The classical problem:
The classic problem:
Each supply flow mixes the entire tank content to a smaller or greater degree. This quickly causes the tank to have a uniform temperature level. The temperature level is often not sufficient to operate the heating system or heat the domestic water.
The costly consequence of these systems is being reheated by the burner.
How can the physical properties of the heating water in a stratified storage tank be optimally utilised?
Quite simple – by considering the following principle demands:
1. The layer system or other inserts built into the tank must not consist of metallic materials. Metals are good heat conductors and would quickly compensate for/mix up different temperature layers again.
2. No heat exchangers may be located inside the heat exchanger: This "thermal stirrers" would generate unwanted currents and destroy temperature layers, or mix up layers with different temperatures.
4. A largely calm ("laminar") inflow of relatively large amounts of water into the tank volume is only possible through multi-chamber systems: Depending on the velocity, flows into pipes always generate overpressure or underpressure (venturi effect).
5. Preliminary sorting into different temperature levels (hot, warm, cool) is generally necessary, as there would otherwise be dynamic, turbulent currents within the tank because of excessive temperature differences and at the same time great height differences, also caused by thermal lift and descent rates (natural law of gravity).
What do good stratified storage tanks look like?
Stratified storage tank OSKAR-10/... from ratiotherm
The thermal hydraulic 5-chamber layer insert of OSKAR-10/... comprises a heat-resistant but bad heat conducting, that is, heat insulating plastic, and depending on the tank size and required volume flow one or more basic main pipe/s with correspondingly sized internal "inflow and stratification chambers".
The supply or withdrawal of heat flows takes place via this layer insert with its sophisticated connection system, exactly suited to OSKAR-10/... and its areas of application and also made of heat resistant, thick-walled plastic pipes with good thermal insulation properties; in other words: the charging and discharging of OSKAR-10/…
Because of the significantly larger cross-sections of this chamber system, compared to the connecting pipes, the flow rate (dynamic, kinetic energy) of the storage medium water is reduced to a minimum.
Due to the extremely slow flow of the water, which is hardly moving, and the integrated water deflections in the chambers, the effect of a calm lift or descent according to the physical law of gravity (warm water is lighter than cold water), can develop without interference.
Why temperature layers?
The different heat generators (solar, wood, etc.) largely vary in their output rating and thus also deliver very different temperatures.
If they are not mixed but stored in layers, their energy content is fully preserved and can be used advantageously for heating or domestic hot water heating.
Mechanical stratified storage tanks
often work with external tank connections at different heights.
The heat flows are then supplied directly to the tank content with different temperatures using control technology.
The many lateral connections thereby constitute a drawback: They penetrate the tank insulation thereby causing increased "heat loss" of the tank.
Furthermore, detrimental effects on existing temperature layers in the tank can hardly be avoided. The necessary control technology for "mechanical" stratified storage tanks is extremely expensive, depending on the system, and is the basis for the entire range of problems regarding maintenance, failure and wear.
Running costs for servicing and maintenance are inevitable.
Thermal hydraulic stratified storage tanks
with single chamber systems and integrated heat exchangers for utilising solar power function relatively well.
The handling of larger volume flows and/or different return temperatures from consumer circuits represents a problem, however, often causing a mixing of the temperature layers.
ratiotherm OSKAR stratified storage tank
The thermal hydraulic stratified storage technology developed by ratiotherm
- with the 5-chamber layer inserts in OSKAR-10/...
or special layer inserts in ratiotherm special stratified storage tanks
- sorts out different temperature levels using a connection system especially suited exactly to the respective storage tank type.
All connections are inserted into the tank at the bottom from underneath and emerge in the corresponding temperature zone of the multi-chamber system of the layer insert
These calming and layer chambers let the heat flows rise and descend in the centre of the tank like in a "lift" in a completely calm and current-free manner.
The supply and withdrawal of heat flows into or out of the corresponding temperature layers of the tank volume range takes place according to temperatures.
In practice, most of the temperature zones are reached with this method.