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A mist flow which is an air flow with water-drop mixed may be suitable for rapid cooling. This paper shows how heat transfer was enhanced due to that the small quantity water-drop was vaporizing immediately near the heated wall, when the mist flow was spouted from entrance section of the channel.In the measurement of local heat transfer coefficients on a heating surface, the detailed temperature distribution was measured by using an infrared camera from an observation window. In the measurement of local temperature and humidity distribution, the detail of spatial temperature and humidity were also measured by using temperature and humidity sensor to observe the change of phase of mist. In this detail measurement result of temperature and humidity in the duct channel, the local heat transfer coefficient was increased at recirculation region, and reattachment region and downstream region of a backward-facing step. It was found that the relation between the situation of evaporation and enhancement of local heat transfer coefficients in the channel.

A detailed experimental investigation of the heat transfer and fluid flow characteristics of finned surfaces was conducted for airflow (ReL = 6250–25,000) at a flat plate boundary layer and narrow duct corresponding to 200 mm and 20 mm duct height, respectively. Short rectangular fins of either aluminum or resin material were attached in 7 × 7 arrays to a heating surface and the fin height, inclination angle and fin pattern (co-angular and zigzag) were varied. The fin spacing to length ratios along the streamwise and spanwise directions were kept at Sx/L = 2 and Sz/L = 1, respectively. T-type thermocouples and an infrared camera with a 160 × 120-point In–Sb sensor were used to measure the wall temperature and the detailed heat transfer at the endwall along with fin base. Dye flow in a water channel and titanium oxide oil film flow patterns around the fins were observed to study the flow behavior and its effect on heat transfer. In case of co-angular pattern flow stagnated in front of the fin and formed a strong horseshoe vortex around the fin while the longitudinal vortexes generated by the side top edges touched the fin surface and the endwall. On the other hand in case of zigzag pattern a weak horse shoe vortex appeared in front of the fin while the longitudinal vortex struck the endwall mainly and a sinusoidal wavy flow behavior was observed. The friction factor value was found to be almost constant and somewhat larger for a zigzag pattern of fins than for a co-angular pattern. The heat transfer results show that a narrow rectangular duct of 20 mm height with fin arrays in a zigzag pattern is the most effective, exhibiting a heat transfer enhancement at the endwall of more than four times over the case without fins wherein co-angular is the least recommended as it exhibits enhancement about a factor of more than three times. At flat plate boundary layer, i.e. in tall duct case both co-angular and zigzag patterns show almost same overall heat transfer enhancement about a factor of three times over the case without fins., 論文

As an augmentative means of forced convective heat transfer, relationships between the heat transfer and the flow behavior were experimentally investigated when the longitudinal vortex was artificially generated by single vortex generator in a pipe. The formation of vortices and then flow spiraling downstream were visualized by means of fluorescein and smoke as tracer of water and air flow, respectively. The velocity components were also measured using an inclined hot wire probe in three flow directions. The vortices rings being accompanied with longitudinal vortex as a kind of shear vortex gradually closed to the wall surface. It was found that the local heat transfer coefficients was mainly increased depending on the circumferential velocity component. Furthermore, a law of non-analogy between heat and flow was discussed about some locations taking accounts of both heat transfer coefficients and skin friction factors.

The temperature and the pressure distributions on a plate in underexpanded impinging jets are experimentally and numerically studied in this paper. The experiments were performed by measuring the adiabatic wall temperature using infrared imaging camera and the wall static pressures on the impinging plate and by visualizing density fields using schlieren method. Numerical calculations were conducted by solving two dimensional axisymmetric compressible Navier-Stokes equations and three dimensional compressible Euler equations. The comparison between the experiments and the calculations shows that the decrease in the stagnation temperature is caused by a recirculating flow carrying the cold air from the jet boundary to the stagnation point. The temperature and pressure ; contours on the impinging plate illustrate azimuthal structures for the circular nozzle, which are also confirmed by the three dimensional calculations., 論文

The temperature and the pressure distributions on a plate in underexpanded impinging jets are experimentally and numerically studied in this paper. The experiments were performed by measuring the adiabatic wall temperature using infrared imaging camera and the wall static pressures on the impinging plate and by visualizing density fields using schlieren method. Numerical calculations were conducted by solving two dimensional axisymmetric compressible Navier-Stokes equations and three dimensional compressible Euler equations. The comparison between the experiments and the calculations shows that the decrease in the stagnation temperature is caused by a recirculating flow carrying the cold air from the jet boundary to the stagnation point. The temperature and pressure ; contours on the impinging plate illustrate azimuthal structures for the circular nozzle, which are also confirmed by the three dimensional calculations.

