CN113252378A

CN113252378A - Cold accumulation working medium test method for cold accumulation tank

Info

Publication number: CN113252378A
Application number: CN202110665393.8A
Authority: CN
Inventors: 邢美波; 景栋梁; 张洪发; 贾朝富; 王瑞祥
Original assignee: Beijing University of Civil Engineering and Architecture
Current assignee: Beijing University of Civil Engineering and Architecture
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2021-08-13
Anticipated expiration: 2041-06-16
Also published as: CN113252378B

Abstract

The invention discloses a cold accumulation working medium test method of a cold accumulation tank, which comprises the following steps: a obtaining Fe₃O₄-CNTs composite nanoparticles; b corresponding proportions of surfactant and Fe obtained₃O₄The CNTs composite nano particles are added into water according to the minimum proportion requirement to prepare a cold accumulation working medium for a test; c obtaining Fe by heating one end and detecting the temperature of the other end₃O₄-optimal addition ratio of CNTs composite nano particles and corresponding optimal control of magnetic field size. The invention can quickly obtain Fe in the cold accumulation working medium in the cold accumulation tank device₃O₄-optimal addition ratio of CNTs composite nanoparticles, and corresponding control of magnetic field magnitudeThe advantages of (1).

Description

Cold accumulation working medium test method for cold accumulation tank

Technical Field

The invention relates to the technical field of cold storage tanks, in particular to a cold storage working medium test method for a cold storage tank.

Background

With the acceleration of the modern society process, the energy consumption continuously and rapidly increases, and in 2014, China becomes the first energy consuming country in the world. With the continuous advance of industrialization in China, the urbanization rate is continuously improved, so that the electricity consumption for production and life is continuously increased, the phenomenon of peak-valley load of power supply of a power grid is caused due to the regular work and rest time of people day and night, and the power supply efficiency of the power grid is low and the waste of power resources is serious due to the great difference of day and night electricity consumption. Meanwhile, in the urban power utilization structure, the power load proportion of the air conditioning system is large. The existing ice cold storage air conditioner can make water into ice at the electric wave valley time for the power grid at night, utilizes the phase change latent heat of the ice to store cold quantity, and releases the cold quantity of the ice to be used for cooling the air conditioner at the power grid power utilization peak time in the daytime. The ice storage air conditioning technology can solve the problem of unmatched energy supply and demand, and the ice storage air conditioning technology is adopted to realize load peak load shifting and valley filling of a power grid, so that not only can electric power resources be fully utilized, but also the capacity and the power distribution capacity of refrigeration equipment can be reduced, and the energy utilization rate is improved.

The ice storage air conditioner usually adopts a cold storage tank device to realize ice storage and cold storage, so the cold storage tank is also called as an ice storage tank, the structure of the ice storage tank usually comprises a containing body, water is contained in the inner cavity of the containing body to be used as a cold storage working medium, and a heat exchange structure is further arranged in the containing body to realize heat exchange. For example, in a traditional coil type ice storage device with an internal ice-melting ice, an internal ice-melting cold storage tank is a sealed heat preservation box body, a coil is arranged in the box body and used as a heat exchange structure, a coolant is arranged in the coil in a flowing mode, the coolant is usually glycol solution, and water is arranged outside the coil. The coil pipe of the heat exchange structure is used as a heat exchange component for supplying cold to water in the cold storage tank to freeze the cold storage tank and also used as a heat exchange component for conveying cold quantity of ice outwards to an indoor load end for cooling. When cold accumulation is carried out, the coil is connected into the power end refrigerating system under the control of a selector switch on a pipeline outside the coil, low-temperature glycol solution cooled by the power end refrigerating system enters the coil, and ice accumulation and cold accumulation are carried out outside the coil. When the coil pipe is cooled, the coil pipe is connected into an energy supply system at an indoor load end, high-temperature glycol solution from the indoor load end flows through the coil pipe for heat exchange, and ice outside the coil pipe is melted for cooling.

The existing cold storage tank device has the following defects: in the cold storage tank device of interior ice-melt formula, the coil pipe of heat transfer structure makes its heat transfer part that freezes as the cold storage inslot water cooling simultaneously in the cold storage tank to and when outwards carrying the cold volume of ice to the heat transfer part of indoor load end cooling, two kinds of functions need to switch over the use, so air conditioning system can't outwards supply cold in the refrigerated while for the cold storage tank, has the application restriction. In the external ice melting type cold accumulation tank, when water in the cold accumulation tank is completely frozen, the flow of circulating water in the cold supply circulating system can be influenced, the cold supply circulating system is limited, and the cold supply circulating system directly adopts a cold accumulation working medium in the cold accumulation tank as a heat exchange medium, so that the cold accumulation working medium is easily polluted. In addition, among the current cold-storage tank device, in order to improve heat exchange efficiency, the heat transfer structure often can occupy great volume and can be located cold-storage tank middle part position, like this, the cold-storage working medium in the cold-storage tank is the freeze thawing process repeatedly, can cause the damage to the heat transfer structure, reduces its life.

In order to solve the above problems, the applicant considers and designs a cold storage tank device, which comprises a cold storage tank, a cold storage working medium is arranged in the cold storage tank, and the cold storage tank device also comprises a heat exchange structure for input and a heat exchange structure for output which are positioned in the cold storage tank, and is characterized in that the heat exchange structure for input is an evaporator coil and is positioned at one end part of an inner cavity of the cold storage tank, the heat exchange structure for output is a heat exchange coil and is positioned at the other end part of the inner cavity of the cold storage tank, the cold storage working medium₃O₄-mixture of CNTs composite nanoparticles and surfactant, Fe₃O₄The CNTs composite nano particles are used as crystal nucleus materials, and the crystal nucleus materials also comprise an electromagnetic device arranged outside the cold storage tank, wherein the inner cavity of the cold storage tank is positioned in the action range of the magnetic field of the electromagnetic device, and the direction of the magnetic field in the inner cavity of the cold storage tank is opposite to the heat exchange structure for input and the heat exchange structure for output.

Therefore, in the process of exchanging heat between the heat exchange structure and the cold accumulation working medium, and cooling and crystallizing the cold accumulation working medium, the electromagnetic device can be started firstly, and the Fe serving as a crystal nucleus₃O₄the-CNTs composite nano particles are magnetic strips, so that the particles can act on an electromagnetic deviceThe length direction of the lower part of the phase-change energy storage medium is arranged in the direction of the magnetic field. Because the direction of the magnetic field is consistent with that of the heat exchange structure, crystal nuclei are formed and arranged in the direction pointing to the heat exchange structure, and a heat transfer path pointing to the direction of the heat exchange structure can be generated in the phase change energy storage medium; thereby greatly improving the heat transfer efficiency between the cold accumulation working medium and the heat exchange structure and realizing the effect of controllably improving the heat exchange efficiency of the device.

However, when the cold storage tank device is applied, how to quickly confirm Fe in the cold storage working medium₃O₄The optimal adding proportion of the CNTs composite nano particles and the corresponding control of the magnetic field size so as to achieve the optimal heat transfer effect become problems to be considered and solved by the people in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: how to provide a device capable of quickly obtaining a cold storage tank and storing Fe in a cold storage working medium₃O₄The optimal adding proportion of the CNTs composite nano particles and a corresponding cold storage working medium test method of the cold storage tank for controlling the size of the magnetic field.

In order to solve the technical problems, the invention adopts the following technical scheme:

a cold accumulation working medium test method for a cold accumulation tank is characterized by comprising the following steps: a obtaining Fe₃O₄-CNTs composite nanoparticles; b corresponding proportions of surfactant and Fe obtained₃O₄The CNTs composite nano particles are added into water according to the minimum proportion requirement to prepare a cold accumulation working medium for a test; c, heating at one end of the cold storage working medium for the test with fixed heating efficiency, detecting the temperature of the cold storage working medium for the test at the other end of the cold storage working medium for the test, continuously applying a fixed magnetic field pointing to the direction from the heating end to the detection end to the cold storage working medium for the test in the heating process, and obtaining the time required when the temperature reaches a preset temperature value; d sequential adjustment to increase Fe₃O₄The proportion of the CNTs composite nano particles is detected by repeating the step c, and Fe corresponding to the required minimum time value is obtained₃O₄-CNTs composite nanoparticles addition ratio, and identified as optimum ratio; e will fix the magnetAnd (c) replacing the field with a controllable magnetic field, fixing the cold accumulation working medium at an optimal proportion, sequentially adjusting the cold accumulation working medium under different magnetic field sizes, repeating the operation of the step (c), obtaining the magnetic field size corresponding to the required minimum time value, and determining the magnetic field size as the optimal control magnetic field size.

