7/30/2019 Expansion Tank Calculation

1/1

I. FOR TEMPERATURES 70 to 140oC (ASME)

I.1. Required Data

1. Vt Min. Volume of Expansion Tank ? m3

2. Vs System volume 1 m

3. t Max. average Operating Temperature 90oC

4. Pa Pressure in Expansion Tank when water 1.5 bar (abs.)

first enters (abs.)

5. Pf Initial fill or min. pressure at Tank (abs.) 1.5 bar (abs.)

6. Po max. operating pressure at Tank (abs.) 3 bar (abs.)

I.2. Formula

Vt = (0.000738t - 0.03348) Vs / [(Pa/Pf) - (Pa/Po)] = m

= lt

II. FOR TEMPERATURES BELOW 70oC (WIDELY USED FORMULA)

II.1. Required Data

1. Vt Min. Volume of Expansion Tank ? m

2. t Max. average Operating Temperature 70oC

3. Pa Pressure in Expansion Tank when water 1.5 bar (abs.)

first enters (abs.)

4. Pf Initial fill or min. pressure at Tank (abs.) 1.5 bar (abs.)

5. Po max. operating pressure at Tank (abs.) 3 bar (abs.)

6. E Net expansion of the water in the System 0.034 m3

when heated from min. to max. temperature

(from graph using t)

II.2. Formula

Vt = E / [(Pa/Pf) - (Pa/Po)] = 0.07 m = lt

Notes: 1. In case of Diaphragm Exp. Tanks, Pa = Pf

Source: 1987 ASHRAE H/B - HVAC Systems & Applications (see book for more info, details & examples)

68.0

0.07

65.9

SIZING OF EXPANSION TANK