scholarly journals Vortex heat transfer enhancement on energy-efficient surfaces structured by inclined trench dimples

2021 ◽  
Vol 2119 (1) ◽  
pp. 012016
Author(s):  
S A Isaev ◽  
N I Mikheev ◽  
N S Dushin ◽  
A E Goltsman ◽  
D V Nikushchenko ◽  
...  
Keyword(s):  
Energy Efficient ◽  
Longitudinal Velocity ◽  
Narrow Channel ◽  
Longitudinal Component ◽  
Experimental Measurements ◽  
Transfer Enhancement ◽  
Air Velocity ◽  
Flow Acceleration ◽  
Numerical Predictions ◽  
Sst Turbulence Model

Abstract Experimental measurements and numerical predictions of the longitudinal component of the air velocity in a narrow channel with two rows of 26 densely packed oval trenches at angles of ±45° and ±135° in laminar (Re=103) and turbulent (Re=4×103) regimes have been compared. The acceptability of the RANS approach using the modified SST turbulence model within the Rodi–Leschziner–Isaev approach has been substantiated. The flow acceleration in the dimpled channel up to the longitudinal velocity maxima of 1.85 and 1.55 of the average bulk velocity for laminar and turbulent air flows has been experimentally confirmed.

scholarly journals Vortex heat transfer enhancement in the separated flow near structured dimpled surfaces

2021 ◽  
Vol 2057 (1) ◽  
pp. 012002
Author(s):  
S A Isaev ◽  
I A Popov ◽  
N I Mikheev ◽  
S V Guvernyuk ◽  
M A Zubin ◽  
...  
Keyword(s):  
Shear Flow ◽  
Maximum Velocity ◽  
Separated Flow ◽  
Field Measurements ◽  
Narrow Channel ◽  
Transfer Enhancement ◽  
Flow Core ◽  
Flow Acceleration ◽  
Inclination Angles ◽  
Windward Slope

Abstract The numerically discovered phenomena of abnormal enhancement of the separated flow in the inclined oval-trench dimple (OTD) and the flow acceleration in the dimpled narrow channel are substantiated experimentally. The analysis of turbulent flow around a deep OTD on the plate and on the channel wall show that within the inclination angle range from 25° to 85°, the pressure drop is seen between the zones of stagnation on the windward slope and of rarefaction in the place where a tornado-like vortex is generated. The velocity field measurements in the narrow channel with two rows of inclined OTDs at the inclination angles of ±45° and ±135° reveal that the shear flow with a maximum velocity in front of the dimple entrance is formed in the flow core. This maximum shear flow velocity exceeds the maximum velocity in the plane-parallel channel.

An Appraisal of the Paper by O'Carrol et al. (1990)

1995 ◽  
Vol 209 (3) ◽  
pp. 203-205 ◽  
Author(s):  
A Strozzi ◽  
A Unsworth
Keyword(s):  
Finite Element ◽  
Finite Elasticity ◽  
Experimental Measurements ◽  
Linear Elastic ◽  
Numerical Predictions ◽  
Elasticity Effects

The paper by O'Carrol et al. (1), which addresses the problem of an elastomeric disc indented by a spherical punch, has been evaluated. The sources of disagreement between linear elastic numerical predictions and experimental measurements noted in this paper have been critically examined in the light of finite element forecasts obtained with a package which incorporates finite elasticity effects and incompressibility.

Experimental Measurements Research on Internal Micro-Environment of Individually Ventilated Cage System

2013 ◽  
Vol 401-403 ◽  
pp. 1044-1047
Author(s):  
Dong Xie ◽  
Shun Quan Mo
Keyword(s):  
Laboratory Animal ◽  
Close Correlation ◽  
National Standards ◽  
Air Distribution ◽  
Experimental Measurements ◽  
Internal Environment ◽  
Air Velocity ◽  
Cage System ◽  
Environment Parameters ◽  
Edge Side

This paper firstly presents the operation principle of individually ventilated cages (IVC) system. Measurements on micro-environment of IVC system in laboratory animal room at University of South China are conducted to attain the internal environment parameters (Temperature, humidity, air velocity, air cleanliness and noise). Research results show that internal micro-environment parameters basically meet national standards about the barrier environment, but internal air distribution is uneven. In IVC system, air velocities in the edge side are higher than in the middle side, and the maximum air velocity is about 10% larger than the minimum value. Temperature in internal micro-environment depends on indoor temperatures which IVC system located in, and there has a close correlation between air velocity and temperatures. Internal environment evaluation could provide the first-hand research materials for guiding the breeding and management of laboratory animal.

