KR810000174B1 - Heat exchanger - Google Patents

Abstract

A heat exchanger is used in cooling towers and similar installations and comprises a number of rectangular section conduits(3) spaced apart and parallel to each other. These are used to convey the water which is to be cooled and each conduit is provided internally with rows of baffle plates(6) forming a serpentine circuit(7,8). The air is conveyed through round section tubes(5) which pass through the conduits from side to side, being at 90≰ to the axis of each conduit. These tubes are plain and have no external finning, but may be provided with internal baffles to produce turbulence.

Description

heat transmitter

1 is a plan view of a dry cooling tower incorporating a heat exchanger.

FIG. 2 is a sectional view taken along the line I-I of FIG. 1. FIG.

3 is a right sectional view of the heat exchange element.

4 is a top view of the FIG. 3 element.

5 is a longitudinal sectional view of an element different from FIG.

6 and 7 are longitudinal cross-sectional views of a dry cooling tower.

8 is a partial plan view of an element.

9 is a cross-sectional view of FIG. 8 a-a.

10 is a horizontal sectional view directly above the heat exchange element of the cooling tower.

11 is a central longitudinal section of the cooling tower.

12 is a horizontal sectional view directly above the heat exchange element of the cooling tower.

13 and 14 are characteristic curve diagrams of a heat exchanger according to the present invention.

The present invention relates to a heat transfer medium having a relatively high heat transfer coefficient compared to air, for example a heat exchanger which indirectly recools water by air.

It is known to send recooling water through a cooling conduit and to pass air in a direction perpendicular to the conduit. The surface of the tube in contact with air is generally fitted with a fin or vane so that the heat transfer coefficient on the air side and the product of the effective heat transfer area (α _L × A _L ) are as balanced as possible with the water side (α _W × A _W ) To achieve. However, as the ratio of A _L / A _W (A = area) increases, the spacing of the fins must be reduced and the height of the fins must be increased, which causes pressure loss on the air side and heat conduction from the fin to the tube body. Since the loss by the enemy is limited to the approach of the enemy. Both reduce the heat exchange efficiency depending on the efficiency of the tube.

In order to deliver the same amount of heat, for example, a dry cooling tower needs a larger size than a wet cooling tower, and the size of the tower can be made smaller by the enlargement of the surface area of the air side, but still significantly larger.

(여기서 A_WU및 A_L는 열전달 매체측 및 공기측의 열전달면적, α_WU및 α_L은 각각의 열전달 계수를 표시함)의 비가 바람직하게 달성될 수 있는 제조 용이한 열교환기를 제공하는데 있다.The object of the present invention is to make the resistance on the air side as small as possible and

(Where A _WU and A _L are heat transfer areas on the heat transfer medium side and air side, α _WU and α _L represent the respective heat transfer coefficients) to provide an easy-to-manufacturing heat exchanger in which the ratio can be preferably achieved.

The present invention provides a heat exchanger having two parallel end walls and a heat transfer medium inlet having a hole according to the present invention, and a tube through which a free flow of air sealed through the side wall and the end wall having an outlet flows through the end wall. Is achieved.

In the case of the heat exchanger according to the present invention, the air contact area can be arbitrarily enlarged by the length of the tube without using a fin, and no additional loss due to heat conduction occurs.

The heat load per unit area decreases as the length of the tube increases, so the loss decreases. The heat exchanger according to the present invention has a significantly higher heat transfer capacity in the heat exchanger according to the present invention due to the physical difference in the case of the same air contact area and the same air-side flow resistance in the case of a tube having a fin on the outer surface. All of the contact area enlargement of is to enlarge the contact area of water.

이 적용되어 관의 길이는 0.8m 이상 또는 0.8m로 선택된다. 여기서The fact that such a fact and the top cross section can be utilized more effectively raises heat transfer ability further. In the case of a heat exchanger having a tower wall necessary for generating a suction force of the cooling tower, the cooling tower is designed according to the advantageous formation of the present invention.

This applies so that the length of the tube is chosen to be at least 0.8m or 0.8m. here

L = length of the tube, m

H = height of the tower wall, m

r ₁ = specific gravity of air just before the inlet of the heat exchanger kg / ㎥

r ₂ = specific gravity of air at the top of tower wall kg / ㎥

K = heat exchange capacity w / ㎡k (air flow area ㎡, watt per kelvin)

Here, the airflow area refers to the projected area of the heat exchanger as seen in the direction of the airflow immediately before the heat exchanger.

