30 th June 20111Enrico Da Riva, V. Rao Parametric study using Empirical Results June 30 th 2011 Bdg 298 Enrico Da Riva,Vinod Singh Rao CFD GTK NA-62(Micro channel)

30 th June 20112Enrico Da Riva, V. Rao PD device = PD manifold + PD microchannels + PD pipe w here PD : Pressure Drop Estimation of the pressure drop in the Microchannel device

30 th June 20113Enrico Da Riva, V. Rao 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 to obtain the pressure -25°C Estimation of pressure drop in manifold

30 th June 20114Enrico Da Riva, V. Rao 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 Estimation of pressure drop in the microchannel

30 th June 20115Enrico Da Riva, V. Rao Number of microchannels: 300 Length of microchannel: 40mm Depth of microchannel: 100µm Width of channel: 100µm Mass flow rate:7 g/s 15°C : Kg/m 3 Kinematic 15°C :.425 cSt  Inlet velocity: 1.75 m/s  Inlet Reynolds number: °C : Kg/m 3 Kinematic -25°C :.8 cSt  Inlet velocity:1.65 m/s  Inlet Reynolds number: » Flow is laminar in the microchannels Dimensions and flow regime in the microchannels

30 th June 20116Enrico Da Riva, V. Rao 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. Effect of the mass flow rate on Pressure drop across the microchannels

30 th June 20117Enrico Da Riva, V. Rao Length of microchannel: 40mm Depth of microchannel: 100µm Fin-width: 100µm Mass flow rate: 7 g/sec Increasing the number of channels with fin-width constant increases the pressure drop exponentially as the hydraulic diameter decreases quite fast. Effect of the microchannel dimension/Number of microchannels on Pressure drop across the microchannels

30 th June 20118Enrico Da Riva, V. Rao Length of microchannel: 40mm Depth of mircochannel: 100µm Microchannel-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. Effect of the microchannel dimension/Number of microchannels on Pressure drop across the microchannels

30 th June 20119Enrico Da Riva, V. Rao Inlet mass flow rate: 7g/s Inlet diameter: 1.4 mm Manifold cross section: 280µm X 1.7mm 15°C : Kg/m 3 Kinematic 15°C :.425 cSt  Inlet velocity: 2.67 m/s  Inlet Reynolds number:  Manifold velocity: 8.64 m/s  Manifold Reynolds number: °C : Kg/m 3 Kinematic -25°C :.8 cSt  Inlet velocity:2.51 m/s  Inlet Reynolds number:  Manifold velocity: 8.14 m/s  Manifold Reynolds number:  Flow is turbulent in the manifold Effect of the mass flow rate on Pressure drop across the manifold

30 th June Enrico Da Riva, V. Rao Dimensions: Inlet diameter of the pipe: 1.4 mm Depth of the manifold: 280 µm Width of the manifold: 1.7mm Temperature: 15°C Effect of the mass flow rate on Pressure drop across the manifold

30 th June Enrico Da Riva, V. Rao Effect of the mass flow rate on Pressure drop across the manifold.

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

30 th June Enrico Da Riva, V. Rao Effect of the mass flow rate on Pressure drop across the inlet-outlet pipes.

30 th June Enrico Da Riva, V. Rao The change in the steepness of the curve may be due to the transition from laminar region to turbulent flow. Effect of the mass flow rate on Pressure drop across the Pipes.

30 th June Enrico Da Riva, V. Rao 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. Conclusions & Suggestions

30 th June Enrico Da Riva, V. Rao Working fluid -25 °C Mass 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: 2447 Inlet Reynolds number:2204 Pressure drop with dual inlet-outlet

30 th June Enrico Da Riva, V. Rao The required pressure drop for mass flow rate of 7 g/s is about 4 bar Pressure drop with dual inlet-outlet

30 th June Enrico Da Riva, V. Rao For laminar flow  Nusselt number : 3.2 Hydraulic diameter of channels : 100 µm Thermal conductivity of -25 °C: W/(m-k) Heat transfer coefficient (Perflourohexane):2008 W/(m 2 k) Heat transfer coefficient