This is because the surfactant is used to adsorb Fe in the cold storage working medium₃O₄The surface activity and repulsion of the CNTs composite nano particle are improved, so that the CNTs composite nano particle can be in a suspension state in water and can resist the action force of a magnetic field to a certain extent, the CNTs composite nano particle is prevented from being directly attracted to a magnetic pole position by the action force of the magnetic field, and therefore the quantity of the surfactant is only equal to that of Fe₃O₄The quantity of-CNTs composite nanoparticles is related, usually in terms of surfactant and Fe₃O₄The mass ratio of the-CNTs composite nano particles is (0.5-3): 1 is added. And Fe₃O₄The concentration of the-CNTs composite nano particles is closely related to the heat transfer performance of the cold storage working medium if Fe₃O₄If the concentration of the-CNTs composite nanoparticles is too low, the heat transfer efficiency is low due to an insufficient amount of the heat transfer medium, but if the concentration is too high, the heat transfer efficiency is reduced due to easy agglomeration and precipitation, and the smoothness of the direction adjustment is affected, so that Fe₃O₄The higher the concentration of the-CNTs composite nanoparticles is not, the better. The concentration ratio can be obtained through the test, and the heat transfer performance of the cold accumulation working medium can be ensured to be optimal. At the same time, in Fe₃O₄After the proportion of the-CNTs composite nano particles is confirmed, the magnitude of a magnetic field can become the largest influence factor of thermal conductivity. Because the magnetic field is too large, Fe is caused₃O₄The CNTs composite nano particles are adsorbed to the magnetic pole position in a whole body, so that a heat transfer path is interrupted, and heat transfer efficiency is influenced. When the magnetic field is too small, Fe is caused₃O₄The CNTs composite nano particles cannot be adjusted to a state of pointing to the direction of a magnetic field along a straight line under the action of the magnetic field force. Therefore, by adopting the test method, the optimal Fe can be obtained firstly₃O₄And (4) adding the CNTs composite nano particles in proportion, and then obtaining the optimal magnetic field size. The heat transfer performance of the cold accumulation working medium can reach the best, and the heat exchange effect of the cold accumulation tank can reach the maximum. At the same time, the methodThe steps have the advantages of simple and stable operation, easy control and the like.

Further, the cold-storage working medium test device is carried out by adopting the following cold-storage working medium test device, the cold-storage working medium test device comprises a test container which is integrally in a closed state, a water inlet pipeline is communicated with the upper end of the test container, a water outlet pipeline with a switch valve is communicated with the lower end of the test container outwards, a batching adding inlet is further formed in the upper end of the test container, an electric heating module is arranged at the lower end of an inner cavity of the test container, a temperature probe is fixedly arranged in the middle of the upper end of the inner cavity, an electromagnetic device is further arranged outside the upper end and/or the lower end of the test container, an oscillation generating device is further arranged outside the lower end of the test container, and the control center is connected with.

Thus, the test equipment can be conveniently used for completing the test steps. During specific tests, water is added into the inner cavity of the test container through the water inlet pipeline, and then the surfactant and the Fe in corresponding proportions are added through the ingredient adding inlet₃O₄the-CNTs composite nano particles are prepared into cold accumulation working medium for test, and when the cold accumulation working medium is added, a surfactant can be added firstly, an oscillation generating device is used for oscillation to enable the surfactant to be uniformly distributed, and then Fe is added₃O₄And (3) the CNTs composite nano particles are oscillated by an oscillation generating device to be uniformly distributed, so that the configuration of the cold storage working medium for the test is completed. Increase of Fe is required₃O₄When the proportion of the-CNTs composite nano particles is operated, the surfactant is added firstly and is uniformly oscillated, and then Fe is added₃O₄CNTs composite nanoparticles and oscillation uniformity. Then, the electromagnetic device is controlled to exert the magnetic field action, the size of the magnetic field is adjusted according to the requirement, the electric heating module is controlled to heat according to fixed power, the time required by the temperature probe to reach the preset temperature is recorded, and the preset temperature is larger than the normal temperature of water and smaller than the boiling temperature. Then, the test process can be completed according to the specific test steps. Therefore, the test equipment has the advantages of simple structure, convenience in operation, contribution to test implementation operation, guarantee of accurate and reliable test results and the like.

Furthermore, at least one side of the test container is also provided with an observation window made of transparent materials and arranged along the height direction. This facilitates observation of the internal conditions.

Furthermore, the shape and the size of the inner cavity of the test container are consistent with those of the inner cavity of the cold accumulation tank.

Therefore, the test is more targeted, and the application effect of the test result can be better ensured.

Furthermore, the electromagnetic device of the cold accumulation working medium test equipment is consistent with the electromagnetic device of the cold accumulation tank.

Further, the oscillation generating device is an ultrasonic oscillator. The oscillation stirring effect can be better improved.

Furthermore, a constant-temperature water bath interlayer is arranged on the circumferential direction and the outer wall of the bottom of the test container, a water bath circulating water inlet and a water bath circulating water outlet are communicated with the constant-temperature water bath interlayer, and the water bath circulating water inlet and the water bath circulating water outlet are externally connected with a constant-temperature water bath control device.

Therefore, when the cold accumulation working medium is configured, the constant-temperature water bath environment is improved, the configuration of the cold accumulation working medium is facilitated, and the cold accumulation working medium is optimally configured under the requirement of the constant-temperature water bath at 50 ℃.

Furthermore, two electrifying leads which are arranged in parallel at intervals are connected into the inner cavity of the test container, one electrifying lead is connected with a section of long platinum wire (the length of which can be taken as 100 mm), the other electrifying lead is connected with a section of short platinum wire (the length of which can be taken as 40mm so as to be convenient for calculation) which is arranged in parallel with the long platinum wire, the long platinum wire and the short platinum wire are respectively connected with a thermocouple, and the electrifying leads and the thermocouples are respectively connected with a control center to form a transient double-hot-wire method measuring system.

Therefore, the test equipment can be used for realizing the measurement by a transient double-heat-wire method, and finishing the measurement of the specific heat conductivity of the cold storage working medium so as to conveniently perfect test data, verification and feedback test effects. The specific transient dual hot line measurement is prior art and is not described in detail herein.

Further, said Fe₃O₄the-CNTs composite nano particles are prepared by the following method: a, acidizing a multi-walled carbon nano tube by using concentrated nitric acid, washing to be neutral, and drying; b, adding a certain amount of pure water into a certain amount of acidified multi-walled carbon nanotubes, and uniformly dispersing the multi-walled carbon nanotubes in the water to form a carbon nanotube dispersion liquid; c taking a certain amount of FeCl₃·6H₂O and FeCl₂·4H₂Mixing O and adding pure water to prepare a ferric salt solution; d, adding the carbon nano tube dispersion liquid obtained in the step b into the ferric salt solution obtained in the step c, adding ammonia water and sodium dodecyl benzene sulfonate dispersing agent under a stirring state to react to generate ferroferric oxide, and loading the ferroferric oxide on the carbon nano tube; e after the reaction is finished, precipitating the reactant, repeatedly washing the reactant by pure water to be neutral, and drying the reactant to obtain Fe₃O₄-CNTs composite nanoparticles.

