Flow and Heat Transfer in the Space Between Two Corotating Disks in an Axisymmetric Enclosure

1989 ◽  
Vol 111 (3) ◽  
pp. 625-632 ◽  
Author(s):  
C. J. Chang ◽  
C. A. Schuler ◽  
J. A. C. Humphrey ◽  
R. Greif
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Velocity Measurements ◽  
Flow And Heat Transfer ◽  
Gap Flow ◽  
Flow Reynolds Number ◽  
Improved Design ◽  
And Control ◽  
Gap Width ◽  
Disk Spacing

A numerical investigation was undertaken to characterize the laminar flow and heat transfer in axisymmetric coaxial corotating shrouded disk configurations. Attention was focused on calculation conditions favoring steady, stable, symmetric solutions of the conservation equations. The justification for this is based on velocity measurements obtained in a test section that matches the numerical configuration. Calculations were performed to investigate the dependence of the flow characteristics on disk angular velocity, disk spacing, and the disk–shroud gap width. Conditions involving a radial throughflow (blowing) and/or an axially directed disk–shroud gap flow were also predicted. In the region of the shroud the results show a strong sensitivity of the flow and heat transfer to variations in the flow Reynolds number (rotation) and Rossby number (blowing). By contrast, the flow was found to be less dependent on the disk spacing and the disk–shroud gap width for the conditions investigated. The introduction of an axially directed disk–shroud gap flow significantly alters the flow and heat transfer characteristics in the region between two disks. This finding is important for the improved design and control of corotating disk systems.

Innovatively Arranged Curved-Ribbed Solar-Assisted Air Heater: Performance and Correlation Development for Heat and Flow Characteristics

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Rajneesh Kumar ◽  
Abhishek Singh Kashyap ◽  
Paramvir Singh ◽  
Varun Goel ◽  
Khushmeet Kumar
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Roughness Element ◽  
Flow Characteristics ◽  
Solar Air Heater ◽  
Quasi Steady State ◽  
Air Heater ◽  
Relative Roughness ◽  
Flow And Heat Transfer ◽  
Gap Width

Abstract Solar radiation is a rich and clean source of energy. It can be collected and converted to thermal energy with the help of flat plate collectors called the solar-assisted air heater. Because of the low coefficient of heat transfer of air, the solar-assisted air heater has low thermal performance which can be improved by creating local turbulence using surface roughness on the heat transferring plate. The present investigation has been conducted to perceive the influence of the curved-ribbed element with gap on flow and heat transfer. The roughness element is defined by using five non-dimensionlized parameters, i.e., relative roughness width (W/w), relative roughness pitch (P/e), relative gap width (g/e), relative roughness height (e/D), and relative gap distance (d/x). The radius of the curvature of the curved rib-element is kept constant and the experimental measurements were done under quasi-steady state. The thermohydraulic performance parameter improved by 3.61 times the smooth flat plate solar air heater (SAH), in curved-ribbed SAH for W/w = 3, P/e = 8, g/e = 1, e/D = 0.045, and d/x = 0.65 at Reynolds number of 23,000. The generalized relation for heat transfer and flow characteristics is also being developed and the predicted Nusselt number and friction factor with the accuracy of ± 7.5% and ± 6.7%, respectively.

Analysis of Runback Water Flow on Anti-Icing Surface Using Volume-of-Fluid Method

2017 ◽  
Author(s):  
Mei Zheng ◽  
Wei Dong ◽  
Zhiqiang Guo ◽  
Guilin Lei
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Thin Liquid Film ◽  
Flow Characteristics ◽  
Volume Of Fluid ◽  
Complex Model ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Liquid Film Flow ◽  
The Mathematical Model

