Gravity-dependent Transport in Industrial Processes

Gravity dependent transport phenomena in various industrial processes are investigated in order to indicate new directions for micro-gravity research that enhance the commercial success of the space program. The present article describes the commercialization possibilities of such topics associated with physicochemical transport phenomena. The topics are: coating flow, rotating electrochemical system, and convection in low Prandtl number fluids. The present study is directed to understand these phenomena, and to develop a knowledge base for their applications with emphasis to a micro-gravity environment. INTRODUCTION Ostrach (ref. 1) indicated new directions for micro-gravity research that could enhance the commercial success of the space program. In particular, it is pointed out that the research is dispersed over a number of disciplines but the underlying, and unifying basis for new and unusual aspects are gravitationally modified biophysicochemical transport phenomena. The important implications include the effects of fluid flow, heat and mass transfer on biology and chemical reactions. Inversely, the transport phenomena associated with such processes are different in a modified gravitational environment. Such phenomena are vital elements of the chemical, pharmaceutical, energy production, material processing, and biotech industries. The present results demonstrate a great potential for space applications. Furthermore, ground-based research and the corresponding industrial applications in space have been identified. The present research effort has resulted in various topics. First, transport phenomena in zeolite growth were thoroughly investigated, and subsequently a method for increasing the crystal size by adding nutrient after crystallization was developed. Second, the effect of regular and random modes g-jitter, on liquid motion in an open container under microgravity environment was examined numerically and analytically. Third, a theoretical analysis of bubble formation in continuous liquid phase under both terrestrial and microgravity environments investigated though more experimental research is still under way. Fourth, an experimental study on double diffusive convection was completed. Fifth, a scaling and theoretical analysis were performed to understand transport phenomena in supercritical fluid extraction. To date, all these topics have been thoroughly investigated and a detail description can be found elsewhere (rcf 1 and 12). The current research topics are described individually in the following sections: rotating electrochemical systems, coating flows, and convection in low Prandtl number fluids. ROTATING ELECTROCHEMICAL SYSTEMS The present study shows that there is a need to increase mass transport by a rotating system to achieve a high density power system in micro-gravity. Ostrach et al., (ref. 2) completed scaling and experimental studies on natural convection in a shallow rotating annulus subjected to axial stable temperature gradient. The present work, in essence, is an e.xtension of that study. The present research was motivated by the discovery of a rotating nickel-zinc (Ni-Zi) battery system The main advantages of this system include the following: a high specific energy (-80 KWh/Kg), an excellent power performance (-100 + KW/Kg), a good performance in cold ambient temperatures, inexpensive, and low toxicity materials. These excellent performance characteristics make a rotating battery a leading candidate for energy generation and storage in micro-gravity. The development and commercialization of stationary Ni-Zn battery have been hindered for decades mainly due to the limited life cycles. Failure of this battery is typically associated with two phenomena: First, zinc dendrite formation and propagation that leads to the cell shorting. Second, zinc material redistribution (or shape change), which leads to gradual capacity loss. Conversely, by rotating the battery, the following performance enhancements are noticed: First, at rotations corresponding to 50 times the earth's gravitation the dentrite gro_ is nearly eliminated. This 759 https://ntrs.nasa.gov/search.jsp?R=19970000475 2018-03-27T20:23:20+00:00Z