SU1474435A1 - Heat-exchange tube - Google Patents

Abstract

Invention m. Used in vertical steam and condensation machines in the energy, chemical and food industries. The purpose of the invention is to intensify heat transfer during steam condensation. The pipe 1 has parallel grooves 2 on the outer surface of the pipe and the corresponding protrusions 3 on the inner surface. The grooves 2 cover the surface of the pipe 1 in a plane at an angle of 98 * 98 90 ° K OS and Truba. The distance between adjacent grooves 2 is equal to the triple groove width S = 3T, and the depth of the grooves is determined by the expression H 02 = √ ³ _{3G K * 98H / TX ρ SIN} Α x G, where G _K - condensate flow, the resulting surface of the pipe between adjacent grooves

* 98H - condensate viscosity

T - groove width

ρ is the specific density of the condensate

G is the acceleration of free fall. Between the grooves m. there are separate edges or grooves not communicating with them, oriented mainly parallel to the axis of the tubes. The design of the pipe reduces the average film thickness of the condensate around the perimeter of the pipe. 1 з.п f-ly, 1 ill.

Description

one

The invention relates to a power system and can be used in vertical steam and condensation units used in the power industry, chemical and food industries.

The purpose of the invention is to intensify heat transfer during steam condensation.

The drawing shows a heat exchanger tube.

The heat exchange tube 1 has on its outer surface closed parallel grooves 2 and the corresponding protrusions 3 on the inner surface of the tube. Grooves 2 grab the surface of the pipe in a plane located at an angle of 90 ° to the axis of the pipe. The heat exchange tube has the following geometrical characteristics: the distance between the grooves S, the width of the grooves t, the depth of the grooves h.

The heat exchange pipe operates as follows.

Condensate resulting from condensation of steam on the outer surface of the vertical pipe 1 flows into the grooves 2 and is discharged along them to one side of the pipe. As a consequence, the average film thickness around the perimeter of the pipe is reduced, which provides for the intensification of heat transfer during vapor condensation.

The theory of heat transfer during steam condensation allows us to determine the optimal geometric characteristics of this pipe design to ensure its maximum thermal efficiency during operation. The magnitude of the heat transfer coefficient oir during steam condensation on vertical smooth pipes depends on the height of the pipe L:

oir

I1 L1

Periodic drainage of the condensate by the grooves actually reduces the height of the vapor-condensing surface to the distance between the grooves, for this case the heat transfer coefficient σ k is determined:

Due to the fact that the condensate filling groove does not practically participate in the heat exchange, the effective length of the heat exchange tube is less than the length

oh and

14744352

smooth pipe of the same height

t.

0

about

Hence, the magnitude of the intensification of heat transfer dk upon condensation of steam on the outer surface of the proposed pipe, as compared with smooth, determines:

(L- 5i - t) .i

eU 4GG

 Is

V

S + t

ifDL

 D

15

about

 W

(one &

Differentiating this equation no S. And equating to the first derivative zero, it is determined that the maximum intensification of heat transfer is achieved with a distance between the grooves equal to three times the width of one groove:

S 3t.

The geometrical dimensions of the grooves width t, depth h and angle of inclination relative to the pipe axis can be determined on the basis of the condition on the pipe surface between adjacent grooves C „

Jk

c

)

p. sinoi-g

Where

- viscosity of condensate; p is the specific density of the condensate;

g - free fall acceleration.

Heat transfer intensification can be increased by placing additional grooves or fins in the pipe sections between the grooves, oriented mainly parallel to the pipe axis, which increase the heat transfer efficiency due to the effect of surface tension forces. Moreover, these grooves or ribs should not be connected with closed grooves in order to ensure regular condensate drainage to one side of the pipe.

Claims (2)

1. A heat exchange tube having parallel grooves on the outer surface of the pipe and corresponding protrusions on the inner surface, characterized in that J1474435 In order to intensify heat transfer during steam condensation, the grooves cover the surface of the pipe in a plane at an angle to the pipe axis 5, the distance between adjacent grooves being three times the width of the groove S 3t,   | 3 " 1g p sinot g where g k - consumption of condensate formed on the pipe surface 0 } - t Р- g between adjacent grooves; condensate viscosity; groove width; specific condensate density; free fall acceleration. 2. A pipe according to claim 1, characterized by the fact that there are separate edges or grooves not communicating with them between the grooves, oriented mainly parallel to the axis of the pipe.