Journal of Thermophysics and Heat Transfer 

About: Journal of Thermophysics and Heat Transfer is an academic journal published by American Institute of Aeronautics and Astronautics. The journal publishes majorly in the area(s): Heat transfer & Heat transfer coefficient. It has an ISSN identifier of 0887-8722. Over the lifetime, 3406 publications have been published receiving 64242 citations.

Thermal Conductivity of Nanoparticle -Fluid Mixture

Abstract: Effective thermal conductivity of mixtures of e uids and nanometer-size particles is measured by a steady-state parallel-plate method. The tested e uids contain two types of nanoparticles, Al 2O3 and CuO, dispersed in water, vacuum pump e uid, engine oil, and ethylene glycol. Experimental results show that the thermal conductivities of nanoparticle ‐e uid mixtures are higher than those of the base e uids. Using theoretical models of effective thermal conductivity of a mixture, we have demonstrated that the predicted thermal conductivities of nanoparticle ‐e uid mixtures are much lower than our measured data, indicating the dee ciency in the existing models when used for nanoparticle ‐e uid mixtures. Possible mechanisms contributing to enhancement of the thermal conductivity of the mixtures are discussed. A more comprehensive theory is needed to fully explain the behavior of nanoparticle ‐e uid mixtures. Nomenclature cp = specie c heat k = thermal conductivity L = thickness Pe = Peclet number P q = input power to heater 1 r = radius of particle S = cross-sectional area T = temperature U = velocity of particles relative to that of base e uids ® = ratio of thermal conductivity of particle to that of base liquid ¯ = .® i 1/=.® i 2/ ° = shear rate of e ow Ω = density A = volume fraction of particles in e uids Subscripts

Review of chemical-kinetic problems of future NASA missions, II: Mars entries

Abstract: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed, including the nonequilibrium thermochemical relaxation phenomena occurring behind a shock wave surrounding the flying object, problems related to aerobraking maneuver, the radiation phenomena for shock velocities of up to 12 km/sec, and the determination of rate coefficients for ionization reactions and associated electron-impact ionization reactions. Results of experiments are presented in form of graphs and tables, giving data on the reaction rate coefficients for air, the ionization distances, thermodynamic properties behind a shock wave, radiative heat flux calculations, Damkoehler numbers for the ablation-product layer, together with conclusions.

Assessment of two-temperature kinetic model for ionizing air

Abstract: A two-temperatur e chemical-kinet ic model for air is assessed by comparing theoretical results with existing experimental data obtained in shock tubes, ballistic ranges, and flight experiments. In the model, one temperature (T) is assumed to characterize the heavy-particle translational and molecular rotational energies, and another temperature (Tv) the molecular vibrational, electron translational, and electronic excitation energies. The theoretical results for nonequilibrium flow in shock tubes are obtained using the computer code STRAP (shock-tube radiation program) and for flow along the stagnation streamline in the shock layer over spherical bodies using the newly developed code SPRAP (stagnation-point radiation program). Substantial agreement is shown between the theoretical and experimental results for relaxation times and radiative heat fluxes. At very high temperatures, the spectral calculations need further improvement. The present agreement provides strong evidence that the two-temperature model characterizes principal features of nonequilibriu m airflow. New theoretical results using the model are presented for the radiative heat fluxes at the stagnation point of 6 m radius sphere, representing an aeroassisted orbital transfer vehicle, over a range of freestream conditions. Assumptions, approximations, and limitations of the model are discussed. Nomenclature = average molecular speed ^/$kT/nm, cm s ~ ! = pre-exponential factor in reaction rate coefficient, cm3mole~ 1 s~ * - average vibrational energy per particle, erg = average vibrational energy per particle under equilibrium, erg = reaction energy, erg

Finite volume method for radiation heat transfer

Abstract: This chapter presents a finite-volume (FV) method for computing radiation heat transfer processes The main ingredients of the calculation procedure were presented by Chai et al [1] The resulting method has been tested, refined and extended to account for various geometrical and physical complexities

Effective thermal conductivity of aqueous suspensions of carbon nanotubes (carbon nanotube nanofluids)

Abstract: This work is concerned with the effective thermal conductivity of aqueous suspensions of multiwalled carbon nanotubes (nanofluids). Stable nanofluids were made using sodium dodecylbenzene sulfonate as the dispersant. The effects of concentration of carbon nanotubes and temperature on effective thermal conductivity were investigated. It was found that effective thermal conductivity increased with increasing concentration of carbon nanotubes, and the dependence was nonlinear even at very low concentrations, which was different from the results for metal/metal oxide nanofluids. The effective thermal conductivity increased with increasing temperature, and the dependence was also nonlinear. At temperatures lower than ∼30 ◦ C, approximately linear dependence of the thermal conductivity enhancement on temperature was seen, but the dependence tended to level off above ∼30◦C. A comparison between the results of this work and those of published studies showed a large discrepancy in the effective thermal conductivity of carbon nanotube nanofluids. Differences in the interfacial resistances and thermal conductivities of carbon nanotubes used in these studies were proposed to be the main reasons. The experimental results were also compared with some classical macroscopic models for thermal conductivity of homogenous mixtures containing micrometer- or millimeter-sized particles. It was shown that the macroscopic models were inadequate for the prediction of the effective thermal conductivity of nanofluids. Analysis of possible mechanisms for thermal conduction enhancement suggested that networking of carbonnanotubes was likely to be responsible for the observed high effective thermal conductivity of carbon-nanotube nanofluids. Experiments at a temperature above 60‐70 ◦ C showed that the dispersant failed, which led to destabilization of nanofluids.