M.Sc Thesis

M.Sc StudentAbraham Devi
SubjectSteady Flow in a Heated Capillaries with a Distinct
Phase Domain
DepartmentDepartment of Mechanical Engineering
Supervisors PROFESSOR EMERITUS Gad Hetsroni (Deceased)


The heat fluxes generated by various electronic devices are continuously increasing. While in the past the heat generated by a CPU was relatively low, one would expect heat fluxes as high as 100W/cm2 in the not too distant future. This created the need for new methods of cooling such devices. Some of these methods involve cooling by means of single and/or two-phase flow in micro-channels. These developments created the need to investigate the mechanism governing flow fields in micro-channels, vis a vis those in larger conduits.

This investigation is aimed at better understanding the fluid dynamics and heat transfer that govern a single - and two-phase flows in micro-channels, and to develop the tools, which are needed to improve the cooling capabilities. This is an analytical study, where the results are compared with experimental data.

In the first analytical model, we developed a model that predicts fluid motion in conduit with irregular cross sections, such as trapezoidal or triangular. The mathematical formulation for the analysis of fully developed flow within belongs to a class of two-dimensional elliptic diffusion-type problems defined in irregular domains.

A one-dimensional model was developed in the next section to describe the two-phase flow in electronic devices with an array of equilateral micro-channels incorporated in to a silicon wafer. The results demonstrate the micro-channels heat sink may dissipate heat fluxes of the order of 106W/m2 .

Next, we investigated the conventional heat transfer in fully developed, laminar flow, in channels with an irregular cross section. We used a finite difference method and the ALGOR_FEA code.

Finally, we solved numerically the heat transfer process in the solid device.

In summary, the steady conjugate heat transfer in an irregular cross-section microchannels heat sink with hydrodynamically and thermally developing laminar flow has been analytically and numerically investigated.