scholarly journals Investigations of scalar transfer coefficients in fog during the Coupled Boundary Layers and Air Sea Transfer Experiment : a case study

2004 ◽  
Author(s):  
Robert Farrington Crofoot
Keyword(s):  
Boundary Layers ◽  
Transfer Coefficients ◽  
Transfer Experiment

The Coupled Boundary Layers and Air-Sea Transfer Experiment in Low to Moderate Winds (CBLAST-LOW): Flux Profile Relationships Across the Coupled Boundary Layers

2002 ◽  
Author(s):  
John H. Trowbridge ◽  
James B. Edson ◽  
Wade R. McGillis ◽  
Albert J. Plueddeman ◽  
Eugene A. Terray ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Transfer Experiment ◽  
Flux Profile

scholarly journals Measurement of Unsteady Flow and Heat Transfer in a Linear Turbine Cascade

1992 ◽  
Author(s):  
X. Liu ◽  
W. Rodi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Boundary Layers ◽  
Suction Side ◽  
Turbine Cascade ◽  
Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Background Turbulence ◽  
Hot Film

A detailed experimental study has been conducted on the wake-induced unsteady flow and heat transfer in a linear turbine cascade. The unsteady wakes with passing frequencies in the range zero to 240 Hz were generated by moving cylinders on a squirrel cage device. The velocity fields in the blade-to-blade flow and in the boundary layers were measured with hot-wire anemometers, the surface pressures with a pressure transducer and the heat transfer coefficients with a glue-on hot film. The results were obtained in ensemble-averaged form so that periodic unsteady processes can be studied. Of particular interest was the transition of the boundary layer. The boundary layer remained laminar on the pressure side in all cases and in the case without wakes also on the suction side. On the latter, the wakes generated by the moving cylinders caused transition, and the beginning of transition moves forward as the cylinder-passing frequency increases. Unlike in the flat-plate study of Liu and Rodi (1991a) the instantaneous boundary layer state does not respond to the passing wakes and therefore does not vary with time. The heat transfer increases under increasing cylinder-passing frequency even in the regions with laminar boundary layers due to the increased background turbulence.

scholarly journals <i>Letter to the Editor</i> Simultaneous observations of the ionospheric footprint of flux transfer events and dispersed ion signatures

2002 ◽  
Vol 20 (2) ◽  
pp. 281-287 ◽  
Author(s):  
G. Provan ◽  
S. E. Milan ◽  
M. Lester ◽  
T. K. Yeoman ◽  
H. Khan
Keyword(s):  
Boundary Layers ◽  
High Latitude ◽  
Spectral Width ◽  
Field Of View ◽  
Magnetospheric Physics ◽  
Plasma Convection ◽  
Coherent Scatter ◽  
Flux Transfer Events ◽  
Letter To The Editor

Abstract. We perform a case study of a favourable conjunction of overpasses of the DMSP F11 and F13 spacecraft with the field of view of the Hankasalmi HF coherent scatter. At the time, pulsed ionospheric flows (PIFs) were clearly observed at a high-latitude in the radar field of view. The PIFs were associated with medium spectral width values and were identified as the fossilized signatures of pulsed dayside reconnection. Simultaneously, DMSP spectrograms from the two spacecraft showed dispersed ion signatures, observed equatorwards of the PIF signatures. We identified dayside high-latitude magnetosphere boundaries; these boundaries agreed well with those defined using the algorithm on the JHU/APL auroral particle website (Haerendel et al., 1978; Newell and Meng, 1988, 1995; Newell et al., 1991a, 1991b, 1991c; Traver et al., 1991). We conclude that in this case study the dispersed ion signatures map to regions of very newly-opened flux. It is only when this flux has convected polewards that the signatures of the PIFs with medium spectral widths are observed by the HF radars. These particular PIF signatures map to regions of mantle precipitation, i.e. recently reconnected flux.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (magnetopause, cusp and boundary layers; plasma convection)

Dynamic Design Optimization for Thermal Management: A Case Study on Shell and Tube Heat Exchangers

2019 ◽  
Author(s):  
Austin L. Nash ◽  
Neera Jain
Keyword(s):  
Heat Exchanger ◽  
Performance Metrics ◽  
Static Model ◽  
Transient Performance ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Component Design ◽  
Shell And Tube ◽  
Linearized Model

Abstract We present a new methodology for designing a heat exchanger that explicitly considers both static and transient performance characteristics. The proposed approach leverages 1) a highly detailed, albeit static model that captures the complex nonlinear relationship between heat exchanger geometry and heat transfer coefficients, and 2) a reduced-order dynamic model of the heat exchanger that approximates the geometry detailed in the static model. In order to optimize the component design for both static and transient performance metrics, pole locations of the corresponding linearized model are penalized in the cost function of the proposed optimization algorithm in order to move dominant poles further into the left half complex plane. Through a simulated case study for a shell and tube heat exchanger, we demonstrate how the proposed algorithm exploits the trade off between static design metrics, including mass and footprint, and the rate at which heat is removed from the primary fluid.

