Analysis of Heat Transfer and Fluid Flow Through a Spirally Fluted Tube Using a Porous Substrate Approach

1994 ◽  
Vol 116 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Vijayaragham Srinivasan ◽  
Kambiz Vafai ◽  
Richard N. Christensen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Porous Substrate ◽  
The Finite Element Method ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Friction Factors ◽  
Flow Through ◽  
Good Agreement

An innovative approach was opted for modeling the flow and heat transfer through spirally fluted tubes. The model divided the flow domain into two regions. The flutes were modeled as a porous substrate with direction-dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity, and ratio of the direction-dependent permeabilities were obtained from the geometry of the fluted tube. Experimental data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry were available. Experimental data from a few of the tubes tested were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matrix. Very good agreement was found between the numerical predictions and the experimental data.

Forced Convection in a Porous Channel With Discrete Heat Sources

2000 ◽  
Vol 123 (2) ◽  
pp. 404-407 ◽  
Author(s):  
C. Cui ◽  
X. Y. Huang ◽  
C. Y. Liu
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Experimental Results ◽  
Porous Channel ◽  
Heat Sources ◽  
Nusselt Numbers ◽  
Discrete Heat Sources ◽  
Flow Through ◽  
Good Agreement

An experimental study was conducted on the heat transfer characteristics of flow through a porous channel with discrete heat sources on the upper wall. The temperatures along the heated channel wall were measured with different heat fluxes and the local Nusselt numbers were calculated at the different Reynolds numbers. The temperature distribution of the fluid inside the channel was also measured at several points. The experimental results were compared with that predicted by an analytical model using the Green’s integral over the discrete sources, and a good agreement between the two was obtained. The experimental results confirmed that the heat transfer would be more significant at leading edges of the strip heaters and at higher Reynolds numbers.

Experimental and Numerical Studies of Heat Transfer in Human Uteri During Cryoablation

2002 ◽  
Author(s):  
Jim S. Chen ◽  
Kevin Agnissey ◽  
Marla Wolfson ◽  
Charles Philips ◽  
Thomas Shaffer
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Temperature History ◽  
Rubber Sheet ◽  
Numerical Studies ◽  
Numerical Predictions ◽  
Silicone Rubber Sheet ◽  
Nicolson Scheme ◽  
Sheet Good ◽  
Good Agreement

This paper presents experimental and numerical studies of transient heat transfer inside the uterus during application of a PFC (perfluorochemical) fluid into the endometrium cavity in order to achieve cryoablation. The numerical prediction is based on a 1-D finite difference method of the bio-heat equation using the Crank Nicolson scheme. The numerical method is first validated by a 1-D physical model by measuring temperature history at several locations within a silicone rubber sheet. Good agreement, thus positive predictability, was obtained by comparing numerical predictions with the experimental data obtained from eight intact, hysterectomized uteri during cryoablation.

Computation of Flow and Heat Transfer in Two-Pass Channels With 60 deg Ribs

2001 ◽  
Vol 123 (3) ◽  
pp. 563-575 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Moment Closure ◽  
Closure Model ◽  
Second Moment ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Sharp Turn ◽  
Second Moment Closure ◽  
Near Wall

Numerical predictions of three-dimensional flow and heat transfer are presented for a two-pass square channel with and without 60 deg angled parallel ribs. Square sectioned ribs were employed along one side surface. The rib height-to-hydraulic diameter ratio e/Dh is 0.125 and the rib pitch-to-height ratio (P/e) is 10. The computation results were compared with the experimental data of Ekkad and Han [1] at a Reynolds number (Re) of 30,000. A multi-block numerical method was used with a chimera domain decomposition technique. The finite analytic method solved the Reynolds-Averaged Navier Stokes equation in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model, and a two-layer k-ε isotropic eddy viscosity model. Comparing the second-moment and two-layer calculations with the experimental data clearly demonstrated that the angled rib turbulators and the 180 deg sharp turn of the channel produced strong non-isotropic turbulence and heat fluxes, which significantly affected the flow fields and heat transfer coefficients. The near-wall second-moment closure model provides an improved heat transfer prediction in comparison with the k-ε model.

scholarly journals Numerical Prediction of Flow and Heat Transfer in a Two-pass Square Channel with 90°Ribs

