Researches on New Heat Transmitting Tubes : 1st Report

Abstract

In order to elevate the heat transmission capacity of circular tubes which are most common as heat transmitting tubes, many devices have been made on the surfaces of tubes. From our consideration on heat transmitting tubes, we got heat transmitting tubes of a new type, which are superior in point of heat transmission in case of fluid flowing across the tubes and are equipped with one or two fins stretching in axial direction on the outer surfaces of circular tubes. Now we will report our researches (1 st∼3 rd reports) on new heat transmitting tubes in the lump. The results of our researches are as follows. 1) The most excellent characteristic in heat transmission is attained with the tube which has two fins stretching in axial direction on its front surface and holding the angle 2θ=40°between them against the outer flow of air. In this case more than 50% increase of heat transmission may be expected. 2) These tubes, used as a bundle in staggered arrangement of suitable spacings of tubes, produce the highest coefficient of heat transfer and the lowest pressure loss.