scholarly journals ANALYSIS OF FLOW AND HEAT TRANSFER IN THE BOUNDARY LAYER OF FLUID WITH ESSENTIAL DEPENDENCE OF VISCOSITY FROM TEMPERATURE

2018 ◽  
Vol 40 (4) ◽  
pp. 13-18
Author(s):  
A.V. Timoshchenko ◽  
N.P. Dmitrenko ◽  
M.M. Kovetska
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Fluid Layer ◽  
Basalt Fiber ◽  
Melting Furnace ◽  
Flow And Heat Transfer ◽  
Temperature Regimes ◽  
Environmentally Safe ◽  
Basalt Melt

The introduction of new environmentally safe, durable and fire-resistant thermal insulation based on basalt fiber requires the improvement of technological processes for the production of basalt filaments in order to increase their energy efficiency. The quality of basalt fiber significantly depends on the properties of the basalt melt in the process. The process is considered to be more perfect than the more homogeneous and isotropic final properties of the melt. The conditions of flow and heat transfer in the bath and feeder of the melting furnace have a significant impact on the final properties of the melt. The paper presents the results of studies of heat transfer in the boundary layer on a flat plate with the flow of a liquid, the viscosity of which depends significantly on temperature. The system of differential equations, which describes the steady-state flow regime, is solved using symmetry analysis (analysis of Lie groups). On the basis of the developed mathematical model, new results were obtained which characterize the regularities of the flow and heat exchange of a highly viscous fluid in the range of temperature variations from 900 to 1450 ° C. The conditions for the formation of a low-mobility layer of liquid near a solid surface are determined. The influence of the value of a low-mobility fluid layer on the temperature distribution in the boundary layer of basalt melt is established. The results obtained allow us to adjust the temperature regimes in the melting furnace and improve the process of manufacturing ultrathin basalt threads.

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.

Flow and Heat Transfer in Branched Wavy Microchannels

2013 ◽  
Author(s):  
Pawan K. Singh ◽  
Hua Feng Samuel Tan ◽  
Chiang Juay Teo ◽  
Poh Seng Lee
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Aspect Ratio ◽  
Chaotic Advection ◽  
Wavy Channel ◽  
Flow And Heat Transfer ◽  
Boundary Layer Development ◽  
Novel Concept ◽  
High Pressure Zone ◽  
Wavy Channels

The Wavy channels are supposed to enhance performance of microchannel heat sink through chaotic advection. The change in boundary layer thickness (thinning) and the macroscopic mixing due to the formation of Dean’s vortices have been found to be main reasons for enhanced heat transfer in wavy microchannel. Present study carries out a detailed numerical investigation for flow and heat transfer in wavy channel. A 3D geometry for a single loop of wavy channel is modeled in GAMBIT and simulated in CFD software FLUENT. The basic dimensions were 0.15 mm width, 0.3 mm height and 1.5 mm length. The formation of Dean vortices are shown. In parametric study, the effect of Re number on the flow and heat transfer performance is shown. Heat transfer was found to be increased with Re. The effect of Aspect ratio is shown. The channel with the aspect ratio of 0.5 is found to be best among the channels studied including wavy and straight microchannels. A novel concept of secondary branches is introduced to wavy microchannel to take advantage of high pressure zone at crust. The branched wavy microchannel encouraged the secondary flow thus enhanced the macroscopic mixing. Due to disrupt of boundary layer development and its re-initialization, an improved thermal performance was achieved.

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