The runback water flow and heat transfer on the surface of aircraft components has an important influence on the design of anti-icing system. The aim of this paper is to investigate the water flow characteristics on anti-icing surface using numerical method. The runback water flow on the anti-icing surface, which is caused by the impinging supercooled droplets from the clouds, is driven by the aerodynamic shear forces and the pressure gradient around the components. This is a complex model of flow and heat transfer that considers flow field, super-cooled droplets impingement and runback water flow simultaneously. In this case of gas-liquid two phase flow, the Volume-of-Fluid (VOF) method is very suitable for the solution of thin liquid film flow so that it is applied to simulate the runback water flow on anti-icing surfaces in this paper. Meanwhile, the heat and mass transfer of the runback water flow are considered in the calculation using the User-Defined Functions (UDFs) in ANASYS FLUENT. The verification is conducted by the comparison with the results of the experimental measurement and the mathematical model calculation. The effect of the airflow velocity and contact angle on the water flow are also considered in the numerical simulation.

scholarly journals Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

2012 ◽  
Vol 16 (2) ◽  
pp. 593-603 ◽  
Author(s):  
M. Nili-Ahmadabadi ◽  
H. Karrabi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Flow Region ◽  
Air Gap ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Slip Ring

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

Experimental Investigation of Flow and Heat Transfer Characteristics Using Thermo-Sensitive Magnetic Fluid in a Mini-Channel

2007 ◽  
Author(s):  
Koji Fumoto ◽  
Masahiro Ikegawa
Keyword(s):  
Heat Transfer ◽  
Magnetic Fluid ◽  
Flow Characteristics ◽  
Force Convection ◽  
Transport Systems ◽  
Magnetic Characteristics ◽  
Flow And Heat Transfer ◽  
Zn Ferrite ◽  
Mini Channels ◽  
Increasing Temperature

In the present study, the flow characteristics and heat transfer of a thermo-sensitive magnetic fluid, which is a multiphase-flow material, were investigated experimentally. Heat transport systems using magnetic fluids have been proposed by several researchers, but miniature devices of this type have not yet been developed. The mini-channels considered herein have a depth of 500 μm, with the nominal channel width being five times the width. The channel device was constructed from a Teflon tube. The operation of the device is based on the thermo-magnetic characteristics of the fluid, a suspension of Mn-Zn ferrite particles in kerosene, the magnetization of which is known to decrease with increasing temperature. The experimental parameters were magnetic force, the position of the magnet, and the temperature of the magnetic fluid. The experimental results indicated that force convection based on the magnetic characteristics of the fluid in the mini-channel exhibited excellent cooling performance. In particular, the observed variations in the flow patterns were compared with the results of a boundary layer of the flow velocity in the pipe, which is generally known. Furthermore, it was found that the flow characteristic of the thermo-sensitive magnetic fluid was strongly dependent on the magnetic condition, such as the force and the position.

Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins

2003 ◽  
Author(s):  
D. Chakraborty ◽  
G. Biswas ◽  
P. K. Panigrahi
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stagnation Line ◽  
Flow And Heat Transfer ◽  
Annular Fin ◽  
Annular Fins

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.

Optimization of Flow and Heat Transfer for a New Double-Layered Microchannel Heat Sink

2019 ◽  
Author(s):  
Huanling Liu ◽  
Bin Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Microchannel Heat Sink ◽  
Transfer Performance ◽  
Temperature Uniformity ◽  
Flow And Heat Transfer ◽  
Fluent Simulation ◽  
New Type ◽  
Improved Design

Abstract In this paper, we propose a new type of DL-MCHS to improve the substrate temperature uniformity of the microchannel heat sink, and conduct the optimization of the New DL-MCHS. The heat transfer and friction characteristics of the novel DL-MCHS are studied by numerical simulation. We compare the heat transfer performance the new DL-MCHS with the traditional TDL-MCHS (the DL-MCHS with truncated top channels λ = 0.38). The results prove the effectiveness of the improved design by FLUENT simulation. When the inlet velocity is kept constant and coolant is water, the heat transfer performance of the New DL-MCHS is higher than that of TDL-MCHS leading to an increase of the temperature uniformity. In order to achieving the best overall heat transfer performance, an optimization of New DL-MCHS is performed by GA (genetic algorithm).

