Power pipe: An algorithm for analysis for single-phase, steady state, pipe networks with second-degree boundary conditions

2001 ◽  
Vol 215 (4) ◽  
pp. 519-525
Author(s):  
U Desideri ◽  
F Di Maria
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Conditions ◽  
Single Phase ◽  
Steam Condensation ◽  
Pipe Networks ◽  
Input And Output ◽  
Comparison With Experimental Data ◽  
Network Power ◽  
Second Degree

In this paper, an algorithm is described for the resolution of pipe networks with input and output conditions defined by pressure-flowrate correlations. The procedure and the main characteristics of the software are described. The method is particularly suited for solving pipe networks with boundary conditions defined by pressure-flowrate second-degree curves and during off-design operation. The code works with single-phase compressible and incompressible flow and a variety of fluids, including steam-gas mixtures. Heat transfer is also calculated for pipe elements and controls for steam condensation in steam or steam-gas networks are present. An application to a geothermal steam network power plant is included with comparison with experimental data.

Numerical Investigation of Heat Transfer Characteristics of Different Nanoparticles Using Modified Eulerian-Eulerian Model

2020 ◽  
Author(s):  
Muzafar Hussain ◽  
Shahbaz Tahir
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchangers ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Phase Model ◽  
Heat Transfer Characteristics ◽  
Eulerian Model ◽  
Transfer Characteristics

Abstract Nanofluids are widely adopted nowadays to enhance the heat transfer characteristics in the solar applications because of their excellent thermophysical properties. In this paper, a modified Eulerian-Eulerian model recently developed based on experiments was validated numerically to account for the deviations from the experimental data. The modified Eulerian-Eulerian model is compared with the single-phase model, Eulerian-Eulerian models for TiO2-water at different operating conditions and deviation from the experimental data for each of the model was documented. However, the modified Eulerian-Eulerian model gave much closer results when compared to the experimental data. For the further extension of work, the modified Eulerian-Eulerian model was applied to different nanofluids in order to investigate their heat transfer characteristics. Three different nanoparticles were investigated namely Cu, MgO, and Ag and their heat transfer characteristics is calculated based on the modified Eulerian-Eulerian model as well as the single-phase model for the comparison. For lower values of Reynolds numbers, the average heat transfer coefficient was almost identical for both models with small percentage of error but for higher Reynolds numbers, the deviation got larger. Therefore, single-phase model is not appropriate for higher Reynolds numbers and modified Eulerian-Eulerian model should be used to accurately predict the heat transfer characteristics of the nanofluids at higher Reynolds numbers. From the analysis it is found that the Ag-water nanofluid have the highest heat transfer characteristics among others and can be employed in the solar heat exchangers to enhance the heat transfer characteristics and to further improve the efficiency.

Analysis of Swirl Flow by Tube Inserts for CFD Study

2015 ◽  
Author(s):  
Salem Bouhairie
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Single Phase ◽  
Tube Bundle ◽  
Reynolds Numbers ◽  
Swirl Flow ◽  
Twisted Tape ◽  
Cfd Simulations ◽  
Flow Length ◽  
Mechanical Methods

The petroleum and petrochemical industries continually seek mechanical methods to improve heat transfer in shell-and-tube heat exchangers. Tube bundle inserts are popular mechanical devices that help improve performance. The increase in the tubeside heat transfer coefficient by the insert allows for a decrease in required shellside flow length, assuming single tube pass. The flow length reduction allows for designing higher velocities and subsequent shellside shear rates, to help reduce crude oil fouling potential. This work presents some of HTRI’s ongoing experimental measurements and preliminary Computational Fluid Dynamics (CFD) simulations. CFD visualization of swirl flow dynamics and heat transfer inside the augmented tube provides insight on complex flow physics, which is misunderstood. Heat Transfer Research, Inc. (HTRI) collected experimental data for in-tube single-phase flow using twisted tape inserts in the Tubeside Single-Phase Unit (TSPU) situated in the Research and Technology Center (RTC). Our data will be used to calibrate ANSYS FLUENT CFD simulations of a tube with a twisted tape swirl insert. We first performed plain tube simulations and compared the heat transfer results with open literature measurements, for validation. We will modify the CFD tube model to have a swirl flow insert, and compare numerical results against open literature experimental data of diabatic single-phase swirl flow. In future, we will compute heat transfer (heating and cooling) and pressure drop for tube insert configurations at laminar and turbulent Reynolds numbers from 3000 to 500000. The range of tubeside Reynolds numbers required the use of the laminar, transition, and Realizable k-epsilon turbulence models with scalable wall functions. This study describes some of the mechanisms behind turbulent swirl flow augmentation inside a tube, as well as the limitations of conventional in-tube heat transfer correlations applied to swirl flow inserts.

