Design method of vacuum condenser

Abstract

The invention discloses a design method of a vacuum condenser, which relates to the field of heat exchange equipment and comprises the following steps: S1, preliminarily determining structural parameters of the vacuum condenser according to design parameters; s2, a preliminary heat exchange tube arrangement diagram is completed according to the structural parameters; s3, through the mode of the equivalent heat exchanger, computer software is used for conducting process and hydraulic calculation, and the heat transfer coefficient, the heat exchange area, the pipe bundle pressure drop, the inlet connecting pipe pressure drop and the non-condensable gas outlet connecting pipe pressure drop are determined; s4, calculating the turning pressure drop at the turning position of the medium; s5, the overall pressure drop of the vacuum condenser is calculated, and if the requirement is met, a model selection scheme is determined; if not, returning to S1 to redesign; s6, determining a final scheme; according to the method, the data accuracy is high, the optimization effect of the structural parameters is good, the structure of the vacuum condenser can be improved, the size of the vacuum condenser can be reduced, the calculation accuracy of the vacuum condenser can be improved, and meanwhile overall optimization of a vacuumizing system, equipment investment reduction and operation energy consumption reduction are facilitated.

Description

Technical Field

[0001] The invention relates to the field of heat exchange equipment, and in particular to a design method for a vacuum condenser. Background Art

[0002] The vacuum condenser is one of the key equipment in the vacuum system. It cools the oil and gas pumped out by the pump, partially condenses it, and then discharges the condensate to reduce the system temperature. The performance of the condenser (including heat transfer efficiency and pressure drop) and its stability are directly related to the reliability of the vacuum system.

[0003] Since the oil and gas extracted by the vacuum pump have the characteristics of low operating pressure and small heat transfer coefficient, the cooler usually needs to optimize the internal structure by setting special flow channels, increasing the number of pipe passes, etc. This makes it impossible to complete the heat transfer and hydraulic calculations of the vacuum condenser simply through mainstream professional calculation software (such as HTRI, EDR, etc.). Designers are also required to combine theory and experience for manual calculations, resulting in low data accuracy and poor structural parameter optimization effects.

[0004] Therefore, people are in urgent need of a design method for a vacuum condenser with good structural parameter optimization effect. Summary of the invention

[0005] The purpose of the present invention is to provide a design method for a vacuum condenser to solve the problems existing in the above-mentioned prior art and to improve the optimization effect of structural parameters by means of equivalent heat exchanger calculation.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a design method for a vacuum condenser, comprising the following steps: S1: Preliminarily determine the structural parameters of the vacuum condenser according to the design parameters of the vacuum condenser; S2: Complete the preliminary heat exchange tube layout diagram according to the determined vacuum condenser structural parameters, and determine the baffle position and size, pipe position and anti-impact height; S3: By means of an equivalent heat exchanger, computer software is used to perform process and hydraulic calculations to determine the heat transfer coefficient, heat exchange area, tube bundle pressure drop, inlet pipe pressure drop, and non-condensable gas outlet pipe pressure drop; S4: Calculate the directional pressure drop at the turning point of the medium according to the baffle size; S5: Calculate the overall pressure drop of the vacuum condenser. If it meets the requirements, determine the selection plan; if it does not meet the requirements, return to S1 to adjust the plan and recalculate; S6: Determine the final plan and complete the preparation of process documents.

[0007] Preferably, in step S1, the design parameters of the vacuum condenser include medium operating temperature, operating pressure, physical property data, design temperature, design pressure, and equipment material.

[0008] Preferably, in step S1, the structural parameters of the vacuum condenser are determined by computer software, and the structural parameters of the vacuum condenser include equipment diameter, number of tube passes, number of heat exchange tubes, length of heat exchange tubes, size of connecting pipes and number of connecting pipes.

