Jirasak Kongkiattikajorn

Experimental Study of Heat Transfer in Soil to Inhibit Microbial Growth Using the Underground Release of Hot Water and a Hydraulic Head Method

ABSTRACT This research aimed to study the effectiveness of heat transfer in soil using the underground release of hot water with a hydraulic head. Pressure heads of 1.0, 1.5 and 2.0 m were utilized for underground release with a nozzle to investigate heat transfer in soil necessary to inhibit microbial growth through underground hot water release using a pressure head of liquid. The nozzle was made of stainless steel pipe (SUS304). The proposed system was designed to inhibit microbes of Ralstonia solanacearum with a hot water volume flow of 300, 400 and 500 ml min−1, while temperature was kept constant at 70 ºC. The hot water released underground provided higher soil temperature with shorter working time. The research found that the number of layers and diameter of drilled holes had a significant effect on soil temperature distributed at various depth levels (y-plan), resulting in enhanced performance (100%) for the inhibition of microbes in an x-plan radius of 15 cm for a shorter time of 20–30 min with one nozzle.

Effect of Solar Concentrator System on Disinfection of Soil-Borne Pathogens and Tomato Seedling Growth

The development of non-imaging reflectors for circular-cylindrical solar energy receivers has consisted primarily of investigations on symmetrical V-trough and compound parabolic concentrator (CPC) designs, with the latter being favoured recently because of its superior optical collection. However, it has since been realised that asymmetrical versions of such reflectors may be developed and that they have their own limits of concentration and ideality. It was shown that ideal asymmetrical reflectors could achieve substantially greater peak concentration than symmetrical reflectors of the same acceptance angle (Mills and Giutronich, 1979). An important difference, however, is that the performance of the asymmetrical reflector is much higher at one solstice than another because the aperture is adjusted with respect to the acceptance angle envelope. With an asymmetrical collector, the possibility is presented of at least partial bias of the seasonal collector output toward the maximum load period. Such a bias would reduce dumped solar energy in low load periods, allowing a larger usable solar fraction of energy supplied. Phitthayarachasak (Phitthayaratchasak et al., 2005) upgraded the solarization system process to increase its efficiency by applying the asymmetrical compound parabolic concentrator (ACPC) to enable the concentration of more solar radiation by an average of up to 2.5 times. It is convenient to operate because there is no need to adjust the angle of the ACPC unit according to the movement of the sun. The result showed that the soil temperatures at various depths were high enough to inhibit the growth of microbes within a 5 day period. The solarization operating time was distinctly decreased. The solarization system is then a suitable process for destroying or inhibiting the growth of soil microbes which cause plant diseases (Burrafato, 1998; Le Bihan et al., 1997; Bell; 1998). Even though this system is easy to conduct, with less cost, and no pollution, it still needs 4–6 weeks to operate. Therefore, in this study, the CPC combined with an ACPC unit was developed in order to decrease the time for soil microbe inhibition to be closer to the time of traditional steaming methods.