### CALCULATION OF THE POWER REQUIRED FOR HEATING A VOLUME OF LIQUID

The power to be installed in order to raise the temperature over a given time of a volume of liquid contained in a tank is the result of 2 calculations: The calculation of the power to raise the temperature of the liquid (Pch) and the calculation of the heat loss (Pth).

Power to be installed (kW) = Heating power (Pch) + Heat loss (Pth)

1 / Calculation of the power required to raise the temperature of a volume of liquid:

– Heating power : Pch (kW)

– Weight of liquid : M (kg)

– Specific heat of liquid : Cp (kcal/kg×°C)

– Starting temperature : t1 (°C)

– Required end temperature : t2 (°C)

– Heating time : T (h)

1,2 : Safety coefficient linked to our manufacturing tolerances and variations in network power

Pch = (M × Cp × (t2 − t1) × 1,2) ÷ (860 × T) a/ Calculation of the mass of liquid to be heated :

– Weight of liquid : M (kg)

– Volume of liquid to be heated : V (dm3 ou litre)

– Density of the liquid : ρ (kg/dm3)

M = V × ρ

ρ / Cp values for a few liquids :

Water : 1 / 1

Mineral oil : 0,9 / 0,5

Bitumen : 1,1 / 0,58

Acetic acid : 1,1 / 0,51

Hydrochloric acid : 1,2 / 0,6

Nitric acid : 1,5 / 0,66

b/ Calculation of the volume of liquid :

In a cylindrical tank :

– Volume of tank : V (dm3)

– Diameter of tank :  (dm)

– Height of liquid : H1 (dm)

V = π × (∅² ÷ 4)  × H1 In a rectangular tank :

– Volume of tank : V (dm3)

– Length of tank : L (dm)

– Width of tank : W (dm)

– Height of liquid : H1 (dm)

V = L × W × H1 2 / Calculation of the power required to compensate for heat loss :

– Heat loss : Pth (kW)

– Exchange surface area of the tank : S (m2)

– Required end temperature : t2 (°C)

– A temperature : ta (°C)

– Exchange coefficient : K (kcal/h × m2 × °C)

1,2 : Safety coefficient linked to our manufacturing tolerances and variations in network power

Pth = (S × (t2 – ta) × K × 1,2) ÷ 860

Exchange coefficient K as a function of the wind speed and insulation thickness : a/ Calculation of the exchange surface area of the tank :

Surface area of a cylindrical tank :

– Surface area of the tank : S (m2)

– Diameter of tank :  (m)

– Height of the tank : H2 (m)

S = (π × (∅² ÷ 4))  + (π × ∅ × H2) Surface area of a rectangular tank :

– Surface area of the tank : S (m2)

– Length of tank : L (m)

– Width of tank : W (m)

– Height of the tank : H2 (m)

S = ((L + W ) × H2 × 2) + (L × W) 