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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Liaw, Jane-SunnHas files: No

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    A Criterion of Heat Transfer Deterioration for Supercritical Organic Fluids Flowing Upward and Its Heat Transfer Correlation
    (2020-02-01)
    Li, Yung-Ming
    ;
    Liaw, Jane-Sunn
    ;
    Wang, Chi-Chuan
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    The main objective of this study was to develop the supercritical heat transfer correlation applicable for organic fluids when flowing upward in smooth tubes based on the available experimental data. The organic fluids contain R-22, R-134a, R-245fa and Ethanol and the associated heat transfer characteristics were compared with non-organic fluids like water and carbon-dioxide (CO2). It was found that the limit heat flux may result in heat transfer deterioration (HTD) of organic fluid and the corresponding values are much smaller than water or CO2. A new criterion to predict the HTD was developed and this criterion yields the best predictive ability against database. It was found that HTD occurs can be well described by the acceleration parameter evaluated at the wall condition rather than at bulk condition. For estimation of the supercritical heat transfer coefficient (HTC) for organic fluid, the present study proposes a new correlation with a physically based correction factor, which gives satisfactory predictions against the HTC of supercritical organic fluid. The new correlation can offer the smallest average deviation of 0.007 and standard deviation of 0.181 among the existing correlations.
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    A novel "partial bypass" concept to augment the performance of air-cooled heat exchangers
    (2012-09-01)
    Wang, Chi-Chuan
    ;
    Chen, Kuan-Yu
    ;
    Liaw, Jane-Sunn
    ;
    Tseng, Chih-Yung
    ;
    機械工程學系
    This study proposes a novel "partial bypass" concept which facilitates the heat transfer augmentation without the pumping power penalty. The basic idea is to introduce bypass cold stream which bypasses the front part of the heat exchanger and mixes with the hot stream across the front part of the heat exchanger, and the mixed stream flows through the rear part of the heat exchanger. Through this concept, heat transfer performance at the front part is slightly reduced but the rear part is substantially increased. The concept can be implemented with either maintaining the same total flowrate, heat transfer rate but accompanies with a much lower pressure drop or it can be applied with the same pumping power but accompanies with a much higher heat transfer rate. It is found that the "partial bypass" concept is especially fruitful for a heat exchanger with a comparatively large number of transfer unit (NTU). The concept is especially helpful in the design of a deep tube bank operated at lower frontal velocity. For validating the proposed concept, the calculation is also compared with the experimental measurements, and good agreement amid the calculations and measurements are reported. (C) 2012 Elsevier Ltd. All rights reserved.
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    An experimental study of the air-side performance of fin-and-tube heat exchangers having plain, louver, and semi-dimple vortex generator configuration
    (2015-01-01)
    Wang, Chi-Chuan
    ;
    Chen, Kuan-Yu
    ;
    Liaw, Jane-Sunn
    ;
    Tseng, Chih-Yung
    ;
    機械工程學系
    In this study, a comparative study of the airside performance of fin-and-tube heat exchangers having plain, louver, and semi-dimple vortex generator (VG) are made. A total of eighteen samples are made and tested with the corresponding fin pitch (F-p) being 1.6 mm and 2.0 mm and the number of tube row (N) are 1, 2 and 4, respectively. Test results indicate that the heat transfer coefficient for N = 1 for louver fin geometry with a smaller fin pitch of 1.6 mm is higher than that of semi-dimple VG and plain fin geometry. For N = 1 with a larger fin pitch of 2.0 mm, the semi-dimple VG is marginally higher than that of louver fin geometry when the frontal velocity is lower than 2 m s(-1). However, the trend is reversed where the heat transfer coefficient for louver fin outperforms that of semi-dimple VG when the velocity is increased further. For the airside performance for N = 2 or N = 4, the heat transfer coefficients for louver fin geometry is about 2-15% higher than those of semi-dimple geometry. The difference is increased with the rising velocity and the results prevail for both fin pitches. However, the difference is smaller at a larger fin pitch due to the comparatively effectively swirled motion of the semi-dimple VG. The effect of the number of tube row on the heat transfer coefficients is negligible for louver fin geometry and is also rather small for semi-dimple VG. For the plain fin geometry, the effect of tube row is also small when N > 1. The heat transfer performance for N = 1 is different from N = 2 or N = 4 due to its inline configuration. (C) 2014 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item type:Item,
    "A novel ""partial bypass"" concept to augment the performance of air-cooled heat exchangers"
    (2012-09-01)
    Wang, Chi-Chuan
    ;
    Chen, Kuan-Yu
    ;
    Liaw, Jane-Sunn
    ;
    Tseng, Chih-Yung
    ;
    機械工程學系
    "This study proposes a novel ""partial bypass"" concept which facilitates the heat transfer augmentation without the pumping power penalty. The basic idea is to introduce bypass cold stream which bypasses the front part of the heat exchanger and mixes with the hot stream across the front part of the heat exchanger, and the mixed stream flows through the rear part of the heat exchanger. Through this concept, heat transfer performance at the front part is slightly reduced but the rear part is substantially increased. The concept can be implemented with either maintaining the same total flowrate, heat transfer rate but accompanies with a much lower pressure drop or it can be applied with the same pumping power but accompanies with a much higher heat transfer rate. It is found that the ""partial bypass"" concept is especially fruitful for a heat exchanger with a comparatively large number of transfer unit (NTU). The concept is especially helpful in the design of a deep tube bank operated at lower frontal velocity. For validating the proposed concept, the calculation is also compared with the experimental measurements, and good agreement amid the calculations and measurements are reported. (C) 2012 Elsevier Ltd. All rights reserved."