The procedures developed of automatic cascade non-azeotropic. refrigerant selection and matching

Transcription

1 5th Internatonal onference on Avance Desgn an Manufacturng Engneerng (IADME 15) The proceures evelope of automatc cascae non-azeotropc refrgerant selecton an matchng Zheng Da-yu (a), B. hen u-yan (b), B. Gao L-png (b),.lu-le (c). hen-shuo (c), D. L Xang (), D. Yu Ha-feng (), D. L Je () (a) School of Energy an vl Engneerng of Harbn ommercal Unversty Harbn, 158, hna Fax , zhengayu@16.com (b)(c)() School of Energy an vl Engneerng of Harbn ommercal Unversty Harbn, 158, hna Fax , superteacher73@16.com KEYWORDS: automatc cascae, non-azeotropc refrgerant selecton, matchng ABSTRAT: Draw the commonly refrgerants table for wrtng n the program selector workng par n tune content. Selecton accorng to the evaporaton temperature of low temperature refrgerant, base on tratonal non-azeotropc refrgerant select automatc cascae prncple, the preparaton metho of choce of refrgerant an wrtten proceures, the use of the program to select the approprate refrgerant refrgerant par. Meanwhle calculate by the heat balance prncple to raw a flow chart an wrte a program to calculate, usng the program raw on the rato of the refrgerants. VLE calculate usng the number of moles of the components, the use of the program to optmze the rato of the refrgerant. Makng savng automatc cascae refrgerant selecte tme, choose refrgeraton system s more effcent an more economc an envronmental protecton.fnally ths paper analyzes the reason of the automatc cascae OP value s low, to mprove after automatc cascae system scheme s put forwar. INTRODUTION Wth the avancement of technology, the ncreasng growth of the peoples lvng stanars. Whether n the bomecal communty, or n the tratonal manufacturng nustry, more an more eman for low temperature, whch s ncreasng the eman for equpment. Wth coolng temperatures requre lower temperatures, the effcency of the tratonal way of usng a sngle throttle refrgeraton refrgerant s reuce, can not acheve the requrements of energy conservaton, but also can not reach the esre low temperature [1]. n-azeotropc refrgerant for refrgeraton sector proves a new lower coolng worl, whle sngle machne mult-level automatc cascae makes movng parts whle reucng the esre temperature s reache, an get smple safe operaton of the refrgeraton system. n azeotropc ue to the fferent bolng pont n the process of heat transfer component changes, the proporton of non azeotropc evaporaton temperature of the workng meum s lower than any other sngle workng meum evaporaton temperature, then can get cryogenc refrgeraton temperature. In orer to acheve ts best OP, automatc cascae refrgeraton system refrgerant rato s the prmary problem, base on prevous experments show that the best rato can mprove the OP of the system []. 15. The authors - Publshe by Atlants Press 648

2 Rato of the refrgerant Select the correct non-azeotropc refrgerant par, an calculate ther rato. Reasonable rato can reuce the equpment operaton s amage, longer equpment lfe an safer. omparson of the rato of the conventonal metho of theoretcal an expermental results, only the combnaton of the fne-tune the rato of the refrgerant to get the best rato. onsere stable operaton of the automatc cascae refrgeraton system of nternal refrgerant n vapor-lqu equlbrum. Each of the refrgeraton cycle s assume that no pressure loss n the ppelne, wthout heat exchange, the compresson process s aabatc sentropc compresson, the gas-lqu separator lqu s pure lqu, an a unform temperature over the gas-lqu state uner a smplfe refrgeraton cycle. Draw ts varous contons of low temperature coolng effect parameters accorng want to acheve. Auto cascae refrgeraton are one by a compressor cycle, wth the classc cascae refrgeraton cycle thermoynamc calculaton as [4] : G = (1) q Equaton: G - cryogenc refrgerant mass flow rate (kg/s); - the requre coolng capacty (kw); q - ryogenc coolng capacty per unt mass (kj /kg). After the low-temperature refrgerant mass flow rate calculate by the estmaton of the amount of heat exchange evaporator conensate to etermne the low-temperature refrgerant conense refrgerant mass flow rate. = G ( q ) () k, + w Equaton: k, - cryogenc refrgerant conensng loa (kw); G - Low-temperature refrgerant mass flow rate (kg / s); w - Theory cryogenc unt power n low temperature (kj / kg). o, x 1. k, = (3) Equaton: o, x - cryogenc refrgerant conensng refrgerant evaporator loa (kw); Above, n the calculaton of the mass flow rate of refrgerant conensng low temperature refrgerant, by the estmaton of conensate evaporator heat transfer, an to etermne the next refrgerant flow of refrgeraton, the mole fracton of each component for VLE theoretcal calculaton of the nee theory ata. n-azeotropc mxe refrgerant bolng pont no common element n each group. Evaporaton or conensaton n certan contons, the vapor an lqu phases of fferent composton an temperature are constantly changng. 649

