阅读说明：本技术 一种高效太阳能集热装置 (High-efficiency solar heat collecting device ) 是由 牛雷 赵京 李艺维 谢大为 谢龙 于 2019-10-23 设计创作，主要内容包括：本发明提供了一种高效太阳能集热装置,包括蒸发器、汽管路、冷凝器、液管路、储液器、传热工质；所述蒸发器的上下两端分别连通汽管路、液管路的一端,所述汽管路的另一端连通冷凝器,所述液管路的另一端连通冷凝器；所述液管路的中段设有储液器；所述蒸发器包括若干块竖直阵列布置的微通道单元板,所述微通道单元板上设有若干条竖直阵列布置的微通道；冷凝器放置于水箱中,且冷凝器布置高度高于蒸发器。本发明的高效太阳能集热装置,有效集热面积大、底层传热技术传热能力强,因此集热效率高,可有效提升整个集热系统的性能和经济性。(The invention provides a high-efficiency solar heat collection device, which comprises an evaporator, a steam pipeline, a condenser, a liquid pipeline, a liquid storage device and a heat transfer working medium, wherein the evaporator is connected with the steam pipeline; the upper end and the lower end of the evaporator are respectively communicated with one end of a steam pipeline and one end of a liquid pipeline, the other end of the steam pipeline is communicated with the condenser, and the other end of the liquid pipeline is communicated with the condenser; a liquid storage device is arranged at the middle section of the liquid pipeline; the evaporator comprises a plurality of micro-channel unit plates which are vertically arranged in an array, and a plurality of micro-channels which are vertically arranged in an array are arranged on the micro-channel unit plates; the condenser is placed in the water tank, and the condenser is arranged at a height higher than that of the evaporator. The efficient solar heat collection device has the advantages of large effective heat collection area and strong heat transfer capability of the bottom layer heat transfer technology, so that the heat collection efficiency is high, and the performance and the economical efficiency of the whole heat collection system can be effectively improved.)

1. An efficient solar heat collection device, characterized in that: comprises an evaporator, a steam pipeline, a condenser, a liquid pipeline, a liquid storage device and a heat transfer working medium;

the upper end and the lower end of the evaporator are respectively communicated with one end of a steam pipeline and one end of a liquid pipeline, the other end of the steam pipeline is communicated with the condenser, and the other end of the liquid pipeline is communicated with the condenser;

a liquid storage device is arranged at the middle section of the liquid pipeline;

the evaporator comprises a plurality of micro-channel unit plates which are vertically arranged in an array, and a plurality of micro-channels which are vertically arranged in an array are arranged on the micro-channel unit plates;

the condenser is placed in the water tank, and the condenser is arranged at a height higher than that of the evaporator.

2. The efficient solar thermal collection device according to claim 1, wherein: the heat transfer working medium comprises isobutane, dimethyl ether, difluoroethane and nano copper powder.

3. The efficient solar thermal collection device according to claim 2, wherein: the heat transfer working medium is prepared from 30-50% of isobutane, 20-30% of dimethyl ether, 10-20% of difluoroethane and 2-5% of nano copper powder.

4. A high efficiency solar thermal collection apparatus according to claim 3, wherein: the evaporator also comprises an upper frame and a lower frame; the middle part of the upper frame is a cavity, the left end of the upper frame is connected with a steam pipeline, the bottom of the upper frame is provided with a plurality of jacks, the top end of the micro-channel unit plate is inserted into the cavity, and the joint of the micro-channel unit plate and the jacks is sealed; the middle part of the lower frame is a cavity, the left end of the lower frame is connected with a liquid pipeline, the top of the lower frame is provided with a plurality of jacks, the bottom end of the micro-channel unit plate is inserted into the cavity, and the joint of the micro-channel unit plate and the jacks is sealed.

5. The efficient solar energy collection device according to any one of claims 1-4, wherein: the liquid storage device comprises a liquid storage tank, an annular pipe, a liquid feeding pipeline and a liquid discharging pipeline; the liquid storage tank is a tank body with openings at the upper end and the lower end and an inner cavity in the middle; the annular pipe is fixedly arranged at the bottom of the liquid storage tank, the upper liquid pipeline is inserted into the middle of the annular pipe from an opening at the upper end of the tank body, a gap is formed between the outer wall of the upper liquid pipeline and the inner wall of the annular pipe, and an overflow channel is formed in the gap; the lower end of the annular pipe is connected with a liquid discharging pipeline; and a space is arranged between the upper liquid pipeline and the lower liquid pipeline.

