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Pressure Drop in Microchannel Device: Parametric Study using Empirical Results

This study analyzes the estimation of pressure drop in a microchannel device through empirical results. The effect of mass flow rate, dimensions, and number of microchannels on pressure drop is investigated. Conclusions and suggestions for reducing pressure drop are provided.

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Pressure Drop in Microchannel Device: Parametric Study using Empirical Results

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  1. CFD-2011-03-GTK NA-62(Micro channel) Parametric study using Empirical ResultsJune 30th 2011Bdg 298Enrico Da Riva,Vinod Singh Rao 30th June 2011

  2. Estimation of the pressure drop in the Microchannel device PDdevice = PDmanifold + PDmicrochannels+ PDpipe where PD : Pressure Drop 30thJune 2011

  3. Estimation of pressure drop in manifold The pressure drop in a fluid flow is proportional to the dynamic pressure as given by the relation:The value of K(=3*2.1) is chosen according to the experimental data provided @15°C to obtain the pressure drop @ -25°C 30th June 2011

  4. Estimation of pressure drop in the microchannel The pressure drop across the microchannel and the inlet-outlet pipe is calculated using churchill correlations flow in tubes.where Re : Reynolds number f: friction factor where L: Length w: Mass flow rate D: hydraulic diameter 30th June 2011

  5. Dimensions and flow regime in the microchannels Number of microchannels: 300Length of microchannel: 40mm Depth of microchannel: 100µm Width of channel: 100µm Mass flow rate:7 g/sDensity @ 15°C :1700.85 Kg/m3Kinematic viscosity @ 15°C : .425 cSt Inlet velocity: 1.75 m/s Inlet Reynolds number: 410.99 Density @ -25°C :1805.25 Kg/m3Kinematic viscosity @ -25°C : .8 cSt Inlet velocity:1.65 m/s Inlet Reynolds number:205.71 » Flow is laminar in the microchannels 30th June 2011

  6. Effect of the mass flow rate on Pressure drop across the microchannels The pressure drop varies linearly with the mass flow rate in the laminar region.The variation of the kinematic viscosity with temperature also has a huge effect on the pressure drop . The pressure drop at a lower temperature is quite high as compared to the higher temperature with same mass flow rate. 30th June 2011

  7. Effect of the microchannel dimension/Number of microchannels on Pressure drop across the microchannels Length of microchannel: 40mmDepth of microchannel: 100µmFin-width: 100µm Mass flow rate: 7 g/secIncreasing the number of channels with fin-width constant increases the pressure drop exponentially as the hydraulic diameter decreases quite fast. 30th June 2011

  8. Effect of the microchannel dimension/Number of microchannels on Pressure drop across the microchannels Length of microchannel: 40mm Depth of mircochannel: 100µmMicrochannel-width:100µm Mass flow rate: 7 g/sec Increasing the number of channels with channel width constant decreases the pressure drop as there is smaller mass flow rate in each channel. 30thJune 2011

  9. Effect of the mass flow rate on Pressure drop across the manifold Inlet mass flow rate: 7g/sInlet diameter: 1.4 mmManifold cross section: 280µm X 1.7mm Density @ 15°C :1700.85 Kg/m3Kinematic viscosity @ 15°C : .425 cSt Inlet velocity: 2.67 m/s Inlet Reynolds number: 8806.94 Manifold velocity: 8.64 m/s  Manifold Reynolds number: 9781.55Density @ -25°C :1805.25 Kg/m3Kinematic viscosity @ -25°C : .8 cSt Inlet velocity:2.51 m/s Inlet Reynolds number: 4408.11 Manifold velocity: 8.14 m/s  Manifold Reynolds number: 4895.93Flow is turbulent in the manifold 30th June 2011

  10. Effect of the mass flow rate on Pressure drop across the manifold Dimensions:Inlet diameter of the pipe: 1.4 mmDepth of the manifold: 280 µmWidth of the manifold: 1.7mmTemperature: 15°C 30th June 2011

  11. Effect of the mass flow rate on Pressure drop across the manifold. 30th June 2011

  12. Effect of the mass flow rate on Pressure drop across the manifold. With decrease in temperature , the pressure drop in microchannel become more prominent but for the current operating point, manifold pressure drop is quite important. 30th June 2011

  13. Effect of the mass flow rate on Pressure drop across the inlet-outlet pipes. 30th June 2011

  14. Effect of the mass flow rate on Pressure drop across the Pipes. The change in the steepness of the curve may be due to the transition from laminar region to turbulent flow. 30th June 2011

  15. Conclusions & Suggestions 1.) The pressure drop in the manifold would be dominant at the design temperature and design mass flow rate.2.) The problem is due to the small cross section of the manifold.3.) Before looking at the microchannels, we must work on the manifold.4.) Temperature has a strong influence on the pressure drop in the microchannel, but this is not so important with the present design since the dominant pressure drop is in the manifold.5.) Using multiple inlet-outlet system to reduce pressure drop in the manifold. 30th June 2011

  16. Pressure drop with dual inlet-outlet Working fluid perflourohexane @Temperature -25 °CMass flow: 7 g/s or 2*3.5 g/s Manifold velocity:4.07 m/s Inlet velocity: 1.25 m/s Manifold Reynolds number: 2447Inlet Reynolds number:2204 30th June 2011

  17. Pressure drop with dual inlet-outlet The required pressure drop for mass flow rate of 7 g/s is about 4 bar 30th June 2011

  18. Heat transfer coefficient For laminar flow  Nusselt number : 3.2Hydraulic diameter of channels : 100 µmThermal conductivity of Perflourohexane @ -25 °C: .06275 W/(m-k) Heat transfer coefficient (Perflourohexane):2008 W/(m2 k) 30th June 2011

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