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This paper discusses an experimental study of the direct delivery of cold air into a full-scale environmental chamber using different diffusers, i.e., a multi-cone circular ceiling diffuser, a vortex diffuser, and a nozzle-type diffuser. Comparisons have been made of mean flow patterns, temperature distribution, thermal comfort using the PD model and the ADPI model, and condensation risk. The results show that both the vortex diffuser and the nozzle-type diffuser are capable of providing a very good indoor thermal comfort environment compared with that provided by the multi-cone circular diffuser, which tends to create cold air dumping in the occupied zone. The vortex diffuser exhibits a higher induction effect than the nozzle-type diffuser. However, the airspeed generated by the vortex diffuser is generally lower than that of the nozzle-type diffuser. Both the vortex diffuser and the nozzle-type diffuser can be considered to have condensation-free characteristics, although some vapor film was observed in the early stage of a hard start-up test for the nozzle-type diffuser.

Units: Dual

Citation: ASHRAE Transactions, vol. 105, pt. 1