JP2019132470A - Heat collecting and radiating tube and geothermal heat pump using the same - Google Patents

Abstract

To more improve heat collecting and radiating effect in a heat collecting and radiating tube of a direct expansion type geothermal heat pump causing refrigerant phase change.SOLUTION: A heat collecting and radiating tube of the present invention is a heat collecting and radiating tube for a direct expansion type geothermal heat pump which is housed in a casing pipe buried in the ground. The heat collecting and radiating tube comprises: a main pipe; and an adiabatic material covering a part of the main pipe. The main pipe comprises: first and second outflow/inflow ports for inflow or outflow of refrigerant; a first pipe from the first outflow/inflow port to the end; and a second pipe from the second outflow/inflow port to the end. The first pipe and the second pipe are connected to communicate with each other at the end, the first and second outflow/inflow ports are provided on the ground surface side of the casing pipe. The ends of the first pipe and the second pipe are located at a deepest position in the heat collecting and radiating tube when the casing pipe is buried, the first pipe is covered with the adiabatic material l at least to the end thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat collecting / radiating tube and a geothermal heat pump using the same, and more particularly to a heat collecting / radiating tube used for a direct expansion type geothermal heat pump and a geothermal heat pump using the same.

  There are an indirect system and a direct expansion system in the geothermal heat pump. The indirect system is a borehole in which the brine is provided in the ground by providing a heat exchanger between a refrigerant such as CFC substitute and water or antifreeze (referred to as brine) in the outdoor unit of the heat pump and supplying the heat of the coolant to the brine. It is introduced into a resin or metal pipe provided inside, and heat is collected from the ground indirectly through this brine. (Patent Documents 1 and 2)

  On the other hand, in the direct expansion method, a heat-dissipating tube composed of a copper circular tube is embedded in the ground (shallowing about 30m) shallower than the indirect method to form a ground heat exchanger, and the heat pump refrigerant is directly used as the ground heat. It is a method of introducing heat into the exchanger and collecting heat from the ground. For this reason, alternative chlorofluorocarbon refrigerants are used as the refrigerant.

  In the direct expansion method, refrigerant is introduced directly into the underground heat exchanger, so the underground heat exchanger becomes an evaporator during heating operation and a condenser during cooling operation. It becomes a flow with change.

  In the geothermal heat pump, various measures are taken in order to increase the efficiency of heat collection and radiation. For example, as shown in Patent Documents 1 and 2 and the like, there is shown a means for preventing unnecessary heat exchange from occurring by using a heat insulating material in a heat-dissipating tube or the like.

  Further, in the heat collecting and radiating pipe of the direct expansion type underground heat pump, it is necessary to take measures due to the fact that the refrigerant has undergone a phase change. For this reason, for example, as in Non-Patent Document 1, a heat collecting / radiating tube having a configuration in which a heat insulating material is wound around a part of a U-shaped heat collecting / radiating tube has been proposed.

JP 2014-005981 A JP 2014-084857 A

Norihiko Muramatsu et al., 2016 Annual Meeting of the Japan Society of Mechanical Engineers, Exchange performance of direct expansion type geothermal heat pump-Performance of geothermal heat exchanger, 2016/9 / 11-14

  There is a need for a measure to further improve the heat-dissipating effect in the heat-dissipating pipe of the direct expansion type geothermal heat pump that causes the phase change of the refrigerant.

  The heat collecting and radiating pipe of the present invention is a heat collecting and radiating pipe for a direct expansion type underground heat pump that is housed in a casing pipe embedded in the ground, and the heat collecting and radiating pipe includes the main pipe and a part of the main pipe. The main pipe includes first and second outlets through which refrigerant flows in and out, a first pipe from the first outlet to the end, and a second outlet. A second pipe from the inlet to the end, the first pipe and the second pipe are connected to communicate with each other at the end, and the first and second outlets are on the ground surface side of the casing pipe When the casing tube is embedded, the end portion is located at the deepest in the heat-radiating / radiating tube, the first tube is covered with the heat insulating material, and the heat insulating material covers at least the end portion of the heat insulating material. It was configured as described above.

