Condensation secondary heat exchanger and design method of flue gas flow deflector of condensation secondary heat exchanger

Abstract

The invention discloses a condensation secondary heat exchanger and a design method of flue gas flow deflectors of the condensation secondary heat exchanger, and relates to the technical field of condensation secondary heat exchangers. The flue gas guide plate is clamped between the middle guide plate and the opposite side shell wall of the shell by the two side walls of the shell and is arranged in the upper cavity and the lower cavity in a crossing manner, so that when the flue gas turns to flow into the upper cavity from the lower cavity, part of the flue gas is guided into a lower heat absorption pipe area of the upper cavity, and the heat absorption efficiency of the flue gas is improved. The flue gas is discharged from the flue gas outlet after flowing through the lower heat absorption pipe, so that the flue gas is redistributed when flowing from the lower cavity to the upper cavity, a flowing dead zone generated when the flue gas automatically circulates is avoided, the actual flowing sectional area of the flue gas is increased, and the heat exchange efficiency of the condensation secondary heat exchanger is improved.

Description

Technical Field

[0001] The invention relates to the technical field of condensing secondary heat exchangers, and in particular to a design method of a condensing secondary heat exchanger and a smoke guide plate thereof. Background Art

[0002] At present, the market share of household gas wall-mounted boilers is also increasing year by year. Existing wall-mounted boilers are mainly heated by natural gas as fuel. The flue gas generated by combustion is heated by the main heat exchanger to a temperature of about 120-150℃. If it is directly discharged into the atmosphere, the residual heat of water vapor in the flue gas will be wasted, which has a great impact on the thermal efficiency of the wall-mounted boiler. Therefore, a secondary heat exchanger is installed at the tail of the flue of the wall-mounted boiler to recover the residual heat in the flue gas and improve the efficiency of the wall-mounted boiler.

[0003] In the prior art, the shell of the condensing secondary heat exchanger is divided into an upper chamber and a lower chamber. When the flue gas flows on the shell side, it first flows into the lower chamber from the flue gas inlet. When it flows near the outer shell wall, the flue gas flow direction reverses 180 degrees and flows upward into the upper chamber. Then, it flows out from the flue gas outlet and is discharged into the atmosphere under the suction of the fan.

[0004] However, the heat exchange efficiency of the current condensing secondary heat exchanger is low. Summary of the invention

[0005] Based on this, it is necessary to provide a design method for a condensing secondary heat exchanger and its flue gas guide plate to address the above technical problems.

[0006] The present invention adopts the following technical solutions:

[0007] The present invention provides a condensing secondary heat exchanger, comprising: a shell, a plurality of heat absorbing tubes, an intermediate guide plate and a flue gas guide plate;

[0008] The shell is provided with a smoke inlet and a smoke outlet, and a plurality of heat absorbing tubes are provided in the shell;

[0009] The intermediate guide plate is arranged between the smoke inlet and the smoke outlet, and the plurality of heat absorbing tubes are separated into upper and lower parts by the intermediate guide plate, and the interior of the shell is divided into an upper chamber connected to the smoke outlet and a lower chamber connected to the smoke inlet, and there is a gap between the intermediate guide plate and the opposite shell wall, so as to form a passage from the smoke inlet to the smoke outlet;

[0010] The smoke guide plate is fixed between the middle guide plate and the opposite shell wall, is clamped by the two side walls of the shell, and is arranged across the upper chamber and the lower chamber. It is used to guide part of the smoke into the lower heat absorption pipe area of ​​the upper chamber when the smoke turns from the lower chamber to flow to the upper chamber, so that it flows through the lower heat absorption pipe area and is discharged from the smoke outlet.

[0011] Optionally, the smoke guide plate is an arc-shaped guide structure, with two arc ends respectively located in the upper chamber and the lower chamber, with the concave side facing the middle guide plate and the convex side facing the shell wall opposite to the middle guide plate.

[0012] Optionally, the smoke guide plate further includes two fins, which are respectively fixedly connected to the arc end in the upper chamber and the arc end in the lower chamber, and the other ends of the two fins are arranged near the shell wall to form a wave-shaped guide structure.