6. The efficient solar thermal collection device according to claim 5, wherein: the evaporator adopts a micro-channel brazing process, the condenser adopts a copper pipe and copper fin expansion joint process, and the integral forming adopts a brazing process.

7. The efficient solar thermal collection device according to claim 5, wherein: the section caliber of the micro-channel is rectangular.

8. The efficient solar thermal collection device according to claim 7, wherein: the cross-sectional shape of the microchannel is oval or circular.

9. The efficient solar thermal collection device according to claim 7, wherein: the micro-channel has the dimension specification of 60mm multiplied by 2mm or 32mm multiplied by 2mm or 25.4mm multiplied by 2 mm.

10. The efficient solar thermal collection device according to claim 7, wherein: and a partition plate is arranged at the upper end of the left side of the rightmost micro-channel unit plate of the evaporator.

Technical Field

The invention belongs to the technical field of solar heat collection, and particularly relates to a high-efficiency solar heat collection device.

Background

The world today faces serious energy shortage problems and environmental pollution problems associated with conventional energy use. The utilization of renewable energy is the most effective method of the above two problems, which is a new trend of future social energy utilization. The solar energy is the key focus of attention of renewable energy sources due to the remarkable advantages of environmental protection, abundant resources, safety, harmlessness and the like.

In the development of the solar energy industry, the heat utilization conversion technology of the solar water heater is undoubtedly the most mature, and the industrialization process of the solar water heater is one step ahead of industries such as photovoltaic cells, solar power generation and the like. The solar water heater is a typical green economic industry and a low-carbon economic industry, and has obvious energy-saving benefit and environmental benefit.

Solar energy is not concentrated as fossil energy, so a solar energy absorbing device, a solar collector, is required. The solar heat collector as a device for converting light energy into heat energy is a core component of a solar energy utilization system, and the efficiency and investment cost of the solar heat collector affect the performance and economy of the whole heat collection system. The key factors affecting the heat collection efficiency are the effective heat collection area of the heat collector and the heat transfer capacity of the bottom heat transfer technology.

The existing solar heat collector mainly comprises a vacuum tube type (further divided into a full-glass vacuum tube heat collector, a U-shaped tube-vacuum tube heat collector and a heat tube-vacuum tube heat collector) and a flat plate type (usually in a copper tube aluminum wing structure), the heat collection efficiency is not high, the energy efficiency coefficient (namely the actual heat storage capacity of the heat collector/the radiation heat received by the heat collector) is only 0.5 at most, and the main reasons are that:

all-glass vacuum tube heat collector: the inner tube diameter of the vacuum heat collecting tube is not large, and the effective heat collecting area is not high; the bottom heat transfer technology is water natural convection heat exchange, and the heat exchange coefficient is small;

u-shaped tube-vacuum tube heat collector: the U-shaped tube heat collector is of a copper tube aluminum wing structure, and the rib efficiency is low, so that the effective heat collection area is small; the bottom heat transfer technology is water micro-circulation forced convection heat exchange, and the heat exchange coefficient is not large;

heat pipe-vacuum tube collector: the heat pipe heat collector is of a copper pipe aluminum wing structure, and the rib efficiency is low, so that the effective heat collection area is small; the bottom layer heat transfer technology is a copper water gravity heat pipe, and the heat transfer capacity is small;

a flat plate collector: the flat plate collector is of a copper pipe aluminum wing structure, and the rib efficiency is low, so that the effective heat collection area is small; the bottom heat transfer technology is water natural convection heat exchange or water microcirculation forced convection heat exchange, and the heat exchange coefficient is not large.

In conclusion, the existing solar heat collector has small effective heat collection area and low heat transfer capacity of the bottom layer heat transfer technology, so that the heat collection efficiency is not high, and the performance and the economical efficiency of the whole heat collection system are directly influenced. The invention provides a high-efficiency solar heat collecting device, which aims to solve the problem of low heat collecting efficiency of a heat collector.

For the purposes of understanding the principles of operation of the present application, a highly efficient passive heat transfer technique based on a temperature difference driven self-circulating two-phase fluid loop is described in detail herein. The high-efficiency passive heat transfer technology refers to a heat transfer technology having a high heat transfer capability, requiring no external power (i.e., having high reliability).

The heat exchange carried out by the phase change latent heat is several orders of magnitude larger than the heat transferred by a single relative flow system in a sensible heat mode, and meanwhile, the efficient passive heat transfer technology is usually constructed on the basis of the phase change heat exchange without external power.

