Thermal performance and efficiency of a thermosyphon heat pipe working with a biologically ecofriendly nanofluid

Thermal performance of a wickless thermosyphon heat pipe charged with a biologically-produced ecofriendly working fluid is experimentally studied. Biologically dependable process is a cheap and promising way for obtaining the high quality nanoparticles. Thus, in the present work, using the green synthesis, silver nanopartides are produced from the aqueous silver nitrate and the fresh tea leaf extract. The formation of Ag nanoparticles was observed by the change of color from colorless to dark brown by the addition of silver nitrate into the leaf extract and proved by SEM, TEM and XRD quality tests. Performing the two-step method, nanofluids at different weight concentrations were prepared, stabilized and used as working fluid inside the thermosyphon. The heat pipe was fabricated from the smooth copper tube with inner and outer diameters of 10.7 and 12 mm respectively and total length of 280 mm. Uniform heat flux was applied into the evaporator section using electrical cartridge heater and the condenser section was constantly cooled using ethylene glycol/water cooling jacket. Influence of different operating parameters such as applied heat flux to the evaporator section, filling ratio of working fluid, heat pipe inclination, nanoparticle concentration and response time on the thermal performance and efficiency of heat pipe was also experimentally studied and briefly discussed. Results showed that using the nanoparticles leads to the reduction in temperature distribution and enhances the thermal performance of heat pipe. (C) 2014 Elsevier Ltd. All rights reserved.