In this paper we evaluated the performance of a helix tube solar collector. This helix tube collector increases the absorbed radiation of diffuse and ground reflection. The inner and outer diameters of the helix tube are 8 and 12 mm, respectively. The helix tube was designed as a copper tube which is coated with a nanocarbon composite. A cylindrical glass, length 1.2 m, outer diameter 1.397 x 10(-1) m and thickness 6.4 x 10(-3) m was used as a cover. The performance of the collector was in Phitsanulok province, Thailand, which is located at latitude 16.783 degrees N with an average wind velocity of 3 m s(-1). Solar absorbance was 0.94 and the IR emission of nanocarbon was 0.15. The heat transfer fluid was Paratherm MG (TM) oil at 32 degrees C and the oil mass flow rate was 9.5 kg h(-1). These were used to evaluate the performance of the collector. The performance of the helix tube collector and the temperature difference of oil (inlet and outlet) were 50.32% and 47.43 degrees C, respectively. Copyright (C) 2007 John Wiley & Sons, Ltd.