The high-efficiency passive heat transfer technology has wide engineering application scenes.

In a heat utilization scene, the method relates to the field of efficient utilization of cold quantity, such as cold conduction of a semiconductor refrigerator, cold conduction of a Stirling refrigerator, LNG (liquefied natural gas) cold quantity transmission, a thawing plate and the like; and the fields of high-efficiency utilization of heat, such as high-efficiency utilization of solar energy, utilization of low-grade heat energy of ground source/water source/air source, utilization of industrial waste heat, thermoelectric generation, IH-like electric cooker inner containers and the like.

In a thermal control scene, the heat dissipation field of electronic devices is related, such as 5G equipment, LEDs, lasers, phased array radar T/R components, CPUs (home computers/servers/mobile phones), IGBTs (frequency converters/photovoltaic inverters/extra-high voltage direct current transmission), semiconductor refrigerators, power batteries, proton exchange membrane fuel cells and the like; and the field of heat exchange of closed spaces, such as base stations, data centers, power cabinets, naval vessel engine cabins and the like.

1. Principle of system

The fundamental idea of strengthening the phase change heat exchange is to increase the phase change heat exchange quantity in unit time, namely, to increase the product of the phase change rate and the phase change latent heat.

On one hand, the whole phase change period covers the whole process of bubble nucleation, bubble growth, bubble detachment and bubble polymerization rise; on the other hand, the phase transition rate and the phase transition latent heat are closely related parameters on the physical aspect, so the improvement of the product of the two parameters needs to be based on the comprehensive analysis of the bubble nucleation and the kinetic characteristics of the phase transition complete cycle.

2. Intensification of the phase transition Rate

2.1 bubble nucleation theory

The vapor bubbles in the boiling process all develop from the core of vaporization (i.e., the tiny vapor bubbles).

The vaporization core of the volume boiling is generated spontaneously, and is caused by fluctuation of the density of each part of the liquid around the average value due to the energy distribution nonuniformity of liquid molecules (according to the molecular motion theory, the energy of each molecule in the liquid is unequal and is distributed according to a certain rule, the nonuniformity of the molecular energy distribution enables the density of each part of the liquid to fluctuate around the average value, temporary local tiny low-density areas are formed due to the random aggregation of activated molecules with larger energy, and the small low-density areas are considered to be tiny vapor bubbles with certain radius and molecular number, which is the formation process of tiny vapor saturated cores in the liquid phase), and the degree of superheat of hundreds is needed.

The vaporization cores of the boiling in the pool are provided outside and are pits, slits and cracks on the heating wall surface (firstly, the liquid in the slits on the heating surface is influenced by much more heating than the same amount of liquid on the plane, and is easy to vaporize to generate steam, and secondly, the gas in the slits is easy to remain, and the gas naturally becomes the vaporization cores for generating bubbles), and the superheat degree is smaller.

As shown in FIG. 1, a container is provided, the bottom surface of which is heated and the upper surface of which is provided with a pressure p_sCorresponds to t_sE.g. with a bubble in the middle, with internal pressure p_vTemperature t_vAmbient fluid corresponds to p_l、t_l。

The conditions under which the bubbles are stable are thermal equilibrium and force equilibrium:

(1) heat balance: t is t_l＝t_v

If t_l＜t_vThen the bubbles transfer heat to the fluid, the steam in the bubbles condenses, and the bubbles collapse;

if t_l＞t_vThen the fluid transfers heat to the vapor bubble, the vapor in the vapor bubble expands, and the vapor bubble grows up.

(2) Force balance: p is a radical of_v-p_l＝2γ/R

If p is_v-p_lIf the pressure difference between two sides of the steam bubble is less than 2 gamma/R, the pressure difference between two sides of the steam bubble is not enough to resist surface tension, steam in the steam bubble is condensed, and the steam bubble is collapsed;

if p is_v-p_lIf the pressure difference is more than 2 gamma/R, the pressure difference of two sides of the steam bubble is more than the surface tension, the steam in the steam bubble expands, and the steam bubble grows up.

