Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Experimental Results

Local heat transfer and pressure drop measurements were made during condensation of a nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double-tube condensers. The inner tube was a 19.1mm o.d. corrugated copper tube with soldered wire fins on the outer surface. The outer tubes were smooth tubes with inside diameter D_i of 29.9 and 25.0mm. The pressure drop and the heat transfer coefficient based on the bulk vapor-to-wall temperature difference were considerably smaller for R114/R113 than for R113. The vapor phase mass transfer coefficient β_n was higher for larger test fluid mass velocity G and D_i. At constant values of G and D_i, β_n was higher for larger condensation mass flux. The radial distribution of the vapor temperature was affected by the vapor velocity, becoming flatter at the outer part of the annulus and steeper near the liquid-vapor interface as the vapor velocity increased.蒸気圧縮式ヒートポンプ、冷凍機などの成績係数を向上させるための一方策としてローレンツサイクルが提案され、このサイクルに近づけることのできる非共沸2成分混合冷媒が実用されつつある。しかし、この冷媒が凝縮する際には低沸点蒸気が不凝縮ガスと類似の挙動を示すため、凝縮伝熱性能が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器の性能向上を図るためには、凝縮液膜の熱抵抗と混合気の拡散抵抗の両者を減少させる必要がある。著者らは前提で純冷媒用の伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管環状部における非共沸混合冷媒R114/R113の凝縮実験を行い、圧力降下の摩擦成分は純冷媒に対する実験式で整理できること、凝縮側の熱抵抗にしめる気相の熱抵抗の割合は冷媒流量の増大につれて減少することを示した。そして、混合気相の物質伝達係数を円管上の強制対流凝縮理論から導かれた無次元パラメータを用いて整理した。しかし、より一般性のある整理式を得るためにはフィン形状、内外管径比などの影響を明らかにする必要がある。なお、フロン系非共沸2成分混合冷媒の管内、シェル側あるいは環状部における凝縮については最近多くの実験的研究が報告されているが、混合気相の物質伝達について検討したものは少なく、実験データの蓄積が望まれる。本報では、前報の内管とフィン配列が多少異なる管を内管とし、内径の異なる2種類の平滑管を外管とする水平二重管環状部におけるR114/R113の凝縮実験を行い、前報の結果と比較する。また、混合気相の温度分布測定結果についても述べる

Experimental Study of Condensation Heat Transfer from Downward-Facing Inclined Surfaces

Experiments were perfomed to study the effect of surface inclination on condensation heat transfer from downward-facing horizontal surfaces. A smooth surface and two low-finned surfaces with a length of 50mm were tested for condensation of R-113. The angle of inclination from the horizontal φ ranged from 0 to 90 deg. For the smooth surface, the heat tranfer coefficient α first decreased with the increasing of φ, then took a minimum near 5 deg, and then increased monotonically with further increasing φ. For the low-finned surfaces, α increased sharply with φ in the range of 0 to 30 deg, and then increased moderately with further increasing φ. The heat tranpfer coefficient for the better performing finned surface was 2.5, 9 and 12 times the smooth surface value for φ=0, 10 and 90 deg., respectively.電子素子の発熱密度の増大にともない、高性能の冷却法として浸漬冷却に対する関心が高まり、研究が盛んになっている。この冷却法では、発生蒸気を凝縮させるための凝縮器が必要となる。その形式として種々のものが検討されているが、容器の上面または側面を凝縮器として使用するものが最も簡便な方式であると考えられる。著者らはさきに下向き水平凝縮面下部に蒸気空間が存在する場合および凝縮面が液中に浸漬されている場合の熱伝達特性とその促進法について実験的に検討し、多孔質排液板を取付けたフィン付き面を使用することによって熱伝達が平滑面に比べて大幅に促進されることを見いだした。これは、フィン間溝部に充満した凝縮液が毛細管力によって効率良く多孔質排液板へ引き込まれ、フィン頂部が高性能の凝縮面として働くためである。同様の排液効果は伝熱面を傾斜させ、重力を利用することによっても期待できる。本報では平滑面と2種類のローフィン付き面をとりあげ、下向き面上の凝縮熱伝達に及ぼす伝熱面傾斜角の影響を冷媒R113を用いて実験的に検討する

A Case of Choroidal Neovascularization Secondary to Unilateral Retinal Pigment Epithelium Dysgenesis

Aim: To report a case of choroidal neovascularization secondary to unilateral retinal pigment epithelium dysgenesis (URPED), which was resistant to posterior subtenon injection of triamcinolone acetonide (STTA) and intravitreal bevacizumab injection (IVB). Case Report: An 8-year-old boy was referred to us because of a unilateral unique clinical appearance on funduscopic examination in his left eye (OS). A geometric lesion at the retinal pigment epithelium level of the interpapillomacular area was disclosed OS. The optic nerve was slightly hyperemic OS. Findings from the right fundus examination were normal. Based on these characteristic findings, he was diagnosed as having URPED. Best corrected Landolt ring chart visual acuity (BCVA) was 1.0 in both eyes. Twenty-three months after the first visit, the patient presented with visual disturbance OS. Funduscopic examination showed an expansion of the geometric lesion and the development of a subfoveal choroidal neovascularization (CNV). BCVA was 0.4 OS. Two-time STTA (40 mg/1 ml) was performed at the onset of CNV and 6 months later, and additional IVB (1.25 mg/0.05 ml) was done 10 months later for the treatment of CNV, but the geometric lesion and CNV were resistant to the treatment and continued to expand. Seven years after the first visit, the geometric lesion and the CNV kept expanding steadily. Conclusion: URPED is a rare clinical entity, and the prognosis of this disease is still unclear. The visual prognosis may depend on whether CNV fully develops

Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Correlation of Frictional Pressure Drop and Vapor Phase Mass Transfer

Frictional pressure gradient and vapor phase mass transfer correlations were developed for condensation of nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double tubes with an enhanced inner tube. The frictional pressure gradient data were correlated fairly well by a previously developed empirical equation for condensation of pure refrigerants. The vapor phase mass transfer correlation was based on the previous results for turbulent flow in smooth and rough tubes with and without surface suction. For given conditions of vapor and tube wall, the heat transfer coefficient can be calculated by using the correlations for the vapor phase mass transfer coefficient and the heat transfer coefficient for the condensate film. The calculated values agree with the measured data to a mean absolute deviation of 14.3%.蒸気圧縮式ヒートポンプ、冷凍機の成績係数向上させることのできる作動媒体として、非共沸2成分混合冷媒が有望視されており、最近その凝縮熱伝達に関する研究が開発に行われている。非共沸2成分混合冷媒が凝縮する際には、低沸点蒸気が不凝縮ガスと類似な挙動を示すため、熱伝達係数が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器については液膜の伝熱促進とともに混合気の物質伝達促進をはかる必要がある。著者らは伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管の環状部における冷媒R11およびR113ならびに非共沸混合冷媒R114/R113の凝縮な関する一連の実験を行い、圧力降下と熱伝達の特性を明らかにした。R114/R113に関する第1報では液膜の伝熱特性がR113の場合と同一であると仮定して、混合気相の物質伝達係数を求め、円管上の強制対流凝縮理論から導かれた無次元パラメータを用いてデータ整理を行った。また、圧力降下の摩擦成分は純冷媒に対する実験式によって良好に整理できることを示した。第2報では、第1報の内管とフィン配列が多少異なる内管を使用し、外管内径を2種類に変化させて混合気相の物質伝達特性をより詳細に調べた。その結果、第1報で得られた物質伝達の式は凝縮質量流束の影響をよく表現するが、質量速度の影響および予測精度に関しては十分でないことが明らかになった。本報では、管内の乱流熱・物質伝達に関する従来の実験および理論解析の結果をもとにして、より一般性のある物質伝達の整理式を導く。また、圧力降下の摩擦成分の整理法についても検討する。なお、記号表中には本報で用いる主な記号のみ列挙する。その他の記号は第2報と同一である

Macular Edema Formation and Deterioration of Retinal Function after Intravitreal Bevacizumab Injection for Proliferative Diabetic Retinopathy

Purpose: To report a case of proliferative diabetic retinopathy (PDR) showing transient macular edema (ME) and deteriorated retinal function after intravitreal bevacizumab injection (IVB). Methods and Results: A 53-year-old man received IVB (1.25 mg/0.05 ml) in both eyes for the treatment of PDR. There was no treatment-related complication. However, he complained of photopsia in both eyes 6 h after the injection. Slit-lamp examination revealed mild cellular infiltrations (1+) in the anterior chamber in both eyes. Optical coherence tomography showed ME formation in the left eye. Both full-field and multifocal electroretinography (ERG) revealed the deterioration of all parameters in both eyes compared with pretreatment. The inflammation in the anterior segment and ME disappeared 1 day after the injection. ERG parameters were improved 9 days after the injection, except for the N1 and P1 amplitude of multifocal ERG in the left eye. Conclusion: We propose that patients who undergo IVB should be carefully informed and followed up for possible complications including temporal ME formation and retinal function deterioration

Bilateral Optic Disc Anomalies Associated with PAX2 Mutation in a Case of Potter Sequence

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Stimulus-Dependent State Transition between Synchronized Oscillation and Randomly Repetitive Burst in a Model Cerebellar Granular Layer

Information processing of the cerebellar granular layer composed of granule and Golgi cells is regarded as an important first step toward the cerebellar computation. Our previous theoretical studies have shown that granule cells can exhibit random alternation between burst and silent modes, which provides a basis of population representation of the passage-of-time (POT) from the onset of external input stimuli. On the other hand, another computational study has reported that granule cells can exhibit synchronized oscillation of activity, as consistent with observed oscillation in local field potential recorded from the granular layer while animals keep still. Here we have a question of whether an identical network model can explain these distinct dynamics. In the present study, we carried out computer simulations based on a spiking network model of the granular layer varying two parameters: the strength of a current injected to granule cells and the concentration of Mg2+ which controls the conductance of NMDA channels assumed on the Golgi cell dendrites. The simulations showed that cells in the granular layer can switch activity states between synchronized oscillation and random burst-silent alternation depending on the two parameters. For higher Mg2+ concentration and a weaker injected current, granule and Golgi cells elicited spikes synchronously (synchronized oscillation state). In contrast, for lower Mg2+ concentration and a stronger injected current, those cells showed the random burst-silent alternation (POT-representing state). It is suggested that NMDA channels on the Golgi cell dendrites play an important role for determining how the granular layer works in response to external input