Droplet evaporation coupled with gravity and surface tension on a wall with the radial Temperature gradients is numerically studied with the arbitrary Lagrangian‒Eulerian method. The influence of the wall Temperature distribution on the droplet evaporation process, which is less considered in the existing literature, is mainly discussed. The droplet Temperature coefficient of the surface tension and the viscosity on the droplet profile evolution, flow, heat and mass transfer characteristic are also discussed. The results indicate that the droplets become flat first and then retract under the gravity and Marangoni convection during droplet evaporation. There are two high-velocity regions inside the evaporating droplet. One region is at the droplet axis, in which fluid flows to the wall from the droplet top. The other region is near the droplet surface, where fluid flows to the droplet top. There are turning points on the two sides of which the influence of wall Temperature distribution on the ratio between the droplet height and the radius of the three-phase contact line (h/Rc), the velocity in the droplet and the surface Temperature converts. All of them are larger before the turning point when the wall Temperature slope is positive. After the turning point, these are reversed. For both h/Rc and average surface Temperature, there is one turning point, which are t*=1.63×10-4 and t*=1.05×10-4, respectively. For maximum velocity and average velocity in droplet, there are two turning points, which are both t*=1.63×10-4 and t*=1.7×10-5. The droplet morphology changes more obviously when it is with a greater Temperature coefficient of surface tension. Moreover, the turning point is delayed from t*=6.41×10-5 while α is 8 K/m to t*=7.91×10-5 while α is -8 K/m, which indicates that the negative wall Temperature slope is beneficial to inhibit the Marangoni effect on droplet evaporation.

This paper examines the deficiencies of existing oil spillage remediating techniques and their inabilities to achieve optimal result at maximum efficiency. The development of alternative strategy for remediating oil spillage is an idea conceived from a natural phenomenon based on obvious physical changes between oil and water at lower Temperature. The technique involves extensive studies of the physical, chemical and thermodynamic properties of water and hydrocarbons as well as oceans and characteristics of oceans as it is affected by Temperature change, climatic condition, heat gradient, salinity, wind speed, and heat stratification. The paper also exploited critical analysis of the thermodynamics of heat transfer between two objects in constant contact as well as the existing oil spillage remediating techniques or devices for sea and land pollution. The new device was designed to generate high quality crude oil continuously from crude oil/ water mixture optimally when the operational conditions are followed strictly. The step by step derivation of equation for the quantity of recovered oil from the empirical data through graphical analyses is a real representation of the conditions for effective operation of the machine in an oceanic environment. The new technique has shown a very high efficiency in quality oil separation and remediation process for a short run as well as optimal efficiency close to one hundred percent for a long run. The results achieved in the operation of the new system are well appreciable when compared with the existing remediating techniques, although, it may be necessary to use an intermediary wave neutralization system in a rough oceanic environment to improve the oil quality and maximize efficiency.

Dispersion of heavy gases is considered to be more hazardous than the passive ones because it takes place more slowly. When the gas is accidentally released at ground level or where there are many obstacles in the area it is considered to be a heavy gas. In this paper, based on the extensive experimental work of McQuid and Hanna, the model was tested against two types of experiments: A simple experiment “Thorney Island” and a complex experiment “Kit Fox” in order to validate CFD code. In order to accomplish this validation the multiphase approach was employed. Also, the vertical Temperature gradient in the atmosphere was investigated. The investigation of wind speed was done taking factors such as time, height and direction into consideration. In order to reduce the number of elements in the computational domain, a combination of 2D and 3D geometry was utilized. The results showed that the wind inlet correction, as well as the Temperature gradient, had a significant influence on gas concentration records.