CN104504252B - A kind of Trans-critical cycle CO2The evaluation methodology of the diffusion room efficiency of ejector in kind of refrigeration cycle - Google Patents
A kind of Trans-critical cycle CO2The evaluation methodology of the diffusion room efficiency of ejector in kind of refrigeration cycle Download PDFInfo
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- CN104504252B CN104504252B CN201410755616.XA CN201410755616A CN104504252B CN 104504252 B CN104504252 B CN 104504252B CN 201410755616 A CN201410755616 A CN 201410755616A CN 104504252 B CN104504252 B CN 104504252B
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Abstract
The invention discloses a kind of Trans-critical cycle CO2The diffusion room efficiency of ejector is evaluated in the evaluation methodology of the diffusion room efficiency of ejector in kind of refrigeration cycle, the evaluation methodology using pressure coefficient；Pressure coefficient represented based on diffusion room inlet and outlet pressure, and the expression formula of pressure coefficient is that p is actual cycle process ejector diffusion room outlet pressure in formula, psFor Ideal Cycle process ejector diffusion room outlet pressure, peFor ejector diffusion room inlet pressure.The inventive method evaluates the efficiency of ejector diffusion room using pressure coefficient, and measurement gets up convenient, and the work of evaluation ejector diffusion room is more accurate, more accurately explains the choking phenomenon of injector interior flowing.
Description
Technical field
The present invention relates to a kind of evaluation methodology of the diffusion room work efficiency of ejector, more particularly, to a kind of Trans-critical cycle
CO2The evaluation methodology of the diffusion room efficiency of ejector in kind of refrigeration cycle.
Background technology
As energy shortage and environmental pollution are serious, seek various environmentally friendly, the Sustainable type energy, develop energy-conservation
Technology thing must gone.CO2Paid attention to by many scholars with its unique thermophysical property and environmental friendliness performance.However, by
There was only 31.1 DEG C in its critical temperature, the pressure differential of the high-low pressure both sides of the trans critical cycle system being made up of which is up to
7MPa, and heat loss and restriction loss are crossed all than larger.Wherein, how to reduce system throttles loss becomes raising CO2Refrigeration
One important research content of the coefficient of performance (COP) of system.
Chinese scholars pass through theory analysis and experimental verification, propose the throttling of expansion process is reduced with ejector
Loss, recovery section pressure energy.And ejector has simple structure, low cost, movement-less part, adaptation two phase flow operating mode etc.
Advantage.At present, many scholars are to CO2Steam compressed/jet refrigeration circulation has carried out some theory analysises and has studied, and draws in theory
Coefficient of performance COP improves more than 20% than simple cycle.
When researcher is analyzed mostly, it is assumed that in ejector, Ideal Cycle process is expanded with the ejector of actual cycle process
Pressure chamber outlet pressure is identical；But there is complicated turbulent mixture process, friction loss in injector interior and occur being jammed now
As etc. factor, actual cycle process ejector diffusion room outlet pressure and Ideal Cycle process ejector diffusion room outlet pressure meeting
It is different.Therefore, tradition is based on Ideal Cycle process bar identical with the ejector diffusion room outlet pressure of actual cycle process
The assessment Trans-critical cycle CO made under part2In kind of refrigeration cycle, the diffusion room efficiency evaluation result of ejector is just less reliable.
The content of the invention
The technical problem to be solved is to provide a kind of Trans-critical cycle CO2The diffusion room effect of ejector in kind of refrigeration cycle
The evaluation methodology of rate, evaluates the diffusion room efficiency of ejector by using pressure coefficient, more rationally more accurately can evaluate
The complicated turbulent mixture process of injector interior, determines the impact of friction loss and choking phenomenon to diffusion room work efficiency.
The present invention for the technical scheme that adopts of solution above-mentioned technical problem for：
Trans-critical cycle CO of the present invention2The evaluation methodology of the diffusion room efficiency of ejector, described ejector master in kind of refrigeration cycle
Nozzle to be included, diffusion room and mixing chamber, the evaluation methodology include following operating procedure：
1) first ignore ejector and import and export fluid dynamic energy, ignore pressure drop of the driving fluid in driving nozzle, it is assumed that be mixed
Close indoor for isobaric mixed process；
2) and then using following steps obtain pressure coefficient：
A. temperature T of input nozzle import1, pressure p1, evaporator temperature T2And nozzle efficiency ηp；
B. nozzle inlet enthalpy h is inquired about by the physical property parametric software refprop8.0 that freezes1=h (T1,p1), entropy s1=s
(T1,p1), the ideal escape enthalpy h of nozzle2s=h (T2,s1) and flow type pump with injection import saturated vapor enthalpy h3=h (T2)；
C. the actual outlet enthalpy h of nozzle is calculated successively2=h1-ηp(h1-h2s) and actual exit velocity
D. the initial value of jet coefficient μ is preset, is calculated successively
Diffusion room inlet velocity u5=u2/ (1+ μ), ejector outlet enthalpy h6=(h1+h3* μ)/(1+ μ), the import of diffusion room
Enthalpy h5=h6-(u5)2/2；
Inquiry diffusion room import entropy s5=s (T2,h5), when diffusion room is in perfect condition, h6s=h6, s6s=s5, spray
Emitter exports mass dryness fraction x6s=x (h6s,s6s), pressure p6s=p (h6s,s6s)；
Jet coefficient μ '=1/x is calculated finally6s- 1, judge whether μ=μ ' sets up, if so, Ideal Cycle process is sprayed
Device diffusion room outlet pressure is ps=p6s, otherwise change jet coefficient μ value be iterated calculating until equation set up；
E. define pressure coefficientP in formulaeFor ejector diffusion room inlet pressure, p is actual cycle process
Ejector diffusion room outlet pressure, due to pressure coefficient ηdChanging Pattern can reflect extension pressur efficiency ηkChanging Pattern, so as to
Realize using pressure coefficient evaluating the diffusion room efficiency of ejector.
