A STUDY ON THE IMPROVEMENT OF EXHAUST RANGE HOOD AND FAN-ASSISTED VENTILATlON SYSTEMS FOR COOKING A. Kegasa Osaka Gas Co., Ld. Nishi-ku, Osaka 550, Japan K. Yagoh \ Osaka Gas Co., Ld. Nishi-ku, Osaka 550, Japan T. Yamanaka Osaka Universiy Suia, Osaka 565, Japan Venilaion rae is regulaed by a building ode so ha indoor air may no be pollued by ombusion produs from ooking applianes in Japan, whih aused unexpeed problems. suh as large noise, roubles brough abou by redued indoor air pressure, and higher hea load of air-ondiioning* In order o solve hese problems, we have developped a effiien exaus range hood whih an redue 2/5 of usual flow rae wihou any size-up. We ompared i wih onvenional range hoods and esed i using. various ooking applianes. And we also ondued somewha dynami experimens suh as when really ooked and when fresh air was direly supplied hrough a du. Finally, we ompared he effiieny when ooked by gas applianes wih when by elri ones. From hese experimens, we found ha he performane of he hood and haraerisis inheried by he ooking energy were made lear. INTRODUCTION ~,., I )._...,,,., Wih reen inrease in airighness of residenes, kihen venilaion problems have been araing people's aenion. Japanese building ode requires fan assised venilaion so as o keep o. onenraion down o 21.5%, whih requires higher flow rae of abou o.i4rrl'/s(500rrl'/h). Bu unexpeed problems have oured by pleniful venilaion. For expample, large noise is generaed, doors and windows are hard o open by redued indoor air pressure, hea load of airondi ioning is inreased and so on. In order o solve hese problems, we have developed a effiien exhaus range food and we ompared i wih onvenional range food using various ooking applianes. And we also made somewha dynami experimens suh as when really ooked and when oudoor air was supplied direly hrough a du in a air igh model kihen, he resuls ware exellen and ineresing as follows. 401
TESTING METHOD The exhaus apure effiieny of a range exaus hood was measured in onformiy o he BL esing mehod (Fig.1). In he ase of using eleri ho plaes, he apure effiieny was measured by spouing ou C02 as raer gas hrough holes on a ring shape ube surroundig ouer surfae of a pan boom in omformiy o he BL mehod. The COa onenraion was measured by an infrared sperophoomeer (Honeywell KNG 14) and he air flow rae by an ulrasoni flow meer (Kaijo Denki GF-150). m!~:.v~~~ x M i la in ra x 100 00 Fl g. l Bl Tulng l'ahod ( DEVELOPMENT OF RANGE EXAUST HOOD When flow lines around a onvenional hood of ypial onsruion are invesigaed visually, he overflows as shown in Fig.2 an be observed. The onveninal. hood has defes of having inerfering omponens suh as he fan boom over and he lighing over and leing exaus air pass hrough he op inle hole a low venilaion rae. Afer some preliminary experimens and repeaed rials and errors, a range exaus hood of onsruion shown in Fig.3 has been developed. Even hough he hood has usual size(600mm!ix 600mmDX 400mmll),100% apure effiieny has been ahieved a he venilaion rae of 300m"/h whih are abou 60% of usual hoods. The onsraive feaures are enumeraed as follows: Arranging he fan and he lighing over no o preven suion. Providing greaer dishae beween he end of hood boom and he fan inle por. Inreasing suion speed around he ~ hood-end using double hood onsraion. Ela. 2 Overflow fr.,. Elhaus!!!!!9! Hool l E [ 0 :; : j/ :-' 402
RESULTS AND FINDINGS --! 1(sai Resuls The exhaus apure effiieny of he developed range hood using various gas.. ho' plaes is shown in FigA. Though he effiieny is 100% in he ase of he BL mehod(3.5kw burner), shifing he burner ener forward or inreasing of he.ombusion rae lowers he effideny. Howeve), when muliple burners are fired, buoyan plume inerferes wih one anoher and ends o olle a he ener, and he apaiy does no lower as muh ~j as he.inrease of ombusion rae. '. Even when 4 burners are fired, he : developed range hood sill holds 90% effiieny a 300ri/h. Fig.5 ompares apure apaiy of various A range hoods generally used. Fig.6 shows I 00 200 JOO <OO 500 Yenl lai~ Rie (n1/hr) flg.c Poro,..,,.., a'i Various Ho plau 100!00 <00 Yenl l1lnv Rie (ni/hr) Fl1.5 Porfornnai of Yorio.is Hoods oulines of he hoods used in he om par is on. The apaiy of he developed hood and he ypial one is on rased in Fig.7, when gas or eleri ho plaes are used. The reason why.he differene in effiieny appears beween eleri and gas ho plaes in he ase of a ypial hood may be explained by he differene of buoyan plume speed. As shown in Fig 8, a gas burner generaes higher exhaus gas speed, and herefore plume ends o be saered a he fan and lighing over. The performane when insallaion posiion was lowered is shown in Fig 9, 100 200 loo 400 SCIO Ven 1 lalng Ra (m/hr)!l1~rfo1'1111(!!'.'1.!112_~_!!!'! Elo~ Plelos 403
