Thermal EngineeringP0

Heat Transfer Calculator

Calculate heat transfer rate Q through a wall or surface using the conductive/convective heat transfer equation.

Inputs

Enter your values below

Heat Transfer Coefficient (U)*W/(m²·K)

Air free convection: 5-25; forced air: 25-250; liquid: 100-1000

Surface Area*m2

Temperature Difference (ΔT)*C

Result

Heat Transfer Rate

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Enter values and click Calculate

Formula

u × area × delta_t

Result unit: W

Q = U × A × ΔT. Heat transfer rate equals overall heat transfer coefficient × area × temperature difference. U in W/(m²·K), A in m², ΔT in K.

Introduction

The fundamental heat transfer equation Q = U·A·ΔT calculates heat flow across a surface or through a composite wall. U (overall heat transfer coefficient) combines convection on both sides and conduction through the material.

Calculation Example

A 10 m² wall with U=25 W/m²K across 20°C ΔT loses 5,000 W (5 kW).

Inputs: u=25, area=10, delta_t=20

Result: 5000 W

Engineering Applications

•Building heat loss
•Heat exchanger rating
•Insulation design
•HVAC load calc

Frequently Asked Questions

What is a typical U-value?

Insulated building wall: 0.2-0.5 W/m²K; uninsulated brick wall: 2-3; window single pane: ~5; forced-air heat exchanger: 25-100; shell-and-tube liquid-liquid: 300-1000.

How do I calculate U from k (conductivity)?

For a flat wall: U = k/L (conductivity/thickness). For composite walls: U = 1/Σ(L_i/k_i) including convection resistances on each side.

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Disclaimer: Calculations are for reference and educational purposes only. Always verify results independently for engineering design. See full disclaimer.