Investigating Transport Properties of Environmentally Friendly Azeotropic Binary Blends Based on Evaporation in Auto-Cascade Refrigeration

The exploration of performance and prediction of environmentally friendly refrigerant physical properties represents a critical endeavor.Equilibriummolecular dynamics simulationswere employed to investigate the density and transport properties of propane and ethane at ultra-low temperatures under evaporative pressure conditions.The results of the density simulation of the evaporation conditions of the blends proved the validity of the simulation method.Under identical temperature and pressure conditions,increasing the proportion of R170 in the refrigerant blends leads to a density decrease while the temperature range in which the gas-liquid phase transition occurs is lower.The analysis of simulated results pertaining to viscosity,thermal conductivity,and self-diffusion coefficient reveals heightened deviation levels within the phase transition temperature zone.This increase in deviation attributed to intensified molecular activity.In terms of uncovering the physical mechanism of gas-liquid phase transition,the work illustrates the macroscopic phenomenon of the intensified existing disorder during phase transitions at the molecular level.Molecular dynamics simulations analyzing the thermophysical properties of refrigerant blends from a microscopic point of view can deepen the comprehension of the thermal optimization of refrigeration processes.

Impact of binary blends of biodiesels on fuel quality,engine performance and emission characteristics

The incessant pressure of energy requirements by the growing global populace has led to the exploration of unconventional methods to produce renewable and sustainable fuels.Among these,biodiesel is most suited to the present needs of eco-friendly standards to keep the atmosphere free from residual emissions.Various fuel-modification methods were developed over a couple of decades to make biodiesel suitable for diesel engines.In the present research,Jatropha curcas biodiesel and waste-cooking-oil(WCO)biodiesel were used to craft a unique binary blend to obtain desirable fuel properties and operational suitability for the diesel engine.The blend with 80% WCO biodiesel and 20% J.curcas biodiesel,which had the most suitable fuel properties,was tested on a four-stroke single-cylinder vertical diesel engine.The emissions and operational parameters were analysed and compared with diesel.The results of the study indicated that engine emissions for binary blend,carbon monoxide and unburnt hydrocarbon emissions were highly reduced,and carbon dioxide and nitrogen oxide(NO_(x))emissions increased relative to diesel.At full load,NO_(x) emission was found to be 51.32% higher than that from diesel and 3.8% lower than that from WCO biodiesel.Engine performance showed that for the binary blend,at full load,the brake-specific fuel consumption was 396.82 g/kWh,which was 15.26% higher,and the brake thermal efficiency was 22.7%,which was 2.74% lower than regular diesel fuel.The present study suggests that the binary blend of J.curcas biodiesel and WCO biodiesel can be a promising approach towards advancements in the fuel properties of biodiesels.

Dynamics of Polypropylene Chains in Their Binary Blends of Different Stereochemical Sequences Studied by Monte Carlo Simulations

The conformational and dynamic properties of polypropylene （PP） for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic （iPP）, atactic （aPP） and syndiotactic （sPP） polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state （RIS） model and Lennard-Jones （LJ） potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as： iPP 〉 aPP 〉〉 sPP. For PP/PP blends with 50：50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular （molecular size and chain stiffness） and intermolecular （chain packing） interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.

Synthesis of PP-g-PIP and Properties of PP/PP-g-PIP Binary Blends

The polypropylene-grafl-polyisoprene （PP-g-PIP） copolymers with different side chain length were synthesized by the combination of solid phase graft and anionic polymerization. The copolymers were characterized by nuclear magnetic resonance spectrum （1H-NMR）, gel permeation chromatography （GPC） and differential scanning calorimetry （DSC）. Five PP/PP-g-PIP blends with PP-g-PIP as a flexibilizer to toughen PP were prepared and characterized by scanning electron microscope （SEM）, dynamic mechanical analysis （DMA）, DSC, wide-angle X-ray diffraction （WAXD）. Their morphologies, glass transition temperatures, crystallinity and mechanical properties were investigated. All the results pointed out that the covalent bonding of PP and PIP increased the compatibility and interfacial adhesion, which led to PIP well dispersed in the system and small size PIP particles in the binary blends. In addition, the toughness of PP was improved while its tensile strength slightly decreased.