{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/83874"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/83874","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Predicting the Air-Side Thermal -Hydraulic Performance Characteristics of Flat-Tube Louver-Fin Heat Exchangers Under Dry and Wet Conditions","abstract":"A simple area-partitioning method for analyzing the wind-tunnel data is developed for flat-tube heat exchangers under partially wet conditions, and new air-side performance correlations are presented for both dry- and wet-surface conditions. Correlations between the Colbum j or f factors and the Reynolds numbers are developed in the conventional way and compared to multivariate non-parametric regressions. The conventional correlations significantly extend prior work by expanding the parameter space and establishing a physical basis for the form of the fits. However, it is found that multivariate non-parametric regressions can dramatically reduce the RMS errors if a large, well-structured dataset is used. Furthermore, this method provides statistical indicators that can be used to prevent over-fitting when the dataset is limited. Important condensate retention and drainage mechanisms are identified and modeled using analytical and numerical methods. When condensate obstructs the louver gap, boundary layer re-starting does not occur, and the most important heat transfer enhancement mechanism in these flows lost. It is shown that surface tension can maintain inter-louver condensate bridges against gravity and flow-generated shear and pressure forces, even at air-side Reynolds numbers much higher than are typical to the applications of interest. Thus, maintaining wet-surface heat transfer performance depends on avoiding the initial formation of inter-louver bridges.","abstract_html":"A simple area-partitioning method for analyzing the wind-tunnel data is developed for flat-tube heat exchangers under partially wet conditions, and new air-side performance correlations are presented for both dry- and wet-surface conditions. Correlations between the Colbum j or f factors and the Reynolds numbers are developed in the conventional way and compared to multivariate non-parametric regressions. The conventional correlations significantly extend prior work by expanding the parameter space and establishing a physical basis for the form of the fits. However, it is found that multivariate non-parametric regressions can dramatically reduce the RMS errors if a large, well-structured dataset is used. Furthermore, this method provides statistical indicators that can be used to prevent over-fitting when the dataset is limited. Important condensate retention and drainage mechanisms are identified and modeled using analytical and numerical methods. When condensate obstructs the louver gap, boundary layer re-starting does not occur, and the most important heat transfer enhancement mechanism in these flows lost. It is shown that surface tension can maintain inter-louver condensate bridges against gravity and flow-generated shear and pressure forces, even at air-side Reynolds numbers much higher than are typical to the applications of interest. Thus, maintaining wet-surface heat transfer performance depends on avoiding the initial formation of inter-louver bridges.","abstract_has_math":false,"creators":["Park, Young-Gil"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Jacobi, Anthony M."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T21:12:32Z","date_published":"2015-09-25T21:12:32Z","updated_at":"2026-07-22T22:26:22Z","subjects":["Engineering, Mechanical"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3270001"],"render_values":[{"text":"(MiAaPQ)AAI3270001","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/83874","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Jacobi, Anthony M."]},{"key":"dc:creator","label":"Author","values":["Park, Young-Gil"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T21:12:32Z","10000-01-01","2007"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engineering, Mechanical"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/83874","(MiAaPQ)AAI3270001"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A simple area-partitioning method for analyzing the wind-tunnel data is developed for flat-tube heat exchangers under partially wet conditions, and new air-side performance correlations are presented for both dry- and wet-surface conditions. Correlations between the Colbum j or f factors and the Reynolds numbers are developed in the conventional way and compared to multivariate non-parametric regressions. The conventional correlations significantly extend prior work by expanding the parameter space and establishing a physical basis for the form of the fits. However, it is found that multivariate non-parametric regressions can dramatically reduce the RMS errors if a large, well-structured dataset is used. Furthermore, this method provides statistical indicators that can be used to prevent over-fitting when the dataset is limited. Important condensate retention and drainage mechanisms are identified and modeled using analytical and numerical methods. When condensate obstructs the louver gap, boundary layer re-starting does not occur, and the most important heat transfer enhancement mechanism in these flows lost. It is shown that surface tension can maintain inter-louver condensate bridges against gravity and flow-generated shear and pressure forces, even at air-side Reynolds numbers much higher than are typical to the applications of interest. Thus, maintaining wet-surface heat transfer performance depends on avoiding the initial formation of inter-louver bridges.","Made available in DSpace on 2015-09-25T21:12:32Z (GMT). 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Correlations between the Colbum j or f factors and the Reynolds numbers are developed in the conventional way and compared to multivariate non-parametric regressions. The conventional correlations significantly extend prior work by expanding the parameter space and establishing a physical basis for the form of the fits. However, it is found that multivariate non-parametric regressions can dramatically reduce the RMS errors if a large, well-structured dataset is used. Furthermore, this method provides statistical indicators that can be used to prevent over-fitting when the dataset is limited. Important condensate retention and drainage mechanisms are identified and modeled using analytical and numerical methods. When condensate obstructs the louver gap, boundary layer re-starting does not occur, and the most important heat transfer enhancement mechanism in these flows lost. It is shown that surface tension can maintain inter-louver condensate bridges against gravity and flow-generated shear and pressure forces, even at air-side Reynolds numbers much higher than are typical to the applications of interest. Thus, maintaining wet-surface heat transfer performance depends on avoiding the initial formation of inter-louver bridges.","Made available in DSpace on 2015-09-25T21:12:32Z (GMT). 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