A quantitative estimate of heat transfer enhancement is discussed here based on the measuements of local coefficients of heat transfer and friction for air flow over a range of Reynolds number from Re=9400 to 28200. Pairs of vortex generators consisting of two rectangular blades, increasing linearly in separation downstream, are aligned laterally to the flow with a spacing W. Characteristics of spanwise local heat transfer and pressure coefficients are found to vary differently over two regions of W. For small W, the phase of their distribution is shifted by 180° from the patterns observed just downstream of the blades. For large W, no phase change is observed but changes of the pattern between paired blades are distinctive. Overall heat transfer coefficients are more than double those for a smooth duct without generators. As a result, the performance ratio is greater than unity for all values of W., 論文

The longitudinal vortices were artificially generated by a single winglet vortex generator in a pipe. The longitudinal vortex enhances the heat transfer compared to other vortices produced by protrusions, because this longitudinal vortex does not decay until relatively further downstream. The purpose of this study is to know the informations about the flow motion of longitudinal vortex and the influence of vortices on heat transfer enhancement. The flow pattern was visualized by means of both fluorescein and rhodamine B, as a tracer of the water flow in a water table. The main vortex was spirally moved along the circumference and the behavior of other vortices was observed. Streamwise and circumferential heat transfer coefficients on the wall, wall static pressures, and velocity distribution in the overall cross section were also measured for air flow in the range of Reynolds number from 18 800 to 62 400. The distributions of streamwise heat transfer coefficients had a periodic pattern, and the peaks in the distribution moved circumferentially due to the spiral motion of the main vortex. Relation of the iso-velocity distribution and the wall static pressure to the heat transfer characteristics was shown. Moreover, the thermal performance was calculated under the condition of fixed pumping power, and it was found that the performance ratio is almost larger than unity., 論文

Heat transfer characteristics and flow patterns were measured over the plate for various separation distances between the nozzle exit and target plate when the air issuing from a sharpedged cross-shaped nozzle impinges on the plate. The local heat transfer coefficients in the radial direction for different circumferential positions were calculated using the wall temperatures measured by means of thermocouples, and the flow patterns were observed using a oil-titanium IV oxide method. The isotherms of the infrared images were also measured using an infrared radiometer with a two-dimensional array of InSb sensors. The geometric axes were switched due to the self-induced velocity of a vortex filament ; the convex corners became flat and the concave corners generated outward ejection. The distribution of the iso-heat-transfer-coefficient contours corresponds well to the flow pattern and the isotherm contours. These contours extended diagonally and demonstrated the Andrew's cross pattern for the short separations, subsequently becoming the octagonal patten, and then becoming circular at large separations. The correspondence of the heat transfer characteristic to the flow behaviors, and the heat transfer mechanism were also described., 論文

The characteristics of heat transfer and pressure distributions were measured by varying the clearances against the duct wall and the separations of the two thin plates for various arrangements of the thin plates which were oscillated by a flow in a parallel plate duct, with a view to enhancing the heat transfer along the duct. The maximum and mean Nusselt numbers have a Reynolds number dependence of Re^, and were 2.3 and l.6 times those in the fully developed turbulent flow, respectively, for air with Reynolds number ranging from 9000 to 37500. A relatively new technique, i.e., full field infrared imaging, was used to obtain the time and spatial temperature profiles on the wall surface. Contours of the isotherm of the infrared images correspond well to the heat transfer characteristics and flow behavior., 論文

The heat transfer coefficients and the pressure distributions were measured downstream of the backward facing step in which the heat transfer was actively or passively enhanced by following procedure. (1)The jet was ejected perpendicularly to the main flow from the portion on the opposite wall of the step. (2) The air flow was sucked from the recirculating zone. (3) A slat was inserted with an inclination to the main flow. These cause the main flow to curve sharply, and then the recirculating zone to shorten, so it is easy to control the lengths of the reattachment point, and consequently, the heat transfer. The thermal performance, η defined as the ratio of the heat transfer coefficient at the recirculating region with these modifications to that of a normal region, was calculated for equivalent pumping power, and it was found that η was larger than unity for the enhanced systems, except in the case of the discharge jet. It is effective to apply the enhancement of the heat transfer by active or passive methods to the suddenly expanding tunnel., 論文