CFD and Thermal Analysis of Leaf Seals for Aero-Engine Application

2016 ◽  
Author(s):  
Vincenzo Fico ◽  
Michael J. Pekris ◽  
Christopher J. Barnes ◽  
Rakesh Kumar Jha ◽  
David Gillespie
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Analysis ◽  
Reynolds Number ◽  
Boundary Conditions ◽  
Frictional Heat ◽  
Analysis And Design ◽  
Thermal Boundary Conditions ◽  
Leaf Pack ◽  
Aero Engine

Aero-engine gas turbine performance and efficiency can be improved through the application of compliant shaft seal types to certain sealing locations within the secondary air system. Leaf seals offer better performance than traditional labyrinth seals, giving lower leakage flows at design duties. However, for aeroengine applications, seal designs must be able to cope with relatively large off-design seal closures and closure uncertainties. The two-way coupling between temperatures of seal components and seal closures, through the frictional heat generated at the leaf-rotor interface when in contact, represents an important challenge for leaf seal analysis and design. This coupling can lead to leaf wear and loss, rotor overheating, and possibly to unstable sealing system behaviour (thermal runaway). In this paper we use CFD, FE thermal analysis, and experimental data to characterise the thermal behaviour of leaf seals. This sets the basis for a study of the coupled thermo-mechanical behaviour. CFD is used to understand the fluid-mechanics of a leaf pack. The leaf seal tested at the Oxford Osney Laboratory is used for the study. Simulations for four seal axial Reynolds number are conducted; for each value of the Reynolds number, leaf tip-rotor contact and clearance are considered. Distribution of mass flow within the leaf pack, distribution of heat transfer coefficient at the leaf surface, and swirl velocity pick-up across the pack predicted using CFD are discussed. The experimental data obtained from the Oxford rig is used to develop a set of thermal boundary conditions for the leaf pack. An FE thermal model of the rig is devised, informed by the aforementioned CFD study. Four experiments are simulated; thermal boundary conditions are calibrated to match predicted metal temperatures to those measured on the rig. A sensitivity analysis of the rotor temperature predictions to the heat transfer assumptions is carried out. The calibrated set of thermal boundary conditions is shown to accurately predict the measured rotor temperatures.

Comparison of Single and Two-Phase Models for the Study of Mixed Convection Flows With Nanofluids

2010 ◽  
Author(s):  
Mahmood Akbari ◽  
Amin Behzadmehr ◽  
Nicolas Galanis
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mixed Convection ◽  
Single Phase ◽  
Volume Fraction ◽  
Solid Particles ◽  
Two Phase ◽  
Prediction Ability ◽  
Numerical Predictions ◽  
Phase Models

The single phase and three different two phase models (Volume of fluid, Mixture and Eulerian) are used to analyse laminar mixed convection flow of Al2O3-water nanofluids in a horizontal tube, in order to evaluate their prediction ability. The flow is considered steady and developing. The fluid’s physical properties are temperature dependent whereas those of the solid particles are constant. A uniform heat flux is applied at the fluid-solid interface. Two different Reynolds numbers and three different volume fractions have been considered. The governing three-dimensional partial differential equations are elliptical in all directions and coupled. Predicted convective heat transfer coefficients, velocity, and temperature profiles, as well as secondary flow’s velocity vectors and temperature contours are compared at different axial positions. To validate the comparisons and verify the accuracy of the results, the numerical predictions are compared with corresponding experimental data. There are essentially no differences between the predictions of the two-phase models; however their results are significantly different from those of the single-phase approach. Two-phase model results are closer to the experimental data, but they show an unrealistic increase in heat transfer for small changes of the particle volume fraction. Hydrodynamically, the two-phase and single-phase approaches perform almost the same but their thermal predictions are quite different.

scholarly journals New Perspective for Heat Transfer Evaluation During Film Condensation Inside Tubes

2021 ◽  
Vol 39 (2) ◽  
pp. 390-402
Author(s):  
Yanán Camaraza-Medina
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Single Phase ◽  
Film Condensation ◽  
Mean Deviation ◽  
Two Phase ◽  
Wide Range ◽  
The Mean ◽  
Vertical Tubes

This paper presents the main results of the research developed by the author in his postdoctoral investigations on heat transfer calculations during film condensation inside tubes. The elements studied are combined in an analysis expression that provides a reasonable fit with the available experimental data, which includes a total of 22 fluids, including water, refrigerants and a wide range of organic substances, which condense inside horizontal, inclined and vertical tubes. These experimental data were obtained from the reports of 33 sources. Available data covers tube diameters from 2 to 50 mm, mass flow rates from 3 to 850 kg/(m2s), reduced pressures ranging from 0.0008 to 0.91, values for single-phase from 1 to , Reynolds number for two-phase from 900 to 594390, Reynolds number for single-phase from 65 to 84950 and vapor quality from 0.01 to 0.99. The mean deviation found for the analyzed data for horizontal tubes was 13.4%, while for the inclined and vertical tubes data the mean deviation was 14.9%. In all cases, the agreement of the proposed model is good enough to be considered satisfactory for practical design.