Effects of Guide Vanes on the Tip Heat Transfer Enhancement of a Turbine Blade

2011 ◽  
Author(s):  
Gongnan Xie ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Enhancement ◽  
Turbine Blade ◽  
Pressure Loss ◽  
Transfer Enhancement ◽  
Guide Vanes ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Blade Tip

Gas turbine blade tips encounter large heat load as they are exposed to the high temperature gas. A common way to cool the blade and its tip is to design serpentine passages with 180-deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip life time. This paper presents numerical predictions of turbulent fluid flow and heat transfer through two-pass channels with and without guide vanes placed in the turn regions using RANS turbulence modeling. The effects of adding guide vanes on the tip-wall heat transfer enhancement and the channel pressure loss were analyzed. The guide vanes have a height identical to that of the channel. The inlet Reynolds numbers are ranging from 100,000 to 600,000. The detailed three-dimensional fluid flow and heat transfer over the tip-walls are presented. The overall performances of several two-pass channels are also evaluated and compared. It is found that the tip heat transfer coefficients of the channels with guide vanes are 10∼60% higher than that of a channel without guide vanes, while the pressure loss might be reduced when the guide vanes are properly designed and located, otherwise the pressure loss is expected to be increased severely. It is suggested that the usage of proper guide vanes is a suitable way to augment the blade tip heat transfer and improve the flow structure, but is not the most effective way compared to the augmentation by surface modifications imposed on the tip-wall directly.

scholarly journals Aerodynamic adaptivity criterion in the production methodology of the energy-efficient mine turbomachines

2020 ◽  
Vol 177 ◽  
pp. 03004
Author(s):  
Vladimir Makarov ◽  
Nikolai Makarov ◽  
Alexandr Lifanov ◽  
Artem Materov ◽  
Nikolay Kosarev
Keyword(s):  
Energy Efficient ◽  
Oil And Gas ◽  
Cost Effective ◽  
Mapping Method ◽  
Industrial Safety ◽  
Competitive Growth ◽  
Flow Acceleration ◽  
Russian Economy ◽  
Conformal Mapping Method ◽  
Effective Performance

Competitive growth of enterprises in the mining and oil and gas industries of the Russian economy, combined with industrial safety requirements, updates the task of developing the design and production methodology for the aerodynamically adaptive turbomachines with a nature-like dominance. Such machines adequately and economically soundly establish the necessary parameters of the air environment in the technological space that implement the concept of optimal subsurface management ecotechnology. This article proposes a production methodology for the energy-efficient turbomachines using the aerodynamic adaptability criterion that determines the relations between the velocity circulation and flow acceleration around the vane cascade profiles as the nature-like dominance of the process for converting the mechanical rotational energy of impeller into the internal energy of the air flow. The Karman theory of bound and free vortices, the Chaplygin-Joukowski-Kutta hypothesis, the conformal mapping method, and curve irregularities are used for development of a mathematical model for controlling the aerodynamic adaptability. It is proved that the control dominant is the intensity of the sources distributed over the turbomachine impeller vane profile that determine the flow diffusivity and as a result the acceleration circulation around the profile. It has been experimentally confirmed that the use of profiles obtained using the proposed technique increases the aerodynamic adaptability coefficient of the turbomachine by 51%, while increasing the area of its cost-effective performance by at least 2 times.

Evaluation of Indoor Climate in Small University Lecture Hall

2016 ◽  
Vol 861 ◽  
pp. 369-375
Author(s):  
Mária Budiaková
Keyword(s):  
Thermal Comfort ◽  
Architectural Design ◽  
Winter Season ◽  
Lecture Hall ◽  
Experimental Measurements ◽  
Optimal Parameters ◽  
Indoor Climate ◽  
Air Velocity ◽  
Globe Temperature ◽  
The University

This paper is focuses on the evaluation of the indoor climate in the small university lecture hall. Providing the optimal parameters of thermal comfort in the interiors of a university is immensely important for the students of the university. Fulfilling these parameters is inevitable not only for the physiological needs of students but also for the required performance of students. Reconstruction took place in the small university lecture hall. The original windows were exchanged for the modern wood tight windows. Experimental measurements were carried out in the winter season in 2016 in this small university lecture hall in order to evaluate the thermal comfort after the reconstruction. The device Testo 480 was used for the measurements. Obtained values of air temperature, air relative humidity, air velocity, globe temperature and indexes PMV, PPD are presented in the graphs. Heating, operation and architectural design of the small university lecture hall were evaluated on the basis of the parameters of thermal comfort. In the conclusion of this paper, there are principles how to design new small university lecture halls. Furthermore, there are presented recommendations how to operate the existing small university lecture halls.

