This study consists of effect of the rain infiltration with the increase of surface temperature and gasifiers using Refuse derived fuel is investigated using a commercial CFD code (STAR-CCM+ 7.02).

The first topic deal with the lab scale experiment together with the effort of numerical calculation have been performed to evaluate the basic assumption of run-off mechanism by the elevation of land surface temperature.

To this end, first of all, a series of experiment has been made over 10 times in terms of the change of soil temperature with well-sorted coarse sand having porosity of 35 % and particle diameter, 1.999mm.

In specific, in case 1, the ground surface temperature was kept at 15 C, while in case 2 that was high enough at 70℃. The temperature of 70℃ was tested as first try since the informal measured surface temperature of black sand in California''s Coachella Valley up to at 191 deg. F(88 ℃).

As a result of this experimental study, it is well found that flux of runoff at 70 Celsius has increased more than 5% compared to that at 15 Celsius. The normalized increase of the relative amount infiltration by the decrease of the surface temperature from 70 to 15 ℃ is about more than 30%. The result of numerical calculation performed was well agreed with the experimental data and physically acceptable.

Doing this successfully, a basic but important research will be made in the near future for the more complex and advanced topic in the area of the water resource management and climate disaster prevention strategy.

The second problem is optimization of the gasifier using combustible wasteuel. The waste management is become a very crucial issue in many countries, due to the ever-increasing amount of waste material.

Recent studies have focused on an innovative technology, the gasification, that has been demonstrated as one of the most effective and environmentally friendly methods for solid waste treatment and energy utilization. In this study, a plasma gasification process based on up-draft fixed bed gasifier has been investigated by developing a thermochemical model able to estimate the syngas composition.

In this study, this optimization of gasifier was numerically evaluated for the following rate of injected air(ER=0.25, 0.3, 0.35, 0.45)and steam (S/C(steam and carbon mole ratio)=0.0, 1.1, 2.2, 3.0). lastly, angle of steam injector was changed as 3stages (degree=30, 45, 90).

Results show that better plant solution depends on both equivalence ratio(ER) and steam and carbon mole ratio(S/C). The plasma gasification efficiency is the best at ER=0.35 and S/C=2.2. At this operating condition, syngas mole fraction of the product gas is 0.37 and CO2 is much lowered. Based on the simulated results, an optimal condition is suggested for gasifier using combustible waste.