Experimental investigations of flow and thermal behavior of wall confluent jets as a heating device for large-space enclosures. (15th May 2023)

• Record Type: Journal Article
• Authors: Choonya, Gasper; Larsson, Ulf; Moshfegh, Bahram
• Is Part Of: Building and environment. Volume 236(2023)
• Publication Date: 2023-05-15
• Subjects: Experimental study -- Parametric study -- Wall confluent jets -- Core zone of the wall confluent jets -- Response surface methodology -- Large-space enclosure heating; U∗decay Velocity decay factor [-]; Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2023.110282
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: The study aimed to explore the effects of inlet air temperature, outdoor air temperature, inlet bulk velocity, and the number of nozzles on wall confluent jets (WCJ) propagating along an external cold wall in a large space enclosure such as a greenhouse. A combination of experimental study and Response surface methodology has been used to predict the flow and thermal behavior of the WCJ for the studied cases. Box-Behnken design was used to determine the case matrix for four of the above-mentioned vital variables for non-isothermal cases. The experimental study employed constant current anemometers to measure the velocity and temperature of the WCJ. Results showed that the WCJ attached to the wall under both isothermal and non-isothermal conditions. This flow behavior suggests that the WCJ can be used to heat the external facades of large-space enclosures. All the stated variables were critical to the decay factor and decay rate of maximum velocity, albeit at varying levels. The velocity decayed faster with an increase in the inlet bulk velocity and outdoor air temperature. It also decayed faster as the number of nozzles and inlet air temperature decreased. The external wall surface temperature and the wall-heating effect increased as the momentum of the jet increased. The surface temperature on the external wall was most influenced by the inlet air temperature and least by the number of nozzles. Correlations of the second-order polynomial for the Response surface models that estimate the rate of velocity decay and temperature on the external wall were obtained. Highlights: Novel experimental study of flow and thermal behavior of wall confluent jets (WCJ). Response surface methodology has been used to perform a systematic parametric study. The WCJ can be used to heat facades of large-space enclosures. High bulk velocity and outdoor air temperature cause faster decay of velocity. Inlet bulk velocity affects the flow and temperature behavior of WCJ the most.