The geometry of a solar still determines the convection constants C and n, which in turn affect the convection heat transfer coefficient’s value and mass. A method for determining the value of convection heat transfer constants C and n has already been developed by the researchers. Therefore, this study aimed to use several methods and theories to find the value of convection heat transfer constants C and n. The results are then compared with the results of the study. The solar still used in this study has one slope. To reduce variables that cannot be controlled, the data collection was conducted indoors using a halogen lamp that can be regulated as a heat source for 24 hours nonstop. The sea surface height in the solar still was maintained at a height of 20 mm, using a height regulator. Temperature was measured using a data logger set to enter data every hour. The desalinised clean water was stored in bottles placed on scales that were recorded every one hour. Room temperature was maintained in the range of 35 to 36 oC. The data in this study were used to calculate the heat transfer constants C and n to obtain the value of the convection heat transfer coefficient and mass calculation. This study compares the calculation models of Tiwari, Dunkle and Power. The following calculation model results: Tiwari model, C = 0.082 and n = 0.612; Dunkle model, C = 0.075 and n = 1/3; Power model, C = 0.815 and n = 0.611. The C and n values obtained with these four approaches reveal that the results from the Power model calculation are the closest to the actual mass, showing a percentage deviation of 1.63%.
This paper presents the results from numerical investigations carried out on circular footing rests on Geo-grid reinforced sand. The finite element program (Plaxis-2D) was used to study experimental results carried out by [1]. This experimental work was used to study the effect of variation of Geo–grid reinforced layers number (N = 0, 1, 2, and 3) under circular footing. The numerical validation with experimental work was considerably agreed with an average percentage of 93%. Then a parametric study was conducted to evaluate the soil performance under circular footing, while applying the same loading conditions. Several parameters have been investigated to identify the optimumsoil behaviour that achieves optimum bearing capacity and minimum settlement under the footing. The parameters include number of Geo-grid layers (N), the Geo-grid layer width (L), the spacing between the footing base and topmost Geo-grid layer (U), the spacing between Geo-grid layers (h) and the Geo-grid stiffness (K). The results indicated that by increasing the number and the width of the Geo-grid reinforced layers the bearing capacity ratio increases up to a limited extent. Moreover, the optimum number of Geo-grid layer equals four layers for circular footing.
The efficacy of erosion control systems depends on preventing soil loss underneath and maintaining its integrity under the effects of the water flow. The paper presents the research results at the Colorado State University on the performance of double twisted wire mesh products, known as Reno Mattresses, used as soil erosion control systems. Mattresses were subjected to various flow conditions on a 10 m long flume placed on a soil layer. The performance against erosion was evaluated by assessing the effect of the stone motion inside the mattress combined with the condition of incipient soil erosion underneath, in relationship to the mattress thickness, the filling stone properties, and under variable hydraulic flow regimes. At the same time, confirming the stability obtained using the conventional tractive force design approach, the research results allowed to introduce a new performance limit based on incipient soil erosion underneath the revetment. Based on the research results, the authors propose to express the shear resistance of mattresses used as soil erosion control systems as a function of the filling stones’ size, uniformity, unit weight, mattress thickness, and the presence of vertical strengthening elements.
Natural fiber composite materials have been widely applied for various purposes, one of which is reducing noise. Many efforts have been tried to reduce noise by using sound absorbing materials such as glasswool, rockwool, and gypsum as sound absorbers, but because of the high price and bad impact on health, many studies have been conducted to find materials that are practical, cheap, and abundant availability in nature, one of which is natural fiber as an alternative to commercial sound absorbing materials. In this study, we want to know the effect of the composition of palm fronds with polyester resin can affect the sound absorption of a material and the effect of composition on sound absorption. The composition of palm frond fiber and polyester resin was varied 60%:40%, 65%:35%, 70%:30%, 75%:25%, 80%:20%, 85%:15%, 90%:10%, arranged randomly with a length of 5 mm. The specimen synthesis process starts with cutting the palm fronds, decomposing the palm frond fibers so that the fibers are separated from the flesh. Acoustic testing was conducted using a single microphone impedance tube. The test results showed that the largest absorption coefficient value is 0.984 at a frequency of 1500 Hz and is obtained in materials with a composition of 70%: 30%, and for the largest acoustic impendance value is 1.714 which is found at a frequency of 500 Hz and is obtained in the composition of 85%: 15%.
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