CN112146477A - Efficient spiral baffle plate shell-and-tube heat exchanger and heat exchange method - Google Patents

Abstract

The invention discloses a high-efficiency spiral baffle plate shell-and-tube heat exchanger and a heat exchange method, wherein the shell-and-tube heat exchanger comprises a shell, a shell side inlet pipe and a shell side outlet pipe which are arranged on the shell, a first tube plate and a second tube plate which are close to two sides of the shell, a left end socket and a right end socket, the left end socket is provided with the tube side inlet pipe, the right end socket is provided with the tube side outlet pipe, the shell is internally provided with a central tube and a plurality of heat exchange tubes and fixed on the left tube plate and the right tube plate, a continuous spiral baffle plate provided with jet holes is fixed on the central tube and is matched with the heat exchange tubes to form jet holes for enabling fluid to longitudinally flow, and the flow of the shell side. The invention can obviously improve the comprehensive heat exchange performance of the shell side of the shell-and-tube heat exchanger, reduce the dirt deposition of the shell side of the heat exchanger and ensure that the heat exchanger is more efficient and compact.

Description

A kind of high-efficiency spiral baffle shell-and-tube heat exchanger and heat exchange method

technical field

The invention relates to the technical field of tubular heat exchangers, in particular to a high-efficiency helical baffle shell-and-tube heat exchanger and a heat exchange method.

Background technique

Shell-and-tube heat exchangers, as an important equipment for realizing technological process, are widely used in various industrial fields such as petroleum smelting, energy, chemical industry, etc., usually accounting for 35-40% of the total equipment investment. The shell and tube heat exchanger is a kind of partition heat exchanger. The cold and hot fluids are located on both sides of the wall of the heat exchange tube bundle, and the heat is transferred from the hot fluid to the cold fluid through the wall of the tube bundle. A baffle plate is arranged on the shell side, the baffle plate provides support for the tube bundle, and at the same time makes the shell side fluid flow according to a specific channel to improve the heat transfer characteristics of the shell side fluid. The heat exchanger is simple in structure, low in cost, easy to clean scale, and can be used under high temperature and high pressure.

The traditional arcuate baffle shell-and-tube heat exchanger has its inherent shortcomings: the shell-side flow is repeatedly compressed and released, and the flow direction is changed with 90° turning for many times, resulting in high pressure loss and high pump work. There is a flow dead zone behind the baffle, which is easy to scale, resulting in a decrease in the local heat transfer coefficient. Therefore, the traditional arcuate baffle shell-and-tube heat exchanger cannot meet the requirements of modern industry for high efficiency, low resistance and controllability.

In recent years, some scholars have proposed helical baffle shell-and-tube heat exchangers, which effectively solve the problems of flow dead zone and shell-side scaling of arcuate baffle shell-and-tube heat exchangers. However, the turbulence intensity of the helical flow of the fluid on the shell side is smaller than that of the "Z"-shaped flow, so that the comprehensive heat exchange performance of the shell-and-tube heat exchanger cannot be fully exerted. At the same time, the existing technologies for improving the heat transfer performance of the shell-side fluid are concentrated on the single-flow method of the shell-side. The cross flow of the heat exchanger greatly improves the comprehensive heat transfer performance of the heat exchanger.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-efficiency helical baffle shell-and-tube heat exchanger and a heat exchange method to solve the above-mentioned problems in the prior art, which is a kind of exquisite structure design, good heat exchange effect and high safety performance. High-efficiency spiral baffle shell-and-tube heat exchanger and heat exchange method. There are jet holes on the continuous spiral baffle plate, so that the fluid on the shell side is divided into longitudinal flow and spiral flow. Great improvement. At the same time, a part of the fluid scours the tube bundle longitudinally through the jet holes, which further reduces the flow resistance on the shell side, so that the comprehensive heat exchange performance of the obtained heat exchanger is better than that of the general shell-and-tube heat exchanger.

