Transpiration Cooling System in Al-Co Open-celled Foam having PPI of 13

One-dimensional transpiration cooling system in open-celled foam has been conducted experimentally and numerically to investigate the heat transfer characteristics of combined convection and radiation. The Alumina–Cordierite (Al-Co) open-cell foam having porosity of 0.87 and pores per inch (PPI) of 13 was employed. The upper surface of porous plate was heated by the heat flux of incoming radiation (qRx,f) varying from 0.97 - 16.59 kW/m2 whereas air injection velocity (uf) fed into the lower surface was varied from 0.364 - 1.274 m/s, and then uf was converted as Reynolds number (Re). The results show that the temperature efficiency (hT), indicating how close the mean temperature of a porous heat plate to that of inlet air, increased rapidly with the air injection velocity (Re). It was then saturated and had a constant value at Re higher than 30. The conversion efficiency (hC), which was regarded as the ability of porous material in transferring energy by convection after absorbed from heat radiation, decreased slightly with increasing of qRx,f and uf (Re). The numerical predictions also agreed well with experimental data. Keyword: Open-cell foam, Radiation, Transpiration cooling, Reynolds numbe

Transpiration Cooling System using Open-cellular Alumina-Cordierite Porous Media having Pore Per Inches (PPI) of 6.0

AbstractAnalysis of numerical model and experimental study on steady-state heat transfer characteristics of combinedconvection and radiation of the air transpiration cooling system using the open-cellular porous material was investigated.The Alumina-Cordierite (Al-Co) open - cellular plates, having porosity of 0.873 and pores per inch (PPI) of 6.0, was usedas porous media. The upper surface of porous plate was heated by the heat flux (qR) of incoming radiation varying from0.988 to 16.560 kW/m2 whereas air injection velocity fed into the lower surface was varied from 0.212 to 1.486 m/s. Toreport the results in the paper, the air velocity was rearranged as Reynolds number (Re). From study, the results showedthat the temperature profile of both gas and solid phase increased when qR, increased and Re decreased. The temperature efficiency (ηT) increased first and then was taken to constant level about of 97% for Re > 70. The conversion efficiency (ηC) increased slightly with Re but depend strongly with qR. The agreement between theoretical and experiential data wassatisfactory

Combustion behavior of rotary solid porous burners (RSPB)

The combustion behavior of rotary solid porous burners (RSPB), i.e., temperature (T), exhaust gas (CO and NOx) and combustion efficiency (nc) were investigated. The stainless wire-mesh type of porous media was selected as porous absorber with porosity of 0.82, thickness of 4.2 mm. The rice husk was used as the fuel with the humidity around 12-14%. The experiment showed that the T tends to increase following the rotating velocity (ro) rising around 0.5-1 rpm. When a ro increased to 1.5 rpm, a T had tendency decreasingly. Because, a ro was too high resulting in the fuel in combustion chamber were ejected quickly then the reaction time reduced not enough to burn fuel, leading to incomplete combustion. The air flow rate (Qa) of 40 m3/h and the fuel load input rate (Qf) of 2.3 kg/h, gave the highest of T due to the system become complete combustion. Corresponding to the level of CO, the least level was obtained at ro = 1 rpm, Qf = 2.3 kg/h and Qa = 40 m3/h. The qc yielded highest with 93.7% at the same condition. The NOx in this research was considered as low, not more than 40 ppm in all experimental conditions