  The geothermal heat pump of the present invention includes the heat collecting and radiating pipe.

  It is possible to increase the efficiency of the heat collecting and radiating pipe of the direct expansion type geothermal heat pump.

It is a figure which shows the 1st example of the heat collecting / radiating tube of this invention. It is a figure which shows an example of the underground heat pump using the heat collecting / radiating pipe of this invention. It is a figure which shows the 2nd example of the heat collecting and radiating tube of this invention. It is a figure which shows the 3rd example of the heat collecting and radiating tube of this invention.

Example 1
(Constitution)
FIG. 1 shows a first example of the heat collecting and radiating pipe of the present invention, and FIG. 2 shows an example of a geothermal heat pump using the heat collecting and radiating pipe 11 of the present invention.

  As shown in FIG. 1, the heat-dissipating pipe 11 has a main pipe 4 and a heat insulating material 5 covering a part thereof. The main pipe 4 is a U-shaped pipe provided with refrigerant outlets 1 and 2 and is a main body of the pipe through which the refrigerant flows. The outflow inlets 1 and 2 are refrigerant inlets or outlets depending on the operation mode of the geothermal heat pump. Further, the main pipe 4 includes a first pipe 41 from the first outflow inlet 1 to the end 3 and a second pipe 42 from the second outflow inlet 2 to the end 3. The tube 41 and the second tube 42 are connected to communicate with each other at the end 3. Further, the first pipe 41 is covered with a heat insulating material (heat insulating material) 5 and is configured to cover at least the heat insulating material 5 to the end portion 3. Here, the end 3 is a portion corresponding to the deepest position when the main pipe 4 is installed in the ground as shown in FIG. Accordingly, the end (or end point) 3 is the deepest part or the lowest part of the main pipe 4.

  In the example of FIG. 1, the first pipe 41 includes a straight part 41 a that extends linearly from the first outflow inlet 1 toward the end part 3, and a curved part 41 b that forms a U-shaped bottom by bending the pipe 41. And have. The straight portion 41a and the curved portion 41b are configured such that the tubes communicate with each other at a point B at which the tube 41 begins to bend. Similarly, the second pipe 42 has a straight part 42a extending linearly from the second outflow inlet 2 toward the end part 3, and a curved part 42b forming a U-shaped bottom by bending the pipe 42. ing. The straight portion 42a and the curved portion 42b are configured such that the tubes communicate with each other at a point C at which the tube 42 begins to bend. In addition, you may comprise the point B and the point C so that it may become parallel to a horizontal surface, when the underground heat pump using the heat collecting / radiating pipe 11 is installed in the ground.

  For example, a copper pipe can be used as the main pipe 4. Further, for example, a diameter of about 3/8 inch can be used.

  In the example illustrated in FIG. 1, the heat insulating material 5 includes a heat insulating material 51 that covers the straight portion 41 a of the first pipe 41 and a heat insulating material 52 that covers the curved portion 41 b of the first pipe 41. The heat insulating material 5 may be covered until it includes the first flow revenue port 1. Alternatively, the main pipe 4 may cover the water surface portion of the filled water 7 in the casing pipe 6. Preferably, all the piping from the first outlet to the air conditioner may be covered with the heat insulating material 5. In addition, as long as the performance is achieved, it may be up to a portion that is slightly immersed in water 7 as shown in FIG.

  In the geothermal heat pump in this example, a casing pipe 6 is placed in a bore hole 9 formed on the ground, and the casing pipe 6 is filled with water 7 and the above-described heat-dissipating pipe 11 is installed in the casing pipe 6. Here, the space between the casing tube 6 and the bore hole 9 may be filled with the sand 8.