scholarly journals Flow Characteristic and Heat Transfer for Non-Newtonian Nanofluid in Rectangular Microchannels with Teardrop Dimples/Protrusions

Open Physics ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Zheyuan Zhang ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Gongnan Xie
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Relative Depth ◽  
Microchannel Heat Sink ◽  
Local Flow ◽  
Flow And Heat Transfer ◽  
Fanning Friction Factor ◽  
Limiting Streamlines

AbstractPorous cavity technology is one of the effective ways to improve local flow structures and thus the overall heat transfer of heat exchanging devices. In the present investigation, the flow characteristics and heat transfer in a microchannel heat sink with teardrop dimples/protrusions are studied with a numerical method. The working substances are Al2O3-water nanofluids, which are defined by power-law shear-thinning model. The relative depth and positive eccentricity of dimples/protrusions arranged in the microchannels are 0.2 and 0.3 respectively. The inlet velocity varies in the range of 1.41 m⋅s−1to 8.69 m⋅s−1and the volume fraction ranges from 0.5% to 3.5%. The effects of the flow and heat transfer characteristics are investigated by analyzing the limiting streamlines structures and temperature distributions. The overall thermal performance is evaluated by parameters of Fanning friction factor, Nusselt number and thermal performance. It is shown that the combination of teardrop dimple/protrusion structure and Al2O3-water nanofluids could effectively strengthen heat transfer with low pressure loss. Moreover, in order to obtain the best overall thermal performance, working substances with volume faction of 3.5% is preferred for the proposed microchannel structure.

Flow and Heat Transfer of Mist/Steam Two-Phase Flow in Two-Pass Rectangular Channels With Paralleled and V-Shaped Rib Turbulators

2018 ◽  
Author(s):  
Guangwen Jiang ◽  
Jianmin Gao ◽  
Xiaojun Shi ◽  
Wang Zhao ◽  
Yunlong Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Internal Cooling ◽  
Phase Flow ◽  
Transfer Performance ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Cooling Passage

The heat and flow characteristics of mist/steam two-phase flow in U-shaped internal cooling passage of gas turbine blade are studid numerically in this paper. The standard k-ε model was used as the turbulence model combined with the DPM model to calculate the influence of mist/steam mass ratio and mist diameter on flow and heat transfer of U-passage with different shaped ribs. The result indicates that under the same working condition, the U-shaped channel with 45 deg. V-shaped ribs has better heat transfer performance than other channels and heat transfer non-uniformity of the U-shaped channel with 75 deg. ribs is the worst among all channels studied in this paper. The heat transfer performance of the U-shaped channel with V-shaped ribs is higher than that of the channel with paralleled ribs. As for the mist/steam cooling in U-shaped passage with same ribs structure, heat transfer non-uniformity increases with the increasing of heat transfer performance. When mists diameter increases from 5μm to 15μm, the heat transfer performance of the Second-Flow-Passage increases obviously and the heat transfer non-uniformity increases at the same time. The heat transfer performance has not been further enhanced when the mists diameter continuously increases after mist diameter are larger than 10μm.

The Intertube Falling Film: Part 1—Flow Characteristics, Mode Transitions, and Hysteresis

1996 ◽  
Vol 118 (3) ◽  
pp. 616-625 ◽  
Author(s):  
X. Hu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Horizontal Tube ◽  
Falling Film ◽  
Flow And Heat Transfer ◽  
Transition Criteria ◽  
Continuous Sheet ◽  
Mode Transitions ◽  
Regime Map ◽  
Flow Regime Map

When a liquid film falls from one horizontal tube to another below it, the flow may take the form of discrete droplets, jets, or a continuous sheet; the mode plays an important role in the wetting and heat transfer characteristics of the film. Experiments are reported that explore viscous, surface tension, inertial, and gravitational effects on the falling-film mode transitions. New flow classifications, a novel flow regime map, and unambiguous transition criteria for each of the mode transitions are provided. This research is part of an overall study of horizontal-tube, falling-film flow and heat transfer, and the results may have important implications on the design and operation of falling-film heat exchangers.

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