Cooling towers (heat exchangers) designed in this way have particular advantages in terms of tower size, or heat exchange capacity, compared to known structures with fin tubes.

According to another feature of the invention, the inner diameter of the tube is 10 to 50 mm and / or the thickness of the tube is 0.3 to 1 mm, and / or in the case of liquid heat transfer medium, the spacing between adjacent tubes is 0.5 to 2 mm. By doing so, a preferable relationship is achieved.

When the vapor phase heat transfer medium is condensed, the distance between adjacent tubes is advantageously 2 to 5 mm. In order to generate a favorable flow for heat transfer in the heat exchange element of the heat exchanger, a flow path for guiding the liquid transfer medium is formed inside each element by one or a plurality of intermediate walls, so that the heat transfer medium is guided like a cooling pipe.

When the heat exchanger according to the present invention has a plurality of heat exchange elements, the elements are arranged adjacent to each other left and right or up and down.

In addition, according to another form of the invention, the tube extends from the end to a hexagon, where the hexagonal stars or sides are closely coupled to each other with respect to the heat transfer medium to form an end wall. This means brings particular advantages in the manufacture of a member suitable for a heat exchanger.

Reduction in top size or increase in heat exchange capacity is achieved by having a turbulence generator in the tube through which air passes by another feature of the present invention.

Referring now to the drawings the present invention will be described. The dry cooling tower 1, which derives the heat of condensation in a large steam station, has a number of heat exchange elements 2 which connect to the supply and outlet tubes in the tower for reasons of transport and handling of the heat exchange elements. Since the heat exchange elements 2 are all made of the same element, one heat exchange element will be described in detail below.

Each heat exchange element 2 has two plates 3 spaced apart from each other and arranged up and down. The plates 3 can be arranged horizontally or inclined, and the two plates 3 form a flow path together with the side walls 4, through which the heat transfer medium is particularly recooled with a higher heat transfer coefficient than air. For water is induced. The heat transfer medium enters the flow path at one end and leaves the flow path at the other end.

에 적합한 간격은 간단한 계산에서 얻어지며, 가장 적합한 간격은 관(5)의 재질에 의하여 다르다.The plate 3 has a hole through which a vertically conductive tube 5 of heat conducting material, for example aluminum, penetrates through which air is guided from the bottom up. Since the hole of the tube 5 and the plate 3 having a smooth outer surface comes into contact with each other to form a liquid-tight bond, the heat transfer medium cannot be leached outward. The tube 5 protrudes through the upper and lower plates 3. The ratio from the air inlet of the pipe 5 to the flow path formed by the plate 3 and the side wall 4

The spacing suitable for is obtained from simple calculations, and the most suitable spacing depends on the material of the tube (5).

Between the plates 3, an insertion plate 6 may be arranged to help guide the heat transfer medium in parallel with the plates.

According to FIG. 3 three insertion plates 6 are provided, which are arranged such that 34 identical cross sections are formed in the heat-transfer medium which flows through.

The heat transfer medium enters into the heat exchange element from the inlet 7 and is diverted at the end of the flow path of the element several times to be guided in the form of a pipe and exit from the outlet 8.

As shown in FIG. 5, a plurality of separate flow passages (without insertion plates) having a small height may be vertically divided into a plurality of flow passages having a small height by the insertion plate 6 as shown in FIG. It can also be arranged separately.

The heat conducting medium flows in from the inlet 9 where it is diverted and enters the central flow path at the central inlet 10, and again is diverted to enter the lower flow path at the inlet 11 and flows out of the outlet 13.

The heat transfer area per element on the heat transfer medium is

Awu = daππz

[Da = outer diameter, b = distance of plate, z = watering, pi = 3.14159].

Heat transfer area per air side element is for pipes without inner fan.

A _L = d _i

[Di = inner diameter of the tube, l = length of the tube, z = irrigation,? = 3.14159].

7 reduces the cost by raising the portion above the heat exchange element of the tube 5 from the inside of the tower to the outside so that the outermost tube heat becomes a part of the cooling tower wall, respectively. The outermost tubes are in contact with one another or are spaced apart and the gap is filled by a suitable medium for reasons of sealing and strength.

The pipe rows are mutually supported by increasing their height gradually from the inside to the outside.