[0009] Preferably, in step S2, the baffle divides the fluid flow path in the vacuum condenser shell into three parts: a two-phase downstream area, a gas phase turning area and a gas-liquid diversion area. In step S3, all the heat exchange tubes are divided into a number of units according to the number of heat exchange tube rows along the fluid flow direction in the shell. The size of the equivalent heat exchanger is determined according to the number of heat exchange tube rows and the number of heat exchange tubes in each row of the three areas. The number of heat exchange tube rows and the number of heat exchange tubes in each row of the equivalent heat exchanger are the same as those in the corresponding areas. Computer software is used to simulate and calculate the three equivalent heat exchangers in series to obtain the heat transfer coefficient and pressure drop of each of the three parts, and then the overall heat transfer coefficient, pressure drop and area margin of the heat exchange tubes are obtained.

[0010] Preferably, the pressure drop of each area or the equivalent heat exchanger corresponding to the area is the sum of the pressure drops of all units in the area or the equivalent heat exchanger, and the heat transfer coefficient is the average value of the heat transfer coefficients of all units in the area or the equivalent heat exchanger calculated according to the load ratio.

[0011] Preferably, after step S3, it is determined whether the pressure drop and the heat exchange area can meet the margin requirement based on the calculation results. If so, proceed to step S4; if not, return to step S1, adjust the structural parameters and recalculate.

[0012] Preferably, in step S5, the overall pressure drop of the vacuum condenser includes the tube bundle pressure drop, the inlet pipe pressure drop, the non-condensable gas outlet pipe pressure drop and the change-of-direction pressure drop.

[0013] Preferably, after step S5, local optimization is performed on the heat exchange tubes based on the selection scheme, and bypass baffles are added and local optimization measures are taken to increase the non-pipeline area.

[0014] Preferably, in step S2, the tube side arrangement is fully considered when arranging the heat exchange tubes, so that the tube side medium and the flowing medium in the shell are fully counter-flowed.

[0015] Preferably, in step S2, the flow direction of the medium in the tube side is perpendicular to the flow direction of the flowing medium in the shell.

[0016] Compared with the prior art, the present invention mainly achieves the following technical effects: After the structural parameters of the vacuum condenser are preliminarily determined, the heat exchange tube layout diagram is completed using the structural parameters. On this basis, relevant data are calculated using the equivalent heat exchanger calculation method. The feasibility of the current plan is judged by the calculation results, and then the plan is determined. There is no need for manual calculations, which improves data accuracy and thus improves the optimization effect of the structural parameters. This can not only improve the structure of the vacuum condenser, reduce the volume of the vacuum condenser, and improve the calculation accuracy of the vacuum condenser, but also is beneficial to the overall optimization of the vacuum system, reduce equipment investment, and reduce operating energy consumption, with obvious social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 is a flow chart of a vacuum condenser design method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the appearance structure of a vacuum condenser in an embodiment of the present invention; Figure 3 It is a tube bundle arrangement diagram of the shell in an embodiment of the present invention; Figure 4 Schematic diagram of the flow characteristics and path of the fluid to be cooled in an embodiment of the present invention; Figure 5 Schematic diagram of the structure of an equivalent heat exchanger in a two-phase downstream zone in an embodiment of the present invention; Figure 6 It is a schematic diagram of the structure of an equivalent heat exchanger in the gas phase turning zone in an embodiment of the present invention; Figure 7 It is a structural schematic diagram of an equivalent heat exchanger in the gas-liquid splitting area in an embodiment of the present invention; Among them, 1. Shell; 2. Inlet connecting pipe; 3. Non-condensable gas outlet connecting pipe; 4. Condensate outlet connecting pipe; 5. Refrigerant inlet connecting pipe; 6. Refrigerant outlet connecting pipe; 7. Drain connecting pipe; 8. Process gas side exhaust connecting pipe; 9. Fixed saddle; 10. Sliding saddle; 11. Tube bundle; 12. Heat exchange tube; 13. Baffle; 14. Bypass baffle; 15. Non-pipe area; 16. Two-phase downstream area; 17. Gas phase turning area; 18. Gas-liquid diversion area. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The purpose of the present invention is to provide a design method for a vacuum condenser to solve the problems existing in the prior art and to improve the optimization effect of structural parameters by calculating an equivalent heat exchanger.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Please refer to Figures 1 to 7 As shown, a design method for a vacuum condenser is provided, comprising the following steps: S1: Preliminarily determine the structural parameters of the vacuum condenser based on the design parameters of the vacuum condenser (including medium operating temperature, operating pressure, physical property data, design temperature, design pressure, equipment material, etc.); S2: Complete the preliminary layout of the heat exchange tube 12 according to the determined vacuum condenser structural parameters, determine the position and size of the baffle 13, the position of the pipe (inlet pipe 2, non-condensable gas outlet pipe 3, condensate outlet pipe 4, etc.) and the anti-impact height (the distance between the inlet pipe 2 and the heat exchange tube 12 directly impacted by the fluid); S3: By means of an equivalent heat exchanger, process and hydraulic calculations are performed using computer software to determine the heat transfer coefficient, heat exchange area, tube bundle pressure drop, inlet pipe 2 pressure drop, and non-condensable gas outlet pipe 3 pressure drop; S4: Calculate the direction-changing pressure drop at the turning point of the medium according to the size of the baffle 13; S5: Calculate the overall pressure drop of the vacuum condenser (including the pressure drop of the tube bundle 11, the pressure drop of the inlet pipe 2, the pressure drop of the non-condensable gas outlet pipe 3, and the pressure drop of the change direction). If the requirements are met, determine the selection plan; if the requirements are not met, return to S1 to adjust the plan and recalculate; S6: Determine the final plan and complete the preparation of process documents.