The step 2) in nozzle efficiency ηpFor constant, value is between 0～1.
Due to actual cycle process ejector diffusion room outlet pressure and Ideal Cycle process ejector diffusion room outlet pressure
Power is different, therefore, by defining pressure coefficient ηdTo describe the work efficiency of ejector diffusion room, description that can be more appropriate is sprayed
The working condition of emitter diffusion room, and it is convenient for measuring determination.
Description of the drawings
Fig. 1 is Trans-critical cycle CO2Steam compressed/injection refrigerating system sketch.
Fig. 2 is the Trans-critical cycle CO using traditional method2Steam compressed/injection refrigerating system p-h figures.
Fig. 3 is the Trans-critical cycle CO using the inventive method2Steam compressed/injection refrigerating system p-h figures.
Fig. 4 is with pressure coefficient η using the inventive method with jet coefficient μ during traditional methoddWith extension pressur efficiency ηkChange
State diagram.
Fig. 5 is with pressure coefficient η using the inventive method with COP during traditional methoddWith extension pressur efficiency ηkChange.
In figure：
1. working fluid import,
2. the virtual condition outlet of nozzle,
The perfect condition outlet of 2s. nozzles,
3. driving fluid import,
4. mixing-chamber inlet,
5. diffusion room import,
6. ejector virtual condition outlet,
6s. ejectors perfect condition is exported,
7. actual gas-liquid separator gaseous phase outlet,
6g. ideal gas-liquid separator gaseous phase outlets
8. real gas cooler inlet,
12. ideal gases cooler inlets
9. actual gas-liquid separator liquid-phase outlet,
6l. ideal gas-liquid separator liquid-phase outlets,
10. import at actual evaporation,
11. ideal evaporator imports.
Specific embodiment
Below in conjunction with the accompanying drawings the inventive method is described further.
As shown in figure 1, Trans-critical cycle CO2The course of work of steam compressed/injection refrigerating system is：
From the gas cooler high pressure CO in thermodynamic state out2Gas enters ejector from working fluid import 1,
By nozzle blood pressure lowering speedup to virtual condition outlet 2 (Ideal Cycle process constant entropy expansion to perfect condition exports 2s), by pressure
When can be converted into kinetic energy, the saturated vapor come by evaporator outlet passes through driving nozzle by injection to suction from driving fluid import 3
The mixing-chamber inlet 4 entered the room, is then mixed into diffusion room import 5 in mixing chamber and working fluid equipressure；Subsequent fluid-mixing
Ejector virtual condition outlet 6 is boosted to by diffusion room, and (Ideal Cycle process isentropic Compression to ejector perfect condition is exported
6s)；Saturated liquid is separated in gas-liquid separator afterwards from actual gas-liquid separator liquid-phase outlet 9 out, saturated gas from
Actual gas-liquid separator gaseous phase outlet 7 out (Ideal Cycle process correspond to respectively preferable gas-liquid separator liquid-phase outlet 6l and
Preferable gas-liquid separator gaseous phase outlet 6g)；Saturated liquid is expanded to 10 (Ideal Cycle mistake of import at actual evaporation by expansion valve
11) journey, subsequently enters evaporator evaporation refrigeration and enters driving fluid import 3 again for ideal evaporator import；Saturated gas is entered
Compressor compresses to High Temperature High Pressure enters back into real gas cooler inlet 8, and (Ideal Cycle process is entered for ideal gases cooler
12) mouth, is then cooled to working fluid import 1 by gas cooler equipressure.
Point out in the present invention that ejector diffusion room outlet pressure is different in the case of two kinds of actual cycle and Ideal Cycle, such as
Shown in Fig. 2 and Fig. 3.
It is that traditional method assumes the inlet and outlet pressure of ejector diffusion room in reality and ideally identical feelings in Fig. 2
Under condition, the extension pressur efficiency η of ejector diffusion room efficiency is evaluatedkIt is that enthalpy is imported and exported based on diffusion room, shape is such as
And the present invention is to quote pressure coefficient ηdTo evaluate the work efficiency of ejector diffusion room, this pressure coefficient ηdIt is base
In the inlet and outlet pressure of ejector diffusion room, it is：
By with MATLAB codings, to CO2Trans-critical cycle jet refrigeration circulation has done numerical simulation calculation, this example
Selected relevant parameter is：Gas cooler exit temperature T1=36 DEG C, evaporating temperature Te=5 DEG C, nozzle efficiency ηp=0.7.
