Background technology
Modern Refrigeration Technique is as a science, be to grow up in 19th-century mid-term and later stage, before this, trace back to human ancestors, people have understood cold utilization and simple artificial cooling very early: do cold storage chamber with the cellar, with the history of existing 5000 of spring cooling storeroom.
Behind the twentieth century, Refrigeration Technique has had larger development: domestic refrigerator in 1910 comes out, and 1917 begin to put on market as commodity in the U.S..Nineteen thirty, the appearance of freon refrigeration working medium and the use of freon refrigerator bring new change to Refrigeration Technique.Nineteen seventies, people have carried out a large amount of research to mixed working fluid, and bring into use azeotropic mixed working medium, for new road has been opened up in the development of vapour compression refrigerator.Refrigeration Technique develops into today, and each department of national economy is expanded, is penetrated into to the temperature from preserving food and regulating certain space, and has had more closely with daily life and to contact.The thermoelectric (al) cooling device claims again semiconductor cooler, and it does not have complicated running frame for movement, utilizes extraordinary semi-conducting material to form P-N knot, and logical upper direct current just can freeze, and refrigeration rapidly, changes the Power supply direction, can transfer to from refrigeration heating.Its these characteristics provide application for new and high technology, an important branch as Refrigeration Technique, countries in the world pay much attention to and have organized state's development such as fairly large explained hereafter, research, the particularly U.S., Russia, Germany, France, Japan very fast to this.
1821, first found difference of temperature Germany scientist Seebeck (Seebeck), namely in the open circuit that is comprised of two kinds of different conductors, if there is temperature difference in two nodes of conductor, will produce electromotive force E in the open circuit
0, Seebeck effect that Here it is.The electromotive force that is produced by Seebeck effect claims thermoelectromotive force.Why being called thermoelectric, is because people recognized that the deflection of compass caused owing to the temperature difference makes the loop generation current afterwards.
Approximately after 12 years, when the Pa Er note (Peltier) of France finds that electric current flows through the interface of two kinds of different conductors, will obtain or emit heat from the external world, Here it is peltier effect.The heat flow that is produced by peltier effect claims Pa Er note heat.But he do not recognize he discovery essence and and Seebeck effect between relation.Until 1838, the essence of Pa Er note phenomenon has just given correct explanation by Lenz.
1855, the relation of Seebeck effect and peltier effect is found and set up to Thomson, and foretold the third difference of temperature, i.e. the existence of Thomson effect; He was again from experimentally having proved this effect afterwards.The discovery of Thomson relation has played great impetus to thermo-electricity and thermodynamics development afterwards.
Approximately the flying of the former Soviet Union in 1949 proposed the theory about semiconductor temperature difference electric, many work aspect practical application, have been done simultaneously, nineteen fifty-three is developed thermoelectric domestic refrigerator model machine, and with published " semiconductor heat electric device and thermoelectric cooling " book in 1956, can think the beginning of the practical electric equipment products of thermoelectric transition effects, development after this is very rapid.But comparing with the development of other semiconductor devices, but is slowly.The maximum restriction factor that affects the application of thermoelectric transfer power is that their conversion efficiency is too low, is difficult to compare with traditional power converter, and research once receded to a low ebb.Yet nineteen fifty-nine Zener doctor foretells that thermoelectric material can realize being similar to freon compression-type refrigeration or the such performance of turbogenerator, and this has injected cardiotonic, excitant for undoubtedly the industrialization of thermoelectric device.Upper hundred professional factories have just appearred in the initial stage sixties quickly, and also greatly having excited scientists is to seek higher figure of merit material and enthusiasm aspect basic theory and new material exploration.People conduct in-depth research the breast binary take bismuth telluride (Bi2Te3) as the basis, breast ternary alloy system.However, recent decades material property raising but very slow.Comparatively speaking, the preparation technology of device then is gradually improved, and product formation standardization, seriation are produced and formed scale.