For achieving the above object, the present invention provides the following scheme:

The invention provides a high-efficiency helical baffle shell-and-tube heat exchanger, which includes a shell, a tube plate 1 and a tube plate 2 arranged at both ends of the shell, and a left head sealingly installed on the outer side of the first tube plate. and the right head sealingly installed on the outer side of the second tube sheet, the shell side inlet pipe and the shell side outlet pipe are respectively installed on both sides of the shell, the tube side inlet pipe is installed on the left head, the A pipe-side outlet pipe is installed on the right head, and a continuous spiral baffle plate with jet holes is installed in the center of the shell. The jet holes are circumferentially distributed on the spiral plate of the continuous spiral baffle plate. The jet holes on the plate are opposite one by one and are coaxial, and the center of the shell is provided with a center tube, which is used to fix the continuous spiral baffle plate and is fixed to the tube plate one and the tube Between the two plates, a plurality of parallel heat exchange tubes are axially arranged in the shell, and the heat exchange tubes pass through the jet holes of the continuous spiral baffles in parallel and are fixed to the first and second tube plates. On the second tube plate, the continuous spiral baffle plate and the heat exchange tube cooperate with each other to form jet holes for the longitudinal flow of the fluid.

Preferably, the shape of the jet holes on the continuous helical baffle plate is a grid shape, a triangle shape, a square shape, a polygon shape, or a petal shape.

Preferably, the relationship between the inscribed circle diameter D ₀ and the circumscribed circle diameter D ₁ of the jet hole shape and the jet hole pitch P _t is: D ₀ <D ₁ <P _t .

Preferably, the inscribed circle of the jet hole is coaxial with the heat exchange tube.

Preferably, in addition to being supported by the first tube sheet and the second tube sheet, the heat exchange tube is also supported by the inner edge protrusion of the jet hole.

Based on the above-mentioned high-efficiency helical baffle shell-and-tube heat exchanger, the present invention also provides a heat exchange method for the high-efficiency helical baffle shell-and-tube heat exchanger, comprising the following steps:

1) The tube-side fluid flows in from the tube-side inlet tube, exchanges heat with the shell-side fluid through the heat exchange tube, and finally flows out from the tube-side outlet tube;

2) The fluid flows into the shell from the shell side inlet pipe, a part of the fluid scours the tube bundle in a spiral flow along the helical baffle, and a part of the fluid scours the heat exchange tube bundle longitudinally through the jet holes on the continuous spiral baffle plate with jet holes. , the overall flow form of the shell-side fluid is a cross-flow formed by the combination of longitudinal flow and spiral flow, which flows out from the shell-side outlet tube after heat exchange with the tube-side fluid.

Preferably, since the jet holes are opened on the continuous helical baffle, the inner edges of the jet holes are also helical, and the longitudinal flow of the part of the fluid is a helical longitudinal flow.

The present invention has achieved the following beneficial technical effects with respect to the prior art:

(1) Compared with the general shell and tube heat exchanger, the shell and tube heat exchanger of the present invention has no flow dead zone at all, which greatly reduces the probability of fouling deposition on the shell side, thereby prolonging the service life of the heat exchanger.

(2) The fluid flow on the shell side of the shell and tube heat exchanger of the present invention is a cross flow composed of a longitudinal flow and a spiral flow, which further reduces the probability of the fluid scouring the tube bundle laterally. Compared with the general continuous spiral baffle shell and tube heat exchanger The heat exchanger further reduces the vibration of the tube bundle, and the structural stability of the heat exchanger is better.

(3) The fluid flow on the shell side of the shell-and-tube heat exchanger of the present invention is a cross flow composed of longitudinal flow and spiral flow, and the comprehensive heat exchange performance of the heat exchanger is improved, making the shell-and-tube heat exchanger widely used in the energy and chemical industries. Heaters are more efficient and compact.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the overall structure schematic diagram of the high-efficiency helical baffle shell-and-tube heat exchanger in the present invention;

Fig. 2 is the structural representation inside the high-efficiency helical baffle shell-and-tube heat exchanger in the present invention;

3 is a side view of the baffle of the high-efficiency helical baffle shell-and-tube heat exchanger in the present invention;

Fig. 4 (a) is a kind of structural representation of the baffle plate of the high-efficiency helical baffle plate shell-and-tube heat exchanger of the present invention;

Figure 4 (b) is another structural schematic diagram of the baffle of the high-efficiency helical baffle shell-and-tube heat exchanger of the present invention;

Figure 5 is a streamline diagram of a traditional continuous helical baffle shell-and-tube heat exchanger when the shell-side inlet mass flow is 0.5kg/s;

6 is a streamline diagram of the high-efficiency helical baffle shell-and-tube heat exchanger of the present invention when the shell-side inlet mass flow rate is 0.5 kg/s;

Figure 7 is a graph showing the relationship between the comprehensive performance parameter h/Δp of the heat exchanger and the mass flow rate of the shell side inlet;

Figure 8 is a graph showing the relationship between the efficiency coefficient EEC of the heat exchanger and the inlet mass flow rate. The comparison heat exchanger is a traditional continuous spiral baffle shell-and-tube heat exchanger;

