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Lee C.-L.,Diwan University | Jou C.-J.G.,National Kaohsiung First University of Science and Technology
Fuel Processing Technology | Year: 2011

The furnace efficiency can be maintained or improved slightly by lowering the excess air ratio and raising the air preheat temperature in the heat furnace. The results obtained with a plant-size industrial furnace show that when the excess air oxygen concentration is reduced from 4% to 3%, the furnace efficiency is raised by 0.6%. However, raising the temperature of the pre-heated air will cause a higher furnace temperature and a faster flowing speed of the air in the furnace. Thus, the heat in the radiation zone of the furnace can be evenly transmitted to shorten the time for the fuel to reach the igniting point, and reduce the heat loss from the hot air stream. This will reduce the emission of CO2 and NOx. If the temperature of the pre-heated air is raised from 200 °C to 240 °C, about 2.3 × 106 m 3 of natural gas can be saved annually to reduce 3.1 × 10 3 t of CO2 and 14.3% of nitrogen oxide emissions. Such operational adjustments of the furnace using the recovered FG will save energy, reduce CO2 emission and alleviate the adverse impact to environment. © 2011 Elsevier B.V. All rights reserved.


Lee C.-L.,Diwan University | Jou C.-J.G.,National Kaohsiung First University of Science and Technology
Environmental Progress and Sustainable Energy | Year: 2012

Reducing the input excess air or airflow rate to a furnace or boiler will result in decreasing transmission rate of the thermal flow from the radiation zone to the convection heating surface zone in the furnace. Results of the plant-scale test presented in this article show that if the furnace is operated at 3.6 ×- 10 7 kcal/h of combustion capacity, decreasing the residual O 2 concentration in the furnace flue gas from 4% to 2.5% will save 9.3 × 10 3 m 3 of natural gas consumption, and 2.1 × 10 4 tons of CO 2 emission annually. For the boiler tested in the study, 1.8 × 10 5 m 3 of natural gas consumption and 3.9 × 10 5 tons of CO 2 emission will be reduced annually if it is operated with 90 ton/h steam yield. Hence, controlling the input excess air (or oxygen) as an important operating alternative to enhance thermal efficiency, and alleviate environmental impact of a heater furnace and boiler has been confirmed in this research. © 2011 American Institute of Chemical Engineers.


Cheng S.-J.,Diwan University
Water Resources Management | Year: 2010

Taiwan frequently experiences heavy rainfall events during the summer. The rainfall-runoff regeneration is an important job in specific areas where excessive rainfall causes serious flooding. The primary goal of this study is to generate and understand runoff components of the watershed outlet by using a conceptual model of three linear cascade reservoirs. The conceptual model is needless to determine direct runoff and excess rainfall in advance. Every linear cascade reservoir has an independent response function with an exponential expression. The outflows of the linear reservoirs represent streamflow components of a watershed outlet during rainfall-runoff processes, in which surface runoff is considered as quick runoff, whereas subsurface and groundwater runoffs are slow runoffs. In the simulation process, mean rainfall as model inputs were estimated using the block Kriging method. Available recordings of 68 rainfall-runoff events during 1966-2002 were used as the study sample. Fifty-four events were calibrated to determine the best hydrograph parameters and were used to compare simulation precision resulting from the model with those based on the Nash with NLP. The efficacy of the proposed model was verified using the remaining 14 observed rainfall-runoff data from an actual basin. The seven averaged parameters, which were applied for verification, show that the IUH shape of quick flow is more sharp-pointed with the peak shifted forward than that of slow flow. In rainfall-runoff processes, peak discharge of quick runoff is far larger than that of slow runoff, the time it takes for the peak discharge for a quick flow is earlier than that for a slow runoff, and the base time of a slow flow is longer than that of a quick flow. Furthermore, this study also found: (1) the base time of a slow runoff hydrograph is the same as that of a total runoff hydrograph; (2) the base time of a quick runoff hydrograph is contrariwise to the value of the soil antecedent moisture; (3) an amount of quick runoff is directly proportional to that of total runoff. These analytical results reveal that the model used in this study is suitable to evaluate hydrological conditions in this and other watersheds and can be further applied to watershed management in Taiwan. © 2010 Springer Science+Business Media B.V.