But as a class solid energy transducer, its advantage is again unrivaled, and along with the continuous expansion of application and the raising of level, the advantage of all kinds of thermoelectric devices that reach its maturity is more paid attention to, and is applied in numerous fields.These characteristics comprise movement-less part, noiseless, easily microminiaturized, be easy to control, reliability is high, the life-span is long etc., the reliability height is its major advantage, usually need not to adopt other forms of heat-transfer working medium in the design, therefore the problem with regard to having avoided often running in many device fabrications such as vibration, pressure, sealing system.Many be not that thermoelectric has advantages of not to be replaced take energy conversion efficiency as the main application scenario of considering factor.In high today of protection of the environment cry day, the thermoelectric switching device again free from environmental pollution because of it, can utilize the potentiality of used heat and regenerative resource further to be paid attention to.Last century Mo, high temperature superconducting materia and the application thereof of flourish superconducting transition temperature more than liquid nitrogen temperature can be rated as the most great scientific and technological achievement, for adapting to the very wide demand to cryogenic conditions of this following application prospect, thermoelectric cooling is also obtaining such low temperature as an important content.This effort comprises the material that further selection is possible.
The prophesy of Zener fails to realize so far regrettably.And up to the present, also be difficult to determine and can realize, that is to say, from the angle of energy conversion efficiency, thermoelectric cooling can't be comparable with traditional pattern steam compression type refrigeration or absorption refrigeration merely.
Why fail to obtain important breakthrough, its basic reason is not have correct refrigerating theory to instruct, do not recognize that the high efficiency application that the thermoelectric conversion equipment really suits is the low temperature field that is lower than environment temperature, be the cold electric conversion field of cold energy, and fail to find the high effective model of cold energy generation.If effectively address the above problem, thermoelectric material can realize being similar to the such performance of freon compression-type refrigeration fully, realizes Zener doctor's prophesy, and the present invention namely is the exploration to the theory and practice of the problems referred to above.
The main foundation of tradition refrigerating theory is thermodynamics, namely adopts with the contrary cycle analysis kind of refrigeration cycle process in the Kano of the temperature difference, and the economic index of kind of refrigeration cycle is coefficient of refrigerating performance, the ratio of the income that obtains exactly and the cost that expends, and with atmospheric temperature T
0With temperature be T
CAll kind of refrigeration cycle between the low-temperature heat source (such as freezer), with the coefficient of refrigerating performance of reverse Carnot cycle for the highest:
ε in the following formula
cBe coefficient of refrigerating performance, q
2Be the refrigerating capacity of circulation, w
0Be the net work that circulates and consume.
In fact, the Kano is in the paper of " about thermodynamic opinion ", and the conclusion that draws is: " all heat engines of between the constant temperature thermal source of two different temperatures, working, with the efficient of reversible heat engine for the highest." namely being referred to as Carnot's theorem by the descendant, the thermal efficiency of putting the Carnot cycle that draws by the desirable equation of gas state in order is:
The temperature T of the high temperature heat source in the formula (2)
1With the temperature of low-temperature heat source be T
2All be higher than atmospheric temperature T
0, and can draw following some important conclusion:
1) thermal efficiency of Carnot cycle only is decided by the temperature of high temperature heat source and low-temperature heat source, and namely the temperature during the working medium heat absorption and release improves T
1And T
2, can improve the thermal efficiency.
2) thermal efficiency of Carnot cycle can only must not equal 1 less than 1, because T
1=∞ or T
2=0 all can not realize.In other words, though in cycle engine in the ideal case, also heat energy all can not be converted into mechanical energy, the thermal efficiency is certainly more impossible greater than 1.
3) work as T
1=T
2The time, thermal efficiency of cycle equals 0, it shows, in the system of equalized temperature, heat energy can not be converted into mechanical energy, heat energy produces power must have temperature difference as thermodynamic condition, thereby has verified that the machine by the single source continuous doing work does not manufacture, or perpetual motion machine of the second kind is non-existent.
4) Carnot cycle and thermal efficiency formula thereof are significant in thermodynamic (al) development.At first, it has established the theoretical foundation of the second law of thermodynamics; Secondly, the research of Carnot cycle has been pointed out direction for improving the various heat power machine thermals efficiency, closely may improve the endothermic temperature of working medium and reduce as far as possible the exothermic temperature of working medium, and heat release is carried out when can unearned minimum temperature being atmospheric temperature approaching.What propose in the Carnot cycle utilizes adiabatic compression to improve the method for gas endothermic temperature, still generally adopts in the heat power machine take gas as working medium so far.