The distance between the bottom of the tube and the bottom of the cooling tower increases as the distance from the center of the tower increases to achieve the desired inflow of air.

(See Figures 6 and 7)

For example, in a cooling tower having a square cross section, when four heat exchanging elements 2a, 2b, 2c, and 2d are arranged forward and backward in the longitudinal direction of the heat exchanging element, supply of a cooled heat transfer medium This is done for example via two conduits 14a, 14b extending perpendicular to the longitudinal axis of the heat exchange element. Two conduits 14a and 14b each pass between two opposing sides and feed the medium to all four rows of elements. Conduit 14a feeds media in two rows of A and B, and conduit 14b feeds in two rows of C and D. Derivation of the heat transfer medium in the heat exchange element is done via conduits 15a, 15b, 15c and 15d, which are equally perpendicular to the longitudinal axis of the heat exchange element but on the side opposite to the inlet side. To pass. Conduits 15a to 15d are engaged with the outlet openings of all heat exchange elements 2.

When the plate 3 is horizontal, the plate is formed by enlarging the ends of the tube 5 to the hexagonal portion 5a and closely joining the six sides to each other by welding solder bonding or another method.

In FIG. 8, a part of the heat exchange element formed in this manner is shown in a plan view, and an arrow 21 indicates the direction of flow of the heat transfer medium.

The cross-sectional area (length x width) of the heat exchange element 2 is selected for transport, and the height is selected by electrothermal engineering needs. Heat exchange elements are made of aluminum, brass, special steel and carbon steel.

As air flows through the tube 5, a boundary layer is formed between the tube wall and the fluid at a certain distance from the inlet, and the thickness of the boundary layer increases as the distance from the inlet becomes longer. Moreover, in order to improve heat transfer, well-known means, such as a spiral body and a ring-shaped press line, are used in a pipe | tube. This means that it becomes a rather effective turbulence generator to remove the boundary layer. Turbulence generator 16 is shown in FIG. All the walls except for the lower surface and the upper surface formed of the side wall 4 of the box heat exchange element 2, that is, the plate 3, can be formed flexibly. In this case, the heat exchange elements are arranged to be spaced apart from each other with respect to the inner wall of the cooling tower, and must be rigidly formed with respect to the frame structure 18 (FIG. 11) in the area where the heat exchange elements in the cooling tower are arranged. The rigid frame structure 18 assists in supporting the bottom and side surfaces of the heat exchange element and may be formed of, for example, concrete. The gap between the sidewalls of the heat exchange elements and the corresponding heat exchange element side walls of the cooling tower inner wall are filled with a pressure-resistant filler 17, for example a plastic material. When the heat transfer medium flows through the heat exchange element 2 from the outside of the heat exchange element at a pressure lower than the pressure actuated by the atmosphere, the side walls 4 of the heat exchange element 2 are mutually spaced 20a and on the inside of the cooling tower. It is arranged at intervals 20b and is provided with vertically extending shaped steel materials 19 which, for example, are joined to the outer wall 4 by welding, for example. As the shaped steel, a shaped steel having a U-shaped cross section is used as shown in FIG. This section steel 19 has two legs 19a and 19b parallel to the side wall 4 of the heat exchange element, one end of which is joined to each other by a horizontal member 19c perpendicular to the legs.

The heat exchange elements 2 are elastically coupled by the shape steel 19 so that the forces generated by decompression on each side of the heat exchange elements are extinguished. For example, in the concrete frame 18 formed of the rigid material, the same shape steel material 19 '(c shape) is provided. The section steel 19 is elastically coupled so that the tension generated by the pressure reduction with the section steel 19 on the adjacent side wall of the heat exchange element is absorbed by the frame structure 18. The gap 20a between the side walls 4 of the adjacent heat exchange element 2 or the gap 20b between the outermost side wall adjacent the frame structure and the cooling tower inner wall is filled with a pressure-resistant filler, for example a suitable plastic material, as described above. do. Plastic materials are advantageous because they absorb the forces generated by overpressure in the element.

In the case of such formation, the heat exchange element can optionally be operated under overpressure or under reduced pressure. Therefore, the filling by the fillings in the gaps 20a and 20b assists in the sealing, so that intrusion of leakage air can be avoided. The cross section of the cooler is particularly square in the range in which the heat exchange element 2 is arranged to almost fill the cross section. However, the cross section may be a sphere, for example.

