JPS5913897A - Heat exchanger - Google Patents

Abstract

PURPOSE:To separate a condensed liquid on a thermal conduction surface, to thin a liquid film, and to improve a heat transfer efficiency, by attaching slanted plates to the outer surface of heat transfer pipes, vertically installed, of a condensation type heat exchanger. CONSTITUTION:Slanted plates 12 with an inclination phi are installed at distances P to the outside of a heat transfer pipe 11. This causes the condensed liquid of a condensed liquid film 23 on the surface of the heat transfer pipe 11 to flow in a specified direction over the surfaces of the slanted plates 12 and to drop only from the lower ends of the slanted plates 12, and enables the liquid film 23 to be formed thin. In which case, the inclination phi and the distance P are set to a specified value determined by a condensing quantity, the outer diameter of the heat transfer pipe 11, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger, and more particularly to a condensing type heat exchanger in which the secondary medium is a condensable gas and which is suitable for condensing gas on a heat transfer surface and exchanging heat.

In a condensing heat exchanger, the heat exchange efficiency mainly depends on the thickness of the liquid film on the heat transfer surface formed by condensation of gas, which is the primary medium. In order to reduce the thickness of the liquid film and improve heat exchange efficiency, most heat transfer tubes are installed horizontally. If the heat exchanger tubes are installed horizontally, the installation area becomes large, so if there are restrictions on the installation area and restrictions on the condensed gas supply source, which is the secondary medium, it is necessary to install the heat exchanger tubes vertically or at an angle.

However, in this case, the thickness of the liquid film on the heat transfer surface becomes thick and the heat exchange efficiency decreases, so it is necessary to increase the cross-sectional area of all the heat transfer surfaces, which has the disadvantage of increasing the size of the heat exchanger.

The purpose of the present invention is to improve heat exchange efficiency in a heat exchanger in which heat exchanger tubes are installed vertically or at an angle, and to provide a heat exchanger with a small heat transfer area, small size, and the same size as conventional heat exchangers. The purpose is to provide an exchanger.

In the present invention, in order to couple the above objects, the heat exchange efficiency mainly depends on the thickness of the liquid film on the heat transfer surface formed by the condensation of gas as the primary medium. Arranged on the outer surface of the heat tube at an interval p of inclined sheet metals inclined with respect to the horizontal direction, S is provided in the front oblique direction on this inclined plate surface, and the condensed liquid on the heat transfer surface is collected by the inclined plate and passes through the groove of the inclined plate surface ILj4. By discharging in a fixed direction, the liquid film on the heat transfer surface can be reduced in minutes.
B. Decrease the average liquid film thickness.

The principle of the present invention will be explained below with reference to FIGS. 1 and 2. , FIG. 1 shows the heat transfer mechanism in the heat transfer tube 11 in /J'4. The primary medium 21 which is a condensable gas is the heat exchanger tube 11
It condenses on the surface, becomes a liquid film 22, and the surface of the heat exchanger tube 11 iMi
to fall. The secondary medium 24 on the low temperature side is passed through the heat transfer '#11. At this time, total heat transfer! Q.

can be expressed by the following formula.

QT=−At・(Tl'I'2)
-... (1) Here, lg: heat member fM, rate r; total surface area (total heat transfer area) of heat transfer tube 11 T1 temperature of secondary medium 21 T2: i crystal of secondary medium 24 Summer hla: Heat transfer rate h6 on the inner surface of the heat exchanger tube 11. ．． ．． : Heat transfer coefficient on the outer surface of the heat transfer tube 11 tD: Thickness of the heat transfer blue 11 λD; Heat transfer [°11th thermal conductivity 1() is the total thermal resistance, (1/h+fi) is the thermal resistance on the inner surface of heat transfer v11, (1D/λp) is the thermal resistance of heat transfer tube 11, (1/''
eat) indicates the thermal resistance at the outer surface of the heat transfer dll. In formula (1), it is clear from the opening formula that the purpose of use of the secondary sister body 24 is V on the left (Ding IT2> Kuyu shell); To make the heat exchanger the host without letting it go down (preferably 5 + fiat gold), 'C' is a peace of mind that goes into the heat exchanger 0.
゜By the way, A: 2 at (2), 45N-111 outside m
tD W resistance (1/h-1) l'L-tkQc slag heat 'Ill inner thermal resistance (1/11 quantity,) approximately io.

Since the heat of the heat exchanger tube 11 is 910 times smaller than the enemy (tD/λD), the raw heat resistance (1/K)k is reduced/) VCV
i m A'l Tetsu 11 Thermal resistance of the surrounding area (1/h-at)
It's so sad and childish to make pebbles. In other words, in order to downsize the heat exchanger, the heat transfer coefficient Ω on the outer surface of the heat exchanger tube 11 is required.

