CN101078598A - Multi-tube pass type heat exchanger - Google Patents

Abstract

The invention relates to a heat exchanger with multiple tube side, especially applied in exhaust gas recirculation cooling device in automobile engine system. The invention comprises shell and heat exchanging pipe. Pipe plates are set at two ends of said shell. Pipe ports of said heat exchanging pipe are welt on the pipe plate and are fixed in the shell in parallel. Double tube side is constituted by said heat exchanging pipe groups and is divided into a first tube side and a second tube side. The quality of heat exchanging pipes in the first tube side is more than the one in the second tube side. The height of sections of said heat exchanging pipe is different from the width and it is flat shape. Grooves are set on said heat exchanging pipe on the outer surface. Said grooves are convex on the inner surface of heat exchanging pipe and the shape is corresponding to the groove. The invention can improve heat exchanging efficiency by 25-40%, decrease emission of NOx in automobile engine, and shorten length and cubage of heat exchanger. The invention is provided with simple and compact structure, low scaling and low manufacture and maintenance cost.

Description

A multi-tube heat exchanger

technical field

The invention relates to a heat exchanger, in particular to a multi-tube heat exchanger, which is suitable for use in exhaust gas recirculation systems of automobile engines, and is used as a cooler for reducing emissions of nitrogen oxides (NOx) , is also suitable for use as an intercooler in a turbocharger system to improve engine performance.

Background technique

Heat exchangers are used in various industrial sectors such as power, metallurgy, chemical industry, oil refining, construction, machinery manufacturing, food, medicine and aerospace. Therefore, the optimal design of heat exchangers is particularly important for various industries. With increasingly stringent emission standards around the world, heat exchangers in automotive exhaust gas recirculation cooling systems are critical.

Exhaust gas recirculation cooling technology is in the well-known automobile engine exhaust gas recirculation system. Part of the exhaust gas emitted by the automobile engine is cooled and recycled through the heat exchanger, and the cooled exhaust gas is returned to the combustion chamber of the engine, so that The introduction of inert gas, mainly carbon dioxide (CO ₂ ) into the combustion chamber can not only reduce the content of nitrogen (N ₂ ) in the combustion chamber, but also reduce the temperature of the combustion chamber, the lower temperature and less nitrogen in the combustion chamber ( N ₂ ), which can not only make the fuel fully combust but also make the reaction conditions between nitrogen (N ₂ ) and oxygen (O ₂ ) deficient, so as to suppress the generation and emission of nitrogen oxides (NOx). Therefore, in the exhaust gas recirculation system, a high-efficiency exhaust gas recirculation heat exchanger can make the vehicle's emissions reach a higher standard.

At present, there are two types of heat exchangers used in the exhaust gas recirculation system of automobile engines.

The first type is the plate-fin heat exchanger, which is composed of many thin plates and the secondary surface between the plates. The secondary surface not only serves as the ribbed surface, but also plays the role of the tube-sheet spacing and enhances the rigidity. This type of heat exchanger The structure of the exchanger is complex and the manufacturing cost is high.

The second type is the shell-and-tube heat exchanger, and the shell-and-tube heat exchanger is provided with many parallel tubes in a cylindrical shell (these parallel tubes are called tube bundles), and the hot and cold fluids are separated from the space in the tubes. (tube side) and the space outside the tube (shell side) flow through for heat exchange; usually a longitudinal partition parallel to the tube bundle or a baffle perpendicular to the tube bundle is installed on the shell side; to increase the flow velocity of the fluid and enhance the disturbance, Improve heat exchange efficiency; this type of heat exchanger has a simple structure, but low heat exchange efficiency. Due to the limited space around the automobile engine, it is necessary to find a heat exchanger with high heat exchange efficiency and compact structure in order to effectively reduce unnecessary settings without reducing the heat exchange efficiency.

Contents of the invention

The purpose of the present invention is to improve the heat exchange efficiency and compact structure of the heat exchanger and propose a multi-tube heat exchanger technical solution, which is especially suitable for the exhaust gas recirculation cooling device or cooling device in the automobile engine system. Intercooler for engine turbo system.

The technical solution of the present invention is achieved in that the heat exchanger includes a shell and heat exchange tubes; tube plates are respectively provided at both ends of the shell, and the nozzles of the heat exchange tubes are respectively welded on the tube plates and connected to each other. fixed in the shell in parallel; it is characterized in that the heat exchange tubes form double tube passes, which are divided into a first tube pass and a second tube pass according to the sequence in which the heat exchange medium flows in the heat exchange tubes, and the second tube pass The heat exchange medium outlet of the first tube side and the heat exchange medium inlet of the second tube side form a "U"-shaped circuit through the head fixed on the shell, and the number of heat exchange tubes in the first tube side is more than that in the second tube side The number of heat exchange tubes; the cross-sectional height and width of the heat exchange tubes are not equal, and the shape is flat; the heat exchange tubes are provided with grooves along the outer surface, and the grooves are convex on the inner surface of the heat exchange tubes. Corresponds to the groove shape.

