Design method of heat exchange section of air-temperature type gasifier

Abstract

The present application relates to heat exchanger technical field. The present application discloses a kind of design method of heat exchange zone of air temperature type gasifier, comprising the following steps: preliminary design the arrangement and quantity of gasifier tube pass;Determine medium fluid state;Calculate the heat exchange area required in supercooling section interval, vaporization section interval and supercooling section interval;According to the heat exchange area, the heat exchange tube height of supercooling section interval, vaporization section interval and heating section interval is deduced, and the preliminary design of tube pass layout is obtained;According to the preliminary design of tube pass layout, check calculation is carried out, and the check calculation value of the heat exchange area required in supercooling section interval, vaporization section interval and heating section interval is obtained;According to the check calculation value, the heat exchange area ratio of which surface temperature is higher than dew point temperature in gasifier is obtained, the heat exchange area which is higher than dew point temperature is separated out and located in first gasifier, and the remaining heat exchange area is located in second gasifier;If check calculation value exceeds or is less than the heat exchange area value of the design of tube pass layout by 10%, then redesign tube pass layout.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and in particular to a method for designing the heat exchange zone of an ambient air vaporizer. Background Technology

[0002] An air-cooled vaporizer is a device that converts subcooled gas from a liquid to a gaseous state. An ambient air vaporizer uses air as the heat exchange medium; air flows downwards from the top of the vaporizer, carrying away the cooling energy and achieving heat exchange, resulting in energy-saving and environmentally friendly performance. Based on the different gas states, an ambient air vaporizer consists of a subcooling section, a vaporization section, and a heating section. The gas is liquid in the subcooling section, a gas-liquid mixture in the vaporization section, and a gaseous state in the heating section. The subcooling section, vaporization section, and heating section are integrated into a single device.

[0003] In existing technologies, to achieve continuous operation, two ambient air vaporizers are connected in parallel, with only one operating at a time. When the surface of the ambient air vaporizer frosts or freezes, the heat exchange efficiency drops significantly. At this point, the other ambient air vaporizer is switched on. This requires both ambient air vaporizers to have high operating capacities. However, the operating capacity of an ambient air vaporizer is related to the number of pipes. A higher-capacity ambient air vaporizer is larger, requires more materials, resulting in a larger footprint and higher equipment costs.

[0004] Therefore, how to provide a design method for the heat exchange zone of an ambient air vaporizer to reduce the size of the equipment is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to propose a design method for the heat exchange zone of an ambient air vaporizer. The method involves verifying the pre-designed tube layout, using the verified value in conjunction with the ambient dew point temperature to calculate the proportion of heat exchange area where the surface temperature is higher than the dew point temperature, and then isolating this portion of the heat exchange area as a separate vaporizer. This can significantly reduce equipment materials and shrink the equipment size.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for designing the heat exchange zone of an ambient air vaporizer includes the following steps:

[0008] Based on the site area and medium flow rate, the arrangement and quantity of the vaporizer tubes are designed in advance;

[0009] Calculate the medium flow rate in the subcooled zone, vaporization zone, and heating zone based on the arrangement and number of tubes, and determine the medium fluid state;

[0010] Based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, calculate the required heat transfer area for the subcooled section, the vaporization section, and the subcooled section.

[0011] The heat exchange tube heights of the subcooling zone, vaporization zone, and heating zone are deduced from the heat exchange area to obtain the pre-designed tube layout;

[0012] Based on the pre-designed tube layout, calculations are performed to obtain the required heat exchange areas for the subcooled zone, vaporization zone, and heating zone.

[0013] Based on the calculation values, the proportion of heat exchange area in the vaporizer whose surface temperature is higher than the dew point temperature is determined. This heat exchange area with a surface temperature higher than the dew point temperature is separated and located in the first vaporizer, while the remaining heat exchange area is located in the second vaporizer.

[0014] If the calculated value exceeds or falls below 10% of the heat exchange area of ​​the designed tube layout, the tube layout should be redesigned.