  As the refrigerant, for example, alternative chlorofluorocarbons such as R410A and R32 can be used.

  In this example, it is a heat collecting / radiating pipe 11 for a direct expansion type underground heat pump which is housed in a casing pipe 6 embedded in the ground, and the heat collecting / radiating pipe 11 is a heat insulating material covering the main pipe 4 and a part thereof. 5 and the main pipe 4 includes first and second outlets (1, 2) through which the refrigerant flows in or out, and a first pipe 41 from the first outlet 1 to the end 3; A second pipe 42 from the second outflow inlet 2 to the end 3, and the first pipe 41 and the second pipe 42 are connected to communicate with each other at the end 3, and the first and second 2 is provided on the ground surface side of the casing tube, the end 3 is located at the deepest in the heat-radiating / radiating tube when the casing tube is buried, and the first tube 41 is a heat insulating material (heat insulating material) 5. The heat-dissipating tube 11 is configured so that the heat insulating material 5 covers the first tube 41 up to at least the end 3.

(Operation)
In the heating operation, liquid refrigerant is caused to flow from the outlet 1 (first outlet) of the main pipe 4 of the heat collection and discharge pipe 11. Here, the first pipe 41 of the main pipe 4 covers up to the end (lowermost part) 3 with the heat insulating material 5. For this reason, when the liquid refrigerant flows through the first pipe 41 of the main pipe 4 from the ground, it receives heat from the ground and does not evaporate (evaporate).

  In other words, the heat of the refrigerant in the main pipe 4 is covered with the heat insulating material (heat insulating material) 5 up to the portion where the flow of the refrigerant is reversed from the downward flow to the upward flow (up to the portion including the end portion 3). Yes. As a result, bubbles are not generated by evaporation while the liquid refrigerant in the main pipe 4 flows down, and generation of bubbles is eliminated until the liquid refrigerant is reversed to an upward flow. In other words, the 2nd pipe | tube 42 without the heat insulating material 5 operate | moves as an evaporator, and the 1st pipe | tube 41 covered with the heat insulating material 5 can be considered as a bubble removal apparatus. The refrigerant that has passed through the end portion 3 flows upward through the second pipe 42 of the main pipe 4 and evaporates (vaporizes) by receiving heat from the ground. The evaporated (vaporized) warm refrigerant flows out from the outflow port 2 (second outflow port) of the main pipe 4 and is used for heating.

  On the other hand, in the cooling operation, gaseous refrigerant is caused to flow from the outflow inlet 2 (second outflow inlet) of the main pipe 4 of the heat collection and discharge pipe 11. Here, the first pipe 41 of the main pipe 4 covers up to the end (lowermost part) 3 with the heat insulating material 5. For this reason, after the gaseous refrigerant flows from the ground down the second pipe 42 of the main pipe 4 to the ground, it dissipates heat and condenses to become a liquid refrigerant, and then reverses at the end (lowermost part) 3. The liquid refrigerant operates so that it does not evaporate (evaporate) again by receiving heat from the ground while it rises to the ground via the first pipe 41 of the main pipe 4. In other words, the second tube 42 without the heat insulating material 5 operates as a condenser, and the first tube 41 covered with the heat insulating material 5 can be regarded as a bubble eliminator. The refrigerant that has passed through the end portion 3 flows upward through the first pipe 41 of the main pipe 4, and is taken out as a refrigerant cooled in liquid form from the outlet 1 of the main pipe 4 without evaporating (vaporizing) again. Used for cooling.

