CN110779951B - Experimental system for supercritical water and carbon dioxide mixed working medium heat transfer - Google Patents
Experimental system for supercritical water and carbon dioxide mixed working medium heat transfer Download PDFInfo
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Abstract
The invention discloses an experimental system for supercritical water and carbon dioxide mixed working medium heat transfer, wherein a water supply unit comprises a water storage tank and a first control assembly communicated with the water storage tank; the carbon dioxide supply unit comprises a carbon dioxide liquefaction feeding assembly and a second control assembly communicated with the carbon dioxide liquefaction feeding assembly; the system comprises a preheating mixing unit, a cooling unit, a pressure control discharge unit and an electric pressure regulating valve and a pneumatic back pressure valve which are sequentially communicated. The invention can avoid the problem of cross flow of current without adopting a one-way diode to isolate each heating module, improves the reliability and the economy, does not have the problems of carbon dioxide gasification and ice blockage, and saves energy.
Description
Technical Field
The invention belongs to the technical field of supercritical mixed working media, and particularly relates to a supercritical water and carbon dioxide mixed working medium heat transfer experimental system.
Background
The supercritical working medium has good application prospect in the field of multi-energy hybrid power generation. In the existing measurement and research of the heat transfer characteristics of supercritical working media, pure working media are mainly used. The heat transfer characteristics of the supercritical water and carbon dioxide mixed working medium are not measured. The invention provides a system and a method for researching the heat transfer characteristics of a supercritical water and carbon dioxide mixed working medium, which are urgently needed for developing a novel thermal power generation poly-generation technology. The measurement of the mixed working medium needs to ensure that the two working media, namely water and carbon dioxide, have large difference in thermal physical properties, the working media with far-spaced critical points reach the critical points and are fully mixed, and the stability of parameters such as pressure, temperature, flow and the like needs to be ensured in the process. At present, in supercritical pure working media, a supercritical carbon dioxide system is taken as an example, a closed circulation system is mostly adopted, and due to the problems of pipeline resistance and pump head heating, most of metering pump intakes gaseous carbon dioxide, the flow cannot be accurately controlled, and the stability is poor. Moreover, for example, in the closed circulation system of chinese patent (CN106066235A), since the solubility of carbon dioxide in water is low, after the water and carbon dioxide are cooled by the condenser, the two working fluids are separated, so the concentration of the components after circulation cannot be guaranteed. If an open system such as that of japanese patent (JP2003245679A) is used, the carbon dioxide rapidly decreases at the outlet of the back pressure valve, which causes the ice blockage phenomenon and the cavitation problem due to the heat absorption of the gasification, and the pressure stability accuracy is insufficient, resulting in high replacement and maintenance costs. In the cooling stage, the heat exchanger is mostly adopted in industry to carry out two-in-one liquefaction and supercooling, but the temperature of the required refrigerant is too low, about-40 to-60 ℃, which is very energy-consuming. In the supercritical mixed working medium flowing heat exchange characteristic experiment, because parameters such as flow, pressure, component concentration, temperature and the like are coupled, the instability or change of one parameter can influence other parameters and the whole state. The existing experiment table is not designed by adopting modularized automatic control, has high operation difficulty and long operation time, consumes manpower and material resources and is difficult to reach a steady-state condition.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
The present invention has been made in view of the above-mentioned technical drawbacks.
Therefore, as one aspect of the invention, the invention overcomes the defects in the prior art and provides an experimental system for heat transfer of a supercritical water and carbon dioxide mixed working medium.
In order to solve the technical problems, the invention provides the following technical scheme: an experimental system for supercritical water and carbon dioxide mixed working medium heat transfer comprises,
the water supply unit comprises a water storage tank and a first control assembly communicated with the water storage tank;
the carbon dioxide supply unit comprises a carbon dioxide liquefaction feeding assembly and a second control assembly communicated with the carbon dioxide liquefaction feeding assembly;
the preheating and mixing unit comprises a first preheating component for supplying heat to the working medium in the water supply unit, a second preheating component for supplying heat to the working medium in the carbon dioxide supply unit, a mixing cavity and a third preheating component for supplying heat to the working medium mixed by the mixing cavity; the mixing cavity is respectively communicated with the water supply unit and the carbon dioxide supply unit; the test assembly is communicated with the preheating and mixing unit.
