Partition design method for spiral tube heat exchanger

Abstract

The spiral pipe heat exchanger partition design method disclosed by the application comprises the following steps: S1, inputting the heat exchanger structure and operation parameters; S2, dividing the spiral pipe bundle radially into multiple layers, regarding the pipe network branches, establishing a layer flow distribution equation based on mass and pressure drop conservation, and solving the actual flow of each layer; S3, according to the flow of each layer, splitting the pipe of each layer into horizontal sections and vertical sections, iteratively calculating the flow and heat transfer characteristics of each section, and obtaining partition calculation results; S4, judging whether the calculation results meet the energy conservation and the design heat load, if not, returning to S2; S5, when the heat load is met, judging whether the pipe side and shell side pressure drops are less than the allowable values, if not, adjusting the structure parameters and returning to S2; and S6, outputting the temperature field, heat transfer coefficient distribution and pressure drop. The application solves the problems in the existing spiral pipe heat exchanger thermal design, such as uneven interlayer flow distribution of the pipe side, large axial temperature difference of the heat exchange pipe, and significant variation of the physical properties along the pipeline, which leads to low calculation accuracy.

Description

Technical Field

[0001] This invention belongs to the technical field of heat exchanger thermal calculation and structural design, specifically relating to a zoned design method for spiral tube heat exchangers. Background Technology

[0002] Spiral tube heat exchangers are widely used in air conditioning, petroleum, energy and other fields due to their compact size, simple structure and high heat transfer efficiency. Their thermodynamic performance and structural integrity design are of paramount importance.

[0003] Existing thermal design methods for spiral tube heat exchangers mostly employ zero-dimensional or one-dimensional simplified models, which have several technical shortcomings: First, most existing calculation models for spiral tube heat exchangers neglect interlayer flow differences, failing to accurately reflect the actual flow and heat transfer conditions inside the heat exchanger, resulting in low calculation accuracy and an inability to effectively support design optimization. Second, spiral tube heat exchangers have complex structures, significant axial heat transfer temperature differences and property variations, and differing fluid flow characteristics in different tube sections, posing considerable challenges to heat exchanger calculation and performance evaluation. Third, the flow and heat transfer differ in different tube sections of the spiral tube. The heat transfer coefficient K depends on the convective heat transfer coefficient of the fluids on both sides and the thermal conductivity of the solid, changing with factors such as the properties along the tube, the geometry of the heat transfer surface, and the flow state along the tube, resulting in a non-uniform distribution of the heat transfer coefficient K along the tube.

[0004] Existing design methods fail to adequately consider these factors, resulting in significant limitations in the design and optimization of traditional spiral tube heat exchangers. Therefore, a relatively accurate heat exchanger design methodology for spiral tube heat exchangers is currently lacking in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a zoned design method for spiral tube heat exchangers, which solves the problems of uneven flow distribution between tube layers, large axial temperature difference of heat exchange tubes, and significant changes in physical properties along the flow path that lead to low calculation accuracy in the thermal design of existing spiral tube heat exchangers.

[0006] The technical solution adopted in this invention is a zonal design method for spiral tube heat exchangers, comprising the following steps:

[0007] S1. Input the structural and operating parameters of the heat exchanger; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0008] The invention is further characterized by: In S1, the heat exchanger structural parameters include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations.

[0009] S2 specifically refers to: the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p sThe pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the main flow of MC in the spiral tube bundle flowing along the spiral curvature.

[0010] In S3, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. Specifically, a single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment.

[0011] The specific calculation of the flow and heat transfer characteristics of each segment in S3 is as follows: the logarithmic mean temperature difference method is used to calculate the heat transfer and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation.

[0012] The iterative calculation in S3 also includes calculating the convective heat transfer coefficient of each segment by selecting the corresponding heat transfer correlation based on the flow state and physical property parameters of each segment.

[0013] The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); (8); h = Not · λ / d (9); Among them, 2300≤ R e tube ≤10 6 ; Not tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; Different boiling conditions include saturated boiling in tubes, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); (10); The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); (11); The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); (12); in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C. Tsat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T lo The convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The reference heat transfer coefficient for nucleate boiling of a single-component fluid is denoted as .

[0014] The heat transfer coefficient for convective boiling is calculated using the following process; when R el When ≤4000, calculate according to formula (13); (13); When 4000 < R el When <10000, calculate according to formula (14); (14); when R el When the value is ≥10000, calculate according to formula (15); (15); in, R el The heat transfer coefficient for convective boiling conditions; h con-boil The heat transfer coefficient for convective boiling is W / (m²). K); F mix,con This is a correction factor for the convection of the mixture; F tp,o This is a correction factor for two-phase flow; Liquid phase thermal conductivity, unit: W / (m K); This is a fluid property correction factor.

