JPS6059516B2 - Air-cooled heat exchanger with means to prevent supercooling - Google Patents

Description

[Detailed Description of the Invention] The tube bundle of an air-cooled heat exchanger is generally provided with multiple layers of finned tubes, and the high-temperature steam inside the tubes is cooled by the air flow that crosses this tube bundle, but the temperature of the air flow is The temperature is lower on the upstream side of the airflow, so the temperature difference with the steam inside the pipe is maximum at the inlet, and the cooling capacity is at its maximum value.As the airflow moves downstream across the finned pipe, The air stream is heated in turn by heat exchange with the finned tube, and the temperature difference with the steam inside the tube is reduced, thereby reducing the amount of heat transfer through the finned tube.

This means a reduction in the amount of directly condensed steam. As a result,
In the finned tube at the lowest temperature, the amount of steam flowing into the tube increases as the steam inside the tube condenses, but as the flow resistance of the finned tube increases and the closer it gets to the exit, the flow of steam decreases, ensuring sufficient heat transfer. Because the amount of steam is small despite the area, the condensed water becomes extremely supercooled and eventually freezes.

This tendency is particularly severe when the atmospheric temperature is extremely low, in winter, or in cold regions, and the same problem occurs when the fluid in the pipe has a high freezing point. In order to prevent these problems, efforts have been made to change the pitch of the fins, remove some fins and use bare tubes, or change the number of turns and height of the fins. Even with this adjustment, there was a risk that the pressure inside the pipes would become unbalanced every time the atmospheric temperature changed, resulting in overcooling.

To prevent such overcooling, there are methods in which each heat exchanger tube that makes up the tube bundle is made into an independent closed circuit, and the drain is extracted from each tube to prevent overcooling, and multiple U in the steam inlet header are used.
There is also a method that considers the difference in internal pressure by arranging U-shaped pipes in parallel inside and outside, but the former requires a complicated structure, and the latter requires drain generated inside the pipe to flow over a long distance in the U-shaped pipe. Therefore, there still remain drawbacks such as the fact that it is likely to be cooled more than necessary. By improving the above drawbacks, the vapor pressure of the fluid to be cooled in the heat transfer tube layer caused by heat exchange is kept uniform in each heat transfer tube, and condensed water is quickly extracted to prevent freezing and improve heat transfer efficiency. In order to improve the results, the applicant first filed Japanese Patent Application No. 53-68186
No. 24783) proposed a heat exchanger characterized by having heat exchanger tubes intersecting in the middle, but the present invention further improves this and can be applied to a tube bundle in which the heat exchanger tubes are maintained in a horizontal direction. Furthermore, the present invention aims to provide an air-cooled heat exchanger that prevents condensed water from accumulating and facilitates its outflow, thereby further helping to prevent overcooling.

The present invention will be described below with reference to the accompanying drawings showing examples thereof, but the present invention is not limited by the drawings or the following description, and the technical scope of the present invention is defined in the claims. That's right.

The air-cooled heat exchanger 1 shown in FIG. 1 has an inlet header 6 and an outlet header 7 arranged symmetrically on both sides above the cooling air supply fan device 2 with an inclination angle α0 to the horizontal plane.
Tube bundles 3 and 3'' are disposed between the left and right headers 6 and 7, respectively, and the heat transfer tubes 4 used here are oriented horizontally, as shown in Fig. 4 to increase the heat transfer surface. The fin 5 is wrapped around the fin 5.

In FIG. 2, the tube plate 8 of the inlet header 6 has lower tube holes A, A'', A''... and upper layer tube holes B, B'', B''.
... are bored in the tube plate 9 of the outlet header 7, and upper pipe holes A, a'', a''... and lower pipe holes B, b
'', b''... are bored, so that two layers of upper and lower heat transfer tubes are provided per channel.

In this example, the tube plate 8 of the inlet header 6 has a second
As clearly shown in FIG. l! 1. B is provided horizontally, tube holes B and A'' are provided vertically, and tube holes A'' and B'' are provided horizontally, while as shown in FIG.
The tube plate 9 of the outlet side header 7 has tube holes a<15b in the vertical direction and tube holes B. (5a'' in the horizontal direction, pipe holes a'' and b
The headers 6 and 7 are both provided at an inclination of 45 degrees with respect to the horizontal plane. Therefore, in the tube sheet 8, the tube holes A, A'', A'''' form the lower row, and the tube holes B, B'', B'' form the upper layer row, and in the tube sheet 9, the tube holes A, a ″, a″ are upper rows, tube holes B, b″, b″
" form the lower row. One end is connected to the lower pipe hole of the tube plate 8, A
, A'', A'', the other end of each heat exchanger tube P is inserted into the upper tube hole A, a'', a'''' of the tube plate 9, and a horizontal bent portion 10 is formed in the center. and on the other hand, one end is connected to the tube plate 8.
Each heat exchanger tube Q inserted into the upper layer pipe hole B, B″, B″″ is
The other end is inserted into the lower tube holes B, b'', b'' of the tube plate 9, and a vertically bent portion 11 is formed in the center. Thus, on the inlet side, each heat exchanger tube P is in the lower layer and each heat exchanger tube Q is in the upper layer, but on the outlet side, this arrangement is reversed, and each heat exchanger tube P and Q has a flow direction of the fluid in the tube. The structure is such that there are no rising points. In addition, when using a heat exchanger tube wrapped with fins 5 to increase the heat transfer area as shown in FIG. They are starting to overlap. In the air-cooled heat exchanger having the above configuration, a part of the steam introduced into the inlet side header 6 enters the lower heat exchanger tubes P through the tube holes A, A″, A″, etc. in the lower row, and other parts A part of the upper row of pipe holes B, B″, B″
..., but after passing through the intermediate bends 10 and 11, the layers of the flow are turned upside down.