For the force balance condition, without considering the static pressure,

p_l＝p_s

then there is a change in the number of,

is the rate of change of pressure on a vapor-liquid two-phase saturation line with temperature, and is constant for a certain pressure. According to the relation between the pressure variation along with the temperature on the saturation line and each parameter of the saturation state, the Clausius-Clabailong provides the following calculation formula:

wherein r is the latent heat of vaporization at saturation temperature, ρ_vAnd rho_lRespectively the density of the vapor and liquid within the bubble. When boiling away from the critical point, ρ_v＜＜ρ_lThen, the above formula is simplified as follows:

the substitution above can result in:

in the case of boiling, the liquid has a maximum superheat at the wall, Δ t ═ t_v-t_s＝t_w-t_sTherefore, the bubble generation condition is satisfied at the wall surface first, and the minimum radius of the wall surface when the bubble nucleus is generated is as follows:

the above formula shows that under certain conditions of p and delta t, the primary bubble nucleus can grow continuously only when the radius of the primary bubble nucleus is larger than the value, and the above formula is the minimum radius of the primary bubble nucleus for standing the foot.

If the vaporized core in the pit can not grow any more, the pit is an inactive pit, i.e., an inactive nucleation site. The vaporization core in the pit grows until the vaporization core grows to expose the opening of the pit, and the radius of a small vapor bubble exposing the opening (which can be approximately regarded as the radius of the opening of the pit) is larger than or equal to the critical radius of the vapor bubble corresponding to the superheat degree of a given liquid, so that the vaporization core can continue to grow, and the pit is called an activation pit, namely an activation nucleation point.

Critical activation nucleation point radius r_mCritical core of vaporization R_min＝2γT_s/rρ_vΔ T, where γ is the surface tension coefficient of the working fluid, T_sIs the saturation temperature at the local pressure, r is the saturation temperatureLatent heat of vaporization ρ_vIs the saturated steam density, Δ t ═ t_w-t_sThe superheat degree of the liquid working medium on the wall surface. The boiling heat exchange intensity (or phase change rate) on the wall surface depends on the total number of activated nucleation points on the heating wall surface, and the size distribution density of pits on the heating wall surface is approximate to a normal distribution function N with the origin as the starting point_rThus total number of activated nucleation sitesI.e. the radius r of the heating wall surface is larger than the critical activation nucleation point_mThe pits of (a) are all activation nucleation sites. Thus, the ways to increase the total number of activated nucleation sites N fall into two categories: firstly, a layer of porous structure is formed on the heating wall surface, and the normal distribution function N is increased_rThe expectation and standard deviation of the activation nucleation sites N can be multiplied by the method; secondly, the phase change working medium is modified at a certain saturation temperature T_sAnd the critical activation nucleation point radius r is reduced under the condition of the wall surface superheat degree delta t_mThis method can increase the total number of activated nucleation sites N by several orders of magnitude.

2.2 gas dynamic theory

The dynamics of the vapor bubble mainly researches the growth and movement rule of the vapor bubble in the liquid.

(1) The bubble grows, the vaporization core formed on the activation nucleation point can grow continuously under various forces. The early stage is a dynamic control stage, the growth of the bubbles is mainly governed by internal thermal inertia force and external surface tension, and the growth rate of the bubbles is very high; the latter is a heat transfer control stage, which is extended for a longer time, with the bubble growth rate being dominated by the heat transfer capacity from the heated liquid to the vapor bubble, the bubble growth rate being slower when the liquid is saturated liquid and faster when the liquid is superheated liquid (discussed at point (2.3)).

(2) Bubble detachment phase, bubble detachment diameter D from heated wall_dThe smaller the detachment frequency f, the higher the phase transition rate. Wherein the bubble detachment diameter D_dThe influencing factors comprise the decreasing of the system pressure and the proportional relation of the power of-1/3 to the gravity accelerationThe negative pressure (pressure lower than atmospheric pressure) is mainly affected by inertia force, etc.; the bubble disengagement frequency f has a relationship

For the kinetic control phase, the index n is 2, and for the heat transfer control phase, the index n is 1/2. Therefore, the bubble separation diameter D can be reduced by modifying the working medium_dMeanwhile, the bubble separation frequency f is increased, and the phase change rate is further enhanced.

(3) In the bubble polymerization rising period, the heat exchange between the bubbles and the liquid in the rising process can reach very high strength (discussed at (2.3)), so that the effective discharge of the bubbles can improve the critical heat flow density under the working condition of high heat flow density, the polymerization and rising movement of the bubbles are very complex, and the bubbles are related to complex gas-liquid two-phase turbulence, and the current research is in the initial stage. But a reasonable bubble discharge structure can be designed to effectively discharge bubbles, thereby strengthening the phase change rate.

The method integrates (1) and (2) nub analysis, modifies the phase change working medium based on the phase change characteristic of the phase change full cycle, and reduces the radius r of the critical activation nucleation point from the physical property level_mTo increase the total number of activated nucleation sites N; reducing the bubble separation diameter D from the physical layer_dIncreasing the bubble separation frequency f to further enhance the phase change rate.

