Hot‐Film and Calorimetric Methods With Transient Heating for Measurement of High Biofluid Flow Rate

ABSTRACT Accurate measurement of biofluid flow rate is critical for clinical diagnostics and physiological monitoring, such as in cerebrospinal fluid shunt assessment and vascular blood flow evaluation. Thermal flow sensors, particularly hot‐film and calorimetric types, are widely used in biomedical settings due to their broad dynamic range and long‐term stability. However, their performance declines at high flow rates. To overcome this drawback, we propose a transient heating method that applies a short‐duration thermal pulse and tracks the peak temperature response. This method, validated by experiments using artificial blood and vessels, significantly improves sensitivity to the flow rate change at high flow rates and reduces energy consumption. There exists an optimal heating time to maximize sensitivity to the flow rate. A contour plot of flow rate sensitivity vs. the heating time and flow rate is obtained to guide the selection of optimal heating time for different flow conditions.