Analogy between turbulent flows in curved pipes and orthogonally rotating pipes

1996 ◽  
Vol 307 ◽  
pp. 1-10 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Laminar Flows ◽  
Computational Results ◽  
Transfer Rates ◽  
Fundamental Parameters ◽  
Curved Pipes ◽  
Friction Factors

A quantitative analogy between fully developed turbulent flows in curved pipes and orthogonally rotating pipes will be described through similarity arguments, the use of experimental data and computational results. A pair of similarity parameters will be derived for each turbulent flow, so that they have the same dynamical meaning as those of laminar flows. When the second parameter for each flow is large enough, it will be shown that friction factors, as well as heat transfer rates, of the two flows coincide for equal values of the fundamental parameters. Computed contours of velocity and temperature will also reveal strong similarities between the two flows.

Analogy between laminar flows in curved pipes and orthogonally rotating pipes

1994 ◽  
Vol 268 ◽  
pp. 133-145 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Laminar Flows ◽  
Computational Studies ◽  
Flow Properties ◽  
Straight Pipe ◽  
Pipe Axis ◽  
Transfer Rates ◽  
Curved Pipe ◽  
Curved Pipes ◽  
Data Similarity ◽  
Friction Factors

The secondary flow of a viscous fluid, caused by the Coriolis force, through a straight pipe rotating about an axis perpendicular to the pipe axis is analogous to that of a fluid, caused by the centrifugal force, through a stationary curved pipe. The quantitative analogy between these two fully developed laminar flows will be demonstrated through similarity arguments, computational studies and the use of experimental data. Similarity considerations result in two analogous governing parameters for each flow, which include a new one for the rotating flow. When one of these analogous pairs of parameters of the two flows is large, it will be demonstrated that there are strong similarities between the two flows regarding friction factors, heat transfer rates, flow patterns and flow properties for the same values of the other pair of parameters.

scholarly journals A modified k - ε model of turbulence

1970 ◽  
Vol 38 ◽  
pp. 14-17 ◽  
Author(s):  
Showkat Jahan Chowdhury
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Mechanical Engineering ◽  
Computer Code ◽  
Computational Results ◽  
Consistent Model ◽  
Model Predictions ◽  
Computational Code ◽  
Flow Through

 In this paper, the parameters of a thermodynamically consistent k - ε model of turbulence are first determined, and the numerical values of the various model coefficients are evaluated. Limiting flows of a decaying homogeneous turbulence, turbulent flow in the inertial sublayer, and known properties of purely diffusive turbulence are used for this purpose. The thermodynamically consistent model is then incorporated into an enhanced version of the TEACH computer code called STARPIC. Finally, the modified computational code is used to simulate the flow through a channel to assess its capability in predicting turbulent flows. The computational results are compared with available experimental data, and found to have reasonable matching. The flows are also simulated using standard k - ε model, for comparison. It is observed that the present thermodynamically consistent modified k - ε model predictions are better compared to the standard k - ε model predictions.DOI: 10.3329/jme.v38i0.895 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.14-17  

scholarly journals Effect of the size of graded baffles on the performance of channel heat exchangers

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 767-775 ◽  
Author(s):  
Djamel Sahel ◽  
Houari Ameur ◽  
Touhami Baki
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Computer Code ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Enhancement Of Heat Transfer ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Friction Factors

The baffling technique is well-known for its efficiency in terms of enhancement of heat transfer rates throught channels. However, the baffles insert is accompanied by an increase in the friction factor. This issue remains a great challenge for the designers of heat exchangers. To overcome this issue, we suggest in the present paper a new design of baffles which is here called graded baffle-design. The baffles have an up- or down-graded height along the channel length. This geometry is characterized by two ratios: up-graded baffle ratio and down-graded baffle ratio which are varied from 0-0.08. For a range of Reynolds number varying from 104 to 2 ? 104, the turbulent flow and heat transfer characteristics of a heat exchanger channel are numerically studied by the computer code FLUENT. The obtained results revealed an enhancement in the thermohydraulic performance offered by the new suggested design. For the channel with a down-graded baffle ratio equal to 0.08, the friction factors decreased by 4-8%