scholarly journals Impacts of Horizontal Resolution and Air–Sea Flux Parameterization on the Intensity and Structure of simulated Typhoon Haiyan (2013)

2019 ◽  
Author(s):  
Mien-Tze Kueh ◽  
Wen-Mei Chen ◽  
Yang-Fan Sheng ◽  
Simon C. Lin ◽  
Tso-Ren Wu ◽  
...  
Keyword(s):  
Surface Flux ◽  
Horizontal Resolution ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Transfer Coefficients ◽  
Typhoon Intensity ◽  
Flux Parameterization ◽  
Upper Level ◽  
Positive Effect

Abstract. This study investigates the impacts of horizontal resolution and surface flux formulas on typhoon intensity and structure simulations through the case study of the Super Typhoon Haiyan (2013). Three different sets of surface flux formulas in the Weather Research and Forecasting Model were tested using grid spacing of 1, 3, and 6 km. Both increased resolution and more reasonable surface flux formulas can improve typhoon intensity simulation, but their impacts on storm structures are different. A combination of decrease in momentum transfer coefficient and increase in enthalpy transfer coefficients has greater potential to yield stronger storm. This positive effect of more reasonable surface flux formulas can be efficiently enhanced when the grid spacing is appropriately reduced to yield intense and contracted eyewall structure. As resolution increases, the eyewall becomes more upright and contracted inward. The size of updraft cores in the eyewall shrinks and the region of downdraft increases; both updraft and downdraft become more intense. As a result, the enhanced convective cores within the eyewall are driven by more intense updrafts within a rather small fraction of spatial area. This contraction of eyewall is associated with an upper level warming process, which may be partly attributed to air detrained from the intense convective cores. This resolution dependence of spatial scale of updrafts is related to the model effective resolution as determined by grid spacing.

The Coupled Boundary Layers and Air-Sea Transfer Experiment in Low to Moderate Winds (CBLAST-LOW): Flux Profile Relationships Across the Coupled Boundary Layers

2003 ◽  
Author(s):  
James B. Edson ◽  
Wade R. McGillis ◽  
Albert J. Plueddeman ◽  
Eugene A. Terray ◽  
John H. Trowbridge ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Transfer Experiment ◽  
Flux Profile

Possibilities of the Use of the Electrolytic Technique for the Investigations of Mass/Heat Transfer in Nanofluid

2016 ◽  
Vol 831 ◽  
pp. 216-222 ◽  
Author(s):  
Sebastian Grosicki
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Current Method ◽  
Annular Channel ◽  
Ion Concentration ◽  
Limiting Current ◽  
Transfer Coefficients ◽  
Transfer Experiment ◽  
Heat Transfer Coefficients ◽  
Physical Phenomena

In the paper the author presents the possibilities of the application of the electrolytic technique for the investigation of heat transfer coefficients in channels with nanofluids. The electrolytic technique called the limiting current method enables to obtain mass transfer coefficients on the basis of the electrochemical processes and the laws governing these physical phenomena. The exemplary graph presenting the limiting currents values resulting from the experiment is shown in Fig. 1. These are the voltammograms at different Reynolds numbers and the ion concentration Cb. Heat transfer coefficients can be calculated using the correlations describing the analogy of mass and heat transfer processes. Some cases of the possible application of the electrolytic technique and factors influencing the mass transfer experiment including the state of the electroactive surface, change in ion concentration and thickness of the diffusion layer are discussed in [1]. In this work the author focused on the mass transfer experiment with the application of the nanofluid. Special properties of the nanofluid should be taken into account in the investigations. The paper presents the preliminary results of the experiment with nanofluid in the annular channel.

scholarly journals Preliminary research on mass/heat transfer in mini heat exchanger

2018 ◽  
Vol 70 ◽  
pp. 02016
Author(s):  
Joanna Wilk ◽  
Sebastian Grosicki ◽  
Krzysztof Kiedrzyński
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Limiting Current ◽  
Experimental Facility ◽  
Transfer Coefficients ◽  
Transfer Experiment ◽  
Heat Transfer Coefficients ◽  
Flow Through ◽  
Mass And Heat Transfer

In the paper the authors present the facility for model investigations of heat/mass transfer in the exchanger characterised by small dimensions. Determination of heat transfer coefficients is an important issue in the design of mini heat exchangers. The built facility enables measurements of mass transfer coefficients with the use of limiting current technique. The coefficients received from the experiment are converted into heat transfer coefficients basing on the analogy between mass and heat transfer. The exchanger considered consists of nine parallel minichannels with a square cross-section of 2mm. In real conditions during the laminar flow through the minichannels the convective heat transfer occurs. Analogous conditions are maintained during the model mass transfer experiment. The paper presents the experimental facility and the preliminary results of measurements in the form of voltammograms. The voltammograms show the limiting currents being the base of mass transfer coefficient calculations.

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