T. Moontree, S. Rittidech, S. Thongdaeng, Thermosyphon Heat Exchanger for Cooling of Hydraulic Oil in Sugarcane Harvester, Research Journal of Applied Sciences, Volume 11,Issue 1, 2016, Pages 1-6, ISSN 1815-932x, rjasci.2016.1.6, (https://makhillpublications.co/view-article.php?doi=rjasci.2016.1.6) Abstract: This research aims to study the application of a thermosyphon heat exchanger for cooling of hydraulic oil in sugarcane harvester. The objective was to control hydraulic oil temperature to reduce an over-heat problem for the engine and the hydraulic system. The thermosyphon heat exchanger was made of 90 copper tubes with inner diameter of 18 mm. The evaporator and condenser section length were equal to 200 mm and adiabatic section length of 100 mm. R134a, ethanol and water were used as working fluids with a filling ratios of 30, 50 and 80% by total volume. The air flow rate inlets at the condenser were 2.3, 2.6 and 2.8 m sec-1. In the testing, hot hydraulic oil passed through the evaporator section and air passed through the condenser section. The results show that the thermosyphon heat exchanger reduced the hydraulic oil temperature from 80 to 62°C. The maximum heat transfer rate and effectiveness were occurred as an air velocity of 2.3 m sec-1 with R134a as working fluid and filling ratio of 50% by total volume. Keywords: hydraulic system;Sugarcane harvester;Themosyphon