oioli:,. alan) p,...in.-;il lfji hi. 11 h, flllil'" ~~~~~:ilpldui i.e "' ~. I :. frying..,..,.1. (oooll.in aaion) pje-.e\ in pulin in oil puing in " 'k pu\lng in -llli<i - PUU in in PUl in in ooodln 11faad~r -. ~ I (;.... u~, Cl 10 Ill) o ~.. Capure EffllSIC)' (l) Capure EffllSICI' 00 fjg. l? ~!l!r Eff!!!!9..!.l!L~J!'!9 (eleer) ho pl l fried rie) f!j..1!. el'.!.~r!..illill '!"!SL!l!!!. ~l~ (eleri ho plae a- a!en) aording o dishes and hea soures ogeher wih ooking moions; Figures indiae ha moions o move a frying pan and o mix ingrediens ause buoyan plume o overflow, hus lowering he effiieny. From he view poin of differene in menus, how mien whih requires bigger moion loses greaer effiieny. The eleri applianes lower he effiieny more grealy when hands are moved han he gas ones, resuling poorer mean efffiieny, Jn he high air igh rooms, fresh air mus be fed foribly when a range hood is operaed in order o resri he depressure in he room. In his experimen, he apure apaiy was measured when he air was supplied ino a model kihen of 3.6mX3.6m floor. The air was blown off from a exernal fan hrough a inle por a he op of he developed hood. On he inle pgr,louvers are insalled horizonally, allowing he air direion o vary verially, The area equivalen o learane per uni floor area ( rxa/ A) was abou 0.4nl/ rrf. The apure apaiy was ompared wih he blowing off direions wih 80% of exausl flow rae. Fig. 15 shows he resuls of a gas ho plae. The apaiy was found o be lowered only when he air was fed downward. I was surmised ha he negaive pressure was generaed a he hood fron end due o he supply ai flow, and buoyan 100.--- ---..,... plume overflowed from he hood fron by being suked o he negaive pressure porion, whih lower he apure effiieny. Then, he apure apaiy was ompared when he raio ofhe feed air from a du was hanged. Fig.16 shows he resuls obained wih a gas ho plae. When he air feed rae was se a 0, ha is, he air was supplied only from he raks, he apure apaiy was influened. This indiaes ha he supply air flow rae has an opimum range whih does no affe he effiieny. 5 IO J.... ffi 70 l ' 100 horizonal. LCMWd JO" dawniard 30", i nlel~ lla'51x0.8 inoul 3100k.ll/hr 400 Vonl oling Rae (nl/hr) Fls.15 Perfomine on Bia.Ing Direion of Inle.(~!!!!L e!~.!!) 405
Finally, he apaiy of buoyan plume from a elei ho plae was examined. From Fig.17, he effe of direion and air feed rae on he apure effiieny seems o have nearly he same endeny. However, in eiher ase, he lowering rae of effiiey is greaer han ha of he gas one. As shown during hese dynami experimens,he haraerisis of slow exaus asending speed generaed by eleri applianes an be hough o work negaively. CONCLUSION This researh and developmen has made i lear ha he venilaion rae an be redued o 300rrf /h while mainaining 100% effiieny. I was also onfirmed ha lowering he insallaion high an provide higher effiieny. Finally, he resuls of he dynami ess show ha he effiieny are grealy affeed by feeble horizonal air urren. Wih hese researhes and onrivanes, he kihen venilaion should be brough ino a sysem, and leaner and more omforable kihen and living spaes ould be reaed.! inl1-..... xo.a inl... m.xo.s inl1-o hf'i1onal l>liwine inov 320Clall)w 100 loo loo ~ $00 Voni la Ing Rae (rrl{hr) Fig,16 Pw1...a <11 V1ri..,. lnie Rae (pas ho pl1o) 100,.. )J)Jl «II Vonl la Ing Rae (rrlfhrl Fl 17 Pw...-"' v..-1... Inle (eleri ho plae) REFERENCES. :,, 1. Ying YU, e al. (1988) The Buoyan Plume Charaerisis from.., :q Gasrange for Cooking. Summaries of Tehnial Papers of Annual ';., Meeing Arhieural Insiue of Japan : 0811-812. I! 2.Kenzo S (1987) The Improvemen of he Effiieny of he Range Hood?~? Summaries of Tehnial Papers of' Annual Meeing Arhieural ; 1 Insiue of Japan : D 1091-1092. "...! ~ 11! 3.Hase K e al. (1988) Sud on Venilaion for Kihen -Diffusion!I' ii Charaerisis of Conaminans in Buoyan Plumes a ove Cooking n~~ Applianes-. Summaries of Tehnial Papers of Annual Meeing..,.. '""'. Arhieural Insiue of Japan : 0809-810., o ll 111 406