Investigation of the characteristics of turbulent flow and heat transfer induced by a vibrating piezoelectric fan on asymmetrical concave surfaces

2021 ◽  
pp. 095765092110260
Author(s):  
Xinjun Li ◽  
Weiwei Chen ◽  
Shihua Lu
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Convective Heat Transfer Coefficient ◽  
Displacement Function ◽  
Concave Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Offset Distance ◽  
Mesh Technique

This paper aims at performing an investigation numerically on the turbulent flow and thermal performances for an asymmetrical concave surface integrated with a slim vibrating piezoelectric fan. The dynamic mesh technique using a user defined function to describe the displacement function of vibrating cantilever beam is employed to model the deformation of the slim piezoelectric fan in time. Meanwhile, the SST k-ω turbulence model is chosen to capture the turbulence behavior of the flow and heat transfer. Two important factors, the relative curvature of the both sides of semicircular surfaces ( RK) and the dimensionless distance of fan offset along y-axis (Δ y/ APP) are taken into considerations during the simulation process. A considerable increase of local time-average heat transfer coefficients is observed in the vicinity of vibration envelope. The results show that the relative curvature ( RK) has a strong influence on the flow and heat transfer at both ends of the asymmetrical concave surface when its value is larger than 2. And by adjusting the dimensionless offset distance of the piezoelectric fan (Δ y/ APP), the area-averaged convective heat transfer coefficient can be increased by 20% on a small zone surrounding the fan with WPF ×  App (S1). The conclusions of this paper implement a theoretical attempt for expanding the application scenarios of piezoelectric fan.

Single Impinging Slot Jet on a Concave Surface: Inlet/Outlet Influence

2008 ◽  
Author(s):  
L.-E. Brizzi ◽  
T. K. D. Hoang ◽  
E. Dorignac ◽  
M. Fe´not
Keyword(s):  
Heat Transfer ◽  
Impinging Jet ◽  
Constant Heat Flux ◽  
Concave Surface ◽  
Classical Particle ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Heat Transfer Coefficients ◽  
Impingement Jet ◽  
Flow And Heat Transfer

An experimental study of fluid flow and heat transfer has been carried out for a single slot jet impinging on a concave surface. Experiments have been conducted with nozzle exit Reynolds number (Reb = 3200), dimensionless impinging height (H/b = 7) and relative curvature (Dc/b = 5) to determine the heat transfer coefficients under a constant heat flux condition by infrared thermography (≈ 500 samples). The distributions of mean velocity and velocity fluctuation on the concave surface have been measured by using classical Particle Image Velocimetry (≈ 5000 samples). The presence of an oscillatory impinging jet around three different positions has been observed. This type of behavior modifies considerably the impinging jet structure and the turbulence values which results in a modification the cooling efficiency. In order to use this type of jet for the optimization of the cooling of a concave surface, we propose to study, in this present study, the effect of Inlet/Outlet condition (riblets and obturator). The results underline the strong effect of outlet condition (e varies from 0 to 10 mm) for a single slot impingement jet on a concave surface. The flow is characterized by an oscillatory jet when the exit is totally opened (e = 10 mm) while the jet is stabilized at the opposite part for the closed exist (e = 0 mm). Therefore, the oscillatory impinging jet generated a uniform and symmetric heat transfer area while the stabilized impinging jet causes a dissymmetrical heat transfer.

Turbulent flow and heat transfer in pipes with buoyancy effects

1979 ◽  
Vol 94 (2) ◽  
pp. 383-400 ◽  
Author(s):  
A. M. Abdelmeguid ◽  
D. B. Spalding
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Dissipation Rate ◽  
Flow Resistance ◽  
The Other ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Velocity And Temperature Fields

A finite-difference procedure, is employed to predict the turbulent flow and heat transfer in horizontal, inclined and vertical pipes when influenced by buoyancy. The flow is treated as parabolic; and the turbulence model used involves the solution of two differential equations, one for the kinetic energy of turbulence and the other for its dissipation rate. Results are presented for the velocity and temperature fields, and the associated flow-resistance and heat-transfer coefficients. The predictions for horizontal and vertical pipes have been compared with the available experimental results, and the agreement obtained is good.

