Gasifier based on spiral turbulent flow enhanced heat exchange and condensed water integrated recovery

Abstract

The invention provides a vaporizer based on spiral turbulent flow enhanced heat exchange and condensed water integrated recovery. The vaporizer comprises a heat exchange pipe, spiral turbulent flow pieces are arranged on the inlet section of the heat exchange pipe to form a turbulent flow induction area, a condensed water disc is arranged at the bottom of the heat exchange pipe, and a water outlet of the condensed water disc is connected with a water storage container; and the heat exchange tube and the condensate water disc are arranged in the shell. Through the collaborative design of the spiral spoiler, the integrated condensate water disc and the optimized shell, the three core problems that in the prior art, the laminar flow heat exchange efficiency is low, condensate water energy is wasted, and the cold island effect is caused are systematically solved, and the gasifier is suitable for phase-change heat exchange equipment such as an LNG gasifier and an industrial steam gasifier.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchange equipment, and more specifically, to a vaporizer based on spiral flow disturbance for enhanced heat transfer and integrated condensate recovery. Background Art

[0002] In the context of global energy transformation and low-carbon development, the air-cooled vaporizer, as an environmentally friendly heat exchange device without external energy, shows broad application prospects in liquefied natural gas (LNG) receiving stations, distributed energy systems, and civil gas fields. Its core principle is to achieve the phase change process through the natural convection of ambient air and low-temperature fluid, and the theoretical thermal efficiency can reach more than 85%. However, in practical engineering applications, there are generally four major technical bottlenecks, which seriously restrict the energy efficiency and reliability improvement.

[0003] From a thermodynamic perspective, the single-phase flow mode of traditional heat exchange tube vaporizers causes the fluid to form a stable laminar boundary layer in the low heat flux density region (such as the sudden change of pipe diameter). According to the Dittus-Boelter criterion, when the Reynolds number Re < 2300, the Nusselt number in the laminar state is only 30% - 45% of that in the turbulent state, and the corresponding heat transfer coefficient difference reaches 2 - 3 times. This inefficient heat transfer characteristic is particularly significant under low-temperature conditions. Measured data shows that when the LNG flow rate is lower than 300 kg / h, the vaporization efficiency is less than 60% of the theoretical value. At the same time, the existing spiral flow disturbance fin designs mostly rely on empirical parameters, lacking the quantitative relationship between the spiral angle (α) and the Nusselt number (Nu); the condensate management is not coupled with the turbulent flow enhancement, resulting in a latent heat recovery efficiency of less than 30%.

[0004] The defect of condensate management and the cold island effect form a vicious cycle. The unrecovered condensate not only causes latent heat loss (theoretical calculation shows that each kilogram of condensate carries about 2258 kJ of vaporization latent heat), but the local low-temperature area generated during its dripping process will accelerate the corrosion rate of the metal pipe wall. The operation and maintenance data of an LNG receiving station shows that the average annual corrosion depth of the vaporizer without waterproof measures reaches 0.8 mm, and the equipment life is shortened by 40%. The environmental temperature drop caused by the cold island effect further deteriorates the heat transfer performance. The CFD simulation based on the finite volume method shows that when the vaporization amount reaches 1000 kg / h, the temperature drop within 5 m around the equipment can reach 8 - 12 °C, corresponding to an increase in air density, resulting in a decrease in the natural convection driving force of about 35%. More dangerously, in coastal areas with high humidity, frost layers are likely to form on the low-temperature surface, and its thermal resistance can reach 0.1 - 0.3 m 2 ·K / W, reducing the effective heat transfer coefficient by more than 50%. In addition, the support design of traditional vaporizers mostly relies on empirical formulas, without quantifying the matching relationship between the equipment weight and the support parameters. The data of an LNG receiving station shows that the structural deformation caused by insufficient support thickness accounts for 12% of the equipment failures, while over-design increases the material cost by 15% - 20%. There is an urgent need for a support optimization method based on a mechanical model.

[0005] Prior art attempts to improve performance through structural modifications, but all have fundamental flaws. Although the design of the spiral heat exchange tube extends the heat transfer path (the measured tube length increases by 30%-50%), it does not change the nature of single-phase flow, and the laminar flow proportion still accounts for more than 60%. In the external condensate pan solution, since it is not thermally integrated with the vaporizer body, the collected condensate needs to be evaporated again, which instead increases the system energy consumption. Although the forced air supply device can increase the heat transfer coefficient by 20%-30%, the power supply it relies on is contrary to the "zero energy consumption" design concept of the air-temperature vaporizer, and its applicability is limited in remote areas or emergency scenarios.

[0006] In summary, the prior art has not systematically solved the three core contradictions of low-efficiency heat transfer dominated by laminar flow, waste of condensate energy, and performance decay caused by the cold island effect. Therefore, it is urgent to construct a multi-physical field coupling enhanced heat transfer mechanism to achieve a double breakthrough in gasification efficiency and operation reliability through active flow control, latent heat recovery, and boundary condition optimization. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention provides a vaporizer based on spiral flow disturbance enhanced heat transfer and integrated condensate recovery. Through the collaborative design of spiral flow disturbance fins, an integrated condensate pan, and an optimized shell, the present invention systematically solves the three core problems of low laminar heat exchange efficiency, waste of condensate energy, and cold island effect in the prior art. This vaporizer is applicable to phase change heat transfer equipment such as LNG vaporizers and industrial steam vaporizers.

[0008] To achieve the above object, the present invention provides the following technical solution: A vaporizer based on spiral flow disturbance enhanced heat transfer and integrated condensate recovery, including a heat exchange tube. A spiral flow disturbance fin is arranged at the inlet section of the heat exchange tube to form a turbulent flow induction area, and a condensate pan is arranged at the bottom of the heat exchange tube. The drain outlet of the condensate pan is connected to a water storage container; the heat exchange tube and the condensate pan are arranged in a shell.