[0013] The present invention provides a design method for a flue gas guide plate in a condensing secondary heat exchanger, comprising:

[0014] According to the physical object of the condensing secondary heat exchanger, a geometric model of the condensing secondary heat exchanger is constructed;

[0015] Determine the flue gas inlet velocity, flue gas inlet temperature, total cold water inlet flow rate of each heat absorption tube in the condensing secondary heat exchanger, cold water inlet temperature and numerical simulation boundary conditions of flue gas circulation;

[0016] According to the changes in the thermal physical properties of the flue gas caused by the temperatures at the inlet and outlet sides of the flue gas, the physical properties of the flue gas are fitted as a physical property parameter function input that changes with temperature;

[0017] A condensation model is constructed according to the geometric model of the condensing secondary heat exchanger, the numerical simulation boundary conditions and the physical parameter function input, and a numerical simulation is performed according to the target flue gas guide vane and the condensation model to determine the degree of optimization of the heat exchange efficiency of the condensing secondary heat exchanger by the target flue gas guide vane;

[0018] Taking the maximum optimization degree of the heat exchange efficiency of the condensing secondary heat exchanger by the target flue gas guide vane as the optimization goal, the design parameters of the target flue gas guide vane are optimized, and the optimal design parameters of the flue gas guide vane are determined through multiple rounds of iterative numerical simulation.

[0019] Optionally, the numerical simulation boundary conditions for determining the flue gas inlet velocity, the flue gas inlet temperature, the total cold water inlet flow rate of each heat absorption tube in the condensing secondary heat exchanger, the cold water inlet temperature and the flue gas circulation specifically include:

[0020] Determine that the flue gas inlet of the secondary condensing heat exchanger is a constant temperature velocity inlet, the cold water inlet of each heat absorption tube in the secondary condensing heat exchanger is a mass flow inlet, the flue gas outlet and the cold water outlet are pressure outlets, the inner and outer walls of each heat absorption tube are applied with coupled boundary conditions, and the shell wall of the secondary condensing heat exchanger is applied with adiabatic boundary conditions;

[0021] For each process of cold water from the cold water inlet to the cold water outlet, the average temperature and average flow rate of the process outlet are taken as the inlet boundary conditions of the next process;

[0022] Among them, the flue gas inlet velocity is 8-12m·s -1The flue gas inlet temperature is 393.15K, and the total flow rate of cold water inlet is 10-20kg·min -1 The cold water inlet temperature is 293K.

[0023] At least one of the above technical solutions adopted by the present invention can achieve the following beneficial effects:

[0024] When the condensing secondary heat exchanger is not equipped with a flue gas guide plate, the flue gas is in a state of self-circulation, usually flowing from the lower chamber along the opposite side of the shell wall of the middle guide plate to the upper chamber, and then concentratedly flowing through the upper heat absorption pipe area of ​​the upper chamber and discharged from the flue gas outlet, resulting in a flow dead zone in the lower heat absorption pipe area of ​​the upper chamber. The temperature in this area is much lower than the flue gas inlet temperature and close to the cooling water temperature, that is, the convective heat exchange intensity in the area is weak. At the same time, the vortex in the flow dead zone hinders the flow of the incoming flue gas, resulting in the actual flow cross-sectional area of ​​the flue gas in the upper chamber being only the upper area of ​​the theoretical flow cross-sectional area, and the flow resistance of the flue gas is significantly increased.

[0025] The present invention sandwiches a smoke guide plate between the middle guide plate and the opposite shell wall of the shell with the side walls of the shell, and makes it straddle the upper chamber and the lower chamber. When the smoke turns to flow from the lower chamber to the upper chamber, part of the smoke is guided into the lower heat absorption pipe area of ​​the upper chamber, and is discharged from the smoke outlet after passing through the lower heat absorption pipe, thereby redistributing the smoke when it flows from the lower chamber to the upper chamber, avoiding the flow dead zone generated when the smoke circulates by itself, increasing the actual flow cross-sectional area of ​​the smoke, and improving the heat exchange efficiency of the condensing secondary heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 A schematic diagram of a condensing secondary heat exchanger provided by the present invention;

