Correlation of Theoretical Analysis With Experimental Data on The Performance of Charring Ablators

1976 ◽  
Vol 98 (1) ◽  
pp. 139-143 ◽  
Author(s):  
K. Mastanaiah
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Theoretical Analysis ◽  
Experimental System ◽  
Wall Heat Flux ◽  
System Response ◽  
Exponential Dependence ◽  
Cold Wall ◽  
Static Test

Experimental data are obtained for surface recession, char depth, and temperatures in silica phenolic and carbon phenolic ablators from static test conducted on rocket nozzles. In an attempt to correlate the theoretical analysis with the experimental observations, it is found that the effective thermal conductivity of char is strongly dependent on the wall heat flux. An hypothesis is postulated that the char conductivity can best be correlated by cold wall heat flux treated as a generalized variable that includes the effects of other factors like temperature and chemical composition of the char. Exponential dependence of char conductivity on the cold wall heat flux is observed for both the ablators, and has offered excellent comparison between the theoretical and the experimental system response.

scholarly journals Simulation of a GOx-GCH4 Rocket Combustor and the Effect of the GEKO Turbulence Model Coefficients

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 341
Author(s):  
Evgeny Strokach ◽  
Victor Zhukov ◽  
Igor Borovik ◽  
Andrej Sternin ◽  
Oscar J. Haidn
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Turbulence Model ◽  
Chemical Kinetic ◽  
Wall Heat Flux ◽  
Combustion Model ◽  
Combustion Chambers ◽  
Separation Parameter ◽  
Kinetic Mechanisms ◽  
Stable Performance

In this study, a single injector methane-oxygen rocket combustor is numerically studied. The simulations included in this study are based on the hardware and experimental data from the Technical University of Munich. The focus is on the recently developed generalized k–ω turbulence model (GEKO) and the effect of its adjustable coefficients on the pressure and on wall heat flux profiles, which are compared with the experimental data. It was found that the coefficients of ‘jet’, ‘near-wall’, and ‘mixing’ have a major impact, whereas the opposite can be deduced about the ‘separation’ parameter Csep, which highly influences the pressure and wall heat flux distributions due to the changes in the eddy-viscosity field. The simulation results are compared with the standard k–ε model, displaying a qualitatively and quantitatively similar behavior to the GEKO model at a Csep equal to unity. The default GEKO model shows a stable performance for three oxidizer-to-fuel ratios, enhancing the reliability of its use. The simulations are conducted using two chemical kinetic mechanisms: Zhukov and Kong and the more detailed RAMEC. The influence of the combustion model is of the same order as the influence of the turbulence model. In general, the numerical results present a good or satisfactory agreement with the experiment, and both GEKO at Csep = 1 or the standard k–ε model can be recommended for usage in the CFD simulations of rocket combustion chambers, as well as the Zhukov–Kong mechanism in conjunction with the flamelet approach.

scholarly journals A Numerical Model to Estimate the Soil Thermal Conductivity Using Field Experimental Data

2019 ◽  
Vol 9 (22) ◽  
pp. 4799 ◽  
Author(s):  
Leugim Corteze Romio ◽  
Débora Regina Roberti ◽  
Lidiane Buligon ◽  
Tamires Zimmer ◽  
Gervásio Annes Degrazia
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Numerical Model ◽  
Soil Temperature ◽  
Field Experiments ◽  
Soil Heat Flux ◽  
Soil Thermal Conductivity ◽  
Empirical Parameter ◽  
Soil Temperature Gradient

Soil thermal conductivity is an important parameter for understanding soil heat transfer. It is difficult to measure in situ with available instruments. This work aims to propose a numerical model to estimate the thermal conductivity from the experimental measurements of soil heat flux and soil temperature. The new numerical model is based on the Fourier Law adding a constant empirical parameter to minimize the uncertainties contained in the data from field experiments. Numerically, the soil thermal conductivity is obtained by experimental linear data fitting by the Least Squares Method (LSM). This method avoids numerical indetermination when the soil temperature gradient or soil heat flux is very close to zero. The new model is tested against the different numerical methodology to estimate the soil heat flux and validated with field experimental data. The results indicate that the proposed model represents the experimental data satisfactorily. In addition, we show the influence of the different methodologies on evaluating the dependence of the thermal conductivity on the soil water content.