[0023] The structural parameters of the vacuum condenser are determined by computer software (such as HTRI, EDR, etc.) or determined based on the computer software in combination with the designer's experience. The structural parameters of the vacuum condenser include equipment diameter, number of tube passes, number of heat exchange tubes 12, length of heat exchange tubes 12, pipe size and number of pipes, etc.

[0024] In step S2, the baffle 13 is a structure arranged in the vacuum condenser shell 1 to extend the fluid flow path. It is arranged between the inlet pipe 2 and the non-condensable gas outlet pipe 3 to make the fluid flow path V-shaped. The baffle 13 divides the fluid flow path in the vacuum condenser shell 1 into three parts: a two-phase downstream zone 16, a gas phase turning zone 17 and a gas-liquid diversion zone 18.

[0025] The "equivalence" principle in this embodiment is as follows: Because the heat transfer coefficient can be regarded as a function of the medium flow rate, temperature difference and physical properties, and the pressure drop can be regarded as a function of the medium flow rate, process and physical properties, the heat transfer coefficient and pressure drop of the i-th row of heat exchange tubes 12 (i.e., the i-th unit) can be expressed as: ; ; Wherein K is the heat transfer coefficient; M is the number of heat exchange tubes 12, and the spacing between them (i.e., the flow area) determines the medium flow rate; ΔT is the heat transfer temperature difference; P1, P2, etc. are all medium properties; ΔP is the pressure drop; N is the number of tube rows, which is used to characterize the medium flow.

[0026] Therefore, the heat transfer coefficient of each area or the equivalent heat exchanger corresponding to the area is the average value of the heat transfer coefficients of all units in the area or the equivalent heat exchanger calculated according to the load ratio, and the pressure drop is the sum of the pressure drops of all units in the area or the equivalent heat exchanger.

[0027] The specific pressure drop and heat transfer coefficient calculation formula is:

[0028] ; Where Q is the heat load, is the average heat transfer temperature difference.

[0029] Therefore, based on the zoning effect of the baffle 13, in step S3, the tube bundle 11 is divided into a number of units according to the number of rows of heat exchange tubes 12 along the fluid flow direction in the shell 1, and the size of the equivalent heat exchanger is determined according to the number of rows of heat exchange tubes 12 in each of the three regions and the number of heat exchange tubes 12 in each row. The number of rows of heat exchange tubes 12 and the number of heat exchange tubes 12 in each row of the equivalent heat exchanger are the same as those in the corresponding regions. Computer software is used to simulate and calculate the three equivalent heat exchangers in a three-unit series manner, and the heat transfer coefficient and pressure drop of each of the three parts are obtained, thereby obtaining the overall heat transfer coefficient, pressure drop and area margin of the heat exchange tubes 12.

