A multi-stage heat recovery process design method and heat exchanger based on average temperature difference

Abstract

The present invention discloses a multi-stage heat recovery process design method based on average temperature difference and a heat exchanger, which obtains the cold side parameter value of the cold side component of the #imgabs0# section, obtains the hot side parameter value of the hot side component, calculates the relative temperature rise of each section of the cold side component and arranges them; calculates the cold side heat exchange capacity of each section of the cold side component, calculates the thermal mass temperature of the position corresponding to the outlet of each section of the cold side component in the hot side component, calculates the average temperature difference of the heat exchange logistics of the #imgabs1# section, and calculates the heat exchange area of ​​the heat exchange logistics of the #imgabs2# section; determines the length, width and cold side joint width of the heat exchanger, and forms a multi-stage heat recovery arrangement scheme; the present invention arranges multiple cold side components and one hot side component, and arranges the cold side heat exchange logistics along the process, so that the heat recovery of multiple cold side components can be achieved through one hot side component, thereby improving the compactness.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and in particular to a multi-stage heat recovery process design method based on average temperature difference and a heat exchanger. Background Art

[0002] Heat exchangers are general process equipment for allocating energy between different logistics and completing heat transfer. They are widely used in a large number of industries such as power generation, chemical industry, power, metallurgy, etc., especially in power circulation systems with supercritical carbon dioxide as the working fluid. Heat exchangers play an important role in transferring and allocating energy between working fluids.

[0003] With the continuous improvement of science and technology, people pay more and more attention to the special application scenarios of power systems involving nuclear power plants, thermal power plants, and aircraft engines. Reducing the size of equipment, improving efficiency, and reducing equipment manufacturing and operating costs and natural resource consumption are one of the future development directions of heat exchangers.

[0004] Most of the printed circuit board heat exchangers currently in use are only used to achieve heat exchange between two fluids. However, in actual industrial application scenarios, there are a large number of demands for heat exchange between multiple working fluids. At present, one heat exchange demand requires the configuration of a heat exchanger, which makes the system complicated. For example, the recompression cycle arrangement in the supercritical carbon dioxide Brayton power conversion system has two heat exchange processes, high-temperature heat recovery and low-temperature heat recovery. If two heat exchangers are designed and developed according to conventional ideas, the system volume will increase a lot, which adds a lot of difficulty to the system layout. Summary of the invention

[0005] The technical problem to be solved by the present invention is that multi-stage heat exchange logistics cannot be compacted. The purpose is to provide a multi-stage heat recovery process design method and heat exchanger based on average temperature difference, which can realize heat exchange of multiple stages of logistics at the same time.

[0006] The present invention is achieved through the following technical solutions:

[0007] A multi-stage heat recovery process design method based on average temperature difference includes the following steps:

[0008] Get The cold side parameter values ​​of the cold side components of the first Inlet temperature of cold side components , No. Outlet temperature of cold side components , ;

[0009] Get the hot side parameter value of the hot side component, which includes the inlet temperature of the hot side component , outlet temperature of hot side components and mass flow ;

[0010] Calculate the Relative temperature rise of cold side components , and sort them from large to small according to relative temperature rise;

[0011] The cold side component with the largest relative temperature rise corresponds to the inlet end of the hot side component, and the cold side component with the smallest relative temperature rise corresponds to the outlet end of the hot side component;

[0012] Calculate the The heat transfer rate of the cold side components of the segment, ,in, For the The specific heat capacity of the cold mass, For the Mass flow rate of working fluid in cold side components of the section;

[0013] Calculate the hot side components and The heat mass temperature at the outlet of the cold side component ;

[0014] calculate Average temperature difference of heat exchange flow ;

[0015] Calculated Heat exchange area of ​​heat exchange flow section ;

[0016] Obtain the flow length on the hot side based on the heat transfer area And the total length of heat exchange ;

[0017] Calculate and obtain the flow channel width of the cold side component;

[0018] Determine the length, width, and cold side component flow channel width of the heat exchanger to form a multi-stage heat recovery layout plan.