[0015] Furthermore, the steps for calculating the required heat transfer area for the subcooled section, vaporization section, and subcooled section based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer are as follows:

[0016] Calculate the relative temperature difference t between the external temperature and the medium on each surface of the vaporizer;

[0017] Calculate the surface heat transfer coefficient W1 between the outside air and the vaporizer;

[0018] Calculate the thermal resistance of the vaporizer material and the efficiency η of the fins;

[0019] Calculate the heat transfer coefficient W2 of the medium fluid in the subcooled zone, vaporization zone, and heating zone;

[0020] Calculate the thermal resistance R of the vaporizer after prolonged use due to the accumulation of dirt.

[0021] Calculate the required heat exchange area for the subcooled zone, vaporization zone, and heating zone based on t, W1, η, W2, and R.

[0022] Furthermore, the method for calculating the relative temperature difference t between the external temperature and the medium on various surfaces of the vaporizer is as follows:

[0023] The calculation formula is selected based on the state of the medium fluid. When the medium fluid is in liquid or gas state, the arithmetic mean temperature difference formula is used, and when the medium fluid is in a gas-liquid mixed state, the logarithmic mean temperature difference formula is used.

[0024] Based on the temperature difference formula above, and considering the co-current and counter-current flow of the medium fluid and the external air fluid, the relative temperature difference t on the surface of the vaporizer is calculated.

[0025] Furthermore, the method for setting the surface heat transfer coefficient W1 between the outside air and the vaporizer is as follows: first, set an empirical value, and then correct it during verification.

[0026] Furthermore, the method for calculating the thermal resistance of the gasifier material and the efficiency η of the fins is as follows: calculate the thermal resistance of the gasifier material according to the heat conduction formula, and calculate the efficiency η of the fins according to the heat exchanger fin efficiency formula.

[0027] Furthermore, the step of verifying the required heat exchange areas of the subcooled zone, vaporization zone, and heating zone based on the pre-designed tube layout is as follows:

[0028] Calculate the medium flow rate in the subcooled zone, vaporization zone, and heating zone based on the pre-designed tube layout, and determine the medium fluid state;

[0029] Based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, the required heat transfer area for the subcooled section, the vaporization section, and the subcooled section is calculated, which is the verification value.

[0030] Furthermore, when the calculated value does not exceed or is less than 10% of the heat exchange area value of the designed tube-side layout, and the heat exchange area value of the designed tube-side layout is greater than the calculated value, the proportion of heat exchange area in the vaporizer with a surface temperature higher than the dew point temperature is calculated after adding the heat exchange area to the calculated value.

[0031] Furthermore, the method for calculating the proportion of heat exchange area in the vaporizer whose surface temperature is higher than the dew point temperature includes the following steps:

[0032] Calculate the surface temperatures of the subcooled zone, vaporization zone, and heating zone based on the heat transfer coefficient determined by the verification value, and find the zone where the surface temperature is higher than the dew point temperature.

[0033] Using an exhaustive method, the proportion of heat transfer area with a surface temperature higher than the dew point temperature is derived.

[0034] The heat exchange area above the dew point temperature is separated out and a safety factor is increased to form the first vaporizer, while the remaining heat exchange area is located in the vaporizer.

[0035] The first vaporizer and the second vaporizer are connected in series, and the second vaporizer is located upstream of the first vaporizer according to the flow direction of the medium fluid.

[0036] Furthermore, the redesigned tube layout is recalculated until the calculated value does not exceed or fall below 10% of the heat exchange area of ​​the designed tube layout.

[0037] The technical solution provided by this invention may include the following beneficial effects:

[0038] In the method of this invention, the pre-planned tube layout is verified, and the verification result is adapted to the desired production scale. The verification result, combined with the dew point temperature of the local environment, calculates the proportion of heat exchange area where the surface temperature is higher than the dew point temperature. This heat exchange area is located in the first vaporizer, while the remaining heat exchange area is located in the second vaporizer. This ensures that the first vaporizer does not frost or frosts very little during operation and can remain in operation without shutdown. Therefore, the heating range of the two parallel second vaporizers is reduced. The second vaporizer only needs to have a subcooling section and a vaporization section, which can greatly reduce the volume of the entire vaporization equipment.

