Abstract: A heat insulating pipe has a foamed heat insulating layer on its outer circumferential face in which the heat insulating layer has an expansion ratio of at least 4 and is of a three-layered structure consisting of a middle foamed layer and lower and upper foamed layers formed at both sides of the middle foamed layer. The cells of the middle foamed layer are relatively large. The cells of the upper foamed layer and the lower foamed layer are relatively small. The shapes of the cells of the middle foamed layer are such that, for the average cell diameter (.mu..sub.1) measured in the radial direction of the pipe and the average cell diameter (.mu..sub.2) measured in the axial direction of the pipe, the relation of .mu..sub.1 /.mu..sub.2 =0.3-0.9 holds.

Abstract: A method for manufacturing a heat insulating pipe having a foamed insulating layer around the outer surface of said pipe. The foamed insulating layer has an expansion ratio of at least 4. It has three integral sub-layers, said sub-layers including a cellular middle foamed sub-layer which is integral with a cellular inner foamed sub-layer and a cellular outer foamed sub-layer, said inner and outer sub-layer being on opposite sides of said middle sub-layer, said cellular inner foamed sub-layer being the innermost sub-layer with respect to said pipe and surrounding the outer surface of said pipe. The cells of said inner and outer sub-layers are smaller than the cells of said middle cellular sub-layer, the ratio .mu..sub.1 /.mu..sub.2 of the cell dimensions of said cellular middle sub-layer are between 0.3 and 0.9, wherein .mu..sub.1 is the average cell dimension measured in the radial direction of said pipe and .mu..sub.2 is the average cell dimension measured in the axial direction of said pipe.

Abstract: A heat transfer tube for condensation easily obtainable through an additional machining process applied to a low fin tube and a method for manufacturing the same. There is formed a toothed wheel-like part having mountain and valley parts alternately and continuously arranged on the outer circumferential fin part of the low fin tube. Each of the mountain parts is formed into a pyramid-like shape having a transverse cross section of approximately a long snare hand drum-like shape in which longer sides are disposed along grooves provided between the fins of the tube and are arranged to be concave curvatures each resembling an arc. The two slanting faces of the mountain part including these longer sides of the pyramid-like shape gradually and smoothly slant from the top of the pyramid to the bottom thereof. The heat transfer tube for condensation is manufactured by carrying out a transforming process applied to the outer circumference of fins of a low fin tube in the longitudinal direction of the fin tube.

Abstract: A molten metal surface level in a mold type continuous casting machine is controlled with an improved responsiveness and high accuracy by means of a novel electrical control system comprising a servo mechanism incorporating a microcomputer or the like, means for processing an input signal thereto from a detector means at the molten metal surface to feedback thereto a controlling output and, optionally, an ITV camera for photographing the molten metal surface portion to produce binary-coded signals through a suitable processing means so that the molten metal surface level can be detected and controlled with higher accuracy.

Abstract: The invention is concerned with a heat transfer tube for use in boiling type heat exchangers, having an excellent heat transfer performance. More specifically, the invention relates to a surface condition of the heat transfer tube for improving the heat transfer performance and a method of producing the tube easily, especially a method for processing the surface condition efficiently and advantageously from an industrial point of view. The essential feature of the invention resides in a provision of a surface condition for promoting the boiling which consists of annular or spiral cavities extending along the tube surface in the circumferential direction of the latter, as well as narrow gaps extending along the cavities so as to allow the cavities to communicate the outside space. If necessary, spiral or annular fins may be provided on the tube surface, so as to improve the boiling performance at the outside of the tube.

Abstract: In a molten metal surface level detection system, the use of conventional detector means is eliminated and, instead, an ITV camera is provided at an appropriate place where it is neither thermally affected by the molten metal surface portion nor obstructs the site jobs and the molten metal surface portion is photographed by said ITV camera along a direction permitting the surveillance of the level of the molten metal surface and, then, the thus photographed image of the molten metal surface portion is processed in a suitable manner for accurately and reliably detecting the surface level thereof.