Transport of a passive scalar across a protective wall-jet in a pipe. Part I: Data acquisition

▶ Research was motivated by the problem of setting up a “guard flow” layer on the inner surface of a pipe. ▶ Velocity profiles measured by Pitot probe made by the author himself. ▶ Injection of an improperly chosen fast protective wall-jet may actually lead to re-circulation and collapse of the ordered flowfield. ▶ Transport of passive scalar – temperature - propagated from warm core flow across the wall-jet towards the wall was measured using a thermocouple probe, made by the author himself. ▶ Experimental results were supported by concurrent numerical flowfield and temperature field solutions. A wall-jet of a different fluid (or the same fluid at a different thermodynamic state) is blown along the inner surface of a pipe to prevent a contact between the main central flow and the pipe wall. Although motivated by problems encountered in measuring radioactivity, the analogy between heat and mass transfer was utilised for the experiments and concurrent numerical computations which investigated transport of heat from the central air flow towards cool pipe wall, across the protective cool air wall-jet. Similar protective cooling of walls may be actually itself an important application. Another one may be segregation required due to gas chemical aggressiveness. This first part discusses the details of the experiment and the character of the temperature and flow fields evaluated from measured profiles of time-mean velocity and temperature. Analysis of the data, using mutually supporting information from the experiment as well as the computations, is handled in the next, second part.