Analysis of the Aerodynamic Heating for a Re-Entrant Space Vehicle

1959 ◽  
Vol 81 (3) ◽  
pp. 223-229 ◽  
Author(s):  
M. J. Brunner
Keyword(s):  
Pressure Distribution ◽  
Wall Temperature ◽  
Space Vehicle ◽  
Heat Fluxes ◽  
Aerodynamic Heating ◽  
Heating Rates ◽  
Local Pressure ◽  
High Lift ◽  
Maximum Heating ◽  
Vehicle Bodies

An analysis of the aerodynamic heating is presented through the trajectory and over the surface of a re-entrant hypersonic space vehicle. Bodies exhibiting zero and high lift over drag ratios are considered. The turbulent and laminar convective heat inputs are specified as functions of the trajectory and space vehicle parameters. The maximum heating rates and time integrated heat fluxes are given as functions of the local pressure distribution, body geometry, and wall temperature. Examples are presented to illustrate the application of this analysis.

scholarly journals Thermochemical characterization of polybenzimidazole with and without nano-ZrO2 for ablative materials application

2020 ◽  
Vol 142 (5) ◽  
pp. 2149-2161
Author(s):  
L. Paglia ◽  
V. Genova ◽  
M. P. Bracciale ◽  
C. Bartuli ◽  
F. Marra ◽  
...  
Keyword(s):  
High Performance ◽  
Phenolic Resin ◽  
Thermal Protection ◽  
Space Vehicle ◽  
Heat Fluxes ◽  
Heating Rates ◽  
Thermoplastic Material ◽  
Environmental Friendly ◽  
Very High

AbstractDuring the ballistic atmospheric re-entry, a space vehicle has to withstand huge thermo-mechanical solicitations because of its high velocity and the friction with the atmosphere. According to the kind of the re-entry mission, the heat fluxes can be very high (in the order of some MW m−2) ;thus, an adequate thermal protection system is mandatory in order to preserve the structure of the vehicle, the payload and, for manned mission, the crew. Carbon phenolic ablators have been chosen for several missions because they are able to dissipate the incident heat flux very efficiently. Phenolic resin presents satisfying performance but also environmental drawbacks. Thus, a more environmental-friendly solution was conceived: a high-performance thermoplastic material, polybenzimidazole (PBI), was employed instead of phenolic resin. In this work PBI-ablative material samples were manufactured with and without the addition of nano-ZrO2 and tested with an oxyacetylene flame. For comparison, some carbon-phenolic ablators with the same density were manufactured and tested too. Thermogravimetric analysis on PBI samples was carried out at different heating rates, and the obtained TG data were elaborated to evaluate the activation energy of PBI and nano-filled PBI. The thermokinetics results for PBI show an improvement in thermal stability due to the addition of nano-ZrO2, while the oxyacetylene flame test enlightens how PBI ablators are able to overcome the carbon phenolic ablators performance, in particular when modified by the addition of nano-ZrO2.

Maximum heating rates for producing undistorted glassy carbon ware determined by wedge-shaped samples

1996 ◽  
Vol 11 (9) ◽  
pp. 2368-2375 ◽  
Author(s):  
Hossein Maleki ◽  
Lawrence R. Holland ◽  
Gwyn M. Jenkins ◽  
R. L. Zimmerman ◽  
Wally Porter
Keyword(s):  
Heating Rate ◽  
Treatment Process ◽  
Gaseous Product ◽  
Pyrolysis Mass Spectrometry ◽  
Heating Rates ◽  
Gaseous Products ◽  
Volatile Products ◽  
Solid Bodies ◽  
Polymeric Carbon ◽  
Maximum Heating

Polymeric carbon artifacts are particularly difficult to make in thick section. Heating rate, temperature, and sample thickness determine the outcome of carbonization of resin leading to a glassy polymeric carbon ware. Using wedge-shaped samples, we found the maximum thickness for various heating rates during gelling (300 K–360 K), curing (360 K–400 K), postcuring (400 K–500 K), and precarbonization (500 K–875 K). Excessive heating rate causes failure. In postcuring the critical heating rate varies inversely as the fifth power of thickness; in precarbonization this varies inversely as the third power of thickness. From thermogravimetric evidence we attribute such failure to low rates of diffusion of gaseous products of reactions occurring within the solid during pyrolysis. Mass spectrometry shows the main gaseous product is water vapor; some carboniferous gases are also evolved during precarbonization. We discuss a diffusion model applicable to any heat-treatment process in which volatile products are removed from solid bodies.