2.3 theory of superheated boiling

In the boiling process, in the heat transfer control stage at the later stage of bubble growth, the bubble growth rate is mainly governed by the heat transfer capacity from liquid to vapor bubble, and the superheat degree of the liquid determines the growth rate of the bubbles; in the rising stage of bubble polymerization, the superheat degree of the liquid determines the heat exchange strength between the vapor bubble and the liquid in the rising process. The bubble growth rate can be enhanced by designing the liquid working medium as superheated liquid.

The boiling state when the temperature of the liquid main body reaches the saturation temperature is saturated boiling, and bubbles can grow slowly in the liquid after being separated from the wall surface; the boiling state that the main body temperature of the liquid is lower than the saturation temperature is supercooling boiling, and the bubbles can disappear in the liquid after separating from the wall surface; the boiling state in which the bulk temperature of the liquid exceeds the saturation temperature is superheated boiling, and bubbles grow rapidly in the liquid after leaving the wall surface. Therefore, the liquid working medium is designed to be an overheat liquid, namely, an overheat boiling state is established.

For heterogeneous boiling on the overheating wall surface, the temperature of the liquid working medium is from the heating of the overheating wall surface, the liquid body is difficult to obtain larger superheat degree in a wall surface heating mode, therefore, the boiling point of the working medium is required to be reduced in a mode of reducing boiling interface pressure, and the overheating boiling is realized under the condition that the liquid working medium obtains heat only through the wall surface heating.

In order to reduce the boiling interface pressure, a phase change cycle must be constructed. The complete two-phase fluid loop comprises an evaporator, a steam pipeline, a condenser, a liquid pipeline and a liquid storage device, the two-phase fluid loop is driven by temperature difference to carry out self circulation, and the circulating power can be gravity or capillary force.

(1) The pressure-temperature diagram of a two-phase fluid loop thermodynamic cycle when the cycle power is gravity is shown in figure 2.

Wherein the content of the first and second substances,

1: an evaporation interface within the evaporator;

1 → 2: the steam is continuously heated in the evaporator to form superheated steam-delta P_eva；

2 → 3: steam flows in the steam line-delta P_vap；

3 → 4: cooling steam in the condenser;

4 → 5: condensing steam in the condenser;

5 → 6: supercooling of liquid in condenser-total of the three items Δ P_con；

6 → 8: liquid flowing in the liquid pipe-delta P_liq；

7: a reservoir;

gravity pressure difference delta P as circulating power_gTotal flow pressure loss Δ P_total＝ΔP_eva+ΔP_vap+ΔP_con+ΔP_liq。

(2) When the circulation power is capillary force, the pressure-temperature diagram of thermodynamic circulation of two-phase fluid loop is similar to the above diagram, and the interior of circulation also needs to be increasedAdding the flow pressure difference Δ P in the wick_wic。

Corresponding to capillary pressure difference DeltaP as circulation power_cTotal flow pressure loss Δ P_total＝ΔP_eva+ΔP_vap+ΔP_con+ΔP_liq+ΔP_wicIf the evaporator is in the antigravity working condition, the capillary wick correspondingly provides the total flow resistance delta P_totalAnd gravity head Δ P_gThe circulating power of (2). During thermal equilibrium of the system, the radius of the meniscus in the evaporator is automatically adjusted to match the flow resistance of the fluid circuit, which is the heat transfer capacity limit of the system when the radius of the meniscus is equal to the capillary aperture.

Under any circulating power condition, the boiling interface temperature of the two-phase fluid loop is T₁Pressure of P₈The boiling environment at this time is lower than the saturation pressure + the saturation temperature, that is, the superheated boiling state.

In an overheat boiling state, the liquid working medium is overheat liquid, and in a heat transfer control stage at the later stage of bubble growth, the overheat liquid transfers heat to the vapor bubble in a large amount, and the growth rate of the bubble is high; in the bubble polymerization rising stage, the superheated liquid also transfers a large amount of heat to the bubbles, and the heat exchange strength between the bubbles and the liquid is higher, so that the phase change rate is enhanced.