[0019] Specifically, the calculation method of thermal mass temperature includes:

[0020] Get the hot side heat transfer value of the hot side component. ,in, is the specific heat capacity of the cold mass, is the mass flow rate of the cold mass, For the The heat mass temperature at the outlet of the cold side component of the segment;

[0021] According to the law of conservation of energy, ,by or As the starting point, find the heat mass temperature of all corresponding positions .

[0022] Specifically, the calculation method of the heat exchange area includes:

[0023] Get the The cold side heat exchange corresponding to the cold side components of the segment , the overall heat transfer coefficient between the cold mass and the hot mass ;

[0024] The mean temperature difference is the logarithmic mean temperature difference ,in, For the The heat mass temperature at the outlet of the cold side component of the segment;

[0025] Calculated , .

[0026] Specifically, the overall heat transfer coefficient between the cold mass and the hot mass is calculated according to The materials of the cold side components and the hot side components of the section can be obtained by referring to the heat exchanger engineering design manual.

[0027] Specifically, the calculation method of the flow length and the total heat exchange length on the hot side includes:

[0028] Determine the diameter of microchannels in hot side components , Width of hot side components , and preliminarily set the total number of microchannels in the hot side components ;

[0029] according to Calculate the flow length on the hot side ;

[0030] Determine the total heat exchange length ;

[0031] Determine the flow area of ​​the hot side components , flow rate , the pressure drop along the hot side components ,in, is the friction coefficient of the thermal mass, is the thermal mass density;

[0032] Calculate the delayed pressure drop. If the pressure drop along the path exceeds the allowable pressure drop, increase the total number of microchannels. , reduce flow rate , iterate until the allowable pressure drop requirement is met and obtain the final total heat exchange length and flow length .

[0033] Specifically, the flow channel width of the cold side component is calculated:

[0034] The microchannel of the cold side component is divided into an inlet and outlet section and a heat exchange section, and the width of the inlet and outlet section is set to , the width of the heat exchange section is equal to the width of the hot side component ;

[0035] Initial setup ,in, is the relative temperature rise;

[0036] Calculate the Pressure drop along the cold side of the segment ,in, is the friction coefficient of the cold mass, is the cold mass density, is the flow rate of the cold mass, is the diameter of the microchannel in the cold side component;

[0037] Will and Substitute the manual formula for fluid resistance to calculate the local pressure drop ;

[0038] Sure Whether the total pressure drop requirement is met, if exceeded, increase , iterate until the total pressure drop requirement is met, and obtain the final channel width of the cold side component .

[0039] Optionally, the mean temperature difference also includes: geometric mean temperature difference and the algebraic mean temperature difference .

[0040] Optionally, Replace the cold side assembly of the section with a cold side assembly of the section, and replace the hot side assembly of the section with Section hot side components.

[0041] A multi-stage heat recovery heat exchanger based on average temperature difference, based on a multi-stage heat recovery process design method based on average temperature difference as described in any of the above items, the heat exchanger includes a cold side module and a hot side component, multiple cold side modules and multiple hot side components are repeatedly stacked in the height direction, and the heat exchange direction of the heat exchanger is perpendicular to the flow direction of the cold mass in the cold side module, and is also perpendicular to the flow direction of the hot mass in the hot side component.

[0042] Optionally, the cold side module includes Cold side components, The cold side components of the sections are located in the same horizontal plane and are fitted one by one.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] The present invention arranges multiple cold side components and one hot side component and arranges the cold side heat exchange logistics along the process, so that heat recovery of multiple cold side components can be achieved through one hot side component, thereby improving the compactness. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, are used to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention, and the accompanying drawings are included in and constitute a part of this specification and do not constitute a limitation of the embodiments of the present invention.

[0046] Figure 1 It is a structural schematic diagram of a multi-stage heat recovery exchanger based on average temperature difference according to the present invention.

[0047] Figure 2 It is a flow chart of a multi-stage heat recovery process design method based on average temperature difference according to the present invention.