And the test unit is communicated with the preheating mixing unit, consists of a test component and is used for measuring data such as temperature, pressure, differential pressure, heat flux density and the like in an experiment.
A cooling unit comprising a double pipe condenser, in communication with the test unit;
and the pressure control discharge unit is communicated with the cooling unit and comprises an electric pressure regulating valve and a pneumatic back pressure valve which are sequentially communicated.
The first control assembly, the second control assembly, the preheating mixing unit and the pressure control discharge unit control the working medium water and the working medium carbon dioxide to be in a supercritical state;
as a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the first control assembly comprises a water storage tank outlet valve, a filter, a first high-pressure metering pump, a first pump outlet valve, a first mass flow meter and a water supply back pressure valve which are sequentially communicated with the water storage tank.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the carbon dioxide liquefaction feed assembly comprises a carbon dioxide gas cylinder, a third control assembly, a carbon dioxide liquefaction feed tank body and a refrigerant for cooling carbon dioxide liquefaction, wherein the carbon dioxide gas cylinder, the third control assembly and the carbon dioxide liquefaction feed tank body are sequentially communicated; the third control component controls the carbon dioxide to be introduced into the carbon dioxide liquefaction feed tank body from the carbon dioxide gas cylinder.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the carbon dioxide liquefaction feed tank body comprises a refrigerant inlet arranged at the bottom of the carbon dioxide liquefaction feed tank body, a cooling coil arranged in the carbon dioxide liquefaction feed tank body and communicated with the refrigerant inlet, a refrigerant outlet arranged on the side wall of the carbon dioxide liquefaction feed tank body and communicated with the cooling coil, and a carbon dioxide inlet and a saturated carbon dioxide outlet arranged on the side wall of the carbon dioxide liquefaction feed tank body.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the second control component comprises a second high-pressure metering pump, a second pump outlet valve, a second mass flow meter and a second back pressure valve which are sequentially communicated;
the refrigerant is respectively communicated with the refrigerant inlet, the refrigerant fine-tuning valve and the temperature control valve of the carbon dioxide liquefaction feed tank body through the refrigerant inlet valve, and the refrigerant fine-tuning valve and the temperature control valve of the carbon dioxide liquefaction feed tank body jointly control the refrigerant to supply cold for the carbon dioxide liquefaction feed tank body and liquefied carbon dioxide in the second control assembly.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the carbon dioxide is liquefied and cooled and is divided into a liquefied storage stage and a cryogenic feeding stage; in the liquefaction storage stage, the refrigerant mainly supplies cold for the carbon dioxide liquefaction feeding tank body; and in the cryogenic feeding stage, the refrigerant mainly supplies cold for the second control assembly.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the preheating and mixing unit is characterized in that each preheating assembly of the preheating and mixing unit outputs energy through one direct current power supply, each preheating assembly comprises at least four conductive plates, the conductive plates are sequentially connected with a negative pole, a positive pole and a negative pole of the power supply, and the negative pole is all grounded.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the preheating and mixing unit also comprises a temperature thermocouple for controlling the heating temperature.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the first pump outlet valve comprises a first pump outlet discharge needle valve and a first pump outlet ball valve; the second pump outlet valve comprises a second pump outlet ball valve; the water supply unit and the carbon dioxide supply unit both comprise a safety valve and a pulsation damper.
As a preferred scheme of the supercritical water and carbon dioxide mixed working medium heat transfer experimental system provided by the invention: the heat transfer system is an open system, and the mixed working medium passes through the pressure control discharge unit and then passes through the separation tank to separate water from carbon dioxide and then is discharged.
