Understand liquid thermal mass flow sensors

How does a liquid thermal mass flow sensor work? Thermal mass flow sensors utilize the thermal properties of liquids to measure their mass flow. As shown in Figure 1, heat is introduced into the flowing liquid via a heater, and a temperature sensor measures how much heat the liquid absorbs. In such thermal mass flow meters used for liquids, the heater and sensor are placed around a stainless steel main flow tube, with no movable parts or obstructions inside the tube.