[0030] After step S3, it is determined whether the pressure drop and the heat exchange area can meet the margin requirements based on the calculation results. If they can, proceed to step S4; if not, return to step S1, adjust the structural parameters and recalculate.

[0031] The calculation formula for the directional pressure drop at the turning point of the medium is:

[0032] Among them, F i : fluid mass flow rate, kg / m2s; ρ iD : Fluid density, kg / m 3 ; N: Correction coefficient representing the turning angle. If the turn is approximately 90 degrees, the correction coefficient is 1; After step S5, the heat exchange tube 12 is locally optimized based on the selected scheme, and local optimization measures such as adding a bypass baffle 14 and increasing a non-pipe area 15 are taken. The bypass baffle 14 is to prevent fluid bypass, and the non-pipe area 15 is to form a uniform gas channel to improve the uniformity of fluid flow there and prevent the formation of a dead zone with poor fluid flow inside the gas-liquid diversion area 18.

[0033] In step S2, the tube side layout is fully considered when arranging the heat exchange tubes 12, so that the medium in the tube side and the flowing medium in the shell 1 are fully counter-flowed, thereby improving the heat transfer effect.

[0034] Considering that the medium flow rate is very high under high vacuum conditions and the equipment is very prone to vibration, in step S2, the flow direction of the medium in the tube is perpendicular to the flow direction of the flowing medium in the shell 1 to ensure that the equipment will not be damaged by vibration.

[0035] The vacuum condenser designed in this embodiment is a floating head vacuum condenser, and the heat exchange tube 12 can be pulled out, which is convenient for later maintenance and cleaning.

[0036] In this embodiment, the number of tube passes is 6-8, so that the circulating water can reach the highest possible flow rate on the basis of satisfying the pressure drop, so as to improve the heat exchange efficiency and slow down the deposition of dirt.

[0037] The fluid in the gas-liquid split zone 18 designed in this embodiment flows obliquely upward, and the gas-liquid two phases are separated under the action of gravity. The use of the "reflux condenser" model in the equivalent calculation process helps to more accurately simulate the pressure drop and heat transfer performance.

[0038] The vacuum condenser designed in this embodiment includes a shell 1, an inlet pipe 2, a non-condensable gas outlet pipe 3, a condensate outlet pipe 4, a refrigerant inlet pipe 5, a refrigerant outlet pipe 6, a sewage pipe 7, a process gas side exhaust pipe 8, a fixed saddle 9, a sliding saddle 10, a tube bundle 11, a baffle 13, a bypass baffle 14, a non-pipe area 15, a two-phase downstream area 16, a gas phase turning area 17 and a gas-liquid diversion area 18, each of which is arranged on the shell 1, wherein the inlet pipe 2 is used to supply the fluid to be cooled, the non-condensable gas outlet pipe 3 is used to discharge the gas phase fluid, the condensate outlet pipe 4 is used to discharge the cooled condensate, the refrigerant inlet / outlet pipes are used to supply / discharge the refrigerant, and the sewage pipes on both sides are used to discharge the gas phase fluid. The pipe 7 is used to discharge sewage in the cavities on both sides of the shell 1 (the cavities on both sides are the pipe box cavity connected to the refrigerant inlet pipe 5 and the refrigerant outlet pipe 6, and the spherical cavity on the other side connected to the inner cavity of the shell 1), the process gas side exhaust pipe 8 is used to discharge the gas in the shell 1, the fixed saddle 9 and the sliding saddle 10 are used for support, the tube bundle 11 is arranged in the shell 1 and is parallel to the axis of the shell 1. The tube bundle 11 is composed of a plurality of heat exchange tubes 12 arranged; the baffle 13 is fixedly arranged in the shell 1 to divide the inner cavity of the shell 1 into a V-shaped channel; the bypass baffle 14 blocks the gap between the tube bundle 11 and the inner wall of the shell 1 to prevent the bypass flow of the fluid to be cooled; the non-pipe area 15 is used to improve the flow uniformity.