Расчетно-экспериментальное исследование влияния вдува/отсоса газа через перфорированную поверхность на пограничный слой при сверхзвуковом числе Маха

2021 ◽  
Vol 47 (21) ◽  
pp. 19
Author(s):  
П.А. Поливанов
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Stokes Equations ◽  
Numerical Data ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Navier Stokes Equations ◽  
Piv Method ◽  
Sst Turbulence Model ◽  
Method Analysis

In this paper a numerical and experimental study of the effect of blowing/suction through a perforated surface on a turbulent boundary layer at a Mach number M = 1.4 is carried out. Most of the calculations were performed by Reynolds-averaged Navier-Stokes equations with the k-w SST turbulence model. The calculated geometry completely repeated the experimental one including the perforated surface. The numerical data were compared with experimental measurements obtained by the PIV method. Analysis of the data made it possible to find the limits of applicability of the numerical method for this flow.

Design of a Microfin Array Heat Sink Using Flow-Induced Vibration to Enhance the Heat Transfer Rate in the Laminar Flow Regime

2001 ◽  
Author(s):  
Jeung Sang Go ◽  
Geunbae Lim ◽  
Hayong Yun ◽  
Sung Jin Kim ◽  
Inseob Song
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Flow Regime ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Transfer Enhancement ◽  
Air Velocity ◽  
Flow Induced Vibration

Abstract This paper presented design guideline of the microfin array heat sink using flow-induced vibration to increase the heat transfer rate in the laminar flow regime. Effect of the flow-induced vibration of a microfin array on heat transfer enhancement was investigated experimentally by comparing the thermal resistances of the microfin array heat sink and those of a plain-wall heat sink. At the air velocities of 4.4m/s and 5.5 m/s, an increase of 5.5% and 11.5% in the heat transfer rate was obtained, respectively. The microfin flow sensor also characterized the flow-induced vibration of the microfin. It was determined that the microfin vibrates with the fundamental natural frequency regardless of the air velocity. It was also shown that the vibrating displacement of the microfin is increased with increasing air velocity and then saturated over a certain value of air velocity. Based on the numerical analysis of the temperature distribution resulted from microfin vibration and experimental results, a simple heat transfer model (heat pumping model) was proposed to understand the heat transfer mechanism of a microfin array heat sink. Under the geometric and structural constraints, the maximum heat transfer enhancement was obtained at the intersection of the minimum thickness of the microfin and constraint of the bending angle.

A Numerical Procedure for Modelling the Thermal Performance of Ventilated Hollow Core Slabs

2016 ◽  
Vol 846 ◽  
pp. 12-17
Author(s):  
Ahmed Faheem ◽  
Gianluca Ranzi ◽  
Francesco Fiorito ◽  
Cheng Wang Lei
Keyword(s):  
Turbulence Model ◽  
Thermal Performance ◽  
Numerical Procedure ◽  
Turbulence Models ◽  
Experimental Measurements ◽  
Hollow Core ◽  
Horizontal Pipe ◽  
Dimensionless Velocity ◽  
Nusselt Numbers ◽  
Numerical Predictions

This paper presents a numerical procedure for modelling the thermal performance of ventilated hollow core slabs (VHCS). A turbulence model suitable for this purpose is identified first by considering a smooth horizontal pipe subjected to turbulent mixed convention conditions typical of VHCSs. Comparison of the fully-developed dimensionless velocity (u+) and temperature (T+) profiles as well as the Nusselt numbers (Nu) predicted by five different turbulence models against empirical expressions available in the literature shows that the Standard and Realisable k-ε models provide the best overall predictions of u+, T+ and Nu. Since the Standard k-ε model gives slightly better estimates of the Nu values, it is adopted to model the thermal performance of a VHCS geometry for which experimental thermal responses are reported in the literature. The numerical predictions of local temperatures within the VHCS agree well with the experimental measurements, and hence the Standard k-ε model is recommended here for the modeling of VHCSs.

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