Analysis of Transient Laminar Forced Convection of Nanofluids in Circular Channels

2012 ◽  
Author(s):  
İsmail Ozan Sert ◽  
Nilay Sezer-Uzol ◽  
Sadik Kakac
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Steady State ◽  
Numerical Analysis ◽  
Forced Convection ◽  
Wall Temperature ◽  
Particle Diameter ◽  
Wall Heat Flux ◽  
Transient And Steady State

In this study, forced convection heat transfer characteristics of nanofluids are investigated by numerical analysis of incompressible transient laminar flow in a circular duct under step change in wall temperature and wall heat flux. The thermal responses of the system are obtained by solving energy equation under both transient and steady-state conditions for hydrodynamically fully developed flow. In the analyses, temperature dependent thermo-physical properties are also considered. In the numerical analysis, Al2O3/water nanofluid is assumed as a homogenous single-phase fluid. For the effective thermal conductivity of nanofluids, Hamilton-Crosser model is used together with a model for Brownian motion in the analysis which takes the effects of temperature and the particle diameter into account. Temperature distributions across the tube for a step jump of wall temperature and also wall heat flux are obtained for various times during the transient calculations at a given location for a constant value of Peclet number and a particle diameter. Variations of thermal conductivity in turn, heat transfer enhancement is obtained at various times as a function of nanoparticle volume fractions, at a given nanoparticle diameter and Peclet number. The results are given under transient and steady-state conditions; steady-state conditions are obtained at larger times and enhancements are found by comparison to the base fluid heat transfer coefficient under the same conditions.

Heat Transfer and Wall Heat Flux Partitioning During Subcooled Flow Nucleate Boiling—A Review

2006 ◽  
Vol 128 (12) ◽  
pp. 1243-1256 ◽  
Author(s):  
Gopinath R. Warrier ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Nucleate Boiling ◽  
Wall Heat Flux ◽  
Forced Flow ◽  
Mechanistic Models ◽  
Subcooled Flow ◽  
Flux Partitioning ◽  
Empirical And Mechanistic Models

In this paper we provide a review of heat transfer and wall heat flux partitioning models/correlations applicable to subcooled forced flow nucleate boiling. Details of both empirical and mechanistic models that have been proposed in the literature are provided. A comparison of the experimental data with predictions from selected models is also included.

scholarly journals Thermal conductivity difference between nanofluids and micro-fluids: Experimental data and theoretical analysis using mass difference scattering

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 3797-3807
Author(s):  
Fabrizio Iacobazzi ◽  
Gianpiero Colangelo ◽  
Marco Milanese ◽  
Risi de
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Theoretical Analysis ◽  
Metal Oxides ◽  
Mass Difference ◽  
Deionized Water ◽  
Experimental Results ◽  
Experimental Campaign ◽  
Nanometric Particles ◽  
Phonon Theory

In this work, an experimental campaign on different nanofluids and micro-fluids, obtained by the dispersion of three different metal oxides (CuO, ZnO, and TiO2) with diathermic oil or deionized water has been carried out, in order to extend phonon theory to liquids, as already done in a previous work on Al2O3. Thermal conductivity of stable samples was evaluated by time. The experimental results on thermal conductivity of stable micrometric and nanometric particles suspensions in oil and water showed a further proof of mass difference scattering phenomenon.

Wall Heat Flux Partitioning During Subcooled Flow Boiling: Part II—Model Validation

2005 ◽  
Vol 127 (2) ◽  
pp. 141-148 ◽  
Author(s):  
Nilanjana Basu ◽  
Gopinath R. Warrier ◽  
Vijay K. Dhir
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flow Boiling ◽  
Mechanistic Model ◽  
Wall Heat Flux ◽  
Experimental Conditions ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Flux Partitioning ◽  
Model Predictions

A mechanistic model for wall heat flux partitioning during subcooled flow boiling proposed in Part I of this two-part paper, is validated in this part. As the first step of the validation process, the developed model was applied to experimental data obtained as part of this study. Comparison of the model predictions with the present data shows good agreement. In order to further validate/exercise the model, it was then applied to several data sets available in the literature. Though the data in the literature were for experimental conditions vastly different from those from which the model was originally developed, reasonable agreement between the model predictions and the experimental data were observed. This indicates that the proposed model can be extended to other flow conditions provided the submodels cover the conditions of the experiments. Future work should be directed towards improvement of the various submodels involved to extend their range of applicability, especially the ones related to bubble dynamics. Additionally, it must be kept in mind that the model as proposed is strictly only applicable to vertical up-flow and may not be applicable to other orientations.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

Analysis of significant measures for thermal conductivity

2020 ◽  
pp. 35-42
Author(s):  
Yuri P. Zarichnyak ◽  
Vyacheslav P. Khodunkov
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Heat Flux Density ◽  
Measurement Method ◽  
Conductivity Measurement ◽  
Surface Heat ◽  
Measuring Instrument ◽  
New Class ◽  
Achievable Accuracy

The analysis of a new class of measuring instrument for heat quantities based on the use of multi-valued measures of heat conductivity of solids. For example, measuring thermal conductivity of solids shown the fallacy of the proposed approach and the illegality of the use of the principle of ambiguity to intensive thermal quantities. As a proof of the error of the approach, the relations for the thermal conductivities of the component elements of a heat pump that implements a multi-valued measure of thermal conductivity are given, and the limiting cases are considered. In two ways, it is established that the thermal conductivity of the specified measure does not depend on the value of the supplied heat flow. It is shown that the declared accuracy of the thermal conductivity measurement method does not correspond to the actual achievable accuracy values and the standard for the unit of surface heat flux density GET 172-2016. The estimation of the currently achievable accuracy of measuring the thermal conductivity of solids is given. The directions of further research and possible solutions to the problem are given.

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