[0015] The specific energy conservation condition in S4 is: the error between the sum of the heat exchange calculated in each partition and the total heat exchange calculated based on the overall parameters is within a preset range, which is between ±1% and ±5%. The heat exchange is calculated according to formula (16); (16); The undetermined outlet temperature is calculated according to formula (17); (17); in, Q For heat exchange, W; m The fluid mass flow rate is expressed in kg / s. c p Specific heat capacity at constant pressure of fluid, J / (kg) K); T The temperature difference between the fluid inlet and outlet is expressed in °C. t h,o The outlet temperature of the hot fluid is ℃; t h,i The inlet temperature of the hot fluid is ℃; C h denoted as the thermal capacity flow rate of the hot fluid, expressed in W / K.

[0016] The beneficial effects of this invention are: The spiral tube heat exchanger zonal design method provided by this invention employs interlayer flow distribution technology, analogizing each layer of the spiral tube to a pipe network system. Based on mass conservation and pressure drop conservation, an interlayer flow distribution equation is established to determine the actual flow distribution of each layer. Subsequently, combining the flow state and physical property parameters of each zone, the corresponding heat transfer correlation is selected, and segmented iterative calculations are performed along the path of each zone to obtain the internal temperature field, heat transfer coefficient, and heat transfer distribution of the spiral tube heat exchanger. On this basis, each spiral pipe is divided into multiple horizontal and vertical segments, and the flow and heat transfer characteristics of each segment are accurately calculated by substituting them into the relevant heat transfer correlation. This invention breaks through the limitations of traditional zero-dimensional or one-dimensional calculations of spiral tube heat exchangers, effectively improving the accuracy of spiral tube heat exchanger design calculations and providing a reliable basis for structural optimization and performance evaluation. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the spiral tube heat exchanger partition design method in Embodiment 8 of the present invention; Figure 2 This is a schematic diagram of the division of the horizontal and vertical sections of the spiral tube in Embodiment 8 of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] The present invention provides a zonal design method for a spiral tube heat exchanger, wherein the spiral tube heat exchanger includes a tube sheet, end caps, a shell, and a bundle of tubes spirally wound together, comprising the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, and analogous to Kirchhoff's laws for circuits, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layered division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the fact that the algebraic sum of the node mass flow rate is zero (the total mass flow rate flowing into the node is equal to the total mass flow rate flowing out of the node) and the algebraic sum of the closed loop pressure drop is zero (the pressure drop of the series flow path is added, and the pressure drop of the parallel flow path is equal), the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. Among them, the pressure of the fluid pipe network is analogous to the potential, the mass flow rate is analogous to the current, and the flow resistance is analogous to the resistance. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p sThe pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,iis the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; Iterative calculations also include using the corresponding heat transfer correlation to calculate the convective heat transfer coefficient of each segment based on the flow state and physical property parameters of each segment. The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); (8); h = Not · λ / d (9); Among them, 2300≤ R e tube ≤10 6 ; Not tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; Different boiling conditions include saturated boiling in tubes, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); (10); The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); (11); The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); (12); in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C.T sat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T lo The convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The core boiling reference heat transfer coefficient for a single-component fluid; The heat transfer coefficient for convective boiling is calculated using the following process; when R el When ≤4000, calculate according to formula (13); (13); When 4000 < R el When <10000, calculate according to formula (14); (14); when R el When the value is ≥10000, calculate according to formula (15); (15); in, R el The heat transfer coefficient for convective boiling conditions; h con-boil The heat transfer coefficient for convective boiling is W / (m²). K); F mix,con This is a correction factor for the convection of the mixture; F tp,o This is a correction factor for two-phase flow; Liquid phase thermal conductivity, unit: W / (m K); This is a fluid property correction factor; S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. The specific energy conservation condition is that the error between the sum of the heat exchange calculated for each zone and the total heat exchange calculated based on the overall parameters is within a preset range, which is between ±1% and ±5%. The heat exchange is calculated according to formula (16); (16); The undetermined outlet temperature is calculated according to formula (17); (17); in, Q For heat exchange, W; m The fluid mass flow rate is expressed in kg / s. c p Specific heat capacity at constant pressure of fluid, J / (kg) K); T The temperature difference between the fluid inlet and outlet is expressed in °C. t h,o The outlet temperature of the hot fluid is ℃; t h,i The inlet temperature of the hot fluid is ℃; C h The thermal capacity flow rate of the hot fluid is expressed in W / K. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0020] Breaking through the limitations of existing zero-dimensional or one-dimensional calculations for spiral tube heat exchangers, this method addresses the low calculation accuracy caused by uneven flow distribution between tube layers, large axial temperature differences in heat exchange tubes, and significant changes in physical properties along the tube. Through spatial partitioning and precise iterative calculations, it improves the accuracy of heat transfer coefficient and heat transfer calculations, providing a reliable basis for heat exchanger structure optimization and performance evaluation.

