Akilan T., Raja L., Hariharan U.

Research on the effectiveness of noise reduction when encoding a lossless speech signal

Solar cooling systems are the energy-saving technologies and are aimed at combating climate change. These systems are the most promising for thermal comfort and storage of agricultural and pharmaceutical products in regions with hot climate. A mathematical model developed describes processes of radiative and convective heat transfer in the collector of combined type with selective coating, providing both absorption of solar radiation heat by day and radiation of heat into outer space at night. The study of operation modes for the collector of the combined type was performed for the weather conditions of the Bamako city, the capital of the Republic of Mali, with a semi-desert climate and a large potential of solar radiation during the year. According to the results of modeling, the dependencies of temperature changes in the storage tanks of 100 liters’ volume for heated and chilled water in the daytime and nighttime operating modes at different flow rates of the coolant were established. For example, it is shown that in a daytime operating mode the thermal efficiency of a 1.8 m² collector is 73 % at a water flow rate of 0.02 kg/s and water temperature in the tank reaches 82 °C in six hours after sunrise. In night mode of operation at a water flow of 0.004 kg/s, the temperature drop overnight in the tank is 6° C for the estimated heat flux from the collector of 34 W/m². Results of calculations according to the developed mathematical model are initial data for analyzing the possibility of using combined type collector as a part of helium-absorption refrigeration machine.