The cross-section of the heat exchange tube is elliptical, and the ratio of the major axis to the minor axis of the ellipse is less than 4:1.

The cross-section of the heat exchange tube is flat, the two opposite long sides are arranged to be arc-shaped protruding from the inside to the outside, and the two opposite short sides are arc-shaped protruding from the inside to the outside, and are round to the long side Arc transition connection.

The cross-sectional shape of the heat exchange tube is composed of two opposite short sides and two opposite long sides, wherein the short sides are arcs protruding from the inside to the outside, and the long sides are straight lines.

The cross-sectional shape of the heat exchange tube is rectangular, and the two adjacent sides are connected by an arc transition.

The heat exchange tube is a stainless steel tube body.

The grooves are arranged intermittently or continuously and spirally along the outer surface of the heat exchange tubes.

The groove depth of the heat exchange tube is not less than 0.4mm.

One or more grooves are provided, and the cross-sectional shape is "U" or "V".

The shape of the head is a curved surface.

Baffles are arranged in the heat exchanger housing.

The shell of the heat exchanger can be designed in various forms of appearance and structure according to the internal space of the engine. The heat exchange tubes are arranged in a reasonable arrangement in the shell of the heat exchanger according to the different appearance shapes of the shell.

Compared with the prior art, the present invention has the following advantages:

1. Under the same conditions, that is, under the premise that the volume of the cooler and the flow rate of the heat exchange medium remain unchanged, the heat exchange efficiency can be increased by 25-40% by using the present invention.

2. Using the present invention in an exhaust gas recirculation system of an automobile engine can reduce the emission of nitrogen oxides (NOx) of the automobile engine and improve the emission performance index of the automobile engine under the same conditions.

3. Compared with the plate-fin heat exchanger, the present invention has a simple structure and reduces the manufacturing cost.

4. Since the present invention uses a multi-channel tube structure in the heat exchanger, the length and volume of the heat exchanger are shortened under the same conditions, and the engine structure is more compact.

5. Since the spiral convex structure provided on the inner wall of the heat exchange tube in the present invention enhances the heat exchange, the strong turbulent movement causes the dirt to be severely eroded in the tube, which is not easy to scale, which is beneficial to cleaning and reduces the Heat exchanger maintenance costs.

6. The present invention takes saving cost and improving performance as the starting point, and provides a technical platform for the organic integration of the engine exhaust gas recirculation refrigeration system and the power system, which greatly saves the space and volume of the engine, and effectively reduces unnecessary settings. While improving the performance of the engine, it greatly saves the manufacturing cost for the manufacturer.

The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the schematic diagram of the front of one end plate of the present invention;

Fig. 3 is a schematic diagram of a heat exchange tube with a spiral groove;

Fig. 4 is a schematic diagram of the cross-sectional shape of the first heat exchange tube;

Fig. 5 is a schematic diagram of the cross-sectional shape of the second heat exchange tube;

Fig. 6 is a schematic diagram of the cross-sectional shape of the third heat exchange tube;

Fig. 7 is a schematic diagram of the cross-sectional shape of the fourth heat exchange tube;

Fig. 8 is a schematic structural view of the present invention with baffles.

Detailed ways

Example 1

Referring to Fig. 1 and Fig. 2, it is an embodiment in which the heat exchange tube is divided into two tubes, wherein, fixed tube sheets 3 are provided at both ends of the shell 1, and the fixed tube sheets 3 are provided on the tube sheet 3. The through holes and the nozzle ends of the heat exchange tubes 2 are respectively welded in the corresponding holes on the tube sheet 3 and fixed in the shell 1 parallel to each other.

The heat exchange tubes 2 form the first tube pass 4 and the second tube pass 5, the exhaust gas outlet port of the engine is connected with the exhaust gas inlet port 8 of the first tube pass 4, the exhaust gas outlet port 9 of the first tube pass 4 is connected with the second tube pass The exhaust gas inlet port 10 of 5 is interconnected through the head 6 fixed on the casing 1, and the exhaust gas outlet port 11 of the second tube pass 5 is connected with the engine air inlet. The sealing head 6 has an arc-shaped curved surface to facilitate the flow of exhaust gas.

The arrow direction in FIG. 1 is the flow direction of the heat exchange medium, and the number of heat exchange tubes 2 in the first tube pass 4 is greater than the number of heat exchange tubes 2 in the second tube pass 5 .

A cooling medium inlet 7 is provided on the housing 1 near the exhaust gas inlet end of the first tube side 4, and a cooling medium is provided on the opposite side of the inlet 7 on the housing 1 near the exhaust gas inlet end of the second tube side 5 Exit 12.

