Article

The effect of the corrugation inclination angle on the thermohydraulic performance of plate heat exchangers

Chemical Engineering Research Group, Council for Scientific and Industrial Research, PO Box 395, Pretoria 0001, Republic of South Africa
International Journal of Heat and Mass Transfer 01/1985; DOI: 10.1016/0017-9310(85)90249-2

ABSTRACT It is well established that the inclination angle between plate corrugations and the overall flow direction is a major parameter in the thermohydraulic performance of plate heat exchangers. Application of an improved flow visualization technique has demonstrated that at angles up to about 80° the fluid flows mainly along the furrows on each plate. A secondary, swirling motion is imposed on the flow along a furrow when its path is crossed by streams flowing along furrows on the opposite wall. Through the use of the electrochemical mass transfer analogue, it is proved that this secondary motion determines the transfer process; as a consequence of this motion the transfer is fairly uniformly distributed across the width of the plates. The observed maximum transfer rate at an angle of about 80° is explained from the observed flow patterns. At higher angles the flow pattern becomes less effective for transfer ; in particular at 90° marked flow separation is observed.RésuméL'angle d'inclinaison entre les corrugations et la direction générale de l'écoulement représente un paramètre important dans la performance thermodynamique d'un échangeur de chaleur à plaques. L'application d'une technique améliorée pour la visualisation de l'écoulement a démontré qu'à des angles jusqu'à 80° le liquide coule essentiellement le long des corrugations dans chaque plaque. Un tourbillon secondaire est imposé sur l'écoulement le long d'une corrugation par l'interaction avec des écoulements le long de la paroi opposée. L'application de l'analogie électrochimique du transfert de matière prouve que ce tourbillon secondaire détermine le processus de transfert ; comme conséquence de ce mouvement il résulte une distribution assez équilibrée du transfert sur la largeur des plaques. Le maximum de la vitesse de transfert observé à un angle d'environ 80° est expliqué à base du profil de l'écoulement. A des angles plus élevés le profil de l'écoulement devient moins efficace pour le transfert; en particulier à un angle de 90° il résulte une nette séparation de l'écoulement.ZusammenfassungDer Neigungswinkel zwischen Plattenwellen und der allgemeinen Fliessrichtung ist ein wichtiger Parameter in der thermodynamischen Leistung eines Plattenwärme-austauschers. Die Anwendung einer verbesserten Technik der Sichtbarmachung der Fliessbewegung hat bewiesen, dass bei Winkeln bis 80° die Flüssigkeit grösstenteils längs der Furchen an jeder Platte fliesst. Die Strömung längs einer Furche erfährt eine sekundäre Wirbelbewegung durch die querlaufenden Strömungen längs der entgegengesetzten Wand. Die Anwendung der elektrochemischen Massenübertragungsanalogie liefert den Beweis, dass diese sekundäre Wirbelbewegung den Übertragungsprozess bestimmt ; als Konsequenz dieser Bewegung wird eine ziemlich gleichmässige Verteilung der Übertragung über die Breite der Platte erreicht. Das beobachtete Maximum der Übertragungsgeschwindigkeit bei einem Winkel von ungefähr 80° wird durch das beobachtete Fliessprofil erklärt. Bei höheren Winkeln wird das Fliessprofil weniger effektiv für die Übertragung; in einzelnen erscheint bei 90° eine klar sichtbare Trennung des Flusses.РефератYcтaнoвлeнo, чтo yгoл нaклoнa мeждy выcтyпaми плacтин и нaпpaвлeниeм пoтoкa являeтcя ocнoвным тepмoгидpaвличecким пapaмeтpoм плacтинчaтыч тeплooбмeнникoв. Пpимe-нeниe ycoвepшeнcтвoвaннoгo мeтoдa визyaлизaции тeчeния пoкaзaлo, чтo пpи yглaч вплoть дo 80° жидкocть движeтcя в ocнoвнoм вдoль выeмoк нa кaждoй плacтинe. Bтopичнoe зaкpyчeннoe движe-ниe нaлaгaeтcя нa тeчeниe вдoль выeмки в тoм cлyчae, кoгдa нaпpaвлeниe движeния пepeceкaeтcя пoтoкaми, движyшимиcя вдoль выeмoк нa пpoтивoпoлoжнoй cтeнкe. C пoмoщью элeктpoчими-чecкoй aиaлoгии мaccoпepeнoca пoкaзaнo, чтo этo втopичнoe движeниe oпpeдeляeт пpoцecc пepe-нoca. кaк cлeдcтвиe этoгo движeния пepeнoc пoчти oднopoднo pacпpeдeляeтcя пoпepeк шиpины плacтин. Пoлyчeннaя мaкcимaльнaя cкopocть тeплoпepeнoca пpи yглaч oкoлo 80° oбьяcняeтcя нaблюдaeмoй кapтинoй oбтeкaния. Пpи бoльшич yглaч oбтeкaния cтpyктypa тeчeния мeньшe влияeт нa пpoцecc пepeнoca, в чacтнocти, пpи 90° нaблюдaeтcя зaмeтный oтpыв пoтoкa.

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