Two prototype transition-metal dichalcogenide (TMDC) materials, MoS 2 and MoSe 2 , have attracted growing attention as promising 2D semiconductors. The heterostructure created by stacking the 2D monolayers in the out-of-plane direction exhibits peculiar properties that can be utilized in electronic applications. The lateral and flexural phonon transport behaviors in MoS 2 /MoSe 2 heterobilayer are comprehensively investigated using classical molecular dynamics simulations. In-plane thermal conductivity (κ) and out-of-plane interfacial thermal resistance (R) are calculated by nonequilibrium molecular dynamics (NEMD) and transient pump−probe methods, respectively. Thermal conductivity of MoS 2 /MoSe 2 bilayer 2D sheet is characterized as 28.8 W/m•K, which preserves the high thermal conductivity of most TMDC materials. The maximum κ reductions of MoS 2 , MoSe 2 , and heterobilayer amount to 83.0, 68.9, and 77.1%, respectively, with increasing temperatures from 100 to 500 K. It is also found that the basal-plane thermal performance of MoS 2 /MoSe 2 bilayer will not be affected by interfacial interactions, which is important in industrial applications. The predicted out-of-plane flexural phonon conductance results reveal that heat flux runs preferably from MoS 2 to MoSe 2 than in the reverse direction.

The dispersion of graphene nanoparticles in a fluid can enhance the thermophysical properties of the base liquid. The physics behind such a phenomenon has yet to be uncovered in the community. In this work, thermal transport in a graphene–water mixture is studied by classical molecular dynamics simulations. Several factors including orientation angle, curvature, thermal rectification, temperature, and van der Waals interaction are investigated, and special attention is paid to the effect on thermal conductance across graphene–water interfaces. It is found that thermal conductance increases from 13.92 to 26.70 MW/m2 K as the orientation angle is increased from 0° to 90°. When the curved graphene is introduced by altering the length to width ratio from 1.0 to 1.8, the thermal conductance is elevated. However, as the length to width ratio exceeds 1.8, such a trend does not continue due to the variation of the intrinsic thermal conductivity of graphene and the formation of the complex graphene–water interface. Even though the curved graphene introduces an asymmetric assembly, no thermal rectification effect is observed for diverse directions of heat flux. It is demonstrated that the enhancement of overall thermal conductance of nanofluids is ascribed to the interface thermal transport rather than the base liquid with increasing temperature. This correlation is suppressed in a hydrophilic interface due to the structural change of liquid layer adjacent to the interface.

As power electronics shrinks down to sub-micron scale, the thermal transport from a solid surface to environment becomes significant. Under circumstances when the device works in rare gas environment, the scale for thermal transport is comparable to the mean free path of molecules, and is difficult to characterize. In this work, we present an experimental study about thermal transport around a microwire in rare gas environment by using a steady state "hot wire" method.Unlike conventional hot wire technique of using transient heat transfer process, this method considers both the heat conduction along the wire and convection effect from wire surface to surroundings. Convection heat transfer coefficient from a platinum wire in diameter 25 m to air is characterized under different heating power and air pressures to comprehend the effect of temperature and density of gas molecules. It is observed that convection heat transfer coefficient varies from 14 W/m 2 K at 7 Pa to 629 W/m 2 K at atmosphere pressure. In free molecule regime, Nusselt number has a linear relationship with inverse Knudsen number and the slope of 0.274 is employed to determined equivalent thermal dissipation boundary as 7.03×10 -4 m. In transition regime, the equivalent thermal dissipation boundary is obtained as 5.02×10 -4 m. Under a constant pressure, convection heat transfer coefficient decreases with increasing temperature, and this correlation is more sensitive to larger pressure. This work provides a pathway for studying both heat conduction and heat convection effect at micro/nanoscale under rare gas environment, the knowledge of which is essential for regulating heat dissipation in various industrial applications.

A fluorescence signal has been demonstrated as an effective implement for micro/nanoscale temperature measurement which can be realized by either direct fluorescence excitation from materials or by employing nanoparticles as sensors. In this work, a steady-state electrical-heating fluorescence-sensing (SEF) technique is developed for the thermal characterization of one-dimensional (1D) materials. In this method, the sample is suspended between two electrodes and applied with steady-state Joule heating. The temperature response of the sample is monitored by collecting a simultaneous fluorescence signal from the sample itself or nanoparticles uniformly attached on it. According to the 1D heat conduction model, a linear temperature dependence of heating powers is obtained, thus the thermal conductivity of the sample can be readily determined. In this work, a standard platinum wire is selected to measure its thermal conductivity to validate this technique. Graphene quantum dots (GQDs) are employed as the fluorescence agent for temperature sensing. Parallel measurement by using the transient electro-thermal (TET) technique demonstrates that a small dose of GQDs has negligible influence on the intrinsic thermal property of platinum wire. This SEF technique can be applied in two ways: for samples with a fluorescence excitation capability, this method can be implemented directly; for others with weak or no fluorescence excitation, a very small portion of nanoparticles with excellent fluorescence excitation can be used for temperature probing and thermophysical property measurement.

Based on the method of discrete phase, the law of droplets' deposition in the last stage stationary blade of a supercritical 600 MW Steam Turbine is simulated in the first place of this paper by using the Wet-steam model in commercial software FLUENT, where the influence of inlet angle of water droplets of the stationary blades is also considered. Through the calculation, the relationship between the deposition and the diameter of water droplets is revealed. Then, the amount of droplets deposition in the suction and pressure surface is derived. The result is compared with experimental data and it proves that the numerical simulation result obtained in this paper is reasonable. Finally, a formula of the relationship between the diameter of water droplets and the inlet angle is fit, which could be used for approximate calculation in the engineering applications.

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