Analytical and experimental characterization of a miniature calorimetric sensor in pulsatile flow

TL;DR

This study develops and validates an analytical and experimental model of a miniature calorimetric sensor for measuring pulsatile flow in coronary arteries, demonstrating good agreement and potential for sensor optimization.

Contribution

The paper introduces a novel analytical model for a miniature calorimetric sensor in pulsatile flow, validated by experiments, aiding sensor design for coronary flow measurement.

Findings

Analytical model accurately predicts sensor response in steady and pulsatile flow.

Experimental results align well with theoretical predictions.

Sensor exhibits a quasi-steady response suitable for coronary flow assessment.

Abstract

The behaviour of a miniature calorimetric sensor, which is under consideration for catheter-based coronary artery flow assessment, is investigated in both steady and pulsatile tube flow. The sensor is composed of a heating element operated at constant power, and two thermopiles that measure flow-induced temperature differences over the sensor surface. An analytical sensor model is developed, which includes axial heat conduction in the fluid and a simple representation of the solid wall, assuming a quasi-steady sensor response to the pulsatile flow. To reduce the mathematical problem, described by a two-dimensional advection-diffusion equation, a spectral method is applied. A Fourier transform is then used to solve the resulting set of ordinary differential equations and an analytical expression for the fluid temperature is found. To validate the analytical model, experiments with the sensor mounted in a tube have been performed in steady and pulsatile water flow with various amplitudes and Strouhal numbers. Experimental results are generally in good agreement with theory and show a quasi-steady sensor response in the coronary flow regime. The model can therefore be used to optimize the sensor design for coronary flow assessment.