Calorifier - orientation important?

[PCUK]

Thanks Vyv, I meant to say in at the bottom for the reason you mention. The other points about having the hottest water at the top are valid if the system works OK. Maybe it should be in at the bottom for raw water engines and best circulation and in at the top for fresh water engines for best domestic water heating.

 

[LittleShip]

No it shouldn't! The feed of hot water from the engine to the heating coil should enter at the top and exit at the bottom. This is the favoured direction for the thermodynamics, i.e. the water wants to fall as it cools, and it opposes the increase in heat of the tank contents. Connecting the wrong way around creates a strong convective flow that can be sufficient to arrest the flow of a circulation pump.

This is quite true on Gravity fed Central heating systems, that said however.......

I was involved in some performance testing for pumped heating to cylinders and at the end of it there was a preference to pump the water into the bottom of the coil as it produced approx 5% increase in the cylinders performance.

In reality the coils in boat cylinders (at least mine) are not up to quick reheating as they are only a single coil and therefore take quite a long time to heat the cylinder. In comparison a modern C/H cylinder will reheat in less than 1/2hr due to the larger coils fitted to them.

Tom

 

[Marsupial]

Well done Tom, my boat cylinder 30 ltr seems to have a massive coil in it as it heats to scalding in around 20 minutes using the engine.

The 5% you found is about right but most householders wouldnt notice it and as you know there are lots of other variables to consider, like the temperature of the feed water, pipe size, length of run etc. . .

 

[Marsupial]

Geof

"My comment, (perhaps poorly worded) about the direction of flow of the heating water is based on the temp difference between the heatING water and the heatED water. To maximise the temp of the heated water, surely the inlet of heating water must be at the place where the hottest water in the tank sits?"

Its the other way round, put the heat where its coldest - or in the case of a fridge put the cold where its hottest. The ice box is at the top of the fridge not the bottom, domestic radiators work best under windows - the coldest part of the room, AC units are best high on the wall (where the heat is) not low on the floor, therefore hot water feeds to heat cylinders work best fed to the coldest part of the cylinder - but most people wont notice the difference on the last one.

Put the ice box at the bottom of the fridge and the fridge wont get cold - except at the bottom the top will stay warm.

Enjoy your hot water!

 

[longjohnsilver]

Another query about calorifiers as there seem to be some experts here. On my boat the pipes from the engine go to the calorifier but the heater element doesn't come into contact with the water in the tank. It looks like a copper cylinder of only a few inches in diameter which slides into a slot/hole at the bottom of the calorifier/tank. Seems very strange to me as on previous boats it's been the traditional calorifier arrangement.

Needless to say the water never gets very hot, and in winter hardly heats at all. It's an American boat and the company who make the calorifier seem to be a respected company over there but I can't for the life of me figure out why any calorifier would have this arrangement. Anyone else come across a system like this?