Convective Heat Transfer to Turbulent Droplet Flow in Circular Tubes

1981 ◽  
Vol 103 (4) ◽  
pp. 679-684 ◽  
Author(s):  
A. G. Rane ◽  
Shi-Chune Yao
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Single Phase ◽  
Size Variation ◽  
Number Density ◽  
Droplet Flow ◽  
Dimensionless Groups ◽  
Flow Heat ◽  
Thermal Entrance ◽  
Good Agreement

Turbulent droplet flow heat transfer is analyzed for the thermal entrance region of a circular tube. Calculations are performed considering droplet size variation, vapor acceleration and dilution of droplet number density until the single-phase fully developed conditions is reached. Effect of the relevant dimensionless groups on the heat transfer results is studied. The analytical results are compared with the available experimental data. These comparisons show good agreement between the experimental data and the predictions.

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.

Single-Phase Heat Transfer and Fluid Flow in Micropipes

2003 ◽  
Author(s):  
Gian Piero Celata
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Transfer Rate ◽  
Single Phase ◽  
Flow Transition ◽  
Laminar And Turbulent Regimes ◽  
Good Agreement

The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 600–800. 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 flow occurs for Reynolds number in the range 1800–2500. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional (macro) tubes, are not properly adequate for heat transfer rate prediction in microtubes.

Convective Heat Transfer of Laminar Droplet Flow in Thermal Entrance Region of Circular Tubes

1979 ◽  
Vol 101 (3) ◽  
pp. 480-483 ◽  
Author(s):  
Shi-chune Yao
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Entrance Region ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Droplet Flow ◽  
Thermal Entrance Region ◽  
Thermal Entrance

Connective heat transfer of laminar droplet flow is calculated numerically for the thermal entrance region of circular tube with constant wall temperature. The heat transfer contribution of saturated droplets in the superheated vapor stream is considered as distributed heat sink. In the thermal entrance region, the size and the population density of the droplets are considered as constants. The heat transfer of droplet flow is found to be considerably higher than that of single phase flow. The effects of the droplet characteristics and the wall superheat to the convective heat transfer are studied. Fundamental differences of heat transfers in single phase flow and droplet flow are revealed.

Post-Test Investigations of BFBT Critical Power Tests With Trace

2009 ◽  
Author(s):  
Marc Thieme ◽  
Wolfgang Tietsch ◽  
Rafael Macian ◽  
Victor Hugo Sanchez Espinoza
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Critical Power ◽  
The Core ◽  
Fine Mesh ◽  
The Us ◽  
Post Test ◽  
Trace Model ◽  
Good Agreement ◽  
Transfer Models

The validation of heat transfer models of safety analysis codes such as TRACE is very important due to the strong interaction of the thermal hydraulics parameters with the core neutronics. TRACE is the reference system code of the US NRC for LWR. It is being developed and extensively validated within the international CAMP-program. In this paper, the validation of heat transfer models of TRACE related to the prediction of the critical power is presented. The validation is based on a large number of critical power tests performed in the NUPEC BFBT (BWR Full-Size Fine-Mesh Bundle Tests) facility in Japan. These tests were analysed with the TRACE Version 5 RC 2. The comparison of predictions with the experimental data shows good agreement. The developed TRACE model and the comparison of experimental data with code results will be presented and discussed.

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.

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.

Coupled CFD-ANN Procedure for Extending Heat Transfer Correlations Out of Their Range of Validity

2012 ◽  
Author(s):  
Andrea Viano ◽  
Gabriele Ottino ◽  
Luca Ratto ◽  
Giuseppe Spataro
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Training Session ◽  
Nonlinear Problems ◽  
Artificial Neural ◽  
Cfd Analyses ◽  
Good Agreement

The heat transfer coefficient and pressure losses are among the main parameters to be evaluated in gas turbine cooling network design. Due to the complexity of these estimates, correlation-based computations are typically used as a result of time-consuming and expensive experimental activities. One of the main problems that the industry has to face is that these correlations, based on non-dimensional experimental data, produce reliable results in a range of validity typically different from that encountered in gas turbine applications. This paper will present preliminary results of an innovative procedure based on CFD analyses and Artificial Neural Networks, able to extend correlation predictions out of their range of validity, without any additional experimental data. Well-known test cases were replicated by building corresponding CAD geometries which were discretized by means of appropriate meshes, resulting from grid-independence studies. CFD analyses, based on the RANS approach, were performed to overlay the computations of the Nusselt number obtained from experimental activities. A preliminary comparison among turbulence models was carried out to find one leading to a good agreement with the experimental data. Then, an optimization method, based on Evolutionary Algorithms, was applied to the CFD analyses in order to find the best set of constant values for the chosen turbulence model, leading to the most accurate prediction of the experimental dataset. The resulting ad hoc CFD model was adopted in order to analyse test case configurations characterized by parameters within and external to the correlation validity field, building a sufficiently wide feeding database. A feed-forward multi-layer neural network was selected among network architectures typically used in engineering applications for prediction analyses. ANNs were chosen because they enable the solution of these complex nonlinear problems by using simple computational operations. The selected Artificial Neural Network was trained by a back-propagation procedure on the CFD results regarding Nusselt number. The validation of the resulting ANN was performed comparing its outputs with experimental data external to the correlation range of validity, which had not been used in the training session. Good agreement has been found. Results are presented and discussed.

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