In the figure: 1. Inlet pipe on tube side; 2. Left head; 3. Tube sheet 1; 4. Inlet pipe on shell side; 5. Shell; 6. Heat exchange tube; 7. Continuous spiral baffle plate; 8. Shell side outlet pipe; 9. Tube sheet two; 10. Right head; 11. Tube side outlet pipe; 12. Center pipe; 13. Jet hole.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a high-efficiency helical baffle shell-and-tube heat exchanger and a heat exchange method to solve the problems existing in the prior art.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

The high-efficiency helical baffle shell-and-tube heat exchanger in this embodiment, as shown in Figures 1-8, includes a shell 5, a tube sheet 1 3 and a tube sheet 2 9 arranged at both ends of the shell 5, and a tube sheet 1 3 and the tube sheet 2 9 are used to fix the heat exchange tube 6 and the central tube 12, the left head 2 installed on the outside of the tube sheet 1 3 and the right head 10 sealed on the outside of the tube sheet 2 9. The shell side inlet pipe 4 and the shell side outlet pipe 8 are respectively installed on both sides.

As shown in FIG. 2 , a continuous helical baffle 7 with jet holes 13 is installed in the center of the casing 5, and the jet holes 13 are circumferentially distributed on the helical plate of the continuous helical baffle 7. The jet holes 13 on each helical plate One-to-one and coaxial, the center of the shell 5 is provided with a center tube 12, the center tube 12 is used to fix the continuous spiral baffle 7, and is fixed between the tube sheet 1 3 and the tube sheet 2 9, the shell 5 There are also a plurality of parallel heat exchange tubes 6 arranged in the axial direction. The heat exchange tubes 6 pass through the jet holes 13 of the continuous spiral baffle plate 7 in parallel, and are fixed on the tube plate one 3 and the tube plate two 9. The flow plate 7 and the heat exchange tubes 6 cooperate with each other to form jet holes 13 for the longitudinal flow of the fluid. Viewed in the axial direction of the heat exchange tubes 6, each heat exchange tube 6 is coaxial with the row of jet holes 13 through which it passes.

As shown in Figure 3, the shape of the jet holes 13 on the continuous helical baffle plate 7 is a grid-shaped or triangular or square or polygonal or petal-shaped; the inscribed circle of the jet holes 13 is coaxial with the heat exchange tube 6; in order to To facilitate the selection and arrangement of the heat exchange tubes 6, the relationship between the diameter D ₀ of the inscribed circle, the diameter D ₁ of the circumscribed circle and the pitch P _t of the jet hole 13 is: D ₀ <D ₁ <P _t , which not only ensures the stability of the heat exchanger, but also facilitates the selection and installation of the heat exchange tube 6 .

As shown in Figure 4, it is a continuous spiral baffle 7 with jet holes according to a specific embodiment of the present invention, the baffle helix angle is 15.8°, and the number of cycles is 6. The starting number is 5, and the number of protrusions on the inner edge of the jet hole in Figure 4(b) is 3. In addition to being supported by the first tube plate and the second tube plate, the heat exchange tube is also supported by the inner edge protrusion of the jet hole.

Based on the above-mentioned high-efficiency helical baffle shell-and-tube heat exchanger, the present embodiment also provides a heat exchange method for a high-efficiency helical baffle shell-and-tube heat exchanger, and the specific process is as follows:

The tube-side fluid enters the left head 2 of the heat exchanger from the tube-side inlet tube 1. The fluid is evenly distributed in the left head 2 into multiple fluids and enters the heat exchange tube 6. In the heat exchange tube 6, it passes through the tube wall and the shell side. After the fluid exchanges heat, it enters the right head 10 and flows out through the pipe-side outlet pipe 11 . The shell-side fluid enters the shell side of the heat exchanger from the shell-side inlet pipe 4, wherein a part of the fluid scours the tube bundle in a spiral flow along the helical baffle, and a part of the fluid passes through the jet hole 13 longitudinally between the baffle and the heat exchange tube 6 By scouring the tube bundle, the shell-side fluid generally exchanges heat with the fluid in the heat exchange tube 6 in a cross-flow mode composed of spiral flow and longitudinal flow, which enhances the turbulence of the shell-side fluid. The pressure drop in the pure spiral flow mode improves the comprehensive heat exchange performance of the shell-side fluid. After the heat exchange is completed, the shell-side fluid flows out of the heat exchanger through the shell-side outlet pipe 8 .