Heat transfer coefficients were measured in the inner wall of a duct with an annular jet. The nozzle exit widths of the annular jets were varied by the change of diameter of the bluff plugs inserted at the duct inlet. The ratios of diameter of the bluff plug to that of the duct were chosen to be d/D＝0.6, 0.7, 0.8, 0.85 and 0.9. It is found that there are two regions of d/D where the characteristics of streamwise local heat transfer coefficients vary differently. For small d/D, the heat transfer mechanism depends on the flow field with a high turbulence intensity caused by the violent shear layer flow separated from the edge of the bluff plug. For large one, that depends on a wall jet like flow because the recirculating region formed back of the plug becomes large and makes the flow stable., 紀要論文

This paper shows how the local heat transfer coefficients along rectangular ducts are affected by the aspect ratios of a duct varying in the range 1.0～2.6 in order to obtain the basic information on the heat transfer mechanisms in both square and rectangular ducts. It was found that the streamwise local heat transfer coefficients at a lower wall are higher than that at a side wall except the aspect ratio AP＝1. As an aspect ratio increases, the local values on both walls increase, moreover the heat transfer coefficients at far downstream attain to the results obtained from the circular duct or the parallel plate duct. The dependency of an aspect ratio on the heat transfer characteristics of the rectangular duct is also presented., 紀要論文

Heat transfer coefficients were measured in the inner wall of a duct with an annular jet. The nozzle exit widths of the annular jets were varied by the change of diameter of the bluff plugs inserted at the duct inlet. The ratios of diameter of the bluff plug to that of the duct were chosen to be d/D＝0.6, 0.7, 0.8, 0.85 and 0.9. It is found that there are two regions of d/D where the characteristics of streamwise local heat transfer coefficients vary differently. For small d/D, the heat transfer mechanism depends on the flow field with a high turbulence intensity caused by the violent shear layer flow separated from the edge of the bluff plug. For large one, that depends on a wall jet like flow because the recirculating region formed back of the plug becomes large and makes the flow stable.

The local heat transfer coefficents were measured for three dimensional separated flow in order to obtain the basic information of heat transfer characteristics around the cylinder perpendicularly set the heating surface. The flow region was constructed by the three parts of lower. upper and back walls and its geometric configuration is like a T type having the duct connected perpendiculaly with straight duct. The working fluid, air. flows downstream against the adverse pressure gradient formed due to the existance of the back wall. The result of the heat transfer corresponds to the data obtained for the flow pattern in the visualization test by using oil film method. The Nusselt number at the flow detached from the wall surface exhibits its well-known Revnolds number dependence of Re^. On the back wall, the mechanism of the heat transfer is essentially the same to that of impingement jet flow., 紀要論文

This paper shows how the heat-transfer coefficients along heated tubes are affected by the clearance against the tube wall, the inlet angle and the widths of various types of blade wheels which are propelled by an internal flow in a circular tube and inserted at the inlet in order to augment heat transfer along the tube. The maximum and averaged heat-transfer coefficients in the region from blade position to far downstream were 3.0 and 2.2 times those in smooth duct respectively, for air ranging in Reynolds number from 15000 to 60000. Moreover, the performance evaluation was carrid out under the condition of fixed pumping power, and it was found that the performace ratio depends more on the inlet angle and the width of the blde than clearence, and the ratio is larger than one., 論文

The characteristics of the local heat transfer coefficient have been studied for a two-dimensional jet impinging perpendicular to a confined wall, with the spent air being collected in a duct which surrounds the jet delivery duct. From this experiment, the effects of the dimensionless distance between the jet exit and impingement wall, the ratio of the wall width to the jet width, and the Reynolds number on the local heat transfer are clarified. It is also confirmed that both the profiles of local pressure coefficients and the local heat transfer coefficients can be classified roughly into two patterns : that is, the bell-shaped and the flat profile., 紀要論文

The characteristics of the local heat transfer coefficient have been studied for a two-dimensional jet impinging perpendicular to a confined wall, with the spent air being collected in a duct which surrounds the jet delivery duct. From this experiment, the effects of the dimensionless distance between the jet exit and impingement wall, the ratio of the wall width to the jet width, and the Reynolds number on the local heat transfer are clarified. It is also confirmed that both the profiles of local pressure coefficients and the local heat transfer coefficients can be classified roughly into two patterns : that is, the bell-shaped and the flat profile.