In other words, the pipe holes A, A″ in the upper layer of the inlet header 6,
Each heat exchanger tube P connected to A''... is in the lower layer in the first half, so it is closest to the fan device 2 and is therefore strongly cooled by the low-temperature air flow. ,B
Since the inside of each heat exchanger tube Q connected to the `` The temperature difference is small, the amount of heat transfer is small, and the amount of condensed steam is reduced.However, the heat exchanger tubes P and Q are
After passing through the bends 10 and 11 in the middle, the layers are turned upside down, so the cooling effect in the second half is also the opposite of the first half, so the cooling by the air flow as a whole is made uniform. , the vapor pressure of the residual steam and non-condensable gas in the tubes becomes uniform in both the upper and lower layers, and only a part of the heat exchanger tubes is not overcooled. In addition, in the above implementation, both headers 6,
The inclination angle of P.7 with respect to the horizontal plane is set to 45 degrees, and the two-layer heat exchanger tube P. Among the heat exchanger tubes Q, the intermediate bent portion 10 of one heat exchanger tube P is formed in the horizontal direction, and the intermediate bent portion 11 of the other heat exchanger tube Q is formed in the vertical direction, but steam does not accumulate in the tube, and Both headers and both bent portions may be appropriately inclined to such an extent that the pipes do not contact each other, and it goes without saying that the outlet side header 7 is provided with a condensed water takeoff pipe and a vent pipe as usual. Furthermore, although the above embodiment shows a case in which the cooling air from the fan device is brought into direct contact with the two-layer heat transfer tubes, the main condensing tube bundle is installed so that it is normally placed between both headers, and the The technical means of the present invention can also be applied to the folded flow sub-condensing pipe provided in the sub-condenser pipe. In summary, the present invention comprises an inlet header and an outlet header arranged at an angle with respect to a horizontal plane, horizontal heat transfer tubes arranged in upper and lower layers to communicate with both headers, and a fan device for cooling fluid in the tubes. In an air-cooled heat exchanger with horizontal heat exchanger tubes in both upper and lower layers,
The pipe is characterized by bending it horizontally and downwardly at the middle part so that there is no rising part in the flow direction of the fluid inside the pipe, and converting the layers of both horizontal heat transfer tubes on the inlet side and the outlet side to reverse positions. The gist of the air-cooled heat exchanger is an air-cooled heat exchanger equipped with supercooling prevention means.According to this, the fluid in the tubes that is strongly cooled in the lower layer tubes on the inlet side becomes the upper layer on the outlet side and is heated in the lower layer heat exchanger tubes. On the other hand, the fluid in the upper pipe on the inlet side was gently cooled by the air flow, whose temperature increased by exchanging heat with the fluid in the lower pipe, and passed through the intermediate bend. It is then transferred to the lower layer, where it is strongly cooled by the low-temperature air flow, so that the fluid in both the upper and lower layers is cooled uniformly as a whole, and even if the atmospheric temperature changes, the fluid in both the upper and lower layers remains cool. The pressure balance in the heat exchanger tubes of the layers does not collapse, and it is possible to avoid the conventional disadvantage that only the lowest heat exchanger tube is supercooled and the condensate inside the tube freezes. The bending part provided in the middle of the tube is formed so that the lower heat transfer tube on the inlet side takes the horizontal direction, and the heat transfer tube that rises on the inlet side takes the downward direction. There are no rising points in the flow direction, and therefore, the condensate flows out easily, does not accumulate in the pipe, and can be quickly discharged from the outlet header, preventing overcooling and, ultimately, preventing freezing. can be further encouraged.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and Fig. 1 is a schematic layout diagram, Fig. 2 is a perspective view of the main parts, Fig. 3 is an enlarged plan view thereof, and Fig. 4 is a tube plate of Fig. 2. The side view of Figure 5 is the side view of Figure 2.
-V line sectional view. 1... Air-cooled heat exchanger, 2... Fan device, 3,3''... Tube bundle, 4... Each heat transfer tube, 5...・Fin, 6... Inlet side header, 7... Outlet side header, 8... Inlet side tube plate, 9... Outlet side tube plate, A ,A″,A″
...Inlet side lower pipe hole, B, B'', B''...
・・Inlet side upper layer pipe hole, A, a″, a″・・・・Outlet side upper layer pipe hole, B, b″, b″″・・・・・Outlet side lower layer pipe hole, P・・...Inlet side upper heat exchanger tube, Q...
- Upper layer heat exchanger tube on the inlet side, 10...Bending portion of heat transfer tube P, 11...Bending portion of heat transfer tube Q, α...Inclination angle of header.

Claims (1)

[Claims] 1. An air-cooled heat exchanger having an inlet header and an inlet header arranged at an angle with respect to a plane, horizontal heat transfer tubes arranged in upper and lower layers and communicating with both headers, and a fan device for cooling fluid in the tubes. In this method, horizontal heat exchanger tubes in both upper and lower layers are bent laterally and downwardly at the middle part so that there is no rising part in the flow direction of the fluid inside the tubes, and the layers of horizontal heat exchanger tubes on the inlet side and the outlet side are An air-cooled heat exchanger equipped with a means for preventing supercooling, which is characterized by converting the arrangement to reverse.