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Master's Dissertation
DOI
https://doi.org/10.11606/D.18.2011.tde-29082011-171131
Document
Author
Full name
Fábio Toshio Kanizawa
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2011
Supervisor
Committee
Ribatski, Gherhardt (President)
Barbosa Junior, Jader Riso
Hernandez Rodriguez, Oscar Maurício
Title in Portuguese
Estudo teórico e experimental sobre padrões de escoamento e perda de pressão durante escoamentos monofásicos e bifásicos no interior de tubos com fitas retorcidas
Keywords in Portuguese
Ebulição convectiva
Fitas retorcidas
Padrões de escoamento
Perda de pressão
Térmica e fluidos
Abstract in Portuguese
A presente dissertação trata de um estudo teórico-experimental sobre escoamento monofásico e bifásico no interior de tubos com fitas retorcidas. Esta técnica tem sido utilizada há várias décadas para a intensificação de troca de calor para escoamento monofásico e evaporação convectiva no interior de tubos. No entanto, com sua utilização, o aumento do coeficiente de troca de calor é acompanhado pelo incremento da perda de pressão. Portanto a compreensão dos fenômenos relacionados aos incrementos da perda de pressão e troca de calor são fundamentais para engenheiros projetistas. Neste estudo, inicialmente, é apresentada uma extensa revisão bibliográfica sobre padrões de escoamento, modelos para estimativa de fração de vazio e metodologias para previsão da perda de pressão em tubos com e sem fitas retorcidas para escoamentos bifásicos e monofásicos. Foram realizados experimentos em bancada experimental utilizando seção de testes com diâmetro interno de 15,9 mm e dois metros de comprimento com fitas apresentando razões de retorcimento de 3, 4, 9, 14 e , a última correspondente ao tubo sem inserto. Os experimentos foram executados para o refrigerante R134a, velocidades mássicas entre 75 e 250 kg/m²s, e títulos de vapor entre 5 e 95% no caso de escoamentos bifásicos. Resultados foram levantados para velocidades mássicas entre 100 e 450 kg/m²s para escoamentos monofásicos. Durante os ensaios foram levantados resultados de perda de pressão e identificados subjetivamente os respectivos padrões de escoamento. Como resultado final deste estudo é proposta uma correlação para previsão da perda de pressão durante o escoamento no interior de tubos com fitas retorcidas.
Title in English
Theoretical and experimental study on flow pattern identification and pressure drop during single and two-phase flow in tubes with twisted tape inserts
Keywords in English
Convective boiling
Flow patterns
Pressure drop
Twisted-tape inserts
Abstract in English
A theoretical and experimental study on single and two-phase flow inside tubes with twisted tapes inserts is presented. Twisted tape inserts have been used for decades as a technique of heat transfer enhancement. However, their heat transfer enhancement is accompanied by an increase of the pressure drop. Therefore, understanding the pressure drop and heat transfer mechanisms is fundamental for heat exchanger designers in order to optimize these devices when using twisted-tape inserts. Based on these aspects the present study concerns single and two-phase flows inside tubes with twisted tapes. Experiments were performed in an experimental apparatus for a 15.9 mm ID and twisted tape with twist ratios of 3, 4, 9, 14 and , the last one corresponding to a plain tube without tape. For two-phase flow, experiments were conducted for R134a, mass velocities from 75 to 250 kg/m²s and vapor qualities from 5 to 95%. In case of single-phase flow, experiments were performed for mass velocities from 100 to 450 kg/m²s. The experimental campaign was focused on pressure drop and flow pattern subjective identification. Additionally an extensive literature review on flow patterns, superficial void fraction, and methodologies for prediction of the pressure drop in plain tubes with and without twisted-tape inserts during single and two-phase flow is presented. As final result, a correlation for prediction of pressure drop during flow inside tubes with twisted tape inserts is proposed.
 
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Publishing Date
2011-09-01
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • AGRAWAL, K.N., e VARMA, H.K.. Experimental study of heat transfer augmentation versus pumping power in a horizontal R1. International Journal of Refrigeration [CD-ROM], 1991, vol. 14, p. 273-281. doi: 0140-7007/91/050273-09.
  • ABERNETHY, R.B., and THOMPSON, J.W.. Handbook, Uncertainty in gas turbine measurement. Editor. Arnold, Tennessee : Arnold Engineering Development Center. Arnold Airforce Station, Tennessee 37389, 1973.
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