Experimental investigation of friction factor and heat transfer for single phase water flow in stainless steel and nickel micro-tubes.

摘要

Scope and Method of Study: This study has been conducted in order to present the design, construction and validation of a state-of-the-art experimental apparatus for the purpose of measuring pressure drop and heat transfer in micro-tubes. The data collected by this method has been compared with the previous research work and established conventional correlations for friction factor and heat transfer. All the data also have been analyzed by different flow regions (laminar-transition- turbulent).;Findings and Conclusions: The inner surface roughness and diameter play significant roles in friction factor and heat transfer of micro-tubes. A change in relative roughness of micro-tubes causes a change in the transition region of friction factor. The start and the end Reynolds numbers of transition region shift to the higher value when the stainless steel tubes diameter reduced from 1600microm to 1000microm. From 1000microm to 560microm, the start and the end Reynolds numbers of transition region for these stainless steel tubes become smaller with the decrease of diameter. For heat transfer, the large roughness dominates the heat transfer rate in stainless steel tubes. In very smooth nickel tubes, tube diameter has an effect on the heat transfer rate in the transition region. When the nickel tube diameter decreased from 1016mum to 762mum, the start of transition region of heat transfer shifted from 3207 to 3734. When the nickel tube diameter decreased to 508mum, the start Reynolds number of transition region shifted back to 3363 from 3734.