DEPARTMENT OF MECHANICAL ENGINEERING K.I.E.T, GHAZIABAD NUMERICAL ANALYSIS OF FLUID FLOW AND HEAT TRANSFER IN MICROCHANNEL UNDER THE GUIDANCE OF Mr. Deepak Kumar Singh PRESENTED BY- PARUL SINGH( ) PRESHITA JAIN ( ) VIVEK SINGH ( ) ANURAG SHARMA( )

TABLE OF CONTENT Objective of Project Geometry Details Computational Fluid Dynamics Calculations Result Conclusion Work Plan Tentative Date for the completion of Project

OBJECTIVE To investigate hydrodynamic & thermal characteristics of micro-channel through Computational Fluid Dynamic modeling & simulation. Parameter sensitivity study of micro-channel.  Input parameters: (Reynolds‘ Number, Cross-section, Waviness)  Output parameters: (Friction loses, Convective heat transfer coefficient, Temperature)

Rectangular size410*200 mm² Channel geometryWavy Rectangular micro- channel Micro-channel length0.01 m Mesh sizing 2 x 10ˉ ⁵ µm Material usedSilicon LiquidWater-liquid Reynolds' Number GEOMETRIC SPECIFICATIONS

Based on the previous researches that have been made so far, we have confined our work to the micro- channel in the wavy structure of varying relative wavy amplitude with constant length of the micro- channel at various Reynolds’ number. Values of various relative wavy amplitude (γ) of the channels are 0.05, 0.075, 0.1, & Then we’d be comparing our result with that of the straight channel of similar dimensions.

GEOMETRY Wavy line equation y=A cos (2πx/L) where y= channel relative wavy amplitude A= channel’s wavy amplitude L= channel wavelength = mm x= x co-ordinate

DIMENSIONLESS PARAMETERS Dimensionless channel width (α e ): α e = S c /L where α e = 0.1 S c = Spacing between two wavy planes Cross-section aspect ratio (β): β = S c /H where β = 1/3 H= Depth of channel

Relative wavy amplitude (γ): γ= A/L where γ varies as 0.05,0.075,0.1, Number of wavy unit (n)= 12 Total length of channel is fixed & equals to 0.01 m and is given by: “n x L”

VARIOUS GEOMETRY Straight Rectangular channel Wavy channel with γ= 0.05 Wavy channel with γ= 0.075

VARIOUS GEOMETRY Wavy channel with γ= 0.1 Wavy channel with γ= 0.125

MESHING

SETUP & SOLUTION Models : Energy Model Materials used: Fluid: Water-liquid PROPERTIES: Density kg/m³ Specific Heat-4182 J/kg-K Thermal Conductivity-0.6 W/m-K Viscosity kg/m-s Channel material: Silicon PROPERTIES: Density-2570 kg/m³ Specific Heat-710 J/kg-K Thermal Conductivity-149 W/m-K

BOUNDARY CONDITIONS INLET: Velocity Inlet (Based on Reynolds Number) Temperature at inlet = 300 K WALL: Constant Wall Heat Flux (direction –from wall surface to fluid) = 50 W/cm² Stationary Wall No-Slip boundary condition at wall surface OUTLET: Outflow boundary condition at channel outlet. Reynolds’ number Velocity(m/s)

SOLVER SETTINGS PRESSURE-VELOCITY COUPLING:- Pressure-velocity coupling refers to the numerical algorithm which uses a combination of continuity and momentum equations to derive an equation for pressure (or pressure correction) when using the pressure-based solver. Four algorithms are available in FLUENT:  Semi-Implicit Method for Pressure-Linked Equations (SIMPLE)  This is a guess and correct procedure for the calculation of pressure.  SIMPLE-Consistent (SIMPLEC)  Allows faster convergence for simple problems (e.g., laminar flows with no physical models employed).  Pressure-Implicit with Splitting of Operators (PISO) o It is useful for unsteady flow problems. The steady state PISO algorithm adds an extra correction step to SIMPLE to enhance its performance per iteration. Coupled

