# Heat transfer coefficient of a cylindrical hot water storage tank depending on its size

I have a simulation model of a cylindrical hot water storage tank. The heat loss is determined by the surface area and the heat transfer coefficient.

A configuration of the storage tank with 900 liters was validated with a real scenario.

Now I would like to test how the scenario changes when the storage tank gets bigger. Thereby my surface becomes bigger, but I don't know if the heat transfer coefficient changes as well.

Does a larger storage tank usually improve the insulation so that the heat transfer coefficient changes?

• A larger tank will cool more slowly due to having a lower surface area to volume ratio, with the same transfer coefficient, if nothing else has changed. – Jonathan R Swift Nov 13 '19 at 12:41
• Yes, the HTC is a function of system geometry, fluid and flow properties and of course $\Delta T$, how to find it is actually lengthy. larger storage tank usually doesn't improve the insulation, there is a critical radius. – Sam Farjamirad Nov 13 '19 at 12:44
• @JonathanRSwift I'm not agree with you, the larger the tank, the larger the area, so the larger heat loss duo to convection. As I mentioned before, there exist a critical radius. And the HTC doesn't remain the same. – Sam Farjamirad Nov 13 '19 at 12:45
• @SamFarjamirad Thank you for your detailed answer. If I have understood it correctly, a larger heat storage tank with the same insulation will cause a changed HTC due to the changed system geometry. Would this change be significant if the ratio between radius and height remained the same? – MerklT Nov 13 '19 at 13:27
• That's something that you have to calculate to know, I'm very busy these days, otherwise I would gladly do it for you, hope other users contribute. – Sam Farjamirad Nov 13 '19 at 13:47