, 1 can be increased. This heat is h-otic,
Transmission pp, -t t '10I] 上 oOy 22 It depends on the thickness of the t, and it is known that the total of 1 song in the material bone is 1 song, and the ↓ sea urchin clothes V can be made. 7.

+A δ+ , :c(L o /sin Q)
-・= -(4) Here, λf: Thermal conductivity of the condensate δf: Thickness of the liquid film 22 at the lower end of the heat exchanger tube 11 LD: Length of the heat exchanger tube 11 0: Inclination angle formula of the heat exchanger tube 11 ( 3) and (4) To increase and increase the heat transfer coefficient h ant , shorten the length LD of the heat transfer tube 11 and reduce the liquid film 22.
What is necessary is to reduce the thickness δf.

FIG. 2 illustrates the principle of the invention. In the present invention,
The liquid film 22 on the outer surface of the heat transfer tube 11 is separated by installing inclined plates 12 having an inclination ψ at a distance p outside the heat transfer tube 11.
Improve heat transfer coefficient. The heat transfer coefficients b and f at this time,
The heat transfer coefficient f h in the heat exchanger tube 11 without the inclined plate 12. Then, from equations (3) and (4), we get the following.

FIG. 3 shows an example of the effect of the principle of the present invention, in which the length of the heat exchanger tube 11 L p = 2 m, the outer diameter D =
12 mm, wall thickness ja = 1 mm, the material is stainless steel, the secondary medium 21 is steam at 280C, and the heat transfer coefficient without the inclined plate 12 is K.

Finally, the heat X flow rate according to the present invention is shown. When the interval p between the inclined plates 120 is reduced, the thermal conductivity I(,) decreases due to the mutual interference of the inclined plates 12.As shown in FIG. ~
It can be improved by 2.0 times, and the total heat transfer area can be reduced to 85 to 50%.

Embodiments of the present invention will now be described with reference to FIGS. 4, 5, and 6. The embodiment shown in Fig. 4 is an application of the principle of the present invention shown in Fig. 2 to a general heat converter, and the embodiment shown in Fig. 5 is an application of the principle of the present invention to a heat exchanger for a nuclear reactor. As an example, FIG. 6 is a detailed view of the heat exchange section.

In the embodiment shown in FIG. 4, the primary medium 2 is a condensable gas.
1 flows into the heat exchanger main body container l from the primary medium population 15, condenses on the surface of the heat exchanger tubes 11, and causes the heat exchanger tubes 11 and the inclined plate 1
2 and flows out from the secondary medium outlet 16. The secondary medium flows in from the secondary medium port 13, passes inside the heat transfer tube 11, is heated, and flows out from the secondary medium outlet 14. Since the heat exchanger according to this embodiment is vertical, it is effective in cases where the installation area is small.

In the embodiment shown in FIG. 5, steam (i.e., secondary medium) generated in the core 4 of the nuclear reactor rises inside the shroud 3 and accumulates in the steam dome 6. Steam Dome 6Vcfc, Wait-
The secondary medium 21 condenses on the surface of the heat exchanger tube 11, falls along the heat exchanger tube 11 and the inclined plate 12, descends outside the shroud 3, and returns to the core 4. The secondary medium flows from the secondary medium port 14 downwardly through the ladder 17 into the heat transfer tubes 11, is heated and exits through the upper header 18 through the secondary medium outlet 18.

In this case, the reactor vessel 2 also serves as a heat exchanger main body vessel. In a nuclear reactor, the reactor vessel 2 is vertical, so it is more advantageous to install the heat exchanger tubes 11 vertically or inclined, as in the present invention, than to install the heat exchanger tubes 11 horizontally.

FIG. 6 is an enlarged detailed view of the heat exchange section in the embodiment shown in FIGS. 4 and 5. FIG. The primary medium condensed on the outer surface of the heat exchanger tube 11 descends as a full liquid film 22 on the outer surface of the heat exchanger tube 11, flows on the upper surface of the inclined plate 12 arranged at the interval p, and falls from the lower end of the inclined plate 12. Similar to the inclined plate 12VC, there is a conventional vibration isolation plate for the heat transfer tube 11, but the vibration isolation plate is installed horizontally.In this case, the ground primary medium falls from both ends of the vibration isolation plate and gas This prevents the primary medium from reaching the surface of the heat exchanger tube 11, thereby deteriorating the heat exchange efficiency. Therefore, the liquid film 22 on the outer surface of the heat transfer tube 11 is separated and the liquid film 2
2, the angle ψ of the inclined plate 12 must be selected so that the liquid film 23 on the inclined plate 12 flows in a fixed direction and falls only from the lower end of the inclined plate 12.
, the lower limit value ψ of the inclination angle ψ for dropping only from the lower end of the inclined plate 12 is given by the following equation based on the rate of descent of the liquid film on the inclined plate surface.