By integrating the summary analysis of (2.1) - (2.3), the critical activation nucleation point radius r can be reduced from the physical property level by modifying the phase change working medium_mTo increase the total number N of activation nucleation points and to decrease the bubble separation diameter D from the physical aspect_dIncreasing the bubble separation frequency f to ensure that the heat transfer working medium has higher phase change rate in the bubble nucleation and bubble separation process of the phase change full period, thereby strengthening the phase change rate; the vapor-liquid separation is realized by designing a two-phase fluid loop and by a capillary structure, a liquid pool structure and a height difference structure, so that the phase change interface pressure of the heat transfer working medium in the evaporator is reduced, a hot boiling state is further established, the heat exchange strength of the vapor heat transfer working medium and the liquid heat transfer working medium is increased in the process of bubble growth and bubble polymerization in the phase change full period, and the phase change rate is further enhanced.

3. Intensification of latent heat of phase change

The latent heat of phase change refers to the heat absorbed or released by the working medium of unit mass in the phase change process when the temperature is unchanged. The latent heat of phase change comprises an internal work part for overcoming the interaction potential energy between molecules to do work and an external work part for overcoming the atmospheric pressure to do work. The internal work is a main component, and the potential energy of intermolecular interaction includes intermolecular forces such as van der waals force and hydrogen bond. Van der waals' force is a weakly basic electrical attraction, also called intermolecular force, that exists between neutral molecules or between inert gas atoms; hydrogen bonds exist between nonmetal atoms with large electronegativity and small atomic radius such as F, O and N and hydrogen, and molecules with hydrogen bonds include HF and H₂O and NH₃And the like.

The intermolecular forces of working media with similar physical shapes in the same temperature zone are not different greatly, for example, water, ethanol and acetone are all liquid at normal temperature and normal pressure, and the intermolecular forces are different by only a few times. That is, the latent heat of phase change between different working mediums in a certain temperature area is usually only several times different.

Therefore, when the product of the phase change rate and the phase change latent heat is comprehensively considered in the enhanced phase change heat exchange, the phase change rate enhanced by several orders of magnitude can be realized, and the phase change latent heat with the difference of several times in the same temperature region is considered.

4. System components

The high-efficiency passive heat transfer technology based on the temperature difference driven self-circulation two-phase fluid loop is designed by combining the analysis of the enhanced phase change rate and the enhanced phase change latent heat, mainly comprises an evaporator, a steam pipeline, a condenser, a liquid pipeline, a liquid storage device and a modified heat transfer working medium, the system is a closed loop, the product of the phase change rate and the phase change latent heat of the system is large, the phase change heat exchange capacity is strong, and the high-efficiency passive heat transfer technology is ideal.

Disclosure of Invention

The invention aims to provide a high-efficiency solar heat collecting device to solve the problem that the heat collecting efficiency of a heat collector is not high due to small effective heat collecting area and low heat transfer capability of a bottom layer heat transfer technology of the conventional solar heat collector.

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

a high-efficiency solar heat collection device comprises an evaporator, a steam pipeline, a condenser, a liquid pipeline, a liquid storage device and a heat transfer working medium; the device as a whole forms a two-phase fluid loop;

the upper end and the lower end of the evaporator are respectively communicated with one end of a steam pipeline and one end of a liquid pipeline, the other end of the steam pipeline is communicated with the condenser, and the other end of the liquid pipeline is communicated with the condenser;

a liquid storage device is arranged at the middle section of the liquid pipeline;

the evaporator comprises a plurality of micro-channel unit plates which are vertically arranged in an array, and a plurality of micro-channels which are vertically arranged in an array are arranged on the micro-channel unit plates;

the evaporator adopts a micro-channel brazing process, the condenser adopts a copper pipe and copper fin expansion joint process, and the integral forming adopts a brazing process.

Preferably, the evaporator further comprises an upper frame and a lower frame; the middle part of the upper frame is a cavity, the left end of the upper frame is connected with a steam pipeline, the bottom of the upper frame is provided with a plurality of jacks, the top end of the micro-channel unit plate is inserted into the cavity, and the joint of the micro-channel unit plate and the jacks is sealed. The middle part of the lower frame is a cavity, the left end of the lower frame is connected with a liquid pipeline, the top of the lower frame is provided with a plurality of jacks, the bottom end of the micro-channel unit plate is inserted into the cavity, and the joint of the micro-channel unit plate and the jacks is sealed.

Preferably, the liquid storage device comprises a liquid storage tank, an annular pipe, an upper liquid pipeline and a lower liquid pipeline; the liquid storage tank is a tank body with openings at the upper end and the lower end and an inner cavity in the middle; the annular pipe is fixedly arranged at the bottom of the liquid storage tank, the upper liquid pipeline is inserted into the middle of the annular pipe from an opening at the upper end of the tank body, a gap is formed between the outer wall of the upper liquid pipeline and the inner wall of the annular pipe, and an overflow channel is formed in the gap; the lower end of the annular pipe is connected with a liquid discharging pipeline; and a space is arranged between the upper liquid pipeline and the lower liquid pipeline.

