Calculator Inputs
Performance Chart
Example Data Table
| Case | Width (mm) | Height (mm) | Length (mm) | Channels | Mass Flow (kg/s) | Wall Temp (°C) | Heat Duty (W) |
|---|---|---|---|---|---|---|---|
| Compact Cooler A | 0.50 | 0.30 | 120 | 20 | 0.020 | 65 | 1,210 |
| Compact Cooler B | 0.40 | 0.25 | 150 | 28 | 0.018 | 70 | 1,360 |
| Electronics Sink C | 0.60 | 0.35 | 100 | 16 | 0.024 | 60 | 1,080 |
Formula Used
Hydraulic Diameter: Dh = 4A / P
Velocity: v = ṁ / (ρAtotal)
Reynolds Number: Re = ρvDh / μ
Prandtl Number: Pr = cpμ / k
Nusselt Number: Nu = 4.36 for laminar fully developed flow, or Nu = 0.023Re0.8Pr0.4 for turbulent estimation
Convection Coefficient: h = Nu·k / Dh
Overall Coefficient: U = 1 / [(1 / hη) + Rf]
Heat Duty: Q = U·A·ΔTlm
LMTD: ΔTlm = (ΔT1 - ΔT2) / ln(ΔT1/ΔT2)
This calculator estimates microchannel convection and exchanger performance using compact-channel geometry, coolant properties, and thermal driving force. It is suited for early design screening, teaching, and quick engineering comparisons.
How to Use This Calculator
- Enter channel width, height, length, and total number of channels.
- Provide coolant mass flow rate and fluid properties.
- Enter inlet, wall, and outlet temperatures.
- Set fouling factor and surface efficiency to reflect real conditions.
- Click the calculate button.
- Review Reynolds, Nusselt, convection coefficient, heat duty, and pressure drop.
- Use the chart to compare key thermal indicators.
- Export the result summary as CSV or PDF.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates hydraulic diameter, coolant velocity, Reynolds number, Prandtl number, Nusselt number, convection coefficient, heat transfer area, LMTD, heat duty, effectiveness, and pressure drop for a microchannel system.
2. Why is hydraulic diameter important in microchannels?
Hydraulic diameter converts a non-circular microchannel into an equivalent flow dimension. It directly affects Reynolds number, Nusselt number, convection coefficient, and pressure-drop predictions.
3. When does the laminar assumption apply?
It usually applies when Reynolds number stays below about 2300. Many microchannel systems operate in laminar or transitional flow because the passages are extremely small.
4. Why does the calculator use wall temperature?
Wall temperature provides the thermal driving force between the channel surface and coolant. That difference helps estimate LMTD and the resulting heat transfer rate.
5. What is fouling factor in this model?
Fouling factor represents added thermal resistance caused by deposits or surface degradation. Increasing it lowers the overall heat transfer coefficient and therefore reduces heat duty.
6. Is this suitable for detailed final design?
It is best for preliminary engineering checks and comparisons. Final design should include validated correlations, material effects, temperature-dependent properties, entrance effects, and experimental verification.
7. Why can pressure drop become very high?
Small hydraulic diameters increase flow resistance sharply. Higher velocity, longer channels, and larger friction factors also raise pressure drop in compact microchannel devices.
8. Can I use fluids other than water?
Yes. Enter the correct density, viscosity, specific heat, and thermal conductivity for the intended coolant. Reliable property inputs are critical for meaningful results.