TECHNICAL FEATURE FIGURE 4 Airflow patterns at the central plane for non-isothermal conditions with the heat source on the table show that under low supply airflow rates the upward buoyant plume can form non-unidirectional patterns. a) 200 cfm (94.4 L/s) b) 400 cfm (188.8 L/s) c) 600 cfm (283.2 L/s) d) 800 cfm (377.6 L/s) exists only in the vicinity of the supply diffuser. With increasing supply airflow rate (or the cooling capacity), the downward moving jet sustains unidirectional motion and the average temperature in the space starts decreasing with shrinking zone of high temperature (Figure 6). It should be noted that in these cases the upward buoyant plume can act as a protective shield for the heat source objects on the table which may be desirable in certain situations. However, when supply airflow rate is increased to 800 cfm (377.6 L/s), the cooling capacity of the supply air reaches four times the cooling load and the air jet 26 ASHRAE JOURNAL ashrae.org J U N E 2 0 19 becomes unidirectional and overcomes the upward buoyant force from the heat source. It should be noted that, unlike previous cases, in this case the zone of high velocity detaches from the ceiling and moves downward (Figure 5d). The cold supply air gets hot as it passes through the heat source, moves sideward, and then upward along the side walls of the chamber. As a result large recirculation zones are formed on both sides of the supply jet which entrain the surrounding warm air into the cold air stream (Figure 6d). Such recirculation pattern results in thermal stratification in the chamber forming a zone of cold air near the floor.https://www.ashrae.org/