5) limit point of Carnot cycle is atmospheric temperature, and to being lower than the process of refrigerastion circulation of environment temperature, Carnot cycle does not provide clear and definite answer.
Because the imperfection of coefficient of refrigerating performance, the scholar of lot of domestic and foreign studies it, and has proposed Perfect Suggestions.Ma Yitai etc. in the analysis of the research of the Energy Efficiency Standard of heat pump product and cycling hot mechanics sophistication " refrigeration with " in conjunction with Curzon and Ahlborn the analysis that this irreversible procedure introducing thermodynamic cycle of different transfer of heat is arranged, and the inspiration of the Finite-Time Thermodynamics that creates thus, in conjunction with the CA cycle efficieny, proposed the thermodynamics sophistication of CA direct circulation, made the efficiency research of refrigeration and heat pump product that progress to a certain degree arranged.
But use thermodynamic (al) basic theories can not make succinctly kind of refrigeration cycle, understand, explain intuitively.Einstein once did evaluation to classical thermodynamics: " a kind of theory, its prerequisite is simpler, and related things is more, and its accommodation is more extensive, and it gives people's impression just more deep." to the theoretical explanation of refrigerating field, also answer this advantage of to succeed and develop.
Therefore, really find the correct theoretical foundation of kind of refrigeration cycle, propose new Thermoelectricity refrigerating apparatus in this theoretical foundation and also can be applied in the reality, the cold conversion efficiency of Effective Raise electricity becomes the difficult point that refrigeration technology field is studied.
Summary of the invention
Purpose of the present invention be exactly be applied to freeze for solving Carnot's theorem, imperfection that the thermoelectric replacement theory is analyzed, proposition is cold theory of mechanics and is used for Guiding Practice corresponding to the refrigerating theory of thermodynamic argument: be referred to as low-temperature receiver for the environment that is lower than atmospheric temperature, with respect to the thermal source that is higher than environment temperature; Corresponding to heat energy, heat, corresponding cold energy, cold concept are proposed; The formula of the power conversion in the conversion of proposition cold energy and law of conservation, cold mechanics second law, cold analysis of Available Energy; Corresponding to the available energy of heat "
", unavailable energy " cinder ", understanding to heat, cold water intaking fire, the available energy for cold is named as " cold ripples ", cold is called " cold Jin " to the unavailable energy of environment transmission, " Jin " pronunciation is " using up ".
Conversion of Energy and law of conservation are followed in the transmission of cold energy in the process of refrigerastion.
For describing direction, condition and the limit that cold transmits in the process of refrigerastion, propose cold mechanics second law: the essence of cold mechanics second law is the same with the essence of the second law of thermodynamics, follow equally " can matter decline demote principle ", being multi-form cold energy, is the difference that " matter " is arranged in the ability of changing successfully amount; Even the cold energy of same form, its existence are not simultaneously, its transfer capability is also different.The real process that all cold energy transmit, the direction that always descends towards energy matter is carried out, and all cold energy are always from being sent to the conversion of atmospheric environment direction.Cold energy can matter the raising process can not be automatically, carry out individually, the process that the process of the raising of an energy matter must be accompanied by the decline of another energy matter occurs simultaneously, this process that can matter descends is exactly to realize the compensation condition of necessity that can the matter elevation process, namely with can matter drop to cost, by way of compensation promote can the matter elevation process realization.In real process, as the energy matter decline process of cost, must be enough to compensate the process that energy matter raises, the universal law that must descend to satisfy total energy matter.Therefore, under the compensation condition that certain energy matter descends, the process that energy matter raises must have a theoretical limit the highest.Only under the ideal conditions of completely reversibility, just can reach this theoretical limit, at this moment, can just in time equal the offset that energy matter descends by the matter lift-off value, make total energy quality guarantee hold constant.As seen, reversible process is the energy matter conservative process of equidimensional ideal; Energy matter total in irreversible procedure must descend; May realize in no instance making the process of the total energy matter rising of isolated blob.Here it is can matter declines and demotes the physical connotation of principle, is the essence of cold mechanics second law, also is the essence of the second law of thermodynamics, and it has disclosed, and all Macroscopic Process are mandatory, the objective law of relative process travel direction, condition and limit.
