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ABSTRACT
A numerical simulation is performed to investigate the characteristics of flow and heat transfer in microchannels with cavities and fins. Nine microchannels with various shaped cavities and fins are presented and compared to the smooth microchannel. The effect of cavity and fin shapes on the flow field and temperature field is analyzed. Results show that the presence of cavity and fin can increase the heat transfer area, intensify mainstream disturbance, and induce chaotic advection, which result in obvious heat transfer enhancement. The shape of cavity or fin has a great influence on the hydrodynamic and thermal performance for such micro heat sinks. Based on the performance evaluation criterion (PEC), the overall performance of the microchannel is evaluated. The combination of cavities and fins leads to lower bottom temperature, lower net temperature gradient of fluid, and better heat transfer performance, which has the potential to meet the increased heat removal requirement.
Nomenclature
| Acon | = | convection heat transfer area, m2 |
| Afilm | = | heating area, m2 |
| AR | = | aspect ratio |
| cp | = | specific heat capacity, J/(kg·K) |
| Dh | = | hydrodynamic diameter, m |
| f | = | friction factor |
| h | = | heat transfer coefficient, W/(m2·K) |
| H | = | height of the microchannel, m |
| Hz | = | height of the computational domain, m |
| K | = | Hagenbach’s factor |
| L | = | length of the microchannel, m |
| L1 | = | expansion segment length of triangular cavity, m |
| L2 | = | contraction segment length of triangular cavity, m |
| L3 | = | constant cross-section length between cavities, m |
| L4 | = | length of incline section of trapezoidal cavity, m |
| L5 | = | constant cross-section length of trapezoidal cavity, m |
| Lr | = | length of the rectangular fin, m |
| Nu | = | Nusselt number |
| P | = | pressure, Pa |
| Δp | = | pressure drop, Pa |
| Po | = | Poiseuille number |
| Pr | = | Prandtl number |
| q | = | heat flux, W/m2 |
| Re | = | Reynolds number |
| T | = | temperature, K |
| ΔT | = | temperature difference, K |
| |∇Tf| | = | net temperature gradient of fluid, K/m |
| u | = | velocity component in the x direction, m/s |
| = | velocity vector, m/s | |
| W | = | width of the rectangular channel, m |
| Wc | = | cavity region width, m |
| Wr | = | fin width, m |
| Wz | = | width of the computational domain, m |
| εTw | = | temperature control effectiveness |
| λ | = | thermal conductivity, W/(m·K) |
| μ | = | dynamic viscosity, Pa·s |
| ρ | = | density, kg/m3 |
| Subscripts | = | |
| app | = | apparent |
| ave | = | average |
| f | = | fluid |
| fd | = | fully developed |
| in | = | inlet |
| m | = | mean |
| out | = | outlet |
| s | = | solid |
| w | = | wall |
| 0 | = | smooth microchannel |
Nomenclature
| Acon | = | convection heat transfer area, m2 |
| Afilm | = | heating area, m2 |
| AR | = | aspect ratio |
| cp | = | specific heat capacity, J/(kg·K) |
| Dh | = | hydrodynamic diameter, m |
| f | = | friction factor |
| h | = | heat transfer coefficient, W/(m2·K) |
| H | = | height of the microchannel, m |
| Hz | = | height of the computational domain, m |
| K | = | Hagenbach’s factor |
| L | = | length of the microchannel, m |
| L1 | = | expansion segment length of triangular cavity, m |
| L2 | = | contraction segment length of triangular cavity, m |
| L3 | = | constant cross-section length between cavities, m |
| L4 | = | length of incline section of trapezoidal cavity, m |
| L5 | = | constant cross-section length of trapezoidal cavity, m |
| Lr | = | length of the rectangular fin, m |
| Nu | = | Nusselt number |
| P | = | pressure, Pa |
| Δp | = | pressure drop, Pa |
| Po | = | Poiseuille number |
| Pr | = | Prandtl number |
| q | = | heat flux, W/m2 |
| Re | = | Reynolds number |
| T | = | temperature, K |
| ΔT | = | temperature difference, K |
| |∇Tf| | = | net temperature gradient of fluid, K/m |
| u | = | velocity component in the x direction, m/s |
| = | velocity vector, m/s | |
| W | = | width of the rectangular channel, m |
| Wc | = | cavity region width, m |
| Wr | = | fin width, m |
| Wz | = | width of the computational domain, m |
| εTw | = | temperature control effectiveness |
| λ | = | thermal conductivity, W/(m·K) |
| μ | = | dynamic viscosity, Pa·s |
| ρ | = | density, kg/m3 |
| Subscripts | = | |
| app | = | apparent |
| ave | = | average |
| f | = | fluid |
| fd | = | fully developed |
| in | = | inlet |
| m | = | mean |
| out | = | outlet |
| s | = | solid |
| w | = | wall |
| 0 | = | smooth microchannel |