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The evaporating thin film region is an extended meniscus beyond the apparent contact line at a liquid/solid interface. Thin film evaporation plays a key role in a highly efficient heat pipe. A detailed mathematical model predicting fluid flow and heat transfer through the thin film region is developed. The model considers the effects of inertial force, disjoining pressure, surface tension, and curvature. Utilizing the order analysis, the model is simplified and can be numerically solved for the thin film profile, interfacial temperature, meniscus radius, heat flux distribution, velocity distribution, and mass flow rate in the evaporating thin film region. The prediction shows that while the inertial force can affect the thin film profile, interfacial temperature, meniscus radius, heat flux distribution, velocity distribution, and mass flow rate, in particular, near the non-evaporating region, the effect can be neglected. It is found that a maximum velocity, a maximum heat flux, and a maximum curvature exist for a given superheat, but the locations for these maximum values are different.friction factor, f ¼ 4s w 1 2 q l u 2 h lv latent heat of vaporization (J/kg) k thermal conductivity (W/m K) K curvature (m -1 ) _ m mass flow rate (kg/s) p pressure (N/m 2 ) P R reference pressure (N/ m) 2 q heat transfer (W) q¢¢ heat flux (W/ m 2 ) Re Reynolds number, Re ¼ q l ud l l t time (s) T temperature (K) u velocity in the x-direction (m/s) " u mean velocity in the x-direction (m/s) v velocity in the y-direction (m/s) x coordinate (m) y coordinate (m) d film thickness (m) d 0 non-evaporating film thickness (m) l viscosity (N s/m 2 ) q density (kg/m 3 ) r surface tension (N/m) s shear stress (N/ m 2 )

Traditional protective garments loaded with activated carbons to remove toxic gases are very bulky. Novel graphene oxide (GO) flake-based composite lamellar membrane structure is being developed as a potential component of a garment for protection against chemical warfare agents (CWAs) represented here by simulants, dimethyl methyl phosphonate (DMMP) (a sarin-simulant), and 2-chloroethyl ethyl sulfide (CEES) (a simulant for sulfur mustard), yet allowing a high-moisture transmission rate. GO flakes of dimensions 300–800 nm, 0.7–1.2 nm thickness and dispersed in an aqueous suspension were formed into a membrane by vacuum filtration on a porous poly­(ether sulfone) (PES) or poly­(ether ether ketone) (PEEK) support membrane for noncovalent π–π interactions with GO flakes. After physical compression of such a membrane, upright cup tests indicated that it can block toluene for 3–4 days and DMMP for 5 days while exhibiting excellent water vapor permeation. Further, they display very low permeances for small-molecule gases/vapors. The GO flakes underwent cross-linking later with ethylenediamine (EDA) introduced during the vacuum filtration followed by physical compression and heating. With a further spray coating of polyurethane (PU), these membranes could be bent without losing barrier properties vis-à-vis the CWA simulant DMMP for 5 days; a membrane not subjected to bending blocked DMMP for 15 days. For the PEEK-EDA-GO-PU-compressed membranes after bending, the separation factors of H2O over other species for low gas flow rates in the dynamic moisture permeation cell (DMPC) are: αH2O–He is 42.3; αH2O–N2 is 110; and αH2O–ethane is 1800. At higher gas flow rates in the DMPC, the moisture transmission rate goes up considerably due to reduced boundary layer resistances and exceeds the threshold water vapor flux of 2000 g/(m2·day) that defines a breathable fabric. This membrane displayed considerable resistance to permeation by CEES as well. The PES-EDA-GO-PU-compressed membrane shows good mechanical property under tensile strength tests.

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A mathematical model predicting the oscillating motion in an oscillating heat pipe is developed. The model considers the vapor bubble as the gas spring for the oscillating motions including effects of operating temperature, nonlinear vapor bulk modulus, and temperature difference between the evaporator and the condenser. Combining the oscillating motion predicted by the model, a mathematical model predicting the temperature difference between the evaporator and the condenser is developed including the effects of the forced convection heat transfer due to the oscillating motion, the confined evaporating heat transfer in the evaporating section, and the thin film condensation in the condensing section. In order to verify the mathematical model, an experimental investigation was conducted on a copper oscillating heat pipe with eight turns. Experimental results indicate that there exists an onset power input for the excitation of oscillating motions in an oscillating heat pipe, i.e., when the input power or the temperature difference from the evaporating section to the condensing section was higher than this onset value the oscillating motion started, resulting in an enhancement of the heat transfer in the oscillating heat pipe. Results of the combined theoretical and experimental investigation will assist in optimizing the heat transfer performance and provide a better understanding of heat transfer mechanisms occurring in the oscillating heat pipe.

It is well known that heat transfer in dropwise condensation (DWC) is superior to that in filmwise condensation (FWC) by at least one order of magnitude. Surfaces with larger contact angle (CA) can promote DWC heat transfer due to the formation of “bare” condensation surface caused by the rapid removal of large condensate droplets and high surface replenishment frequency. Superhydrophobic surfaces with high contact angle (> 150°) of water and low contact angle hysteresis (< 5°) seem to be an ideal condensing surface to promote DWC and enhance heat transfer, in particular, for the steam-air mixture vapor. In the present paper, steam DWC heat transfer characteristics in the presence of noncondensable gas (NCG) were investigated experimentally on superhydrophobic and hydrophobic surfaces including the wetting mode evolution on the roughness-induced superhydrophobic surface. It was found that with increasing NCG concentration, the droplet conducts a transition from the Wenzel to Cassie-Baxter mode. And a new condensate wetting mode—a condensate sinkage mode—was observed, which can help to explain the effect of NCG on the condensation heat transfer performance of steam-air mixture on a roughness-induced superhydrophobic SAM-1 surface.

The copolymer SAFT equation of state is found to represent phase transitions in the normal-alkane and methyl-alkane solutions in methane, ethane, propane, and n-hexane, the polyethylene and poly(ethylene-co-olefin-1) solutions in propane, and the polystyrene solutions in n-butane. The pure-solute parameters are all estimated on the basis of the molecular weight and structure only, and the one temperature-independent and system-independent (within each class of solutes) binary parameter is set equal to a constant. The segment energy of the methyl branches is found to be around 160 K, which is lower than the corresponding backbone energy, while the segment energy of the benzene branches is found to be around 222 K for polystyrene, which is higher than the corresponding backbone energy. The alkyl branches are found to promote the polymer miscibility while the benzene branches are found to inhibit the polymer miscibility in propane.

Polypropylene hybrid composites were made using silica and white rice husk ash (WRHA) fillers as reinforcing agents in the polypropylene (PP) matrix. Both fillers were used at the similar total filler loading i.e., 40% by weight of PP matrix. Results indicate that the increasing loading of WRHA in silica/WRHA weight ratio has increased the flexural modulus and tensile modulus but decrease the tensile strength, stress at yield, elongation at break, Eb and water absorption of PP/silica/WRHA hybrid composites. Degradation study shows that percentage loss of above properties increases with increasing the loading of WRHA in silica/WRHA weight ratio of composites. Scanning electron microscopy (SEM) of tensile fracture surfaces of composites indicates that silica has better adhesion with PP matrix compared to WRHA.