Examination of a solar desalination system equipped with an air bubble column humidifier, evacuated tube collectors and thermosyphon heat pipes

In this paper, the performance of a novel HDH solar desalination system equipped with a combination of heat pipe (HP), evacuated tube collector (ETC) and air bubble column humidifier is experimentally investigated. This novel HDH system uses advantages of ETC-HP as a highly efficient thermal absorption and conductor device, and at the same time employs the advantages of an air bubble column humidifier, i.e. high interface area and effective mixing in order to heat the water and humidify the air, respectively. The effects of various parameters including incoming air flow rate into the humidifier, initial depth of water in the humidifier, and adding fluids such as oil and water in the space between the ETCs and heat pipes on the system performance were investigated. Results indicate that by adding oil in the space between the ETCs and heat pipes, daily fresh water productivity and daily efficiency increase significantly and reached 6.275 kg/day·m2 and 65%, respectively. In addition, the optimum initial water depth in the humidifier is the same as the length of the heat pipe's condenser section in the humidifier. Moreover, daily production slightly increases as the air flow rate increases. The estimated cost of fresh water produced through the HDH system designed is 0.028 $/L.