The Film Coefficient Calculator helps engineers, HVAC designers, and heat transfer specialists determine the convective heat transfer coefficient for fluids flowing over surfaces. This value, known as the film coefficient, is critical for designing heat exchangers, insulating walls, and predicting energy losses in pipes and equipment. Knowing this coefficient makes it possible to calculate how effectively heat moves from a solid surface into a fluid (or vice versa). This calculator belongs to the Heat Transfer and Thermal Engineering Calculator category and is widely used in mechanical, chemical, and process engineering.
formula of Film Coefficient Calculator
Film Coefficient (h) = q / (A × ΔT)
Where:
h is the film coefficient or convective heat transfer coefficient (W/m²·K)
q is the heat transfer rate (watts, W)
A is the surface area through which heat is transferred (square meters, m²)
ΔT is the temperature difference between the solid surface and the fluid (°C or K)
If you know the heat flux directly instead of total heat flow:
h = Heat Flux / ΔT
Where:
Heat Flux is the heat transfer rate per unit area (W/m²)
For fluid flow over a flat plate (using empirical correlations):
h = Nu × k / L
Where:
Nu is the Nusselt number (dimensionless)
k is the thermal conductivity of the fluid (W/m·K)
L is the characteristic length (m)
These formulas provide practical ways to calculate the film coefficient for different heat transfer conditions.
Common Film Coefficient Reference Table
This table shows typical film coefficient values for various fluids and conditions. Use these as a quick guide or to cross-check your calculations.Fluid/Condition Approx. Film Coefficient (W/m²·K) Air, free convection 5–25 Air, forced convection 25–250 Water, free convection 50–1,000 Water, forced convection 500–10,000 Condensation of steam 5,000–25,000 Boiling water 2,500–100,000
These ranges help engineers make reasonable assumptions during early design stages.
Example of Film Coefficient Calculator
Let’s check a practical example step by step.
Suppose hot water flows inside a pipe and transfers heat to the pipe wall.
Given:
Heat transfer rate (q) = 1,500 W
Surface area (A) = 0.5 m²
Temperature difference (ΔT) between the pipe wall and water = 15°C
- Use the formula:
h = q / (A × ΔT) - Plug in the numbers:
h = 1,500 / (0.5 × 15)
h = 1,500 / 7.5
h = 200 W/m²·K
So, the film coefficient is 200 W/m²·K, which is within the expected range for forced convection in water.
Most Common FAQs
The film coefficient shows how easily heat transfers between a surface and a fluid. It helps design heat exchangers, boilers, radiators, and insulation. A low coefficient means poor heat transfer; a high value means heat moves quickly.
It depends on fluid type, flow speed, surface roughness, fluid temperature, and whether the fluid moves naturally (free convection) or is forced by a pump or fan.
Yes. The calculator works for air, steam, water, oil, and other fluids. Just use the correct values for heat rate, area, and temperature difference, or use empirical Nusselt number equations if you know flow conditions.