Title

Single-phase forced convective heat transfer in microtubes

Date of Award

2005

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Mechanical Engineering

First Committee Member

Sadik Kakac, Committee Chair

Abstract

With the increase of integrated circuit density and power dissipation of microelectronic devices, it is becoming more necessary to employ effective cooling devices and cooling methods to maintain the operating temperature of electronic components to a safe level. The tremendous progresses in micro scale industry have been made over the past two decades, such as microelectronics, micro scale sensing and measuring tools, micro heat exchangers, micro motors. Heat dissipation from these micro devices has become an important field. But microscale heat transfer is very different from macro phenomena.In this thesis, the mathematical model of single-phase forced convective heat transfer for steady state, laminar, hydrodynamically developed flow in microtubes with uniform temperature, linear wall temperature and uniform heat flux boundary conditions is formulated and solved by the numerical methods. Temperature jump and velocity slip condition and viscous heating are included. The complete analysis for all parameters, like Knudsen number, Prandtl number, Brinkman number, is made.The solution is verified for the cases where viscous heating is neglected. For these three cases, with a given Brinkman number, at specified axial lengths, the viscous effects are presented for the thermal developing range. Also, the viscous heating is investigated for all the cases where the fluid is being heated or cooled. Knudsen number analysis has shown that, as the Knudsen number increases, the Nusselt number decreases because of the increase of the temperature jump. Furthermore, as we increase the Prandtl number, the temperature jump diminishes, which gives a rise to the Nusselt number. On the contrary, without considering temperature jump, the Nusselt number increases as the Knudsen increases because of the increase of the velocity of slip. The fully-developed values of Nusselt number for linear wall temperature boundary condition approaches the corresponding values under uniform heat flux.

Keywords

Engineering, Mechanical

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3185021