[0009] Furthermore, the spiral angle of the spiral flow disturbance fin is designed according to the enhanced heat transfer requirements of the heat exchange tube, and is specifically determined by the following formula:

[0010] Nu = 0.023·Re 0.8 ·Pr 0.4 (1 + Aα B )

[0011] In the formula: Nu is the Nusselt number of the heat exchange tube after adding the spiral flow disturbance fin, representing the convective heat transfer intensity; Re is the Reynolds number, where ρ is the fluid density, u is the flow velocity, d is the pipe diameter, and μ is the dynamic viscosity; Pr is the Prandtl number, where C Pis the specific heat capacity, λ is the thermal conductivity; α is the helix angle of the helical turbulator; A and B are the influence coefficients of the helix angle of the helical turbulator on the heat transfer coefficient;

[0012] It is required that the Nusselt number Nu of the heat exchange tube after adding the helical turbulator is greater than the Nusselt number Nu of the smooth heat exchange tube smoorh ;

[0013] The Nusselt number Nu of the smooth heat exchange tube smooth is calculated as follows:

[0014] Nu smooth = 0.023·Re 0.8 ·Pr 0.4

[0015] In the formula: Nu smooth is the Nusselt number of the smooth heat exchange tube, Re is the Reynolds number, and Pr is the Prandtl number.

[0016] Furthermore, the helical turbulator is made of a stainless steel helical turbulator, the helix angle of the stainless steel helical turbulator is 10° to 50°, the thickness is 0.1 mm to 2.5 mm, and the pitch-diameter ratio of the stainless steel helical turbulator to the heat exchange tube is 2.5 / 1 to 10 / 1.

[0017] Furthermore, the helical turbulator is fixed to the inner wall of the heat exchange tube by laser welding or mechanical expansion joint, and a fixing hole is provided in the middle of its upper end.

[0018] Furthermore, the bottom of the condensate pan is provided with a slope towards the drain outlet, and the slope of the condensate pan is determined by the drainage efficiency, specifically as follows:

[0019] The relationship between the slope of the condensate pan and the drainage efficiency satisfies:

[0020] Q 有效 = Q water ×(1 - e -k·i )

[0021] In the formula: Q 有效 is the actual amount of cold water discharged; k is the empirical coefficient; i is the slope; Q water is the condensate recovery amount;

[0022] Q water = K·A·ΔT·t·η

[0023] In the formula: A is the effective condensation surface area; K is the heat transfer coefficient; ΔT is the temperature difference; t is the operating time, in hours, based on the single-shift operating time; η is the recovery efficiency;

[0024] Q 滞留 = Q water - Q 有效

[0025] Where: Q 滞留 is the condensate retention amount, and the condensate retention amount ≤ 5%;

[0026] Determine the diameter of the drain port 31 according to the condensate pan slope and the condensate drainage time, specifically as follows:

[0027]

[0028] Where: V water is the condensate volume, V water = Q water / ρ; D valve is the drain valve diameter; g is the acceleration due to gravity; i is the bottom slope of the condensate pan; L slope is the length of the drainage slope;

[0029] It is required that the drain port diameter D valve satisfies the following conditions:

[0030]

[0031] Where: Q max is the maximum condensate flow rate; v crit is the critical flow velocity.

[0032] Furthermore, the bottom slope i of the condensate pan towards the drain port = 0.01.

[0033] Furthermore, the condensate pan is detachably arranged at the bottom of the housing, and the covering area of the condensate pan is larger than the projected area of the bottom of the heat exchange tube.

[0034] Furthermore, there are supports in the housing. The support includes four support legs and a base plate arranged at the bottom of each support leg. Among them, every two support legs are connected by a cross beam with a slope and a groove, and the cross beam can slide up and down along the two support legs through a guide rail slider lock;

[0035] The condensate pan is detachably arranged on two cross beams of the four support legs. The slopes of the two cross beams are the same, and wing turn locks are arranged on the support legs of the two supports to fix the condensate pan.

[0036] Furthermore, the thickness of the support legs of the support in the housing is designed according to the total weight of the equipment and the material strength, specifically as follows:

[0037]

[0038] Where: W total is the total weight of the equipment, including the heat exchange tube, the condensate pan and the housing; L span is the span of the two supports; σ allowσ is the allowable stress of the material; b is the width of the support; the safety factor ≥ 1.5, and the actual thickness is 1.2 - 1.5 times the calculated value.

[0039] Furthermore, the overall energy efficiency of the vaporizer is improved by setting the spiral turbulator, the condensate pan and the outer shell, specifically including the contribution rate of turbulence enhancement brought by setting the spiral turbulator, the contribution rate of condensate recovery brought by setting the condensate pan, and the flow path wind resistance loss between the outer shell and the heat exchange tube brought by setting the outer shell, where each item is denoted as: η turb is the contribution rate of turbulence enhancement; η cond is the contribution rate of condensate recovery; Δη inter is the flow path wind resistance loss;

[0040] Among them, the contribution rate of turbulence enhancement is calculated as follows:

[0041]

[0042] In the formula: η turb is the contribution rate of turbulence enhancement, Nu is the Nusselt number of the heat exchange tube after adding the spiral turbulator; Nu smooth is the Nusselt number of the smooth heat exchange tube;

[0043] The Nusselt number Nu of the heat exchange tube after adding the spiral turbulator is calculated as follows:

[0044] Nu = 0.023·Re 0.8 ·Pr 0.4 (1 + 1.5sin 1.2 α)

[0045] The Nusselt number Nu of the smooth heat exchange tube smooth is calculated as follows:

[0046] Nu smooth = 0.023·Re 0.8 ·Pr 0.4

[0047] In the formula: Re is the Reynolds number, where ρ is the fluid density, u is the flow velocity, d is the pipe diameter, and μ is the dynamic viscosity; Pr is the Prandtl number, where C P is the specific heat capacity, λ is the thermal conductivity; α is the spiral angle of the spiral turbulator;

[0048] Among them, the contribution rate of condensate recovery is calculated as follows:

[0049]

[0050] In the formula: η cond is the contribution rate of condensate recovery; m is the mass of condensate, which is calculated from the condensate recovery amount Q water Calculated; Lv is the latent heat of vaporization of water; E total is the total energy consumption of the system;

[0051] Q water = K·A·ΔT·t·η

[0052] In the formula: A is the effective condensation surface area; K is the heat transfer coefficient; ΔT is the temperature difference; t is the operation time, based on the single-shift operation time; η is the recovery efficiency;

[0053] Among them, the calculation formula for the wind resistance loss of the flow channel between the shell and the tube is:

[0054]