Thus, the multi-walled carbon nano tube adopted in the step a can be beneficial to better realizing the loading of the ferroferric oxide and the subsequent surfactant. Concentrated nitric acid is adopted to acidify the multi-walled carbon nano-tube, so that the multi-walled carbon nano-tube has hydrophilicity, active groups such as hydroxyl, carboxyl and the like can be generated on the surface of the carbon nano-tube, certain electronegativity is further shown, and the loading of ferroferric oxide can be better realized. And then adding water into the reactants in the two aspects in the steps b, c and d to disperse the reactants in the two aspects to form carbon nano tube dispersion liquid and ferric salt solution, and combining the carbon nano tube dispersion liquid and the ferric salt solution, compared with a mode of adding the reactants in the two aspects into the water one by one, the uniform dispersion of the carbon nano tube can be ensured, the ferric salt is completely dissolved, and the load uniformity of the ferroferric oxide on the carbon nano tube can be further improved. Then in step d, ammonia water is dripped for reaction by adopting a coprecipitation method, namely, a certain amount of Sodium Dodecyl Benzene Sulfonate (SDBS) is added for surface modification of the carbon nano tube so as to enhance the electronegativity of the surface and Fe³⁺A stronger bonding force is formed between the two. Simultaneously, the dropwise added sodium dodecyl benzene sulfonate is used as a surfactant (SDBS), the sodium dodecyl benzene sulfonate can be adsorbed to the surface of the carbon nano tube due to the self characteristics, and then part of ferroferric oxide particles responsible for the pores of the carbon nano tube are blocked to form a similar coating effect, so that the carbon nano tube is coated with the ferroferric oxide particlesThe reliability of the suction of the carbon nano tube and the ferroferric oxide load is improved in one step. In addition, the sodium dodecyl benzene sulfonate is attached to the surface of the carbon nano tube and can achieve the purpose of deagglomeration by means of self activity. Therefore, in the process of subsequently adopting the magnet to adsorb reaction products on the side wall of the reaction container, the phenomenon that a large amount of composite nano particles are precipitated to reach the bottom of the container and are poured away and lost due to self agglomeration is avoided.

Further, the step a specifically comprises: putting the multi-walled carbon nanotube into an oven to bake (24 hours) to remove moisture in the carbon nanotube, mixing the multi-walled carbon nanotube and the concentrated nitric acid according to the proportion that 1g of the multi-walled carbon nanotube corresponds to 90-110mL (optimal 100 mL), carrying out reflux treatment in a water bath at 55-75 ℃ (optimal 65 ℃) for 2-4 hours (optimal 3 hours), naturally cooling to room temperature, washing with pure water to be neutral, carrying out suction filtration by using a suction filtration device, and then transferring to a drying oven to dry.

In this way, the acidification treatment effect can be optimized.

Further, in the step b, 0.05g of multi-wall carbon nano-tube is mixed and added according to the proportion of 10mL of pure water, and the mixture is subjected to ultrasonic oscillation for about 10 minutes to complete uniform dispersion.

Thus, the effect of uniform dispersion can be more effectively obtained.

Further, FeCl in step c₃·6H₂O and FeCl₂·4H₂Taking the amount of O according to the mass ratio of 2.7:1, and adding FeCl₂·4H₂Adding the pure water into the mixture according to the mass ratio of O to the multi-wall carbon nano tubes (0.5-2) to 1; wherein, the solid substance and the pure water can be added according to the mass ratio of 1:40-60 (50 is the best).

Thus, the reaction can be promoted more effectively, and the excess reaction material can be avoided.

And further, stirring is realized by adopting a magnetic stirring mode in the step d, the mass fraction of dropwise added ammonia water is 25%, the addition mass of the sodium dodecyl benzene sulfonate dispersing agent is 0.5-1 time of that of the carbon nano tube, the ammonia water is firstly dropwise added, then the sodium dodecyl benzene sulfonate is added, and then the reaction is carried out for 30 minutes at the temperature of 70 ℃.

This can assist in being higherThe reaction is completed quickly and better, and the reaction equation is FeCl₂+FeCl₃+8NH₄OH→Fe₃O₄+8NH₄Cl+4H₂And O. And ammonia water is dropwise added for reaction, and then sodium dodecyl benzene sulfonate is added, so that the carbon nano tube can firstly complete the loading of the ferroferric oxide, a large amount of the ferroferric oxide enters the pores of the carbon nano tube, and then the sodium dodecyl benzene sulfonate is added, thereby achieving the purposes of better enhancing the loading effect of the carbon nano tube on the ferroferric oxide and deagglomerating the carbon nano tube.

Furthermore, in the step e, after the reaction is finished, a magnet is arranged outside the side wall of the reaction container to place Fe of the reaction product₃O₄The CNTs composite nano particles are sucked and fixed on the side wall of the reaction container, and the rest reaction products and reaction solution are poured out; meanwhile, in the process of pure water washing, Fe is carried out by means of a magnet in the same way₃O₄And attracting the CNTs composite nano particles to the side wall of the washing container, and pouring washing liquid until the washing is neutral.

In this way, the magnet is adopted to assist in realizing precipitation, so that the primary selection of reaction products can be realized, the precipitated composite nanoparticles are guaranteed to be loaded with enough ferroferric oxide particles, the magnetic field reaction effect is sufficient, and the rest carbon nanotubes loaded with the ferroferric oxide particles and having insufficient effects are abandoned. And meanwhile, in the repeated washing process, the selection is realized in the same way. So that part of the composite nanoparticles with insufficiently tight attraction effect between the ferroferric oxide and the carbon nanotubes can not be adsorbed by the magnet after the magnetic effect is reduced due to the falling of the ferroferric oxide in the washing process, and the part of the composite nanoparticles with poor stability is discarded, thereby ensuring that the obtained Fe₃O₄The CNTs composite nano particles are all composite nano particles which have enough magnetism to be capable of mutually reacting with a magnetic field with the required magnetic force, and meanwhile, the composite nano particles with enough magnetic force stability are ensured. Thus, the quality requirement of the composite nano particles in the subsequent application process is ensured, and the final product effect is ensured. Wherein, the magnet adopts the way of attracting at the container side wall position, also guarantees to leave alone compoundThe nano particles have the effect of magnetic force greater than that of gravity, so that the quality requirement of subsequent application is better ensured.

Further, the cold storage tank device aimed at by the method comprises a cold storage tank, wherein a cold storage working medium is arranged in the cold storage tank, the cold storage tank device further comprises a heat exchange structure for input and a heat exchange structure for output, the heat exchange structure for input is an evaporator coil and is located at one end of an inner cavity of the cold storage tank, the heat exchange structure for output is a heat exchange coil and is located at the other end of the inner cavity of the cold storage tank, crystal nuclei are arranged in the cold storage working medium, and the thermal conductivity of the crystal nuclei is greater than that of the cold storage working medium.

Like this, the heat transfer structure for the input is connected in refrigeration cycle system and is used for providing cold volume for the cold-storage tank, and the heat transfer structure for the output is connected in the cold supply cycle system and is used for exporting cold volume. Therefore, the refrigeration circulation system and the cooling circulation system respectively adopt respective heat exchange media, the control of the respective heat exchange media is conveniently realized, the control of the respective heat exchange process of the system is further conveniently realized, and the limitation on the control of the heat exchange process is reduced. Meanwhile, the heat exchange structure for input and the heat exchange structure for output respectively adopt coil pipes and are arranged at two ends of the inner cavity of the cold storage tank, so that the cold storage tank cannot be pulled and damaged by the heat exchange structure due to water freezing expansion in the repeated freezing and thawing process of the cold storage working medium. The service life of the equipment is prolonged. Meanwhile, as the crystal nucleus is added into the cold accumulation working medium, the crystal nucleus can accelerate the freezing process of the cold accumulation working medium and is beneficial to heat transfer of the cold accumulation working medium. So that the heat exchange efficiency is not reduced. In addition, the heat transfer medium does not contact with the cold accumulation working medium for circulation, so that the cold accumulation working medium can be better protected, and the heat transfer effect of the crystal nucleus is protected.

Further, the heat exchange structure for input and the heat exchange structure for output are respectively arranged at the end parts of the two ends of the inner cavity of the cold storage tank in the vertical direction.

