CN102245978B - Heat collecting method and heat collecting device for solar heat - Google Patents

Abstract

A heat collection device, the purpose of which is to realize a solar heat collection method that does not require power, can save energy, can simplify the structure of the device to achieve low cost, and can obtain a high recovery temperature even in winter. The thermal device is equipped with a heat collector (2) and a heat exchanger (3), and the heat collector (2) forms a closed circuit (1) in which a working fluid with _CO2 as the main fluid, that is, a _CO2 fluid circulates, and the heat collector (2) Hotter than the _CO2 fluid, the heat exchanger (3) recovers heat from the heat-collected _CO2 fluid, and the heat-collecting device is equipped with: recovering the potential heat of the _CO2 fluid (w) to liquefy it, and There is a height difference between the inlet side where the _CO2 fluid (w) flows in and the outlet side where the _CO2 fluid (w) flows out, and the heat of the head pressure (H) generated by the _CO2 fluid (w) is formed on the outlet side The exchanger (3); intervenes in the closed circuit (1) and gathers heat in the liquefied _CO Fluid (w) so that the _CO fluid (w) on the outlet side becomes a heat collector (2) in a supercritical state, A natural circulation of _CO2 fluid (w) is formed in the closed circuit (1).

Description

Heat-gathering method and heat-gathering device of solar energy

technical field

The present invention relates to the invention of utilizing a closed circuit in which a working fluid with _CO2 as the main fluid is circulated to realize heat collection of solar energy, especially relates to the ability to circulate _CO2 fluid without power to collect heat with high efficiency and low cost And the heat collecting method and device of solar energy utilizing solar energy.

Background technique

In recent years, against the background of environmental pollution problems such as global warming caused by greenhouse gases and the depletion of fossil fuels, research related to the development and practical application of new energy instead of fossil fuels is being conducted. Among them, solar energy irradiates almost all of the earth, and its energy is overwhelming and inexhaustible compared with other natural energies. Therefore, many researches and practical applications related to the effective use of solar energy are being carried out.

As the effect of using natural energy including solar energy, there are energy saving and reduction of carbon dioxide emission, but as a problem in the utilization of solar energy, the reduction of the installation area of the solar energy utilization system, the improvement of the heat collection rate, and the lower price are desired. .

The present applicants first proposed a solar energy system that utilizes solar energy to simultaneously supply power generation, cooling and heating, and hot water supply in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-263944 ). The system includes: using CO ₂ , NH ₃ , H ₂ O, hydrocarbon natural refrigerants as the working fluid, and using the liquefied CO ₂ fluid as the pumping part of the supercritical pressure fluid; using solar energy to make the supercritical pressure fluid become An evaporator for high-temperature supercritical pressure fluid; an expansion turbine that adiabatically expands the high-temperature supercritical pressure fluid to form low-pressure gas and generate electricity; recovers heat from low-pressure gas to form liquefied and supercritical, close to supercritical, and less than critical Heat recovery for working fluid.

The solar system disclosed in Patent Document 1 has problems in that pump power for forcibly circulating a working fluid is required in the system, the device becomes large-scale, and the equipment cost and maintenance cost are high.

Generally, solar energy utilization systems have the problems of poor heat collection efficiency and large equipment investment. Especially in winter, the recovery temperature is low, and additional fuel needs to be added during utilization. Furthermore, in the system disclosed in Patent Document 1, power is required for heat collection itself, and there is a problem that heat utilization is poor because of batch-type heat recovery.

[Patent Document 1] Japanese Patent Laid-Open No. 2004-263944

Contents of the invention

In view of the problems of the above-mentioned prior art, an object of the present invention is to realize a solar heat collection method that does not require power, can save energy, can simplify the structure of the device, realize cost reduction, and can obtain a high recovery temperature even in winter .

In order to achieve the above object, the solar energy heat collection method of the present invention is provided with a solar heat collector and a heat exchanger by intervening, and the solar heat collector is formed with _CO2 as the main fluid of the working fluid (hereinafter referred to as _CO2 fluid) performing a circulating closed circuit and concentrating solar energy in the closed circuit, the heat exchanger having heat transfer tubes through which the _CO2 fluid flows, thereby concentrating solar energy on the _CO2 fluid circulating in the closed circuit, and The heat of the _CO fluid is recovered through a heat exchanger, and the method for concentrating solar energy is characterized in that,

The closed circuit is a closed circuit that does not intervene in the physical forced circulation equipment that is accompanied by the compression or head action of the _CO2 fluid,

The heat transfer tube installed in the closed circuit heat exchanger is provided with a height difference so that the suction side of the working fluid is high and the discharge side is low, and a liquid head is formed on the _CO2 fluid discharge side of the heat transfer tube pressure,

The liquid phase part (hereinafter referred to as the boundary between the liquid phase part and the supercritical state) until the heating of the _CO liquid that flows into the heat collecting tube in the heat collecting tube installed on the solar heat collector starts and changes into a supercritical state Part called supercritical interface) is arranged to be inclined upward toward the downstream side of the flow direction of the CO ₂ fluid, and is heated by solar heat concentrating by the solar heat collector so that the supercritical temperature of the CO ₂ fluid in the heat collector The interface is located in the heat collecting pipe of the heat collector, so that the _CO2 fluid on the outlet side of the heat collector is formed into a supercritical state, thereby forming a natural circulation of the _CO2 fluid in the closed circuit, preferably, based on the detection of the heat collector The detection value of the detector whether the _CO2 fluid in the fluid has a supercritical state is adjusted by the opening and closing of the flow regulating valve arranged on the closed circuit, and the solar heat concentrator is used to heat the concentrator so that the concentrator The supercritical interface of the _CO2 fluid in the heat collector is located in the heat collecting tube of the heat collector, so that the _CO2 fluid at the outlet side of the heat collector becomes supercritical.

