A thermal energy meter is an instrument designed to measure the thermal energy which, in a thermal energy exchange circuit, is given up by a liquid called the thermal energy-conveying liquid.
A thermal energy meter is either a complete instrument or a combined instrument consisting of the sub-assemblies, flow sensor, temperature sensor pair, and calculator, as defined in Article 4(2), or a combination thereof
| θ | = | the temperature of the thermal energy-conveying liquid; |
| θin | = | the value of θ at the inlet of the thermal energy exchange circuit; |
| θοut | = | the value of θ at the outlet of the thermal energy exchange circuit; |
| Δθ | = | the temperature difference θin — θοut with Δθ ≥ 0; |
| θmax | = | the upper limit of θ for the thermal energy meter to function correctly within the MPEs; |
| θmin | = | the lower limit of θ for the thermal energy meter to function correctly within the MPEs; |
| Δθmax | = | the upper limit of Δθ for the thermal energy meter to function correctly within the MPEs; |
| Δθmin | = | the lower limit of Δθ for the thermal energy meter to function correctly within the MPEs; |
| q | = | the flow rate of the thermal energy conveying liquid; |
| qs | = | the highest value of q that is permitted for short periods of time for the thermal energy meter to function correctly; |
| qp | = | the highest value of q that is permitted permanently for the thermal energy meter to function correctly; |
| qi | = | the lowest value of q that is permitted for the thermal energy meter to function correctly; |
| P | = | the thermal power of the thermal energy exchange; |
| Ps | = | the upper limit of P that is permitted for the thermal energy meter to function correctly. |