[0055] In the formula: △η inter is the energy efficiency loss caused by the wind resistance of the flow channel between the shell and the tube; △P inter is the additional pressure drop of the flow channel between the shells; ρ is the air density; u is the natural convection wind speed.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] The present invention provides a vaporizer based on spiral flow disturbance enhanced heat transfer and condensate integrated recovery. By arranging spiral flow disturbance fins inside the heat exchange tube, the laminar flow state easily formed inside the traditional heat exchange tube vaporizer can be broken, the fluid is forced to generate turbulence, the gas-liquid contact time is prolonged, and the heat transfer coefficient is significantly improved;

[0058] Preferably, the spiral flow disturbance fins are stainless steel spiral flow disturbance fins with a spiral angle of 10° to 50° and a thickness of 0.1 mm to 2.5 mm, and the pitch-to-diameter ratio is 2.5 / 1 to 10 / 1. These parameters perform excellently in balancing the flow resistance and heat transfer efficiency, resulting in only an 18% increase in the pressure drop while the heat transfer coefficient is greatly improved. Further, through the formula (Nu = 0.023·Re 0.8 ·Pr 0.4 (1 + Aα B )) the flow disturbance parameters are precisely designed, avoiding the empirical trial and error in the traditional design, resulting in a 42.6% increase in the Nusselt number (Nu) (compared with the calculated value of the smooth tube Dittus-Boelter formula), and the Reynolds number (Re) also jumps from the laminar flow region (Re < 2300) to the turbulent flow region (Re > 4000), and the measured heat transfer coefficient is increased by 2 to 3 times. Due to the enhancement of the turbulence inside the tube, the heat transfer efficiency inside the vaporizer is significantly improved, which not only speeds up the vaporization process but also improves the heat transfer performance of the overall equipment.

[0059] The present invention provides a vaporizer based on spiral flow disturbance for enhanced heat transfer and integrated condensate recovery. An integrated condensate pan is provided at the bottom of the heat exchange tube to effectively collect and process the condensate generated during the gasification process. This avoids the consumption of latent heat of vaporization due to secondary evaporation of the condensate, reduces the humidity around the equipment, increases the air density by 1.5%, and correspondingly increases the Reynolds number Re by 9.2%, thereby increasing the convective heat transfer coefficient by 12% - 15%. At the same time, it avoids the sudden change in thermal resistance caused by condensation on the tube wall, maintains the heat transfer stability, improves the heat transfer efficiency of the vaporizer, and inhibits the electrochemical corrosion of the metal surface;

[0060] The inclined slope of the condensate pan (i = 0.01) combined with a large-diameter drain valve (DN20) enables the residence time of the condensate to be less than 15 minutes, and the condensate recovery rate reaches over 95% (compared with the retention amount of 15% - 20% in the traditional design without slope). The recovered condensate can be reused, avoiding the consumption of latent heat of vaporization due to secondary evaporation of the condensate, thereby reducing the total energy consumption. The latent heat recovery contributes to a 16.4% reduction in the total energy consumption. The condensate pan adopts a detachable design, such as a slide rail groove guide + manual locking mechanism, etc., making the cleaning and maintenance work more convenient and efficient. The cleaning efficiency is increased by 50%, reducing the maintenance cost.

[0061] The present invention provides a vaporizer based on spiral flow disturbance for enhanced heat transfer and integrated condensate recovery. By providing a vaporizer housing, it effectively isolates the internal equipment from the external environment erosion, extending the service life of the equipment. At the same time, the housing has functions such as dust-proof, waterproof, and anti-collision, and the openings and gaps are all sealed, improving the protection performance and safety of the vaporizer.

[0062] Preferably, the shell-side flow channel is optimized for wind resistance design, and the energy efficiency loss caused by the additional pressure drop is controlled within 2.3%. This not only improves the heat transfer efficiency but also inhibits the cold island effect (the peripheral temperature drop is reduced from 8 - 12°C to 3 - 5°C), enabling the vaporizer to maintain good performance under different environmental conditions. The housing design is verified by finite element analysis, and the maximum deformation is less than 0.1 mm, meeting the rigidity requirements of industrial equipment. This ensures that the vaporizer can still maintain a stable form under harsh working conditions, preventing equipment damage caused by vibration or external impact, and improving the reliability of the overall system.

[0063] Preferably, the present invention realizes the quantitative design of the equipment weight through the thickness of the support, achieving the balance between structural safety and light weight.

[0064] In summary, through the collaborative design of the spiral turbulator, the integrated condensate pan, and the optimized housing, the present invention systematically solves the three core problems in the prior art: low laminar heat transfer efficiency, waste of condensate energy, and cold island effect. The improvement of heat transfer efficiency reduces energy consumption, the recovery of condensate reduces water resource waste, and the detachable design reduces maintenance costs, resulting in significant overall economic benefits. By optimizing the housing design and condensate recovery measures, the present invention also embodies the concept of environmental friendliness, contributing to promoting green manufacturing and sustainable development. Description of the Drawings

[0065] Figure 1 Schematic diagram of the overall structure of the vaporizer;

[0066] Figure 2 Detail drawing of the fixed structure of the spiral turbulator;

[0067] Figure 3 Schematic diagram of the size and spiral angle of the spiral turbulator;

[0068] Figure 4 Structural diagram of the condensate pan and drainage system;

[0069] Figure 5 Schematic diagram of the fixed state of the condensate pan;

[0070] Figure 6 Schematic diagram of the disassembled state of the condensate pan;

[0071] Figure 7 Schematic diagram of the structure of the vaporizer housing;

[0072] Figure 8 Curve of the wind resistance coefficient of the flow channel between the shell and the tube varying with the length-diameter ratio;

[0073] Figure 9 Curve of the drainage time-valve diameter relationship based on theoretical calculation (gradient i = 0.01).