In addition, the solar heat collection device of the present invention is interposed with a solar heat collector and a heat exchanger, and the solar heat collector is formed with a working fluid (hereinafter referred to as CO ₂ fluid) that circulates CO ₂ as the main fluid. a closed circuit in which _CO2 is heated by solar heat concentration, the heat exchanger is provided with heat transfer tubes through which the _CO2 fluid flows, thereby concentrating solar heat on the _CO2 fluid circulating in the closed circuit, And the heat of the _CO fluid is recovered through a heat exchanger, and the heat collecting device of said solar energy is characterized in that,

The closed circuit is a closed circuit that does not intervene in the physical forced circulation equipment that is accompanied by the compression or head action of the _CO2 fluid,

The heat transfer tube installed in the closed circuit heat exchanger is provided with a height difference so that the suction side of the working fluid is high and the discharge side is low, and a liquid head is formed on the _CO2 fluid discharge side of the heat transfer tube pressure,

The liquid phase part (hereinafter referred to as the boundary between the liquid phase part and the supercritical state) until the heating of the _CO liquid that flows into the heat collecting tube in the heat collecting tube installed on the solar heat collector starts and changes into a supercritical state Part is called the supercritical interface) is configured to be inclined upward toward the downstream side of the flow direction of the _CO2 fluid, and the heat collecting device of the solar energy is equipped with: a detection device for detecting whether the _CO2 fluid in the heat collector has a supercritical state device; be arranged on the closed circuit and control the flow regulating valve of the _CO fluid amount in the heat collecting tube; based on the detected value of the detector, the controller for opening and closing the flow regulating valve,

The controller is to adjust the opening and closing of the flow regulating valve, and use solar energy to heat the solar heat collector to make the CO in the solar heat collector _The supercritical interface of the fluid is located in the heat collector A controller that makes the CO ₂ fluid on the outlet side of the heat collector into a supercritical state in the heat collector tube.

In the method of the present invention, a working fluid with _CO2 as the main fluid is used. The higher the pressure of _CO2 , the lower the specific heat, and the heat accumulation becomes easier especially at high temperatures. Moreover, even at high pressure and high density, the viscosity does not change significantly, but it becomes a supercritical state above the critical point (pressure 7.3MPa, temperature 31°C). Since the viscosity decreases in the supercritical state, the working fluid accumulates heat. The moving power can be reduced when circulating in a closed circuit arranged between the heat exchanger and the heat exchanger. In addition, the latent heat of the _CO fluid is recovered by the heat exchanger to liquefy the _CO fluid, and the liquid head pressure of the liquefied _CO fluid is formed in the closed circuit at the outlet of the heat transfer tube of the heat exchanger. , so that the CO ₂ fluid naturally circulates in this closed circuit. Therefore, there is no need to intervene in a closed circuit to install physical forced circulation equipment accompanying the compression or lift of the CO ₂ fluid.

In addition, in the device of the present invention, a height difference is set on the inflow side of the _CO2 fluid of the heat transfer tube of the heat exchanger and the outflow side from which the _CO2 fluid flows out, and a closed circuit formed on the outflow side of the _CO2 fluid is formed by _CO2 The head pressure created by the fluid, thereby allowing the _CO2 fluid to circulate naturally in this closed circuit.

In addition, since CO ₂ is liquefied or gasified (or critical) in the normal temperature range, by utilizing the phase change near the normal temperature range, a natural circulation flow can be formed without power, and heat can be continuously carried out through this circulation flow. move.

Thus, in the present invention, using the working fluid with _CO2 as the main fluid, the head pressure of the _CO2 fluid is formed on the outlet side of the heat exchanger that recovers heat from the _CO2 fluid, and on the outlet side of the heat collector Make the CO ₂ fluid into a supercritical state, thereby forming a natural circulation of the CO ₂ fluid in a closed circuit, thereby, by circulating the CO ₂ fluid without power, the structure of the device can be simplified, energy saving and low cost can be realized.

In the method of the present invention, it is preferable to arrange at least a part of the heat collecting tube provided on the heat collecting device until the _CO fluid is heated and changed to a supercritical state to be inclined upward toward the downstream side of the flow direction of the _CO fluid. With such a configuration, the CO ₂ fluid in the supercritical state due to the phase change (liquid → supercritical state) of the CO ₂ fluid in the upwardly inclined heat collecting tube generates an upward force toward the outlet side of the heat collector. And, the lifting force acts to contribute to the formation of natural circulation in the closed circuit.

Since the amount of heat collected by the heat collector or the ambient temperature fluctuates day by day, or the amount of heat collected by solar energy fluctuates due to seasons, etc., it is necessary to heat the _CO2 fluid at a high temperature to efficiently recover heat, or to suppress the circulation of the _CO2 fluid volume to prevent high pressure. In the method of the present invention, it is preferable to detect whether the _CO2 fluid has a supercritical state by means of a detector arranged on the outlet side closed circuit of the heat collector, and to adjust and intervene on the outlet side of the heat collector according to the detection result The opening of the flow adjustment valve on the closed circuit connected to the inlet side of the heat exchanger is always formed in the closed circuit at the outlet side of the heat collector to form a supercritical state of CO _fluid .

As a result, since the closed circuit on the outlet side of the heat collector can always form the supercritical state of the _CO fluid, it is possible to increase the heat of _CO fluid accumulation, and make the _CO fluid high temperature to improve the heat recovery efficiency of the heat exchanger , or it is possible to control the circulation amount of the CO ₂ fluid to prevent high pressure in the closed circuit. Therefore, the temperature of the heat recovery fluid can be controlled to a necessary temperature according to the application, or a high temperature heat recovery fluid can be obtained even when the amount of sunlight from the sun in winter is small.

