The heating of fluids with a storage tank is used when the flow is discontinuous allowing the gradual accumulation of thermal energy.
Although this kind of heating is used by a lot of industrial plants, the most common heater with a storage tank is the boiler.
The energy balance of this method in comparison with that without storing are almost the same but the possibility of to heat the fluid in a longer time allows a drastic reduction of the electric power installed.
For a correct design is necessary to valuate the quantity of fluid to store and the electric power of heating that must be installed, making sure that the avaiability of heated fluid is greater then the required.
There are two ways to increase the stored energy limiting the dimensions of the tank,
also both avaible:
- Increase the fluid temperature and then dilute it in the usage phase.
- Increase the mass of the tank (choosing the right material).
Selection kind of fluid
Fluid density
kg/l (kg/dm3)
Specific heat
kcal/kg
Volume of fluid to heat
l (dm3)
Tank material
Material density
kg/dm3
Specific heat of the material
kcal/kg
Tank mass
kg
Kind of insulation
Thermal conductivity
W/m K
Insulation thickness
mm
Exposed surface
m2
Installed power
kW
Ambient temperature
°C
Fluid starting temperature
°C
Required fluid temperature
°C
| Results | |||
| Time necessary to reach the temperature | h | ||
| Thermal energy stored | kW | ||
| Thermal energy stored (equivalent) | kcal | ||
| Wasted thermal energy during the warming | W | ||
| Hourly thermal energy wasted at the max temperature | W/h | ||
Notes.
The results are valid until the fluid reaches the 90% of the boiling temperature at the
work pressure of the system, over the latent heat begins to be important and here is not considered.