[0048] Figure 3 It is a schematic diagram of the flow chart of the flow heat transfer verification calculation according to the present invention. DETAILED DESCRIPTION

[0049] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present invention.

[0050] It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the drawings.

[0051] In the absence of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] Embodiment 1

[0053] like Figure 2 As shown in the figure, a multi-stage heat recovery process design method based on average temperature difference includes the following four steps:

[0054] The first step is to input the parameters of multi-stage heat exchange logistics.

[0055] Get The cold side parameter values ​​of the cold side components of the first Inlet temperature of cold side components , No. Outlet temperature of cold side components , .

[0056] Get the hot side parameter value of the hot side component, which includes the inlet temperature of the hot side component , outlet temperature of hot side components and mass flow .

[0057] The cold side assembly includes a cold side flow channel plate and a cold side flow channel arranged in the cold side flow channel plate, and the hot side assembly includes a hot side flow channel plate and a hot side flow channel arranged in the hot side flow channel plate.

[0058] The cold side flow channel and the hot side flow channel are repeatedly stacked in the height direction, that is, the cold side working fluid and the hot side working fluid exchange heat in the direction perpendicular to the flow during the flow process.

[0059] The second step is to sort the cold side heat exchange logistics along the process.

[0060] Introducing dimensionless parameters, that is, calculating the relative temperature rise of each cold side component , and sort them from large to small according to relative temperature rise.

[0061] The cold side component with the largest relative temperature rise is matched with the inlet end of the hot side component, because the cold side component requires the largest heating power, the average temperature of the inlet end of the hot side component is high, and the temperature difference with the cold side component is large. Similarly, the cold side component with the smallest relative temperature rise is matched with the outlet end of the hot side component.

[0062] The third step is Figure 3 As shown, flow heat transfer verification calculation.

[0063] Calculate the cold side heat transfer of each cold side component. ,in, For the The specific heat capacity of the cold mass, For the The mass flow rate of the working fluid in the cold side components of the section.

[0064] Then, according to the law of energy conservation, the heat mass temperature at the corresponding position of the outlet of each section of the cold side component in the hot side component is calculated. ; The method comprises: obtaining the heat exchange amount of the hot side component of the hot side, ,in, is the specific heat capacity of the cold mass, is the mass flow rate of the cold mass; according to the law of conservation of energy, ,by or As the starting point, find the heat mass temperature of all corresponding positions .

[0065] calculate Average temperature difference of heat exchange flow ; Mean temperature difference includes: logarithmic mean temperature difference

[0066] , geometric mean temperature difference and the algebraic mean temperature difference In this embodiment, the logarithmic mean temperature difference is selected.

[0067] according to Calculated Heat exchange area of ​​heat exchange flow section ; The calculation method includes: obtaining the The cold side heat exchange corresponding to the cold side components of the segment , mean temperature difference , the overall heat transfer coefficient between the cold mass and the hot mass , the overall heat transfer coefficient between the cold mass and the hot mass It is obtained by referring to the heat exchanger engineering design manual based on the material types of the cold side components and the hot side components of section k.

[0068] Obtain the flow length on the hot side based on the heat transfer area And the total length of heat exchange ; The specific methods include: The calculation methods of the flow length of the hot side and the total heat exchange length include:

[0069] Determine the diameter of microchannels in hot side components (Based on the current experience of microchannel processing technology for this type of heat exchanger, the microchannel of the hot side component is selected as a semicircular microchannel with a diameter of d=1-4mm) , and preliminarily set the total number of microchannels in the hot side components based on the design experience of this type of heat exchanger ;

[0070] according to Calculate the flow length on the hot side ;

[0071] Determine the total heat exchange length ;

[0072] Determine the flow area of ​​the hot side components , flow rate , the pressure drop along the hot side components ,in, is the friction coefficient of the thermal mass (obtained from the fluid resistance manual), is the thermal mass density.

[0073] Calculate the delayed pressure drop. If the pressure drop along the path exceeds the allowable pressure drop, increase the total number of microchannels. , reduce flow rate , iterate until the allowable pressure drop requirement is met and obtain the final total heat exchange length and flow length .