Comparison of Existing Supercritical Carbon Dioxide Heat Transfer Correlations for Horizontal and Vertical Bare Tubes

2012 ◽  
Author(s):  
Prabu Surendran ◽  
Sahil Gupta ◽  
Tiberiu Preda ◽  
Igor Pioro
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Wall Temperature ◽  
Statistical Error ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bulk Fluid ◽  
Heat Transfer Correlations ◽  
Supercritical Carbon

This paper presents a thorough analysis of ability of various heat transfer correlations to predict wall temperatures and Heat Transfer Coefficients (HTCs) against experiments on internal forced-convective heat transfer to supercritical carbon dioxide conducted by Koppel [1], He [2], Kim [3] and Bae [4]. It should be noted the Koppel dataset was taken from a paper which used the Koppel data but was not written by Koppel. All experiments were completed in bare tubes with diameters from 0.948 mm to 9 mm for horizontal and vertical configurations. The datasets contain a total of 1573 wall temperature points with pressures ranging from 7.58 to 9.59 MPa, mass fluxes of 400 to 1641 kg/m2s and heat fluxes from 20 to 225 kW/m2. The main objective of the study was to compare several correlations and select the best of them in predicting HTC and wall temperature values for supercritical carbon dioxide. This study will be beneficial for analyzing heat exchangers involving supercritical carbon dioxide, and for verifying scaling parameters between CO2 and other fluids. In addition, supercritical carbon dioxide’s use as a modeling fluid is necessary as the costs of experiments are lower than supercritical water. The datasets were compiled and calculations were performed to find HTCs and wall and bulk-fluid temperatures using existing correlations. Calculated results were compared with the experimental ones. The correlations used were Mokry et al. [5], Swenson et al. [6] and a set of new correlations presented in Gutpa et al. [7]. Statistical error calculations were performed are presented in the paper.

Design and Characterization of a Novel Upward Flow Reactor for the Study of High-Temperature Thermal Reduction for Solar-Driven Processes

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
H. Evan Bush ◽  
Karl-Philipp Schlichting ◽  
Robert J. Gill ◽  
Sheldon M. Jeter ◽  
Peter G. Loutzenhiser
Keyword(s):  
High Temperature ◽  
Flow Reactor ◽  
Thermal Reduction ◽  
Heat Fluxes ◽  
O2 Evolution ◽  
Transfer Model ◽  
Upward Flow ◽  
Heating Rates ◽  
Solar Simulator

The design and characterization of an upward flow reactor (UFR) coupled to a high flux solar simulator (HFSS) under vacuum is presented. The UFR was designed to rapidly heat solid samples with concentrated irradiation to temperatures greater than 1000 °C at heating rates in excess of 50 K/s. Such conditions are ideal for examining high-temperature thermal reduction kinetics of reduction/oxidation-active materials by temporally monitoring O2 evolution. A steady-state, computational fluid dynamics (CFD) model was employed in the design to minimize the formation of eddies and recirculation, and lag and dispersion were characterized through a suite of O2 tracer experiments using deconvolution and the continuously stirred tank reactors (CSTR) in series models. A transient, CFD and heat transfer model of the UFR was combined with Monte Carlo ray tracing (MCRT) to determine radiative heat fluxes on the sample from the HFSS to model spatial and temporal sample temperatures. The modeled temperatures were compared with those measured within the sample during an experiment in which Co3O4 was thermally reduced to CoO and O2. The measured temperatures within the bed were bounded by the average top and bottom modeled bed temperatures for the duration of the experiment. Small variances in the shape of the modeled versus experimental temperatures were due to contact resistance between the thermocouple and particles in the bed and changes in the spectral absorptivity and emissivity as the Co3O4 was reduced to CoO and O2.

Convection Heat Transfer of CO2 at Supercritical Pressures in a Vertical Mini Tube

2009 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
High Heat ◽  
Vertical Tube ◽  
Density Variation ◽  
Heat Fluxes ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration

This paper presents the experimental and numerical investigation results of the convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at various inlet Reynolds numbers, heat fluxes and flow directions. The effects of buoyancy and flow acceleration resulted from the dramatic properties variation were investigated. Results showed that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference of the local wall temperature between upward flow and downward flow was very small when other test conditions were held the same, which indicates that for supercritical CO2 flowing in a mini tube as employed in this study, the buoyancy effect on the convection heat transfer was quite insignificant, and the flow acceleration induced by the axial density variation with temperature was the main factor that lead to the abnormal local wall temperature distribution at high heat fluxes. The predicted values using the LB low Reynolds number turbulence model correspond well with the measured data. Velocity profiles and turbulence kinetic energy near the wall varying along the tube generated by the numerical simulations were presented to develop a better understanding.

