Evaporation characteristics of a solar irradiated naturally ventilated class a pan

• Main Author: Md. Ashikur Rahman
• Format: Thesis
• Language: English; English
• Published: 2016
• Subjects: QC851-999 Meteorology. Climatology Including the earth's atmosphere
• Online Access: https://eprints.ums.edu.my/id/eprint/39289/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/39289/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/39289/
• Institution: Universiti Malaysia Sabah

Evaporative water loss is of significant importance in many fields ranging from hydrology and agriculture, to food science and engineering applications. Water removal from industrial effluent streams, food processing industry and the biodiesel conversion process from microalgae is an important step in wastewater and sludge treatment, harvesting and drying of crops. The purpose of the experiment was to observe the characteristics of evaporation from class A pan and to enhance the rate of evaporation flux by using enhanced natural draft that showed Chu et al. in (2012) by installing wire mesh on the chimney to impede cold inflow. This study monitors the effect of natural draft flow enhancement on evaporation. Experiments were conducted in square shape pan at three different sizes. Dimensions of the experimental pans were side lengths 1.07m, 0.6m and 0.6m; depth 0.254m, 0.254m and 0.2m respectively. The solid wall type solar irradiated chimney was used to enhance natural draft in this research. There were two designs of solar irradiated naturally ventilated pan (SINVAP). The specification for Design-1 category SINVAP was 0.105m2, 0.28m2 and 0.77m for inlet opening area, outlet opening area and solid wall chimney height respectively. The dimensions 8.65×10-3 m2, 0.26m2 and 1.2m were the corresponding values of Design-2 type SINVAP. A 0.64mm×0.64mm size wire mesh was installed at the outlet of the SINVAP to impede cold inflow in the SINVAP. Over about 100 days evaporation readings were taken using the different pan configurations. The experimental result showed the evaporation flux from the SINVAP with wire mesh at outlet opening was around 14% more than the open pan; in the SINVAP without wire mesh at outlet opening was lower than the open pan evaporation rate. The SINVAP evaporation flux was found to be moderately influenced by the net radiation, vapor pressure deficit and natural ventilation draft. The daily average net radiation in the SINVAP water was reduced due to reflection of incoming global radiation at the transparent plastic sheet. Reduction of net radiation in the SINVAP could have caused evaporation to be lower than open pan. The vapor pressure deficit followed the opposite trend of net radiation; as a result, the evaporation flux from the SINVAP with wire mesh has been increased. The elevated vapor deficit in the SINVAP with wire mesh could have caused evaporation to be higher than the open pan. This research found the average local wind run over the open pan was higher than the SINVAP inlet air flow. The nature of the local wind flow profile was unsteady and always fluctuated. However, the inlet air flow profile in the SINVAP was smooth, with little fluctuation. The smooth inlet air flow in the SINVAP was instrumental in transferring higher amount of water vapor molecules from the pan into the air. According to the findings of this study, the use of Chu et al., (2012) enhanced natural draft in the application fields of pond natural evaporation seems promising. The dimensions if chosen properly can thus substantially increase evaporation rates.