[0074] The flow channel width of the cold side component is calculated; the specific method includes: dividing the microchannel of the cold side component into an inlet and outlet section and a heat exchange section, and setting the width of the inlet and outlet section to , the width of the heat exchange section is equal to the width of the hot side component Therefore, when the working fluid of the cold side component flows through the heat exchanger, a sudden change in the flow area will produce a local pressure drop, which is a sudden expansion pressure drop and a sudden contraction pressure drop. is related to the ratio.

[0075] According to the process design experience of this type of heat exchanger, the initial setting ,in, is the relative temperature rise.

[0076] Taking into account the different temperature rise conditions of different cold side components and the different requirements for the flow channel width of the cold side components, it is now necessary to check whether the sum of the along-the-line pressure drop and the local pressure drop of the cold side component in the kth section meets the design allowable pressure drop requirements.

[0077] The calculation formula for the pressure drop of cold mass along the path is similar to that of hot mass along the path. Pressure drop along the cold side of the segment ,in, is the friction coefficient of the cold mass, is the cold mass density, is the flow rate of the cold mass, is the diameter of the microchannel in the cold side component;

[0078] Will and Substitute the manual formula for fluid resistance to calculate the local pressure drop ;

[0079] Sure Whether the total pressure drop requirement is met, if exceeded, increase (Close to ), iterate until the total pressure drop requirement is met, and obtain the final channel width of the cold side component .

[0080] The fourth step is to establish a multi-stage heat recovery layout plan.

[0081] According to step 3, determine the length of the heat exchanger ,width , Cold side joint width Etc., to form a multi-stage heat recovery arrangement plan.

[0082] The semi-empirical relationship used to calculate the convective heat transfer coefficient includes but is not limited to the DB relationship and other relationships.

[0083] Will Replace the cold side assembly of the section with a cold side assembly of the section, and replace the hot side assembly of the section with The hot side components can achieve the purpose of multi-stage cooling.

[0084] Embodiment 2

[0085] Based on a multi-stage heat recovery process design method based on average temperature difference in Example 1, Figure 1 As shown, a multi-stage heat recovery heat exchanger based on average temperature difference is provided, the heat exchanger includes a cold side module 1 and a hot side component 2, multiple cold side modules 1 and multiple hot side components 2 are repeatedly stacked in the height direction, and the heat exchange direction of the heat exchanger is perpendicular to the flow direction of the cold mass in the cold side module, and is also perpendicular to the flow direction of the hot mass in the hot side component.

[0086] Cold side module 1 includes Cold side components, The cold side components of the sections are located on the same horizontal plane and are fitted one after another.

[0087] Figure 1 middle, , ,……, Respectively refer to the first section cold side components, the second section cold side components, ..., the Cold side components of the segment.

[0088] Figure 1 In , ,……, Respectively refer to the first section hot side components, the second section hot side components, ..., the Section hot side components.

[0089] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0090] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0091] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above invention, and these changes or modifications are still within the scope of the present invention.

Claims

1. A multi-stage heat recovery process design method based on average temperature difference, characterized in that: The following steps are involved: Get The cold side parameter values ​​of the cold side components of the first Inlet temperature of cold side components , No. Outlet temperature of cold side components , ; Get the hot side parameter value of the hot side component, which includes the inlet temperature of the hot side component , the outlet temperature of the hot side component and mass flow ; Calculate the Relative temperature rise of cold side components , and sort them from large to small according to relative temperature rise; The cold side component with the largest relative temperature rise corresponds to the inlet end of the hot side component, and the cold side component with the smallest relative temperature rise corresponds to the outlet end of the hot side component; Calculate the The heat transfer rate of the cold side components of the segment, ,in, For the The specific heat capacity of the cold mass, For the Mass flow rate of working fluid in cold side components of the section; Calculate the hot side components and The heat mass temperature at the outlet of the cold side component ; calculate Average temperature difference of heat exchange flow ; Calculated Heat exchange area of ​​heat exchange flow section ; Obtain the flow length on the hot side based on the heat transfer area And the total length of heat exchange ; Calculate and obtain the flow channel width of the cold side component; Determine the length, width, and cold side component flow channel width of the heat exchanger to form a multi-stage heat recovery layout plan.