The invention has the beneficial effects that: when the working medium passes through the pneumatic back pressure valve, water does not generate phase change, ice blockage does not exist, the working environment of the regulating valve is improved, the inlet of the pneumatic back pressure valve is 15MPa, and the outlet of the pneumatic back pressure valve is atmospheric pressure. Compared with the arrangement of a single regulating valve, the pressure difference is reduced by 40%, the flow cross section of the valve is improved by 30%, and the ice blockage phenomenon is effectively avoided. Through calculation, the mass ratio of the carbon dioxide in the mixed working medium can be increased to 50%, and in the cryogenic feeding stage, the flow of the liquid carbon dioxide is stable and gasification cannot occur. The invention divides the carbon dioxide liquefaction and cooling into a liquefaction storage stage and a cryogenic feeding stage, saves energy, the refrigerant can maintain the liquefaction and cooling of the carbon dioxide only at minus 7 to minus 10 ℃, adopts direct current to improve the heating speed and adjust the response speed, has small heat loss, does not generate local tube wall overheating caused by alternating current skin effect to cause tube explosion, and does not cause influence on other electric equipment including temperature control arrangement by electromagnetic interference generated by alternating current heating; insulation gaskets are not needed to be adopted for insulation under the conditions of high temperature and high pressure and containing supercritical working media, so that the reliability and the safety of the sealing performance of the system are ensured; meanwhile, a joint and a heating module can be added according to needs, and the heated current cannot flow through the joint or a welding seam, so that tube explosion caused by overheating can be avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:
FIG. 1 is an overall view of an experimental system for heat transfer of a supercritical water and carbon dioxide mixed working medium.
FIG. 2 is a diagram of a carbon dioxide liquefaction feed assembly of the present invention.
FIG. 3 is a diagram of a carbon dioxide liquefaction feed tank of the present invention.
Fig. 4 is a current flow diagram of the preheat assembly of the present invention.
FIG. 5 is a graph illustrating stability testing of the heat transfer system of the present invention.
FIG. 6 is a stability test chart of a prior art heat transfer system.
FIG. 7 is a stability test chart of the heat transfer system of the present invention under a supercritical state.
FIG. 8 is a diagram of the temperature difference between the inlet and outlet of the heat transfer system of the present invention.
FIG. 9 is a graph illustrating carbon dioxide flow stability testing of a heat transfer system according to the present invention.
FIG. 10 is a graph of carbon dioxide flow stability testing for a prior art heat transfer system.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with examples are described in detail below.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Example 1:
as an embodiment of the experiment system for the supercritical water and carbon dioxide mixed working medium heat transfer, as shown in FIGS. 1 to 3, a water supply unit 100 includes a water storage tank 101 and a first control assembly 102 communicated with the water storage tank; the carbon dioxide supply unit 200 comprises a carbon dioxide liquefaction feed assembly 201 and a second control assembly 202 communicated therewith; the preheating and mixing unit 300 comprises a first preheating assembly 301 for supplying heat to the working medium in the water supply unit 100, a second preheating assembly 302 for supplying heat to the working medium in the carbon dioxide supply unit 200, a mixing cavity 303, and a third preheating assembly 304 for supplying heat to the working medium mixed by the mixing cavity 303; the mixing cavity 303 is respectively communicated with the water supply unit 100 and the carbon dioxide supply unit 200; the first control assembly 102, the second control assembly 202 and the preheating mixing unit 300 control the working medium water and the working medium carbon dioxide to be in a supercritical state; a cooling unit 400 including a double pipe condenser 401, which is communicated with the preheating mixing unit 300; and a pressure control discharge unit 500, which is communicated with the cooling unit 400, and comprises an electric pressure regulating valve 501 and a pneumatic back pressure valve 502 which are communicated in sequence. Preferably, the water supply unit 100 and the carbon dioxide supply unit 200 each include a pulsation damper.