The fundamental formular of describing cold mechanics second law is:
In the formula (3), Tc2<Tc1<To, To is environment temperature, is Kelvin's thermometric scale.
Relative environment temperature To, the maximum cold efficient of low-temperature receiver under Tc1, Tc2 is:
Be assumed to be q
2The refrigerating capacity of circulation, w
0Be the net work that circulates and consume, then when sink temperature is Tc1:
Equally, when sink temperature is Tc2:
Be not difficult to find out to (7) from formula (4), the efficient of cold mechanics is between 0 to 1, because irreversibility inevitable in the real process, kind of refrigeration cycle efficient is less than 1; When environment temperature To determined, sink temperature was lower, inputted same merit, and the refrigerating capacity of acquisition is more, thereby had indicated direction for constructing the i.e. cold efficient conversion of electricity of new kind of refrigeration cycle.
Need to prove:
(1) cold is spontaneously to transmit from low temperature cold source to environment temperature;
(2) can not pass to cold lower low-temperature receiver and not cause other variations from low temperature cold source;
When (3) cold was from the low temperature cold source transmission to environment, the merit amount that exchanges with the external world was w
0, wherein comprise the idle work p that environment is done
0(V
0-V
c), p
0Be atmospheric pressure, Vo is the volume under the environment temperature, and Vc is the volume under the sink temperature, and the maximum reversible useful work that can do is:
When (4) cold is from the low temperature cold source transmission to environment, to the cold Jin of environment transmission be:
Idle work to the environment transmission is: p
0(V
0-V
c)
When (5) cold energy transmitted to environment temperature, outwards the optimum pattern of acting was for adopting the thermal generator of Seebeck (Seebeck) effect, i.e. cold power generator; When electric energy was changed to cold energy, best conversion pattern was to adopt the temperature-difference refrigerating machine of peltier effect;
(6) energy must, also must meet Conversion of Energy and law of conservation in the cold mechanics;
(7) by using for reference the design of Finite-Time Thermodynamics, can develop the cold mechanics basic theories of finite time;
(8) can not break away from the grade that environment is estimated cold.
(9) use for reference Curzon and Ahlborn there being this irreversible procedure of different transfer of heat to introduce the analysis thinking of thermodynamic cycle, and the inspiration of the Finite-Time Thermodynamics that creates thus, in conjunction with the CA cycle efficieny, according to the reduced state principle, the improvement formula of the cold mechanics of finite time is proposed:
(10) cold mechanics and thermodynamics are two branches in the energetics, the one side that had both had opposition, exist again unified one side: in the cryogenic refrigeration circulation, under the prerequisite of following cold mechanics second law, the Rankine cycle principle is followed again in the cyclic process of the cold-producing medium working medium of constructing under low temperature environment, again get back to again Carnot law, just meet the principle that has the positive and negative sun to help mutually in the moon in the Chinese traditional aesthetics.
Can find out from the above-mentioned theory basis, the cold mechanics of proposition has the theoretical frame system with the thermodynamics symmetry, meets the basic principle of the aesthetics of science, i.e. symmetry principle.
Based on above-mentioned basic principle, the present invention proposes to be different from traditional Thermoelectricity refrigerating apparatus, use for reference the backheat Cyclical Theory in the power cycle, make up the reflux refrigeration cycle of cold power closed circuit, thereby be used for to realize the cold conversion of efficient electric, make the theory of proposition become really can Guiding Practice preliminary perfect system.
