Abstract
AbstractEvaporative cooling is a traditional strategy to improve summer comfort, which has gained renewed relevance in the context of the transition to a greener economy. Here, the potential for evaporative cooling of common porous building materials, like natural stone and ceramic brick, is evaluated. The work has relevance also to the protection of built heritage because evaporation underlies the problems of dampness and salt crystallization, which are so harmful and frequent in this heritage. It was observed that the drying rate of the materials is, in some cases, higher than the evaporation rate of a free water surface. Surface area measurements by a three-dimensional optical technique suggested, as probable cause of this behavior, that surface irregularity gives rise to a large effective surface of evaporation in the material. Surface temperature measurements by infrared were performed afterward during evaporation experiments outside during a hot summer day in Lisbon. Their results indicate that ordi...
Highlights
Water is a constant presence in the intricate pore network of traditional building materials, such as mortar, stone, or ceramics
Two main regimes are in general considered, which for a material drying from saturation, correspond to the following main stages (Fig. 1): in Stage I, called the constant drying rate period (CDRP), there is liquid continuity across the material, and the wet front is located at their surface; the drying rate is constant because drying proceeds under steady-state conditions
It was experimentally observed that the drying rate during the CDRP from porous building materials, such as natural stone or ceramic brick, can be very high
Summary
Water is a constant presence in the intricate pore network of traditional building materials, such as mortar, stone, or ceramics. These tests followed a method similar to that described in Diaz Gonçalves et al (2012) except that, here, the experiments lasted just long enough to measure the CDRP drying rate They were carried out in a conditioned room at 20°C and 50% relative humidity (RH). The materials were wetted by capillary absorption through the base by means of partial immersion in water for 48 h in a conditioned room (20°C and 50% RH) After this period, the samples were removed from immersion and its lower face immediately sealed with polyethylene film to ensure that drying would be unidirectional, taking place only through the upper surface. The wet materials and the water-filled container were involved in polyethylene film, as shown, to prevent evaporation because this would lower their surface temperature.
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