Specifically, after the working fluid in the water supply unit 100 flows through the water supply unit 100 and the flow and water pressure of the working fluid are controlled by the first control assembly 102, the working fluid in the carbon dioxide unit 200 is preheated by the first preheating assembly 301, the working fluid in the carbon dioxide unit 200 flows through the carbon dioxide unit 200 and the flow and pressure of the liquid carbon dioxide are controlled by the second control assembly 202, then the liquid carbon dioxide is preheated by the second preheating assembly 302, then the liquid carbon dioxide is mixed in the mixing cavity 303, and then the mixed working fluid is further heated by the third preheating assembly 304, the mixed working fluid can be used for supplying a steam turbine to do work and the like, and then the mixed working fluid is cooled by the cooling unit 400 and discharged by the pressure control discharge unit 500;
the existing system adopts a single regulating valve, carbon dioxide directly reduces the atmospheric pressure from the high pressure of 25MPa in a supercritical state, the service life is short due to too large pressure difference of an inlet and an outlet of the valve, the carbon dioxide can generate severe gasification phenomenon, the carbon dioxide gasification absorbs heat to cause water phase change to form small ice slag, so that the pipeline is blocked, danger is easily caused, the higher the carbon dioxide content is, the more serious the ice blocking phenomenon is, therefore, the content of the carbon dioxide in a mixed working medium of water and the carbon dioxide is not allowed to be adjusted to be higher, and generally, the content of the carbon dioxide in the mixed working medium is not more than 25%.
The pressure control discharge unit 500 of the invention adopts the combination of the electric regulating valve and the pneumatic back pressure valve 502 to carry out the step control regulation of the pressure, the pressure is stable, the control precision is high, the pressure is still above the critical pressure of the carbon dioxide after the electric regulating valve, the cavitation and ice blockage phenomena of the carbon dioxide can not be generated at the position, the working condition of the electric regulating valve is optimized, and the stability of the pressure control of the device system is improved. The electric regulating valve and the pneumatic back pressure valve 502 are matched for use, preferably, the pressure before the electric regulating valve is regulated to be about 24MPa, and the pressure after the electric regulating valve is regulated to be about 15MPa by the pneumatic back pressure valve 502. Compared with the arrangement of a single regulating valve, the pressure difference is reduced by 40%, the flow cross section of the valve is improved by 30%, the ice blockage phenomenon is effectively avoided, and the mass percentage of carbon dioxide in the mixed working medium can be improved to 50% through calculation.
The heat transfer system is an open system, and mixed working medium passes through the pressure control discharge unit 500, and then is discharged after water and carbon dioxide are separated through the separation tank 503.
As a preferred embodiment, the first control assembly 102 includes a water storage tank outlet valve 102a, a filter 102b, a first high pressure metering pump 102c, a first pump outlet valve 102d, a first mass flow meter 102e, a water supply back pressure valve 102f, which are sequentially communicated with the water storage tank 101; preferably, the first pump outlet valve 102d comprises a first pump outlet discharge needle valve 102d-1 and a first pump outlet ball valve 102d-2, when in use, the water storage tank outlet valve 102a and the first pump outlet discharge needle valve 102d-1 are opened first, after water slowly and stably flows out, the first pump outlet discharge needle valve 102d-1 is closed, the first pump outlet ball valve 102d-2 is opened, the first high-pressure metering pump 102c and the first mass flow meter 102e are opened, the back pressure 102f of the water supply valve is adjusted, and the control water pressure is about 28 MPa.
As shown in fig. 5, which is a stability test chart of the heat transfer system of the present invention, since there is no ice blockage problem, the stability of the whole system is greatly improved, and the pressure is very stable in about 6 hours of the test, especially in the supercritical time period, there is hardly any fluctuation in the pressure. By way of obvious comparison, as shown in fig. 6, for the experimental result of the prior art that the pressure is unstable by using a single regulating valve, it is obvious that the pressure is out of control and varies violently, and the risk factor is very high. FIG. 7 is a stability test chart of the present invention in a supercritical state, and it can be seen that the temperature changes by only + -0.4 ℃ and the pressure changes by only + -0.02 MPa within 10 minutes, and the system stability is very good.