Assuming that the fluid density ρ is a constant value and the fluid volume flow rate Q _V is constant, in order to ensure that the average flow velocity v and resistance loss of the fluid in different tubes are roughly the same, according to the fluid mechanics formula Q _V =Av=con tan t , the flow area A of different tube passes is the same, that is, the number of heat exchange tubes in different tube passes is approximately the same.

In Example 1, the exhaust gas from the engine first flows through the heat exchange tube 2 of the first tube pass 4, and then flows through the heat exchange tube 2 of the second tube pass 5, and the flow of the fluid in the tube pass is in a "U" shape. circuit. After the exhaust gas passes through the cooler, the temperature before and after cooling can vary by hundreds of degrees, and the density ρ of the gas has a certain gap between high temperature and low temperature. On the premise that the mass flow rate Q _M remains constant, the temperature of the exhaust gas when passing through the first tube pass 4 is higher than the temperature when passing through the second tube pass 5, then the density ρ ₁ of the exhaust gas in the first tube pass is higher than that in the first tube pass The density ρ ₂ of the second tube pass 5 is low, that is, ρ ₁ ≤ ρ ₂ , according to the formula Q _M = ρ ₁ A ₁ v ₁ = ρ ₂ A ₂ v ₂ = con tan t, in order to ensure that the fluid in different tube passes The average flow velocity v and the resistance loss are roughly the same, so the flow area of the first tube pass 4 is larger than the flow area of the second tube pass 5, that is, A ₁ ≥ _{A 2} . Therefore, the number of heat exchange tubes 2 in the first tube pass 4 is greater than the number of heat exchange tubes 2 in the second tube pass 5 . This ensures that under the same mass flow rate, the number of tubes in the first tube pass 4 increases and the resistance decreases, and the number of tubes in the second tube pass 5 decreases and the speed increases, so the heat exchange effect is better. The enhanced heat exchanger finally enables the heat exchanger to achieve higher heat exchange efficiency, and also reduces the number of heat exchange tubes used and saves materials.

Referring to Fig. 3, the heat exchange tube 2 in Embodiment 1 is a stainless steel pipe body, and there is an inwardly protruding spiral rotating groove 21 on the surface; the spiral groove 21 is one or multiple; the spiral groove 21 The groove 21 is arranged continuously along the surface of the heat exchange tube 2, or it can be arranged intermittently; the cross-sectional shape of the spiral groove 21 is "U" shape, and can also be set as a "V" shape, which is beneficial to the processing of small-sized shaped surfaces; The helix angle 24 of the groove 21 is 25 degrees, which can be set between 20 and 75 degrees; the depth of the groove 21 is 1mm, and the depth setting should not be less than 0.4mm, and the outer diameter of the heat exchange tube is the same as the set value of the heat exchange tube. The ratio of the inner diameter of the bottom of the groove is less than 1.4.

A heat exchange tube with a spiral groove is installed in the heat exchanger. When the fluid passes through the heat exchange tube, it encounters the obstruction of the spiral protrusion in the tube, and the flow direction changes, resulting in a complex secondary flow vortex flow. At the same time, a vortex is also formed behind the spiral protrusion, which increases the turbulence of the exhaust gas, especially increases the disturbance of the boundary layer near the wall, destroys or thins the boundary layer of the fluid, thereby enhancing the heat transfer ; At the same time, the enhancement of fluid disturbance reduces the critical Reynolds number, that is, the transition from laminar flow to turbulent flow occurs earlier, and the strong turbulent flow makes the dirt in the tube severely eroded, which is not easy to scale and easy to clean.

Referring to Fig. 4 to Fig. 8, the vertical section of the heat exchange tube 2 fixed in the shell 1 can have various shapes;

The heat exchange tubes arranged in the shell 1 with a flat cross-sectional shape and spiral grooves are compared with the circular heat exchange tubes with spiral grooves in the cross-sectional shape: First, when the cross-sectional area of the heat exchange tubes is constant and the flow rate of the heat exchange medium is not Under the premise of changing, the cross-sectional perimeter of the flat tube is larger than that of the round tube, so the heat transfer area of the flat tube is larger than that of the round tube, which in turn increases the heat transfer area of the entire heat exchanger. Under the premise that the volume of the heat exchanger remains unchanged, the heat exchanger achieves a higher heat exchange effect; in addition, the flat heat exchange tubes with spiral grooves arranged in the exhaust gas recirculation heat exchanger are not only better than the circular tubes. The heat exchange area has increased, and the flat tube is compared with the round tube, because the flat tube is not a symmetrical shape to the center of the round tube, and the distance between the geometric center of the flat tube with spiral grooves and the tube wall is smaller than that of the circular spiral The distance between the grooved tube and the tube wall is small, most of the fluid in the tube can participate in heat exchange, and the shape of the flat tube enhances the disturbance of the fluid, and the disturbance of the fluid in the tube is more intense, which also enhances the heat transfer effect. As a result, the temperature of the fluid in the tube drops rapidly, the temperature difference between the inlet and outlet increases, and the heat exchange efficiency is improved.