The objective of the invention is to realize by following measures:
A kind of thermoelectric refrigerator step cooling cold-storage device, this device comprises Thermoelectricity refrigerating apparatus utmost point low-temperature level kind of refrigeration cycle, low-temperature level kind of refrigeration cycle and charge cycle, it is characterized in that:
Described Thermoelectricity refrigerating apparatus utmost point low-temperature level kind of refrigeration cycle, refer to by DC plant device 4-4 thermoelectric couple group input dc power: from cold-producing medium basin 1 liquid refrigerant 2 out, after cryogenic liquid pump 3 superchargings, send into thermoelectric refrigerator 4, the DC plant device 4-4 of thermoelectric refrigerator 4 is to thermoelectric couple group 4-1 input dc power, cold-producing medium by coolant channel 4-2 obtains a part of cold energy that thermoelectric couple group 4-1 uses electric energy conversion, the temperature of cold-producing medium is reduced, the heat that the electric energy process of refrigerastion produces passes to the cold-producing medium 9 that passes through among the backheat passage 4-3 by thermoelectric couple group 4-1, send into cold from thermoelectric refrigerator 4 cold-producing medium out and use unit 5, enter cold-producing medium basin 1 through choke valve 6 again, thereby form thermoelectric refrigerator 4 utmost point low-temperature level refrigeration cycles;
Described Thermoelectricity refrigerating apparatus low-temperature level kind of refrigeration cycle, refer to from cold-producing medium basin 8 liquid refrigerant 9 out, send into back cooler 11 through cryogenic liquid pump 10, the backheat passage 4-3 of thermoelectric refrigerator 4, absorb the heat that thermoelectric couple group 4-1 process of refrigerastion produces, send into again low-temperature level cold user 12, form refrigerant superheat steam 13, enter decompressor 14 expansion actings and drag braking equipment 18, return cooler 11 from decompressor 14 exhaust steam 15 warps out, pipeline 16 backflows, choke valve 17, get back to cold-producing medium basin 8, thereby form the low-temperature level kind of refrigeration cycle process of thermoelectric refrigerator 4.
Described Thermoelectricity refrigerating apparatus charge cycle, refer to from cold-producing medium basin 1 liquid refrigerant 2 out, after cryogenic liquid pump 3 superchargings, send into thermoelectric refrigerator 4, the direct current conversion equipment 4-4 of thermoelectric refrigerator 4 is to thermoelectric couple group 4-1 input dc power, cold-producing medium by coolant channel 4-2 obtains a part of cold energy that thermoelectric couple group 4-1 uses electric energy conversion, the temperature of cold-producing medium is reduced, the heat that the electric energy process of refrigerastion produces passes to the cold-producing medium 9 that passes through among the backheat passage 4-3 by thermoelectric couple group 4-1, use the by-pass line 7 of unit 5 directly to enter cold-producing medium basin 1 from thermoelectric refrigerator 4 cold-producing medium out through cold, cold-producing medium basin 1 is equivalent to regenerator at this moment, thereby forms the charge cycle loop of Thermoelectricity refrigerating apparatus.
Described thermoelectric refrigerator 4 comprises thermoelectric couple group 4-1, coolant channel 4-2, backheat passage 4-3 and direct current input unit 4-4.
Described thermoelectric couple group 4-1 adopts one or more groups series, parallel or series-parallel system to connect; Every group of thermoelectric couple has multistage thermoelectric couple, adopts series, parallel or series-parallel connection pattern.
The characteristics of the multistage thermoelectric couple of tandem type are that operating current at different levels is identical, level with grade between the junction need the conduction cooling layer (generally adopting two potsherds that are parallel to each other etc. of anodised aluminium or conduction cooling better performances and electric insulation to separate) of one deck electric insulation, require the conduction cooling coefficient of conduction cooling layer large, temperature difference loss is reduced; From current path, all thermoelectric couples are series connection, and from the cold path, all thermoelectric couples then are in parallel.
The characteristics of the multistage thermoelectric couple of parallel connection type are except operating current is large, because inter-stage should conduct electricity by conduction cooling again, so do not need electric insulation layer, also stepless temperature difference.When the temperature difference that requires and load were identical with tandem type thermoelectric couple group, parallel connection type was less than tandem type power consumption, but line design is complicated.
Each thermoelectric couple is connect by a P type thermoelement and N-type thermoelement and forms, connect direct current after, will produce the temperature difference and energy in the joint and shift: electric current is by P → N in thermoelectric couple, and temperature rises and heat release is called the hot junction; Electric current is from N → P, and drop in temperature and heat absorption are called cold junction.Some thermoelectric couple is together in series at circuit, and in parallel aspect heat transfer, just consisted of common thermoelectric refrigerator.