Fig. 8 is a diagram of the temperature difference at the outlet of the system of the present invention, which is used to show whether the mixing of the working medium in the mixing chamber 303 of the present invention is sufficient, and it can be seen from the diagram that the temperature difference at the inlet and the outlet of the heat transfer system of the present invention has an average value of 21.344 ℃ and a root mean square deviation of 0.57%, and it can be seen that the temperature difference at the inlet and the outlet does not change with the time change under the same heating power, and the temperature difference at the inlet and the outlet cannot be so stable if the mixing of the working medium of water and carbon dioxide is not uniform, because the specific heat capacity of water and carbon dioxide is very different. Therefore, the experimental result can reflect that the water and the carbon dioxide working medium are mixed very uniformly by adopting the heat transfer system.
Example 2:
the difference between the embodiment and embodiment 1 is that, as shown in fig. 1 to 4, the carbon dioxide liquefaction feed assembly 201 includes a carbon dioxide gas cylinder 201a, a third control assembly 201b, a carbon dioxide liquefaction feed tank 201c, and a refrigerant for liquefying and cooling carbon dioxide, which are sequentially communicated with each other; the third control component 201b controls the passage of carbon dioxide from the carbon dioxide cylinder 201a into the carbon dioxide liquid feed tank 201 c.
Preferably, as shown in fig. 3, the carbon dioxide liquefaction feed tank 201c includes a refrigerant inlet 201c-1 disposed at the bottom of the carbon dioxide liquefaction feed tank 201c, a cooling coil 201c-2 disposed inside the carbon dioxide liquefaction feed tank 201c and communicated with the refrigerant inlet 201c-1, a refrigerant outlet 201c-3 disposed on a side wall of the carbon dioxide liquefaction feed tank 201c and communicated with the cooling coil 201c-2, and a carbon dioxide inlet 201c-4 and a saturated carbon dioxide outlet 201c-5 disposed on a side wall of the carbon dioxide liquefaction feed tank 201 c. The cooling coil 201c-2 is communicated with an interlayer on the side wall of the carbon dioxide liquefaction feed tank body 201c, and a refrigerant enters the interlayer on the side wall of the cooling coil 201c-2 and the carbon dioxide liquefaction feed tank body 201c from the refrigerant inlet 201c-1, flows in the interlayer, and finally flows out from the refrigerant outlet 201 c-3.
Preferably, the second control assembly 202 comprises a second high-pressure metering pump 202a, a second pump outlet valve 202b, a second mass flow meter 202c and a second backpressure valve 202d which are communicated in sequence; the refrigerant is respectively communicated with the refrigerant inlet 201c-1, the refrigerant fine-tuning valve 202f and the carbon dioxide liquefaction feed tank body temperature control valve 202g through a refrigerant inlet valve 202e, and the refrigerant fine-tuning valve 202f and the carbon dioxide liquefaction feed tank body temperature control valve 202g jointly control the refrigerant to supply cold for the carbon dioxide liquefaction feed tank body 201c and the liquefied carbon dioxide in the second control assembly 202. The second pump outlet valve 202b comprises a second pump outlet ball valve.
