| 摘要 |
PURPOSE:To make hardly the adhesion of dirt and maintain the high heat transfer of a spiral tube by a method wherein the shape of the tube is formed so that fluid in the tube advances under cutting the adhered substance on the wall surface of the tube by own force of the fluid at all times in the manner of the advance of a drill. CONSTITUTION:The shape of groove of the tube has a form similar to that of the groove of a drill and the edge angle A is within the range of 25-80 deg. but 40-45 deg. is the optimum. The deepest part of the groove is biased to one side and an angle B between the edge line of groove and a line drawn from the center of the tube is within the range of -20-30 deg. and 0-20 deg. is preferable. At least one groove is indented along the lengthwise direction of the tube in spiral. The angle of rotation C of the groove is within the range of 25-80 deg. and the angle within the range of 25-45 deg. is ideal for producing a whirling stream for cutting while the pitch of the groove is determined by the angle of rotation. The spiral groove of such shape is provided on a circular pipe, whereby the heat transfer surface may be kept in clean and the high heat transfer rate in the tube due to the whirling and turbulent flow effect of the groove may be maintained for a long period of time. |
