Hirotaka Konno

Bio: Hirotaka Konno is an academic researcher from Yamagata University. The author has contributed to research in topics: Heat transfer & Plate heat exchanger. The author has an hindex of 4, co-authored 20 publications receiving 112 citations. Previous affiliations of Hirotaka Konno include Tohoku University.

Simulation of limit-deposit velocity in horizontal liquid-solid flow

Abstract: The limit-deposit velocity at which a solid deposit begins to build up in the bottom of a pipe is numerically analyzed on the basis of a two-dimensional flow model and a comparison is made with experimental results. The model explains well the fact that the limit-deposit velocity increases with an increase in the delivered concentration of solids, and after reaching a maximum at a certain concentration it decreases gradually at higher concentrations. It is shown that, at lower solid concentrations, the shear stress acting on the surface of the bed of particles is the dominant factor for transporting the solids, while at higher concentrations the drag force of fluid within the bed plays a very important role.

Natural-Convection Heat Transfer around a Horizontal Array of Heated Cylinders in Air.

Abstract: 空気中において水平1列に配列した水平円柱群の自然対流熱伝達特性について実験的に考察した.3本配列および9本配列円柱群の双方に関して, 配列間隙を種々変化させて個々の円柱の熱伝達係数を測定した.その結果, 群の外端に位置する円柱とは明らかに差異があるものの, それ以外の他の円柱の熱伝達係数は互いにほぼ等しいことがわかった.そこで, 熱伝達係数に及ぼす円柱間隙の影響について簡単な考察を加え, それに基づいて上述の2種類の熱伝達係数に対して各々相関式を提出した.両相関式により熱伝達係数の全実験値が良好に表示し得た.

Natural‐convection heat transfer around a horizontal array of heated cylinders in air

Abstract: An experimental study was performed to determine the natural-convection heat transfer characteristics of horizontal cylinders placed in a horizontal line in air. Local heat transfer coefficients were measured for three- and nine-cylinder arrays in various cylinder-spacing arrangements. As a result, it was found that there were no major differences in heat transfer coefficient among cylinders, other than for the array-edge cylinders. The mean value of all cylinders was clearly different from that of the array-edge cylinders. Based on a simple consideration for the effect of cylinder-spacing on heat transfer coefficient, correlation equations were proposed for each kind of heat transfer coefficient mentioned above. All the experimental heat transfer coefficients were expressed well by these equations. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(6): 410–419, 1996

A theoretical approach to predict the performance of chevron-type plate heat exchangers

Abstract: Manufacturers of plate and frame heat exchangers nowadays mainly offer plates with chevron (or herringbone) corrugation patterns. The inclination angleof the crests and furrows of that sinusoidal pattern relative to the main flow direction has been shown to be the most important design parameter with respect to fluid friction and heat transfer. Two kinds of flow may exist in the gap between two plates (pressed together with the chevron pattern of the second plate turned into the opposite direction): the crossing flow of small substreams following the furrows of the first and the second plate, respectively, over the whole width of the corrugation pattern, dominating at lower inclination angles (lower pressure drop); and the wavy longitudinal flow between two vertical rows of contact points, prevailing at highangles (high pressure drop). The combined effects of the longer flow paths along the furrows, the crossing of the substreams, flow reversal at the edges of the chevron pattern, and the competition between crossing and longitudinal flow are taken into account to derive a relatively simple but physically reasonable equation for the friction factor ξ as a function of the angleand the Reynolds number Re. Heat-transfer coefficients are then obtained from a theoretical equation for developing thermal boundary layers in fully developed laminar or turbulent channel flow — the generalized Leveque equation — predicting heat-transfer coefficients as being proportional to (ξ·Re2)1/3. It is shown, by comparison, that this prediction is in good agreement with experimental observations quoted in the literature.

Plate Heat Exchanger Literature Survey and New Heat Transfer and Pressure Drop Correlations for Refrigerant Evaporators

Abstract: Plate heat exchangers are used regularly in the heating, ventilating, air conditioning, and refrigeration industry. There is an urgent need for detailed and systematic research regarding heat transfer and the fluid flow characteristics of these types of exchangers. As an initiative in this respect, a literature search is presented on plate heat exchangers. New correlations for evaporation heat transfer coefficient and friction factor are introduced, which are applicable to various system pressure conditions and plate chevron angles. The correlations are based on actual field data collected during several years of installation and operation of chillers, and they are intended to serve as design tools and perhaps as a starting point for future research.