Thermic calculations Generalities Basic rules for cartridge Adjustment of the CCHC Mould heating example Heat loss by natural convection

 Example of calculation of power in order to heat a steel mould.    3. Necessary power to balance heat losses at the surface of the plates, of the mould and the frame of the press.

These losses are by :

• Losses by conduction through the plates' insulated surfaces  where :

l       = coefficient of conduction of the rigid insulator
= 0,65 W/m.K

e        = insulator thickness
= 0,015 m

S       = total insulated surface ( upper and lower plates)
= (0,25 x 0,4) x 2
= 0,2 m²

D    = 180°C Losses by convection of the lateral surfaces of the mould and the plates:  where :
h.D = power dispersed per m² on an upright metallic surface multiplied by the DT (180°C).
= 900W/m²

S       = upright surface of the plates and the mould
= (0,15 + 0,25) x 2 x 0,15 + (0,25 + 0,4) x 2 x 0,05 x2
= 0,25 m² Losses by convection below the upper plate:  Where :

h.DT  = 850W/m²

S       = (0,25 x 0,4) – (0,15 x 0,25)
= 0,0625 m² Losses by convection above the lower plate :  Where :

h.DT  = 1650W/m²

= 0,0625 m² Losses by radiation of every surface of the mould and the plates: Where:

a        = coefficient of emission for hardening steel slightly oxidized
= 0,7

s        = constant of Stefan-Boltzmann
= 5,675 . 10-8 W/m².K4

K       = Kelvin = degree Celsius + 273

T       = Temperature of the mould and the plates in K
= 200 + 273
= 473 K

S       = total surface of the mould and of the radiant plates
= 0,375 m² Total loss per hour:
 Conduction Fa = 1560 W Convection lateral side Fb = 225 W Convection lower side Fc = 53 W Convection upper side Fd = 103 W Radiation Fe = 745 W Total loss F3 = 2686 W © IVALDI 2004 - Home | About us | Contact us | Location | Customers | Legal informations Products : Introduction | Cartridge heaters | Coiled heaters | Band heaters | Strip heaters | Tubular heating elements | Immersion heaters | Air Heating Printed heaters | Temperature sensors | Temperature controllers | Accessories Technical data : Electrical calculation | Thermal calculation | Technical data