Tham khảo tài liệu 'the mems handbook mems applications (2nd ed) - m. gad el hak episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Micro Heat Pipes and Micro Heat Spreaders 11-11 differential and then combined with the continuity expression. The result was a first order ordinary differential equation that related the radius of curvature of the liquid-vapor interface to the axial position along the pipe. Building upon this model Peterson 1988a and Babin et al. 1990 developed a steady-state model for a trapezoidal micro heat pipe using the conventional steady-state modeling techniques outlined by Chi 1976 and described earlier in this chapter. The resulting model demonstrated that the capillary pumping pressure governed the maximum heat transport capacity of these devices. The performance limitations resulting from the models presented by Cotter 1984 and by Babin et al. 1990 were compared and indicated significant differences in the capillary limit predicted by the two models. These differences have been analyzed and found to be the result of specific assumptions made in the initial formulation of the models Peterson 1992 . A comparative analysis of these two early models was performed by Gerner et al. 1992 who indicated that the most important contributions of Babin et al. 1990 were the inclusion of the gravitational body force and the recognition of the significance of the vapor pressure losses. In addition the assumption that the pressure gradient in the liquid flow passages was similar to that occurring in Hagen-Poiseuille flow was questioned and a new scaling argument for the liquid pressure drop was presented. In this development it was assumed that the average film thickness was approximately one-fourth the hydraulic radius resulting in a modified expression for the capillary limitation. FIGURE Micro heat pipe operation. Reprinted with permission from Peterson . Swanson . and Gerner . 1996 Micro Heat Pipes in Microscale Energy Transport . Tien A. Majumdar and . Gerner eds. Taylor-Francis Publishing Co. Washington . 2006 by Taylor Francis Group LLC 11-12 MEMS .
