Semnan province with a total area of 296000 km² is the sixth biggest province in Iran. The evaporation rate in this province is high and can be more than 2000 ml in the year. This province suffers from water shortage and drought. To make use of evaporation capacity, in this paper the impact of solar radiation intensity on the performance of single-slope solar desalination still was investigated. The solar radiative flux depends on geographical location, season, and time. In this study, the dimension and temperature of the basin are fixed and the radiation intensity of different times in April in Semnan province is investigated. To do this, the three-dimensional humid air models in the laminar and steady form are used for internal flow and the laminar flow model is used for the external flow. The accuracy of the numerical method has been evaluated using different models and experimental data for the average Nusselt number on water surface and production rate of water. Results showed calculations have acceptable accuracy. Results also indicate that the variation trends for radiation intensity are similar to the production rate. The maximum water production rate belongs to 12 o'clock with a 5.6% increase in comparison with 7:00 AM., which has the lowest evaporation rate.

塞姆南省总面积 29.6 万平方公里²是伊朗第六大省。本省蒸发量高，年蒸发量可达200​​0毫升以上。这个省缺水和干旱。为了利用蒸发能力，本文还研究了太阳辐射强度对单坡太阳能海水淡化性能的影响。太阳辐射通量取决于地理位置、季节和时间。本研究将流域的尺度和温度固定，调查了Semnan省4月份不同时间的辐射强度。为此，层流和稳态形式的三维湿空气模型用于内部流动，层流模型用于外部流动。数值方法的准确性已使用不同模型和实验数据对水面平均努塞尔数和产水率进行了评估。结果表明计算具有可接受的准确性。结果还表明辐射强度的变化趋势与生产率相似。最大产水率属于12点钟，与蒸发率最低的上午7:00相比增加了5.6%。