[0021] Example 1 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0022] Example 2 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p tThe pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0023] Example 3 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0024] Example 4 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; Iterative calculations also include using the corresponding heat transfer correlation to calculate the convective heat transfer coefficient of each segment based on the flow state and physical property parameters of each segment. S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0025] Example 5 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; Iterative calculations also include using the corresponding heat transfer correlation to calculate the convective heat transfer coefficient of each segment based on the flow state and physical property parameters of each segment. The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); (8); h = Not · λ / d (9); Among them, 2300≤ R e tube ≤10 6 ; Not tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; Different boiling conditions include saturated boiling in tubes, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); (10); The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); (11); The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); (12); in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C. T sat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T loThe convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The core boiling reference heat transfer coefficient for a single-component fluid; S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0026] Example 6 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area;m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; Iterative calculations also include using the corresponding heat transfer correlation to calculate the convective heat transfer coefficient of each segment based on the flow state and physical property parameters of each segment. The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); (8); h = Not · λ / d (9); Among them, 2300≤ R e tube ≤10 6 ; Not tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; Different boiling conditions include saturated boiling in tubes, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); (10); The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); (11); The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); (12); in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C. T sat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T lo The convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The core boiling reference heat transfer coefficient for a single-component fluid; The heat transfer coefficient for convective boiling is calculated using the following process; when R el When ≤4000, calculate according to formula (13); (13); When 4000 < R el When <10000, calculate according to formula (14); (14); when R el When the value is ≥10000, calculate according to formula (15); (15); in, R el The heat transfer coefficient for convective boiling conditions; h con-boil The heat transfer coefficient for convective boiling is W / (m²). K); F mix,conThis is a correction factor for the convection of the mixture; F tp,o This is a correction factor for two-phase flow; Liquid phase thermal conductivity, unit: W / (m K); This is a fluid property correction factor; S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0027] Example 7 The spiral tube heat exchanger zoning design method provided in this embodiment includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; The structural parameters of the heat exchanger include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; among these, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tubes, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids (counter-current or co-current), and whether the spiral tubes are integral tubesheets; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. Specifically, the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving it. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); (1); (2); in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m tThis refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of voltage drops in the closed loop is zero, calculated according to equation (3); (3); in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the mainstream MC flowing through the tube bundle along the spiral curvature. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. Specifically, each layer of pipeline is divided into horizontal and vertical segments along the axial direction. A single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation. The horizontal segment is the pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment. The vertical segment is the pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment. The iterative calculation of the flow and heat transfer characteristics of each segment is as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are solved iteratively. (4); (5); (6); in, T 1mThe logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation; Iterative calculations also include using the corresponding heat transfer correlation to calculate the convective heat transfer coefficient of each segment based on the flow state and physical property parameters of each segment. The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); (8); h = Not · λ / d (9); Among them, 2300≤ R e tube ≤10 6 ; Not tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; Different boiling conditions include saturated boiling in tubes, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); (10); The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); (11); The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); (12); in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C. T sat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T lo The convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The core boiling reference heat transfer coefficient for a single-component fluid; The heat transfer coefficient for convective boiling is calculated using the following process; when R el When ≤4000, calculate according to formula (13); (13); When 4000 < R el When <10000, calculate according to formula (14); (14); when R el When the value is ≥10000, calculate according to formula (15); (15); in, R el The heat transfer coefficient for convective boiling conditions; h con-boil The heat transfer coefficient for convective boiling is W / (m²). K); F mix,con This is a correction factor for the convection of the mixture; F tp,oThis is a correction factor for two-phase flow; Liquid phase thermal conductivity, unit: W / (m K); This is a fluid property correction factor; S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. The specific energy conservation condition is that the error between the sum of the heat exchange calculated for each zone and the total heat exchange calculated based on the overall parameters is within a preset range, which is between ±1% and ±5%. The heat exchange is calculated according to formula (16); (16); The undetermined outlet temperature is calculated according to formula (17); (17); in, Q For heat exchange, W; m The fluid mass flow rate is expressed in kg / s. c p Specific heat capacity at constant pressure of fluid, J / (kg) K); T The temperature difference between the fluid inlet and outlet is expressed in °C. t h,o The outlet temperature of the hot fluid is ℃; t h,i The inlet temperature of the hot fluid is ℃; C h The thermal capacity flow rate of the hot fluid is expressed in W / K. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

