Testing Method for Non-Isothermal Radial Wall Jets from Ceiling Diffusers Used in Building Ventilation

Maria Hurnik ()
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Maria Hurnik: Department of Heating, Ventilation and Dust Removal Technology, Faculty of Energy and Environmental Engineering, Silesian University of Technology, Konarskiego 20, 44-100 Gliwice, Poland

Energies, 2025, vol. 18, issue 2, 1-13

Abstract: Diffusers producing radial jets attached to the ceiling are most often used in ventilation and air conditioning systems. In building ventilation, the temperature of the jet supplying the air into the rooms is usually different to the surrounding air temperature. To save energy for air transportation during periods of low heat gains, the air flow should be reduced as low as possible, to about 20% of its nominal value. A significant decrease in the air flow supply in cooling mode may cause cold air dumping and, consequently, increase the risk of local discomfort due to drafts in the occupied zone. In this study, a method for assessing the effect of non-isothermality on the speed distribution of radial wall jets has been developed. The measured terminal speed isolines, W = 0.2 m/s, were compared with the isolines determined for isothermal jets. The test results have shown that, for radial wall jets supplying air at an Archimedes number higher than approximately 50 × 10 −4 , the risk of jet dumping is significant.

Keywords: non-isothermal radial wall jet; ceiling diffuser; air velocity; air speed; hot-sphere anemometer; jet spread; velocity decay; jet envelope (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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