2001 ◽  
Vol 7 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Moment Closure ◽  
Closure Model ◽  
Second Moment ◽  
Square Channel ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Sharp Turn ◽  
Near Wall

Numerical predictions of three-dimensional flow and heat transfer are presented for a two-pass square channel with°parallel ribs. Square sectioned ribs were employed along the one side surface. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.125 and the rib pitch-to-height ratio(P/e)is 10. The computation results were compared with the experimental data of Ekkad and Han (1997) at a Reynolds number (Re) of 30,000.A multi-block numerical method was used with a chimera domain decomposition technique. The finite analytic method solved the Reynolds-Averaged Navier-Stokes equation in conjunction with a near-wall second-order Reynolds stress (secondmoment) closure model, and a two-layerk − εisotropic eddy viscosity model. Comparing the second-moment and two-layer calculations with the experimental data clearly demonstrated that the rib turbulators and the 180°sharp turn of the channel produced strong non-isotropic turbulence and heat fluxes, which significantly affected the flow fields and heat transfer coefficients. The near-wall second-moment closure model provides an improved heat transfer prediction in comparison with thek − εmodel.

PREDICTION OF FLUID FLOW AND HEAT TRANSFER THROUGH SQUARE DUCT WITH TWISTED TAPE INSERT AND INTERRUPTED RIB

2013 ◽  
Vol 37 (3) ◽  
pp. 917-925 ◽  
Author(s):  
Ho Keun Kang ◽  
Soo Whan Ahn ◽  
Myung Sung Lee ◽  
Dae Hee Lee
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Steel Sheet ◽  
Heat Transfer Performance ◽  
Twisted Tape ◽  
Square Duct ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Friction Factors ◽  
Carbon Steel Sheet

Numerical predictions of characteristics of turbulent flows through a square duct (30 × 30 mm) with twisted tape inserts and with twisted tape inserts plus interrupted ribs are conducted to investigate regionally averaged heat transfer and friction factors. The twisted tape is a 0.1 mm thick carbon steel sheet with a diameter of 28 mm, length of 900 mm and 2.5 turns. The present study demonstrates that the twisted tape with interrupted ribs provides a greater overall heat transfer performance over the twisted tape with no ribs in the square duct.

Prediction of Flow and Heat Transfer in Ducts of Square Cross-Section

1973 ◽  
Vol 187 (1) ◽  
pp. 455-461 ◽  
Author(s):  
B. E. Launder ◽  
W. M. Ying
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Cross Section ◽  
Close Agreement ◽  
Heat Transfer Characteristics ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Secondary Motion ◽  
Fully Developed Turbulent Flow

Numerical predictions are presented of the hydrodynamic and heat transfer characteristics of fully developed turbulent flow in square-sectioned ducts. The turbo stresses in the plane of the cross-section, whose gradients cause the well-known secondary motion, are approximated by gradients in the axial mean velocity. Predicted results are in close agreement with available experimental data of primary and secondary velocities as well as the shear stress and heat flux variations around the perimeter.

Experimental and Numerical Investigation of Flow and Heat Transfer in Stationary Two-Pass Rectangular Duct (AR = 1:2) with Continuous and Broken V- shaped ribs

2021 ◽  
pp. 1-37
Author(s):  
Ramesh Erelli ◽  
Arun Saha
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heated Surface ◽  
Reynolds Analogy ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Friction Factors ◽  
Local Temperature Distribution

Abstract The combined experimental and Large Eddy Simulations (LES) were performed in the stationary two-pass duct of aspect ratio (AR) 1:2. The experiments were conducted with three different rib arrangements, namely 60° V, 60° V-IV, and broken 60° V-IV ribs, and analysis was carried out with Reynolds numbers of 45,000, 60,000, and 75,000. The infrared thermography (IRT) technique is employed to obtain the local temperature distribution on heated smooth and ribbed surfaces. In all ribbed cases, the copper ribs are glued to the heated surface with a fixed rib height-to-hydraulic diameter (e / Dh) ratio is 0.125 and the rib pitch-to-height ratio (P / e) is 10 and 5 for continuous and broken ribs, respectively. In addition, LES turbulence model was adopted for carrying out simulation to understand the flow and heat transfer behavior in ducts populated with all three V-shaped ribs. The comparison of the time-averaged thermal fields generated using computations has been made with experimentally measured Nusselt numbers, friction factors, thermal performance factor (TPF), and Reynolds analogy performance parameter (RAPP) for all cases. The overall thermal performance factor was found to be quantitatively within 8.0 - 10.66% between experimental and numerical results. Among all the cases, the 60° V-IV ribbed duct provides the best TPF and RAPP than the other two ribbed ducts, whereas the smooth duct shows poor TPF.