[0028] Example 8 The spiral tube heat exchanger zoning design method provided in this embodiment is as follows: Figure 1 As shown, it includes the following steps: Taking the design of a spiral tube heat exchanger as an example, the tube-side inlet temperature is 65℃, the tube-side mass flow rate is 4.6kg / s, the tube-side inlet pressure is 103kPa, and the maximum allowable pressure drop is 170kPa; the shell-side inlet temperature is 23℃, the outlet temperature is 50℃, the shell-side flow rate is 4.5kg / s, the shell-side inlet pressure is 690kPa, and the maximum allowable pressure drop is 170kPa. Heat exchange calculation: kW; Calculation of undetermined temperature: ℃; The heat exchanger is determined to be horizontally positioned with upward flow, and the spiral tube structure is a monolithic tube sheet heat exchanger. The spiral tube layers are set to 13, and the outer diameter of the tube bundle is 745 mm. The 13-layer spiral tube bundle is regarded as 13 branches of the pipeline system. The pressure of the fluid pipeline network is analogous to the potential, the mass flow rate is analogous to the current, and the flow resistance is analogous to the resistance. Based on the conservation equation that the mass flow rate at the node is 0 and the pressure drop of the closed loop is 0, the interlayer flow distribution equation is established by analogy with Kirchhoff's law of circuits. The actual mass flow rate of each of the 13 spiral tubes is obtained by solving the equation, and the accurate distribution of interlayer flow is completed. After calculation, it was found that due to the differences in flow channel length and flow resistance, the flow rate of each layer of the spiral tube is distributed with a slightly larger flow rate in the outer layer and a slightly smaller flow rate in the inner layer. The distribution results of the flow rate between single layers are shown in Table 1. Table 1 Summary of Flow Distribution Results Between Single-Layer Floors

[0029] The total flow rate of the 13-layer spiral tube is 4.6 kg / s, which is exactly the same as the total input flow rate on the tube side, satisfying the conservation condition that the nodal mass flow rate is 0. Based on the actual flow rate of each layer of the spiral tube, the flow rate of each layer of the spiral tube is calculated in segments along the flow path, such as... Figure 2 As shown, each layer of the spiral tube is divided into alternating series combinations of vertical and horizontal segments. Assuming the length of the spiral tube is L=1m, according to the spatial partitioning method, the lengths of the vertical and horizontal segments are L / 2=0.5m respectively; In this embodiment, the fluid flow inside the pipe is turbulent. R el The range is 5000 12000, select the corresponding heat transfer correlation, and introduce the two-phase correction coefficient and characteristic correction coefficient of the vertical and horizontal sections to calculate the heat transfer coefficient of each section. Liquid relative heat transfer coefficient h ll0 The calculation formula is as follows: W / (m 2 ·℃); The heat transfer coefficient of convective boiling is calculated by the following formula: When 4000 < R el <10000 hours: ; The two-phase correction factor for the vertical segment is: , ; The characteristic correction factor is: ; The two-phase correction factor for the horizontal segment is: , ; The characteristic correction factor is: ; Calculations show that the liquid-to-liquid convective heat transfer coefficient in the vertical section is 2729 W / (m²). 2 •℃); The liquid-to-liquid relative heat transfer coefficient in the horizontal section is 2388 W / (m²). 2 ·℃); The logarithmic mean temperature difference method is used, combined with the heat transfer coefficient and heat transfer area of ​​each pipe section, to iteratively solve the temperature distribution and heat transfer of each spiral tube along the flow direction. This process is repeated to complete the zonal calculation of the entire spiral tube heat exchanger. The energy conservation of the calculation results for each zone is verified. After confirming conservation, it is determined whether the overall heat transfer of the heat exchanger meets the design heat load requirements. In this embodiment, the calculated overall heat transfer meets the design heat load, so the process proceeds directly to the next step. If it does not meet the requirements, the interlayer flow rate is recalculated, and the zonal iteration calculation is performed again. Calculations show that the overall heat exchanger capacity is 509.2 kW, with a relative error of 0.08% compared to the design heat load of 508.77 kW, meeting the calculation accuracy requirements. In this embodiment, the calculated pressure losses on both the tube side and shell side are also less than the maximum allowable pressure drop (170 kPa), meeting the pressure drop design requirements. This design completed the zonal design calculations for the spiral tube heat exchanger, and the calculation results meet the requirements of energy conservation, design heat load, and pressure drop limits.