Hsiao K.-L.,Diwan University
Journal of Thermal Science | Year: 2010

In this study, a new and effective improved Semi-Analytic and Semi-Empirical formula f(Pr)= 0.749999437Pr1/2/(0.609 +1.221Pr 1/2 + 1.238Pr)1/4 has been proposed to solve a conjugate problem with free convection in the incompressible laminar boundary layer flow and heat conduction in a solid wall for the flow passing a flat plate fin. A combination of flat-plate flow and flat-plate fin heat conduction has been considered in the present study. Finite- difference solutions for the interface temperature profiles and the heat transfer rates have been presented over the entire thermo-fluid-dynamic field for Prandtl numbers from 0.001 to 10000. First, the similar flow field has been solved by the Runge-Kutta method and the shooting methods, then the correlation equation of the local heat transfer coefficient have been obtained. Finally, the empirical formula has been substituted into the fin temperature heat conduction calculation processes to obtain the iterative solutions of the conjugate problems. © 2010 Science Press and Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg.


Cheng S.-J.,Diwan University
Hydrological Processes | Year: 2010

This study explores the hydrograph characteristics of quick and slow runoffs in watershed outlet hydrographs. The quick and slow runoffs were modelled using a conceptual model of three linear cascade reservoirs that have exponential decay response expressions. Mean rainfall for model inputs was estimated using the block Kriging method. The 107 storms during the 1966-2008 events were classified as large, medium and small events according to the observed streamflow. The optimal hydrograph parameters for 61 rainfall-runoff events were calibrated using the shuffled complex evolution optimal algorithm. The efficacy of the model was verified using the seven averaged parameters of three types of 46 events and was compared with three evaluation criteria resulting from the Nash model. The 61 calibrations were used to analyse and compare the characteristics of quick and slow flows in early and later periods (1966-2002 and 2003-2008). Finally, the following five conclusions were obtained: (1) The base time of a slow runoff hydrograph is the same as that of a total runoff hydrograph. (2) A quick runoff with a long period occurs when soil antecedent moisture is low and with a short period under a high value. (3) The time to peak of hydrograph components is directly proportional to peak time of a hyetograph; the time to peak of quick and slow flows is about 0·97 and 1·12 times the peak time of a hyetograph, respectively. (4) The peak of hydrograph components is relative to a total runoff hydrograph; the percentages for quick runoff are approximately 71% and 13% for slow flow. Finally, (5) the volume of a quick runoff component is 49% of a total runoff volume and 37% for a slow runoff volume. © 2010 John Wiley & Sons, Ltd.


Cheng S.-J.,Diwan University
Journal of the American Water Resources Association | Year: 2010

This study investigates the characteristics of hydrograph components in a Taiwan watershed to determine their shapes based on observations. Hydrographs were modeled by a conceptual model of three linear cascade reservoirs. Mean rainfall was calculated using the block Kriging method. The optimal parameters for 42 events from 1966-2008 were calibrated using an optimal algorithm. Rationality of generated runoffs was well compared with a trusty model. Model efficacy was verified using seven averaged parameters with 25 other events. Hydrograph components were characterized based on 42 calibration results. The following conclusions were obtained: (1) except for multipeak storms, a correlation between base time of the surface runoff and soil antecedent moisture is a decreasing power relationship; (2) a correlation between time lag of the surface flow and soil antecedent moisture for single-peak storms is an increasing power relationship; (3) for single-peak events, times to peak of hydrograph components are an increasing power correlation corresponding to the peak time of rainfall; (4) the peak flows of hydrograph components are linearly proportional to that of total runoff, and the peak ratio for the surface runoff to total runoff is approximately 78 and 13% for subsurface runoff to total runoff; and (5) the relationships of total discharges have direct ratios between hydrograph components and observations of total runoffs, and a surface runoff is 60 and 32% for a subsurface runoff. © 2010 American Water Resources Association.