[0074] In the drawings: 1, heat exchange tube; 2, spiral turbulator; 3, condensate pan; 4, housing; 5, wing rotating lock; 21, fixing hole; 31, water outlet; 32, sewage valve; 33, water pan handle; 41 support leg; 42 base plate. Detailed Embodiments

[0075] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0076] The present invention provides a vaporizer based on spiral flow disturbance for enhanced heat transfer and integrated condensate recovery. The core lies in optimizing the internal structure of the vaporizer to enhance the heat transfer efficiency and integrating a condensate treatment system to improve the overall energy efficiency. First, the basic dimensions and the layout of the heat exchange tubes of the vaporizer are determined. Subsequently, stainless steel spiral flow disturbance fins are designed and installed inside the heat exchange tubes to break the laminar flow state that is easily formed by the fluid inside the traditional heat exchange tube type vaporizer, forcing the fluid to generate turbulence and enhancing the heat transfer effect. At the same time, an integrated condensate pan is designed at the bottom of the heat exchange tubes to collect and treat the condensate generated during the vaporization process, avoiding energy waste and equipment corrosion. Finally, the outer shell of the vaporizer is optimized in design to improve its protection performance and durability. In summary, the structure of the composite vaporizer of the present invention includes:

[0077] Components such as heat exchange tubes 1, spiral flow disturbance fins 2, condensate pans 3, and outer shells 4, where:

[0078] The heat exchange tube 1 is the core component of the vaporizer. The heat exchange tube 1 is used to carry the liquid medium to be vaporized. The heat exchange tube 1 adopts standard dimensions and materials to ensure that it can withstand the working pressure and maintain long-term stable operation.

[0079] The spiral flow disturbance fin 2 is made of 304 stainless steel and is of the same length as the heat exchange tube 1. The spiral angle is controlled between 10° and 50°, and the thickness range is between 0.1 mm and 2.5 mm ( Figure 3 ); The spiral flow disturbance fin 2 is fixed to the inner wall of the heat exchange tube 1 by laser welding or mechanical expansion joint. A fixing hole 21 is provided in the middle of its upper end for easy fixation. The spiral flow disturbance fin 2 can break the laminar flow state that is easily formed by the fluid inside the traditional heat exchange tube type vaporizer, forcing the fluid to generate turbulence, prolonging the gas-liquid contact time, and significantly increasing the heat transfer coefficient;

[0080] Specifically, in the first row of heat exchange tubes of the vaporizer heat exchange tubes ( Figure 1 ) internally installed spiral flow disturbance fins of 304 stainless steel of the same length, and a fixing hole 21 ( Figure 2 ) is provided in the middle of the upper end of the spiral flow disturbance fin; When the pitch-to-diameter ratio of the stainless steel spiral flow disturbance fin is 2.5 / 1 to 10 / 1, the fluid Reynolds number can be increased from the laminar flow region (Re < 2300) to the turbulent flow region (Re > 4000). Furthermore, the laminar boundary layer can be destroyed by the spiral flow disturbance fin 2, inducing the fluid to generate turbulence (Re > 4000) and secondary eddies, enhancing the fluid mixing in the near-wall region, and increasing the heat transfer coefficient by 25% - 35% compared with the smooth tube (see Example 1).

[0081] Preferably, the 304 stainless steel spiral flow disturbance fin takes into account both corrosion resistance and mechanical strength. Its 1.0 mm thickness can withstand a working pressure of 4.0 MPa (safety factor 1.5).

[0082] The vertical distance between the upper edge of the condensate pan 3 and the bottom horizontal heat exchange tube 1 is 10 mm. It is made of 316L stainless steel with a thickness of 2 mm to ensure sufficient strength and corrosion resistance. The bottom of the condensate pan 3 is designed with an inclined slope to facilitate the smooth discharge of condensate. The coverage area of the condensate pan 3 is larger than the projected area of the heat exchange tube 1 to prevent condensate from splashing. The drain port 31 of the condensate pan 3 is equipped with a flanged sewage valve 32 and a quick connector, which is convenient for connecting the water pipe to the water storage container. In addition, a backwash ball valve is also provided at the bottom for sewage discharge when cleaning the equipment.

[0083] Preferably, the condensate pan 3 is made of a 316L stainless steel pan body (with a thickness of 2 mm), the bottom inclined slope i = 0.01 (corresponding to an angle of 0.57°), the coverage area of the pan body ≥ 120% of the projected area of the heat exchange tube 1 (redundant design to prevent splashing), the drain port 31 corresponding to the lowest point of the condensate pan 3 uses a DN20 flanged drain valve; a DN15 backwash ball valve (with a pressure resistance of 1.6 MPa) is set at the lowest point of the bottom of the condensate pan 3 for sewage discharge when cleaning the equipment, and a silicone rubber bellows is used to connect between the drain port 31 and the water storage container ( Figure 4 ).

[0084] A water pan handle 33 is provided on the condensate pan 3. The condensate pan 3 can be removed from the housing 4 by using the water pan handle 33. Specifically, there is a support in the housing 4. The support includes four support legs 41 and a base plate 42 provided at the bottom of each support leg 41. Every two support legs 41 are connected by a cross beam with a slope and a groove. The cross beam can slide up and down along the two support legs 41 through a guide rail slider and be locked to the required height ( Figure 5 ), and the condensate pan 3 is detachably arranged on the two cross beams of the support, and the slopes are all the same, i = 0.01.

[0085] Two front support legs 41 are provided with wing rotation locks 5 for fixing the condensate pan 3; when the condensate pan 3 needs to be removed, twist the wing rotation lock 5 on the support leg 41 perpendicular to the ground ( Figure 5 ), when the condensate pan 3 needs to be fixed, twist the wing rotation lock 5 parallel to the ground ( Figure 6 ).

[0086] The thickness (t support ) of the support leg 41 of the housing 4 needs to be quantitatively designed according to the total weight (W total ) of the equipment and the material strength, and satisfies the following formula:

[0087]

[0088] In the formula: W total is the total weight of the equipment (kg), including the self - weight of the heat exchange tube, the condensate pan and the housing; L span is the support span (m), that is, the distance between the two supports (take 1.2 m); σallow σ is the allowable stress of the material (MPa), taking 120 MPa for stainless steel (316L) and 160 MPa for carbon steel; b is the width of the support (m), with a default value of 0.1 m. Design criterion: safety factor ≥ 1.5, and the actual thickness needs to be 1.2 - 1.5 times the calculated value;

[0089] The present invention collects and exports the condensed water, avoids the consumption of latent heat of vaporization due to secondary evaporation, reduces the humidity around the equipment, can increase the air density by 1.5% (compared with the condition of RH = 80%), the Reynolds number Re increases by 9.2% accordingly, and then increases the convective heat transfer coefficient by 12% - 15%. At the same time, it avoids the sudden change of thermal resistance caused by dew condensation on the pipe wall, maintains the heat transfer stability, so as to improve the heat transfer efficiency of the vaporizer and inhibit the electrochemical corrosion of the metal surface.