Like this, compare with the setting both ends tip about, can avoid cold-storage working medium to freeze the pulling power that the in-process produced heat transfer structure forms destruction to the repetition better, improved device stability in use, prolonged the life of device.

Further, the phase change energy storage medium is water.

Therefore, the device is applied to the ice storage air conditioner, and the heat exchange efficiency of the ice storage air conditioner can be greatly improved. Certainly, when implementing, the phase change energy storage medium can also be other phase change materials, and this device also can be applied to other phase change material heat-retaining heat exchange equipment.

As optimization, the crystal nucleus is a strip-shaped magnetic crystal nucleus material and further comprises an electromagnetic device arranged outside the cold storage tank, and the inner cavity of the cold storage tank is located in the magnetic field action range of the electromagnetic device, and the magnetic field direction in the inner cavity of the cold storage tank is opposite to the input heat exchange structure and the output heat exchange structure.

Like this, exchange the heat at heat transfer structure and cold-storage working medium, the cold-storage working medium cooling crystallization in-process can start electromagnetic means earlier, because the crystal nucleus is for having magnetic rectangular shape, so can form the arrangement of length direction pointing to magnetic field direction in the phase change energy storage medium under the electromagnetic means effect. Because the direction of the magnetic field is consistent with that of the heat exchange structure, crystal nuclei are formed and arranged in the direction pointing to the heat exchange structure, and a heat transfer path pointing to the direction of the heat exchange structure can be generated in the phase change energy storage medium; thereby greatly improving the heat transfer efficiency between the cold accumulation working medium and the heat exchange structure and realizing the effect of controllably improving the heat exchange efficiency of the device.

Furthermore, the number of the electromagnetic devices is two, and the two electromagnetic devices are respectively arranged at the upper end and the lower end of the cold storage tank. Therefore, the uniform and stable magnetic field intensity in the cold storage tank can be better ensured, the heat transfer uniformity is improved, the heat exchange coil is better protected, and the influence on the heat exchange efficiency and the influence on the service life due to the uneven heating of the heat exchange coil are avoided.

Or the whole cold storage tank is cylindrical, and the electromagnetic device comprises an electromagnetic coil wound outside the cold storage tank. Thus, even and stable magnetic field intensity can be formed in the cold storage tank, and the uniformity of heat transfer is improved.

Further, the magnetic crystal nucleus material is a carbon nano tube loaded with ferroferric oxide. Namely Fe₃O₄-CNTs composite nanoparticles.

The carbon nano tube loaded with ferroferric oxide is an existing magnetic composite powder material, and is generally used as an adsorbent with a reduction effect in the field of sewage treatment or medical treatment. The carbon nano tube phase change energy storage material is used for crystal nuclei of phase change energy storage media, because the radial dimension of the carbon nano tube is nano-scale and the axial dimension is micro-scale, the whole body is in a long strip shape similar to a silk shape under a microscopic angle, and after the axis direction of the carbon nano tube is directionally arranged along the direction of a magnetic field under the action of an electromagnetic field, heat can be better transferred along the direction. Meanwhile, the carbon nano tube has light weight, can be more conveniently controlled to be uniformly dispersed in the phase change energy storage medium in a suspension state after being loaded with ferroferric oxide, and has the effect of crystal nucleus when the liquid phase change energy storage material is crystallized. In addition, the carbon nano tube serving as the crystal nucleus has high self heat transfer efficiency, and the heat transfer efficiency between the phase change energy storage medium and the heat exchange structure can be better improved. The carbon nano tube loaded with ferroferric oxide has magnetic particles and shows a tendency of directional arrangement along the direction of a magnetic field under the action of the magnetic field. This state is due to the assembly of ferroferric oxide nanoparticles into chains in the magnetic fluid. The chain structure is composed of a plurality of tiny magnetic poles which are mutually attracted, the superposition of countless N-S magnetic poles shows strong magnetism, the magnetic composite material is magnetized under the action of a magnetic field, so that N-S poles are formed at two ends of the carbon nano tube, the direction can be linearly arranged along the direction of a magnetic induction line, a heat transfer path is formed in water serving as a phase change energy storage medium, and the heat transfer efficiency of the phase change energy storage medium is greatly improved.

Further, the cold accumulation working medium comprises water and Fe₃O₄-mixtures of CNTs composite nanoparticles and surfactants, wherein the surfactants and Fe₃O₄The mass ratio of the CNTs composite nano particles is (0.5-3): 1, water and Fe₃O₄The mass ratio of the CNTs composite nano particles is (100- & 1000): 1. preferably about 500: 1.

The cold storage working medium adopting the components in the proportion can be automatically attached to Fe due to the adsorptivity of the hydrophilic group of the surfactant to the solid₃O₄The pores and the surface of the-CNTs composite nano particles enable the carbon nano particles to form a surface inner layer which is attracted and loaded with ferroferric oxide particles, and a surface outer layerThe particles with the surfactant component absorbed are supported. The proportion of the material proportion is large and small, so that under the action of the dispersing effect of the surfactant, the carbon nano particles can be mutually separated and are in a suspension state in water, the magnetic carbon nano particles can resist magnetic field attraction force to a certain extent under the action of a magnetic field, the carbon nano particles can be kept at the positions of the carbon nano particles to the greatest extent under the action of the magnetic field and are adjusted to be arranged along the direction of the magnetic field by the magnetic field, the trend that the carbon nano particles are directly close to the magnetic pole position of the magnetic field is reduced, and a heat transfer path is better generated in water.

The surfactant can be acacia gum, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide, and the preferred sodium dodecyl benzene sulfonate has the advantages of good binding property with the nano particles, good dispersing effect and the like.

Further, the cold accumulation working medium is prepared by the following method: 1) adding the surfactant according to the proportion requirement into water, and performing ultrasonic oscillation for 15-25 minutes (optimally 20 minutes) under the water bath condition of 40-60 ℃ (optimally 50 ℃) to obtain a surfactant aqueous solution with certain concentration; 2) fe according to the proportion requirement₃O₄Adding the-CNTs composite nano particles into a surfactant aqueous solution, uniformly stirring, then carrying out ultrasonic oscillation under the water bath condition of 40-60 ℃ (optimally 50 ℃), stopping the ultrasonic oscillation for 10 minutes every 5 minutes, and continuing the oscillation until the accumulation of the oscillation time exceeds 30 minutes (namely oscillating for at least 6 times), thereby obtaining the cold storage working medium.

The method comprises the steps of adding the surfactant into water, uniformly oscillating and adding Fe₃O₄The CNTs composite nano particles can more quickly absorb and cover the components of the surfactant to all circumferential surfaces of the magnetic carbon nano particles to achieve surface modification and form uniform repulsive force in all directions of the carbon nano particles, so that mutual repulsion among the carbon nano particles is facilitated, and agglomeration and settlement are better avoided. After the magnetic carbon nano particles are added, a repeated ultrasonic oscillation mode is adopted, the oscillation is stopped for 10 minutes after every 5 minutes, so that the magnetic carbon nano particles can be repeatedly oscillatedThe air in the pores is gradually discharged to be sucked by the surfactant component, so that the depth and the tightness of the combination of the surfactant and the carbon nano particles can be better improved, and the long-term stable combination effect is kept. Meanwhile, the suspension for ten minutes in the middle can enable bubbles formed by air discharged from the magnetic nano particles through oscillation to float upwards, form foams and dissipate the foams into the air, so that the next oscillation is facilitated, and finally the magnetic carbon nano tube solution with good stability, good dispersibility and good uniformity is formed. Shaking in a water bath at about 50 deg.C can effectively accelerate the above reaction effect. Compared with the method that the nano particles are added in advance and the dispersing agent is added, the method has the advantages that the surfactant can be completely dissolved, and the composite material is added with the surfactant which can immediately enrich the surrounding, so that the coating effect is improved. Of course, the method can also be implemented by directly adding the surfactant with the corresponding proportion into water and then adding the Fe with the corresponding proportion₃O₄And uniformly stirring the-CNTs composite nano particles integrally to prepare the cold storage working medium. However, it may require longer stirring time, the dispersion stability of the nanoparticles is relatively difficult to ensure, and the prepared cold storage working medium may be difficult to achieve the best heat exchange effect.

