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**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).**

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

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

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– 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

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**Pch = (M × Cp × (t2 − t1) × 1,2) ÷ (860 × T)**

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**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)

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** M = V × ρ
**

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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

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**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)
**

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