Cooling Load Reduction by Ambient Wetting Technique. (Experimental study)
The increase of the building temperatures above the normal thermal comfort specifications is due to the external layer of traditional building walls in summer seasons exposed to huge heat waves. In order to counteract that, a moist external air gap has been constructed around the building to help eliminate the direct ambient effects on the walls of the buildings. A simple wooden structure has been constructed to support the fiberglass mesh window screen that lies about 600 mm from the wall spanning its entire dimension (2×1) m. Three spray water nozzles were installed on the external layer of the wall. Nozzles directed towards the mesh window screen fiberglass to create a foggy layer.
The traditional wall (240 mm common bricks) of the building was covered with 4 types of materials that are available locally: face bricks 120mm thickness, tile bricks 40 mm thickness, limestone 40 mm thickness, and solid cement bricks 40 mm thickness. The external covering layer is 50 mm away from the traditional wall; this has been utilized as the external air gap that allows the ambient air to move using a fan. The fan gets its energy from a photocell.
The study was performed in Baghdad city (latitude angle 33.2 N°) during the summer season (May through September) 2019 one day for each month, from 6 AM to 7 PM, That testing room was maintained standard comfort level at 26.5˚C, 50% RH.
The researcher found out that the electrical energy consumed within natural ambient air for a traditional wall was 316 kWh, the four another studied cases in this research recorded consumption of 224 kWh, 258 kWh, 248 kWh and 302 kWh. When the water spray nozzles pump was operating to humidifying the ambient air in the external gap, a drop in the electrical energy consumed was noticed, 60 kWh, 52 kWh, 102 kWh, and 143 kWh for studied cases. Achieved energy-saving, was 162 kWh, 206 kWh, 144 kWh, and 159 kWh. Saving percentages were recorded for studied cases 72%, 83%, 58%, and 53%.
According to the results of this study, tile bricks are the best cover material out of the 4 used in the study. The most electrical reduction (206 kWh) and the highest percentage (83%) were seen with tile bricks.