Example 2

Referring to Fig. 1 and Fig. 4, the fixed heat exchange tube 2 in the housing 1 is a heat exchange tube with the first cross-sectional shape shown in Fig. The two opposite short sides 22 are arc-shaped protrusions from the inside to the outside, and are connected with the long side 23 in an arc-shaped transition. Such a setting makes full use of the surface of the heat exchange tube to achieve heat exchange with maximum efficiency, and is easy to produce. processing.

Example 3

Referring to Fig. 1 and Fig. 5, the heat exchange tube 2 fixed in the housing 1 is a heat exchange tube with the second cross-sectional shape shown in Fig. 5. The cross-sectional shape of the heat exchange tube 2 is approximately rectangular, and a circle is set between adjacent two sides Arc-shaped transition connection; this setting is convenient for production and processing, and can also improve the heat exchange efficiency of the heat exchange tube.

Example 4

Referring to Figure 1 and Figure 6, the heat exchange tube 2 fixed in the casing 1 is a heat exchange tube with the third cross-sectional shape shown in Figure 6, and the cross-sectional shape of the heat exchange tube 2 is the first cross-sectional shape shown in Figure 4 On the basis of the above, the two opposite long sides 23 of the stainless steel tube are set to be arcs protruding from the inside to the outside, that is, the four surfaces of the stainless steel tubes are all set to be arc-shaped protruding arcs from the inside to the outside; and The arc radius of the long side 23 is much larger than the radius of the short side 22, so that the surface "collapse" will not occur on the long side 25, which is beneficial to processing.

Example 5

Referring to Fig. 1 and Fig. 7, the heat exchange tube 2 fixed in the shell 1 is the heat exchange tube with the fourth cross-sectional shape shown in Fig. The ratio of the axes is 3:1, preferably no more than 4:1; the heat exchange tube with an elliptical cross section is easy to process and has a good heat exchange effect.

Example 6

Referring to Fig. 8, a baffle 13 is provided in the shell 1; when the shell 1 is long, the proper setting of the baffle 13 can not only play the role of supporting the heat exchange tube 2, but also increase the flow rate of the coolant outside the tube. The disturbance enhances the heat exchange effect of the fluid inside and outside the tube.

Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred arrangement scheme, those skilled in the art should understand that the technical solution of the present invention can be implemented Modification or equivalent replacement without departing from the spirit and scope of the technical solutions of the present invention.

Claims (11)

1. the heat exchanger of a multitube journey includes housing, heat exchanger tube; Described housing two ends are respectively equipped with tube sheet, and the described heat exchanger tube mouth of pipe is welded on the tube sheet respectively and is parallel to each other and is fixed in the housing; It is characterized in that, form two-tube-pass by described heat exchanger tube, press the sequencing that heat transferring medium flows in heat exchanger tube, be divided into first tube side and second tube side, the described first tube side heat transferring medium outlet and the second tube side heat transferring medium import, form " U " shape loop by the end socket that is fixed on the housing, the heat exchanger tube quantity of described first tube side is more than the second tube side heat exchanger tube quantity; Described heat exchanger tube depth of section and width are unequal, and it is flat-shaped that shape is; Described heat exchanger tube is provided with groove along outer surface, and described groove is projection at the heat exchanger tube inner surface, and its shape is corresponding with groove shapes.

2. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described heat exchanger tube cross section is oval, and the ratio of long axis of ellipse and minor axis was less than 4: 1.

3. the heat exchanger of a kind of multitube journey according to claim 1, it is characterized in that, described heat exchanger tube cross section is flat, and two relative long limits are set to be the arc of projection from inside to outside, two relative minor faces for curved projection from inside to outside and with grow the limit and be connected for the circular arc transition.

4. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described heat exchanger tube cross sectional shape is made of two relative minor faces long limit relative with two, and wherein, described minor face is the camber line that protrudes from inside to outside, and described long limit is a straight line.

5. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described heat exchanger tube cross sectional shape is a rectangle, and connects for arc-shaped transition between the adjacent both sides.

6. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described heat exchanger tube is the stainless steel body.

7. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described groove is interrupted or continuously spiral setting along described heat exchange pipe external surface.

8. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described heat exchanger tube depth of groove is not less than 0.4mm.

9. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described groove is one or more its cross sectional shape to be set for " U " shape or " V " shape.

10, the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, described end socket is shaped as arc-shaped curved surface.

11. the heat exchanger of a kind of multitube journey according to claim 1 is characterized in that, is provided with deflection plate in the described heat exchanger shell.

Images