Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface
Evaporation and condensation can be seen in our daily lives but also play a key role in technologies that drive our modern society, such as power generation, distillation, refrigeration, and thermal management for buildings and electronics. Over the past century, great advances have been made in imp...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2023
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| Online Access: | https://hdl.handle.net/1721.1/151919 |
| _version_ | 1826212518248316928 |
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| author | Vaartstra, Geoffrey |
| author2 | Lienhard, John H. |
| author_facet | Lienhard, John H. Vaartstra, Geoffrey |
| author_sort | Vaartstra, Geoffrey |
| collection | MIT |
| description | Evaporation and condensation can be seen in our daily lives but also play a key role in technologies that drive our modern society, such as power generation, distillation, refrigeration, and thermal management for buildings and electronics. Over the past century, great advances have been made in improving the performance of evaporators and condensers; yet the risk of overall system performance being bottlenecked by these components remains. Recently, state-of-the-art materials and micro-nanofabrication techniques have been applied to develop high-performance prototypes to prevent such a bottleneck. These advances are pushing toward the fundamental limit of evaporation/condensation in which the kinetics of heat and mass transport at the liquid-vapor interface become rate-limiting. As we approach this regime, experimental validation of our fundamental understanding of these kinetics ensures the accuracy of computationally-efficient models suitable for engineering design. These efforts will aid further innovation of the thermofluid systems which are critical to our modern society.
A century of research on the kinetics of liquid-vapor phase change has provided a plethora of knowledge on the topic, yet the literature contains many discrepancies in theoretical treatment and conflicting experimental results. In this thesis, we seek to bridge the gap between kinetic theory and practical thermofluid engineering using computational analysis, and then experimentally validate the application of the kinetic model to condensation heat transfer. We first apply theory and a high-accuracy numerical technique to evaluate computationally-efficient models for evaporation/condensation rates. We quantify the accuracy of the Schrage equation—an approximation commonly used to predict heat fluxes in thermofluid engineering—and identify an existing moment-based model that ought to be used instead. Next, we fabricate and test an ultrathin, freestanding, nanoporous membrane designed to achieve high experimental sensitivity to the properties of the liquid-vapor interface. As a supplement to that experiment, we use highly-accurate direct simulation Monte Carlo calculations to validate the dusty-gas model. We demonstrate that this model accurately and efficiently predicts gas transport in our experimental system and state-of-the-art membranes that could be used for high-selectivity membrane separation processes.
Finally, we carefully design an experimental setup to observe high-rate dropwise condensation under a microscope with strict measures to prevent contamination. We achieve unprecedented sensitivity to kinetics near the interface and our results validate the kinetic theory for condensation. Further, these experiments show that the accommodation coefficient of water is at least 0.5 and likely quite close to 1, indicating nearly ideal behavior of the interface.
This thesis advances our fundamental understanding of the kinetics of heat and mass transfer near the liquid-vapor interface and provides guidelines for using models that can ultimately lead to better-performing components in power generation, desalination, and thermal management systems. |
| first_indexed | 2024-09-23T15:24:30Z |
| format | Thesis |
| id | mit-1721.1/151919 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T15:24:30Z |
| publishDate | 2023 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1519192023-08-24T03:08:19Z Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface Vaartstra, Geoffrey Lienhard, John H. Massachusetts Institute of Technology. Department of Mechanical Engineering Evaporation and condensation can be seen in our daily lives but also play a key role in technologies that drive our modern society, such as power generation, distillation, refrigeration, and thermal management for buildings and electronics. Over the past century, great advances have been made in improving the performance of evaporators and condensers; yet the risk of overall system performance being bottlenecked by these components remains. Recently, state-of-the-art materials and micro-nanofabrication techniques have been applied to develop high-performance prototypes to prevent such a bottleneck. These advances are pushing toward the fundamental limit of evaporation/condensation in which the kinetics of heat and mass transport at the liquid-vapor interface become rate-limiting. As we approach this regime, experimental validation of our fundamental understanding of these kinetics ensures the accuracy of computationally-efficient models suitable for engineering design. These efforts will aid further innovation of the thermofluid systems which are critical to our modern society. A century of research on the kinetics of liquid-vapor phase change has provided a plethora of knowledge on the topic, yet the literature contains many discrepancies in theoretical treatment and conflicting experimental results. In this thesis, we seek to bridge the gap between kinetic theory and practical thermofluid engineering using computational analysis, and then experimentally validate the application of the kinetic model to condensation heat transfer. We first apply theory and a high-accuracy numerical technique to evaluate computationally-efficient models for evaporation/condensation rates. We quantify the accuracy of the Schrage equation—an approximation commonly used to predict heat fluxes in thermofluid engineering—and identify an existing moment-based model that ought to be used instead. Next, we fabricate and test an ultrathin, freestanding, nanoporous membrane designed to achieve high experimental sensitivity to the properties of the liquid-vapor interface. As a supplement to that experiment, we use highly-accurate direct simulation Monte Carlo calculations to validate the dusty-gas model. We demonstrate that this model accurately and efficiently predicts gas transport in our experimental system and state-of-the-art membranes that could be used for high-selectivity membrane separation processes. Finally, we carefully design an experimental setup to observe high-rate dropwise condensation under a microscope with strict measures to prevent contamination. We achieve unprecedented sensitivity to kinetics near the interface and our results validate the kinetic theory for condensation. Further, these experiments show that the accommodation coefficient of water is at least 0.5 and likely quite close to 1, indicating nearly ideal behavior of the interface. This thesis advances our fundamental understanding of the kinetics of heat and mass transfer near the liquid-vapor interface and provides guidelines for using models that can ultimately lead to better-performing components in power generation, desalination, and thermal management systems. Ph.D. 2023-08-23T16:19:06Z 2023-08-23T16:19:06Z 2023-06 2023-07-19T18:42:23.752Z Thesis https://hdl.handle.net/1721.1/151919 0000-0001-6158-241X In Copyright - Educational Use Permitted Copyright retained by author(s) https://rightsstatements.org/page/InC-EDU/1.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Vaartstra, Geoffrey Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title | Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title_full | Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title_fullStr | Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title_full_unstemmed | Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title_short | Kinetics of Heat and Mass Transfer Near the Liquid-Vapor Interface |
| title_sort | kinetics of heat and mass transfer near the liquid vapor interface |
| url | https://hdl.handle.net/1721.1/151919 |
| work_keys_str_mv | AT vaartstrageoffrey kineticsofheatandmasstransferneartheliquidvaporinterface |