In the case of the preferred embodiment shown in FIG. 9, a plurality of heat exchange elements 2 are not arranged adjacently, and each heat exchange element is disposed apart from the heat exchange medium circuit. In order to obtain favorable heat exchange conditions for the liquid heat exchange medium and to guide the flow of the heat exchange medium inside the heat exchange element, a horizontal intermediate wall is installed, one of which is indicated by the partition 6 'in FIG. . The intermediate wall is also required for cooling the gaseous heat exchange medium. The partition 6 'is not necessary when the heat exchange medium is condensed by the inflow of heat exchange elements in the form of steam.

The diagram of FIG. 13 shows the characteristics of the heat exchange element according to the invention. This heat exchange element has been tested in the laboratory and the most important data are as follows. Height (= length of tube 5); 0.5-4 m, arbitrary width and length: 20 mm inner diameter tubeless tube, spiral 0.6 mm as a turbulence generator and spiral pitch 50 mm.

The air flow rate (W _A ) immediately before the inlet of the cooling pipe is indicated in m / S on the horizontal side of the drawing, and the air flow (heat exchange capacity per square meter of area (KA) is Kcal / m 2 hk (kilo calories / square m, time) on the vertical axis. Curves α ₁ , α ₂ , α ₃ , α ₄ , α ₅ , and α ₆ , respectively. Curve α ₁ is a 0.5 m long tube, curve α ₂ is L = 1.0m, α ₃ is L = 1.5m, α ₄ is L = 2.0m and α ₅ is L = 3.0 m and (α ₆ ) were obtained with a tube of L = 4.0 m.

Further, curves β ₁ to β ₁₀ are shown in the drawing, in which case curve β is given in mm orders of pressure loss ΔP measured as the differential pressure between the air inlet and the outlet. Curves β ₁ to β ₁₀ are curves for ΔP of 1 mm to 10 mm orders.

In this figure, in order to explain the progress of the heat exchange element according to the present invention, a value obtained from a fin tube heat exchange element having a known structure in which a cooling medium flows through the fin tube and air flows at right angles is written. Known heat exchange elements were obtained from a Seilnetz dry cooling tower at Schmehausen, a nuclear power plant. In the data used here, the value of K _A was 3,340 Kcal / m 2 hk, and the value of ΔP was written on the surface even if an order of 8.3 mm was obtained. In this regard, when a straight line g ₁ parallel to the horizontal axis is drawn, a pressure loss of about 2 mm is obtained by selecting the height of the element as 3 m flow rate of about 1 m / S, for example, by the heat exchange element of the present invention with the same heat exchange capacity. . That is, according to the heat exchange element structure according to the present invention, it is possible to derive the same amount of heat per unit time with a pressure loss value of about 1/4. Since the ΔP value has a decisive influence on the height of the cooling tower, when the cooling tower length (height of the heat exchanging elements) and the air flow rate are appropriately selected by the heat exchange element according to the present invention, about ¼ of the height of the known cooling tower of the Schmehausen atomic power station It is evident that a reduced cooling tower can be obtained and the smaller the cooling tower, the lower the production and maintenance costs.

In addition, since the height of the cooling tower is low, it does not harm the aesthetics. On the other hand, assuming that the cooling tower size and ΔP value are the same, a curve in the direction of the arrow is drawn along the ΔP curve β ₈ at point 0, for example, at a height of 3m, a remarkably high K _A value of about 7400 Kcal / m 2 hk is obtained. In other words, when a heat exchange element having a height of 3 m is introduced into a known (untrop Schmehausen 30 megawatt element cooling) cooling tower and the air velocity is 2.4 m / S, heat exchange capacity of about 2.2 times is obtained by the heat exchanger of the present invention. This shows the great advantage of the heat exchanger according to the present invention.

Another example of a known steam element with a commercial heat exchanger is indicated by an X in FIG. This is a device in South Grotte.

FIG. 14 shows the relationship between the height of the tower wall of the heat exchange capacity K _A in various enemas with L = 0.5 to 4 m.

In this case, the vertical axis represents the heat exchange capacity (W / m 2 k) per square meter of air flow cross-sectional area, and the horizontal axis represents the tower wall height (m).