[0090] The outer shell 4 is made of high-strength and corrosion-resistant materials ( Figure 7 ), and has functions such as dust-proof, waterproof, and anti-collision. The following materials can be specifically selected:

[0091] 1. Aluminum alloy (such as 6061 - T6): light weight, excellent corrosion resistance, high thermal conductivity, suitable for medium and small-sized vaporizers.

[0092] 2. Stainless steel (such as 316L): extremely excellent corrosion resistance, high strength, suitable for large-sized vaporizers or extreme environments.

[0093] 3. Composite material (such as fiberglass): light weight, excellent corrosion resistance, suitable for occasions with high requirements for weight and corrosion resistance.

[0094] 4. Carbon steel + surface treatment (such as galvanizing or spraying): low cost, high strength, improve the corrosion resistance through surface treatment, suitable for occasions with limited budget.

[0095] The design of the outer shell 4 fully considers the working environment of the vaporizer, and the openings and gaps are carefully designed and sealed to prevent leakage and accidents. Reinforcing ribs are added to the inner wall or outer wall of the outer shell 4 to improve the overall stiffness and anti-deformation ability.

[0096] The outer shell 4 is designed as a detachable modular structure, which is convenient for transportation, installation and maintenance. The optimized design of the outer shell 4 not only improves the protection performance of the vaporizer, but also enhances its safety and stability.

[0097] An enhanced heat transfer structure of a vaporizer based on spiral turbulators and a detachable condensate pan provided by the present invention. Based on the improvement of the structure of the present invention, the overall energy efficiency improvement results from the synergistic effect of spiral turbulator enhancement, condensate recovery, and shell-side flow channel optimization, as follows: Through the design of the spiral turbulator 2, the laminar flow state that is easily formed inside the traditional heat exchange tube type vaporizer is successfully broken, and the fluid is forced to generate turbulent flow, thereby significantly improving the heat transfer coefficient. Specifically: The spiral turbulator 2 is designed at an angle of 40° to 50°, converting laminar flow (Re < 2300) into turbulent flow (Re > 4000). The measured heat transfer coefficient is increased by more than 40%, and the contribution rate of turbulent flow enhancement is 28.5%; at the same time, the integrated design of the condensate pan 3 effectively avoids the waste of condensate and equipment corrosion problems, improving the overall energy efficiency. Specifically: The condensate pan 3 has a 1% slope and a 95% recovery rate with a DN20 drain valve, and the contribution rate of condensate recovery is 16.4%, reducing the latent heat loss; the shell-side flow channel between the outer shell 4 and the heat exchange tube 1 is optimized for wind resistance, and the wind resistance loss of the flow channel is only 2.3%, improving the protection performance and safety of the vaporizer.

[0098] 1) After adding the spiral turbulator 2, the heat exchange tube 1 generates turbulent flow, and the calculation of the contribution rate of turbulent flow enhancement is as follows:

[0099] Forced convection heat transfer in the smooth heat exchange tube inside the traditional vaporizer is applicable to the Dittus - Boelter classical empirical formula, and its form is:

[0100] Nu smooth = 0.023·Re 0.8 ·Pr 0.4

[0101] In the formula:

[0102] Nu smooth is the Nusselt number of the smooth heat exchange tube, dimensionless, representing the intensity of convective heat transfer;

[0103] Re is the Reynolds number, dimensionless, where ρ is the fluid density (kg / m 3 ), u is the flow velocity (m / s), d is the pipe diameter (m), and μ is the dynamic viscosity (Pa·s);

[0104] Pr is the Prandtl number, dimensionless, where C P is the specific heat capacity (J / (kg·K)), and λ is the thermal conductivity (W / (m·K)). The heat transfer efficiency of the heat exchange tube 1 with the spiral turbulator added satisfies:

[0105] Nu = 0.023·Re 0.8 ·Pr 0.4 (1 + Aα B )

[0106] In the formula:

[0107] Nu is the Nusselt number of the heat exchange tube after adding the spiral turbulator, dimensionless, representing the convective heat transfer intensity;

[0108] Re is the Reynolds number, dimensionless, where ρ is the fluid density (kg / m 3 ), u is the flow velocity (m / s), d is the pipe diameter (m), and μ is the dynamic viscosity (Pa·s);

[0109] Pr is the Prandtl number, dimensionless, where C P is the specific heat capacity (J / (kg·K)), and λ is the thermal conductivity (W / (m·K));

[0110] α is the spiral angle (°) of the spiral turbulator, and the preferred range is 10° to 50°. Beyond this range, it will cause a sharp increase in pressure drop or a decrease in heat transfer effect;

[0111] A and B are the influence coefficients of the spiral angle of the spiral turbulator on the heat transfer coefficient.

[0112] After calculation, the Nusselt number Nu of the heat exchange tube 1 after adding the spiral turbulator 2 is increased by 25% - 35% compared with the traditional structure.

[0113] Calculation formula for the contribution rate of turbulent enhancement after adding the spiral turbulator:

[0114]

[0115] In the formula:

[0116] Nu is the Nusselt number of the heat exchange tube after adding the spiral turbulator, dimensionless, representing the convective heat transfer intensity;

[0117] Nu smooth is the Nusselt number of the smooth heat exchange tube, dimensionless, representing the convective heat transfer intensity;

[0118] η turb is the contribution rate of turbulent enhancement (%).

[0119] 2) The calculation of the contribution rate of condensate recovery is as follows:

[0120] The condensate recovery amount is calculated using the following formula:

[0121] Q water = K·A·ΔT·t·η

[0122] In the formula: Q water is the condensate recovery amount, with the unit of kg, based on the typical heat transfer coefficient range of the LNG vaporizer;

[0123] A is the effective condensation surface area, with the unit of m2 , refers to the outer surface area of the heat exchange tubes in the vaporizer that are in direct contact with the cryogenic fluid and cause condensation.

[0124] K is the heat transfer coefficient, with the unit of W / (m 2 ·K), which is determined according to the design dimensions of the vaporizer;

[0125] ΔT is the temperature difference, with the unit of K, based on the operating temperature difference range of the LNG vaporizer;

[0126] t is the operating time, with the unit of h, based on the single-shift operating time;

[0127] η is the recovery efficiency, based on the design optimization and measured data of the condensate pan.

