Testing of a Porosity Measuring Apparatus Based on Comparisons of Pressure Decay Rates
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A porosity measuring apparatus based on comparisons of pressure decay rates was developed. The porosity of a granular sample was determinated by conducting two pressurization tests. The apparatus could perform these pressurization tests automatically. In the first and second tests, the sample chamber was empty and filled with the sample, respectively. The air pressure inside the chamber was increased to a specified level and then the inside air was released from the chamber. The pressure in the empty chamber decreased slower than that in the chamber filled with the sample. These different pressure decay rates were used in the calculation of the solid volume and then the porosity of the sample. The four different types of samples were used in this study, three sizes of spherical samples with diameters of 2.35 (±0.01), 5.94 (±0.01) and 37.86 (±0.19) mm and one size of cylindrical samples with a diameter of 21.91 (±1.43) mm and a height of 134.02 (±0.24) mm. The numbers of the sample pieces were ~123,400, 9,435 and 24, and 17, respectively. The porosity measurements from the apparatus were compared against the reference porosities measured based on either the dimensional measurement method or a gas pycnometer. The measurement accuracy was expressed in terms of absolute percentage error and was analyzed using one-way analysis of variance (one-way ANOVA). The main factors were the pressure half-life of the empty sample chamber, initial pressure and type of the sample. The maximum absolute percentage error was 4.44%. In addition, the statistical analysis showed that the main factors and the interaction of each factor pair did not have significant effects on the measurement accuracy (Sig. > 0.05). As a result, the porosity measuring apparatus developed in the present study yielded satisfying accuracy.
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สมาคมวิศวกรรมเกษตรแห่งประเทศไทย
Thai Socities of Agricultural Engineering
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สยาม แกมขุนทด, พานิช วุฒิพฤกษ์, สันชัย อินทพิชัย และ พิทยา แจ่มสว่าง. 2558 ตัวแปรที่มีผลกระทบต่อค่าสัมประสิทธิ์การซึมผ่านของน้ำในดินลูกรังที่มีขนาดคละแตกต่างกัน. วารสารวิชาการพระจอมเกล้าพระนครเหนือ 25(1). 11-19
อภิรัฐ จันทลักษณ์ 2557: การพัฒนาวิธีการวัดความพรุนด้วยวิธีการเปรียบเทียบอัตราการลดลงของความดัน. ปริญญาวิศวกรรมศาสตรมหาบัณฑิต (วิศวกรรมเกษตร) สาขาวิศวกรรมเกษตร ภาควิชาวิศวกรรมเกษตร
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