfers the heat to the heat pipe condensation section 101. The heat is dissipated through the heat pipe condensation section 101 to the cement drainage cushion layer 202 and the heat storage hydrophobic gravel layer 3 and is absorbed and stored by the cement, coarse sand and fine sand layer to maintain the main frame 4 of the air energy heat pump group. The bottom space 401 is always higher than the micro-environment above 0℃. 60-80% of the total length of the heat pipe condensation section is buried in the heat storage hydrophobic layer composed of sand and gravel. The cobblestone (coarse) stone structure forms a water flow gap, which is conducive to the flow, penetration and enhanced heat exchange effect of defrosting condensed water; 60% of the fine sand in the heat storage hydrophobic layer fills the cobblestone (coarse) stone gap, which is conducive to the heat conduction of heat pipe condensation. The heat pipe condensation section has annular heat exchange fins, which are covered by the heat storage hydrophobic layer for 60-80% of the condensation section length. The released heat is stored by the sand and gravel layer of the heat storage hydrophobic layer and maintained above 0℃, so as to ensure that the condensed water of the heat pump defrosting is maintained in liquid state above 0℃ and flows away. The more defrosting water in the heat pump, the greater the temperature difference between the condensation section and the evaporation section of the heat pipe, and the heat exchange efficiency of the heat pipe is improved. Even in the extreme case of freezing rain, the micro-environment state of the bottom space of the heat pump can still be maintained above 0℃. The heat pipe condensing section is a structural form with annular fins as heat exchange fins to enhance the condensation heat exchange effect. The evaporation section is a light pipe, which is convenient for construction and buried in the soil, and fine sand with high thermal conductivity is filled between the light pipe and the soil pores and cracks in the evaporation section to ensure the evaporation heat absorption effect of the gravity heat pipe; 20-40% of the total length of the heat pipe condensing section is exposed to the heat storage hydrophobic layer, and the heat pipe condensing section can be used for direct heat exchange to prevent a small amount of ice waterfalls under extreme conditions. At the same time, supercooled water is preheated and infiltrated into the sand and gravel of the heat storage hydrophobic layer for further insulation and heat absorption to prevent the defrosting condensed water of the air-to-energy heat pump from freezing again at the bottom of the base. The present invention does not consume any additional energy and can maintain a microenvironment above 0°C at the bottom space of the air-to-energy heat pump base. The heat pipe is used to take "heat" from the soil, which is an active way of melting ice to prevent secondary freezing. The phenomenon of secondary freezing of condensed water in the bottom space of the air-to-energy heat pump is eliminated from the source, solving the technical problem that partial freezing of the air-to-energy heat pump affects the heating operation.

[0042] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preventing secondary icing of an air energy heat pump heat pipe, characterized in that: It includes the following steps: S1: Site measurement, layout and positioning; determine the orientation and spacing according to the X and Y axis lines of the general design drawing based on the site conditions, and position on site by wedging positioning piles; S2: Hole-making process: Use hydraulic down-the-hole hammer drill to drill holes, and use high-pressure air as drilling power and slag removal means; S3: Gravity heat pipe assembly: Use a vacuum unit to evacuate the inside of the welded and sealed gravity heat pipe shell, then fill it with an appropriate amount of working liquid, and then perform cold welding and ultrasonic welding to seal it; The gravity heat pipe (1) comprises, from top to bottom, a heat pipe condensation section (101), a heat pipe insulation section (103), and a heat pipe evaporation section (102); the heat pipe condensation section (101) is arranged above the ground surface (203); the heat pipe insulation section (103) is arranged in a frozen soil layer (201); and the heat pipe evaporation section (102) is arranged in a constant temperature soil layer (2); An annular fin is provided on the heat pipe condensation section (101); An air energy heat pump cluster mainframe support (4) is arranged above the heat pipe condensation section (101); the lower section of the heat pipe condensation section (101) is located in the heat storage hydrophobic gravel layer (3); and the upper section of the heat pipe condensation section (101) is located in the bottom space (401) below the air energy heat pump cluster mainframe support (4); The length of the upper section of the heat pipe condensation section (101) accounts for 20-40% of the total length of the heat pipe condensation section (101); S4: Gravity heat pipe installation: vertically install the assembled gravity heat pipe into the drilled hole in step S2; S5: filling with fine sand: filling fine sand between the bare pipe and the drilled hole gap of the evaporation section of the gravity heat pipe to form a fine sand filling layer; S6: Drainage cushion pouring: pour the drainage cushion with cement on the ground surface. The drainage cushion is mainly used to facilitate the condensed water to flow from high to low to the ground surface and into the drainage ditch; S7: Laying of thermal storage hydrophobic gravel layer: Laying of thermal storage hydrophobic gravel layer on the drainage cushion layer. The thermal storage hydrophobic gravel layer (3) is mainly a mixture of coarse and fine gravel, with a mass ratio of 40% pebbles and 60% fine sand.

2. A method for preventing secondary icing of an air energy heat pump heat pipe according to claim 1, characterized in that: The heat pipe condensation section (101) is less than 60 cm in length.

3. A method for preventing secondary icing of an air energy heat pump heat pipe according to claim 1, characterized in that: The heat pipe insulation section (103) passes through the frozen soil layer (201) and extends downward by more than 0.5 m.

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