Model passive cooling with clear engineering inputs. Review fin spacing, effective area, and temperature rise. Get useful design estimates for compact silent electronic systems.
| Heat Load (W) | Ambient (°C) | Max Sink Temp (°C) | Base (mm) | Fins | Fin Height (mm) | Fin Thickness (mm) | Spacing (mm) | Limit Dissipation (W) | Predicted Sink Temp (°C) |
|---|---|---|---|---|---|---|---|---|---|
| 35 | 25 | 70 | 120 × 100 | 10 | 35 | 2 | 8.89 | 34.07 | 71.00 |
Fin spacing: s = (W − N × tf) / (N − 1)
Fin area: Afin = N × [(2 × H × L) + (tf × L)]
Exposed base area: Abase = (W − N × tf) × L
Average Nusselt number: Nu = [0.825 + 0.387 × Ra^(1/6) / (1 + (0.492 / Pr)^(9/16))^(8/27)]²
Convection coefficient: h = Nu × kair / H
Fin efficiency: ηf = tanh(mH) / (mH), where m = √[2h / (ks × tf)]
Heat dissipation: Q = h × (Abase + ηf × Afin) × ΔT
Thermal resistance: Rθ = ΔT / Q
This model uses a still air natural convection estimate. The orientation selector applies a simple correction factor for non vertical mounting. Use testing for final validation.
A natural convection heat sink calculator helps you estimate passive cooling performance without forced airflow. It is useful for electronics, LED modules, power devices, and embedded hardware. This tool focuses on still air conditions. It estimates convection coefficient, fin efficiency, effective surface area, thermal resistance, and heat dissipation capacity. Those values help you judge whether a heat sink can keep a device within a safe temperature limit.
Natural convection moves heat by buoyancy. Warm air near the sink rises. Cooler air replaces it. This cycle removes heat without fans. That makes passive cooling quiet, simple, and reliable. It also avoids dust buildup and moving parts. Designers often use natural convection heat sinks in sealed enclosures, industrial controls, lighting fixtures, telecom equipment, and low maintenance products.
The calculator uses heat load, ambient temperature, maximum sink temperature, sink length, sink width, fin count, fin thickness, fin height, and material conductivity. These inputs affect exposed area and thermal resistance. The temperature difference sets the driving force for heat transfer. Fin geometry controls area and spacing. Material conductivity changes fin efficiency. Together, these variables define how well the sink spreads and releases heat.
The results show estimated heat transfer coefficient, Rayleigh number, fin spacing, total area, effective area, estimated thermal resistance, and maximum dissipated heat. You can compare estimated dissipation against the required heat load. A lower thermal resistance usually means better cooling. If the result is too weak, increase fin height, improve spacing, enlarge the base, or allow a higher surface temperature. This calculator is best for early design work. Final validation should still include testing, mounting details, enclosure effects, and real orientation.
Use this calculator during concept design, component selection, and thermal tradeoff studies. It quickly shows whether a passive sink is realistic for your heat source. It also helps compare aluminum and copper choices, check spacing penalties, and estimate the benefit of larger fins before building a prototype.
Natural convection removes heat with buoyancy driven airflow. Warm air rises from the fins and cooler air replaces it. No fan is required, so the system stays quiet and simple.
Yes. Vertical fins usually perform better in still air because rising air can travel upward through the channels. Horizontal mounting can reduce flow strength and lower heat dissipation.
Not always. More fins add area, but they also reduce spacing. If gaps become too narrow, airflow weakens. Good passive design balances surface area and channel spacing.
Aluminum is common because it is light, affordable, and easy to machine. Copper conducts heat better, but it is heavier and more expensive.
This calculator is best for early design estimates. Real performance also depends on enclosure shape, device mounting, surface finish, contact resistance, and nearby heat sources.
A sealed box often traps warm air, which reduces natural convection. Use enclosure testing or detailed simulation when the sink will operate in a confined space.
No. Thermal interface material improves heat transfer from the device into the base, but it does not replace the need for enough fin area and suitable airflow paths.
Increase base area, raise fin height, adjust fin spacing, lower the heat load, or allow a higher safe sink temperature. Any of those can improve passive cooling capacity.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.