Engineering

Introduction:

Micro Channel GeometryOver the last decade, micro machining technology has been increasingly used for the development of highly efficient cooling devices called heat sink because of its undeniable advantages such as less coolant demands and small dimensions. One of the most important micromachining technologies is micro channels. Hence, the study of fluid flow and heat transfer in micro channels which are two essential parts of such devices, have attracted more attentions with broad applications in both engineering and medical problems.

Flow disruption can be achieved through passive surface modifications, such as, shape of channel, dimple surfaces, ribs, cavities, groove structures, etc. the unique characteristics of micro channel heat sinks (small length scale, conductive substrate, abrupt contraction/ expansion at the entrance/ exit and high pressure drop) give rise to conditions that are quite different from those conventional channel.

 

Geometry Creation:

Geometry of Micro channel is created in Solid works using Feature workbench. The step. file of Micro channel is used for further processing. The three dimensional model of micro channel is shown below in figure1 and figure 2 showcase the cut section detail view. The total length of the model is 10 mm and height is 0.35 mm.

Microchannel Model

 

section view micro

Meshing:

The saved geometry in step format is imported in ICEM CFD. There After name selection has been done i.e. inlet, outlet, bottom, and micro-channel.

Unstructured Hexa Core Mesh parameters is given by using Cartesian technique in both solid and fluid domain. Total elements is generated 326576, in fluid domain 24871 elements and solid 219425 elements. A grid independent test was done using water to find the effect of mesh size on the results.

Microchannel Meshed Model

Fluent Setup:

With water used as working fluid, the numerical model for fluid flow and heat transfer in the micro channel is developed under the following assumptions.

(1) Steady three-dimensional fluid flow and heat transfer.

(2) Laminar and incompressible.

(3) Piecewise-linear dynamic viscosity of water temperature using the data shown in Table 1.

(4) Viscous dissipation is considered.

The Irreversible process by means of which the work done by a fluid on adjacent layer due to the action of shear forces is transformed into heat is defined as viscous dissipation. Viscous dissipation or viscous heating is a phenomenon that usually is neglected in macro-scale geometries but in micro scale the viscous dissipation effect has significant impress on results.

Table 1:

Dynamic viscosities of water temperature:                     

T (K) 293 303 313 323
µ (Pa s) 0.001004 0.0008015 0.0006533 0.0005494
T (K) 333 343 353 363
 µ(Pa s) 0.0004699 0.0004061 0.0003551 0.0003149

Results:

Temperature Contour of Microchannel

 

Velocity Contour of Microchannel

 

Temperature Contour at mid section of Microchannel

 

Velocity Contour of Microchannel

 

Graph of Microchannel

 

Note: - Three-dimensional CFD simulations of laminar water flow and heat transfer in micro channels by the same procedure discussed above. For different geometries further investigation can be carried out.