Date

2013

Author

Altınöz, Mesru

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This thesis aims to experimentally investigate pressure drop and heat transfer characteristics of single phase water flow in rectangular minichannels. The small channels are an area of interest in heat transfer field since 1970’s owing to their enhanced heat transfer characteristics. However, the heat transfer and pressure drop characteristics of these channels are not fully established as there is a wide number of studies in literature showing inconsistent results with each other. In order to investigate this matter further, an experimental set-up is designed and constructed. Laminar region is considered during the experiments because the flow inside minichannels is generally laminar due to pressure drop considerations. Additionally, constant heat flux condition is selected to stimulate cooling with internal flow in minichannels. In the scope of this study, three minichannels with different hydraulic and different port numbers diameters were examined. The results are presented in terms of Poiseulle numbers and average Nusselt numbers. Generally, average Nusselt number results and Poiseuille number results showed a good agreement with constant Po theory and constant Nu theory excluding developing effects and experimental errors. On the other hand, developing effects are found to be increasing as hydraulic diameter decreases. Similarly, constant Nu value showed a decrease with increasing hydraulic diameter. The small scale heat transfer correlations and conventional heat transfer correlations are compared with experimental resuts. The conventional correlations followed the trend of results precisely but predictions of correlations overestimated most of the results. When a correction factor is applied, several correlations predicted almost all results within 11%. Small scale correlations showed agreement with a few results but mostly overestimated the Nu results. No early transition were observed for Reynolds number smaller than 1800. No signs of Poiseuille number or average Nusselt number dependency on Reynolds number were observed considering developing effects and uncertainty values.

Subject Keywords

Heat, Heat, Laminar flow., Single-phase flow., Fluid dynamics.

URI

http://etd.lib.metu.edu.tr/upload/12616710/index.pdf
https://hdl.handle.net/11511/23218

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Graduate School of Natural and Applied Sciences, Thesis