Experimental Study of Heat Transfer to Supercritical Pressure Water Flowing in a 2×2 Rod Bundle

2014 ◽  
Author(s):  
Han Wang ◽  
Qincheng Bi ◽  
Linchuan Wang ◽  
Haicai Lv ◽  
Laurence K. H. Leung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Pressure Drop ◽  
Wall Temperature ◽  
Mass Flux ◽  
Heat Fluxes ◽  
Outer Diameter ◽  
Square Channel ◽  
Rod Bundle

An experiment has recently been performed at Xi’an Jiaotong University to study the wall temperature and pressure drop at supercritical pressures with upward flow of water inside a 2×2 rod bundle. A fuel-assembly simulator with four heated rods was installed inside a square channel with rounded corner. The outer diameter of each heated rod is 8 mm with an effective heated length of 600 mm. Experimental parameters covered the pressure of 23–28 MPa, mass flux of 350–1000 kg/m2s and heat flux on the rod surface of 200–1000 kW/m2. According to the experimental data, it was found that the circumferential wall temperature distribution of a heated rod is not uniform. The temperature difference between the maximum and the minimum varies with heat flux and/or mass flux. Heat transfer characteristics of supercritical water in bundle were discussed with respect to various heat fluxes. The effect of heat flux on heat transfer in rod bundles is similar with that in tubes or annuli. In addition, flow resistance reflected in the form of pressure loss has also been studied. Experimental results showed that the total pressure drop increases with bulk enthalpy and mass flux. Four heat transfer correlations developed for supercritical pressures water were compared with the present test data. Predictions of Jackson correlation agrees closely with the experimental data.

CAE Correlation of Sealing Pressure of a Press-in-Place Gasket

2021 ◽  
Keyword(s):  
Internal Pressure ◽  
Pressure Distribution ◽  
Load Condition ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Test Results ◽  
Local Pressure ◽  
Cross Sectional ◽  
Pad Test ◽  
Sealing Pressure

The Press-in-Place (PIP) gasket is a static face seal with self-retaining feature, which is used for the mating surfaces of engine components to maintain the reliability of the closed system under various operating conditions. Its design allows it to provide enough contact pressure to seal the internal fluid as well as prevent mechanical failures. Insufficient sealing pressure will lead to fluid leakage, consequently resulting in engine failures. A test fixture was designed to simulate the clamp load and internal pressure condition on a gasket bolted joint. A Sensor pad using TEKSCAN equipment was used to capture the overall and local pressure distribution of the PIP gasket under various engine loading conditions. Then, the Sensor pad test results were compared with simulated CAE results from computer models. Through the comparisons, it is found that the gasket sealing pressure of test data and CAE data show good correlation for bolt load condition 500N when compared to internal pressure side load condition of 0.138 MPa & 0.276 MPa. Moreover, the gasket cross-sectional pressure distribution obtained by experimental tests and CAE models correlated very well with R2 ranging from 90 to 99% for all load cases. Both CAE and Sensor pad test results shows increase in sealing pressure when internal side pressure is applied to the gasket seal.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

Impact of Bifurcation Angle and Inlet Reynolds Number on Local Pressure Recovery in Biologically-Inspired Flow Networks

2017 ◽  
Author(s):  
Subhadeep Koner ◽  
David Calamas ◽  
Daniel Dannelley
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Wall Temperature ◽  
Flow Behavior ◽  
Flow Networks ◽  
Local Pressure ◽  
Biologically Inspired ◽  
Local Flow ◽  
Bifurcation Angle ◽  
Microscale Flow

This work computationally investigates local flow behavior in tree-like flow networks of varying scale, bifurcation angle, and inlet Reynolds number. The performance of the tree-like flow networks were evaluated based on pressure drop and wall temperature distributions. Microscale, mesoscale, and macroscale tree-like flow networks, composed of a range of symmetric bifurcation angles (15, 30, 45, 60, 75, and 90°) and subject to a range of inlet Reynolds numbers (1000, 2000, 4000, 10000, and 20000) were evaluated. Local pressure recoveries were evident at bifurcations, regardless of scale and bifurcation angle which may result in a lower total pressure drop when compared with traditional parallel channel networks. Similarly, wall temperature spikes were also present immediately following bifurcations due to flow separation and recirculation. The magnitude of the wall temperature increases at bifurcations was dependent upon both bifurcation angle and scale. When compared with mesoscale and macroscale flow networks, microscale flow networks resulted in the largest local pressure recoveries and the smallest temperature jumps at bifurcations. Thus, while biologically-inspired flow networks offer the same advantages at all scales, the greatest performance increases are achieved at microscale.

Application of a Synthetic Jet to Control Boundary Layer Separation under Ultra-High-Lift Turbine Pressure Distribution

2011 ◽  
Vol 87 (4) ◽  
pp. 597-616 ◽  
Author(s):  
Davide Lengani ◽  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Francesco Bertini
Keyword(s):  
Boundary Layer ◽  
Pressure Distribution ◽  
Boundary Layer Separation ◽  
Synthetic Jet ◽  
High Lift ◽  
Layer Separation
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