[0028] Figure 2 A schematic diagram of a smoke guide plate provided by the present invention;

[0029] Figure 3 A schematic flow chart of a design method for a condensing secondary heat exchanger and a flue gas guide plate thereof provided by the present invention;

[0030] Figure 4 A schematic diagram of a geometric model of a condensing secondary heat exchanger provided by the present invention;

[0031] Figure 5 A schematic diagram of a calculation area of ​​a condensing secondary heat exchanger provided by the present invention;

[0032] Figure 6 A schematic diagram of a condensation process provided by the present invention;

[0033] Figure 7 A comparison chart of numerical calculation and experimental results provided by the present invention;

[0034] Figure 8 A schematic diagram of a temperature cloud map provided by the present invention;

[0035] Fig. 9 The present invention provides a schematic diagram of a flue gas velocity cloud diagram. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] At present, when the flue gas flow direction is deflected, a local flow dead zone will be generated near the tube bundle located at the lower part of the upper chamber. The temperature in this area is much lower than the flue gas inlet temperature and close to the cooling water temperature, which indicates that the convective heat exchange intensity in this area is weak. At the same time, the vortex in the flow dead zone hinders the flow of the incoming flue gas, resulting in the actual flow cross-sectional area of ​​the flue gas in the upper chamber being only about 1 / 3 of the theoretical flow cross-sectional area, and the flow resistance of the flue gas is significantly increased, resulting in a low heat exchange efficiency of the condensing secondary heat exchanger.

[0038] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0039] Figure 1 A schematic diagram of a condensing secondary heat exchanger in the present invention is shown in FIG. Figure 1 It can be seen that the condensing secondary heat exchanger includes a shell 100 and a smoke guide plate 200, wherein a smoke inlet and a smoke outlet are arranged on the shell 100. Figure 1 The shell 100 is also provided with a plurality of heat absorbing tubes 101, and the intermediate guide plate 102 is provided between the smoke inlet and the smoke outlet. The intermediate guide plate 102 separates the plurality of heat absorbing tubes 101 up and down, and separates the interior of the shell 100 into an upper chamber connected to the smoke outlet and a lower chamber connected to the smoke inlet, and there is a gap between the intermediate guide plate 102 and the opposite shell wall, forming a passage from the smoke inlet to the smoke outlet.

[0040] The smoke guide plate 200 is fixed between the middle guide plate 102 and the opposite shell wall, clamped by the two side walls of the shell 100, and straddled between the upper chamber and the lower chamber. It is used to guide part of the smoke into the lower heat absorption pipe area of ​​the upper chamber when the smoke turns from the lower chamber to flow to the upper chamber, so that it flows through the lower heat absorption pipe area and is discharged from the smoke outlet.

[0041] Furthermore, in one or more embodiments of the present invention, the smoke guide plate 200 may be an arc-shaped guide structure, with two arc ends respectively located in the upper chamber and the lower chamber, with the concave side facing the middle guide plate 102 and the convex side facing the opposite shell wall of the middle guide plate 102.

[0042] Furthermore, in one or more embodiments of the present invention, the smoke guide plate 200 may also include two fins, which are respectively fixedly connected to the arc end in the upper chamber and the arc end in the lower chamber, and the other ends of the two fins are arranged near the shell wall to form a wavy guide structure.

[0043] The flue gas guide plate 200 can be set as an extremely thin iron sheet, so a raised slot can be arranged on the shell of the condensing secondary heat exchanger. During the installation process, the flue gas guide plate 200 is inserted into the slot to be arranged in the secondary heat exchanger, which is easy to install.

[0044] Figure 2 This is a schematic diagram of a smoke guide plate in the present invention. Figure 2 The left side in the middle is a schematic diagram of the arc-shaped smoke guide. Figure 2 The right side of the middle is a schematic diagram of a wavy smoke guide plate. The specific style of the smoke guide plate can be determined according to needs. The present invention is only an example and does not limit this.

