A heat exchanger is provided with a first conduit which utilizes a reverse spiral concept and a second fluid conduit which directs a fluid in thermal communication with the first conduit. One of the fluid conduits of the heat exchanger is formed with a generally S-shaped portion which creates a reverse...http://www.google.com.hk/patents/US4883117?utm_source=gb-gplus-share專利 US4883117 - Swirl flow heat exchanger with reverse spiral configuration