[0039] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0040] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0041] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A design method for a vacuum condenser, characterized in that: The following steps are involved: S1: Preliminarily determine the structural parameters of the vacuum condenser according to the design parameters of the vacuum condenser; S2: Complete the preliminary heat exchange tube layout diagram according to the determined vacuum condenser structural parameters, and determine the baffle position and size, pipe position and anti-impact height; S3: By means of an equivalent heat exchanger, computer software is used to perform process and hydraulic calculations to determine the heat transfer coefficient, heat exchange area, tube bundle pressure drop, inlet pipe pressure drop, and non-condensable gas outlet pipe pressure drop; S4: Calculate the directional pressure drop at the turning point of the medium according to the baffle size; S5: Calculate the overall pressure drop of the vacuum condenser. If it meets the requirements, determine the selection plan; if it does not meet the requirements, return to S1 to adjust the plan and recalculate; S6: Determine the final plan and complete the preparation of process documents.

2. The design method of the vacuum condenser according to claim 1, characterized in that: In step S1 , the design parameters of the vacuum condenser include medium operating temperature, operating pressure, physical property data, design temperature, design pressure, and equipment material.

3. The design method of the vacuum condenser according to claim 2, characterized in that: In step S1, the structural parameters of the vacuum condenser are determined by computer software, and the structural parameters of the vacuum condenser include equipment diameter, number of tube passes, number of heat exchange tubes, length of heat exchange tubes, size of connecting pipes, and number of connecting pipes.

4. The design method of the vacuum condenser according to claim 1, characterized in that: In step S2, the baffle divides the fluid flow path in the vacuum condenser shell into three parts: a two-phase downstream area, a gas phase turning area and a gas-liquid diversion area. In step S3, all heat exchange tubes are divided into several units according to the number of heat exchange tube rows along the fluid flow direction in the shell. The size of the equivalent heat exchanger is determined according to the number of heat exchange tube rows and the number of heat exchange tubes in each row in the three areas. The number of heat exchange tube rows and the number of heat exchange tubes in each row of the equivalent heat exchanger are the same as those in the corresponding area. Computer software is used to simulate and calculate the three equivalent heat exchangers in a three-unit series manner to obtain the heat transfer coefficient and pressure drop of each of the three parts, and then obtain the heat transfer coefficient, pressure drop and area margin of the heat exchange tube as a whole.

5. The design method of the vacuum condenser according to claim 4, characterized in that: The pressure drop of each area or the equivalent heat exchanger corresponding to the area is the sum of the pressure drops of all units in the area or the equivalent heat exchanger, and the heat transfer coefficient is the average value of the heat transfer coefficients of all units in the area or the equivalent heat exchanger calculated according to the load ratio.

6. The design method of the vacuum condenser according to claim 4, characterized in that: After step S3, it is determined whether the pressure drop and the heat exchange area can meet the margin requirement based on the calculation results. If they can, proceed to step S4; if not, return to step S1, adjust the structural parameters and recalculate.

7. The design method of the vacuum condenser according to claim 1, characterized in that: In step S5, the overall pressure drop of the vacuum condenser includes the tube bundle pressure drop, the inlet pipe pressure drop, the non-condensable gas outlet pipe pressure drop and the change-of-direction pressure drop.

8. The design method of the vacuum condenser according to claim 1, characterized in that: After step S5, local optimization is performed on the heat exchange tubes based on the determined selection scheme, and bypass baffles are added and local optimization measures are taken to increase the non-pipeline area.

9. The design method of the vacuum condenser according to claim 1, characterized in that: In step S2, the tube side layout is fully considered when arranging the heat exchange tubes, so that the medium in the tube side and the flowing medium in the shell are fully counter-flowed.

10. The design method of the vacuum condenser according to claim 1, characterized in that: In step S2, the flow direction of the medium in the tube side is perpendicular to the flow direction of the flowing medium in the shell.

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