Journal of Energy and Power Engneerng 11 (2017) 655-664 do: 17265/1934-8975/2017.106 D DAVID PUBLISHIN Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson Kazuhro Endoh Research & Development roup, Htach, Ltd., Htachnaka, Ibarak 312-0034, Japan Receved: September 14, 2017 / Accepted: September 25, 2017 / Publshed: October 31, 2017 Abstract: A heat exchanger that arranges flat tubes horzontally has a vertcal header that dstrbutes the refrgerant to each tube. When the heat exchanger works as an evaporator, dfferences n condtons at each branch, such as the rato and dstrbuton of vapor and lqud, due to the dfferences n denstes and momentums of vapor and lqud n the two-phase make equal dstrbuton dffcult. hs paper descrbes the dstrbuton characterstcs of a four-branch header that has a rectangular cross-secton wthout the nternal protruson of flat tubes n the case of the n of the refrgerant R32 from the bottom of the header by usng an equpment that can estmate the dstrbuton rato of the lqud and vapor phase to each branch. hs paper also dscusses the dstrbuton characterstcs on the bass of the vsualzaton n the header. he vsualzaton shows that a lqud level that contans vapor phase exsts n the header and affects the dstrbuton greatly. Key words: Refrgerant dstrbuton, vapor-lqud two-phase, header, flat tube, heat exchanger. 1. Introducton o ncrease energy savng of ar-condtoners, ar-sde pressure loss s beng decreased and heat transfer coeffcent s beng ncreased due to the decrease n the dead-water regon behnd heat transfer tubes of the heat exchanger by reducng dameters of tubes or flattenng them. hs reduces the nner volume of the heat exchanger and results n the decrease n the amount of refrgerant used. On the other hand, the number of passes of the heat exchanger needs to be ncreased to suppress the ncrease n refrgerant-sde pressure loss due to the decrease n the cross-sectonal area of channel. At ths tme, the mportant ssue s to dstrbute the refrgerant to each pass equally. Correspondng author: Kazuhro Endoh, senor researcher, research felds: refrgeraton and ar condtonng. hs paper was presented at 16th Internatonal Refrgeraton and Ar Condtonng Conference at Purdue, July 11-14, 2016, West Lafayette, IN, USA. A multport flat tube has a number of holes whose nner dameter s less than about 1 mm. A heat exchanger that arranges these tubes horzontally has a vertcal header that dstrbutes the refrgerant to each tube. When the heat exchanger works as an evaporator, dfferences n condtons at each branch, such as the rato and dstrbuton of vapor and lqud, due to the dfferences n denstes and momentums of vapor and lqud n the two-phase make equal dstrbuton dffcult. he dstrbuton of two-phase flud n the vertcal header of the flat-tube heat exchanger has been quanttatvely evaluated and vsualzed. Lee [1] studed the dstrbuton characterstcs of the ar-water two-phase flud enterng the bottom of the header. However, snce the physcal propertes of ar-water two-phase flud are very dfferent from those of refrgerants, the fndngs cannot be appled to the header for refrgerants. Byun and Km [2] tested and vsualzed the refrgerant dstrbuton n the vertcal
656 Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson header made for smulatng an actual evaporator. Zou and Hrnjak [3-6] studed the dstrbuton characterstcs of the header wth the nternal protruson of 10 flat tubes, where the refrgerant s from the lower fve flat tubes to the upper fve flat tubes. However, Byun and Km s and Zou and Hrnjak s channel geometres are too complcated for understandng the basc characterstcs of the dstrbuton of a vertcal header. Furthermore, Zou and Hrnjak showed only the lqud phase dstrbuton rato and no vapor phase dstrbuton rato, and ths s nsuffcent to understand detals of dstrbuton characterstcs. o understand the basc characterstcs of the refrgerant dstrbuton of a vertcal header for a flat-tube heat exchanger, ths paper descrbes the dstrbuton characterstcs of a four-branch header that has a rectangular cross-secton wthout the nternal protruson of flat tubes n the case of the n of the refrgerant R32 from the bottom of the header by usng an equpment that can estmate the dstrbuton rato of the lqud and vapor phase to each branch. hs paper also dscusses the dstrbuton characterstcs on the bass of the vsualzaton n the header. 