Abstract
Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed.
Highlights
Separation and recovery of water vapor from industrial processes
Gas Technology Institute (GTI) in the United States developed a new membrane technology of transport membrane condenser (TMC) based on a nanoporous ceramic separation membrane[19,20], which was employed to extract a portion of water vapor and its latent heat from the flue gas and return the recovered water and heat to the steam cycle
We experimentally investigated and compared the performance of heat and mass transfer on original, modified hydrophilic and hydrophobic NPCM tubes
Summary
Separation and recovery of water vapor from industrial processes Their experimental results indicated that 20% water recovery was achieved with temperature reduction below 5 °C. Both asymmetric microporous spongelike ethylene-chlorotrifluoroethylene copolymer (ECTFE) flat sheet membranes and commercial polyvinylidene fluoride (PVDF) hollow fiber membranes were tested by varying the feed temperature and feed flow rate[16]. PVDF microporous hydrophobic fibers assembled in a module were tested by Brunetti et al.[17] It was found that 25% water vapor contained in the feed was recovered at the temperature difference of 8 °C and the ratio of the feed flow rate with the membrane area was a fundamental parameter to be taken into account in the design of the membrane unit. We experimentally investigated and compared the performance of heat and mass transfer on original, modified hydrophilic and hydrophobic NPCM tubes. A computational model of a single nanopore with different wettability was established using the molecular dynamics simulations to reveal the infiltration characteristics of liquid molecules into hydrophilic/ hydrophobic nanopores
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