Numerical research on shell and tube heat exchangers is a computer-based experimental research. At present, various researchers rely on the mature commercial software ANSYS to carry out a large number of numerical experiments. It is quite mature to use this method to study the flow heat transfer characteristics of shell and tube heat exchangers. The present invention, namely a high-efficiency helical baffle shell-and-tube heat exchanger, is numerically studied, and the comparison object is the traditional continuous helical baffle shell-and-tube heat exchanger. In the study, the method of controlling variables was adopted, and the two heat exchangers kept the same shell structure size, shell side inlet and outlet pipe structure size, heat exchange tube structure size, heat exchange tube arrangement and the same baffle plate Helix angle, helix cycle number, installation method, etc. The number of protrusions on the inner edge of the jet hole of the high-efficiency helical baffle shell-and-tube heat exchanger in this embodiment is 3, that is, the structure of the baffle is shown in Figure 4(b). In the numerical experiment, water was used as the heat exchange medium on the shell side. Under the condition that the inlet temperature of the heat exchanger and the temperature of the heat exchange tube wall were kept constant, two kinds of heat exchangers were simulated when the inlet flow rate of the heat exchanger was 0.5-1.5 kg/s. Flow heat transfer characteristics on the shell side of the heat exchanger. The model inlet is the velocity inlet, and the inlet temperature is 300K. The outlet is a pressure outlet and suppresses backflow. The shell is an adiabatic wall with good heat preservation. The baffles are set as the coupled walls and participate in the convective heat transfer between the fluid and the baffles and the heat conduction inside the solid.

As shown in Figure 4 and Figure 5, when the inlet mass flow rate is 0.5kg/s, the flow rates of the traditional continuous spiral baffle shell-and-tube heat exchanger and the high-efficiency spiral baffle shell-and-tube heat exchanger of this embodiment are respectively shown. line graph. It can be clearly seen from the two figures that the fluid flow on the shell side of the traditional continuous spiral baffle shell-and-tube heat exchanger is in the state of pure spiral flow, while the fluid flow on the shell side of the high-efficiency spiral baffle shell-and-tube heat exchanger is in the state of pure spiral flow. It is a cross flow composed of helical flow and longitudinal flow. The longitudinal flow scours the tube bundle longitudinally, destroys the boundary layer on the surface of the tube bundle, and enhances the turbulent flow intensity of the fluid on the shell side. At the same time, the flow mode of the longitudinal flow reduces the pressure drop. The cross-flow of flow composition enhances the overall heat transfer performance on the shell side.

The heat exchange Q between the shell side fluid and the heat exchange tube wall is defined as:

Q=M·c _p (T _in -T _out )

where _cp is the specific heat capacity of the shell-side fluid, in J/(kg·K), M is the mass flow rate of the shell-side fluid, in kg/s, and T _in and T _out are the inlet temperatures of the shell-side fluid, respectively and outlet temperature in K.

The convective heat transfer coefficient h of the shell side fluid is defined as:

where A is the total area of heat transfer, ΔT _m is the logarithmic mean temperature difference between the tube wall and the fluid, and they are defined as:

A=N _t ·π·d·L

where N _t is the number of heat exchange tubes, d is the outer diameter of the heat exchange tubes, L is the length of the heat exchange tube bundle, ΔT _max and ΔT _min are the maximum and minimum temperature differences between the tube wall and the fluid, respectively.

The pressure drop on the shell side of the heat exchanger is defined as:

Δp=p _in -p _out

Efficiency coefficient EEC is used to evaluate the ratio of the increase in revenue after the heat exchanger is strengthened to the increase in pump power consumed. If the value is greater than 1, it indicates that the improved heat exchanger is effective. The definition of EEC is as follows:

In the formula, Q is the heat exchange amount of the high-efficiency spiral baffle shell-and-tube heat exchanger in this embodiment, Q ₀ is the heat exchange amount of the traditional continuous spiral baffle shell-and-tube heat exchanger, and P is this embodiment The power consumption of the high-efficiency spiral baffle shell and tube heat exchanger, P ₀ is the power consumption of the traditional continuous spiral baffle shell and tube heat exchanger.