It should be noted that as a detector for detecting whether the _CO2 fluid has a supercritical state, a device that measures the amount of solar radiation and calculates the amount of heat collected by the heat collector based on the amount of sunlight, or a device that measures the amount of heat collected by the heat collector can be used. The temperature difference or pressure difference of the CO ₂ fluid at the inlet and outlet of the collector and the equipment that calculates the heat accumulation amount of the heat collector based on the measured value, or the temperature or pressure of the CO ₂ fluid at the outlet of the heat collector is detected and calculated based on the detected value A device for detecting the supercritical state of _CO2 fluid.

In addition, in the method of the present invention, preferably, a fluid obtained by mixing CO ₂ and dimethyl ether at 1 to 35 mol % relative to CO ₂ is used as the working fluid. When the heat recovery fluid is circulated through the heat exchanger to recover heat, the temperature of the heat recovery fluid supplied to the heat exchanger rises when the amount of heat collected by the heat collector is large, such as in summer, and CO of the heat exchanger is generated. ₂ Insufficient condensation of the fluid.

As a working fluid, when mixing dimethyl ether to CO ₂ , dimethyl ether dissolves in CO ₂ . As a result, the boiling point of the CO ₂ fluid is higher than that of CO ₂ alone.

The critical temperature of carbon dioxide is 31.05°C, but by mixing dimethyl ether, the condensation temperature of _CO2 fluid can be increased. Thus, even if the temperature domain of the _CO2 fluid is raised, it is easy to condense. Therefore, in the heat exchanger, the _CO2 fluid is easy to liquefy, and the liquid head pressure is easy to form, so the natural circulation of the closed loop can be stably formed.

In addition, the pressure of the CO ₂ fluid can be lowered by mixing dimethyl ether into the CO ₂ . _CO2 has the property that the vapor pressure increases to 3.485 MPa (273K), but by mixing dimethyl ether, the pressure of the _CO2 fluid can be lowered, and a closed-circuit piping system in which the _CO2 fluid flows can be formed at low cost. It should be noted that when the mixing ratio of dimethyl ether increases, it becomes flammable, and since the liquid viscosity of dimethyl ether is relatively high (149.0×10-6Pa/s (298K)), the conveying power increases. Therefore, it is preferable to use it at a mixing ratio of 1 to 35 mol% (non-combustible range or slightly flammable range) relative to CO ₂ .

In addition, in the method of the present invention, the working fluid is preferably a mixture of CO ₂ and a hydrocarbon-based natural refrigerant in an amount of 1 to 35 mol% relative to CO ₂ . In this way, when hydrocarbon-based natural refrigerants such as isobutane, propane, and ethane are mixed, there is an advantage of raising the condensation temperature and lowering the pressure of the CO ₂ fluid.

In addition, in the device of the present invention, it is preferable to arrange at least the part until the heating of the _CO fluid in the heat collecting tube provided on the heat collector until the heating of the CO fluid is changed to a supercritical state toward the downstream side in the flow direction of the _CO fluid. Inclined upwards so that the _CO2 fluid flows in from the bottom of the heat collector and out from the upper part, in said heat exchanger, the heat transfer tubes connected to said closed circuit are arranged downstream towards the direction of flow of the _CO2 fluid The side is sloped downward so that the _CO2 fluid flows in from the upper part of the heat exchanger and out from the bottom.

With the above configuration, since at least the part of the heat collecting tube installed on the heat collector until the heating of the CO ₂ fluid starts to change to a supercritical state is arranged upward, the phase change (liquid → supercritical state) of the CO ₂ fluid critical state), while the _CO2 fluid that becomes supercritical produces an upward force toward the outlet side of the heat collector. This lifting force acts to contribute to the formation of natural circulation within the closed circuit.

In addition, in the heat exchanger, since the heat transfer tube through which the _CO2 fluid flows is formed downward, the head pressure of the _CO2 fluid is easily formed on the outlet side of the heat exchanger. Thus, according to the structure, a natural circulation flow of the CO ₂ fluid is easily formed.

In order to form a natural circulation of the _CO fluid, usually the heat collector is arranged at the lower position and the heat exchanger is arranged at the upper position, but in the device of the present invention, _CO with low viscosity is used as the main fluid of the _CO fluid , and according to the above structure, even if the heat exchanger is arranged at the same height with respect to the heat collector, natural circulation can be performed. Therefore, the heat collecting device can be compacted without becoming bulky.

In addition, in the device of the present invention, it is preferable to include: a detector for detecting the temperature of the _CO fluid flowing into or out of the heat exchanger, or detecting the temperature of the heat recovery fluid flowing out of the heat exchanger; An inlet and outlet pipe through which the heat recovery fluid flows through the heat exchanger, and a flow adjustment valve provided on the inlet and outlet pipe; and a controller for adjusting the opening of the flow adjustment valve based on the temperature detection value of the detector. Accordingly, the temperature of the heat recovery fluid can be adjusted to a necessary temperature according to the application. Therefore, even when the amount of sunlight in winter is small, a high-temperature heat recovery fluid can be obtained.

In addition, in the device of the present invention, preferably, a branch line is provided in parallel in the closed circuit at the outlet of the heat exchanger, and a storage container for carbon dioxide liquefied via an on-off valve is provided in the branch line. The amount of _CO2 fluid in the storage vessel enables the head pressure of the _CO2 fluid to be adjusted.

The specific gravity of the _CO2 fluid is different in summer and winter. Therefore, the head pressure formed on the downstream side of the heat exchanger differs between summer and winter. When the liquid head pressure fluctuates, the natural circulation of the _CO2 fluid cannot be maintained stably. On the other hand, with the above configuration, the liquid head pressure can always be adjusted to a predetermined height, so that natural circulation can always be stably formed.

In addition, in the heat collector of the device of the present invention, preferably, the heat collector pipe through which the CO ₂ fluid flows is arranged inside the vacuum container. Accordingly, it is possible to reduce the diffusion of heat due to conduction and convection from the manifolds, thereby reducing heat loss.

