Convection Heat Transfer Coefficients Equations and Calculator
Heat Transfer Engineering
Thermodynamics
Engineering Physics
Simplified relations for natural convection heat transfer coefficients for various geometries in air at atmospheric pressure for laminar flow conditions.
Convection Heat Transfer Equation and Calculator
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Geometry

W/m^{2 }· °C
(ΔT in °C, L or D in mm) 
Btu/h · ft^{2} 
Vertical Plate or Cylinder

h_{conv} = 1.42 (ΔT / L)^{0.25}

h_{conv} = 0.29 (ΔT / L)^{0.25}

Horizontal Cylinder

h_{conv} = 1.32 (ΔT / L)^{0.25}
^{Open}

h_{conv} = 0.27 (ΔT / L)^{0.25}
^{Open}

Hot Surface Facing Up

Horizontal plate (L = 4A/p, ^{Open}

Horizontal plate (L = 4A/p, h_{conv} = 0.27 (ΔT / L)^{0.25} ^{Open}

Hot Surface Facing Down

Horizontal plate (L = 4A/p, where A is surface area and p is perimeter h_{conv} = 0.59 (ΔT / L)^{0.25}
Open

Horizontal plate (L = 4A/p,
where A is surface area and p is perimeter h_{conv} = 0.12 (ΔT / L)^{0.25}

Components on Circuit Board

h_{conv} = 2.44 (ΔT / L)^{0.25}

h_{conv} = 0.50 (ΔT / L)^{0.25}

Small Components, Wires in Free Air

h_{conv} =3.53 (ΔT / L)^{0.25}

h_{conv} = 0.72 (ΔT / L)^{0.25}

Sphere

h_{conv} = 1.92 (ΔT / L)^{0.25}
Open

h_{conv} = 0.39 (ΔT / L)^{0.25}
Open

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