In conclusion, the invention can rapidly obtain Fe in the cold accumulation working medium in the device of the cold accumulation tank₃O₄The optimal adding proportion of the CNTs composite nano particles and the corresponding advantage of controlling the magnetic field size.

Drawings

Fig. 1 is a schematic diagram of a cold storage tank device and an ice storage air conditioning system according to the test method of the present invention.

FIG. 2 shows Fe in the present invention₃O₄Schematic transmission electron microscope picture of-CNTs composite nanoparticle material.

FIG. 3 shows Fe in the present invention₃O₄-XRD diffractogram of CNTs composite nanoparticle material.

FIG. 4 shows Fe in the present invention₃O₄-hysteresis loop of CNTs composite nanoparticle material.

FIG. 5 shows Fe in the present invention₃O₄-CNTs composite nanoparticlesThe material is configured into a cold storage working medium, and the micrograph is shown schematically under the action of a magnetic field.

Fig. 6 is a schematic structural diagram of a cold storage working medium test device disclosed by the invention.

Detailed Description

The cold storage tank device and the ice storage air conditioning system thereof to which the test method of the present invention is directed will be described in detail with reference to the accompanying drawings.

The specific implementation mode is as follows: an ice storage air conditioning system is shown in figure 1 and comprises a refrigeration cycle system, a cooling cycle system and a cold storage tank 1 (namely a cold storage tank device aimed at by the test method of the invention), wherein a cold storage working medium is arranged in the cold storage tank, the cold storage working medium is a phase change energy storage medium with crystal nuclei, the thermal conductivity of the crystal nuclei is greater than that of the phase change energy storage medium, the ice storage air conditioning system also comprises an input heat exchange structure 2 and an output heat exchange structure 3 which are positioned in the cold storage tank 1, the input heat exchange structure 2 is connected in the refrigeration cycle system and used for providing cold for the cold storage tank, and the output heat exchange structure 3 is connected in the cooling cycle system and used for outputting the cold; wherein, the crystal nucleus is rectangular shape magnetism crystal nucleus material, still including setting up electromagnetic means 4 outside cold-storage tank 1, and the cold-storage tank inner chamber is located electromagnetic means 4 magnetic field effect scope and the magnetic field direction of cold-storage tank inner chamber and input and set up with heat transfer structure relatively for the output.

Like this, when the system uses, exchange the heat at heat transfer structure and cold-storage working medium, in the cold-storage working medium cooling crystallization process, can start electromagnetic means earlier, because the crystal nucleus is for having magnetic rectangular shape, so can form the arranging of length direction pointing to magnetic field direction in the phase change energy storage medium under the electromagnetic means effect. Because the magnetic field direction is consistent with the heat exchange structure, the crystal nucleus is formed and arranged in the direction of the heat exchange structure, the heat transfer efficiency between the cold storage working medium and the heat exchange structure can be greatly improved, and the effect of controllably improving the heat exchange efficiency of the device is realized.

The refrigeration cycle system comprises a compressor 5, a condenser 6, a liquid storage device 7, an expansion valve 8 and an evaporator coil which are connected by a refrigeration medium circulation pipeline, wherein the evaporator coil is positioned in the cold storage tank and forms the heat exchange structure 2 for input; the cold supply circulating system comprises a heat exchange coil, a pressure pump 9 and a load end cold supply device 10 which are connected by a cold supply medium circulating pipeline, wherein the heat exchange coil is positioned in the cold storage tank and forms the heat exchange structure 3 for output. In fig. 1, the refrigerant medium circulation line and the refrigerant medium circulation line are indicated by lines.

Thus, the device has the advantages of simple structure and convenient implementation; meanwhile, the heat exchange structure for input and the heat exchange structure for output are separately arranged, so that the refrigeration cycle system and the cold supply cycle system respectively use the heat transfer medium of the refrigeration cycle system and the cold supply cycle system, the implementation and the control are facilitated, the heat transfer medium is not in contact with and circulates with the cold storage working medium, and the cold storage working medium can be better protected. In other embodiments, the heat exchange structure for input and the heat exchange structure for output can share the same heat exchange coil, and the heat exchange structure for input and the heat exchange structure for output are respectively connected to the refrigeration cycle system and the cold supply cycle system by means of external pipeline switching control, so that a structure similar to the coil type ice storage device for internal ice melting and ice melting is formed. Or the cold storage tank can form a heat exchange structure for output, namely, the cold storage working medium of the cold storage tank is directly connected into the cold supply circulating system to be used as a heat exchange medium for cold supply; forming a structure similar to the external ice-melting coil type ice storage device.

Wherein, the heat exchange structure 2 for input and the heat exchange structure 3 for output are respectively arranged at the upper and lower end parts of the inner cavity of the cold storage tank.

Therefore, the situation that the pulling force generated by the heat exchange structure in the repeated freezing and thawing process of the cold storage working medium is damaged due to the fact that the specific gravity of the cold storage working medium solid-state liquid in the cold storage tank is different can be avoided, the use stability of the device is improved, and the service life of the device is prolonged. Meanwhile, the heat transfer rate from the cold accumulation working medium to the heat exchange structure is greatly improved by controlling the heat transfer path formed by the magnetic crystal nucleus material, so that the reduction of the heat exchange efficiency cannot be caused. The product can reduce the influence of repeated freezing and thawing of the cold accumulation working medium on the heat exchange coil pipe to the maximum extent, and can also improve the heat transfer efficiency between the cold accumulation working medium and the heat exchange coil pipe.

Wherein, the two electromagnetic devices 4 are respectively arranged at the upper end and the lower end of the cold storage tank 1. Therefore, the uniform and stable magnetic field intensity in the cold storage tank can be better ensured, the heat transfer uniformity is improved, the heat exchange coil is better protected, and the influence on the heat exchange efficiency and the influence on the service life due to the uneven heating of the heat exchange coil are avoided.

Wherein the phase change energy storage medium is water.

Wherein the magnetic crystal nucleus material is a carbon nano tube loaded with ferroferric oxide. Namely Fe₃O₄-CNTs composite nanoparticles.

Wherein the cold storage working medium comprises water and Fe₃O₄-mixtures of CNTs composite nanoparticles and surfactants, wherein the surfactants and Fe₃O₄The mass ratio of the CNTs composite nano particles is (0.5-3): 1, water and Fe₃O₄The mass ratio of the CNTs composite nano particles is (100- & 1000): 1. most preferably a 500:1 ratio.

The cold storage working medium adopting the components in the proportion can be automatically attached to Fe due to the adsorptivity of the hydrophilic group of the surfactant to the solid₃O₄And the pores and the surface of the CNTs composite nano particles enable the carbon nano particles to form particles with the surface inner layer attracting and loading ferroferric oxide particles and the surface outer layer loading and attracting the components of the surfactant. The proportion of the material proportion is large and small, so that under the action of the dispersing effect of the surfactant, the carbon nano particles can be mutually separated and are in a suspension state in water, the magnetic carbon nano particles can resist magnetic field attraction force to a certain extent under the action of a magnetic field, the carbon nano particles can be kept at the positions of the carbon nano particles to the greatest extent under the action of the magnetic field and are adjusted to be arranged along the direction of the magnetic field by the magnetic field, the trend that the carbon nano particles are directly close to the magnetic pole position of the magnetic field is reduced, and a heat transfer path is better generated in water.

In implementation, the cold storage working medium can be prepared by the following method: 1) adding the surfactant into water according to the proportion, and performing ultrasonic oscillation for 15-25 minutes (preferably 20 minutes) in 40-60 deg.C (preferably 50 deg.C) water bathTo obtain a surfactant aqueous solution with a certain concentration; 2) fe according to the proportion requirement₃O₄Adding the-CNTs composite nano particles into a surfactant aqueous solution, uniformly stirring, then carrying out ultrasonic oscillation under the water bath condition of 40-60 ℃ (optimally 50 ℃), stopping the ultrasonic oscillation for 10 minutes every 5 minutes, and continuing the oscillation until the accumulation of the oscillation time exceeds 30 minutes (namely oscillating for at least 6 times), thereby obtaining the cold storage working medium.

