Simultaneously combined liquid crystal surface heat transfer and PIV flow-field measurements

An experimental technique has been developed which combines simultaneous high-density particle image velocimetry (PIV) with a new thermochromic liquid-crystal based instantaneous convective heat transfer sensing system. The new heat transfer sensing system employs liquid crystals applied to the non-flow side of a constant heat flux foil, and isolated from the support plate by a thin insulating cavity. The resulting composite sensing sheet is capable of a 66 Hz frequency response and, when utilized in a water flow, it can track instantaneous variations in convective heat transfer for turbulent flows. Placement of the liquid crystals on the non-flow side of the constant heat flux foil also provides optical separation from the flow field, allowing the simultaneous application of high image-density PIV measurements. A description of the experimental apparatus is provided along with a validation and uncertainty analysis of the combined technique. Selected quasi-three-dimensional constructs obtained using this new technique are presented for a variety of turbulent flow configurations.