[0045] When the condensing secondary heat exchanger is not equipped with a flue gas guide plate, the flue gas is in a state of self-circulation, usually flowing from the lower chamber along the opposite side of the shell wall of the middle guide plate to the upper chamber, and then concentratedly flowing through the upper heat absorption pipe area of ​​the upper chamber and discharged from the flue gas outlet, resulting in a flow dead zone in the lower heat absorption pipe area of ​​the upper chamber. The temperature in this area is much lower than the flue gas inlet temperature and close to the cooling water temperature, that is, the convective heat exchange intensity in the area is weak. At the same time, the vortex in the flow dead zone hinders the flow of the incoming flue gas, resulting in the actual flow cross-sectional area of ​​the flue gas in the upper chamber being only the upper area of ​​the theoretical flow cross-sectional area, and the flow resistance of the flue gas is significantly increased.

[0046] The present invention sandwiches a smoke guide plate between the middle guide plate and the opposite shell wall of the shell with the side walls of the shell, and makes it straddle the upper chamber and the lower chamber. When the smoke turns to flow from the lower chamber to the upper chamber, part of the smoke is guided into the lower heat absorption pipe area of ​​the upper chamber, and is discharged from the smoke outlet after passing through the lower heat absorption pipe, thereby redistributing the smoke when it flows from the lower chamber to the upper chamber, avoiding the flow dead zone generated when the smoke circulates by itself, increasing the actual flow cross-sectional area of ​​the smoke, and improving the heat exchange efficiency of the condensing secondary heat exchanger.

[0047] In addition, the present invention also provides a design method for a flue gas guide plate in a condensing secondary heat exchanger, such as Figure 3 As shown, Figure 3 The present invention is a schematic flow chart of a design method for a flue gas guide vane in a condensing secondary heat exchanger, which specifically includes the following steps:

[0048] S101: Construct a geometric model of the condensing secondary heat exchanger based on the actual condensing secondary heat exchanger.

[0049] In practical applications, when designing a flue gas guide vane, the basic shape of the flue gas guide vane and its installation position in the condensing secondary heat exchanger can be determined first, and then a numerical simulation of the flue gas circulation and heat exchange can be performed based on the basic shape to optimize the design parameters of the flue gas guide vane.

[0050] Based on this, the server of the business platform can first abstract the model according to the specific condensing secondary heat exchanger to obtain the geometric model of the condensing secondary heat exchanger, thereby serving the subsequent numerical simulation process.

[0051] The physical model of the secondary heat exchanger for condensation is reasonably simplified for simulation calculation. Specifically, the flue gas flows on the shell side of the condensation secondary heat exchanger, and the cold water has multiple processes in the heat absorption tube, and flows back and forth in the tube. After each process, the cold water flows into the distribution bin for flow redistribution. The distribution bin structure is relatively complex and has little effect on the flow, so the distribution bin is deleted and only the tube bundle layout characteristics of the secondary heat exchanger are retained. The simplified collective model is as follows Figure 4 As shown, Figure 4 It is a schematic diagram of a geometric model of a condensing secondary heat exchanger in the present invention.

[0052] The server mentioned in the present invention may be a server set on a business platform, or a device such as a desktop computer, a notebook computer, etc. that can execute the solution of the present invention. For the convenience of description, the following description is only based on the server as the execution subject.

[0053] S102: Determine the flue gas inlet velocity, flue gas inlet temperature, the total cold water inlet flow rate of each heat absorption tube in the condensing secondary heat exchanger, the cold water inlet temperature and the numerical simulation boundary conditions of the flue gas circulation.

[0054] S103: According to the change of the thermal physical property of the flue gas caused by the temperature at the inlet and outlet sides of the flue gas, the physical property of the flue gas is fitted into a physical property parameter function input that changes with temperature.

[0055] After determining the geometric structure of the condensing secondary heat exchanger, the server can further determine the boundary conditions and physical property conditions of the numerical simulation.

[0056] Specifically, the server can determine that the flue gas inlet of the secondary condensing heat exchanger is a constant temperature velocity inlet, the cold water inlet of each heat absorption tube in the secondary condensing heat exchanger is a mass flow inlet, the flue gas outlet and the cold water outlet are pressure outlets, the inner and outer walls of each heat absorption tube are applied with coupled boundary conditions, and the shell wall of the secondary condensing heat exchanger is applied with adiabatic boundary conditions.