The method comprises the steps of adding the surfactant into water, uniformly oscillating and adding Fe₃O₄The CNTs composite nano particles can more quickly absorb and cover the components of the surfactant to all circumferential surfaces of the magnetic carbon nano particles to achieve surface modification and form uniform repulsive force in all directions of the carbon nano particles, so that mutual repulsion among the carbon nano particles is facilitated, and agglomeration and settlement are better avoided. After the magnetic carbon nano particles are added, a repeated ultrasonic oscillation mode is adopted, and the oscillation is stopped for 10 minutes after every 5 minutes, so that the air in the pores can be gradually discharged in the repeated oscillation process of the magnetic carbon nano particles to be sucked and entered by the components of the surfactant, the combination depth and the tightness of the surfactant and the carbon nano particles can be better improved, and the long-term stable combination effect can be kept. Meanwhile, the suspension for ten minutes in the middle can enable bubbles formed by air discharged from the magnetic nano particles through oscillation to float upwards, form foams and dissipate the foams into the air, so that the next oscillation is facilitated, and finally the magnetic carbon nano tube solution with good stability, good dispersibility and good uniformity is formed. Shaking in a water bath at about 50 deg.C can effectively accelerate the above reaction effect. Compared with the method that the nano particles are added in advance and the dispersing agent is added, the method has the advantages that the surfactant can be completely dissolved, and the composite material is added with the surfactant which can immediately enrich the surrounding, so that the coating effect is improved. Of course, the method can also be implemented by directly adding the surfactant with the corresponding proportion into water and then adding the Fe with the corresponding proportion₃O₄And uniformly stirring the-CNTs composite nano particles integrally to prepare the cold storage working medium. However, this may require longer stirring timesThe dispersion stability of the rice grains is relatively difficult to ensure and the prepared cold accumulation working medium is possibly difficult to achieve the best relative heat exchange effect.

Wherein, the Fe₃O₄-CNTs composite nanoparticles obtained by the following steps: a, acidizing a multi-walled carbon nano tube by using concentrated nitric acid, washing to be neutral, and drying; b, adding a certain amount of pure water into a certain amount of acidified multi-walled carbon nanotubes, and uniformly dispersing the multi-walled carbon nanotubes in the water to form a carbon nanotube dispersion liquid; c taking a certain amount of FeCl₃·6H₂O and FeCl₂·4H₂Mixing O and adding pure water to prepare a ferric salt solution; d, adding the carbon nano tube dispersion liquid obtained in the step b into the ferric salt solution obtained in the step c, adding ammonia water and sodium dodecyl benzene sulfonate dispersing agent under a stirring state to react to generate ferroferric oxide, and loading the ferroferric oxide on the carbon nano tube; e after the reaction is finished, precipitating the reactant, repeatedly washing the reactant by pure water to be neutral, and drying the reactant to obtain Fe₃O₄-CNTs composite nanoparticles.

Thus, the multi-walled carbon nano tube adopted in the step a can be beneficial to better realizing the loading of the ferroferric oxide and the subsequent surfactant. Concentrated nitric acid is adopted to acidify the multi-walled carbon nano-tube, so that the multi-walled carbon nano-tube has hydrophilicity, active groups such as hydroxyl, carboxyl and the like can be generated on the surface of the carbon nano-tube, certain electronegativity is further shown, and the loading of ferroferric oxide can be better realized. And then adding water into the reactants in the two aspects in the steps b, c and d to disperse the reactants in the two aspects to form carbon nano tube dispersion liquid and ferric salt solution, and combining the carbon nano tube dispersion liquid and the ferric salt solution, compared with a mode of adding the reactants in the two aspects into the water one by one, the uniform dispersion of the carbon nano tube can be ensured, the ferric salt is completely dissolved, and the load uniformity of the ferroferric oxide on the carbon nano tube can be further improved. Then in step d, ammonia water is dripped for reaction by adopting a coprecipitation method, namely, a certain amount of Sodium Dodecyl Benzene Sulfonate (SDBS) is added for surface modification of the carbon nano tube so as to enhance the electronegativity of the surface and Fe³⁺A stronger bonding force is formed between the two. The sodium dodecyl benzene sulfonate which is dripped at the same time is taken as a surfactant (SDBS), and the self characteristic of the sodium dodecyl benzene sulfonate can be adsorbed to the surface of the carbon nano tubeAnd then, part of ferroferric oxide particles in the pores of the carbon nano tube are blocked, a similar coating effect is formed, and the reliability of attraction of the carbon nano tube and the ferroferric oxide load is further improved. In addition, the sodium dodecyl benzene sulfonate is attached to the surface of the carbon nano tube and can achieve the purpose of deagglomeration by means of self activity. Therefore, in the process of subsequently adopting the magnet to adsorb reaction products on the side wall of the reaction container, the phenomenon that a large amount of composite nano particles are precipitated to reach the bottom of the container and are poured away and lost due to self agglomeration is avoided.

Wherein, the step a specifically comprises the following steps: putting the multi-walled carbon nanotube into an oven to bake (24 hours) to remove moisture in the carbon nanotube, mixing the multi-walled carbon nanotube and the concentrated nitric acid according to the proportion that 1g of the multi-walled carbon nanotube corresponds to 90-110mL (optimal 100 mL), carrying out reflux treatment in a water bath at 55-75 ℃ (optimal 65 ℃) for 2-4 hours (optimal 3 hours), naturally cooling to room temperature, washing with pure water to be neutral, carrying out suction filtration by using a suction filtration device, and then transferring to a drying oven to dry.

In this way, the acidification treatment effect can be optimized.

And b, mixing and adding 0.05g of multi-wall carbon nano tube in proportion to 10mL of pure water, and performing ultrasonic oscillation for about 10 minutes to complete uniform dispersion.

Thus, the effect of uniform dispersion can be more effectively obtained.

Wherein, FeCl is added in step c₃·6H₂O and FeCl₂·4H₂Taking the amount of O according to the mass ratio of 2.7:1, and adding FeCl₂·4H₂Adding the pure water into the mixture according to the mass ratio of O to the multi-wall carbon nano tubes (0.5-2) to 1; wherein, the solid and the pure water can be added according to the mass ratio of 1:40-60 (50 is the best).

And d, stirring by adopting a magnetic stirring mode, dripping 25% of ammonia water by mass, adding 0.5-1 time of sodium dodecyl benzene sulfonate dispersing agent by mass, dripping the ammonia water, adding the sodium dodecyl benzene sulfonate, and reacting at the temperature of 70 ℃ for 30 minutes.

Thus, the reaction can be assisted to be completed more efficiently and quickly, and the reaction can be completed better, and the reaction equation is FeCl₂+FeCl₃+8NH₄OH→Fe₃O₄+8NH₄Cl+4H₂And O. And ammonia water is dropwise added for reaction, and then sodium dodecyl benzene sulfonate is added, so that the carbon nano tube can firstly complete the loading of the ferroferric oxide, a large amount of the ferroferric oxide enters the pores of the carbon nano tube, and then the sodium dodecyl benzene sulfonate is added, thereby achieving the purposes of better enhancing the loading effect of the carbon nano tube on the ferroferric oxide and deagglomerating the carbon nano tube.

In the step e, after the reaction is finished, a magnet is arranged outside the side wall of the reaction container to place Fe of a reaction product₃O₄The CNTs composite nano particles are sucked and fixed on the side wall of the reaction container, and the rest reaction products and reaction solution are poured out; meanwhile, in the process of pure water washing, Fe is carried out by means of a magnet in the same way₃O₄And attracting the CNTs composite nano particles to the side wall of the washing container, and pouring washing liquid until the washing is neutral.

