On-line monitoring of heat transfer coefficients in a stirred tank from the signatures of the resultant force on a submerged body

A new procedure for on-line monitoring of heat transfer coefficients (h) during immersion cooling is presented. The signature of the resultant force acting on a sphere connected to a load cell by a rigid rod and immersed in a stirred tank was used as an indirect measurement of h. Temperature evolutions over time of the sphere initially at 40 °C, immersed in water at 1 °C, were used to determine h at different positions in a tank. The standard deviation (sd) of the resultant force was used as a measurement of force oscillations (force signature). The results indicated that it is possible to estimate h between sphere and water from the force signature. For a given spatial positions in the tank, a transfer function with correlation coefficients up to 0.98 was observed when a logarithm function was used to correlate h with sd of the normalized resultant force on the sphere.