Claims

1. A zoned design method for spiral tube heat exchangers, characterized in that, Includes the following steps: S1. Input the structural and operating parameters of the heat exchanger; S2. Divide the spiral tube bundle radially into multiple layers, considering them as branches of the pipe network. Based on the conservation of mass and pressure drop, establish the interlayer flow distribution equation and solve for the actual flow of each layer. S3. Based on the flow rate of each layer, each layer of pipeline is divided into horizontal and vertical sections along the axial direction. The flow and heat transfer characteristics of each section are calculated iteratively to obtain the partition calculation results. S4. Determine whether the calculation results meet the energy conservation and design heat load requirements. If not, return to S2. S5. After the heat load is met, determine whether the pressure drop on the tube side and shell side is less than the allowable value. If not, adjust the structural parameters and return to S2. S6, output temperature field, heat transfer coefficient distribution and pressure drop.

2. The zonal design method for spiral tube heat exchangers according to claim 1, characterized in that, The heat exchanger structural parameters described in S1 include the inner diameter, outer diameter, pitch, and layout parameters of the heat exchange tubes; the operating parameters include the mass flow rates of the hot and cold fluids, the inlet and outlet temperatures, the tube-side and shell-side inlet pressures, and the maximum allowable pressure drop; wherein, the tube-side inlet pressure is used to calculate the physical properties of the fluid inside the tube, the shell-side inlet pressure is used to calculate the physical properties of the fluid on the shell side, and the maximum allowable pressure drop is used in subsequent S5 to determine whether the design meets the engineering requirements; the inner and outer diameters of the tubes in the structural parameters are used to calculate the flow cross-sectional area and heat exchange area, the pitch is used to determine the winding density and interlayer spacing of the spiral tubes, and the layout parameters include the horizontal or vertical placement of the heat exchanger, the flow direction of the hot and cold fluids being countercurrent or cocurrent, and the spiral tubes being an integral tube sheet type; the inlet and outlet temperatures include the undetermined outlet temperature, which is obtained through subsequent energy balance calculations.

3. The zonal design method for spiral tube heat exchangers according to claim 2, characterized in that, S2 specifically refers to: the multi-layer division of the spiral tube bundle is regarded as a branch of the pipe network system. Based on the zero algebraic sum of the node mass flow rate and the zero algebraic sum of the closed loop pressure drop, the inter-layer flow distribution equation is established, and the actual flow rate of each layer of the pipe is obtained by solving the equation. The algebraic sum of the node mass flow rates is zero, calculated according to equations (1) and (2); （1）； （2）； in, M T This represents the total mass flow rate within the spiral channel; m w The flow rate through the main spiral channel area; m t This refers to the leakage flow between the heat exchange tubes and the spiral baffles / plates; m s This refers to the leakage flow between the shell and the spiral baffle / plate. m c The main flow of the spiral heat exchanger is the effective heat exchange flow that flows along the spiral channel and vertically / obliquely across the heat exchange tubes. m b This is a bypass flow, an ineffective flow that flows along the gap between the shell and the helical tube bundle and bypasses the heat exchange tubes; The algebraic sum of the voltage drops in the closed loop is zero, calculated according to equation (3); （3）； in, p s The pressure drop due to leakage flow between the shell and the spiral baffle; p t The pressure drop due to leakage flow between the heat exchange tube and the spiral baffle; p b For bypass flow m b Pressure drop along the gap; p w The pressure drop of the fluid flowing through the bend region of the spiral channel; p c The pressure drop is caused by the main flow of MC in the spiral tube bundle flowing along the spiral curvature.

4. The zonal design method for spiral tube heat exchangers according to claim 3, characterized in that, The method described in S3 for dividing each layer of pipeline into horizontal and vertical segments along the axial direction is as follows: a single continuous spiral pipe bundle is decomposed into alternating horizontal and vertical segments along the axial direction as the smallest unit for friction calculation; the horizontal segment is a pipe segment in which the spiral pipe is in an approximately horizontal direction in one turn, including the upper horizontal segment and the lower horizontal segment; the vertical segment is a pipe segment in which the spiral pipe is in an approximately vertical direction in one turn, including the right vertical segment and the left vertical segment.

