Characterization of non-isothermal flows typical of built environments in a laboratory scale model. Part II – Numerical predictions with CFD

Is air moisture relevant on radiative heat exchange inside built environments?

“…Because of that, and prior to apply CFD modeling to actual built environments predictions, a comprehensive validation of CFD results against experimental data acquired at lab scale, which is feasible at acceptably fair cost and time, is mandatory (Serra and Semiao, 2013a;Eidan et al, 2017;Buratti et al, 2018;Guo et al, 2018;Ramadan et al, 2019 andShan et al, 2019). In fact, that is why laboratory scale models have been often used in transport phenomena research for validation purposes, including those occurring in built environments, before their application to full-scale systems transport phenomena research, including those occurring in built environments, scale models have been often used at laboratory studies to reduce the inherent cost and time associated with EC 37,4 the use of full-scale systems (Serra and Semiao, 2013a, 2013b, Posner et al, 2003and Lirola et al, 2017. Such an approach enhances the manual operability of the experiments (Ding et al, 2005), allowing, at the same time, a more detailed spatial interrogation and a smaller number of extraneous variables (Chung and Dunn-Rankin, 1998).…”

“…The previously described conditions make the airflows inside the built environment studied in this work three-dimensional, non-isothermal and turbulent (Serra and Semiao, 2013b). Continuity and momentum transport equations, together with those of transport of enthalpy and absolute humidity are solved Semiao, 2009, 2013b, for the complete mathematical formulation).…”

“…Buoyancy effects are taken into account through the addition of adequate terms into the Navier-Stokes equations and those of transport of k and « . Details on such flow modeling and best turbulence model suitability in predicting built environment flows may be found in several previous works (Chen, 1995;Yuan et al, 1999;Posner et al, 2003;Zhang et al, 2005;Gan, 2005;Evola and Popov, 2006;Serra and Semiao, 2013b). Radiation is modeled through the use of the discrete transfer method (DTM) (Lockwood and Shah, 1981) as described below, and moist air is considered as a participating medium.…”

“…The partial differential equations governing the turbulent fluid flow and heat transfer inside built environments (Serra and Semiao, 2013b, for details) are integrated over nonoverlapping control volumes defined by a grid generated in a way to cover the entire physical domain of the simulated space. For that, the fluxes of the transported variables at the control volumes interfaces are calculated recurring to finite differences based on the hybrid scheme yielding a set of algebraic equations that are solved through the tri-diagonal matrix algorithm.…”

“…Computational fluid dynamics (CFD), which has been widely used in HVAC flows simulations (Hong et al, 2000;Evola and Popov, 2006;Shih et al, 2007;Semiao, 2009 and, Croitoru et al, 2015), has proved to be a powerful tool for such purpose, as it has the potential to predict accurately all relevant dynamic parameters that control the performance of built environments in terms of energy and comfort. Even though, experimental work at laboratory scale models has been often used in transport phenomena research for CFD modeling validation purposes, as for built environments, before its application to full-scale systems, as such laboratory models are feasible at acceptably fair cost and time requirements (Serra and Semiao, 2013a;Serra and Semiao, 2013b, Posner et al, 2003and Lirola et al, 2017. On the other hand, the use of such CFD tools is limited by computer memory capacity and CPU time required to achieve accurate converged solutions that depend on the size of the studied built environment, the detail used to spatially describe the physical domain, the boundary conditions, the modeled physical processes and the occupants' activities.…”