title: Heat Transfer Investigation of Air Flow in Microtubes-Part II: Scale and Axial Conduction Effects.
abstract: In this paper, the scale effects are specifically addressed by conducting experiments with air flow in different microtubes. Three stainless steel tubes of 962, 308, and 83μm inner diameter (ID) are investigated for friction factor, and the first two are investigated for heat transfer. Viscous heating effects are studied in the laminar as well as turbulent flow regimes by varying the air flow rate. The axial conduction effects in microtubes are experimentally explored for the first time by comparing the heat transfer in SS304 tube with a 910μm ID/2005μm outer diameter nickel tube specifically fabricated using an electrodeposition technique. After carefully accounting for the variable heat losses along the tube length, it is seen that the viscous heating and the axial conduction effects become more important at microscale and the present models are able to predict these effects accurately. It is concluded that neglecting these effects is the main source of discrepancies in the data reported in the earlier literature.
authors.affiliation: e-mail:  rittonylin@gmail.com.
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Lin
authors.forename: Satish G
authors.initials: SG
authors.lastname: Kandlikar
keywords: axial conduction; heat loss; heat transfer coefficient; microtubes; nickel tubes; scale effect; viscous heating
references.citation: J Heat Transfer. 2013 Mar;135(3):317041-317046
references.pmid: 23918039