2. Expermental Setup and est Procedure dmensonless hydraulc dameter of 6. Although the header has eght branch holes, four of them are used by appressng a thn plate that opens every other holes or consecutve holes to the sde of the header. he dmensonless branch ptch n the case for every other hole, whch s 2.76, s defned as a standard one and the ptch for consecutve holes as a half one. Fg. 1 Confguraton of header. Branch hole Sght glass Branch hole Channel cross-secton Refrgerant Branch tubes Branch ptch : Standard : Half 2.1 Confguraton of Header Fg. 1 shows the confguraton of a header used for the experment. Fg. 2 shows the confguraton of header channel, and able 1 shows ts specfcatons. Dmensons n able 1 are normalzed wth the hydraulc dameter of the header. he header s made of stanless steel parts and a glass for nsde vsualzaton, whch are bolted for a change of structure. he cross-sectonal shape of the header channel s a rectangle wth an aspect rato of 3. he vapor-lqud two-phase refrgerant s from the bottom of the header to branch holes on the sde of the header, whch mmc a multport of a flat tube and have a flat cross-sectonal shape wth an aspect of 1 wth a (a) (b) Fg. 2 Confguraton of header channels: (a) standard branch ptch and (b) half branch ptch. able 1 Specfcatons of header. Header channel Branch hole Cross-sectonal shape Rectangle Aspect rato 3 Dmensonless hydraulc dameter 1 Number of branch 4 Dmensonless branch ptch 1.38, 2.76 Cross-sectonal shape Flat Aspect rato 1 Dmensonless hydraulc dameter 6
Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson 657 2.2 Expermental Setup and est Procedure Fg. 3 shows the system dagram of the expermental setup for evaluatng the refrgerant dstrbuton of a four-branch header. he expermental setup conssts of a compressor (1), an ol separator (3), a water-cooled condenser (4), a preheater (6), an expanson vale (7), a test header (8), and an evaporator (9) that has four passes of heater-heated tubes and four straght tubes (11) for measurng dfferental pressures. he powers of heaters for each pass of the evaporator are controlled n such a way that the temperatures of superheated vapor at the outlet of each pass are set at a predetermned value. Dfferental pressures of superheated vapors n straght tubes at the outlet of each pass are measured for estmatng refrgerant rates. A header nlet enthalpy h needed for obtanng a header nlet qualty s calculated as follows, usng P W (8) (6) (7) N Pass No. 1 Pass No. 2 Pass No. 3 Pass No. 4 (1) Compressor (2) Bypass valve (3) Ol separator (4) Condenser (water-cooled) (5) Constant temperature water bath (6) Preheater (electrc heater heated) (7) Expanson valve (8) est header (9) Evaporator (elctrc heater heated) (10) Sght glass (11) Straght tube P Fg. 3 System dagram of expermental setup. (5) (10) (11) (4) dp dp dp dp (9) P W W W W M: Corols mass meter N: urbne meter W: Electrc power meter P: Pressure tranceducer dp: Dfferental pressure transducer : Sheath type thermocouple M P (2) (3) (1) the condenser nlet enthalpy c as a standard and representng the water heat exchange amount of the condenser as Q w, the electrc power of the preheater as W ph, and the refrgerant rate as r. ( Q W )/ (1) h c he water-sde heat exchange amount of the condenser Q w s calculated as follows, usng the heat capacty C pw, the densty ρ w, the volume rate L w, the outlet temperature wo, and the nlet temperature w for water. Q w w ph C L ) (2) pw w r w( wo w he refrgerant rate n the No. pass (branch) r, s estmated from a Blasus equaton for frcton factor as follows, usng the dfferental pressure n a straght tube P, the densty ρ, and the vscosty μ. r, 4 j 1 k ( P j k ( P j 5 1/1.75 ) j 5 1/1.75 j ) r (3) he correcton factor k s for compensatng for producton varaton of straght tubes. Snce a total of refrgerant rates estmated from the dfferental pressures n the straght tubes of each pass are dfferent from the refrgerant rate wth the mass meter r, the refrgerant rate n the No. pass r, s corrected by multplyng the rato. An enthalpy of No. branch of the header outlet (branch nlet) ho, needed for obtanng a qualty of No. branch nlet x ho, s calculated as follows, usng the outlet enthalpy of pass No. evaporator (heater-heated tube) eo, and the electrc power of No. pass heater W e,. We, Qe ho, eo, (4) W Snce the electrc power of heater dffers from the refrgerant-sde heat exchange amount due to the effect of heat exchange wth the surroundngs, the electrc power of No. pass heater W e, s corrected by the rato of the refrgerant-sde heat exchange amount Q e to the r, e
