Numerical and Experimental Investigation of Natural Convection in Open-Ended Channels with Application to Building Integrated Photovoltaic (BIPV) Systems

Abstract

Abstract. Numerical and experimental investigations of the flow and heat transfer in open-ended channel formed by the double skin façade have been undertaken in order to improve understanding of the phenomena and to apply it to passive cooling of building integrated photovoltaic systems. Both uniform heating and non-uniform heating configurations in which heat sources alternated with unheated zones on both skins were studied. Different periodic and asymmetric heating modes have been considered for the same aspect ratio 1/15 of wall distance to wall height and for periodicity 1/15 and 4/15 of heated/unheated zones and heat input, 220 W/m 2 . In computational study three dimensional transient LES simulation was carried out. It is shown that in comparison to uniformly heating configuration, non-uniformly heating configuration enhances both convective heat transfer and chimney effect.

Detailed flow development and indicators of transition in a natural convection flow in a vertical channel

“…in which v * is the friction velocity at the nearest wall and where It is important to note that the agreement between the experimental and numerical results has never been reached for this type of configuration [10], [16], [12] or [17]. The best reported agreements remain probably those of the numerical LES model of Lau et al [11] with the experimental results of Miyamoto et al [2].…”

“…A LES study of Kogawa et al [13] of a symmetrically heated channel, at uniform temperature associated the beginning of transition to the appearance of the Tollmien-Schlichting (TS) waves which are characteristics of the beginning of the natural transition of weakly disturbed natural convection flow [14], [15]. However, as was demonstrated by Fedorov and Viskanta [10] in a study using RANS models and by Lau et al [16] and Tkachenko et al [17] in LES investigations, the turbulent intensity level at the entrance of the channel proved crucial to obtaining a fairly good representation of the mean and turbulent quantities of the flow. Because of the presence of the inlet disturbances, the TS waves observed by Kogawa et al [13] are replaced by much more complex three-dimensional structures [7,18,19] which make their criteria impossible to use to locate the beginning of the transition.…”

“…Viskanta[10], Lau et al[16], Tkachenko et al[17] so as to match experimental data. To that end, the environmental noise in the room is modeled here as a disturbance of the velocity components generated at entrance of the computational domain by the Spectral Synthesizer method, based on the work of Smirnov et al[33] and implemented in ANSYS FLUENT.…”

“…A maximum yplus value of x + = 0.8 was obtained by using the maximum friction velocity, implying that viscous sub-layer had been sufficiently resolved. In the literature, similar grid resolutions have been used in numerical LES modeling of natural convection for which the transitional behavior of the flow was shown to be correctly modeled (see e.g [13],[23] [17]…”

A review of building integrated photovoltaic: case study of tropical climatic regions

“…Timchenko et al [54] applied certain system specifications (i.e. 1.5m x 0.7m x 0.1m size) to evaluate open channel PV.…”