(Example 2)
FIG. 3 shows a second example of the present invention. FIG. 3 shows an example in which the heat-radiating / radiating tube 11 of FIG. 1 is replaced with a heat-radiating / radiating tube 11 ′. 3 is a figure which shows the case where it covers with the heat insulating material 5 from the edge part 3 to the curved part 42b of the 2nd pipe | tube 42 of the main pipe 4 of the heat-dissipation pipe | tube 11 '. This is the same as the example shown in FIG. The heat insulating material 5 includes a heat insulating material 51 that covers the straight portion 41 a of the first pipe 41 and a heat insulating material 52 ′ that covers the curved portion 41 b of the first tube 41 and the curved portion 42 b of the second tube 42. The heat insulating material 52 ′ is configured to completely include the end 3. And by comprising in this way, it has covered even the part which the direction which a refrigerant | coolant flows completely switches. In other words, the second tube 42 is further covered with the heat insulating material 5 from the end portion 3 to a portion where the second tube 42 is formed in a direction perpendicular to the ground surface. As a result, it is possible to more completely prevent the generation of bubbles in the first pipe 41 and the backflow of the generated bubbles during cooling and heating, and increase efficiency. In this example, the portion without the heat insulating material 5 in the second pipe 42 functions as an evaporator (during heating operation) or a condenser (during cooling operation).

  In addition, when it is comprised so that it may become parallel to a horizontal surface when the geothermal heat pump using the heat extraction pipe | tube 11 'is installed in the ground, the point B and the point C are points beyond the edge part 3. It is good to cover up to C with the heat insulating material 5. More preferably, the second pipe 42 of the main pipe 4 of the heat collecting and radiating pipe 11 ′ is covered with a heat insulating material 52 ′ up to a position higher than the end 3 by 100 mm or more.

Example 3
FIG. 4 shows a third example of the present invention. FIG. 4 shows an example in which the heat-radiating / radiating tube 11 shown in FIG. 1 is replaced with a heat-radiating / radiating tube 11 ″. Specifically, FIG. 4 is obtained by replacing the second pipe 42 of the main pipe 4 of the heat-dissipating pipe 11 in FIG. 1 with a second pipe 42 ′ having a plurality of parallel pipes. Alternatively, the second pipe 42 is configured to include a plurality of pipes connected via the branch pipe part (branch part) 10 and arranged in parallel to each other. In FIG. 4, the heat insulating material covers the first pipe 41 to the end 3 as in the example of FIG. 1. Instead of this, the heat insulating material 5 may cover the curved portion 42b of the second tube 42 of the heat-dissipating tube 4 beyond the end portion 3 as in the example of FIG. Or you may make it cover to the branch pipe part 10 to a further several parallel pipe | tube.

  By adopting such a configuration, the heat transfer area can be increased in a portion of the second pipe 42 that is not wound with the heat insulating material 5 serving as a condenser during the cooling operation, thereby further improving efficiency. It is done. Furthermore, it is effective to configure the condensing unit using a plurality of copper circular tubes each having a diameter smaller than that of the first tube. For the reasons described later, the number of parallel pipes is preferably an odd number (excluding 1), and more preferably 3.

(Experiment / Discussion)
During heating operation, the heat collecting / radiating tube becomes an evaporator, so the liquid-phase refrigerant that flows down when the liquid-phase refrigerant collects heat from the ground and evaporates at the portion where it flows down from the inlet of the heat / radiating tube. Evaporated bubbles can be generated from the surface of the heat collection and discharge tube. For this reason, buoyancy occurs due to bubble generation by evaporation in the refrigerant flowing down, the flow resistance of the refrigerant flow increases, and the load on the compressor increases, resulting in an increase in power consumption. On the other hand, during the cooling operation, when the gas-phase refrigerant flows down the heat collecting and radiating pipe, it dissipates heat into the ground and condenses, and the liquid-phase refrigerant reverses and rises at the bottom of the heat exchanger. When a part of the heat radiated from the heat collecting / radiating pipe corresponding to the part where the water or gas-phase refrigerant flows down is transferred to the heat collecting / radiating pipe corresponding to the part where the liquefied refrigerant rises, the heat evaporates again and the refrigerant evaporates. The total heat dissipation from the heat exchanger is reduced, which reduces the coefficient of performance and degrades performance.