【Invention effect】

In the method of the present invention, a height difference is set on the inflow side and the outflow side of the _CO2 fluid of the heat exchanger, and _{the CO2} fluid head pressure is formed on the CO2 fluid outflow side of the heat exchanger, and the heat accumulation of the heat collector is used to achieve The _CO2 fluid on the outlet side of the heat collector is made into a supercritical state, thereby forming a natural circulation of the CO2 fluid in the closed circuit where the _CO2 fluid flows, so no power is needed to circulate _{the CO2} fluid, energy can be saved, and the Simplify the device structure and achieve low cost.

In addition, the device of the present invention is equipped with: recovering the potential heat of the _CO2 fluid to liquefy it, and setting a height difference between the inflow side of the _CO2 fluid and the outflow side of the _CO2 fluid, and passing the CO2 on the outflow side of the _CO2 fluid. _2. A heat exchanger in which the fluid forms the liquid head pressure; a heat collector that is installed in a closed circuit of the CO ₂ fluid and collects heat in the liquefied CO ₂ fluid to make the CO ₂ fluid on the outlet side a supercritical state. Since the natural circulation of the _CO fluid is formed, the carbon dioxide flowing in the closed circuit can be naturally circulated, thereby saving energy by not requiring power for circulating the _CO fluid, and simplifying the structure of the device to achieve low cost.

Description of drawings

FIG. 1 is a system diagram of a first embodiment of the present invention.

Fig. 2 is a perspective view of the heat collector of the above-mentioned first embodiment.

Fig. 3 is an enlarged view of part A in Fig. 2 .

FIG. 4 is a Mollier diagram of the first embodiment described above.

Fig. 5 is a system diagram of a second embodiment of the present invention.

Fig. 6 is a system diagram of a third embodiment of the present invention.

Fig. 7 is a graph showing operating conditions of an example in which the above-mentioned first embodiment of the present invention is implemented.

Fig. 8 is a graph showing experimental data of the example.

Fig. 9 is a graph showing experimental data of the example.

Detailed ways

Hereinafter, the present invention will be described in detail using the illustrated embodiments. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not limited to specific descriptions, and are not limited to the scope of the present invention.

[Embodiment 1]

Next, a first embodiment of the solar heat collecting device of the present invention will be described based on FIGS. 1 to 4 . FIG. 1 is a system diagram of the present embodiment. In FIG. 1 , the heat collector 2 for collecting solar energy and the heat exchanger 3 for recovering the solar energy collected by the heat collector 2 are arranged approximately at the same height. A closed circuit 1 is provided between them, and the closed circuit 1 is composed of a flow path 1a connecting the outlet of the heat collector 2 and the inlet of the heat exchanger 3, and connecting the outlet of the heat exchanger 3 and the heat collector. The flow path 1b connected to the inlet of 2 constitutes, and the CO ₂ fluid circulates between the heat collector 2 and the heat exchanger 3 through the closed circuit 1. As the CO ₂ fluid, CO ₂ or a CO ₂ fluid composed of CO ₂ and dimethyl ether mixed in a ratio of 1 to 35 mol % relative to the CO ₂ can be used.

The structure of the heat collector 2 is demonstrated based on FIG.2 and FIG.3. Fig. 2 is a perspective view of the heat collector 2, and Fig. 3 is an enlarged view of part A in Fig. 2 . In FIGS. 2 and 3 , the lower collecting pipe 22 connected to the flow path 1b is arranged obliquely in the vertical direction, and its upper end is attached to the casing 21 of the heat collector 2 . The lower manifold 22 is connected to a lower head 23 arranged inside the casing 21 . A plurality of heat collecting pipes 24 are connected in parallel to the lower head 23 inside the casing 21 . The CO ₂ fluid w flowing into the lower header pipe 22 from the flow path 1 b is distributed to the heat collecting pipe 24 via the lower head 23 . The heat collecting tubes 24 are arranged obliquely in the vertical direction so that the inlet side is low and the outlet side is high, and are arranged so as to have a level difference between the inlet side and the outlet side.

The heat collecting tube 24 is surrounded by a transparent glass tube 25 of a sealed structure, and the inside of the glass tube 25 is kept in a vacuum state. Accordingly, it is possible to reduce the diffusion of heat due to heat conduction and heat convection from the heat collecting pipe 24 , and reduce heat loss.

A parabolic reflector 26 is arranged around the lower side of the glass tube 25 . The reflection plate 26 is composed of a parabola and an involute, and is produced by pressing an aluminum plate that has been given a reflective-increasing coating having a high reflectance. The sunlight s reflected by the reflector 26 is concentrated by the heat collecting tube 24 .

The CO ₂ fluid w is heated by the sunlight s concentrated toward the heat collecting pipe 24 while passing through the heat collecting pipe 24 . Then, the CO ₂ fluid w joins at the upper head 27 provided in the casing 21 and flows out toward the upper header 28 , and flows out from the upper header 28 to the flow path 1 a. The upper collecting pipe 28 is also arranged obliquely in the vertical direction, and its lower end is attached to the casing 21 . An unillustrated heat insulator made of glass wool or the like is arranged under the reflecting plate 26 to prevent heat from diffusing to the outside of the housing 21 .

In FIG. 1 , the CO ₂ fluid w heated by the heat collector 2 (at the outlet of the heat collector 2 is 70-90° C.) passes through the solenoid valve 9 and reaches the heat transfer pipe 3 a of the heat exchanger 3 . In the heat transfer pipe 3a of the heat exchanger 3, the inlet part of the _CO2 fluid w is connected with the upper part of the heat transfer pipe 3a of the heat exchanger 3, and the outlet part of the _CO2 fluid w is connected with the heat transfer pipe 3a of the heat exchanger 3 Lower connection. And, the inlet part of this heat exchanger 3 and this outlet part are connected by the heat transfer pipe 3a arrange|positioned in the up-down direction inside the heat exchanger 3. As shown in FIG. The heat recovery fluid f is supplied to the heat exchanger 3 from the supply pipe 4 connected to the lower part of the heat transfer pipe 3a of the heat exchanger 3, and the heat recovery fluid f undergoes indirect heat exchange with the CO ₂ fluid w from the CO ₂ fluid w. After the heat is recovered, it is discharged from the return pipe 5 connected to the upper part of the heat exchanger 3 .