3 Vapor Dew pont curve Bubble pont curve Bq Temperature T Bl B Two-phase regon A Lqu Mole fracton Fgure1 n-azeotropc refrgerant(t-ε) fgure n-azeotropc mxe refrgerant occurs n the temperature change when the change n the phase constant pressure, the conensaton temperature ncreases at constant pressure to the bubble pont temperature of the ew pont temperature, the evaporaton pressure s fxe to the ew pont temperature becomes from the bubble pont temperature. Accorng to the characterstcs of the mxe refrgerant s wely use n the temperature fference between heat source to match the occason, n orer to acheve approxmate Lorentz cycle n orer to acheve the energy savng effect. The nature of the mxe refrgerant approxmates the average propertes of each component [4]. Vapor-lqu equlbrum s an nterrelate an mutually nepenent co-ecology. For the mult-component system, heat balance refers to the equlbrum force balance an equlbrum contons are satsfe, that s, each phase of the temperature, pressure an chemcal potental of the components n the respectve phases are equal. Metho for calculatng vapor-lqu equlbrum stll scusse, but t s stll the most commonly use metho s stll more precse use of the equaton of state of pure refrgerant to be ntrouce nto a sutable mxng ngreents varable to stuy the rules of the VLE features. Select fugacty coeffcents calculate PR equaton of state, that s, from the P-V-T relatonshp or measure ata of the substance calculate wth hgh accuracy [5]. PR equaton of state s: RT a( T ) P = (4) V b v( v + b) + b( V b) Where a( T) = aa( T), a c c R T RT =.4574, b =. 778 P P 1 + ( ω.699ω ) a( T) = T.5 1 ( ) T Equaton R s the unversal gas constant, T s the temperature, V s the molar volume, a functon of the temperature, b s a functon of the volume. Mxng rule to select fferent computng has a great mpact on the fugacty coeffcent of component. Frst select a classc mx of sngle-class rule Vaner Waals mxng rule [6] : a X = X a (5) b X = X b (6) 65

4 a 1 = 1 K )( a a ) (7) ( The (3-5) nto (3-) have: b = b + b )/ (8) m ( n b = x b = 1 Accorng to the unque nature of mxe refrgerants, vapor-lqu equlbrum theory can be use to calculate the bubble pont, seekng vapor phase components; ew pont calculaton, seekng lqu components; calculaton of two-phase regon, seekng equlbrum vapor an lqu phases group ryness, equlbrum constants, quanttatve stanars for each component of volatlty. Table 1 The metho to calculate VLE by equaton of state Known varables The unknown varables ueston classfcaton P, X T, y Bubble pont temperature P, y T, X Dew pont temperature T, X P, X Bubble pont pressure T, y P, X Dew pont pressure (9) The specfc calculaton shoul have a small amount of expermental ata, frst usng the theory of tratonal matchng of components nstea of ata generaton nto the process. Accorng to the above formula for calculaton program block agram [7] : 1 - Gven P an x values, entfe calculate the requre physcal constants. Temperature an phase composton of the unknown. - Selecte equaton of state to erve fugacty coeffcent equatons, an calculate vapor-lqu equlbrum rato; 3 - From the new calculate value obtane, the values are normalze wth the prevous teraton untl the fference s less than a preetermne allowable value (.1); 4 - Jugment the fference s less than a preetermne value, f less than the en of the calculaton process, output, f more than, nee to contnue to aust the temperature, untl meets the requrement. Prnt X, Y, T Gven P an X Estmate T an y uery physcal constants Austment T alculaton KX Gross whether??? = 1 alculate Y oeffcent alculatey Whether calculate KX gross change Interacton coeffcent s calculate alculatng new lqu components Whether teraton Fgure VLE calculaton flowchart 651

5 ONLUSIONS Automatc cascae refrgeraton energy effcency rato of the sze of the refrgerant has a great mpact on energy conservaton to reuce the amount of refrgerant charge whle not reucng the coolng capacty s the most mportant current research. The fllng shoul have the flexblty to master refrgerant refrgeraton equpment use fferent rules n certan proceures to quckly select a refrgerant par an proporton, save tme an be more accurate. That s accorng to the requre refrgeraton temperature, the refrgeraton capacty can rectly select the qualty an levels of non-azeotropc rato. An can be base on obectve factors gven n a varety of refrgerants par targete selecton, not only to meet the eman for coolng, but may well reuce the use of refrgerants, mprove ts effcency, economy an reuce the nfluence of refrgerants on the envronment. Effect of non-azeotropc refrgerant automatc cascae OP of the refrgeraton cycle as well as an mportant reason for the refrgerant heat exchanger separaton factor. Wth ecreasng evaporaton temperature, but the temperature of the evaporator to reuce the slp, whch shows the value of the refrgerant n the ryness of the throttle s large, a serous loss of latent heat of vaporzaton, n orer to avo ths stuaton, shoul ncrease the egree of subcoolng. Acknowlegements Helongang Provnce Natural Scence Fun Proect: NumberE131 Helongang Provnce Grauate Innovaton Fun Proect: NumberYJSX13-4HSD REFERENES [1] Weang Lu. Ternary non-azeotropc automatc cascae cryogenc equpment research [D]. Harbn Unversty of ommerce, 1. [] Bngfeng Yu. Refrgeraton an ar contonng applcaton of new technology [M]. hemcal Inustry Press,. [3] Yta Ma, Zhmng Gao, Dong hen. Multvarate mxe refrgerants screenng an matchng prncple [J] Engneerng Thermophyscs, 1997, 18 (1): 17-. [4] Yezheng Wu. Refrgeraton prncples an equpment [M]. Xan Jaotong Unversty Press, [5] Junsheng Wu. hemcal Separaton Engneerng [M]. Scence Press,. [6] Zqang Zhu, Youtng Wu. hemcal Thermoynamcs [M]. hemcal Inustry Press, 1. [7] Jun Wang, Mn L, Erx heng. Mxe refrgerant chller esgn prncple an calculaton [J] Journal of Beng Unversty of Aeronautcs an Astronautcs, 198, 4: 5. 65