Thermal energy meters

Installation of thermal energy meters is possible only in closed-circuit heating/cooling systems. The supply line and the return line of the heat-consumer loop form a circle, e.g.:

• Heating / cooling circuits of the residential building,
• Floor heating / cooling,
• Warm air productions (convectors),
• Heat-exchanger circle,
• Teleheating

In relation to purpose of use, the thermal energy meters take on two different roles:
a) As heat cost allocators on the secondary side, usually in multi-flat residential buildings or business facilities with multiple users
b) As primary meter in teleheating systems with or without heating sub-stations

The transferred heat for heating/cooling is calculated as follows:

∆H = k(T) x QV x ∆T x ∆t

∆H = change in enthalpy, transferred heat, e.g.: kWh, MJ
k(T)= heat transfer coefficient (also "k-factor"); approx. 1.16 MWh/m3/K or 4.18 MJ/m3/K for water; same density [kg/m3] multiplied by the specific heat of the medium [kJ/kg/K], depending on the absolute temperature of the supply line and the return line,
QV = volumetric flow rate of a medium, e.g.: l/h, m3/h,
∆T = difference between the supply line temperature and the return line temperature,
∆ t = measured time interval, e.g. in: h (hours), minutes, days.

In practice, we may come across two designs of thermal energy meters:

• A compact version of the meter, with one of the temperature sensors integrated inside the housing of the flow rate sensor. The heat meters have only one type approval for the whole assembly, temperature of the medium is limited to approx. 90 °C, and are more favourable in terms of cost, compared to the split version,
• A split version of the meter, where each assembly part requires individual approval and verification. These meters may be used in systems with temperatures of up to 200°C, and are a bit more costly compared to the compact version.

Our sales range also includes equipment by a Suisse manufacturer Sontex SA which, in addition to mechanical, also develops thermal energy meters using the so-called "Fluidic Oscillator" principle. This principle enables incredibly stable and long-term measurements with high accuracy; the measuring module does not contain any movable parts which could be subject to failure in case of unfavourable/demanding operating conditions.