[0039] The method of this invention for designing the heat exchange zone of an ambient air vaporizer has high reliability. Attached Figure Description

[0040] Figure 1 This is a flowchart of a heat exchange zone design method for an ambient air vaporizer according to an embodiment of the present invention. Detailed Implementation

[0041] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] In the description of this invention, features defined as "first" and "second" may explicitly or implicitly include one or more of the features, used to distinguish and describe features, without any order or importance.

[0043] In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] The following is combined Figure 1 This invention describes a method for designing the heat exchange zone of an ambient air vaporizer according to an embodiment of the present invention.

[0045] like Figure 1 As shown, the present invention provides a method for designing the heat exchange zone of an ambient air vaporizer, comprising the following steps:

[0046] Based on the site area and medium flow rate, the arrangement and quantity of the vaporizer tubes are designed in advance;

[0047] The medium flow rate in the subcooled zone, vaporization zone, and heating zone is calculated based on the arrangement and number of tubes to determine the medium fluid state. Specifically, the chemical flow rate calculation formula and Reynolds formula are used for the calculation.

[0048] Based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, calculate the required heat transfer area for the subcooled section, the vaporization section, and the subcooled section.

[0049] The heat exchange tube heights of the subcooling zone, vaporization zone, and heating zone are deduced from the heat exchange area to obtain the pre-designed tube layout;

[0050] Based on the pre-designed tube layout, calculations are performed to obtain the required heat exchange areas for the subcooled zone, vaporization zone, and heating zone.

[0051] Based on the calculation values, the proportion of heat exchange area in the vaporizer whose surface temperature is higher than the dew point temperature is determined. This heat exchange area with a surface temperature higher than the dew point temperature is separated and located in the first vaporizer, while the remaining heat exchange area is located in the second vaporizer.

[0052] If the calculated value exceeds or falls below 10% of the heat exchange area of ​​the designed tube layout, the tube layout should be redesigned.

[0053] In the method of this invention, the pre-planned tube layout is verified, and the verification result is adapted to the desired production scale. The verification result, combined with the dew point temperature of the local environment, calculates the proportion of heat exchange area where the surface temperature is higher than the dew point temperature. This heat exchange area is located in the first vaporizer, while the remaining heat exchange area is located in the second vaporizer. This ensures that the first vaporizer does not frost or frosts very little during operation and can remain in operation without shutdown. Therefore, the heating range of the two parallel second vaporizers is reduced. The second vaporizer only needs to have a subcooling section and a vaporization section, which can greatly reduce the volume of the entire vaporization equipment.

[0054] In the method of this invention, to ensure that the first vaporizer does not frost or frosts minimally during operation, it is necessary to ensure that the average surface temperature of the first vaporizer is not lower than or close to the dew point temperature of the operating environment. This requires precise calculation of the heat exchange capacity of the second vaporizer at the front end. This invention, by adding a verification process, ensures that the temperature of the medium fluid discharged from the second vaporizer is not too low, thereby ensuring that the overall surface temperature of the first vaporizer is not too low. The method of this invention for designing the heat exchange zone of an ambient air vaporizer offers high reliability.

[0055] It should be noted that the method of the present invention is a heat exchange zone design method. In actual use, the ambient temperature, ambient air flow and climate affect the heat exchange capacity of the air-cooled vaporizer, which also fluctuates to a certain extent. The present invention is based on the site footprint and medium flow rate for preliminary design. Therefore, the deviation between the calculated value and the design value is within 10% to ensure normal production.

[0056] To further explain, the steps for calculating the required heat transfer areas for the subcooled section, vaporization section, and subcooled section of the second vaporizer, based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, are as follows:

[0057] Calculate the relative temperature difference t between the external temperature and the medium on each surface of the vaporizer;

[0058] Calculate the surface heat transfer coefficient W1 between the outside air and the vaporizer;

[0059] Calculate the thermal resistance of the vaporizer material and the efficiency η of the fins;

[0060] Calculate the heat transfer coefficient W2 of the medium fluid in the subcooled zone, vaporization zone, and heating zone;

[0061] Calculate the thermal resistance R of the vaporizer after prolonged use due to the accumulation of dirt.

[0062] Calculate the required heat exchange area for the subcooled zone, vaporization zone, and heating zone based on t, W1, η, W2, and R.

