The extremum principle of mass entransy dissipation and its application to decontamination ventilation designs in space station cabins |
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Authors: | Qun Chen JianXun Ren ZengYuan Guo |
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Institution: | (1) Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China |
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Abstract: | In terms of the analogy between mass and heat transfer phenomena, a new physical quantity, i.e. mass entransy, is introduced
to represent the ability of an object for transferring mass to outside. Meanwhile, the mass entransy dissipation occurs during
mass transfer processes as an alternative to measure the mass transfer irreversibility. Then the concepts of mass entransy
and its dissipation are used to develop the extremum principle of mass entransy dissipation and the corresponding method for
convective mass transfer optimization, based on which an Euler’s equation has been deduced as the optimization equation for
the fluid flow to obtain the best convective mass transfer performance with some specific constraints. As an example, the
ventilation process for removing gaseous pollutants in a space station cabin with a uniform air supply system has been optimized
to reduce the energy consumption of the ventilation system and decrease the contaminant concentration in the cabin. By solving
the optimization equation, an optimal air velocity distribution with the best decontamination performance for a given viscous
dissipation is firstly obtained. With the guide of this optimal velocity field, a suitable concentrated air supply system
with appropriate air inlet position and width has been designed to replace the uniform air supply system, which leads to the
averaged and the maximum contaminant concentrations in the cabin been decreased by 75% and 60%, respectively, and the contaminant
concentration near the contaminant source surface been decreased by 50%, while the viscous dissipation been reduced by 30%
simultaneously.
Supported by the National Basic Research Program of China (Grant No. G2007CB206901) |
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Keywords: | convective mass transfer mass entransy dissipation space station decontamination ventilation optimization |
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