5. The zonal design method for spiral tube heat exchangers according to claim 4, characterized in that, The iterative calculation of the flow and heat transfer characteristics of each segment in S3 is specifically as follows: the logarithmic mean temperature difference method is used to calculate the heat exchange and temperature difference of each segment according to equations (4) to (7), and the temperature distribution, heat transfer coefficient and pressure distribution along the friction of the segment are iteratively solved. （4）； （5）； （6）； in, T 1m The logarithmic mean temperature difference; T 1、 T 2 represents the temperature difference between the hot and cold fluids at both ends of the heat exchanger, in °C; T h,i The inlet temperature of the hot fluid is ℃; T c,o The outlet temperature of the cold fluid is ℃; T h,o The outlet temperature of the hot fluid is ℃; T c,i is the inlet temperature of the cold fluid, ℃; Equation (5) is used for the temperature difference in counter-current operation; Equation (6) is used for the temperature difference calculation in co-current operation.

6. The zonal design method for spiral tube heat exchangers according to claim 5, characterized in that, The iterative calculation described in S3 also includes calculating the convective heat transfer coefficient of each segment by selecting the corresponding heat transfer correlation based on the flow state and physical property parameters of each segment.

7. The spiral tube heat exchanger zoning design method according to claim 6, characterized in that, The corresponding heat transfer correlations include the Gnielinski correlation and heat transfer correlations under different boiling conditions; The heat transfer coefficient is calculated using the Gnielinski correlation as follows: Calculate according to equations (8) and (9); （8）； h = Nu · λ / d （9）； Among them, 2300≤ R e tube ≤10 6 ; Nu tube For the Nusselt number within the tube; λ tube The thermal conductivity of the fluid inside the pipe is (W / (m²)). K)); P r tube It is a Prandtl number; d i The inner diameter of the circular tube is in meters (m). c t This is a temperature correction factor used to correct for the effects of temperature changes on fluid properties. c r This is the curvature correction factor; The different boiling conditions include saturated boiling in the tube, subcooled boiling, nucleation boiling, and convection boiling. The heat transfer coefficient under saturated boiling conditions inside the tube is calculated according to equation (10); （10）； The heat transfer coefficient for subcooled boiling conditions is calculated according to equation (11); （11）； The heat transfer coefficient under nucleate boiling conditions is calculated according to equation (12); （12）； in, h nuc-boil The heat transfer coefficient for nucleate boiling is W / (m²). K); h con-boil This represents the convective heat transfer component under saturated boiling conditions. T w The pipe wall temperature is in °C. T sat The fluid saturation temperature is ℃. T b The bulk temperature of the fluid is ℃; T lo The convective heat transfer coefficient for all-liquid phase flow is expressed in W / (m²). K); F s For surface correction factors; F mix For mixture correction factors; h sing-boil The reference heat transfer coefficient for nucleate boiling of a single-component fluid is denoted as .

8. The zonal design method for spiral tube heat exchangers according to claim 7, characterized in that, The heat transfer coefficient for the convective boiling condition is calculated according to the following process; when R el When ≤4000, calculate according to formula (13); （13）； When 4000 < R el When <10000, calculate according to formula (14); （14）； when R el When the value is ≥10000, calculate according to formula (15); （15）； in, R el The heat transfer coefficient for convective boiling conditions; h con-boil The heat transfer coefficient for convective boiling is W / (m²). K); F mix,con This is a correction factor for the convection of the mixture; F tp,o This is a correction factor for two-phase flow; Liquid phase thermal conductivity, unit: W / (m K); This is a fluid property correction factor.

9. The zonal design method for spiral tube heat exchangers according to claim 8, characterized in that, The energy conservation condition in S4 is specifically as follows: the error between the sum of the heat exchange calculated in each partition and the total heat exchange calculated based on the overall parameters is within a preset range, which is between ±1% and ±5%. The heat exchange is calculated according to formula (16); （16）； The undetermined outlet temperature is calculated according to formula (17); （17）； in, Q For heat exchange, W; m The fluid mass flow rate is expressed in kg / s. c p Specific heat capacity at constant pressure of fluid, J / (kg) K); T The temperature difference between the fluid inlet and outlet is expressed in °C. t h,o The outlet temperature of the hot fluid is ℃; t h,i The inlet temperature of the hot fluid is ℃; C h denoted as the thermal capacity flow rate of the hot fluid, expressed in W / K.

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