As shown in FIG. 1 , the CO ₂ fluid w flowing in the heat transfer tube 3a and the heat recovery fluid f flowing around the heat transfer tube 3a flow in opposite directions to each other, so the heat exchange efficiency can be improved. In this way, the heat collecting tube 24 is disposed in the glass tube 25 in a vacuum state, and the CO ₂ fluid w and the heat recovery fluid f are counterflowed by the heat exchanger 3, whereby the high temperature heat recovery fluid f can be recovered.

As described above, in the heat collector 2, the lower collecting pipe 22, the heat collecting pipe 24, and the upper collecting pipe 28 are arranged to be inclined upward toward the downstream side of the flow direction of the _CO fluid w, respectively, and the lower collecting pipe 22 and the upper collecting pipe 28 Since there is a difference in height, the CO ₂ fluid w heated to a supercritical state in the heat collecting pipe 24 generates a lift force and moves toward the outlet side of the heat collecting pipe 24 . The _CO2 fluid w flowing out of the heat collector 2 enters the heat exchanger 3 from the inlet portion arranged on the upper part of the heat exchanger 3 through the flow path 1a, and is connected to the flow path 1b at the outlet portion arranged on the lower part of the heat exchanger 3 . Therefore, the flow path 1a is arranged above the flow path 1b, and the flow path 1a and the flow path 1b have a height difference.

The heat recovery fluid f that has recovered heat from the CO ₂ fluid w flows out from the return pipe 5 and is supplied to various purposes such as hot water supply, heating, and snow melting. On the other hand, the CO ₂ fluid w cooled to below the condensation temperature of the CO 2 fluid w (for example, 15 to 25° C.) by exchanging heat with the heat recovery fluid f is liquefied and flows downward _. The outlet line 1c of the heat exchanger 3 is arranged in the vertical direction, and the head pressure H can be formed by the _CO fluid w that liquefies in the heat transfer tube 3a and accumulates in the lower part of the heat transfer tube 3a and the outlet line 1c. . Due to the formation of liquid head pressure H, the _CO2 fluid w in the closed circuit 1 can form a natural circulation flow along the direction of arrow a. Therefore, the CO ₂ fluid w flowing from the heat exchanger 3 moves towards the heat collector 2 .

A temperature detector 7 for detecting the temperature of the CO ₂ fluid w is provided on the upper header pipe 28 at the outlet of the heat collector 2, and a flow rate adjustment valve 9 is interposed in the flow path 1a. Then, the detection value detected by the temperature detector 7 is input to the controller 6, and the opening degree of the flow rate adjustment valve 9 is adjusted by the controller 6 to adjust the flow rate of the CO ₂ fluid w flowing in the flow path 1a. By adjusting the opening of the flow regulating valve 9, the temperature of the CO ₂ fluid w at the outlet of the heat collector 2 can be controlled, so that the CO ₂ fluid w at the outlet of the heat collector 2 is always in a supercritical state.

It should be noted that instead of the temperature detector 7, an insolation meter 8 may be provided on the heat collector 2, and the insolation amount of the sunlight s irradiated to the heat collector 2 may be measured by the insolation meter 8, and based on the insolation amount Measured value to adjust the opening of the flow regulating valve 9. Alternatively, the temperature difference or pressure difference between the inlet and outlet of the heat collector 2 may be detected, and the amount of heat collected by the heat collector 2 may be calculated based on the difference, and the flow regulating valve 9 may be adjusted based on the calculated value. Alternatively, the pressure of the CO ₂ fluid w at the outlet of the heat collector 2 may be detected, and the flow rate adjustment valve 9 may be adjusted based on the pressure value.

In addition, a temperature detector 11 is provided on the return pipe 5 of the heat recovery fluid to detect the temperature of the flow rate adjustment valve 10 and the heat recovery fluid f, and the detection value of the temperature detector 11 is input to the controller 6, and based on the detection value, The temperature of the heat recovery fluid f flowing in the return pipe 5 can be adjusted by adjusting the flow rate adjustment valve 10 . Thereby, the heat recovery fluid f of desired temperature can be obtained.

In addition, the branch line 12 is provided in parallel with the outlet line 1c on the outlet line 1c, and a storage container 13 for storing part of the CO ₂ fluid w flowing in the outlet line 1c is interposed in the branch line 12. On-off valves 14 and 15 are provided on the inlet side and the outlet side of the storage container 13 .

In order to stabilize the flow of the _CO fluid w in the closed circuit 1, it is necessary to use the heat collector 2 to form the evaporation zone of the CO fluid w, and to use the heat exchanger 3 to form the condensation zone of the _CO fluid w, and it is necessary to transfer _the heat The liquid head pressure H of the _CO2 fluid w formed by the heat transfer tube 3a of the exchanger 3 and the outlet line 1c is kept constant. However, the head pressure H differs due to the difference in the specific gravity of the CO ₂ fluid w due to the difference in temperature between summer and winter. Therefore, as described above, the storage container 13 is interposed in the branch line 12 provided in parallel with the outlet line 1c, and a part of the CO ₂ fluid w is stored in the storage container 13, and heat accumulation can be ensured by adjusting the storage amount. The evaporation area of the device 2 and the condensation area of the heat exchanger 3, and can always adjust the liquid head pressure H to be constant.

