Heat losses of window compact shutters

Abstract

Window shutters are usually made of wood. They protect glazed windows at their external sides from mechanical damages and inconvenient weather conditions. A typical window compact shutter is described and its thermal properties are discussed. In winter season, the heat transfers inside the window shutters represent unwanted heat losses. These transfers of heat are caused especially by convection and radiation running between the warm glazed side of the window to the cold external side of the shutter and through this external side into outdoor space. The heat transfers are computed on the basis of physical relations. The computation of convective heat transfer is based on the correlation relations utilizing Rayleigh`s and Prandtl’s numbers. The radiative transfer is computed by means of the Stefan-Boltzmann law and the Kirchhoff law. The thermal resistance of the typical shutter is derived. It is shown that this resistance is temperature dependent. It is the radiation that is responsible for the temperature dependency of the thermal resistance of compact window shutters. The formula for thermal resistance derived in this contribution may assist the building technologists to evaluate insulation capabilities of similar compact shutters possessing comparable geometric dimensions and similar thermal emissivities.Window shutters are usually made of wood. They protect glazed windows at their external sides from mechanical damages and inconvenient weather conditions. A typical window compact shutter is described and its thermal properties are discussed. In winter season, the heat transfers inside the window shutters represent unwanted heat losses. These transfers of heat are caused especially by convection and radiation running between the warm glazed side of the window to the cold external side of the shutter and through this external side into outdoor space. The heat transfers are computed on the basis of physical relations. The computation of convective heat transfer is based on the correlation relations utilizing Rayleigh`s and Prandtl’s numbers. The radiative transfer is computed by means of the Stefan-Boltzmann law and the Kirchhoff law. The thermal resistance of the typical shutter is derived. It is shown that this resistance is temperature dependent. It is the radiation that is responsible for the temperature dependency of the thermal resistance of compact window shutters. The formula for thermal resistance derived in this contribution may assist the building technologists to evaluate insulation capabilities of similar compact shutters possessing comparable geometric dimensions and similar thermal emissivities.