658 Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson total electrc power of heaters W e. Q e and W e are represented as follows. Q ) (5) e r ( eo h 4 W (6) e W e, 1 he lqud phase rate of No. branch of the header outlet r_l, and the vapor phase rate of that r_v, are represented as follows, usng a qualty x ho, and refrgerant rate r,. r _ l, ( 1 xho, ) r, (7) r v, xho, r, _ (8) Snce the lqud phase refrgerant that has evaporatve latent heat contrbutes to the coolng at the evaporator, the dstrbuton rato of lqud phase s mportant. he dmensonless standard devaton related to lqud phase rate σ s used as an ndex for the dstrbuton performance as follows, lettng r _ l rate. be the arthmetc mean value of lqud phase 4 1 1 2 ( r _ l, r _ l ) (9) 4 r _ l 1 4 1 r _ l r _ l, (10) 4 1 able 2 shows test condtons at the header nlet. he refrgerant R32 was used and the settng pressure was 1.28 MPa, whose saturated temperature s 15 C. he mass fluxes were set to 25, 50, and 75 kg/(m 2 s) for evaluatng the effect of mass flux. he qualtes were also set to,, and for evaluatng the effect of qualty. o reduce the dfference between the electrc power of the heater and the refrgerant-sde heat exchange amount at the evaporator, the expermental setup was nstalled n the temperature-controlled room at about 15 C, whch s close to the refrgerant temperature at the header nlet. he dfference between the total electrc power of heaters W e and the refrgerant-sde heat exchange amount Q e was wthn 3% at the mass flux of 50 kg/(m 2 s). he test condtons were set by adjustng the compressor speed, the water rate at the condenser, the openng of the expanson valve, and the amount of the refrgerant charged. he electrc powers of the heaters were controlled n such a way that the refrgerants at the outlet of each pass of the evaporator were superheated at the temperature of 25 C. REFPROP [7] was used for the thermodynamc propertes of R32. Flud n the header was observed by takng pctures at the recorded rate of 2,000 fps wth a hgh-speed camera through the sght glass. 3. Expermental Results and Dscusson 3.1 Effect of Inlet Qualty and Mass Flux on Dstrbuton Fg. 4 shows the measured refrgerant dstrbuton of the header at the mass flux of 50 kg/(m 2 s) for the standard branch ptch. he branches are numbered 1-4 from top to bottom. he lqud phase rato for each branch s the rato of ts lqud phase rate to the total lqud phase rate. he same goes for the vapor phase rato and the vapor-lqud two-phase rato. herefore, the phase rato for the equal dstrbuton s 25%. For the header nlet qualty = 1, the lqud phase ratos are about 30% each for the lower three branches (No. 2-4) and only 6% for the top branch (No. 1). he lqud phase ratos for = 7 are about 40% each for the lower two branches (No. 3, 4), about 20% for No. 2 branch, and 2%, whch s very lttle, for No. 1 branch. he lqud phase ratos for = 3 are about 60, 30, 10, and 2% for No. 4, 3, 2, and 1 branches. he lqud phase rato of the bottom branch (No. 4) thus ncreases as qualty ncreases. he lqud able 2 est condtons at header nlet. Refrgerant R32 Pressure 1.28 MPa Saturated temperature 15 C Mass flux 25, 50, 75 kg/(m 2 s) Qualty,,
Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson 659 0.7 1.0 Lqud phase rato xh=1 x xh=7 x xh=3 x Vapor phase rato 0.8 xh=1 x xh=7x xh=3x 1.0 Branch nlet qualty 0.8 xh=1 x xh=7 x xh=3 x Vapor-lqud two-phase rato xh=1 xh=7 xh=3 Fg. 4 Measured refrgerant dstrbutons of header wth standard branch ptch (50 kg/(m 2 s)). phase rato of the second branch from the bottom (No. 3) once ncreases and then decreases and those of the top two branches (No. 1, 2) decrease monotoncally as qualty ncreases. he branch nlet qualtes for the header nlet qualty = 1, where the lqud phase refrgerant s dstrbuted to the lower three branches by about 30% each, are nearly zero for the lower three branches. hs shows that very lttle vapor phase refrgerant s nto these branches. hs can be found n the graph of the vapor phase rato of branches. he branch nlet qualtes for = 7, where the lqud phase refrgerant s dstrbuted to the lower two branches by about 40% each, are 6 for the lower two branches, whch s obvously very lttle, and ths shows that lqud-rch refrgerant s nto these branches. he vapor-lqud two-phase ratos, or the refrgerant rate ratos, for all qualtes are close to 25%, whch represents equal dstrbuton. hs s because the magntude relatonshps of lqud phase rato and vapor phase rato are opposte, and as a result, the sums of lqud phase and vapor phase for each branch become nearly equal. Fg. 5 shows the lqud phase ratos for the mass flux of 25, 50, and 75 kg/(m 2 s). In the range of these mass fluxes, there s no bg dfference n the dstrbuton. However, closer examnaton shows that as the mass flux ncreases, the lqud phase rato of No. 1 branch for ncreases slghtly and that of No. 4 branch for decreases. hese show that ncrease n the mass flux leads n the drecton of equal dstrbuton. Fg. 6 shows the dmensonal standard devatons for lqud phase dstrbuton. For the mass flux of 50 kg/(m 2 s), the dmensonless standard devaton σ at = s 45% and σ at = s 89%, whch s about twce as large as that at =. σ for the mass flux of 75 kg/(m 2 s) s about 10% to 20% lower than that for 50 kg/(m 2 s). Fg. 7 shows typcal photographs of flud n the header shot wth the hgh-speed camera. he regme for the mass flux of 25 kg/(m 2 s) and the qualty = 2 s slug, where lqud, whch ncludes small bubbles, and large bubbles alternately. Observaton on successve photographs for one second depcted n Fg. 8 shows that the lqud level fluctuates and rses especally largely as the especally large bubble rses. At ths tme, the lqud
660 Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson 0.7 was done through the one-sded glass, t s hard to determne the regme for = 3, where vapor Lqud phase rato xh=2 xh=2 xh=3 phase rate s large. Under these condtons, the regme seems to be annular. At ths tme, the lqud level exsts between the postons slghtly above the second branch from the bottom and slghtly above the bottom branch. Examnaton of the relatonshp between the lqud Lqud phase rato 0.7 (a) 25 kg/(m 2 s) xh=1 xh=7 xh=3 level for the mass flux of 25 kg/(m 2 s) n Fg. 7 and the lqud phase dstrbuton rato n Fg. 5a shows that the lqud phase refrgerant s dstrbuted subequally to the branch almost under the lqud level. hs means that for = 2, the lqud level s almost above the lower three branches (No. 2-4), to whch the lqud phase s dstrbuted by about 30% each, and for = 2, the lqud level s above the lower two branches (No. 3, 4), to whch the lqud phase s dstrbuted by about 40% each. In Fg. 7, under the condtons of the mass flux larger than 50 kg/(m 2 s) and the qualty larger than 0.7 (b) 50 kg/(m 2 s) 7, where the vapor phase speed s hgh, the lqud level was not able to be dstngushed from the wavy lqud flms formed on the glass, whch had sharp Lqud phase rato xh=9 xh=9 xh=9 fluctuaton, and the heght of the lqud level was not able to be determned. However, snce the dstrbutons of lqud phase ratos for the mass flux of 50 and 75 kg/(m 2 s) are smlar to those for 25 kg/(m 2 s) n Fg. 5, the lqud levels for 50 and 75 kg/(m 2 s) seem to be the same heght as that for 25 kg/(m 2 s). 1.2 Fg. 5 (c) 75 kg/(m 2 s) Effect of mass flux on lqud phase dstrbuton. 1.0 0.8 level exsts between the top branch and the second branch from the top. he regme for = 2 s churn, where vapor phase rate ncreases and lqud bodes reman n places. At ths tme, the lqud level also fluctuates and exsts between the second and thrd branches from the top. Snce the cross-sectonal shape nsde the header was a rectangle and the observaton σ 0.8 Qualty 25kg/m2s kg/(m 2 s) 50kg/m2s kg/(m 2 s) 75kg/m2s kg/(m 2 s) Fg. 6 Relatonshps of nlet qualty, mass flux, and dmensonless standard devaton.
Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson Mass flux (kg/(m2 s)) 25 Qualty xh 50 661 75 2 2 3 1 7 3 9 9 9 Slug Churn Churn Churn ~ Churn ~ Fluctuatng range of lqud level Photograph Flow regme Fg. 7 0s Fg. 8 Photographs of nsde header. 5s s 5s s 5s s 5s s 5s s 5s s 5s 0.7s 0.75s 0.8s 0.85s 0.9s 0.95s 1.0s Successve photographs of nsde header for mass flux of 25 kg/(m2 s) and xh = 2. In Fg. 4, as descrbed above, very lttle vapor phase refrgerant s nto the lower three branches for the qualty xh = 1 and the lower two branches for xh = 7. hs s because rsng vapor phase does not change the drecton, barely ng nto branch holes on the sde, and goes straght upward. hs s probably affected by buoyancy. Although the regmes depend on the mass flux and qualty, lttle vapor phase refrgerant s nto the branch holes under the lqud level n any regme.
662 Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson 3.2 Effect of Branch Ptch on Dstrbuton Fg. 9 shows the lqud phase ratos of the header wth the half branch ptch for the mass flux of 25 kg/(m 2 s), compared wth those wth the standard ptch. For the nlet qualty, although the lqud phase ratos are about 30% each for the lower three branches (No. 2-4) for the standard ptch, the rato of No. 2 branch, whch s the top of these three branches, decreases slghtly and the rato of No. 1 branch ncreases slghtly for the half ptch. For, although the lqud phase ratos are about 40% each for the lower two branches (No. 3, 4) for the standard ptch, the rato of No. 3 branch, whch s hgher, decreases slghtly and the rato of No. 2 branch ncreases slghtly for the half ptch. Furthermore, for, the rato of No. 4 branch, whch s the bottom, decreases and the rato of No. 2 ncreases. herefore, the decrease n branch ptch mproves the dstrbuton. Fg. 10 shows the photographs of nsde the header wth the half branch ptch and Fg. 11 shows the successve photographs for = 1. Observaton on successve photographs for one second shows that the fluctuatng range of lqud level of the header wth the half branch ptch for each qualty s almost the same or slghtly larger than that wth the standard branch ptch. For, although the lowest lqud level s close to the second branch from the top (No. 2) for the header wth the standard branch ptch, the lowest lqud level s close to the thrd branch from the top (No. 3) for the header wth the half branch ptch. hs leads to the ncrease n the rato of the tme when the lqud level s under No. 2 branch, resultng n a decrease n the lqud phase rato of No. 2 branch. he reason for the ncrease n the lqud phase rato of No. 1 branch s that the decrease n the branch ptch makes the entraned droplets reach the branch more easly. Smlarly, for, although the lowest lqud level s close to the thrd branch from the top (No. 3) for the header wth the standard branch ptch, the lowest lqud level reaches the bottom branch (No. 4) for the header wth the half branch ptch. hs leads to the ncrease n the rato of the tme when the lqud level s under No. 3 branch, and as a result, the lqud phase rato of No. 3 branch decreases. For, the decrease n the branch ptch makes the entraned droplets reach No. 2 branch more easly, resultng n the ncrease n the lqud phase rato of No. 2 branch. Lqud phase rato 0.7 xh=2 xh=2 xh=3 xh=1 xh=1 xh=9 Branch Ptch Standard Fg. 9 Effect of branch ptch on lqud phase dstrbuton (25 kg/(m 2 s)). Mass flux (kg/(m 2 s)) 25 Qualty 1 1 9 Photograph Flow regme Fluctuatng range of lqud level Slug Fg. 10 Photographs of nsde header wth half branch ptch. Churn Half
Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson 663 0s 5s s 5s s 5s s 5s s 5s s 5s s 5s 0.7s 0.75s 0.8s 0.85s 0.9s 0.95s 1.0s Fg. 11 Successve photographs of nsde header wth half branch ptch for mass flux of 25 kg/(m2 s) and xh = 1. 4. Conclusons Rato of σ for half ptch to σ for standard ptch 1.2 1.0 he conclusons drawn from the dscusson on the dstrbuton characterstcs of the vertcal header 0.8 25kg/m2s kg/(m2 s) kg/(m2 s) 50kg/m2s kg/(m2 s) 75kg/m2s Qualty 0.8 Fg. 12 Effect of branch ptch on dmensonless standard devaton. Fg. 12 shows the rato of the dmensonal standard devatons for lqud phase dstrbuton of the header wth the half branch ptch to those wth the standard branch ptch. For the mass rate of 50 kg/(m2 s), the dmensonless standard devatons for the half branch ptch are about 20% lower n the qualty range of - than those for the standard branch ptch. he effect of branch ptch on dstrbuton s summarzed below. he fluctuatng ranges of lqud level n the header are almost the same regardless of the branch ptch. As a result, the relatve fluctuatng range of lqud level to the branch ptch ncreases as the branch ptch decreases. hs leads to the decrease n the lqud phase refrgerant that s nto the branch near the lqud level, and the entraned droplets reach the upper branch more easly as branch ptch decreases, resultng n mproved dstrbuton. wthout nternal protruson on the bass of the vsualzaton n the header are as follows. A lqud level that contans vapor phase exsts n the header, and the heght of the level decreases as the qualty of the refrgerant ncreases. he amount of refrgerant that has lttle vapor s dstrbuted subequally to branch holes under the level. he fluctuatng ranges of lqud level n the header are almost the same regardless of the branch ptch. As a result, the relatve fluctuatng range of lqud level to the branch ptch ncreases as the branch ptch decreases. hs leads to the decrease n the lqud phase refrgerant that s nto the branch near the lqud level, and the entraned droplets reach the upper branch more easly as branch ptch decreases, resultng n mproved dstrbuton. References [1] [2] [3] Lee, J. K. 2009. wo-phase Flow Behavor nsde a Header Connected to Multple Parallel Channels. Expermental hermal and Flud Scence 33 (2): 195-202. Byun, H. W., and Km, N. H. 2011. Refrgerant Dstrbuton n a Parallel Flow Heat Exchanger Havng Vertcal Headers and Heated Horzontal ubes. Expermental hermal and Flud Scence 35 (6): 920-32. Zou, Y., and Hrnjak, P. S. 2013. Experment and Vsualzaton on R134a upward Flow n the Vertcal
664 Refrgerant Dstrbuton Characterstcs n Vertcal Header of Flat-ube Heat Exchanger wthout Internal Protruson Header of Mcrochannel Heat Exchanger and Its Effect on Dstrbuton. Internatonal Journal of Heat and Mass ransfer 62 (July): 124-34. [4] Zou, Y., and Hrnjak, P. S. 2013. Refrgeraton Dstrbuton n the Vertcal Header of the Mcrochannel Heat Exchanger Measurement and Vsualzaton of R410A Flow. Internatonal Journal of Refrgeraton 36 (8): 2196-208. [5] Zou, Y., and Hrnjak, P. S. 2015. Comparson and eneralzaton of R410A and R134a Dstrbuton n the Mcrochannel Heat Exchanger wth the Vertcal Header. Scence and echnology for the Bult Envronment 21 (5): 555-63. [6] Zou, Y., and Hrnjak, P. S. 2015. Dstrbuton Functon for Reversble Mcrochannel Heat Exchanger wth Vertcal Headers Consderng the Effects of Inlet Condtons, eometres and Flud Propertes. Present at 24th Internatonal Congress of Refrgeraton, Yokohama, Japan (ID: 6). Pars, France: IIR. [7] Lemmon, E. W., Huber, M. L., and McLnden, M. O. 2013. NIS Standard Reference Database 23: Reference Flud hermodynamc and ransport Propertes-REFPROP, Verson 9.1. athersburg: Natonal Insttute of Standards and echnology.