Theoretical and experimental investigation of total equivalent temperature difference (TETD) values for building walls and flat roofs commonly used in turkey

Theoretical and experimental investigation of Total Equivalent Temperature Difference (TETD) values for building walls and flat roofs commonly used in Turkey is proposed in this study. An experimental system consisting of two testing rooms are constructed in the University of Gaziantep Campus to perform this purpose. Each testing room consists essentially of four different walls and a roof, measurement elements, data logger, computer and an air conditioner. In the experimental system, inside rooms and outside air temperatures, surface temperature of each layer of the walls and roofs are measured instantaneously. Time lag and decrement factor for all the walls and roofs are calculated using the measured values of the temperatures. Hourly values of solar radiation flux on horizontal surface and outside air temperatures, which have been measured for ten years (1997 to 2007) for 72 cities, are taken from the Turkish State Meteorological Service to obtain more reliable and realistic TETD values. Hourly TETD values for 72 cities in Turkey are computed using time lag, decrement factor obtained for eight types of walls and two types of flat roofs. Theoretical study developed in previous study for solution of transient heat transfer problem for the multilayer walls and flat roofs is used to compare experimental results for the time lag and decrement factor, and daily temperature distribution, TETD and heat gain values of some selected structures. Decrement factors obtained from experimental values for walls of brick, AAC, blokbims and for roof without insulation are 0.145, 0.045, 0.065 and 0.48 while theoretical results for the same structures are obtained as 0.143, 0.043, 0.06, and 0.428, respectively. TETD values of the walls from the highest to the lowest values are obtained as briquette, brick, XPS, EPS, blokbims, AAC, covering and siding walls. Also, the blokbims and AAC walls are determined the best wall types from the wives of heat loss and gain within the walls without insulation.Keywords: Total equivalent temperature difference, time lag, decrement factor, sol-air temperature, heat gain