The Twente mass and heat transfer tunnel

We present a newly-built recirculating vertical water tunnel with global temperature control, bubble injection and local heat/mass injection for the study of local heat and mass transfer in turbulent (bubbly) flows. The tunnel is made of high-grade stainless steel permitting the use of salt solutions in excess of 15% mass fraction, besides clear water. The tunnel volume is 300 liters. Three interchangeable measurement sections of 1 m in height but of different aspect ratios (0.3 x 0.04 m², 0.3 x 0.06 m², 0.3 x 0.08 m²) span a Reynolds-number range from 5 x 10³ to 1.6 x 10⁵ in the case of clear water at room temperature.

The glass vertical measurement sections allow for optical access to the flow, enabling techniques such as laser Doppler anemometry, particle image velocimetry, particle tracking velocimetry and laser-induced fluorescent imaging. Thermistors mounted on a built-in traverse provide local temperature information at a few milli-Kelvin accuracy. Combined with simultaneous local velocity measurements the local heat flux can be studied.