No abstract

Simulation of nanoscale thermo-fluidic transport has attracted considerable attention in recent years owing to rapid advances in nanoscience and nanotechnology. The three- dimensional molecular dynamics simulations are performed for the system of a liquid layer between two parallel solid walls at different wall temperatures. The solid-solid interaction is modeled by the embedded atom method. The heat flux through the solid-liquid interface is calculated by Green-Kubo method. The effects of interface wettability and wall temperature on the interfacial thermal resistance are also analyzed. It is found that there exist the relatively immobile quasi-crystalline interfacial layers close to each solid wall surface with higher number density and thus higher local thermal conductivity than the corresponding liquid phase. The interfacial thermal resistance length is overestimated by 8.72% to 19.05% for the solid-solid interaction modeled by the Lennard-Jones potential, and underestimated based on heat fluxes calculated by Fourier equation.

A novel flat heat pipe is put forward. The novel flat heat pipe is characteristic of its integral wick structure of microgrooves, which is made of a series of thin aluminum foils folded side by side. The thermal performance of the novel flat heat pipe under the different heat loads and incline angles has been investigated experimentally. It is found that the equivalent thermal conductivity of the novel flat heat pipe can be 12.3 times higher than that of the heat pipe material. Moreover, the novel flat heat pipe with integral micro-grooved wick has good temperature uniformity. The novel flat heat pipe can play a pronounced role in heat transfer enhancement, and be expected to be good candidates for thermal management of electronic devices.

Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels, is widely used for the automobile engines. In order to improve the thermal efficiency of CNG engine, the direct-injection (DI) technology has been adopted. The stratified CNG mixture can be ignited by the spark plug which is installed near the injector nozzle, so the lean combustion can be subsequently achieved. For the direct-injection spark-ignition (DISI) engine, the reliable ignition is a foundational problem for the reliable operation, so it is very important to study on the spray characteristics of DISI engine. In our study, a combustion chamber is designed and a visualization system is built. The DI CNG spray's injection process was digital recorded with the schlieren optical system under different experiment conditions. The spray characteristics of the DI CNG engine were analyzed with the experimental results.

Evaporation at thin liquid film can significantly enhance heat transfer process. A detailed mathematical model predicting the heat and mass characteristics of the evaporating thin film is developed. The model considers effects of inertial force, evaporation coefficient, interface thermal resistance, and disjoining pressure. It is found that the interface thermal resistance is in inverse proportion to the evaporation coefficient. The heat and mass transport characteristics decreases sharply as the evaporation coefficient decreases. The inertial force tends to enhance the heat and mass transport characteristics of the evaporating thin film. However the Reynolds number of the liquid flow in the evaporating thin film is far lower than unity, and thus the effect of the inertial force can be neglected.