Air distribution in rooms generated by a textile terminal - comparison with mixing and displacement ventilation

Experiments with air distribution in rooms generated by a low impulse textile terminal are compared with the air distribution obtained by mixing ventilation and displacement ventilation. The air distribution in the room is mainly controlled by buoyancy forces from the heat sources, although the flow from the textile terminal can be characterized as a passive displacement flow with a downward direction in areas without thermal load. A variant of the system is supplied with horizontal jets from openings in the textile terminal to generate a mixing flow in the room. Both systems are compared with mixing ventilation based on a wall-mounted diffuser and with displacement ventilation with a wall-mounted low velocity diffuser All systems are tested in the same room with the same heat load consisting of two manikins, each sitting at a desk, two PCs, and two desk lamps, producing a total heat load of 480 W In addition, cases with a single workplace are also tested. The design of the air distribution system is in all four cases based on flow elements for the diffuser, a maximum velocity assumption, and a critical vertical temperature gradient in the room. The characteristics of the air distribution systems are addressed by analyzing the acceptable conditions for the supply flow rate and the temperature difference for the different systems. The paper shows that an air distribution system based on textile terminals is able to generate comfortable velocity and temperature conditions at the same thermal load as can be obtained by both a mixing ventilation system with a wall-mounted diffuser and a displacement ventilation system with a low-velocity wall-mounted diffuser. The comparison is extended by considering both the local discomfort caused by draft rating and the percentage of dissatisfied due to the temperature gradient when this is relevant to the systems. The draft rating is very low for the low impulse system (textile terminals), and the temperature gradient is also low because of the high level of room air mixing.