A molecular dynamics simulation of the effect of the toluene catalytic ratios and initial temperature on the catalytic combustion of air/methane inside a microchannel.

METHODS: This research studied the effect of initial temperature (300-400K), and atomic percentage of toluene catalyst (1-10%) on the atomic and thermal performance of air/methane catalytic combustion. The present study was performed using molecular dynamics (MD) simulation. CONTEXT: The results demonstrate that by increasing the initial temperature from 300 to 400 K, the maximum velocity and temperature increased from 0.52 Å/ps and 585 K to 0.72 Å/ ps and 629 K, respectively. Moreover, the heat flux, thermal conductivity, and combustion efficiency increased from 2020 W/m2, 1.45 W/mK, and 93% to 2208 W/m2, 1.55 W/mK, and 97% by increasing initial temperature to 400 K. On the other hand, by increasing the atomic percentage of toluene catalyst from 1% to 4%, the maximum velocity and temperature increased from 0.41Å/ps and 546 K to 0.49 Å/ ps and 573 K, respectively. Thermal conductivity and combustion efficiency increased from 1.451.22 W/mK and 77% to 1.33 W/mK and 89%. With further increasing of the catalyst to 10%, the thermal performance of sample declined. This decrease could be attributed to the agglomeration process, where an excessive amount of catalyst may lead to agglomeration, negatively affecting the structure's catalytic activity and overall thermal performance.

Molecular dynamics study of the thermal behavior of ammonia refrigerant in the presence of copper nanoparticles at different volume ratios and initial temperatures.

Generally, the addition of nanoparticles to a fluid significantly increases the thermal conductivity of structures. In the present study, the effect of nanoparticle volume ratio and initial temperature on ammonia/copper nano-refrigerant's thermal behavior in an external electric field in an aluminum nanochannel was studied by molecular dynamics simulations. To study the thermal behavior of the structures, quantities such as particle phase-changed rates (condensation process), phase change duration, and thermal conductivity were investigated. Results show that with the addition of 5% copper to the base fluid, the rate of the phase-changed particles increases from 53 to 71% during 2.40 ns. Also, increasing the volume ratio of nanoparticles up to 5% leads to an increase in thermal conductivity from 0.76 to 0.86 W/mK. On the other hand, increasing the initial temperature up to 350 K reduces the phase-changed particles' rate from 53 to 49% during 2.9 ns. The initial temperature increases from 300 to 350 K, and the thermal conductivity decreases from 0.76 to 0.73 W/mK. The results of this simulation are expected to improve the thermal performance of different nano-refrigerants.

An efficient reliable method to estimate the vaporization enthalpy of pure substances according to the normal boiling temperature and critical properties.

The heat of vaporization of a pure substance at its normal boiling temperature is a very important property in many chemical processes. In this work, a new empirical method was developed to predict vaporization enthalpy of pure substances. This equation is a function of normal boiling temperature, critical temperature, and critical pressure. The presented model is simple to use and provides an improvement over the existing equations for 452 pure substances in wide boiling range. The results showed that the proposed correlation is more accurate than the literature methods for pure substances in a wide boiling range (20.3-722 K).