Influence of Short Helical Tape on Local Convective Heat Transfer and Thermal Performance Characteristics in Turbulent Decaying Swirl Flow

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Smith Eiamsa-ard ◽  
Vichan Kongkaitpaiboon ◽  
Khwanchit Wongcharee
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Thermal Performance ◽  
Swirl Flow ◽  
Transfer Rates ◽  
Friction Factors ◽  
Plain Tube ◽  
Uniform Wall ◽  
Uniform Wall Heat Flux

This paper reports the experimental investigation of local convective heat transfer enhancement, flow friction and thermal performance factor behaviors in the tube fitted with the short helical tapes (SHTs) acting as decaying swirl flow generators. The tapes with three different helical tape angles (? = 90°, 135° and 180°) and three different channel numbers (N = 2, 3 and 4 channels) were tested under the uniform wall heat flux condition. The performance of each tape is compared with the performance of the plain tube subject to the same pumping power. The experimental results show that the heat transfer rates and friction factors of the tube with SHTs are respectively in range of 1.15 to 1.9 and 1.49 to 2.31 times of those in the plain, corresponding to thermal performances between 0.98 and 1.46. The correlations for Nusselt number (Nu) as a function of Reynolds number (Re), Prandtl number (Pr), helical tape angle (?) and the number of channel (N) are also developed.

Thermal Performance of a Heat Storage Module Using Calcium Chloride Hexahydrate

1984 ◽  
Vol 106 (1) ◽  
pp. 106-111 ◽  
Author(s):  
D. Dietz
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Phase Change ◽  
Calcium Chloride ◽  
Thermal Performance ◽  
Heat Storage ◽  
Heat Transfer Area ◽  
Transfer Rates ◽  
Chloride Hexahydrate ◽  
Change Material

The thermal performance of an air-heated/cooled, phase-change, heat stoage module was tested and evaluated. The module (rated at 38.7 kWh) consist of 130 vertically oriented tubes filled with 729 kg (1607 lb) of calcium chloride hexahydrate and enclosed in a rectangular box. Heat transfer rates measured during charging and discharging decreased with time as a result of decreasing effective heat transfer area and increasing thermal resistance of the phase-change material. These two dominant effects are included in a proposed mathematical model that predicted the experimental data.

Heat Transfer and Hydraulic Resistance in Turbulent Flow in Vertical Round Tubes At Supercritical Pressures. Part 1. Results From Numerical Simulations Using Algebraic Turbulent Viscosity Models

2020 ◽  
Author(s):  
Georgii Glebovich Yankov ◽  
Vladimir Kurganov ◽  
Yury Zeigarnik ◽  
Irina Maslakova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulent Flow ◽  
Hydraulic Resistance ◽  
Turbulent Viscosity ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Heating And Cooling ◽  
Prediction Techniques ◽  
Vertical Tubes

Abstract The review of numerical studies on supercritical pressure (SCP) coolants heat transfer and hydraulic resistance in turbulent flow in vertical round tubes based on Reynolds-averaged Navier-Stokes (RANS) equations and different models for turbulent viscosity is presented. The paper is the first part of the general analysis, the works based on using algebraic turbulence models of different complexity are considered in it. The main attention is paid to Petukhov-Medvetskaya and Popov et al. models. They were developed especially for simulating heat transfer in tubes of the coolants with significantly variable properties (droplet liquids, gases, SCP fluids) under heating and cooling conditions. These predictions were verified on the entire reliable experimental data base. It is shown that in the case of turbulent flow in vertical round tubes these models make it possible predicting heat transfer and hydraulic resistance characteristics of SCP flows that agree well with the existed reliable experimental data on normal and certain modes of deteriorated heat transfer, if significant influence of buoyancy and radical flow restructuring are absent. For the more complicated cases than a flow in round vertical tubes, as well as for the case of rather strong buoyancy effect, more sophisticated prediction techniques must be applied. The state-of-the-art of these methods and the problems of their application are considered in the Part II of the analysis.

