A STUDY OF THERMALLY-INDUCED PUMPING OF CARBON DIOXIDE THROUGH NATURAL RUBBER MEMBRANES
Abstract
This investigation was concerned with the pumping action induced by temperature differences for a carbon dioxide-natural rubber membrane system. The phenomenon is often referred to as the "thermo-osmosis effect". Similar known phenomena for other systems were reviewed. The objective of utilizing these phenomena to operate a pump without mechanical moving parts was pursued. A stainless steel diffusion cell with a total volume of 680 cm('3) was designed and constructed. The heating and cooling were performed by two thermal baths. The temperatures inside the hot and cold chambers were monitored with thermocouples. Pressure levels were read from a Heise gage, and the pressure difference indicating the presence of the thermo-osmosis effect was recorded from a U-tube with a manometer fluid having a specific gravity of 2.95. The experimental procedure for measuring this effect is described. Eight test runs were performed with the experimental system. The temperature of the warm bath varied from 50(DEGREES)C to 90(DEGREES)C, while the temperature of the cold bath varied from -10(DEGREES)C to 20(DEGREES)C. Natural rubber membranes from different sources were tested, and the existence of the thermo-osmosis effect was verified. At a temperature difference of 5(DEGREES)C across the membrane, and for an average pressure level of 3 atm, a maximum steady state pressure difference of 14 cm Hg was observed. Variations in the thermo-osmosis effect were observed depending upon the various choices of average pressure level and temperature values, the membrane type and the condition of the membrane. A theoretical discussion based on the temperature dependence of the solubility of a gas-polymer system is given. This involves treatment of the stationary pressure difference, the maximum mass flow rate, the response time of the process, the isothermal permeability, and the thermo-osmotic permeability of the membrane. The thermo-osmosis effect is also discussed within the scope of the irreversible thermodynamics. The quantitities such as the heats of transport and the coupling index are introduced. A direct energy analysis is also presented in relation to the degree of coupling of the process. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI
Degree
Ph.D.
Subject Area
Mechanical engineering
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