Investigation of laminar natural convection heat transfer within tubular daylighting devices for winter conditions

To prevent the increase of total energy consumption, the heat loss at the TDD should be taken into consideration when using TDD. This paper presents an experimental and numerical study on the laminar natural convection in TDD for winter conditions. The results show that the overall heat transfer coefficient of TDD can be decreased by using a separator plate in the TDD. Moreover, the overall heat transfer coefficient changes significantly with the position of the separator plate.