・・・・・・・・・(6) Here, WI: Amount of condensation of the primary medium between the inclined plates 12 Ap: Area of the inclined plate 12, : Length in the inclined direction pr of the inclined plate 12, : Transmission Arrangement pitch D of heat tubes 11 : Outer diameter νf of heat transfer tubes 11 : Kinematic viscosity coefficient ρf of condensed primary medium = Close injection of condensed primary medium, that is, there is a configuration in which the inclination angle ψ of the inclined plate 12 satisfies the following formula. .

,〉ψ, ・・・
(For example, if heat transfer 1ti is made of stainless steel,
Length LD = 2m, outer diameter p = 12mm, wall thickness t, = 1m+
Assuming
C% If the average temperature of the secondary medium is 260C, the total heat exchange amount is Q = 1.3 x 10" Kcal from equation (1)
/8, and the amount of condensation is wt = 0.84Kp/8. In addition, from the heat exchanger tube arrangement with pitch pD = 20 mm and the slope plate length ■,, = 0.2 m, the slope plate area is 1 person, =
0.4i, and from equations (6) and (7), the inclination angle ψ may be set to 1.2 x 10-'ra'd (0.7 degrees) or more.

Also, total heat exchange amount 1.3 x 103Kcal/S
is the total heat exchange Ji0.93XlO when there is no inclined plate 12
'Kcal/S is 1.4 times. That is, according to the present invention, in order to obtain the same heat exchange and stitching, the total heat transfer area can be reduced to 70% of the conventional heat exchanger according to equation (1), making it possible to downsize the heat exchanger.

FIG. 7 is a partially enlarged view showing another embodiment of the present invention.

This embodiment is characterized in that an inclined plate 12 is provided in a spiral shape on each heat exchanger tube 11 shown in FIGS. The primary medium that has condensed into a liquid film 22 is collected on the inclined plate 12, and its waste is discharged. Similar to this embodiment, there are fins such as a fuel spacer of a fast breeder reactor shown in FIG. 8 and a cooler shown in FIG. 9. The fuel spacer 6 shown in FIG. 8 is for maintaining a constant distance between adjacent fuels 1115, and when this fuel spacer 6 is applied to the inclined plate 12 shown in FIG. The fins 7 shown in FIG. 9 are generally used when the primary medium is a non-condensable gas and are intended to widen the heat transfer area. Although it is possible to divide the liquid film 22 in the JJA meeting where this fin 7 is applied when the primary medium is a condensable gas,
This prevents droplets from falling from various places and condensable gas, which is a primary medium, from reaching the surface of the heat transfer tube 11. Therefore, when the secondary medium is a condensable gas, it is necessary to form a groove in the inclined plate 12 to collect and discharge the condensate to a predetermined position, as in the embodiment of the present invention shown in FIG. be. The condition for discharging the collected condensate to the lower end of the heat transfer tube 11 is such that the width of the groove formed by the inclined plate 12 is d and the height H satisfies the following formula.

Here, WD: heat transfer - g, the amount of condensation of the primary medium in one bottle, and other conditions are the same as in equation (6).

For example, heat transfer '#11 is made of stainless steel and is long.

22m1 outer diameter D = 12mm, wall thickness tn'' = 11n!R, pitch of inclined plate p = '0.25FFI (angle of inclination ψ = t
an-'(p/π0)ki1.42 rad (81[)
), width b = 3, negative medium temperature 280C, secondary medium average temperature 260C, then from equation (8) the height H
may be 0.4 mrR or more. In this case as well, the heat transfer coefficient increases as in FIG. 3, and the heat transfer area can be reduced.

According to the present invention, the condensate film formed on the outer surface of the heat transfer tube can be divided by the inclined plate, and the condensed liquid collected on the inclined plate surface can be discharged to a predetermined position. 85 to 50 of the total heat transfer area can be increased by 1.2 to 2.0 times
%.

[Brief explanation of drawings]

Figure 1 is a partial sectional view showing the mechanism of condensation heat transfer, Figure 2 is a principle diagram showing the principle of the present invention, Figure 3 is a diagram showing the effects of the present invention, and Figures 4 and 5 are the invention of the present invention. 6 is a partially detailed view of the implementation row of FIGS. 4 and 5; FIG. 7 is a partially detailed view of another embodiment of the present invention (+IJ); FIG. Fig. 9 is a partially detailed diagram showing a conventional technique similar to the embodiment shown in Fig. 7.

Claims (1)

[Claims] 1. A heat exchanger having vertical or inclined heat exchanger tubes, and having means for supplying a condensable gas as a primary medium to the outside of the heat exchanger tubes and means for supplying a secondary medium to the inside of the heat exchanger tubes. A heat exchanger characterized by having an inclined plate inclined with respect to the horizontal direction on the outer surface of the heat tube.