[0063] The above-mentioned technical method provides a more accurate estimate of the required heat exchange area for each zone. Specifically, the method for calculating the relative temperature difference t between the external temperature and the medium on each surface of the vaporizer in the second vaporizer is as follows:

[0064] The calculation formula is selected based on the state of the medium fluid. When the medium fluid is in liquid or gas state, the arithmetic mean temperature difference formula is used, and when the medium fluid is in a gas-liquid mixed state, the logarithmic mean temperature difference formula is used.

[0065] Based on the temperature difference formula above, and considering the co-current and counter-current flow of the medium fluid and the external air fluid, the relative temperature difference t on the surface of the vaporizer is calculated.

[0066] Specifically, the method for setting the heat transfer coefficient W1 between the outside air and the surface of the vaporizer in the second vaporizer is as follows: first, set an empirical value, and then correct it during the verification.

[0067] Specifically, the method for calculating the thermal resistance of the gasifier material and the efficiency η of the fins in the second gasifier is as follows: calculate the thermal resistance of the gasifier material according to the heat conduction formula, and calculate the efficiency η of the fins according to the heat exchanger fin efficiency formula.

[0068] To further explain, the steps for calculating the required heat exchange areas of the subcooling zone, vaporization zone, and heating zone for the second vaporizer, based on the pre-designed tube layout, are as follows:

[0069] Calculate the medium flow rate in the subcooled zone, vaporization zone, and heating zone based on the pre-designed tube layout, and determine the medium fluid state;

[0070] Based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, the required heat transfer area for the subcooled section, the vaporization section, and the subcooled section is calculated, which is the verification value.

[0071] It should be noted that this verification process is consistent with the process of calculating the heat exchange area of ​​each zone during the design phase, which ensures that the formulas and parameters used in the two calculation processes remain consistent.

[0072] To further explain, when the calculated value of the second vaporizer does not exceed or fall below 10% of the heat exchange area of ​​the designed tube-side layout, and the designed heat exchange area of ​​the second vaporizer is greater than the calculated value, the proportion of heat exchange area in the vaporizer with a surface temperature higher than the dew point temperature is calculated after increasing the calculated value of the second vaporizer. Therefore, when the pre-designed value is greater than the calculated value, and the difference between the two is less than 10% of the design value, the calculated value is increased before calculating the heat exchange area of ​​the first vaporizer. This further ensures that the first vaporizer does not frost during operation.

[0073] To further explain, the calculation method for the proportion of heat exchange area in the second vaporizer whose surface temperature is higher than the dew point temperature includes the following steps:

[0074] Calculate the surface temperatures of the subcooled zone, vaporization zone, and heating zone based on the heat transfer coefficient determined by the verification value, and find the zone where the surface temperature is higher than the dew point temperature.

[0075] Using an exhaustive method, the proportion of heat transfer area with a surface temperature higher than the dew point temperature is derived.

[0076] The heat exchange area above the dew point temperature is separated out and a safety factor is increased to form the first vaporizer, while the remaining heat exchange area is located in the vaporizer.

[0077] The second vaporizer is connected in series with the first vaporizer, and is located upstream of the first vaporizer according to the flow direction of the medium fluid.

[0078] The calculation method for the heat exchange area of ​​the first gasifier is more reliable, ensuring that the first gasifier can work continuously under rated workload.

[0079] To further explain, the second vaporizer was redesigned and the tube-side layout was recalculated until the calculated value did not exceed or fall below 10% of the heat exchange area of ​​the designed tube-side layout.

[0080] Other configurations and operations of the heat exchange zone design method for an ambient air vaporizer according to an embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0081] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0082] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for designing the heat exchange zone of an ambient air vaporizer, characterized in that, Includes the following steps: Based on the site area and medium flow rate, the arrangement and quantity of the vaporizer tubes are designed in advance; Calculate the medium flow rate in the subcooled zone, vaporization zone, and heating zone based on the arrangement and number of tubes, and determine the medium fluid state; Based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer, calculate the required heat transfer area for the subcooled section, the vaporization section, and the subcooled section. The heat exchange tube heights of the subcooling zone, vaporization zone, and heating zone are deduced from the heat exchange area to obtain the pre-designed tube layout; Based on the pre-designed tube layout, calculations are performed to obtain the required heat exchange areas for the subcooled zone, vaporization zone, and heating zone. Based on the calculation values, the proportion of heat exchange area in the vaporizer whose surface temperature is higher than the dew point temperature is determined. This heat exchange area with a surface temperature higher than the dew point temperature is separated and located in the first vaporizer, while the remaining heat exchange area is located in the second vaporizer. If the calculated value exceeds or falls below 10% of the heat exchange area of ​​the designed tube layout, the tube layout should be redesigned.

