Katsuto Okada

Bio: Katsuto Okada is an academic researcher. The author has contributed to research in topics: Plate heat exchanger & Plate fin heat exchanger. The author has an hindex of 2, co-authored 4 publications receiving 76 citations.

Designs of the New Type Plate Heat Exchangers and their Heat Transfer Characteristics

Abstract: 前報までに得られた知見にもとづき, 新しい形状の伝熱板からなるプレート型熱交換器の開発を試みた。流路が二次元的な単純波型プレートで伝熱係数が極大を示すもの1種類と三次元的な流路をもつ多点接触の傾斜波型プレート6種類を試作した。いずれの伝熱板もそのプレス型の機械加工は容易であり, 前者の伝熱特性は前報までの知見をほぼ満足し既存の伝熱板にくらべ優れていることを確認した。後者のプレートは多点接触の構造をもち流体の高い圧力にも耐える特徴を有しており, 傾斜角度および波の間の距離の伝熱係数におよぼす影響を検討し, 好適なプレート形状を決定した。

Studies on the Heat Transfer Coefficient and Pressure Drop of Several Kinds of Plate Heat Exchanger

Abstract: プレート型熱交換器の乱流伝熱機構を解明するため前報においてはモデル実験により基礎的な検討を行数った。本報は各種の実用器のプレートを用いて実験を行ない強制対流における乱流伝熱係数および圧力損失におよほすプレート間隙および凹凸の形状などの諸因子の彰響を検討し, さらにモデル実験との関速性を考察した。結果として, プレート型熱交換器の伝熱係数は前回のモデル実験と同様, 平滑管に較べて約5倍にも向上することを示した。また相似形状のプレートについて伝熱係数および圧力損失に関する実験式を求めた。

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.