Analysis of Turbulent Flow and Heat Transfer in Internally Finned Tubes and Annuli

1979 ◽  
Vol 101 (1) ◽  
pp. 29-37 ◽  
Author(s):  
S. V. Patankar ◽  
M. Ivanovic´ ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Fully Developed Turbulent Flow

The fully developed turbulent flow and heat transfer characteristics for tubes and annuli with longitudinal internal fins were analyzed via a mixing length model. The model takes account of the proximity of both the fin surfaces and the tube wall as well as of the gradients in the radial and circumferential directions. Application was made to air flows, and a single adjustable constant in the model was fixed by comparisons with experimental data for the friction factor and the circumferential-average Nusselt number for internally finned tubes. The local heat transfer coefficients exhibited a substantial variation along the fin height, with the smallest value (essentially zero) at the base and the largest value at the tip. Lesser and more gradual variations were exhibited by the local heat transfer coefficients on the wall of the tube or annulus. In general, the fins were found to be as effective a heat transfer surface as the wall (per unit area). Average Nusselt numbers and friction factors are presented for both the tube and the annulus.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

scholarly journals FORCED CONVECTION DRYING OF INDIAN GROUNDNUT: AN EXPERIMENTAL STUDY

2017 ◽  
Vol 15 (3) ◽  
pp. 467
Author(s):  
Ravinder Kumar Sahdev ◽  
Mahesh Kumar ◽  
Ashwani Kumar Dhingra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Experimental Error ◽  
Linear Regression Analysis ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporative Heat Transfer

In this paper, convective and evaporative heat transfer coefficients of the Indian groundnut were computed under indoor forced convection drying (IFCD) mode. The groundnuts were dried as a single thin layer with the help of a laboratory dryer till the optimum safe moisture storage level of 8 – 10%. The experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by a simple linear regression analysis and consequently, the convective heat transfer coefficient (CHTC) was determined. The values of CHTC were used to calculate the evaporative heat transfer coefficient (EHTC). The average values of CHTC and EHTC were found to be 2.48 W/m2 oC and 35.08 W/m2 oC, respectively. The experimental error in terms of percent uncertainty was also estimated. The experimental error in terms of percent uncertainty was found to be 42.55%. The error bars for convective and evaporative heat transfer coefficients are also shown for the groundnut drying under IFCD condition.

scholarly journals Heat flow and heat transfer coefficient during crystallization under the pressure

2018 ◽  
Vol 157 ◽  
pp. 02036
Author(s):  
Richard Pastirčák ◽  
Ján Ščury ◽  
Tomáš Fecura
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Solidification Process ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Microstructure Modeling ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Solidification Processes ◽  
Precise Prediction

Estimation of the heat flow at the metal-mold interface is necessary for accurate simulation of the solidification processes. For the numerical simulation, a precise prediction of boundary conditions is required to determine the temperature distribution during solidification, porosity nucleation, microstructure development, and residual stresses. Determination of the heat transfer coefficients at the metal-mold interface is a critical aspect for simulation of the solidification process and the microstructure modeling of the castings. For crystallization under the pressure and for thin-walled castings, HTC evaluation is important due to the very limited freezing time.

Simulation of Heat Transfer to Turbulent Nanofluid Flow in an Annular Passage

2014 ◽  
Vol 925 ◽  
pp. 625-629 ◽  
Author(s):  
C.S. Oon ◽  
A. Badarudin ◽  
S.N. Kazi ◽  
M. Fadhli
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Titanium Oxide ◽  
Convective Heat Transfer Coefficient ◽  
Hot Water ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients

The heat transfer in annular heat exchanger with titanium oxide of 1.0 volume % concentration as the medium of heat exchanger is considered in this study. The heat transfer simulation of the flow is performed by using Computational Fluid Dynamics package, Ansys Fluent. The heat transfer coefficients of water to titanium oxide nanofluid flowing in a horizontal counter-flow heat exchanger under turbulent flow conditions are investigated. The results show that the convective heat transfer coefficient of the nanofluid is slightly higher than that of the base fluid by several percents. The heat transfer coefficient increases with the increase of the mass flow rate of hot water and also the nanofluid.

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