At present, heat exchangers are mostly adopted for cooling liquefied carbon dioxide in industry, but the temperature of required refrigerants is too low, about minus 40 to minus 60 ℃, and energy is consumed. And after small-size closed circulation system becomes saturated attitude with the carbon dioxide liquefaction, just squeeze into back-end system with the measuring pump, because pipeline resistance and generate heat, the inspiratory most of measuring pump is gaseous carbon dioxide, and the flow can't accurate control, and stability is very poor. Therefore, the invention divides the carbon dioxide liquefaction and cooling into a liquefaction storage stage and a cryogenic feeding stage; in the liquefaction storage stage, the refrigerant mainly supplies cold for the carbon dioxide liquefaction feed tank 201 c; at this time, the temperature of the carbon dioxide liquefaction feed tank body 201c is set to be-5 ℃, the temperature control valve 202g of the carbon dioxide liquefaction feed tank body automatically controls the opening degree of the valve, and meanwhile, the refrigerant fine-tuning valve 202f is adjusted, so that 90% -95% of refrigerant enters the carbon dioxide liquefaction feed tank body 201c from the refrigerant inlet 201c-1, carbon dioxide is liquefied into a saturated state in the carbon dioxide liquefaction feed tank body 201c, and the remaining 5% -10% of refrigerant supplies cold for liquefied carbon dioxide in the second control assembly 202 through the refrigerant fine-tuning valve 202 f; in the cryogenic feed stage, since the liquefied carbon dioxide in the carbon dioxide liquefied feed tank 201c is liquefied to a saturated state by the liquefied reserve stage, the main purpose of the cryogenic feed stage is to provide cooling for the liquefied carbon dioxide in the second control module 202. At this time, the temperature of the carbon dioxide liquefaction feed tank 201c is set to 0 to 2 ℃, the temperature control valve 202g of the carbon dioxide liquefaction feed tank automatically controls the valve opening degree thereof, the refrigerant in the carbon dioxide liquefaction feed tank 201c only needs to maintain the cooling capacity dissipated to the external environment, and the refrigerant fine adjustment valve 202f is opened at the same time, so that a large amount of refrigerant passes through the refrigerant fine adjustment valve 202f, and the liquefied carbon dioxide in the second control assembly 202 is cooled. Preferably, the coolant is ethylene glycol. The cooling mode of the invention ensures that the refrigerant can maintain the liquefaction and cooling of the carbon dioxide only at minus 7 to minus 10 ℃, thereby greatly saving energy, and simultaneously, the invention also solves the problem that the liquid carbon dioxide is gasified due to the heating of the second control component 202.
As shown in fig. 9, which is a graph of the carbon dioxide flow stability of the heat transfer system of the present invention, each point represents the average of the carbon dioxide flow rate every five minutes. It can be seen that the average flow rate of carbon dioxide is 3.99kg/h and the root mean square deviation of the flow rate is 2.2% in 70 minutes, which indicates that the flow rate of carbon dioxide in the system of the present invention is very stable and no gasification occurs. In contrast, as shown in fig. 10, which is a graph showing the stability of the flow rate of carbon dioxide using the conventional system, it can be seen that the flow rate of carbon dioxide is very unstable. The carbon dioxide is gasified in the pump cavity, so that the flow is insufficient, the rotating speed of a motor of the pump must be increased to ensure a certain flow, the rotating speed cannot be increased continuously until the rotating speed reaches 100%, the heat and the gasification are more and more serious, and finally the flow is reduced, so that the continuous normal operation cannot be realized.
Example 3:
as an embodiment of the experiment system for heat transfer of the supercritical water and carbon dioxide mixed working medium of the present invention, as shown in fig. 4, each preheating assembly of the preheating mixing unit 300 of the present invention is powered by a dc power supply 306, each preheating assembly includes at least four conductive plates, the conductive plates are sequentially connected to a negative electrode, a positive electrode, and a negative electrode of the power supply, and the negative electrode is grounded. Preferably, the preheating and mixing unit 300 further includes a temperature thermocouple 305 to control the heating temperature.
Preferably, the first preheating assembly 301 is divided into two sections to heat the working medium water, the first section is heated to 350 ℃, the second section is heated to 400 ℃, and the second preheating assembly 302 is used for heating the working medium carbon dioxide to 400 ℃; the third preheating assembly 304 heats the mixed working medium to 400-600 ℃.