In the present embodiment having the above-mentioned structure, when the CO ₂ fluid that evaporates inside the heat collecting tubes 24 and the upper header tube 28 that are arranged obliquely upward and becomes supercritical produces a lifting force, the heat transfer in the heat exchanger 3 Under the action of the liquid head pressure H formed by the pipe 3a and the outlet pipe 1c, the natural circulation of the _CO2 fluid w is carried out in the closed circuit 1. And, the heat of the sunlight s is collected by the heat collector 2 to heat the CO ₂ fluid w, and the heated CO ₂ fluid w is indirectly heat-exchanged with the heat recovery fluid f by the heat exchanger 3 . Thus, the latent heat of the _CO fluid w is recovered by the heat recovery fluid f, and the heat recovered by the heat recovery fluid f is used for various purposes such as hot water supply, heating, or snow melting.

The Mollier diagram (pressure-enthalpy diagram) of the CO ₂ fluid w of this embodiment is shown in FIG. 4 . In FIG. 4 , K is the critical point (pressure 7.3 MPa, temperature 31° C.), and the state becomes supercritical above the critical point. In this embodiment, since the _CO2 fluid w is naturally circulated in the closed circuit 1, there is no pressure fluctuation, and the gasification (supercritical state) in the heat collector 2 and the condensation in the heat exchanger 3 are repeated at the same pressure. Between reciprocating cycle b. The CO contained in the CO ₂ fluid w has no change in viscosity even under high pressure _and high density, but becomes a supercritical state above the critical point (pressure 7.3 MPa, temperature 31°C), and the viscosity decreases in the supercritical state, so the When the CO ₂ fluid w circulates in the closed circuit 1 provided between the heat collector 2 and the heat exchanger 3, natural circulation can be easily formed, and the force required to move the CO ₂ fluid w can be reduced. Furthermore, CO ₂ has the advantage that the higher the pressure, the lower the specific heat, and it is easy to accumulate heat especially at high temperatures.

According to the present embodiment, the heat collecting pipe 24 provided on the heat collecting device 2 is arranged to be inclined upward toward the downstream side of the flow direction of the CO ₂ fluid w, and the upper and lower collecting pipes 22 and 28 are also formed in the same arrangement. The heat transfer tubes 3a of the heat exchanger 3 are arranged vertically, the outlet side of the heat collector 2 is connected to the inlet side of the heat exchanger 3 by the flow path 1a, and the outlet side of the heat exchanger 3 is connected to the inlet side of the heat exchanger 3 by the flow path 1b. The inlet side of the heat collector 2 is connected so that a level difference is provided between the flow path 1a and the flow path 1b.

According to the above-mentioned structure, the CO ₂ fluid w which is in a supercritical state through a phase change (liquid → supercritical state) in the heat collecting tube 24 generates an upward force toward the outlet side of the heat collecting device 2 . This upward force acts to contribute to the formation of natural circulation within the closed circuit 1 .

In addition, the head pressure H of the CO ₂ fluid w can be formed through the heat transfer tube 3 a and the outlet line 1 c connected to the outlet side of the heat transfer tube 3 a. In addition, a natural circulation flow of the CO ₂ fluid w can be formed in the closed circuit 1 by the lifting force generated by the formation of the supercritical state in the outlet-side channel 1 a of the heat collector 2 and the liquid head pressure H. As a result, the circulation of the CO ₂ fluid w does not require pumping power, so the operation of the heat collecting device can be performed at low cost with energy saving.

In addition, a storage container 13 is provided on the branch line 12 arranged in parallel on the outlet line 1c of the heat exchanger 3, and a part of the CO ₂ fluid w is stored in the storage container 13. The circulation of CO _fluid w in loop 1 is stable.

In addition, when using a CO 2 fluid mixed with CO _{2 and} dimethyl ether at 1 to 35 mol% relative to CO ₂ as the CO ₂ fluid w, compared with the case of using only CO ₂ as the CO ₂ fluid, it is possible to improve The boiling point of the _CO2 fluid. Thereby, the condensation temperature range can be raised. Therefore, even if the temperature range of the CO ₂ fluid rises, the CO ₂ fluid is easy to condense and the liquid head pressure H is easily formed, so the natural circulation of the CO ₂ fluid can be reliably performed.

In addition, by mixing dimethyl ether, the pressure of the CO ₂ fluid can be lowered, and the piping system of the CO ₂ fluid can be made into a low-pressure specification to achieve low cost.

In addition, since the temperature detector 7 for detecting the temperature of the CO fluid _w or the insolation meter 8 for measuring the insolation of the heat collector 2 is installed on the upper header 28 at the outlet of the heat collector 2, and the control The controller 6 adjusts the opening degree of the flow rate adjustment valve 9 based on these measured values, and therefore, the temperature of the CO ₂ fluid w on the outlet side of the heat collector 2 can be adjusted to a desired temperature. As a result, the supercritical state of the CO fluid w can be stably formed in the outlet-side channel 1a of the heat collector 2, so natural circulation can be stably formed, and the _heat collection efficiency of the _CO fluid w in the heat collector 2 can be improved.

In addition, since the temperature detector 11 for detecting the temperature of the flow regulating valve 10 and the heat recovery fluid is provided in the return pipe 5, and the opening degree of the flow regulating valve 10 is adjusted by the controller 6 based on the temperature detection value, it is possible to adjust the flow rate according to the application. The temperature of the heat recovery fluid is adjusted to the desired temperature. Therefore, it is possible to obtain a high-temperature heat recovery fluid even in a season when the amount of sunlight is low, such as winter.

[Embodiment 2]

Next, a second embodiment of the present invention will be described based on FIG. 5 . In FIG. 5 , devices or components given the same symbols as those in the first embodiment denote devices or components that are the same as those in the first embodiment, and therefore descriptions thereof will be omitted. In this embodiment, the heat recovery unit 30 that recovers the heat of the CO ₂ fluid w heated by the heat collector 2 does not perform heat exchange with the heat recovery fluid, but directly exchanges heat with the object requiring heat supply. heat exchange. Other structures are the same as those of the above-mentioned first embodiment.

