In a method of determining a flow rate in an intravenous fluid delivery system according to one embodiment of the present invention, the fluid delivery channel forms a segment of the intravenous infusion system. An input thermal signal is emitted into a source location of a fluid delivery channel at an emitting instant. A first output thermal signal is received from a first sensor location of the fluid delivery channel at a first receiving instant. The first sensor location is positioned with a first interval downstream from the source location. The input thermal signal, the first output thermal signal, the emitting instant, the first receiving instant and the first interval define a first measured thermal profile. The first measured thermal profile is matched with a reference thermal profile which corresponds to a reference value, and the flow rate can be determined.