Hsiao K.-L.,Diwan University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2010

In this study, an analysis has been performed for heat and mass transfer with radiation effect of a steady laminar boundary-layer flow of a micropolar flow past a nonlinearly stretching sheet. Parameters n, K, k 0, Pr, Ec, and Sc represent the dominance of the nonlinearly effect, material effect, radiation effect, heat and mass transfer effects which have presented in governing equations, respectively. The similar transformation, the finite-difference method and Runge-Kutta method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles, the wall unknown values of θ′(0) and φ′(0) for calculating the heat and mass transfer of the similar boundary-layer flow are carried out as functions of n, Ec, k 0, Pr, Sc. The value of n, k 0, Pr and Sc parameters are important factors in this study. It will produce greater heat transfer efficiency with a larger value of those parameters, but the viscous dissipation parameter Ec and material parameter K may reduce the heat transfer efficiency. On the other hand, for mass transfer, the value of Sc parameter is important factor in this study. It will produce greater heat transfer efficiency with a larger value of Sc. © 2010 Springer Verlag.


Hsiao K.-L.,Diwan University
International Journal of Non-Linear Mechanics | Year: 2011

A magnetic hydrodynamic (MHD) mixed convective heat transfer problem of a second-grade viscoelastic fluid past a wedge with porous suction or injection has been studied. Governing equations include continuity equation, momentum equation and energy equation of the fluid. It has been analyzed by a combination of a series expansion method, the similarity transformation and a second-order accurate finite-difference method. Solutions of wedge flow on the wedge surface have been obtained by a generalized FalknerSkan flow derivation. Some important parameters have been discussed by this study, which include the Prandtl number (Pr), the elastic number (E), the free convection parameter (G) and the magnetic parameter (M), the porous suction and injection parameter (C) and the wedge shape factor (β). Results indicated that elastic effect (E) in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a wedge. In addition, similar to the results from Newtonian fluid flow and conduction analysis of a wedge, better heat transfer is obtained with a larger G and Pr. © 2010 Elsevier Ltd.


Cheng S.-J.,Diwan University
Natural Hazards | Year: 2011

This study evaluates how raingauge measurements affect estimations of areal hyetographs. The Thiessen polygon and block Kriging methods are used to calculate hourly mean hyetographs of rainfall events. Twelve rainfall events with complete recordings from all observation sites were used in this study. For the power semivariogram, a dimensionless semivariogram is a tool for obtaining hourly semivariograms resulting from standardized rainfall depth. Raingauge weight and three hyetograph characteristics were used as evaluation criteria. All raingauges were in turn subtracted from the original raingauge network, and raingauge effects were then compared with computations using all raingauges. Results of this study demonstrates (1) the block Kriging method is appropriate for describing rainfall process in a spatiotemporal structure (2) the Kriging method is an excellent method for obtaining exact mean rainfall, and (3) different raingauge networks influence mean hyetographs and should not be neglected. © 2010 Springer Science+Business Media B.V.


Cheng S.-J.,Diwan University
Natural Hazards | Year: 2011

This study mainly explores the best relationship between hydrograph parameters and urbanized factors in urbanized areas. Urbanization of a developing watershed is analyzed through 51 available rainfall-runoff simulations from 1966 to 2002. Forty of these rainfall-runoff events were calibrated to determine the relationships between impervious area and urbanized factors. During the calibration process, the block Kriging method was used to estimate the mean rainfall, and its hourly excesses were calculated by nonlinear programming. Then, clear tendencies between parameters and urbanized factors were produced by comparing the results of the annual average and optimal interval methods. The remaining eleven cases were used to verify the established relationships. The calibration and verification results confirm that the integral approaches used in this study can effectively illustrate the hydrological and geomorphic conditions in complex urbanized processes. Parameter n responds more sensitively than parameter k to increasing impervious area and population density. Additionally, parameter n responds more strongly to imperviousness than to population. Therefore, this study demonstrates that an impervious area is the main consequence of ongoing urbanization in the Wu-Tu watershed. The satisfactory results show that kernel response of the watershed would be more sharp-pointed and be shifted forward in peak due to an increased impervious cover. © 2010 Springer Science+Business Media B.V.

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