In this way, the magnet is adopted to assist in realizing precipitation, so that the primary selection of reaction products can be realized, the precipitated composite nanoparticles are guaranteed to be loaded with enough ferroferric oxide particles, the magnetic field reaction effect is sufficient, and the rest carbon nanotubes loaded with the ferroferric oxide particles and having insufficient effects are abandoned. And meanwhile, in the repeated washing process, the selection is realized in the same way. So that part of the composite nanoparticles with insufficiently tight attraction effect between the ferroferric oxide and the carbon nanotubes can not be adsorbed by the magnet after the magnetic effect is reduced due to the falling of the ferroferric oxide in the washing process, and the part of the composite nanoparticles with poor stability is discarded, thereby ensuring that the obtained Fe₃O₄The CNTs composite nano particles are all composite nano particles which have enough magnetism to be capable of mutually reacting with a magnetic field with the required magnetic force, and meanwhile, the composite nano particles with enough magnetic force stability are ensured. Thus, the quality requirement of the composite nano particles in the subsequent application process is ensured, and the final product effect is ensured. Wherein the content of the first and second substances,the magnet adopts a mode of attracting at the side wall of the container, and the condition that the single composite nano particles are particles with the effect of magnetic force greater than that of gravity is ensured to be remained, so that the quality requirement of subsequent application of the composite nano particles is better ensured.

FIG. 2 shows Fe obtained₃O₄-transmission electron microscopy of CNTs composite nanoparticle material. The resulting Fe can be seen in the figure₃O₄The CNTs composite nano particles are in a zigzag elongated shape in a natural condition.

FIG. 3 shows Fe obtained₃O₄The XRD diffraction pattern and X-ray diffraction (XRD) analysis of the CNTs composite nanoparticle material can not only qualitatively obtain the types and phase structures of substances, but also obtain the grain size through the Scherrer formula. FIG. 3 shows the production of Fe₃O₄XRD diffractogram of-CNTs composite nanoparticle material sample, showing vibrational peaks indicating the presence of two phases, respectively MWCNT and Fe₃O₄Peak of (1), Fe in the spectral line of the composite material₃O₄Shows 6 diffraction peaks at 30.15 °, 35.72 °, 43.32 °, 53.85 °, 57.35 ° and 63.12 °, respectively, and the positions and relative intensities of these diffraction peaks correspond to the (220), (311), (400), (422), (511), (440) crystal planes of the cubic spinel structure. In addition, the peak appearing at 26.3 ° is a characteristic peak of graphite, and is related to MWCNT. Fe₃O₄The diffraction peak of (A) was not changed, indicating that Fe₃O₄The crystal nucleus is not damaged in the coating process, and the good magnetic property is kept.

FIG. 4 shows Fe obtained₃O₄Hysteresis loop of-CNTs composite nanoparticle material, Fe₃O₄The CNTs composite nanoparticle material has superparamagnetism in a magnetic field, the magnetic properties of the composite material are evaluated by vibrating a sample magnetometer, FIG. 4 is Fe prepared in different ways₃O₄A hysteresis loop of the CNTs composite nano particle material, and the magnetic strength is quantitatively researched. Prepared Fe₃O₄The magnetic hysteresis loop of the-CNTs composite nanoparticle material is shown in FIG. 4, and the saturation magnetization of the material is 20.80 emu/g.

FIG. 5 shows Fe obtained₃O₄Schematic diagram of a micrograph of the-CNTs composite nanoparticle material under the action of a magnetic field after being configured as a cold accumulation working medium. From this figure, it can be seen that Fe is present under the action of a magnetic field₃O₄the-CNTs composite nano particles are arranged in a straight line shape, and further a heat transfer path with directivity can be formed in the cold storage working medium.

The invention discloses a test method for cold accumulation working medium of a cold accumulation tank, namely Fe in the cold accumulation working medium can be obtained by the test method₃O₄The optimal adding proportion of the CNTs composite nano particles and the corresponding control magnetic field size can achieve the optimal heat transfer effect.

When the test method is implemented, the method specifically comprises the following steps: a obtaining the above-mentioned Fe₃O₄-CNTs composite nanoparticles; b corresponding proportions of surfactant and Fe obtained₃O₄The CNTs composite nano particles are added into water according to the minimum proportion requirement to prepare a cold accumulation working medium for a test; c, heating at one end of the cold storage working medium for the test with fixed heating efficiency, detecting the temperature of the cold storage working medium for the test at the other end of the cold storage working medium for the test, continuously applying a fixed magnetic field pointing to the direction from the heating end to the detection end to the cold storage working medium for the test in the heating process, and obtaining the time required when the temperature reaches a preset temperature value; d sequential adjustment to increase Fe₃O₄The proportion of the CNTs composite nano particles is detected by repeating the step c, and Fe corresponding to the required minimum time value is obtained₃O₄-CNTs composite nanoparticles addition ratio, and identified as optimum ratio; e, replacing the fixed magnetic field with a controllable magnetic field, fixing the cold accumulation working medium at the optimal proportion, sequentially adjusting the cold accumulation working medium under different magnetic field sizes, repeating the operation of the step c, obtaining the magnetic field size corresponding to the required minimum time value, and determining the magnetic field size as the optimal control magnetic field size.

This is because the surfactant is used to adsorb Fe in the cold storage working medium₃O₄The surface activity and repulsion of the CNTs composite nano particle are improved, so that the CNTs composite nano particle can be in a suspension state in water and can resist the action force of a magnetic field to a certain extent, the CNTs composite nano particle is prevented from being directly attracted to a magnetic pole position by the action force of the magnetic field, and therefore the quantity of the surfactant is only equal to that of Fe₃O₄The quantity of-CNTs composite nanoparticles is related, usually in terms of surfactant and Fe₃O₄The mass ratio of the-CNTs composite nano particles is (0.5-3): 1 is added. And Fe₃O₄The concentration of the-CNTs composite nano particles is closely related to the heat transfer performance of the cold storage working medium if Fe₃O₄If the concentration of the-CNTs composite nanoparticles is too low, the heat transfer efficiency is low due to an insufficient amount of the heat transfer medium, but if the concentration is too high, the heat transfer efficiency is reduced due to easy agglomeration and precipitation, and the smoothness of the direction adjustment is affected, so that Fe₃O₄The higher the concentration of the-CNTs composite nanoparticles is not, the better. The concentration ratio can be obtained through the test, and the heat transfer performance of the cold accumulation working medium can be ensured to be optimal. At the same time, in Fe₃O₄After the proportion of the-CNTs composite nano particles is confirmed, the magnitude of a magnetic field can become the largest influence factor of thermal conductivity. Because the magnetic field is too large, Fe is caused₃O₄The CNTs composite nano particles are adsorbed to the magnetic pole position in a whole body, so that a heat transfer path is interrupted, and heat transfer efficiency is influenced. When the magnetic field is too small, Fe is caused₃O₄The CNTs composite nano particles cannot be adjusted to a state of pointing to the direction of a magnetic field along a straight line under the action of the magnetic field force. Therefore, by adopting the test method, the optimal Fe can be obtained firstly₃O₄And (4) adding the CNTs composite nano particles in proportion, and then obtaining the optimal magnetic field size. The heat transfer performance of the cold accumulation working medium can reach the best, and the heat exchange effect of the cold accumulation tank can reach the maximum. Meanwhile, the steps of the method have the advantages of simple and stable operation, convenience in control and the like.

In specific implementation, the test can be performed by using the cold storage working medium test device shown in fig. 6, the cold storage working medium test device includes a test container 11 which is wholly in a closed state, an inlet pipe 12 is communicated with the upper end of the test container 11, an outlet pipe 13 with a switch valve is communicated with the lower end of the test container, a material adding inlet 14 is further formed in the upper end of the test container, an electric heating module 15 is installed at the lower end of an inner cavity of the test container, a temperature probe 16 is fixedly arranged in the middle of the upper end of the inner cavity, an electromagnetic device 17 is further installed outside the upper end and/or the lower end of the test container, an oscillation generating device 18 is further installed outside the lower end of the test container, and a control center (not shown in the figure) is further included, and is respectively connected with the electric heating module, the temperature probe, the electromagnetic device and the oscillation generating device.