The condenser is placed in the water tank, and the condenser is higher than the evaporator in arrangement height; the liquid pipeline is directly communicated to the evaporator after penetrating through the middle of the liquid storage device, the volume of the liquid working medium is increased when the working temperature is increased, and redundant liquid working medium overflows into the liquid storage device through the annular pipe on the outer side of the liquid pipeline.

Preferably, the cross-sectional caliber of the microchannel is rectangular, and the dimension specification is 60mm × 2mm (width × thickness), 32mm × 2mm, 25.4mm × 2mm and the like;

the sizes and volumes of functional parts of the evaporator, the steam pipeline, the condenser, the liquid pipeline and the liquid storage device need to be matched and designed based on the technical requirements of working medium physical properties and heat transfer capacity of a working temperature zone.

Preferably, the heat transfer working medium is prepared from 30-50% of isobutane, 20-30% of dimethyl ether, 10-20% of difluoroethane and 2-5% of nano copper powder;

the system working medium is in a vapor-liquid two-phase state in a working temperature region and has a critical activation nucleation point radius r_mSmall, bubble-free diameter D_dSmall size, high bubble separation frequency f and high phase change rate.

The working process is as follows:

the evaporator in the two-phase fluid loop absorbs solar heat, the internal liquid working medium is evaporated at a phase change interface, the vapor working medium is transmitted to the condenser through a vapor pipeline, the vapor working medium in the condenser is firstly cooled, then condensed and finally subcooled, the liquid working medium is transmitted to the liquid storage device through a liquid pipeline, and the liquid working medium in the liquid storage device is supplemented to the evaporator for continuous evaporation. The circulating power of the fluid loop is gravity, and the working medium in the two-phase fluid loop flows along the path of the evaporator → the condenser in a self-circulation mode under the driving of temperature difference.

The working principle is as follows:

the bottom layer heat transfer technology is an efficient passive heat transfer technology based on a temperature difference driven self-circulation two-phase fluid loop, and achieves an efficient heat transfer effect by strengthening phase change heat exchange.

The fundamental idea of strengthening the phase change heat exchange is to increase the phase change heat exchange quantity in unit time, namely, to increase the product of the phase change rate and the phase change latent heat. On one hand, the whole phase change period covers the whole process of bubble nucleation, bubble growth, bubble detachment and bubble polymerization rise; on the other hand, the phase transition rate and the phase transition latent heat are closely related parameters on the physical aspect, so the improvement of the product of the two parameters needs to be based on the comprehensive analysis of the bubble nucleation and the kinetic characteristics of the phase transition complete cycle.

By modifying the phase change working medium, the critical activation nucleation point radius r is reduced from the physical property level_mTo increase the total number N of activation nucleation points and to decrease the bubble separation diameter D from the physical aspect_dIncreasing the bubble separation frequency f to ensure that the heat transfer working medium has higher phase change rate in the bubble nucleation and bubble separation process of the phase change full period, thereby strengthening the phase change rate; by designing a two-phase fluid loop and realizing vapor-liquid separation through a height difference structure, the phase change interface pressure of the heat transfer working medium in the evaporator is reduced, and further a hot boiling state is established, so that the heat exchange strength of the vapor heat transfer working medium and the liquid heat transfer working medium is increased in the processes of bubble growth and bubble polymerization in the phase change full period, and the phase change rate is further enhanced.

When the two-phase fluid loop works, the evaporator 1 in the two-phase fluid loop absorbs heat of a heat source, an internal liquid working medium is evaporated at a phase change interface, a vapor working medium is transmitted to a condenser through a vapor pipeline, the vapor working medium in the condenser is firstly cooled, then condensed and finally supercooled, the liquid working medium is transmitted to a liquid storage device through a liquid pipeline, and the liquid working medium in the liquid storage device is supplemented to the evaporator 1 for continuous evaporation.

The invention has the beneficial effects that:

the system is a closed loop, the product of the phase change rate and the phase change latent heat of the system is large, the phase change heat exchange capacity is strong, and the system is an ideal high-efficiency passive heat transfer technology.