Water Single-Phase Fluid Flow and Heat Transfer in Capillary Tubes

2003 ◽  
Author(s):  
A. Bucci ◽  
G. P. Celata ◽  
M. Cumo ◽  
E. Serra ◽  
G. Zummo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Heat Transfer Correlations ◽  
Good Agreement

This paper reports the results of an experimental investigation of fluid flow and single-phase heat transfer of water in stainless steel capillary tubes. Three tube diameters are tested: 172 μm, 290 μm and 520 μm, while the Reynolds number varying from 200 up to 6000. Fluid flow experimental results indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 800–1000. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–3000. This transition is found in good agreement with the well known flow transition for rough commercial tubes. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional size tubes, are not adequate for calculation of heat transfer coefficient in microtubes. In laminar flow the experimental values of heat transfer coefficient are generally higher than those calculated with the classical correlation, while in turbulent flow regime experimental data do not deviate significantly from classical heat transfer correlations. Deviation from classical heat transfer correlations increase as the channel diameter decrease.

Computational Fluid Dynamics and Thermal Analysis of Leaf Seals for Aero-engine Application

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Vincenzo Fico ◽  
Michael J. Pekris ◽  
Christopher J. Barnes ◽  
Rakesh Kumar Jha ◽  
David Gillespie
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Thermal Analysis ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Boundary Conditions ◽  
Thermal Boundary Conditions ◽  
Leaf Pack ◽  
Aero Engine

Aero-engine gas turbine performance and efficiency can be improved through the application of compliant shaft seal types to certain sealing locations within the secondary air system. Leaf seals offer better performance than traditional labyrinth seals, giving lower leakage flows at design duties. However, for aero-engine applications, seal designs must be able to cope with relatively large off-design seal closures and closure uncertainties. The two-way coupling between temperatures of seal components and seal closures, through the frictional heat generated at the leaf–rotor interface when in contact, represents an important challenge for leaf seal analysis and design. This coupling can lead to leaf wear and loss, rotor overheating, and possibly to unstable sealing system behavior (thermal runaway). In this paper, we use computational fluid dynamics (CFD), finite element (FE) thermal analysis, and experimental data to characterize the thermal behavior of leaf seals. This sets the basis for a study of the coupled thermomechanical behavior. CFD is used to understand the fluid-mechanics of a leaf pack. The leaf seal tested at the Oxford Osney Laboratory is used for the study. Simulations for four seal axial Reynolds number are conducted; for each value of the Reynolds number, leaf tip-rotor contact, and clearance are considered. Distribution of mass flow within the leaf pack, distribution of heat transfer coefficient (HTC) at the leaf surface, and swirl velocity pick-up across the pack predicted using CFD are discussed. The experimental data obtained from the Oxford rig is used to develop a set of thermal boundary conditions for the leaf pack. An FE thermal model of the rig is devised, informed by the aforementioned CFD study. Four experiments are simulated; thermal boundary conditions are calibrated to match the predicted metal temperatures to those measured on the rig. A sensitivity analysis of the rotor temperature predictions to the heat transfer assumptions is carried out. The calibrated set of thermal boundary conditions is shown to accurately predict the measured rotor temperatures.

Single-Phase Liquid Heat Transfer in Microchannels

2005 ◽  
Author(s):  
Mark E. Steinke ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Classical Theory ◽  
Single Phase ◽  
Fin Efficiency ◽  
Transfer Processes ◽  
Reporting Discrepancies ◽  
Phase Liquid ◽  
Liquid Heat ◽  
Flow Devices

The development of advanced microchannel heat exchangers and microfluidic devices is dependent upon the understanding of the fundamental heat transfer processes that occur in these systems. Several researchers have reported significant deviation from the classical theory used in macroscale applications, while others have reported general agreement, especially in the laminar region. This fundamental question needs to be addressed in order to generate a set of design equations to predict the heat transfer performance of microchannel flow devices. A database is generated from the available literature to critically evaluate the reported experimental data. An in-depth comparison of previous experimental data is performed to identify the discrepancies in the reported literature. It is concluded that the classical theory is applicable to microchannel and minichannel flows. The literature reporting discrepancies do not account for developing flows, fin efficiency, erros in channel geometry measurements and experimental uncertainties. It is further concluded that if all these factors are accounted for, the available data have good general agreement with macroscale theories. A similar approach is presented for pressure drop in microchannels in an accompanying conference paper, Steinke and Kandlikar (2005).

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