Interest only, how does an immersion only heat part of a cylinder of water?

[ericmark]

I know heat raises, but I would have thought a flow would have been started, with water flowing up the centre and down the sides. Stratification (water) is shown for large bodies of water, but a hot water tank is quite small, also does it matter as to size (power) of the heating element, will the heating the water using 200 watt be different to using 3000 watts.

I know the Willis system can heat the whole tank, so can other methods heat the whole tank?

 

[SUNRAY]

I know heat raises, but I would have thought a flow would have been started, with water flowing up the centre and down the sides. Stratification (water) is shown for large bodies of water, but a hot water tank is quite small, also does it matter as to size (power) of the heating element, will the heating the water using 200 watt be different to using 3000 watts.

I know the Willis system can heat the whole tank, so can other methods heat the whole tank?

If the heater is only in the top of the tank the water at the top will heat, the stat will trip and that'll be it, the warmest water will rise to the top.

If no further heating occurs, or the water is otherwise undisturbed any thermal cycling will stop.

Very simplistic and not totally accurate but hopefully goodenough to begin with.

Water stratification is basically no different to air stratification.


As to heating the whole space some means of circulating the water is required. In commercial HW storage there are often destratification pumps which commonly draw hot water from the regular draw-off port and reinsert it into the cold inlet port [ideally into a dedicated inlet port]. Putting the heater and thermostat at the bottom is also very effective as the hot water rising sets up a significant thermal current and of course it will continue heating until the bottom is hot.

 

[SUNRAY]

I know the Willis system can heat the whole tank, so can other methods heat the whole tank?

As I understand the Willis system the heating element is in an adjacent chamber and linked into the top and bottom of the storage space, the hot water rises and enters the top of the storage space and cold water is drawn from the bottom and will continue until the heat source is stopped.


In both the Willis and the conventional immersion systems the amount of water heated it dependant on where the thermostat is.

 

[ericmark]

Water stratification is basically no different to air stratification.

So air at the top of a mountain is warmer than air at sea level?

 

[SUNRAY]

So air at the top of a mountain is warmer than air at sea level?

Are you saying the air at ceiling level in a heated room is cooler than floor level?

 

[ericmark]

Are you saying the air at ceiling level in a heated room is colder than floor level?

I know air can be compressed and water can't, so different rules apply. And also the 4°C thing with water, so cold water (under 4°C) raises. Clearly from the USA as no Autumn

But the Summer shows 20°C not a gradual reduction with the "Thermocline" I would have expected

some circulation due to the heat being in the centre and the outer being cooled, but I know this is not the case, but can't work out why, the stratification will lakes needs the lake to be rather deep, just can't get my head around what I know happens, just can't work out why with such a small tank.