Pressure coefficient ηdConcrete calculation process：
A. temperature T of input nozzle import1, pressure p1, evaporator outlet temperature T2And nozzle efficiency ηp；
B. ejector ideal escape pressure p is calculated according to the inventive method6s；
C. inquiry calculates relevant parameter h1,h2s,h2,h3,u2,s1,s3,p5,p6；
D. preset the initial value of jet coefficient μ；
E. calculate ejector outlet enthalpy h6=(h1+h3* μ)/(1+ μ), inquire about mass dryness fraction x6=x (p6,h6)；
F. calculate jet coefficient μ '=1/x6s- 1, iterative calculation is until μ=μ ' sets up；
G. calculate relevant parameter T6,s6,h7,s7,h8s,h8,T8,h9；
H. unit of account refrigerating capacity q=(h3-h9) * μ/(1+ μ) and compressor unit wasted work w=(h8-h7)/(1+μ)；
I. coefficient of performance COP=q/w is calculated, and is drawn.
Can be with it is clear to see that μ and COP be with pressure coefficient η by Fig. 4 and Fig. 5dChanging Pattern with its with extension pressur efficiency ηk
Changing Pattern it is basically identical, but Fig. 3 definition pressure coefficient ηdIt is the pressure imported and exported based on diffusion room, this can be more proper
When the flowing of explanation injector interior choking phenomenon, and more easily accurately can measure.
Claims (2)
1. a kind of Trans-critical cycle CO2The evaluation methodology of the diffusion room efficiency of ejector in kind of refrigeration cycle, described ejector mainly include
Nozzle, diffusion room and mixing chamber, it is characterised in that the evaluation methodology includes following operating procedure：
1) first ignore ejector and import and export fluid dynamic energy, ignore pressure drop of the driving fluid in driving nozzle, it is assumed that mixing chamber
It is interior for isobaric mixed process；
2) pressure coefficient is obtained using following steps：
A. temperature T of input nozzle import1, pressure p1, evaporator temperature T2And nozzle efficiency ηp；
B. nozzle inlet enthalpy h is inquired about by the physical property parametric software refprop8.0 that freezes1=h (T1,p1), entropy s1=s (T1,
p1), the ideal escape enthalpy h of nozzle2s=h (T2,s1) and flow type pump with injection import saturated vapor enthalpy h3=h (T2)；
C. the actual outlet enthalpy h of nozzle is calculated successively2=h1-ηp(h1-h2s) and actual exit velocity
D. the initial value of jet coefficient μ is preset, is calculated successively
Diffusion room inlet velocity u5=u2/ (1+ μ), ejector outlet enthalpy h6=(h1+h3* μ)/(1+ μ), diffusion room import enthalpy
h5=h6-(u5)2/2；
Inquiry diffusion room import entropy s5=s (T2,h5), when diffusion room is in perfect condition, h6s=h6, s6s=s5, ejector
Outlet mass dryness fraction x6s=x (h6s,s6s), pressure p6s=p (h6s,s6s)；
Jet coefficient μ '=1/x is calculated finally6s- 1, judge whether μ=μ ' sets up, if so, Ideal Cycle process ejector expands
Pressure chamber outlet pressure is ps=p6s, otherwise change jet coefficient μ value be iterated calculating until equation set up；
E. define pressure coefficientP in formulaeFor ejector diffusion room inlet pressure, p is the injection of actual cycle process
Device diffusion room outlet pressure, due to pressure coefficient ηdChanging Pattern can reflect extension pressur efficiency ηkChanging Pattern, so as to realize
The diffusion room efficiency of ejector is evaluated using pressure coefficient.
2. Trans-critical cycle CO according to claim 12The evaluation methodology of the diffusion room efficiency of ejector, its feature in kind of refrigeration cycle
Be, the step 2) in nozzle efficiency ηpFor constant, value is between 0～1.
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| EP1202004A1 (en) * | 2000-10-30 | 2002-05-02 | Calsonic Kansei Corporation | Cooling cycle and control method thereof |
| CN1419089A (en) * | 2002-12-05 | 2003-05-21 | 天津大学 | Carbon dioxide transcrisis refrigeration circulation rotor type expansion energy-saving device |
| CN101160496A (en) * | 2005-04-14 | 2008-04-09 | 开利公司 | Method of determining optimal coefficient of performance in a transcritical vapor compression system |
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| EP1202004A1 (en) * | 2000-10-30 | 2002-05-02 | Calsonic Kansei Corporation | Cooling cycle and control method thereof |
| CN1419089A (en) * | 2002-12-05 | 2003-05-21 | 天津大学 | Carbon dioxide transcrisis refrigeration circulation rotor type expansion energy-saving device |
| CN101160496A (en) * | 2005-04-14 | 2008-04-09 | 开利公司 | Method of determining optimal coefficient of performance in a transcritical vapor compression system |
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