[0057] For each process of cold water from the cold water inlet to the cold water outlet, the average surface temperature and average flow rate at the process outlet are taken as the inlet boundary conditions of the next process.

[0058] Among them, the flue gas inlet velocity is 8-12m·s -1 The flue gas inlet temperature is 393.15K, and the total flow rate of cold water inlet is 10-20kg·min -1 The cold water inlet temperature is 293K.

[0059] Of course, in order to allow the flue gas to develop fully and prevent the backflow of the tail flue gas, extension sections can also be set before and after the tube bundle.

[0060] Figure 5 is a schematic diagram of the calculation area of ​​a condensing secondary heat exchanger in the present invention, Figure 5 It can be seen that for the heat absorption tube, cold water flows in from the cold water inlet, flows through the processes numbered 1-4 in sequence, and finally flows out from the cold water outlet.

[0061] In addition, due to the large temperature difference between the inlet and outlet of the flue gas side, in order to ensure the accuracy of the calculation, the change in the thermal properties of the flue gas caused by the temperature change needs to be considered. Therefore, based on the NIST database, the present invention fits the flue gas properties as a function that changes with temperature and inputs it into Fluent. The flue gas property function is shown in Table 1.

[0062] Table 1 Flue gas thermal properties

[0063] Physical properties Polynomial function (300K <T<600K) <![CDATA[ρ / kg·m -3 ]]> <![CDATA[3.03-0.01T+1.46×10 -5 T 2 -7.76×10 -9 T 3 ]]> <![CDATA[cp / J·kg -1 ·K -1 ]]> <![CDATA[1090.63-0.11T+6.02×10 -4 T2 -2 .82×10 -7 T 3 ]]> <![CDATA[μ / kg·m -1 ·s -1 ]]> <![CDATA[5.60×10 -4 +8.42×10 -5 T-2.30×10 -8 T 2 +9.28×10 -12 T 3 ]]> <![CDATA[λ / W·m -1 ·K -1 ]]> <![CDATA[9.47×10 -7 +5.96×10 -8 T-2.92×10 -11 T 2 +1.01×10 -14 T 3 ]]>

[0064] S104: Construct a condensation model according to the geometric model of the condensing secondary heat exchanger, the numerical simulation boundary conditions and the physical parameter function input, and perform numerical simulation according to the target flue gas guide vane and the condensation model to determine the degree of optimization of the heat transfer efficiency of the condensing secondary heat exchanger by the target flue gas guide vane.

[0065] S105: Taking the maximum degree of optimization of the heat exchange efficiency of the condensing secondary heat exchanger by the target flue gas guide vane as the optimization target, optimizing the design parameters of the target flue gas guide vane, and determining the optimal design parameters of the flue gas guide vane through multiple rounds of iterative numerical simulation.

[0066] After that, the server can build a condensation model based on the determined geometric model, boundary conditions and physical property conditions to perform numerical simulation.

[0067] Specifically, most of the flue gas is composed of non-condensable gases, while water vapor only accounts for 10-30%. Studies have shown that 1% of the mass content of air in water vapor can reduce the surface heat transfer coefficient by 60%. Compared with the thermal resistance of non-condensable gases, the thermal resistance brought by the condensation liquid film is very small and can be ignored. Therefore, a single-phase multi-component heat and mass transfer model is used to study the condensation heat transfer process in the secondary heat exchanger.

[0068] The solution of flue gas condensation, diffusion and mass transfer process is based on the diffusion boundary layer condensation model. Therefore, the condensation rate of water vapor on the tube wall can be expressed as:

[0069]

[0070] Where ρ is the smoke density / kg·m -3 , D is the mass diffusion coefficient, ω is the water vapor mass fraction, and n is the normal direction of the vertical wall. b is the suction factor in turbulent state, θ b =ln(1+B) / B, B=(W s,i -W s,∞ ) / (1-W s,i ), the subscripts i and ∞ represent the interface and mainstream, respectively.