The traditional supercritical heating method is to directly use alternating current to heat in two points, has great problems, can not avoid welding seams, also needs a high-temperature and high-voltage insulating gasket, and can not reduce the circuit voltage (along with the increase of the length of a pipe, the voltage also needs to be increased) and exceeds the safe voltage. In addition, the use of alternating current can also affect other electric equipment, forming electromagnetic interference. The contact resistance is larger than the conventional resistance of the pipeline, and when the pipeline is electrified and heated, the heat is more serious at the position because of ohm's law, and the pipeline is very dangerous when being subjected to higher-temperature experimental operation or higher-power experimental operation. The four-point heating mode of four conducting plates is adopted, each preheating assembly outputs energy through one direct current power supply 306, the welding seam can be avoided, the voltage is controlled within safe voltage, the heating is safer, meanwhile, the negative electrode is grounded, all the negative electrodes are 0 potential, so potential can be effectively isolated among modules, modules and other equipment, the four conducting plates of each preheating assembly output energy through one direct current power supply 306, the potentials between the positive electrode and the positive electrode are equal, the welding seam, a connector and the like can be added between the two positive conducting plates, current cannot pass through the four conducting plates, and the heating caused by overlarge contact resistance at the position is effectively avoided. Preferably, a temperature thermocouple 305 is arranged at the outlet of each preheating assembly, the temperature of the outlet of each preheating assembly is accurately controlled in a negative feedback regulation mode, and low-voltage large current is adopted for direct current. Due to the fact that direct current is adopted, heating speed is improved, response speed is adjusted, heat loss is small, tube explosion caused by local tube wall overheating due to the alternating current skin effect is avoided, and influence on other electric equipment including temperature control setting due to electromagnetic interference generated by alternating current heating is avoided.
By adopting the heating mode of the invention, the problem of cross flow of current can be avoided without adopting a one-way diode to isolate each heating module, and the reliability and the economy are improved; and an insulating gasket is not needed to be adopted for insulation under the conditions of high temperature and high pressure and containing supercritical working media, so that the reliability and the safety of the sealing performance of the system are ensured.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (6)
1. The utility model provides an experimental system that supercritical water and carbon dioxide mixed working medium heat transfer which characterized in that: comprises the steps of (a) preparing a mixture of a plurality of raw materials,
the water supply unit (100) comprises a water storage tank (101) and a first control assembly (102) communicated with the water storage tank;
a carbon dioxide supply unit (200) comprising a carbon dioxide liquefaction feed assembly (201) and a second control assembly (202) in communication therewith;
the preheating and mixing unit (300) comprises a first preheating assembly (301) for supplying heat to the working medium in the water supply unit (100), a second preheating assembly (302) for supplying heat to the working medium in the carbon dioxide supply unit (200), a mixing cavity (303), and a third preheating assembly (304) for supplying heat to the working medium mixed by the mixing cavity (303); the mixing cavity (303) is respectively communicated with the water supply unit (100) and the carbon dioxide supply unit (200); the first control assembly (102), the second control assembly (202) and the preheating mixing unit (300) control the working medium water and the working medium carbon dioxide to be in a supercritical state;
a cooling unit (400) comprising a double pipe condenser (401) in communication with the pre-heating mixing unit (300);
the pressure control discharge unit (500) is communicated with the cooling unit (400) and comprises an electric pressure regulating valve (501) and a pneumatic back pressure valve (502) which are sequentially communicated;
each preheating assembly of the preheating mixing unit (300) is output energy by a direct current power supply (306), each preheating assembly comprises at least four conductive plates, the conductive plates are sequentially connected with a negative electrode, a positive electrode and a negative electrode of the power supply (306), and the negative electrodes are all grounded;
