Date of download: 11/11/2017 Copyright © ASME. All rights reserved. From: Real-Size Experiments on Reverse Natural Air Convection Between Inclined Parallel Plates for New Insulation Methods in Solar Flat-Plate Collectors J. Sol. Energy Eng. 2016;139(2):021003-021003-7. doi:10.1115/1.4035024 Figure Legend: Slope-dependent total U-value [W/m2K] of the upper hot (90 °C) plate to the lower cold (30 °C) plate with different insulation concepts between the plates for 30 mm (circles) and 50 mm (squares) plate distance: No insulation, i.e., air gap (hollow), two- (hollow and crossed) and four-sided (filled) film insulation. For comparison, U-values for different mineral wool insulations plotted (bar ranges, upper bar corresponding to 30 mm, lower to 50 mm insulation strength).