Abstract: Disclosed is a producing method which allows low-cost and highly productive production of a seamless tube with a grooved inner surface having a smooth outer surface and an inner surface formed with plural types of grooves such that a protrusion is not formed at the produced seamless tube with a grooved inner surface. The tube is reduced in diameter by using a die and a plug. Then, the outer surface of the tube is pressed against a grooved plug by means of a pair of rolls such that a groove is formed in a portion of the inner surface of the tube. The process flattens the cross-sectional configuration of the tube in the direction in which the tube is pressed with the rolls. Subsequently, a sizing process using a die is performed with respect to the tube such that the tube has a generally circular configuration.

Abstract: A heat transfer tube for a falling film type evaporator, in which water spreading characteristics, particularly the water spreading characteristics in the tube axis direction, enhancing the heat transfer ability. Three types of projections 2, 3, and 4 are formed on an external surface 1a of a heat transfer tube body 1. A respective plurality of projections 2 to 4 are arranged spirally in parallel to one another, forming projection groups 2a to 4a. The number of each projection group 2 to 4 is one. Pitches P2 to P4 for the projections 2 to 4 are in the range of 0.35 mm≦P4<P3<P2≦5.95 mm. Heights h2 to h4 of the projections 2 to 4 are in the range of 0.1 mm≦h4<h3<h2≦0.5 mm. Pitches for the projection groups 2a to 4a is in the range of 0.72 to 1.12 mm.

Abstract: An apparatus for producing an internally grooved seamless tube by rolling. The apparatus has pressing rolls 3 and back-up rolls 20, which work with a constant load under control by the load detector 21 to form uniform grooves without breaking the mother tube.

Abstract: Disclosed is a producing method which allows low-cost and highly productive production of a seamless tube with a grooved inner surface having a smooth outer surface and an inner surface formed with plural types of grooves such that a protrusion is not formed at the produced seamless tube with a grooved inner surface. The tube is reduced in diameter by using a die and a plug. Then, the outer surface of the tube is pressed against a grooved plug by means of a pair of rolls such that a groove is formed in a portion of the inner surface of the tube. The process flattens the cross-sectional configuration of the tube in the direction in which the tube is pressed with the rolls. Subsequently, a sizing process using a die is performed with respect to the tube such that the tube has a generally circular configuration.

Abstract: A heat transfer tube for a falling film type evaporator, in which water spreading characteristics, particularly the water spreading characteristics in the tube axis direction, enhancing the heat transfer ability. Three types of projections 2, 3, and 4 are formed on an external surface 1a of a heat transfer tube body 1. A respective plurality of projections 2 to 4 are arranged spirally in parallel to one another, forming projection groups 2a to 4a. The number of each projection group 2 to 4 is one. Pitches P2 to P4 for the projections 2 to 4 are in the range of 0.35 mm≦P4<P3<P2≦5.95 mm. Heights h2 to h4 of the projections 2 to 4 are in the range of 0.1 mm≦h4<h3<h2≦0.5 mm. Pitches for the projection groups 2a to 4a is in the range of 0.72 to 1.12 mm.

Abstract: A tube having a grooved inner surface capable of achieving high condensing performance and high evaporating performance even in a region of a small flow rate of a refrigerant and preferable as a heat exchanger tube for a condenser as well as an evaporator and its fabrication method, wherein spiral groove fabricating zones 1 formed with spiral grooves are arranged at an inner surface of a metal or an alloy tube and intersecting groove fabricating zones 2 formed with intersecting groove groups intersected with pluralities of grooves are arranged at the inner surface of the metal or the alloy tube at regions different from each other, singles or pluralities of the spiral groove fabricating zones 1 and the intersecting groove fabricating zones 2 are alternately arranged in a tube circumferential direction of the metal or the alloy tube, when a fabrication width of the spiral groove fabricating zone 1 in the tube circumferential direction is designated by W1 and a fabrication width of the intersecting groove fabri

Abstract: In boiling heat transfer tube, fins 2 are provided on an outer surface of the tube body 1 in a manner such that the fins 2 each extend in a peripheral direction of the tube and a direction inclined to the tube axis at a pitch P2 in the tube axial direction. Protrusions 4 and recesses 5 are alternately formed in a length direction of a fin, a protrusion coming after a recess or vice versa, by being pressed. Opening 6 widths at the top ends of the cavity 3 between an adjacent pair of fins 2 are narrowed by inward jutting-out of the fins at both recesses 5 and protrusions 4. A profile of each of the protrusions in section perpendicular to the tube axis assumes a trapezoid. An opening width (W) between protrusions in section including the tube axis is 0.13 mm<W ≦0.40 mm, an angle (&thgr;) formed between opposed side surfaces of each recess in section perpendicular to the tube axis is 55 degrees or less. A pitch (P1) of the recesses or the protrusions in section perpendicular to the tube axis is 0.