[0128] The contribution rate of condensate recovery is calculated using the following formula:

[0129]

[0130] In the formula: η cond is the contribution rate of condensate recovery, with the unit of %; m is the mass of condensate, calculated from Q water and has the unit of kg; L v is the latent heat of vaporization of water, with the unit of kJ / kg, and is default taken as 2260 kJ / kg (1 atm, 100 °C); E total is the total system energy consumption, with the unit of kJ, calculated according to the vaporizer power × operating time.

[0131] 3) Adding the outer shell will cause an increase in the wind resistance of the flow channel between the shell and tubes, and the wind resistance loss of the flow channel between the shell and tubes is specifically calculated as follows:

[0132] The wind resistance loss △η inter of the flow channel between the shell and tubes is calculated by the formula:

[0133]

[0134] In the formula: △P inter is the additional pressure drop (Pa) caused by adding the outer shell; ρ is the air density (kg / m 3 ); u is the natural convection wind speed (m / s)

[0135] The additional pressure drop △P inter caused by adding the outer shell is calculated by the formula:

[0136]

[0137] In the formula: C d is the wind resistance coefficient, dimensionless, representing the degree of obstruction of the outer shell to natural convection; L is the length of the outer shell (m), and the optimization range is 1.5 - 3.0 m; ρ is the air density (kg / m 3) Take the average value of the working condition (such as 1.184kg / m 3 , under standard conditions); u is the natural convection wind speed (m / s), 1.2m / s (obtained through CFD simulation).

[0138] Shell flow channel drag coefficient C d Optimization model of natural convection velocity u:

[0139]

[0140] Where: C d is the drag coefficient, dimensionless, representing the degree of resistance of the shell to natural convection; L is the shell length (m), the optimization range is 1.5m~3.0m; D is the equivalent diameter of the shell (m), Among them A flow is the cross-sectional area of ​​the air flow channel (m 2 ).

[0141] 4) The overall energy efficiency is greatly improved:

[0142] Compared with the prior art, the present invention improves the total energy efficiency by 42.6% (Example 1) compared with the traditional gasifier through multi-physical field coupling design, and the pressure drop increase is controlled within 18%, achieving the best balance between efficiency and stability, and realizing a breakthrough improvement in the total energy efficiency of the gasifier. First, the heat transfer coefficient is increased by 2 to 3 times through turbulence enhancement; second, the condensate recovery rate is greater than 95%, reducing latent heat waste; third, the cold island effect suppression and anti-corrosion design extend the equipment life by more than 40%. The comprehensive effect far exceeds the simple superposition of single technical improvements, and provides an innovative solution for industrial heat exchange equipment.

[0143] Example 1

[0144] The present invention provides a vaporizer with enhanced heat exchange based on spiral spoiler and detachable condensate tray. The vaporizer is mainly composed of heat exchange tube 1, spiral spoiler 2, condensate tray 3 and shell 4.

[0145] The heat exchange tube 1 adopts standard size and material, and can withstand 4.0MPa working pressure (safety factor 1.5), ensuring long-term stable operation. The first row of heat exchange tube 1 is built with equal length 304 stainless steel spiral spoilers, and the middle of the upper end of the spiral spoiler is perforated. The spiral spoiler is fixed to the inner wall of the tube by laser welding or mechanical expansion. The spiral angle of the spiral spoiler is 45° and the thickness is 0.8mm. The spiral spoiler is designed to destroy the laminar flow in the tube and force the fluid to form turbulence, thereby significantly improving the heat transfer coefficient.

[0146] According to the Dittus-Boelter formula, when Re = 5000 and Pr = 0.7, the smooth pipe

[0147] Nusmooth = 0.023 × 5000 0.8 × 0.7 0.4 = 120.3

[0148] The measured Nu of the heat exchange tube with spiral turbulators is 154.6, then

[0149]

[0150] The condensate recovery amount is as follows:

[0151] Q water = K · A · ΔT · t · η

[0152] Wherein: the heat transfer coefficient k is taken as 8.5 W / (m 2 · K); the temperature difference ΔT is taken as 35 K; the recovery efficiency η is taken as 92%; the condensate amount is 8.5 × 120 × 35 × 8 × 0.92 ≈ 258 kg.

[0153] A 316L stainless steel condensate pan is set at the bottom of the heat exchange tube. The thickness of the pan body is 2 mm, the bottom slope i = 0.01 (corresponding to an angle of 0.57°), and the covering area of the pan body is greater than 120% of the projected area of the tube bundle to prevent condensate from splashing.

[0154] The relationship between the condensate pan slope (i) and the drainage efficiency satisfies:

[0155] Q 有效 = Q water × (1 - e -k·i )

[0156] In the formula:

[0157] Q 有效 is the actual discharged cold water amount (kg / h);

[0158] k is an empirical coefficient (taking 0.8 - 1.2, related to the pan surface material, for stainless steel (316L): k = 1.0 (low surface roughness, high drainage efficiency));

[0159] i is the slope;

[0160] When the measured slope i = 0.01, the condensate recovery amount Q water = 258 kg / shift, and the retention amount Q 滞留 = 12.9 kg (accounting for 5%);

[0161] If i = 0.005, the retention amount increases to Q 滞留 = = 38.7 kg (accounting for 15%), verifying the significant influence of the slope on the drainage efficiency.

[0162] Condensate recovery contribution rate:

[0163]

[0164] Among them: The mass of the condensate water is calculated to be 258 kg from the condensate water recovery amount; the latent heat of vaporization of water is taken as 2260 kJ / kg, and the total energy consumption of the system is taken as 3.5×10 6 kJ based on the typical energy consumption range of the vaporizer, and the contribution rate of condensate water recovery is

[0165] Table 1: Comparison of condensate water retention amounts at different slopes

[0166] Gradient i Theoretical retention amount (%) Measured retention amount (%) Drainage time (min) 0.005 15.2 15.0 45 0.010 5.1 5.0 15 0.020 2.0 2.1 8

[0167] The recommended slope i = 0.01 (taking into account both efficiency and structural feasibility)

[0168] To verify the influence of the valve diameter on the drainage efficiency, the theoretical drainage time is calculated through the following formula:

[0169] The relationship between the condensate water drainage time (t drain ) and the slope (i), valve diameter (D valve ) satisfies:

[0170]

[0171] In the formula: V water is the volume of condensate water (m 3 ), which is converted from Q water (Q water / ρ, ρ = 1000 kg / m 3 ρ = 1000 kg / m 3 ) Q water = 258 kg, V water = 0.258 m 3 ; D valve is the diameter of the drain valve (m); g is the acceleration due to gravity, taken as 9.81 m / s 2 ; i is the inclination slope of the bottom of the condensate water tray, taken as 0.01 (i.e., 1% slope, corresponding to an angle of 0.57°);

[0172] L slope is the length of the drainage slope (m), which is determined according to the size of the vaporizer (such as 0.5 m).