For example, in the heat recovery part 30, the heat transfer tube 31 connected to the closed circuit 1 is arranged in the air-conditioning target space r, and the atmosphere of the air-conditioning target space r is circulated by the fan 32 so that it contacts the heat transfer tube 31, Thus, the space r to be air-conditioned is heated. Alternatively, for other purposes, the heat transfer pipes 31 are buried in places where snow melting is required, such as roads in cold places for snow melting. In this way, in this embodiment, in addition to the effects of the above-mentioned first embodiment, since the _CO fluid w flowing in the heat transfer tube 31 directly exchanges heat with the object to be heated, heat recovery can be improved. efficiency.

[Embodiment 3]

Next, a third embodiment of the present invention will be described based on FIG. 6 . The structure of the heat collecting device of the third embodiment shown in FIG. 6 is the same as that of the first embodiment shown in FIG. 1 . Therefore, in the third embodiment, the same symbols as those in the first embodiment are attached to the same devices or components as in the first embodiment, and descriptions of these same devices or components are omitted.

Hereinafter, in this embodiment, differences from the first embodiment described above will be described. In FIG. 6 , the heat exchanger 3 is used to exchange heat indirectly with the _CO fluid w, and the return pipe 5 of the heat recovery fluid after recovering the heat retained by the _CO fluid w is connected to the storage tank 41 to recover the heat. The received heat recovery flow volume is stored in the storage tank 41. The partition wall of the storage tank 41 is made of a heat insulating material and has heat insulating properties. During the day, the high-temperature heat recovery fluid obtained by the heat collecting device is stored in the storage tank 41 in advance, and the latent heat of the heat recovery fluid f can also be used at night.

In addition, the heat recovery fluid in the storage tank 41 is supplied to the absorption refrigerator 42 . Since the heat recovery fluid f stored in the storage tank 41 has a high recovery temperature, supplying the heat recovery fluid f to the absorption refrigerator 42 can be applied to air conditioning in summer. Furthermore, by using drinking water such as tap water as the heat recovery fluid f stored in the storage tank 41, it can also be applied to hot water supply. In addition, it can also be used for heating in winter, heating of plastic greenhouses, auxiliary heat source for heated swimming pools, and snowmelt countermeasures in cold places. For example, when high-temperature recovery such as hot water supply is desired as the heat exchange method, vacuum insulation by the double-pipe method of the heat collector 2 and counter-flow heat exchange by the heat exchanger 3 are preferable as described above.

In this manner, according to the present embodiment, in addition to the effects of the first embodiment described above, the effects described above can be obtained.

[Example]

Next, an example at the time of actually implementing the above-mentioned first embodiment of the present invention will be described based on FIGS. 7 and 8 . Fig. 7 shows the operating conditions of this example, and Fig. 8 shows the obtained experimental data. It should be noted that this embodiment represents the average value of experiments conducted on sunny days in winter (January to March), and water is used as the heat recovery fluid f in the heat exchanger 3 . It can be seen from Fig. 8 that a high heat accumulation rate and recovery rate of more than 80% can be obtained.

In addition, when using _CO2 fluid which mixed dimethyl ether with _CO2 as _CO2 fluid, compared with the case of using only _CO2 , since the condensation temperature can be raised, it becomes easy to form a liquid head pressure. Furthermore, the heat recovery rate when using water as the CO ₂ fluid is 60%, but as the CO ₂ fluid, when using the CO ₂ fluid obtained by mixing CO ₂ and dimethyl ether, a high heat recovery rate of 80% or more can be obtained. heat recovery rate.

FIG. 9 shows experimental data performed on a sunny day in winter (February). This is data obtained by measuring the amount of accumulated heat and solar radiation in the heat collector 2 (per 1.5 m 2 ) when a CO ₂ fluid obtained by mixing 10 mol % of dimethyl ether in CO ₂ is used as the CO ₂ fluid. The experiment was started after 10 o'clock in the morning, and the experiment was carried out at an outside air temperature of 8 to 16°C. It can be seen from FIG. 9 that a high heat concentration was obtained with respect to the amount of sunlight.

【Industrial Applicability】

According to the present invention, a closed circuit in which a working fluid with _CO2 as the main fluid circulates is formed, and by allowing the _CO2 fluid to naturally circulate in the closed circuit, it is possible to realize solar energy that does not require power, is low-cost, and has a high heat-gathering capacity. heat-gathering method.

Claims (11)

1. the heat build-up method of a solar energy arranges solar energy collectors and heat exchanger by intervention, and these solar energy collectors are formed with CO ₂For the working fluid of main fluid is CO ₂The loop circuit that fluid circulated, and in this loop circuit solar energy is carried out heat build-up, this heat exchanger possesses for CO ₂The heat-transfer pipe of Fluid Flow in A, thus with the solar energy heat build-up in the CO that in this loop circuit, circulates ₂In the fluid, and by heat exchanger to this CO ₂The heat of fluid carries out recuperation of heat, it is characterized in that,

Described loop circuit is not get involved to arrange to follow CO ₂The loop circuit of the forced circulation means of the physical property of the compression of fluid or lift effect,

Ejection side low mode arranges difference of height to the heat-transfer pipe that intervention is installed on the heat exchanger of this loop circuit so that the suction side of working fluid is high, and at the CO of this heat-transfer pipe ₂The ejection side of fluid forms the liquid head and presses,

With the CO that flows at least this heat accumulating pipe in the heat accumulating pipe that is arranged on the described solar energy collectors ₂The heating of liquid begins and the liquid phase part that is varied to till the supercriticality is configured to towards CO ₂The flow direction downstream of fluid and being inclined upwardly, the boundary portion of liquid phase part and supercriticality is overcritical interface, and, utilize the solar energy heat build-up of described solar energy collectors to be heated into the CO that makes in this heat collector ₂The overcritical interface of fluid is positioned at the heat accumulating pipe of this heat collector, makes the CO of this heat collector outlet side ₂Fluid forms supercriticality, thereby forms CO in this loop circuit ₂The Natural Circulation of fluid.