Drawings

FIG. 1 is a background art illustration;

FIG. 2 is a background art illustration;

FIG. 3 is a partial schematic view of the high efficiency solar thermal collector of the present invention;

FIG. 4 is a schematic cross-sectional view of a microchannel of a high efficiency solar thermal collector of the present invention;

FIG. 5 is a schematic view of the reservoir of the high efficiency solar thermal collector of the present invention;

FIG. 6 is a schematic structural view of another embodiment of the high efficiency solar thermal collector of the present invention;

fig. 7 is a partially enlarged view of fig. 6.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 3-5, a high-efficiency solar heat collection device comprises an evaporator 1, a steam pipeline 2, a condenser 3, a liquid pipeline 4, a liquid reservoir 5 and a heat transfer working medium 6;

the upper end and the lower end of the evaporator 1 are respectively communicated with one end of a steam pipeline 2 and one end of a liquid pipeline 4, the other end of the steam pipeline 2 is communicated with a condenser 3, and the other end of the liquid pipeline 4 is communicated with the condenser 3;

a liquid storage device 5 is arranged at the middle section of the liquid pipeline 4; the device as a whole forms a two-phase fluid loop;

the evaporator 1 comprises a plurality of micro-channel unit plates 11 which are vertically arranged in an array, and a plurality of micro-channels 12 which are vertically arranged in an array are arranged on the micro-channel unit plates 11;

the evaporator 1 adopts a micro-channel brazing process, the condenser 3 adopts a copper pipe and copper fin expansion joint process, and the integral forming adopts a brazing process.

Preferably, the evaporator 1 further comprises an upper frame 13 and a lower frame 14; the middle part of the upper frame 13 is a cavity, the left end of the upper frame is connected with the steam pipeline 2, the bottom of the upper frame is provided with a plurality of jacks, the top end of the micro-channel unit plate 11 is inserted into the cavity, and the joint of the micro-channel unit plate 11 and the jacks is sealed. The middle part of the lower frame 14 is a cavity, the left end of the lower frame is connected with the liquid pipeline 4, the top of the lower frame is provided with a plurality of jacks, the bottom end of the micro-channel unit plate 11 is inserted into the cavity, and the joint of the micro-channel unit plate 11 and the jacks is sealed.

Preferably, the liquid reservoir 5 comprises a liquid storage tank 51, an annular pipe 52, an upper liquid pipeline 53 and a lower liquid pipeline 54; the liquid storage tank 51 is a tank body with openings at the upper end and the lower end and an inner cavity at the middle part; the annular pipe 52 is fixedly arranged at the bottom of the liquid storage tank 51, the upper liquid pipeline 53 is inserted into the middle of the annular pipe 52 from the opening at the upper end of the tank body and penetrates into the middle of the annular pipe 52, and a gap is formed between the outer wall of the upper liquid pipeline 53 and the inner wall of the annular pipe 52 and forms an overflow channel; the lower end of the annular pipe 52 is connected with a lower liquid pipeline 54; and a space is arranged between the upper liquid pipeline 53 and the lower liquid pipeline 54.

The condenser 3 is placed in the water tank, and the condenser 3 is arranged higher than the evaporator 1; the liquid pipeline 4 is directly communicated with the evaporator 1 after penetrating through the middle of the liquid storage device 5

When the temperature rises, the volume of the liquid working medium is increased, and the redundant liquid working medium overflows into the liquid storage device 5 through the annular pipe 52 on the outer side of the liquid pipeline 4.

Preferably, the cross-sectional caliber of the microchannel 12 is rectangular, and the dimension specification is 60mm × 2mm (width × thickness), 32mm × 2mm, 25.4mm × 2mm, and the like;

the sizes and the volumes of all functional parts of the evaporator 1, the steam pipeline 2, the condenser 3, the liquid pipeline 4 and the liquid storage device 5 need to be matched and designed based on the technical requirements of working medium physical properties and heat transfer capacity of a working temperature zone.

Preferably, the heat transfer working medium 6 is prepared from 30-50% of isobutane, 20-30% of dimethyl ether, 10-20% of difluoroethane and 2-5% of nano copper powder; or the heat transfer working medium 6 can be prepared by 30 to 50 parts of isobutane, 20 to 30 parts of dimethyl ether, 10 to 20 parts of difluoroethane and 2 to 5 parts of nano copper powder by weight.

Preferably, the cross-sectional shape of the microchannel 12 may be an ellipse or a circle.

As shown in fig. 6 and 7, the solar heat collecting device can also be made into an integrated configuration, the partition 7 is arranged at the upper left end of the rightmost microchannel unit plate 11 of the evaporator 1, and the evaporator 1 can be partially arranged into the liquid pipeline 4 in a manner of being isolated by the partition 7.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.