Experimental and numerical study of a small-scale and low-velocity indoor diffuser coupled with radiant floor cooling

We present results of one small scale displacement diffuser coupled with radiant floor cooling. Three control parameters are changed, both numerical and experimentally: flow rate, temperature difference between the undisturbed atmosphere and the supply air, and between the floor and the supply air. Flow visualizations and measurements of the velocity field are carried out using Particle Image Velocimetry for a laminar, axisymmetric, and steady state flow. Numerical simulations show an excellent agreement with experimental data. Special attention is paid to the vicinity of the floor. The main finding in this experimental setup is the appearance of a structure similar to a lee wave, typical in atmospheric flows. This standing wave, named thermal jump in this work, appears while forming a recirculation bubble in a stratified atmosphere with the eruption of the cool air flow that has greater temperature than the ground. To our knowledge, this is the first reported experimental evidence that produces a thermal jump under steady state conditions in air without the breakdown of the plume. Finally, we characterized the heat transfer as function of non-dimensional parameters, showing a parabolic correlation in terms of the radial distance.