As shown in FIG. 6 , h/ΔP of the high-efficiency helical baffle shell-and-tube heat exchanger of the present embodiment and the conventional continuous helical baffle shell-and-tube heat exchanger. h/ΔP is the heat transfer coefficient per unit pressure drop, which is used to characterize the comprehensive heat transfer performance of the heat exchanger. It can be seen from Figure 6 that the h/ΔP of the two heat exchangers decreases with the increase of the inlet mass flow. At the same time, under the same inlet mass flow conditions, the h/ΔP of the high-efficiency helical baffle shell-and-tube heat exchanger /ΔP is higher than that of the traditional continuous spiral baffle shell-and-tube heat exchanger. In the flow range of 0.5-1.5kg/s, the average h/ΔP of the high-efficiency spiral baffle shell-and-tube heat exchanger is higher than that of the traditional continuous spiral baffle heat exchanger. The flow plate shell-and-tube heat exchanger is 12.78% higher, which shows that the high-efficiency helical baffle shell-and-tube heat exchanger of this embodiment is more efficient and compact.

As shown in Figure 7, the relationship between the efficiency coefficient and the inlet mass flow rate obtained by comparing the high-efficiency helical baffle shell-and-tube heat exchanger of the present embodiment and the traditional continuous helical baffle shell-and-tube heat exchanger is shown in the figure. It can be seen that the efficiency coefficient is greater than 1, indicating that the high-efficiency spiral baffle shell and tube heat exchanger of the present invention is more efficient than the traditional continuous spiral baffle shell and tube heat exchanger.

The present invention uses specific examples to illustrate the principles and implementations of the present invention, and the descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention; There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (7)

1. A high-efficient spiral baffling board shell and tube heat exchanger which characterized in that: the heat exchanger comprises a shell, a first tube plate and a second tube plate which are arranged at two ends of the shell, a left seal head and a right seal head which are arranged at the outer sides of the first tube plate and are in sealing installation, a shell side inlet pipe and a shell side outlet pipe are respectively arranged at two sides of the shell, a tube side inlet pipe is arranged on the left seal head, a tube side outlet pipe is arranged on the right seal head, a continuous spiral baffle plate with jet holes is arranged at the center of the shell, the jet holes are circumferentially distributed on spiral plates of the continuous spiral baffle plate, the jet holes on each spiral plate are opposite to each other and coaxial, a central tube is arranged at the center of the shell and is used for fixing the continuous spiral baffle plate and is fixed between the first tube plate and the second tube plate, a plurality of parallel heat exchange tubes are axially arranged in the shell and parallelly penetrate through the jet holes of the, and the continuous spiral baffle plate and the heat exchange tube are mutually matched to form a jet hole for fluid to longitudinally flow.

2. A high efficiency spiral baffle shell and tube heat exchanger as set forth in claim 1 wherein: the hole shape of the jet hole on the continuous spiral baffle plate is in a folded grid shape, a triangular shape, a square shape, a polygonal shape or a petal shape.

3. A high efficiency spiral baffle shell and tube heat exchanger as set forth in claim 1 wherein: the diameter D of the inscribed circle of the hole shape of the jet hole₀Diameter of circumscribed circle D₁Pitch P of jet hole_tThe relationship between them is: d₀<D₁<P_t。

4. A high efficiency spiral baffle shell and tube heat exchanger as set forth in claim 1 wherein: the inscribed circle of the jet hole is coaxial with the heat exchange tube.

5. A high efficiency spiral baffle shell and tube heat exchanger as set forth in claim 1 wherein: the heat exchange tube is supported by the first tube plate and the second tube plate and is also supported by the inner edge of the jet hole in a protruding mode.

6. A method of exchanging heat for a high efficiency spiral baffle shell and tube heat exchanger as recited in any one of claims 1-5 comprising the steps of:

1) the fluid on the tube side flows in from the inlet tube on the tube side, exchanges heat with the fluid on the shell side through the heat exchange tube, and finally flows out from the outlet tube on the tube side;

2) fluid flows into the shell through the shell side inlet pipe, one part of the fluid washes the tube bundle in a spiral flowing mode along the spiral baffle plate, one part of the fluid washes the heat exchange tube bundle longitudinally through the jet holes on the continuous spiral baffle plate with the jet holes, and the total flowing mode of the shell side fluid is cross flow formed by combining longitudinal flow and spiral flow, and the shell side fluid flows out through the shell side outlet pipe after heat exchange with the tube side fluid.

7. A method for exchanging heat in a high efficiency spiral baffle shell and tube heat exchanger as recited in claim 6 wherein: because the jet hole is arranged on the continuous spiral baffle plate, the inner edge of the jet hole is also in a spiral shape, and the longitudinal flow of a part of fluid is spiral longitudinal flow.

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