Ultrasonic Flow Sensor and Thermal Energy Sensor with Non-Invasive Identification of No-Flow and Improved Accuracy

An ultrasonic flow sensor configured to measure a flow of a fluid flowing through a tubular structure, the flow sensor comprising:

• a first detection unit arranged to transmit and receive ultrasonic waves using at least one ultrasonic transducer;
• a first temperature sensor arranged and configured to detect a temperature (Tf) of the fluid;
• a second temperature sensor arranged and configured to detect a temperature (Ts) of the surroundings;
• a data processor configured to receive data detected by the at least one ultrasonic transducer and the first and second temperature sensors,
• wherein the flow sensor is configured to:
• determine a time-of-flight (t, t1, t2) of the ultrasonic waves and calculate a change in speed of sound based on the time-of-flight (t, t1, t2);
• calculate an expected change in the speed of sound as a function of the detected temperature (Tf) of the fluid;
• determine if the expected change in the speed of sound corresponds to the change in the speed of sound calculated based on the time-of-flight (t, t1, t2);
• and
• identify a no-flow state, in which there is no flow of the fluid when:
• A) the expected change in the speed of sound corresponds to the change in the speed of sound calculated based on the time-of-flight (t, t1, t2), and
• B) a temperature difference (ΔTsf) between the surroundings and the fluid is below a predefined level which is pre-set at a fixed level between 0.01 degree Celsius and 0.5 degree Celsius.