Abstract: An absorption chiller that uses an aqueous salt solution as an absorbent and water as a refrigerant, the absorption chiller including an evaporator that allows the water to trickle or flow downward onto the outer surface of a heat exchanger tube installed horizontally or approximately horizontally, an absorber that allows the aqueous salt solution to trickle or flow downward onto the outer surface of a heat exchanger tube installed horizontally or approximately horizontally, and a condenser that allows the water to be supplied onto the outer surface of a heat exchanger tube installed horizontally or approximately horizontally. At least one of the heat exchanger tubes is provided, on the inner surface thereof, with protruded threads formed in a spiral fashion. A plurality of rows of projections of a height of 0.2 to 0.4 mm with flat portions on the top is provided on the outer surface of the tube successively at a pitch of 0.4 to 0.8 mm between projections.

Abstract: A heat exchanger tube includes ribs formed in protrusion on an internal surface of the tube and extending spirally with a suitable distance between adjacent ribs, concavities formed on the external surface of the tube and extending spirally with a suitable distance between adjacent concavities, and a plurality of independent projections formed on the external surface of the tube and laid out spirally. The projections are formed with a recess on their top surfaces in such a way that a portion aligned with the ribs on the internal surface of the tube is lower than a portion aligned with an area between the ribs. Further, the concavities on the external surface of the tube and the ribs on the internal surface of the tube are formed at mutually aligned positions.

Abstract: To provide a heat transfer tube for an absorber in which the quantity of residence of an absorbing liquid on the surface of the tube staying in trough portions is large, and the staying absorbing liquid is thinly and widely spread on the surface of the tube to materially promote an absorbing performance. On an outer surface of a metal tube having an outer diameter of D, a group of N (N is a natural number) number of trough portions, wherein the length L1 in a longitudinal direction of the tube is 70 mm.ltoreq.L1.ltoreq.130 mm, and the depth H is 0.23 mm.ltoreq.H<0.5 mm, is formed on a circumference of a circle formed in section of the tube in the case of being cut perpendicular to a longitudinal direction of the tube so that the pitch P (=.pi. D/N) is set in the range of 6.2 to 8.

Abstract: Disclosed is a heat transfer tube with grooves in an inner surface thereof, which is excellent in both evaporation performance and condensation performance. In the heat transfer tube with grooves in an inner surface thereof according to the present invention, groove processing regions 1 having a width W1 and groove processing regions 2 having a width W2 are alternately arranged in the inner surface thereof, and a linear groove region 3 having a width W3 extending in a longitudinal direction of the tube is arranged between the groove processing region 1 and the groove processing region 2. The width W1 is larger than the width W2. A group of grooves within the groove processing region 1 are helically formed at a torsional angle .theta.1 with respect to a longitudinal direction of the tube, and a group of grooves within the groove processing region 2 are at a torsional angle .theta.2 different from .theta.

Abstract: An inner grooved tube forming apparatus capable of manufacturing an inner grooved tube with a stable quality by reducing the weight of each member and improving the durability to allow high-speed rotation of a planetary ball die. A grooved plug 12 is fixed to the front end of a mandrel 11, and is in contact with the inner surface of a mother tube 10. Balls 13 are in contact with the outer surface of the mother tube 10. The balls 13 are accommodated inside a ball track retaining outer ring 14. A ball retainer 20 is provided inside the outer ring 14 to retain the balls 13. The outer ring 14 is fixed to a rotating shaft 19 by a cylinder 16 and a front cap 17. A bearing 21 is mounted inside the cylinder 16, and a support member 22 is rotatably supported through the bearing 21 to the cylinder 16. The outer ring 14 and the support member 22 are formed of ceramic, and the ball retainer 20 is formed of synthetic resin.

Abstract: An inner grooving process for the tube expanding rolling type by which inner grooves such as wide width grooves or deep grooves which cannot normally be formed readily can be formed with a high quality using an equipment of a simple structure without deteriorating the operability. In the process, a drawing die having an exit hole of a fixed diameter and a floating plug having no bearing portion thereon are used. The floating plug and a grooved plug connected for rotation to the floating plug and having an outer diameter smaller than the diameter of the exit hole of the drawing die are inserted into a metallic tube and then the grooved plug is drawn to a location of the rolling member into the metallic tube by drawing and then retained at such location.