[0071] The condensation process on the outer wall of the tube can be represented by the source term added to the grid adjacent to the wall. The source term in the unit grid can be calculated by the formula:

[0072]

[0073] In the formula, A face is the effective condensation area near the grid wall, V cell is the grid volume.

[0074] The momentum source term, latent heat source term, turbulent energy term, turbulent dissipation rate source term, and component source term on the flue gas side are respectively shown as follows:

[0075]

[0076] Where U j is the velocity of the smoke in the j direction, h fgis the latent heat of water vapor, k is the turbulent kinetic energy, and ε is the turbulent dissipation rate.

[0077] The schematic diagram of the location of adding each source item is as follows Figure 6 As shown, Figure 6 This is a schematic diagram of a condensation process in the present invention. The entire simulation process is self-programmed by adding source items in the calculation area through a user-defined function (UDF). For example, the flue gas condenses at the wall surface and turns into condensed water, and the flue gas mass decreases. A negative mass source item can be added to the first layer of the grid in the flue gas calculation domain to represent the flue gas reduction process. For the latent heat released by condensation, a positive energy source item can be added to the pipe wall calculation domain to represent the heat absorption process. Other source items are similar.

[0078] In order to verify the correctness of the condensation model and parameter settings adopted in the present invention, the numerical simulation results were compared with the experimental results in the literature, and the numerical model used the same model parameters as the experiment. Figure 7 This is a comparison diagram of Nu obtained by numerical calculation and experiment in the present invention. The maximum error between the two is less than 15%, which is within a reasonable error range, proving that the numerical model in the present invention is feasible.

[0079] Figure 8 is a schematic diagram of a temperature cloud diagram in the present invention, Figure 8 It can be seen that the flue gas inlet velocity is 10m·s -1 The temperature distribution cloud diagram of the steady-state flow in the condensing secondary heat exchanger. Figure 8 It can be seen that there is an obvious low-temperature area in the temperature cloud map without smoke guide structure, and its temperature is significantly lower than the smoke temperature and close to the cooling water temperature, which indicates that the convective heat transfer intensity in this area is weak. In the temperature cloud map with arc-shaped and wavy guide structures, the above low-temperature area obviously disappears, and the smoke flows through this area and is cooled by the cold water in the heat absorption tube, forming a temperature gradient with gradually decreasing temperature along the smoke flow direction. This shows that the heat exchange process occurs in this area, and the heat exchange intensity is significantly increased compared with the structure without smoke guide.

[0080] Fig. 9 A schematic diagram of a flue gas velocity cloud diagram in the present invention is shown in FIG. Fig. 9 It can be seen that the flue gas inlet velocity is 10m·s -1, steady-state flow velocity distribution cloud diagram of the condensing secondary heat exchanger. As can be seen from the figure, there is a large area of ​​flow dead zone in the velocity cloud diagram without smoke guide structure, and the flow dead zone hinders the flow of incoming smoke, and the flow cross-sectional area is only about 1 / 3 of the theoretical flow cross-sectional area. In the velocity cloud diagram with arc-shaped guide structure, the turning angle of incoming smoke becomes smaller, more smoke flows into the flow dead zone, the vortex near the heat absorption tube bundle is eliminated, and the flow dead zone is significantly improved. Therefore, the flow dead zone does not hinder the incoming smoke, the flow cross-sectional area of ​​the smoke in the upper part of the condensing secondary heat exchanger becomes larger, and it flows evenly through the upper part of the tube bundle. In the velocity cloud diagram with wavy guide structure, the turning angle of the incoming smoke also becomes smaller, and the flow dead zone is improved. The wavy lower end structure has the function of flow redistribution, so that more smoke flows into the arc structure and finally into the flow dead zone. As can be seen from the figure, the flow increases under the diversion effect, and the flue gas flow velocity near the tube bundle in the original flow dead zone increases significantly. On the right side of the wavy guide structure, the flue gas flow velocity increases due to the sudden decrease in the flow cross-sectional area. At the same time, the smoke flows along the outer shell, eliminating the original flow dead zone.

[0081] When applying the design method of the smoke guide plate provided by the present invention, it is not necessary to Figure 3 The steps are executed in the order shown. The specific execution order of the steps can be determined according to needs, and the present invention does not limit this.

