SU1453147A1 - Heat-exchanging tube - Google Patents

Abstract

Invention m. used in shell-and-tube apparatus. The purpose of the invention is to intensify heat transfer. The heat exchange tube 1 contains inside a wire helix 2 and a cylindrical insert 3 and a highly porous permeable cellular material placed inside helix 2. One flow — the portion of the heat carrier formed by the wire helix 2 —twists along a helical line to form the wall zone, and the other flow, moving axially in the cylindrical insert 3, it forms a core of an intensively mixing (pulsating) flow. In this case, an intensive exchange is carried out between the flows of the coolant of the near-wall zone and the core, 2 Il.

Description

. ...; .... . ... : - “m. -. .; ..: /../ ..... ,, .-- -; - .-. -; ;. . ..: ..; /:.-iV /...-:

"-" . . . . t I

 Г У-:: .. - -: .- -Л.; - .. 5 - /. : .u -;.: ..: -:: /. hl Ll / --v

ate

with

 h

Fig, 1

The invention relates to heat engineering, namely to the design of heat exchange tubes, and can be used as heat exchange elements of shell-and-tube devices,

The purpose of the invention is to intensify heat transfer.

FIG. 1 shows a heat exchanging pipe with a longitudinal section; in fig. 2 - the scanning of the near-wall zone in the region of the boundaries of the filtration and screw flow along the diameter of the insert.

The cushion tube 1 contains inside a wire helix 2 and a cylindrical insert 3 of highly porous permeable cellular material placed inside helix 2.

The heat exchange pipe operates as follows.

The coolant flowing through pipe 1 is divided into two streams. One flow, part of the coolant, formed by the wire helix 2, twists along a helical line to form a near-wall zone, and the other moving in the cylindrical insert 3 in the axial direction forms an intensely moving (pulsating) flow core.

By performing an insert 3 of highly porous cellular permeable material, an intensive exchange occurs between the flows of the coolant of the near-wall zone and the core, which is most pronounced when the axial component of the mean screw velocity V exceeds the mean velocity V of the coolant in the pores of slit 3, t. e. if

V,

V

(one)

in the area of the boundaries of the filtration and screw flow along the diameter D of the insert 3.

When the conditions are met (O and use of expressions

- -L1 -K 1. h / u f

 u cos oi. ;

   . ul h / sinoL 12 (U

(2) (3)

(four)

the diameter of the wire helix can be determined by the formula

0

five

0

five

0

five

5 where

 / AR 24K

 sin 2oL

(five)

h - f

u oi K 0

the pressure drop across the porous medium is equal to the pitch of the helix; spiral pitch,: coefficient of dynamic fluid viscosity; the flow rate in the direction of the helix is equal to the average velocity of the fluid in a flat slit gap; helix angle;

permeability coefficient of the insert;

insert porosity. Thus, the proposed design makes it possible to use the combined effect of the screw movement, the coolant in the near-wall zone with highly efficient mixing in the flow path, as well as between the flow core and the wall layer, which significantly intensifies the heat exchange in general, at relatively low flow rates of the coolant.

Claims (1)

Invention Formula A heat exchange tube with a wire helix inside, characterized in that, in order to intensify heat exchange, the tube additionally contains a cylindrical insert of highly porous permeable cellular material placed inside the helix. (e.Z