The P type can select to bear the superconductor of ternary material such as bismuth telluride-antimony telluride solid solution alloy or P type; But N-type bismuth telluride-bismuth selenide solid solution alloy or N-type superconductor.Add the ternary bismuth selenide such as the P type on the basis of bearing binary system bismuth telluride-antimony telluride, n type material adopts binary solid solution, and can adopt weight ratio is the bismuth selenide of 93% bismuth telluride+7%.
According to different temperature ranges, select the high efficiency thermoelectric couple group with the interval coupling of variations in temperature.
Accompanying drawing 1 provides a kind of cross-sectional view of single-stage temperature-difference refrigerating device, among the figure: 1-temperature upper side, 2-output, the 3-temperature is than downside; Accompanying drawing 2 provides two kinds of temperature-difference refrigerating device structural representations, and Fig. 2 (a) is that the thermoelectric couple inter-stage is in parallel, and Fig. 2 (b) is the series connection of thermoelectric couple inter-stage.
Described coolant channel 4-2, backheat passage 4-3 are circle, rectangle or the curved surface shaped cavity of hollow; Described coolant channel 4-2, backheat passage 4-3 adopt necessary augmentation of heat transfer measure, as increasing fin, adopting plate-fin heat exchanger, micro-channel heat exchanger etc.
The cold energy temperature difference among the present invention sends out that NM other structures no longer describe in detail in the thermoelectric couple group in the refrigerator, all adopts existing ripe thermoelectric generator technology to carry out supporting design.
Described coolant channel 4-2, backheat passage 4-3 adopt plate-fin to change cold element, the cold element of reinforcement biography of cold element or other patterns is changed in the microchannel, the structure of the heat transfer element in its structure and the traditional kind of refrigeration cycle is same or similar, and can use for reference the enhanced heat exchange technology of parallel-flow evaporator in the motorcar air conditioner.
Described cold-producing medium basin 1, cold-producing medium basin 8 adopt necessary cold insulation measure, as adopting the cold insulation materials such as heat-insulation vacuum container, pearlife.
Unaccounted equipment and back-up system thereof, pipeline, instrument, valve, cold insulation among the present invention, have the known mature technologies of employing such as regulatory function bypass facility and carry out supporting.
Be provided with safety, the control facility supporting with cold energy Thermoelectricity refrigerating apparatus of the present invention, make device energy economy, safety, high thermal efficiency operation, reach purpose energy-saving and cost-reducing, environmental protection.
The present invention has following advantage compared to existing technology:
1, for the inefficient characteristic of thermoelectric refrigerator, utilize low-temperature level cooling closed circuit, make up the cold-producing medium Rankine cycle loop under the low-temperature receiver condition, thereby the heat that reclaims the generation of thermoelectric refrigerator process of refrigerastion is used for low-temperature level cooling closed circuit Rankine cycle generating, the comprehensive thermoelectric cooling efficient that improves, refrigerating efficiency can reach more than 50%, realizes simultaneously the step supply of cold, economic, society, environmental benefit are remarkable, are the effective improvement to traditional thermoelectric refrigerator technology.
2, need not to adopt air radiator or recirculated cooling water cooling system in traditional temperature-difference refrigerating device, flow setting is succinct, more meets the energy-conserving and environment-protective principle.
3, the thermoelectric generator that the maintenance load of equipment is more traditional has the reduction of very big degree: owing to adopting clean refrigerant loses heat flow process, can adopt easily to strengthen and pass cold element, need not to worry dust stratification, scale problems, thermoelectric couple group cooling system is optimized, and greatly prolong service life.
4, utilize the cold-storage loop can conveniently realize the cold-storage energy storage, during system cut-off, utilize the cold that holds, contrary running by thermoelectric refrigerator, make original thermoelectric refrigerator form easily the cold energy generation cooling apparatus for cold-storage device, thereby the emergency capability of system, safety operation elasticity are greatly improved.
5, in conjunction with cold energy thermo-electric generation technology, can realize the storage peak regulation function that traditional storage station has, form the combined power and cooling system.