First average and local heat transfer measurements on a forced air-flow at low Re-numbers through a rectangular channel with ribbed surfaces

Accuracy in evaluating heat transfer coefficient by RANS CFD simulations in a rectangular channel with high aspect ratio - Part 1: benchmark on a channel with plane walls

“…The experimental set-up is described in detail in [3], briefly it consists in a rectangular channel of 1:10 aspect ratio. The main geometric parameters of the section dedicated to measurements, are summarized in Table 1.…”

“…Since it is a threedimensional case, given the three directions x, y, z where x is the direction of the channel width, y the direction of the channel height and z the streamwise direction, a sensitivity analysis has been carried out for each dimension. Working at different Reynolds numbers [3][4], different flow regimes (laminar or turbulent) are considered so grids have been constructed respecting the needs of each case analysed. Per example for laminar Reynolds, the number of elements for the whole channel has been around 5•10 6 .…”

“…Probably, given the high aspect ratio of the considered channel, in the experimental measurements, the tiny lateral walls tend to be heated from the upper and the lower walls due to conduction phenomena. To better understand why this approximation can be accepted is recommended to deepen the working conditions of the experimental setup, accurately described in [3]. This approximation applied to the numerical boundary conditions to better represent the experimental configuration is applied to all the following CFD simulations carried out.…”

“…Channel with high aspect ratio, in addition to fulfil the industrial interest for narrow channels, ensures a wide central area undisturbed by edge losses that can be dedicated to heat transfer. At the ThermALab laboratory at Politecnico di Milano, authors have been and are currently involved in experimental analysis on fluid-dynamics and heat transfer characteristics of forced convection inside a channel with an aspect ratio of 1:10 [3][4][5][6]. To complement the experimental campaign with a CFD model, this work is carried out.…”

Heat fluxes distribution and uncertainty in low-Reynolds flow regimes inside a ribbed channel

“…The two approaches are complementary, and have been both used at the ThermALab Laboratory at Politecnico di Milano in a long-term study on heat transfer enhancement in closed channels, see for example [4] on the global approach. In particular, a channel with one heated wall has been built for improving the detail of the local convective heat transfer measurement, and a new analysis procedure has been developed by Gramazio, Vitali, Fustinoni and Niro, see [5] [6], in the effort to validate new CFD simulations by means of DNS.…”