[0173] The optimization of the diameter (D valve ) of the drain port 31 needs to meet two conditions:

[0174] (1) Flow rate requirement: Ensure that there is no liquid resistance and no water accumulation under the maximum condensate water flow rate (Q max );

[0175] (2) Requirements for preventing cavitation: Control the flow velocity below the critical value (v crit ), to prevent cavitation corrosion of the valve.

[0176] Its design formula is:

[0177]

[0178] Where:

[0179] Q max is the maximum condensate flow rate (m 3 / s), calculated from the heat transfer load;

[0180] v crit is the critical flow velocity (m / s), taken as 0.5 m / s (based on ASME B16.34 standard).

[0181] Calculation result:

[0182] When the maximum flow rate Q max = 258 kg / h, D valve ≥ 13 mm, so a DN20 (0.02 m) valve is preferably selected for the drain outlet 31, with a 30% redundancy reserved. The measured flow velocity v = 0.23 m / s (far lower than the critical value of 0.5 m / s), and the drainage is smooth without the risk of cavitation.

[0183] Measured data: When i = 0.01 and D valve = 0.02 m, the drainage time t drain ≤ 15 min, and the condensate retention is reduced to less than 5% of the total output.

[0184] The calculation results are as Figure 9 , shown in Table 2. The theoretical drainage time (14.2 min) of the DN20 valve is significantly better than that of DN15 (26.5 min). Therefore, a DN20 flanged drain valve is selected for the drain outlet 31, and a quick-connect fitting is configured at the outlet, which can be connected to a water pipe to the water storage container. A DN15 backwash ball valve is set at the lowest point of the bottom for sewage discharge when cleaning the equipment. A silicone rubber bellows is used to connect the drain outlet 31 and the water storage container.

[0185] Table 2: Comparison of valve diameter and theoretical drainage time

[0186] Valve diameter D (mm) Theoretical drainage time t (min) 15 26.5 20 14.2 25 8.1

[0187] Note: The calculated values already include a 10% safety margin, and the actual working conditions may vary slightly due to fluid viscosity. Figure 9 is the relationship curve of drainage time - valve diameter based on theoretical calculation (slope i = 0.01).

[0188] The outer shell 4 is made of stainless steel with a thickness of 2 mm and has functions such as dust-proof, waterproof, and anti-collision. An EPDM rubber or silicone rubber sealing strip is embedded at the joint between the outer shell 4 and the support to ensure dust-proof and waterproof at the joint. The optimized design of the outer shell 4 not only improves the protection performance of the vaporizer but also enhances its safety and stability.

[0189] Through ANSYS Fluent simulation, the measured average natural convection wind speed u = 1.2 m / s (environment 25 °C, ρ = 1.184 kg / m 3 ), the wind resistance coefficient (C d ) of the inter-shell flow channel varies with the length-diameter ratio (L / D) curve ( Figure 8 ) Note: The shaded area is the recommended optimization interval (1.5 ≤ L / D ≤ 3.0). When the length-diameter ratio of the outer shell is L / D = 2.0:

[0190] Calculate C d = 0.1 + 0.05 · (2.0) -1.2 = 0.122;

[0191] Additional pressure drop

[0192] Corresponding energy efficiency loss

[0193] Let the total weight of the equipment be W total = 500 kg;

[0194] Support span L span = 1.2, width b = 0.1 m;

[0195] Allowable stress of stainless steel σ allow = 120 MPa, calculate the thickness: actually select a stainless steel support with a thickness of 18 mm, safety factor 1.5.

[0196] Table 3: Comparison of support thicknesses of different materials

[0197] Material Allowable stress σ (MPa) Calculated thickness (mm) Actually selected thickness (mm) 316L stainless steel 120 12 18 Q235 carbon steel 160 10 15

[0198] Working principle: The liquefied natural gas is vaporized through turbulent heat exchange generated by the heat exchange tube 1 and the spiral turbulator 2, the condensed water is collected in the condensate pan 3 and discharged, and the outer shell 4 provides protection and plays a dust-proof role.

[0199] Calculate the total energy efficiency improvement rate of the vaporizer:

[0200] Turbulence enhancement contribution rate (η turb ):

[0201]

[0202] Condensate recovery contribution rate (η cond ):

[0203]

[0204] Air resistance loss (△η inter ) in the flow channel between the shell and the tube:

[0205]

[0206] Example 1 shows that, compared with the prior art, through multi-physical field coupling design, the present invention achieves a breakthrough improvement in the total energy efficiency of the vaporizer, with an overall energy efficiency improvement rate of 42.6%. For the specific structural design, please refer to the attached drawings.

Claims

1. A gasifier based on spiral turbulence to enhance heat exchange and integrated recovery of condensed water, characterized in that: A heat exchange tube (1), wherein a spiral spoiler (2) is arranged at the inlet section of the heat exchange tube (1) to form a turbulence inducing zone, a condensate water tray (3) is arranged at the bottom of the heat exchange tube (1), and a drain port (31) of the condensate water tray (3) is connected to a water storage container; the heat exchange tube (1) and the condensate water tray (3) are arranged in an outer shell (4).

2. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 1 is characterized in that: The spiral angle of the spiral spoiler (2) is designed according to the enhanced heat exchange requirements of the heat exchange tube (1), and is specifically determined by the following formula: Nu=0.023·Re 0.8 ·Pr 0.4 (1+Aα B ) Where: Nu is the Nusselt number of the heat exchange tube after adding the spiral spoiler, which represents the intensity of convective heat transfer; Re is the Reynolds number, Where ρ is the fluid density, u is the flow velocity, d is the pipe diameter, μ is the dynamic viscosity; Pr is the Prandtl number, Among them C P is the specific heat capacity, λ is the thermal conductivity; α is the helical angle of the spiral spoiler; A and B are the influence coefficients of the helical angle of the spiral spoiler on the heat transfer coefficient; It is required that the Nusselt number Nu of the heat exchange tube (1) after adding the spiral spoiler (2) is greater than the Nusselt number Nu of the smooth heat exchange tube smooth ; Nusselt number Nu of smooth heat exchange tube smooth The calculation of is as follows: Not smooth =0.023·Re 0.8 ·Pr 0.4 Where: Nu smooth is the Nusselt number of the smooth heat exchange tube, Re is the Reynolds number, and Pr is the Prandtl number.

3. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 2 is characterized in that: The spiral spoiler (2) is a stainless steel spiral spoiler, the spiral angle of the stainless steel spiral spoiler is 10° to 50°, the thickness is 0.1 mm to 2.5 mm, and the ratio of the pitch of the stainless steel spiral spoiler to the diameter of the heat exchange tube (1) is 2.5 / 1 to 10 / 1.

4. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 2 is characterized in that: The spiral spoiler (2) is fixed to the inner wall of the heat exchange tube (1) by laser welding or mechanical expansion, and a fixing hole (21) is arranged in the middle of the upper end of the spiral spoiler (2).

5. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 1 is characterized in that: The bottom of the condensate water tray (3) is provided with a slope toward the drain outlet (31), and the slope of the condensate water tray (3) is determined by the drainage efficiency, specifically as follows: The relationship between the slope of the condensate pan and the drainage efficiency satisfies: Q 有效 =Q water ×(1-e -k·i ) Where: Q 有效 is the actual amount of cold water discharged; k is the empirical coefficient; i is the slope; Q water is the amount of condensed water recovered; Q water =K·A·ΔT·t·η Where: A is the effective condensation surface area; K is the heat transfer coefficient; ΔT is the temperature difference; t is the operating time, in h, based on a single shift operating time; η is the recovery efficiency; Q 滞留 =Q water -Q 有效 Where: Q 滞留 is the condensate retention, the condensate retention is ≤5%; The diameter of the drain port 31 is determined according to the slope of the condensate pan and the condensate drainage time, as follows: Where: V water is the volume of condensed water, V water =Q water / ρ;D valve is the diameter of the drain valve; g is the acceleration of gravity; i is the slope of the bottom of the condensate tray; L slope is the length of drainage slope; Required drain outlet (31) diameter D valve The following conditions are met: Where: Q max is the maximum condensate flow rate; v crit is the critical flow rate.

6. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 5 is characterized in that: The bottom of the condensed water tray (3) has an inclination gradient i=0.01 towards the drain outlet (31).

7. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 1 is characterized in that: The condensation water tray (3) is detachably arranged at the bottom of the outer shell (4), and the coverage area of ​​the condensation water tray (3) is larger than the projection area of ​​the bottom of the heat exchange tube (1).

8. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 1 is characterized in that: A support is arranged in the housing (4), the support comprising four support legs (41) and a base plate (42) arranged at the bottom of each support leg (41), and every two support legs (41) are connected by a cross beam with a slope and a groove, and the cross beam can slide up and down along the two support legs (41) through a guide rail slider lock; The condensate tray (3) is detachably arranged on two cross beams of the support, the two cross beams have the same slope, and the two front support legs (41) are provided with wing-rotating lockers (5) for fixing the condensate tray (3).

9. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 8 is characterized in that: The thickness of the support leg (41) of the support in the housing (4) is designed according to the total weight of the equipment and the material strength, as follows: Where: W total is the total weight of the equipment, including the heat exchange tube (1), condensate tray (3) and casing (4); L span is the span between two supports; σ allow is the allowable stress of the material; b is the support width; Safety factor ≥1.5, actual thickness is 1.2 to 1.5 times the calculated value.

10. The gasifier based on spiral turbulence enhanced heat exchange and integrated condensed water recovery according to claim 1, characterized in that: The spiral spoiler (2), the condensate tray (3) and the shell (4) are provided to improve the overall energy efficiency of the gasifier, specifically including the turbulence enhancement contribution rate brought by the spiral spoiler (2), the condensate recovery contribution rate brought by the condensate tray (3) and the wind resistance loss of the flow channel between the shell (4) and the heat exchange tube (1) brought by the shell (4), wherein each item is recorded as: η turb is the contribution rate of turbulence enhancement; η cond is the contribution rate of condensed water recovery; Δη inter is the flow channel wind resistance loss; Among them, the turbulence enhancement contribution rate is calculated as follows: Where: η turb is the contribution rate of turbulence enhancement, Nu is the Nusselt number of the heat exchange tube after adding the spiral spoiler; Nu smooth is the Nusselt number of the smooth heat exchange tube; The Nusselt number Nu of the heat exchange tube after adding the spiral spoiler is calculated as follows: No=0.023·Re 0.8 ·Pr 0.4 (1+1.5sin 1.2 a) Nusselt number Nu of smooth heat exchange tube smooth The calculation of is as follows: Not smooth =0.023·Re 0.8 ·Pr 0.4 Where: Re is the Reynolds number, Where ρ is the fluid density, u is the flow velocity, d is the pipe diameter, μ is the dynamic viscosity; Pr is the Prandtl number, Among them C P is the specific heat capacity, λ is the thermal conductivity; α is the helical angle of the spiral spoiler; Among them, the condensed water recovery contribution rate is calculated as follows: Where: η cond is the contribution rate of condensed water recovery; m is the mass of condensed water, which is determined by the condensed water recovery amount Q water Calculated; L v is the latent heat of vaporization of water; E total is the total energy consumption of the system; Q water =K·A·ΔT·t·η Where: A is the effective condensation surface area; K is the heat transfer coefficient; ΔT is the temperature difference; t is the operating time, based on the single shift operating time; η is the recovery efficiency; Among them, the calculation formula for the wind resistance loss of the shell-tube flow channel is: Where: △η inter is the energy efficiency loss caused by the wind resistance of the flow channel between the shell and tube; △P inter is the additional pressure drop of the shell flow channel; ρ is the air density; u is the natural convection wind speed.

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