平成17年度～平成19年度科学研究費補助金(基盤研究(C))研究成果報告書, 研究概要：（平成19年度時点）本研究は，超音速で流れる主流に対し，何らかの物質を注入し混合を促進させることを目的として，考案された装置の詳細な研究である．まず主流に対し垂直に噴射する際に噴射位置近傍を多孔壁とし，さらにその外側にキャビティを設置することで，へさき衝撃波近傍で多孔壁を通してキャビティ内を循環する流れが発生させる．これが主流内のはく離を低減し，キャビティ内における混合の促進につながると考えられる．ただしこのような複雑な流れ場は多くの要因が影響するため，高速度ビデオを用いた光学観察や詳細な圧力測定，さらに，3次元圧縮性Navier-Stokes方程式を解いた数値シミュレーションにより調べた．実験および計算条件として噴流を多孔壁上から噴射する場合と多孔壁から離れた位置で噴射するためのロッドを突き出す場合を設定し，ロッド，噴流，多孔壁およびへさき衝撃波の干渉の様子を調べた．このような実験および計算結果より，ロッドおよび噴流を多孔壁中央に設置した場合は，発生するへさき衝撃波により圧力差ができ，循環流れが発生することが明らかとなった．また複数のロッドおよび噴流をスパン方向に設置した場合はへさき衝撃波前後の圧力差が単一の場合よりも増加し，強い循環流れが発生することもわかった．このような研究成果は混合促進を前提とした装置の設計において極めて有効な指針を提供するものである.また本研究の計算において，多孔壁を通した流れの評価に用いたDoeffer-Bohningモデルも妥当であることが分かった．, 未公開：P.2以降（別刷論文のため）

平成13年度～平成16年度科学研究費補助金（基盤研究（B)(2)）研究成果報告書, 研究概要：本研究では、農業用灌漑用水の供給を目的として、自律型バッテリーレス太陽光発電システムの開発を行い、インターネットによる遠隔監視・制御システムを構築する。今年度は、以下の項目に関し研究と環境整備を行った。今年度は最終年度であるため、特に下記のすべてを統括する研究を行った。太陽光発電系:自律型インバータ周波数制御系:入力日射量の変化に応じ、インバータ出力周波数を可変する周波数制御系を構築した。この制御系は入力エネルギー(太陽エネルギー)の変化に応じて、出力(ポンプ回転数)の値を決定するサーボ機構を実現し、現在、晴天、曇り、雨天時における各種物理データの取得し、データベース構築を行った。インターネット遠隔制御系:無線LAN及び高速ディジタル回線(ISDN64K)により接続されたネットワーク回線を用いて、異なるプロトコルによるデータ通信技術による遠隔計測・制御システムの構築を行なった。ここでは、まず、気象データ、上記の太陽光発電システムの運転データ収集システムを構築し、それらのデータの属性を決定することによりデータベース化を行ない最適散水計画のアルゴリズムを構築した。最適な灌漑システム構築:農作物の成長・育成には、水分が不可欠となる。従って、培地における温度や湿度、および、日照等の自然環境と作物の必要水量を実験的・統計的に分析し、最適な灌漑システムの構築を行う。ここでは、実際に灌漑系を構築し、温室内での葉野菜の栽培を行うことにより際、作物の育成データを収集するための計測系を構築した。そして、実際に作物の要求水分量を計測し、最適散水計画による作物育種を行った。以上の3つのプロジェクトを統合し、最適な灌漑計画に基づき作物を育種するための自律型バッテリーレス太陽光発電システムの研究開発が実現できた。なお、この研究を遂行するにおいて、修士の学生が平成16年度太陽エネルギー学会の奨励賞を受賞した。, 研究概要：Natural energy is the focus of public attention as a clean substitutive energy for petroleum. In particular, photovoltaic solar power generation system is utilized for lighting as independent power source, and also begins to widen its sphere of activity in various fields. In general, the battery has been used to store the electric power that is unstable and variable photovoltaic solar energy. However, using a battery, we must consider the maintenance such as supplement of electricity liquid and securing of the storage place. In addition to that, destruction of battery has harmful influences on the environment, so we cannot avoid these problems. Therefore, the followings are required as a condition of independent power source. 1) To save the troublesome maintenance as much as possible. 2) To reduce harmful influences on environmental load. In this research, we could overcome the above two requirements and develop a photovoltaic solar power generation system with an autonomous battery-less, which is the purpose of the irrigation water for agriculture. Furthermore, we succeeded to establish a supervisory remote control system by the internet. Our main object is to build the remote measurement and control system of the agricultural growth condition in the greenhouse. To achieve that, the network communication system needs to be constructed based on wireless LAN and mobile PHS. To the consequence, we realize a fully automatic measurement and control system with no human labors.