New effective oil coolers of expansion turbines for cryogenic equipment

conforming to the requirements of compactness, metal economy, operational reliability, and technological effectiveness. Oil coolers of expansion turbines use transformer or turbine oil cooled with water. Wateroil heat exchangers possess several features, important of which is the large difference (of tens of times) between the oil and water viscosities. Oil movement as a rule is laminar with a comparatively low heat emission coefficient. Water flow on the contrary is mostly turbulent and the heat emission coefficient in the water channels is quite high. Therefore, increased efficiency of the equipment and its reduced dimensions and weight are mostly dependent on intensifying heat emission in the oil channels. At present, oil coolers made of smooth straight tubes with oil flow inside the tubes are used in the low capacity expansion turbines (up to I0 kW). These designs are simple, reliable, and technologically effective but have a low heat emission coefficient in the oil channels [a = 200 to 300 W/(m2"K]).