In the figure, curves K _A = f ( _H ) for various tube lengths of L = 0.5 to L = 4m are represented by δ ₁ to δ ₆ . curve

δ ₁ is L = 0.5m, δ ₂ is L = 1.0m, δ ₃ is L = 1.5m, and δ ₄ is L = 2m

δ ₅ is L = 3.0m, δ ₆ is L = 4.0m

를 충족하는 것이 경험적으로 구해졌으며, 이 식에서 관의 길이 L는 m, 탑벽높이는 m, 공기비중 r는 kg/㎥이 사용되며, 계산 결과인 K_A값은 W/㎡k 단위로 얻어진다.Corresponds to the tube length. Curve δ is at least approximate K _A = 382.

In this equation, the length L of the pipe is m, the tower wall height is m, and the air specific weight r is used in kg / m3. The calculated K _A value is obtained in units of W / m2k.

FIG. 14 is obtained by posting the K _A value and the DELTA P value belonging to the corresponding α curve in FIG. 13 to the new figure. Each ΔP = g · H · (r ₁ -r ₂ ) [g was converted by the gravity acceleration, H by the tower height, r ₁ , r ₂ by the air specific gravity J at the heat exchanger inlet and the top wall top height. In order to simplify the calculation, the value of r ₁ -r ₂ was approximately 0.1 kg / m 3.

In addition, in Fig. 14, the value of a well-known heat exchanger having a fin tube (Schmehausen is 0 and Grot Belei is X) is written as in Fig. 13, where r ₁ -r ₂ is 0.1 kg / m 3. It was.

The figure shows that the tube length of 0.8 m or more in the heat exchanger of the present invention is superior in terms of top size or heat exchange capacity than known structures.

The application of the above formula K _A = f ( _H ) in relation to the known formula (known to those skilled in the heat exchanger) is described next.

Regarding Tower Height H

By variation or harm of

Is obtained and here 1n is the natural logarithm, again

Applies here where

A _A : Inflow area Δδm before a known pipe inlet: Log mean temperature difference between the medium to be cooled and air

D: Diameter at height under the top wall K _A : Heat exchange capacity W / m 2k

Q: Heat transfer amount W π: 3.14159 ..

Substituting Eq. (3) into Eq. (2) to solve for K _A ,

Is obtained.

Substituting Eq. (4) into Eq. (1)

Is obtained. Q, D, H, L, Δδ m, r ₁ , r ₂ are as described above. Given the design of the heat exchanger, Q, r ₁ , r _2, and Δδm (for example, Q = 4388.106W, r ₁ = 1.152kg.m 3, r ₂ = 1.152kg.m 3 and ΔδM = 10.55k Equation (5) gives the value of H for the various values of D and L. From these values obtained by the table, a combination of H, D and L values of economical and inexpensive devices is obtained. The above figures are only simple examples, but if these values are written in D = 140 mm, L = 1.80 mm, and H = 30 m, at least an approximate and extremely advantageous solution can be obtained.

The thermal bridge of the present invention is not limited to those shown and the above embodiments.

For example, the end wall (for example, the plate 3) may be close to vertical, and the pipe 5 may be horizontal or approximately horizontal.

If the end wall is horizontal or almost horizontal, only one heat exchange element consisting of the end wall, the side wall and the tube may be arranged in the cooling tower or casing. In addition, the heat conduction medium may use waste steam of the turbine, the heat exchanger may be other than natural suction or forced suction, and the intermediate wall may be formed by a method other than the insertion plate 6.

Indirect recooling by air of the heat transfer medium in this specification indicates that the heat transfer medium releases heat to the atmosphere via the pipe wall, i.e., does not come in direct contact with the air.

The expression heat exchanger includes heat exchange elements, cooling tower structures, and the like.

Claims (1)

A straight tube extends in parallel between the two end walls with holes or two end walls each having a hole and one or more side walls with inlets and outlets of the heat transfer medium are joined to the end wall and the heat transfer medium group and the heat transfer medium is In a known tubular heat exchanger which indirectly recools by heat with a heat transfer medium (eg water) that flows outside and has a larger heat transfer coefficient than air flowing through the tube, the fins 5 are spread in the longitudinal direction thereof. (Or wings), the end of the tube 5 is extended to the hexagonal portion 5a so that the sides or sides of the hexagonal element are joined to the mutual heat transfer medium group and inserted into the tube 5 to form an end wall. A heat exchanger for indirectly recooling a heat transfer medium, characterized in that a turbulence generator, such as a thin ring pressed into a spiral body or a pipe wall, or projections of an inner wall of the pipe is installed in the pipe (5).

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