This paper presents the experimental results of the energy and enhancement efficiency characteristics of a decaying swirl flow generated by different radial guide-vane swirl generators. Energy and enhancement efficiency correlation equations were obtained for three types of swirl generator, which had differed from each other by the design of the deflecting element; swirl generator with conical deflecting element, with spherical deflecting element, and with no deflecting element. The enhancement efficiencies varied between 0.86-1.31 depending upon swirl intensity, Reynolds number and type of swirl generator. It was found that the enhancement efficiency increased with increasing vane angle, and decreased with increasing Reynolds number for all types of swirl generator. By comparing heat transfer enhancement efficiencies of each swirl generator, swirl generator with no deflecting element was found to have the highest heat transfer enhancement efficiency.