scholarly journals Detailed CFD Modelling of Open Refrigerated Display Cabinets

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Pedro Dinis Gaspar ◽  
L. C. Carrilho Gonçalves ◽  
R. A. Pitarma
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Thermal Response ◽  
Experimental Tests ◽  
Cfd Modelling ◽  
Humidity Effect ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Parametric Studies ◽  
Flow Through

A comprehensive and detailed computational fluid dynamics (CFDs) modelling of air flow and heat transfer in an open refrigerated display cabinet (ORDC) is performed in this study. The physical-mathematical model considers the flow through the internal ducts, across fans and evaporator, and includes the thermal response of food products. The air humidity effect and thermal radiation heat transfer between surfaces are taken into account. Experimental tests were performed to characterize the phenomena near physical extremities and to validate the numerical predictions of air temperature, relative humidity, and velocity. Numerical and experimental results comparison reveals the predictive capabilities of the computational model for the optimized conception and development of this type of equipments. Numerical predictions are used to propose geometrical and functional parametric studies that improve thermal performance of the ORDC and consequently food safety.

Numerical and Analytical Study of Reversed Flow and Heat Transfer in a Heated Vertical Duct

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
C. S. Yang ◽  
D. Z. Jeng ◽  
K. A. Yih ◽  
C. Gau ◽  
Win Aung
Keyword(s):  
Heat Transfer ◽  
Penetration Depth ◽  
Analytical Models ◽  
Reversed Flow ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Spacing Ratio ◽  
Numerical Process ◽  
Vertical Duct

Both analytical and numerical calculations are performed to study the buoyancy effect on the reversed flow structure and heat transfer processes in a finite vertical duct with a height to spacing ratio of 12. One of the walls is heated uniformly and the opposite wall is adiabatic. Uniform air flow is assumed to enter the duct. In the ranges of the buoyancy parameter of interest here for both assisted and opposed convection, a reversed flow, which can be observed to initiate in the downstream close to the exit, propagates upstream as Gr/Re2 increases. The increase in the Reynolds number has the effect of pushing the reversed flow downstream. Simple analytical models are developed to predict the penetration depth of the reversed flow for both assisted and opposed convection. The models can accurately predict the penetration depth when the transport process inside the channel is dominated by natural convection. Local and average Nusselt numbers at different buoyancy parameters are presented. Comparison with the experimental data published previously was also made and discussed. Good agreement confirms many of the numerical predictions despite simplifications of the numerical process made, such as two-dimensional and laminar flow assumptions.

Analysis of the heat transfer and friction in a ribbed square channel using numerical and experimental methods

2007 ◽  
Vol 221 (3) ◽  
pp. 151-159 ◽  
Author(s):  
H. K. Kang ◽  
S. W. Ahn ◽  
S. T. Bae ◽  
D. H. Lee
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Uniform Heat Flux ◽  
Square Channel ◽  
Numerical Predictions ◽  
Transfer Channel ◽  
Flow Through

Numerical predictions and experiment of a hydrodynamic and thermally developed turbulent flow through square channels with one or two ribbed walls were performed to determine the pressure drop and heat transfer. The CFX (version 5.7) software package was used for the computations. The rough wall had 45°-inclined square ribs. All four walls in the channel were heated, and a uniform heat flux was maintained on the entire inner heat transfer channel area. Experimental data were also obtained for four Reynolds numbers ranging from 7600 to 24 900, a pitch-to-rib-height ratio of 8.0, and a rib-height-to-channel hydraulic diameter ratio of 0.0667. The numerical results were in agreement with the experimental data and showed that the values of the local heat transfer coefficient and friction factor in a square channel with two ribbed walls were greater than those with one ribbed wall.

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