Estudio del refrigerante R134a en estado bifásico circulando en un tubo horizontal

Blanco Fernández, Óscar (2016). Estudio del refrigerante R134a en estado bifásico circulando en un tubo horizontal. Proyecto Fin de Carrera / Trabajo Fin de Grado, E.T.S.I. Industriales (UPM).

Description

Title: Estudio del refrigerante R134a en estado bifásico circulando en un tubo horizontal
Author/s:
  • Blanco Fernández, Óscar
Contributor/s:
  • Muñoz Antón, Javier
Item Type: Final Project
Degree: Grado en Ingeniería en Tecnologías Industriales
Date: July 2016
Subjects:
Faculty: E.T.S.I. Industriales (UPM)
Department: Ingeniería Energética
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

High heat transfer rates at reasonably low temperature differences can be obtained by utilizing a boiling fluid. However, the behaviour of the heat transfer coefficient becomes much more intricate, revealing the modelling of this behaviour quite complex. Nevertheless, a good model of this twophase flow allows for an optimal design and, thus, a safer system with a higher efficiency regarding heat transfer. An extensive research has been conducted in the past decades on this topic, however, many aspects remain unexplored. The literature survey presented in this work condenses previous results in a chronological order, gradually showing new discoveries and corrections on previous models. Yielding, in the end, a wide review of the state of the art on boiling R134a inside an horizontal, small diameter tube. The purpose of this study is to perform an experimental investigation on an unexplored region, obtaining new results that may contribute for the elaboration of a more accurate model. For this end, a deep study was performed on the different aspects exhibited on the experimental results together with a comparison with the literature survey, allowing for the extrapolation of new conclusions on the topic. Experiments were conducted inside a 5mm internal diameter tube with a pressure of 5.5 bar, mass fluxes ranging from 200kg=m2s to 400kg=m2s and heat fluxes ranging from 15:8kW=m2 to 47:8kW=m2. Under these conditions, due to the high heat flux and pressure selected, the nucleate boiling contribution on the heat transfer was found significantly stronger than the convective contribution. As a result, the heat transfer coefficient presented a strong dependence on the heat flux, while the effect of mass flux was only important for higher vapour qualities, were the convective heat transfer mechanism gains strength. Deep focus was also made on the dryout region, revealing interesting behaviours regarding both the vapour quality at which dryout occurred and the HTC achieved at dryout inception. Moreover, a sharp increase of the heat transfer coefficient was found before dryout inception, this feature had been reported only once prior to this project and the experimental results presented in this work have revealed resourceful for the investigation of this new characteristic.

More information

Item ID: 43478
DC Identifier: http://oa.upm.es/43478/
OAI Identifier: oai:oa.upm.es:43478
Deposited by: Biblioteca ETSI Industriales
Deposited on: 07 Oct 2016 07:08
Last Modified: 07 Oct 2016 07:08
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