  In order to prevent performance degradation due to these, a portion corresponding to the pipe 41a in FIG. 1 is used by using a heat insulating material having a minute air layer that is used for heat insulation of a connection copper pipe of the outdoor unit of the commercially available air heat heat pump and the indoor unit. When covered, it can suppress the evaporation of the liquid phase refrigerant in the heat collection / radiation tube where the refrigerant flows down during heating operation and the re-evaporation of the liquid phase refrigerant in the heat collection / radiation tube where the refrigerant rises during cooling operation. Performance improved.

  However, it was visually confirmed that the heat insulating material was crushed by the water pressure in the casing tube filled with water at a depth deeper than 10 m underground. From this, it was considered that the heat insulation performance was lowered, and although the performance was improved to some extent, the following construction was indispensable for the optimum design.

  First, it is necessary to prevent the refrigerant from condensing and evaporating as much as possible in a portion that functions as a condenser or an evaporator in the U-shaped heat radiation pipe. In particular, at the part where the liquid refrigerant flows down in the U-shaped heat collecting / radiating pipe during heating or hot water supply operation, the load on the compressor increases when evaporating bubbles are generated in the flow of the liquid refrigerant due to heat received from the heat collecting / radiating pipe wall, As the power consumption increases, the coefficient of performance may drop significantly. For this reason, as in Example 1, the heat-dissipating tube 11 needs to be covered with the heat insulating material 5 up to at least the end 3. Preferably, as in the second embodiment, the curved portion 42a of the second pipe 42 of the main pipe 4 of the heat collection and discharge pipe 11 'may be covered with the heat insulating material 52'. Furthermore, in Example 2, it is more preferable that the second pipe 42 of the heat collecting and radiating pipe 4 insulates a section from the end 3 to a position higher by 100 mm or more.

  Moreover, it is necessary to confirm that the flow is turbulent from the Reynolds number when the circular pipe diameter is D as the liquid refrigerant. At this time, the flow from the end 3 of the main pipe 4 to the branch pipe to the plurality of pipes is required. The straight pipe portion distance is required to be about 20D or more.

  As a result, it is possible to reliably prevent the vapor phase refrigerant that has evaporated during the flow of the liquid refrigerant from being mixed, and as a result, the increase in power consumption of the compressor can be greatly suppressed, and the coefficient of performance is greatly reduced. Can be prevented and energy saving performance can be maintained.

  During the cooling operation, a part of the heat collecting and radiating pipe (11, 11 ', 11 ") is caused to function as a condenser. When the gas-phase refrigerant flows down the heat collecting / radiating pipe (11, 11 ′, 11 ″), it dissipates heat into the ground and condenses, so that the heat collecting / radiating pipe (11, 11 ′, 11 ″), a plurality of copper circular pipes having a reduced diameter were used for the second pipe 42 of the main pipe 4 of the heat collecting and radiating pipe so as to increase the heat transfer area. The plurality of copper circular tubes were configured to be a condensing part.

  In this experiment, the number of the plurality of tubes was two or four. In particular, when functioning as an evaporator for heating operation, vibrations were observed in the refrigerant flow in the plurality of circular tube passages, and stable It was confirmed that the refrigerant could not evaporate. Furthermore, in the case of a parallel borehole with two boreholes containing heat exchangers, it was confirmed that the performance at the time of heating operation is not stable, so it is not easy to stably distribute the flow rate with the combination of two boreholes. I understood. Therefore, an odd number (1 or 3 or 5) of copper circular pipes is preferable as the portion corresponding to the condensing part in the second pipe 42 of the main pipe 4 of the heat collecting and discharging pipe. In particular, the optimum number of tubes is three. This is because it is easy to equalize the flow rate distribution because the distance between the circular pipes can be made equal by arranging them in equilateral triangles when manufacturing the branch pipe part (branch part). By adopting this configuration as shown in the third embodiment, it is possible to further suppress the increase in power consumption of the compressor and increase the efficiency.

