  Fluid temperature is important for the analysis of the heat transfers in
thermal hydraulics. An accurate measurement or estimation of the fluid
temperature in multiphase flows is challenging. This is due to that the
thermocouple signal that mixes with temperature signals for each phase and
non-negligible noises. This study provides a new approach to estimate the local
fluid temperature in multiphase flows using experimental time-series
temperature signal. The thermocouple signal is considered to be a sequence with
Markov property and the particle filter method is utilized in the new method to
extract the fluid temperature. A complete description of the new method is
presented in this article.
