This paper is concerned with the enhancement of heat transfer by surfactants added to aqueous lithium bromide (LiBr) solutions. Three different kinds of tubes in horizontally stagged arrangement are tested with and without an additive of normal octyl alcohol. The test tubes are a bare tube, a floral tube and a hydrophilic tube. The additive mass concentration is about 0.05-5.5 wt%. The heat transfer coefficient is measured as a function of the solution flow rate in the range 0.01-0.034 kg m(-1) s(-1). The experimental results are compared with/without surfactants. Among three kinds of tubes, the hydrophilic tube shows the highest permeability. It has 4-73% higher wetted area than that of the bare tube, and 10-22% higher than that of the floral tube. Without surfactants, the hydrophilic tube is in the range 10-35% higher heat transfer coefficient than that of the bare tube, and 5-25% higher than that of the floral tube. With surfactants, the increase of the heat transfer coefficient is about 35-90% for the bare tube, 40-70% for the floral tube, and 30-50% for the hydrophilic tube.