[0082] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0083] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present invention.

Claims

1. A condensing secondary heat exchanger, characterized in that: include: A shell, a plurality of heat absorbing tubes, an intermediate guide plate and a smoke guide vane; The shell is provided with a smoke inlet and a smoke outlet, and a plurality of heat absorbing tubes are provided in the shell; The intermediate guide plate is arranged between the smoke inlet and the smoke outlet, and the plurality of heat absorbing tubes are separated into upper and lower parts by the intermediate guide plate, and the interior of the shell is divided into an upper chamber connected to the smoke outlet and a lower chamber connected to the smoke inlet, and there is a gap between the intermediate guide plate and the opposite shell wall, so as to form a passage from the smoke inlet to the smoke outlet; The smoke guide plate is fixed between the middle guide plate and the opposite shell wall, is clamped by the two side walls of the shell, and is arranged across the upper chamber and the lower chamber. It is used to guide part of the smoke into the lower heat absorption pipe area of ​​the upper chamber when the smoke turns from the lower chamber to flow to the upper chamber, so that it flows through the lower heat absorption pipe area and is discharged from the smoke outlet.

2. The condensing secondary heat exchanger according to claim 1, characterized in that: The smoke guide plate is an arc-shaped guide structure, with two arc ends respectively located in the upper chamber and the lower chamber, with the concave side facing the middle guide plate and the convex side facing the shell wall on the opposite side of the middle guide plate.

3. The condensing secondary heat exchanger according to claim 2, characterized in that: The smoke guide plate also includes two fins, which are respectively fixedly connected to the arc end in the upper chamber and the arc end in the lower chamber. The other ends of the two fins are arranged near the shell wall to form a wave-shaped guide structure.

4. A method for designing a flue gas guide vane in a condensing secondary heat exchanger according to any one of claims 1 to 3, characterized in that: include: According to the physical object of the condensing secondary heat exchanger, a geometric model of the condensing secondary heat exchanger is constructed; Determine the flue gas inlet velocity, flue gas inlet temperature, total cold water inlet flow rate of each heat absorption tube in the condensing secondary heat exchanger, cold water inlet temperature and numerical simulation boundary conditions of flue gas circulation; According to the changes in the thermal physical properties of the flue gas caused by the temperatures at the inlet and outlet sides of the flue gas, the physical properties of the flue gas are fitted as a physical property parameter function input that changes with temperature; A condensation model is constructed according to the geometric model of the condensing secondary heat exchanger, the numerical simulation boundary conditions and the physical parameter function input, and a numerical simulation is performed according to the target flue gas guide vane and the condensation model to determine the degree of optimization of the heat exchange efficiency of the condensing secondary heat exchanger by the target flue gas guide vane; Taking the maximum optimization degree of the heat exchange efficiency of the condensing secondary heat exchanger by the target flue gas guide vane as the optimization goal, the design parameters of the target flue gas guide vane are optimized, and the optimal design parameters of the flue gas guide vane are determined through multiple rounds of iterative numerical simulation.

5. The method according to claim 4, characterized in that The numerical simulation boundary conditions for determining the flue gas inlet velocity, the flue gas inlet temperature, the total cold water inlet flow rate of each heat absorption tube in the condensing secondary heat exchanger, the cold water inlet temperature and the flue gas circulation specifically include: Determine that the flue gas inlet of the secondary condensing heat exchanger is a constant temperature velocity inlet, the cold water inlet of each heat absorption tube in the secondary condensing heat exchanger is a mass flow inlet, the flue gas outlet and the cold water outlet are pressure outlets, the inner and outer walls of each heat absorption tube are applied with coupled boundary conditions, and the shell wall of the secondary condensing heat exchanger is applied with adiabatic boundary conditions; For each process of cold water from the cold water inlet to the cold water outlet, the average temperature and average flow rate of the process outlet are taken as the inlet boundary conditions of the next process; Among them, the flue gas inlet velocity is 8-12m·s -1 The flue gas inlet temperature is 393.15K, and the total flow rate of cold water inlet is 10-20kg·min -1 The cold water inlet temperature is 293K.

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