SOLVER SETTINGS INTERPOLATION METHODS (GRADIENTS) :- Gradients of solution variables are required in order to evaluate diffusive fluxes, velocity derivatives, and for higher-order discretization schemes. The gradients of solution variables at cell centers can be determined using three approaches:  Green-Gauss Cell-Based – The default method; solution may have false diffusion (smearing of the solution fields).  Green-Gauss Node-Based – More accurate; minimizes false diffusion.  Least-Squares Cell-Based – Recommended for polyhedral meshes; has the same accuracy and properties as Node-based Gradients. Gradients of solution variables at faces are computed using multi-dimensional Taylor series expansion.

SOLVER SETTINGS INTERPOLATION METHODS FOR PRESSURE :-  Standard – The default scheme; reduced accuracy for flows exhibiting large surface-normal pressure gradients near boundaries (but should not be used when steep pressure changes are present in the flow – PRESTO! scheme should be used instead.)  PRESTO! – Use for highly swirling flows, flows involving steep pressure gradients (porous media, fan model, etc.), or in strongly curved domains.  Linear – Use when other options result in convergence difficulties or unphysical behavior.  Second-Order – Use for compressible flows; not to be used with porous media, jump, fans, etc.  Body Force Weighted – Use when body forces are large.

SOLVER SETTINGS DISCRETIZATION:- Field variables (stored at cell centers) must be interpolated to the faces of the control volumes. Interpolation schemes for the convection term:  First-Order Upwind – Easiest to converge, only first-order accurate.  Power Law – More accurate for one-dimensional problems since it attempts to represent the exact solution more closely.  Second-Order Upwind – Uses larger stencils for 2nd order accuracy, essential with tri/tetra mesh or when flow is not aligned with grid; convergence may be slower.  Monotone Upstream-Centered Schemes for Conservation Laws (MUSCL) – Locally 3rd order convection discretization scheme for unstructured meshes; more accurate in predicting secondary flows, vortices, forces, etc.  Quadratic Upwind Interpolation (QUICK) – Applies to quad/hex and hybrid meshes, useful for rotating/swirling flows, 3rd-order accurate on uniform mesh.

Variation of Nusselt number at different relative wavy amplitude (γ) with varying Reynolds’ number

Values of Nusselt number of wavy channel at different relative wavy amplitude (γ) and straight channel with varying Reynolds’ number γ STRAIGHT CHANNEL ReNu

Heat transfer enhancement factor for various wavy channels & a straight line channel at various Reynolds’number

y ReE Nu Values of Heat transfer enhancement factor of wavy channel at different relative wavy amplitude (γ) with varying Reynolds’ number

Temperature variation of fluid in wavy channel with different relative wavy amplitude (γ) and straight channel at various Reynolds’ number

Values of average temperature of fluid in wavy channel with different relative wavy amplitude (γ) & straight channel at various Reynolds’ number y STRAIGHT CHANNEL Retemp

Variation of Pressure drop penalty factor( E f ) with varying Reynolds’ number at various relative wavy amplitude (γ =0.05, 0.075, 0.1, 0.125)

Values of Pressure drop penalty factor( E f ) with varying Reynolds’ number at various relative wavy amplitude (γ =0.05, 0.075, 0.1, 0.125) y Re PRESSURE DROP PANELTY FACTOR

TEMPERATURE PROFILE

VELOCITY PROFILE

CONCLUSION The result of the above graph shows that the heat transfer coefficient increases with the increasing Reynolds’ number. The heat transfer coefficient greatly increases with the increasing wavy amplitude of the micro-channel. It can also be observed that the temperature drop in the fluid while its flow through the micro-channel, increases with the increase in the waviness of the micro-channel and the Reynolds’ number.

WORKPLAN Month / Activity SeptemberOctoberNovemberDecemberJanuaryFebruaryMarchApril Literature Survey Software Training Designing the model Data collection Validation Result & Comparison Report Submission

DATE OF SUBMISSON The project will be submitted to the concerned authorities on April 10, 2013.