  In addition to this, the heat insulating material can be prevented from being deformed by water pressure while maintaining the heat insulating performance by installing a material having low thermal conductivity, such as polyethylene pipe or VP pipe, outside the copper pipe. By maintaining the above, it is possible to prevent a decrease in energy saving performance.

  It is confirmed from the consideration of the temperature change in the borehole that the condensation process during the cooling operation is completed if the distance between the plurality of pipe portions accommodated in the borehole is 20 m at the minimum and 30 m at the maximum. If heat insulation is performed from the second pipe 42 of the main pipe 4 of the heat collecting / radiating pipe, which is at a position higher than 100 mm, to the ground pipe section, it is possible to further suppress the increase in power consumption of the compressor and increase the efficiency.

  For convenience of explanation, the heat-dissipating tube is U-shaped in the embodiment, but the present invention can be applied to other shapes. For example, the second tube may be a spiral tube. The cross section of the tube is not limited to a circle, but may be an ellipse or a rectangle.

1, 2 Outlet 3 End 4 Main pipe 5 Heat insulating material 6 Casing pipe 7 Water 8 Silica sand 9 Bore hole 10 Branch pipe section 11, 11 ′, 11 ″ Heat collecting / radiating pipe

Claims (12)

It is a heat-dissipating pipe for a direct expansion type underground heat pump that is housed in a casing pipe buried in the ground,
The heat collecting and radiating pipe includes a main pipe and a heat insulating material covering a part of the main pipe,
The main
First and second outlets through which refrigerant flows in and out;
A first tube from the first outlet to the end;
A second pipe from the second outlet to the end,
The first tube and the second tube are connected to communicate with each other at the end;
The first and second outlets are provided on the ground surface side of the casing pipe,
The end portion is located at the deepest in the heat collecting and radiating pipe when the casing pipe is buried,
The said 1st pipe | tube is covered with the said heat insulating material, and the said heat insulating material covers the said 1st pipe | tube with the said heat insulating material at least to the said edge part.   The heat-radiating tube according to claim 1, wherein the second tube is further covered with the heat insulating material from the end portion to a portion where the second tube is formed in a direction perpendicular to the ground surface.   3. The heat-dissipating tube according to claim 1, wherein the second tube is further covered with the heat insulating material to a position higher than the end by 100 mm or more.   The said 2nd pipe | tube has several pipe | tubes connected through the branch pipe part and arrange | positioned in parallel with each other, The heat collecting / radiating pipe | tube as described in any one of Claim 1 thru | or 3 characterized by the above-mentioned. .   The heat collecting / radiating pipe according to claim 4, wherein a second pipe is covered with the heat insulating material from the end to the branch pipe.   The heat-radiating tube according to claim 4, wherein the plurality of tubes is an odd number excluding 1.   The heat collecting / radiating tube according to claim 4, wherein the plurality of tubes are three.   The diameter of the said some pipe | tube is a heat collecting / radiating pipe as described in any one of Claims 4 thru | or 7 smaller than the diameter of a said 1st pipe | tube.   The heat dissipation according to any one of claims 1 to 8, wherein evaporation of the refrigerant is started from a portion not covered with the heat insulating material when the liquid refrigerant flows from the first outlet / inlet. tube.   When the gas-phase refrigerant flows from the first inlet / outlet, the refrigerant condenses into the liquid-phase refrigerant before reaching the location not covered by the heat-insulating material, and covers the heat-insulating material. The heat collecting / radiating tube according to claim 1, wherein the refrigerant does not evaporate again when flowing through the broken heat collecting / radiating tube.   The heat-radiating tube according to claim 1, wherein the heat insulating material is a member that is not deformed by water pressure.   A geothermal heat pump comprising the heat-dissipating tube according to any one of claims 1 to 11.