Free convection in parallelogram-shaped enclosures with isothermal active walls: viscous shear stress in active systems

Abstract

Thermocouples are often used for thermoregulation of active thermal systems. When the junctions of these sensors are under a natural convection flow, it is necessary to take into account the viscous stress that can affect the measurement of temperature and therefore the regulation set points. The main objective of this work is to study the viscous shear stress taking place close to the active hot wall in closed air-filled cavities of parallelogrammic shape. The influence of shear stress is examined for different inclination angles of the cavity and large Rayleigh numbers which are usual in thermal applications. The local stress distributions are presented for the steady state for all the geometric configurations considered. The Nusselt number at the hot wall as well as the temperature and stream function distributions in the cavities are also included. The findings obtained from the numerical simulation using the finite volume method are validated by thermal measurements on an experimental cavity. This study confirms the need to properly choose the location of thermocouples in the reference cell used for controlling the active system.

Radiative heat transfer in a parallelogram shaped cavity

“…The particular case of the parallelogram shaped cavity has some interesting applications in buildings and solar energy systems [1]. Natural convection studies [2][3][4] have been conducted in such geometries and have shown the influence of the angle between adjacent boundaries on the flow pattern and heat transfer.…”