Wherein, at least one side of the test container 11 is also provided with an observation window 19 made of transparent material and arranged along the height direction. This facilitates observation of the internal conditions.

Wherein, the shape and the size of the inner cavity of the test container 11 are consistent with those of the inner cavity of the cold storage tank.

Wherein, the electromagnetic device 17 of the cold accumulation working medium test equipment is consistent with the electromagnetic device of the cold accumulation tank.

Wherein the oscillation generating device 18 is an ultrasonic oscillator. The oscillation stirring effect can be better improved.

Wherein, the outer wall of the circumference and the bottom of the test container is provided with a constant temperature water bath interlayer 20, a water bath circulating water inlet and a water bath circulating water outlet which are communicated with the constant temperature water bath interlayer 20, and the water bath circulating water inlet and the water bath circulating water outlet are externally connected with a constant temperature water bath control device (not shown in the figure).

Two electrifying leads 21 which are arranged in parallel at intervals are connected into the inner cavity of the test container, one electrifying lead is connected with a long platinum wire 22 (the length of which can be 100 mm), the other electrifying lead is connected with a short platinum wire 23 (the length of which can be 40mm so as to be convenient to calculate) which is arranged in parallel with the long platinum wire, the long platinum wire and the short platinum wire are respectively connected with a thermocouple 24, and the electrifying leads and the thermocouples are respectively connected with a control center to form a transient double-hot-wire method measuring system.

Claims

1. A cold accumulation working medium test method for a cold accumulation tank is characterized by comprising the following steps: a obtaining Fe₃O₄-CNTs composite nanoparticles; b corresponding proportions of surfactant and Fe obtained₃O₄The CNTs composite nano particles are added into water according to the minimum proportion requirement to prepare a cold accumulation working medium for a test; c, heating at one end of the cold storage working medium for test with fixed heating efficiency, detecting the temperature at the other end of the cold storage working medium for test, and heatingIn the process, a fixed magnetic field pointing to the direction from the heating end to the detection end is continuously applied to the cold accumulation working medium for the test, and the time required when the temperature reaches a preset temperature value is obtained; d sequential adjustment to increase Fe₃O₄The proportion of the CNTs composite nano particles is detected by repeating the step c, and Fe corresponding to the required minimum time value is obtained₃O₄-CNTs composite nanoparticles addition ratio, and identified as optimum ratio; e, replacing the fixed magnetic field with a controllable magnetic field, fixing the cold accumulation working medium at the optimal proportion, sequentially adjusting the cold accumulation working medium under different magnetic field sizes, repeating the operation of the step c, obtaining the magnetic field size corresponding to the required minimum time value, and determining the magnetic field size as the optimal control magnetic field size.

2. The test method of cold accumulation working medium in cold accumulation tank as claimed in claim 1, wherein the test method is carried out by using a test device of cold accumulation working medium, the test device of cold accumulation working medium comprises a test container in a closed state, the upper end of the test container is communicated with a water inlet pipe, the lower end of the test container is communicated with a water outlet pipe with a switch valve, the upper end of the test container is further provided with a material adding inlet, the lower end of the inner cavity of the test container is provided with an electric heating module, the middle part of the upper end of the inner cavity is fixedly provided with a temperature probe, the outer side of the upper end and/or the lower end of the test container is further provided with an electromagnetic device, the outer part of the lower end of the test container is further provided with an oscillation generating device, and the test device further comprises a control center, and the control center is respectively connected with the electric heating module, the temperature probe, the electromagnetic device and the oscillation generating device.

3. A test method for a cold storage working medium in a cold storage tank of claim 2, wherein at least one side of the test container is further provided with an observation window made of a transparent material and arranged along the height direction.

4. A method for testing a cold storage working medium in a cold storage tank as claimed in claim 2, wherein the shape and size of the inner cavity of the test container are the same as those of the inner cavity of the cold storage tank.

5. A cold storage tank cold storage working medium test method as claimed in claim 2, characterized in that the electromagnetic device of the cold storage working medium test apparatus is identical to the electromagnetic device of the cold storage tank.

6. The method for testing a cold storage working medium in a cold storage tank of claim 2, wherein the oscillation generating device is an ultrasonic oscillator.

7. The method for testing a cold storage working medium in a cold storage tank of claim 2, wherein the test container is provided with a constant temperature water bath interlayer on the circumferential direction and the outer wall of the bottom, and a water bath circulating water inlet and a water bath circulating water outlet which are communicated with the constant temperature water bath interlayer, and the water bath circulating water inlet and the water bath circulating water outlet are externally connected with a constant temperature water bath control device.

8. The method for testing cold storage working medium of a cold storage tank as claimed in claim 7, wherein two current conducting wires arranged in parallel at intervals are connected to the inner cavity of the test container, one current conducting wire is connected with a long platinum wire (the length of which can be 100 mm), the other current conducting wire is connected with a short platinum wire (the length of which can be 40 mm) which is parallel to the long platinum wire, the long platinum wire and the short platinum wire are respectively connected with a thermocouple, and the current conducting wires and the thermocouples are respectively connected with the control center to form a transient double hot wire method measuring system.

9. The method for testing a cold storage working medium for a cold storage tank of claim 1, wherein the Fe is₃O₄the-CNTs composite nano particles are prepared by the following method: a, acidizing a multi-walled carbon nano tube by using concentrated nitric acid, washing to be neutral, and drying; b, adding a certain amount of pure water into a certain amount of acidified multi-walled carbon nanotubes, and uniformly dispersing the multi-walled carbon nanotubes in the water to form a carbon nanotube dispersion liquid; c taking a certain amount of FeCl₃·6H₂O and FeCl₂·4H₂Mixing O and adding pure water to prepare a ferric salt solution; d, adding the carbon nano tube dispersion liquid obtained in the step b into the ferric salt solution obtained in the step c, adding ammonia water and the sodium dodecyl benzene sulfonate dispersing agent under the stirring state, and reacting to generateFerroferric oxide is loaded on the carbon nano tube; e after the reaction is finished, precipitating the reactant, repeatedly washing the reactant by pure water to be neutral, and drying the reactant to obtain Fe₃O₄-CNTs composite nanoparticles.

10. The method for testing a cold storage working medium in a cold storage tank of claim 9, wherein the step a comprises: putting the multi-walled carbon nanotube into an oven to bake to remove moisture in the carbon nanotube, mixing the multi-walled carbon nanotube and the carbon nanotube according to the proportion that 1g of the multi-walled carbon nanotube corresponds to 90-110mL of concentrated nitric acid, carrying out reflux treatment in a water bath at 55-75 ℃ for 2-4 hours, naturally cooling to room temperature, washing with pure water to be neutral, carrying out suction filtration by using a suction filtration device, and then transferring to a drying oven to dry;

in the step b, 0.05g of multi-walled carbon nanotube is mixed and added according to the proportion of 10mL of pure water, and the mixture is subjected to ultrasonic oscillation for 10 minutes to complete uniform dispersion;

FeCl in step c₃·6H₂O and FeCl₂·4H₂Taking the amount of O according to the mass ratio of 2.7:1, and adding FeCl₂·4H₂Adding the pure water into the mixture according to the mass ratio of O to the multi-wall carbon nano tubes (0.5-2) to 1;

d, stirring by adopting a magnetic stirring mode, dropwise adding 25% of ammonia water by mass, adding 0.5-1 time of sodium dodecyl benzene sulfonate dispersing agent by mass, dropwise adding the ammonia water, then adding the sodium dodecyl benzene sulfonate, and reacting for 30 minutes at the temperature of 70 ℃;

e, after the reaction is finished, placing a magnet outside the side wall of the reaction container to enable Fe of a reaction product₃O₄The CNTs composite nano particles are sucked and fixed on the side wall of the reaction container, and the rest reaction products and reaction solution are poured out; meanwhile, in the process of pure water washing, Fe is carried out by means of a magnet in the same way₃O₄And attracting the CNTs composite nano particles to the side wall of the washing container, and pouring washing liquid until the washing is neutral.