2. The multi-stage heat recovery process design method based on average temperature difference according to claim 1 is characterized in that: The calculation methods of thermal mass temperature include: Get the hot side heat transfer value of the hot side component. ,in, is the specific heat capacity of the cold mass, is the mass flow rate of the cold mass, For the The heat mass temperature at the outlet of the cold side component of the segment; According to the law of conservation of energy, ,by or As the starting point, find the heat mass temperature of all corresponding positions .

3. The multi-stage heat recovery process design method based on average temperature difference according to claim 1 is characterized in that: The calculation methods of heat exchange area include: Get the The cold side heat exchange corresponding to the cold side components of the segment , the overall heat transfer coefficient between the cold mass and the hot mass ; The mean temperature difference is the logarithmic mean temperature difference ,in, For the The heat mass temperature at the outlet of the cold side component of the segment; Calculated , .

4. The multi-stage heat recovery process design method based on average temperature difference according to claim 3 is characterized in that: The overall heat transfer coefficient between the cold mass and the hot mass is given by The materials of the cold side components and the hot side components of the section can be obtained by referring to the heat exchanger engineering design manual.

5. The multi-stage heat recovery process design method based on average temperature difference according to claim 1 is characterized in that: The calculation method of the flow length and the total heat exchange length on the hot side includes: Determine the diameter of microchannels in hot side components , Width of hot side components , and preliminarily set the total number of microchannels in the hot side components ; according to Calculate the flow length on the hot side ; Determine the total heat exchange length ; Determine the flow area of ​​the hot side components , flow rate , the pressure drop along the hot side components ,in, is the friction coefficient of the thermal mass, is the thermal mass density; Calculate the delayed pressure drop. If the pressure drop along the path exceeds the allowable pressure drop, increase the total number of microchannels. , reduce flow rate , iterate until the allowable pressure drop requirement is met and obtain the final total heat exchange length and flow length .

6. The multi-stage heat recovery process design method based on average temperature difference according to claim 5, characterized in that: Calculate the channel width of the cold side component: The microchannel of the cold side component is divided into an inlet and outlet section and a heat exchange section, and the width of the inlet and outlet section is set to , the width of the heat exchange section is equal to the width of the hot side component ; Initial setup ,in, is the relative temperature rise; Calculate the Pressure drop along the cold side of the segment ,in, is the friction coefficient of the cold mass, is the cold mass density, is the flow rate of the cold mass, is the diameter of the microchannel in the cold side component; Will and Substitute the manual formula for fluid resistance to calculate the local pressure drop ; Sure Whether the total pressure drop requirement is met, if exceeded, increase , iterate until the total pressure drop requirement is met, and obtain the final channel width of the cold side component .

7. The multi-stage heat recovery process design method based on average temperature difference according to claim 3 is characterized in that: The mean temperature difference also includes: geometric mean temperature difference and the algebraic mean temperature difference .

8. The multi-stage heat recovery process design method based on average temperature difference according to claim 1 is characterized in that: Will Replace the cold side assembly of the section with a cold side assembly of the section, and replace the hot side assembly of the section with Section hot side components.

9. A multi-stage heat recovery exchanger based on average temperature difference, characterized in that: Based on a multi-stage heat recovery process design method based on average temperature difference as described in any one of claims 1-7, the heat exchanger includes a cold side module and a hot side component, multiple cold side modules and multiple hot side components are repeatedly stacked in the height direction, and the heat exchange direction of the heat exchanger is perpendicular to the flow direction of the cold mass in the cold side module, and is also perpendicular to the flow direction of the hot mass in the hot side component.

10. The multi-stage heat recovery exchanger based on average temperature difference according to claim 9, characterized in that: The cold side module includes Cold side components, The cold side components of the sections are located in the same horizontal plane and are fitted one by one.

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