the carbon dioxide liquefaction feeding assembly (201) comprises a carbon dioxide gas cylinder (201a), a third control assembly (201b), a carbon dioxide liquefaction feeding tank body (201c) and a refrigerant for carbon dioxide liquefaction and cooling, wherein the carbon dioxide gas cylinder (201a), the third control assembly (201b) and the carbon dioxide liquefaction feeding tank body (201c) are sequentially communicated; the third control assembly (201b) controls the passage of carbon dioxide from the carbon dioxide gas cylinder (201a) into the carbon dioxide liquid feed tank (201 c);
the second control assembly (202) comprises a second high-pressure metering pump (202a), a second pump outlet valve (202b), a second mass flow meter (202c) and a second backpressure valve (202d) which are communicated in sequence; the refrigerant is respectively communicated with the refrigerant inlet (201c-1), the refrigerant fine-tuning valve (202f) and the carbon dioxide liquefaction feeding tank body temperature control valve (202g) through a refrigerant inlet valve (202e), and the refrigerant fine-tuning valve (202f) and the carbon dioxide liquefaction feeding tank body temperature control valve (202g) jointly control the refrigerant to supply cold for the carbon dioxide liquefaction feeding tank body (201c) and liquefied carbon dioxide in the second control assembly (202);
the carbon dioxide is liquefied and cooled and is divided into a liquefied storage stage and a cryogenic feeding stage; in the liquefaction storage stage, the refrigerant mainly supplies cold for the carbon dioxide liquefaction feeding tank body (201 c); and in the cryogenic feeding stage, the refrigerant mainly supplies cold for the second control assembly (202).
2. The supercritical water and carbon dioxide mixed working medium heat transfer experimental system of claim 1, characterized in that: the first control assembly (102) comprises a water storage tank outlet valve (102a), a filter (102b), a first high-pressure metering pump (102c), a first pump outlet valve (102d), a first mass flow meter (102e) and a water supply back pressure valve (102f), wherein the water storage tank outlet valve (102a), the filter (102b), the first high-pressure metering pump (102c), the first pump outlet valve (102d), the first mass flow meter (102e) and the water supply back pressure valve (102f) are sequentially communicated with the water storage tank (101).
3. The supercritical water and carbon dioxide mixed working medium heat transfer experimental system of claim 2, characterized in that: the carbon dioxide liquefaction feed tank body (201c) comprises a refrigerant inlet (201c-1) arranged at the bottom of the carbon dioxide liquefaction feed tank body (201c), a cooling coil (201c-2) arranged in the carbon dioxide liquefaction feed tank body (201c) and communicated with the refrigerant inlet (201c-1), and a refrigerant outlet (201c-3) arranged on the side wall of the carbon dioxide liquefaction feed tank body (201c) and communicated with the cooling coil (201c-2) through an interlayer of the side wall of the carbon dioxide liquefaction feed tank body (201c), and a carbon dioxide inlet (201c-4) and a saturated carbon dioxide outlet (201c-5) which are arranged on the side wall of the carbon dioxide liquefaction feed tank body (201c) and are communicated with the interior of the carbon dioxide liquefaction feed tank body (201 c).
4. The supercritical water and carbon dioxide mixed working medium heat transfer experimental system of claim 1, characterized in that: the preheating and mixing unit (300) further comprises a temperature thermocouple (305) for controlling the heating temperature.
5. The supercritical water and carbon dioxide mixed working medium heat transfer experimental system of claim 3, characterized in that: the first pump outlet valve (102d) comprises a first pump outlet discharge needle valve (102d-1) and a first pump outlet ball valve (102 d-2); the second pump outlet valve (202b) comprising a second pump outlet ball valve (202 b-1); the water supply unit (100) and the carbon dioxide supply unit (200) each include a pulsation damper (102 g).
6. The supercritical water and carbon dioxide mixed working medium heat transfer experimental system of claim 1, characterized in that: the heat transfer system is an open system, and the mixed working medium passes through the pressure control discharge unit (500) and then is discharged after being separated from carbon dioxide through a separation tank (503).
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| CN113670974B (en) * | 2021-09-18 | 2023-10-31 | 天津大学合肥创新发展研究院 | Supercritical CO 2 Mixed working medium heat exchange experiment system |
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