How to calculate an expansion tank for heating a closed type
When designing a heating system with a circulation pump, the question arose about the capacity of the expansion tank. Please tell me the methodology for calculating it.
Answer
The capacity of the expansion tank is calculated by the formula Vp = (Vt × K) / D, in which Vp is the volume of the device, Vt is the volume of the coolant in the heating system, K is the expansion coefficient, which for water is 0.034. The divider D characterizes the efficiency of the storage tank itself and is calculated by the formula D = 1 - (Pres / Pmax). In it, Pmax is the maximum pressure in the system, and Pres is the initial pressure in the tank, which should be 1.5 atm according to factory recommendations.
So, for a heating system in which 120 l of water circulates under a pressure of 3 atm, a storage tank with a capacity of Vp = (120 × 0.034) / (1 - (1.5 / 3)) = 8.16 l is required. Given the fill factor of the expansion tank itself, it should be designed for 8.16 / 0.37 = 22 liters.
You can find out the fill factor of the device for various pressure values from the table below.
More information on how to choose an expansion tank can be found here:https://aquatech.tomathouse.com/en/otoplenie/kotelnaya/rasshiritelnyj-bak-dlya-otopleniya.html
