In ceramic membrane preparation, drying variables and its phenomena are very important to ensure no defects and failures in membrane layers. Generally, ceramic membrane consists of several layer with the top structure or layers possesses a very hygroscopic zone that acting as a separator while next two layers are non hygroscopic zone. Combination of these two different multilayer systems that exhibit different properties always associated to the failure of ceramic consolidation structure during the drying and sintering process. Therefore,controlling of drying behavior is very important to ensure a consistent shrinkage exist between these two layers system. Thus in this present work, the drying process of multilayer materials was studied and observed via simulation technique. A two dimensional mathematical model that coupled mass, heat and gas transfer was employed. Finite element method was used to solve the model and numerically compute using Skyline solver to capture highly nonlinear and transient process. The results showed that drying of multilayer material for membrane structure is obviously different from drying of single layer system. Separation zone that acting as hygroscopic zone does play its roles towards effecting higher pore water pressure and gas pressure. Thus, different drying factors can be seen in the layering system. Hence, understanding those drying factors that may cause inhomogeneous shrinkage due to the existence of different porous network in membrane layers is essential to avoid ceramic membrane failure.
Abstract. This paper investigates and presents the simulation of drying for hygroscopic and nonhygroscopic materials. This present work used a coupled mathematical model of mass, heat and gas transfer that implemented to finite element method in two dimensional and numerically compute using Skyline solver to capture highly nonlinear transient process. Bound water contribution was taken into account in the drying of hygroscopic materials by incorporating constitutive equation of bound water. The results showed drying process can be divided into three periods named constant rate period (CRP), first falling rate period (FRP1) and second falling rate period (FRP2). Capillary action is dominated during CRP before vapour diffusion takes place in FRP1. Bound water movement is generated by vapour pressure gradient exists that represent hygroscopic material. IntroductionIn reality of porous material consists of three types of water that indentified as free, capillary and bound water. Free water is able to flow under an applied pressure gradient, capillary water is immobile water held by capillary forces in regions of microporosity, i.e. dead-end pores. Meanwhile, bound water includes both the water strongly held to negatively charged particles surfaces and the water of hydration associated with the mineral charge-balancing unit. The difference level of these types of water will exhibit different properties of porous material that generally known as hygroscopic and non hygroscopic materials. Drying of nonhyrosocpic materials only involve free and capillary water that easily experimentally can be determined and measured with specific equipment. In contrast to that, drying of hygroscopic materials not only involves free and capillarity water but also a tightly bound water that strongly attach to the solid matrix up to hydration temperature [1]. Previous studies on drying of hygroscopic and nonhygroscopic have present different equations and formulations as well as the concept that had been derived [1,2,3,4,5]. Bound water movement is expressed in terms of the diffusion of sorbed water driven by a gradient in the chemical potential of the sorbed water molecules [2]. This similar approach had been used by Kolhapure and Venkatesh[1] during studies of an unsaturated flow of low moisture for porous hygroscopic media. During low moisture contents, pores mainly consist of bound water and vapour. Stanish et al [3] in their development had derived a uniquely explicit expression for boundwater flux in terms of temperature and vapor pressure gradients. Meanwhile, Zhang et al [4] and Haghi [5] revealed that the bound water transport mechanism only effective when saturation irreducible is reached. The movement of bound water in hygroscopic materials is also known as liquid moisture transfer near dryness or sorption diffusion with driving force of vapor transport and without liquid transport [6]. Although substantial efforts have been made in the studies of hygroscopic materials, there are limited references available on modeling drying...
A viscometer is a tool used to determine the strength of a fluid to shear or tensile stress. Meanwhile, engine oils are used to reduce friction and wear during operation and often deteriorate by the dynamic process with the combined effects of working conditions, contaminations and wear conditions. Therefore, the precise characterization of viscosity is important in the analysis of numerous engineering situations that consume engine oils that associate the functionality or performance of vehicles and machinery. This work aims to investigate the Complimentary Split Ring Resonator (CSRR) as a viscometer for engine oils. The antenna using radiation path such as CSRR is commonly used to measure the dielectric property of substances. Hence, this approach is applied to identify the dielectric properties of engine oils and establish the correlation between viscosity and dielectric properties. Eight engine oils from Shell were tested based on their margins in the terms of kinematic viscosity. Each oil was tested and repeated three times before the mean values were determined along with the frequency of 1-9GHz. The findings show no convincing and solid correlation between the two variables due to the small dielectric constant variation of engine oil with different viscosity. However, future works using current resonator will be applied in other applications associated with different material properties to build a predictive model. In addition, future work can consider sweeping in low frequency that might show positive results.
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