shape of h/w cylinder - does it make any difference

[Darth Ai]

Following on from a previous post about rationalising/extending the heating circuit in my system.

I'd like to get a customer built h/w cylinder which will fit the small alcove between the chimney and outside wall. It would be convenient if I could get a long thin cylinder to sit in the space. I know from talking to my local plumbers merchant that I can (within reason) get a cylinder of any size.

My question is, for an indirect system, would a tall think cylinder have any effect on heating the water?

TIA for any advice

Darth

[The Natural Philosopher]

No, but the volume to surface are will be lower, which will increase heatloss.

[logized]

A very thin cylinder may make it difficult to fit-in the normal coil of 22mm tube for heating the water and not leave much room for an immersion heater. Maybe you could get one of the new fast recovery cylinders - some of the low capacity ones are much narrower than standard types. Don't forget to allow for the insulation foam thickness too. Here are a few manufactures to look at specifications - (I have not bought any of these so cannot recommend except to say there may be a big price difference between brands, so worth checking).

[Christian McArdle]

Tall thin cylinders will have enhanced heat stratification, ensuring that the water stays hot to the last drop, rather than tailing off through a tepid stage.

However, they will have slightly worse energy efficiency due to increased surface area. All things being equal, a sphere is the best shape for this purpose, and a short dumpy one approximates one better.

Christian.

[IMM]

Darth,

The taller and thinner the better. This greatly aids stratification. Have a "quick recovery" coil fitted as well while you are at it.

[G&M]

The surface area to volume ratio will be higher so heat loss could be higher. Have thicker insulation sprayed on if you can.

[Ian Stirling]

All else being equal, a roll of nice thick loft insulation wrapped round the (already insulated) cylinder will improve things vastly in either case.

[Aidan]

Telford, for example, do standard 400, 450, etc diameter Rapid heat cylinders. If this is small enough, you could use a stack of several of these, it may be cheaper than a one-off special and the heating coil surface area would be large, giving fast recovery.

Would that be like a think tank?

[raden]

In message , IMM writes

Yeah ?

greater surface area to volume ratio

[IMM]

yeah.

[Christian McArdle]

True, but the usual reason for getting a tall thin cylinder is lack of space, which frequently prevents the installation of any meaningful extra insulation.

Christian.

[raden]

Keep up at the back please

[Ed Sirett]

8-)

From a heat retension point of view a spherical cylinder would have the lowest surface area for a given capacity.

Other considerations like the ability to stand stablely (sp?) on the floor and to fit in a fairly compact manner into a cupboard mean that a cylinder is a good compromise.

Tall thin cylinders might be useful where the space is very limited in width rather than height. However the normal 1050x450 or 900x540 units are effective like good enough for most homes. They give out most of the hot before running cold if you draw too much off at once (but that should be avoided by selecting the capacity to fit the requirements).

There is a poster in this thread who, ITSM, someimtes focusses on a single aspect of a product to the detriment of all the requirements. I will simply use the words he has used on occasion 'try to see the big picture'.