2. The heat exchange zone design method for an ambient air vaporizer according to claim 1, characterized in that, The steps for calculating the required heat transfer area of ​​the subcooled section, vaporization section, and subcooled section based on the temperature difference between the medium and the vaporizer surface, the heat transfer coefficient of the medium, and the heat transfer performance of the vaporizer are as follows: Calculate the relative temperature difference t between the external temperature and the medium on each surface of the vaporizer; Calculate the surface heat transfer coefficient W1 between the outside air and the vaporizer; Calculate the thermal resistance of the vaporizer material and the efficiency η of the fins; Calculate the heat transfer coefficient W2 of the medium fluid in the subcooled zone, vaporization zone, and heating zone; Calculate the thermal resistance R of the vaporizer after prolonged use due to the accumulation of dirt. Calculate the required heat exchange area for the subcooled zone, vaporization zone, and heating zone based on t, W1, η, W2, and R.

3. The heat exchange zone design method for an ambient air vaporizer according to claim 2, characterized in that, The method for calculating the relative temperature difference t between the external temperature and the medium on various surfaces of the vaporizer is as follows: The calculation formula is selected based on the state of the medium fluid. When the medium fluid is in liquid or gas state, the arithmetic mean temperature difference formula is used, and when the medium fluid is in a gas-liquid mixed state, the logarithmic mean temperature difference formula is used. Based on the temperature difference formula above, and considering the co-current and counter-current flow of the medium fluid and the external air fluid, the relative temperature difference t on the surface of the vaporizer is calculated.

4. The heat exchange zone design method for an ambient air vaporizer according to claim 2, characterized in that, The method for determining the heat transfer coefficient W1 between the outside air and the surface of the vaporizer is as follows: first, an empirical value is set, and then it is corrected during the verification.

5. The heat exchange zone design method for an ambient air vaporizer according to claim 2, characterized in that, The method for calculating the thermal resistance of the gasifier material and the efficiency η of the fins is as follows: calculate the thermal resistance of the gasifier material according to the heat conduction formula, and calculate the efficiency η of the fins according to the heat exchanger fin efficiency formula.

6. The heat exchange zone design method for an ambient air vaporizer according to claim 1, characterized in that, When the calculated value is not greater than or less than 10% of the heat exchange area value of the designed tube-side layout, and the heat exchange area value of the designed tube-side layout is greater than the calculated value, the proportion of heat exchange area in the vaporizer with a surface temperature higher than the dew point temperature is calculated after adding the heat exchange area to the calculated value.

7. The heat exchange zone design method for an ambient air vaporizer according to claim 1, characterized in that, The method for calculating the proportion of heat exchange area in the vaporizer whose surface temperature is higher than the dew point temperature includes the following steps: Calculate the surface temperatures of the subcooled zone, vaporization zone, and heating zone based on the heat transfer coefficient determined by the verification value, and find the zone where the surface temperature is higher than the dew point temperature. Using an exhaustive method, the proportion of heat transfer area with a surface temperature higher than the dew point temperature is derived. The heat exchange area above the dew point temperature is separated out and a safety factor is increased to form the first vaporizer, while the remaining heat exchange area is located in the vaporizer. The first vaporizer and the second vaporizer are connected in series, and the second vaporizer is located upstream of the first vaporizer according to the flow direction of the medium fluid.

8. The heat exchange zone design method for an ambient air vaporizer according to claim 1, characterized in that, The redesigned tube layout is recalculated until the calculated value does not exceed or fall below 10% of the heat exchange area of ​​the designed tube layout.

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