2. the heat build-up method of solar energy according to claim 1 is characterized in that,

Based on the CO that detects in the described heat collector ₂Whether fluid has the detected value of the detector of supercriticality, by being arranged on the switching adjustment of the flow rate regulating valve on the described loop circuit, utilizes the solar energy heat build-up of described solar energy collectors to be heated into the CO that makes in this heat collector ₂The overcritical interface of fluid is positioned at the heat accumulating pipe of this heat collector, and makes the CO of this heat collector outlet side ₂Fluid forms supercriticality.

3. the heat build-up method of solar energy according to claim 1 is characterized in that,

Detect the CO in the described heat collector ₂The detector whether fluid has a supercriticality be detect described heat collector the heat build-up amount detector or detect the CO that in the loop circuit of this heat collector outlet side, flows ₂The temperature of fluid or the detector of pressure.

4. the heat build-up method of solar energy according to claim 1 is characterized in that,

Described CO ₂Fluid uses CO ₂With with respect to CO ₂It is 1～35 % by mole the mixed fluid of dimethyl ether.

5. the heat build-up method of solar energy according to claim 1 is characterized in that,

Described CO ₂Fluid uses CO ₂With with respect to CO ₂Be 1～35 % by mole the mixed fluid of hydrocarbon system natural refrigerant, described hydrocarbon system natural refrigerant is made of iso-butane, propane or ethane.

6. the Accumulated Heat Units of a solar energy is got involved and is provided with solar energy collectors and heat exchanger, and these solar energy collectors are formed with CO ₂For the working fluid of main fluid is CO ₂The loop circuit that fluid circulated, and in this loop circuit by the solar energy heat build-up to CO ₂Fluid heats, and this heat exchanger possesses for CO ₂The heat-transfer pipe of Fluid Flow in A, thus with the solar energy heat build-up in the CO that in this loop circuit, circulates ₂In the fluid, and by heat exchanger to this CO ₂The heat of fluid carries out recuperation of heat, it is characterized in that,

Described loop circuit is not get involved to arrange to follow CO ₂The loop circuit of the forced circulation means of the physical property of the compression of fluid or lift effect,

The low mode of ejection side arranges difference of height to the heat-transfer pipe that intervention is installed on the heat exchanger of this loop circuit so that the suction side of working fluid is high, and forms liquid head pressure in the heat-transfer pipe ejection side of this heat exchanger,

With the CO that flows at least this heat accumulating pipe in the heat accumulating pipe that is arranged on the described solar energy collectors ₂The heating of liquid begins and the liquid phase part that is varied to till the supercriticality is configured to towards CO ₂The flow direction downstream of fluid and being inclined upwardly, the boundary portion of liquid phase part and supercriticality is overcritical interface,

The Accumulated Heat Units of described solar energy possesses: detect the CO in this heat collector ₂Whether fluid has the detector of supercriticality; Be arranged on the described loop circuit and control CO in the described heat accumulating pipe ₂The flow rate regulating valve of Fluid Volume; Based on the detected value of this detector and described flow rate regulating valve is carried out the controller of open and close controlling,

This controller is by described flow rate regulating valve being opened and closed adjustment, utilizing the solar energy heat build-up described solar energy collectors to be heated into the CO that makes in the described solar energy collectors ₂The overcritical interface of fluid is positioned at the heat accumulating pipe of this heat collector, and makes the CO of this heat collector outlet side ₂Fluid forms the controller of supercriticality.

7. the Accumulated Heat Units of solar energy according to claim 6 is characterized in that,

With at least CO in the heat accumulating pipe that is arranged on the described heat collector ₂The heating of fluid begins and the partial configuration that is varied to till the supercriticality becomes towards CO ₂The flow direction downstream of fluid and being inclined upwardly, thus make CO ₂Fluid flows out from the bottom inflow of this heat collector and from top,

In described heat exchanger, will be configured to towards CO with the heat-transfer pipe that described loop circuit is connected ₂The flow direction downstream of fluid and downward-sloping, thus make CO ₂Fluid flows into from the top of this heat exchanger and flows out from the bottom.

8. the Accumulated Heat Units of solar energy according to claim 7 is characterized in that,

It is height level more than the sustained height that the liquid head voltage levels of described heat exchanger becomes at gravity direction with respect to the overcritical interface configurations of described heat collector.

9. the Accumulated Heat Units of solar energy according to claim 6 is characterized in that, possesses:

The CO that detection flows into or flows out from this heat exchanger to described heat exchanger ₂The temperature of fluid, or detection is from the detector of the temperature of the heat recovery fluid of this heat exchanger outflow;

Make the discrepancy pipe arrangement that heat recovery fluid circulates and be arranged on flow rate regulating valve on this discrepancy pipe arrangement in this heat exchanger;

Based on the temperature detection value of this detector and regulate the controller of the aperture of this flow rate regulating valve.

10. the Accumulated Heat Units of solar energy according to claim 6 is characterized in that,

Described loop circuit in the export department of described heat exchanger is provided with branch line side by side, is provided with the CO that has liquefied via open and close valve at this branch line ₂Fluid accumulate container,

Accumulate in this by adjusting and accumulate CO in the container ₂Fluid Volume and can regulate CO ₂The liquid head of fluid is pressed.

11. the Accumulated Heat Units of each described solar energy is characterized in that according to claim 6～8,

In described heat collector, for CO ₂The heat accumulating pipe of Fluid Flow in A is configured in the inside of vacuum tank.

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