scholarly journals Heat Transfer Enhancement by Detached S-Ribs for Twin-Pass Parallelogram Channel

Inventions ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 50 ◽  
Author(s):  
Shyy Chang ◽  
Wei-Ling Cai ◽  
Ruei-Jhe Wu
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Test Channel ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Performance Factors ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Measured Pressure

Detached S-ribs are proposed to arrange in the stagger manner along two parallelogram straight channels interconnecting with a 180° smooth-walled sharp bend for heat transfer enhancements. The detailed Nusselt number distributions over the two opposite channel endwalls at Reynolds numbers of 5000, 7500, 10,000, 12,500, 15,000 and 20,000 are measured using the steady-state infrared thermography method. The accompanying Fanning friction factors are evaluated from the measured pressure drops across the entire test channel. Having acquired the averaged heat transfer properties and Fanning friction factors, the thermal performance factors are determined under the criterion of constant pumping power consumptions. With the regional accelerated flows between the detached S-ribs and the channel endwall, the considerable heat transfer elevations from the Dittus–Boelter correlation levels are achieved. The comparative thermal performances between the two similar twin-pass parallelogram channels with detached 90° and S-ribs disclose the higher regional heat transfer rates over the turning region and the larger Fanning frictions factors, leading to the lower thermal performance factors, for present test channel with the detached S-ribs. To assist design applications, two sets of empirical correlations evaluating the regionally averaged Nusselt numbers and Fanning friction factors are devised for present twin-pass parallelogram channel with the detached S-ribs.

Pressure Drop and Heat Transfer in Turbulent Duct Flow: A Two-Parameter Variational Method

1995 ◽  
Vol 117 (2) ◽  
pp. 289-295 ◽  
Author(s):  
N. Ghariban ◽  
A. Haji-Sheikh ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Variational Method ◽  
Turbulent Flow ◽  
Turbulent Shear ◽  
Duct Flow ◽  
Turbulent Shear Stress ◽  
Fully Developed Turbulent Flow ◽  
Two Parameter

A two-parameter variational method is introduced to calculate pressure drop and heat transfer for turbulent flow in ducts. The variational method leads to a Galerkin-type solution for the momentum and energy equations. The method uses the Prandtl mixing length theory to describe turbulent shear stress. The Van Driest model is compared with experimental data and incorporated in the numerical calculations. The computed velocity profiles, pressure drop, and heat transfer coefficient are compared with the experimental data of various investigators for fully developed turbulent flow in parallel plate ducts and pipes. This analysis leads to development of a Green’s function useful for solving a variety of conjugate heat transfer problems.

Thermally Developing Single-Phase Flows in Microtubes

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Mehmed Rafet Özdemir ◽  
Ali Koşar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Single Phase ◽  
High Mass ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Friction Factors ◽  
Developing Flow ◽  
Theoretical Predictions

The pressure drop and heat transfer due to the flow of de-ionized water at high mass fluxes in microtubes of ∼ 254 μm and ∼ 685 μm inner diameters is investigated in the laminar, transition and the turbulent flow regimes. The flow is hydrodynamically fully developed and thermally developing. The experimental friction factors and heat transfer coefficients are respectively predicted to within ±20% and ±30% by existing open literature correlations. Higher single phase heat transfer coefficients were obtained with increasing mass fluxes, which is motivating to operate at high mass fluxes and under thermally developing flow conditions. The transition to turbulent flow and friction factors for both laminar and turbulent conditions were found to be in agreement with existing theory. A reasonable agreement was present between experimental results and theoretical predictions recommended for convective heat transfer in thermally developing flows.

Sign in / Sign up

Export Citation Format

Share Document