Method for calculating width of buffer area of high-precision temperature control clean room

Abstract

The invention discloses a method for calculating the width of a buffer area of a high-precision temperature control clean room, and provides a certain reference for calculation and implementation of the width of the buffer area for the clean room with a high-precision temperature control requirement. The method comprises the following operations. 1, establishing a clean room physical model; 2, the heat transfer process is simplified; and 3, a step-by-step calculation process. The invention has the following advantages: the calorific value of the core area of the clean room is basically stable, and the density of heat flow entering the inner surface of the wall surface (1) is qn1; the outer area of the wall surface (4) is generally outdoor or other rooms, the density of heat flow borne by the outer surface is qn4, and the temperature of the outer surface is equal to the temperature of the external environment; the external area (the upper technical interlayer) of the wall surface (5) has no equipment or other internal disturbance factors, and the temperature of the external surface is equal to that of the upper technical interlayer; the air in the air return passageway is subjected to sufficient heat exchange indoors, and the temperature of the air in the air return passageway reaches the indoor set temperature; and the temperature t1 of the inner surface of the clean wall plate in the core area is maintained within the indoor temperature required range, and t1min < = t1max < = t1max.

Description

Technical Field

[0001] The present invention relates to the field of cleanroom design, and more specifically to a method for determining the width of a buffer zone during the design of a cleanroom with extremely high requirements for indoor temperature accuracy. Background Art

[0002] With the continuous improvement of China's comprehensive national strength and the rapid progress of science and technology, intelligence and informatization have become the development trends of today's society. Against this background, the semiconductor industry, as the cornerstone of modern industry, has become increasingly important. Semiconductor production mainly includes three major processes: design, manufacturing, and packaging and testing. Due to the extremely high fineness of semiconductor products, any tiny dust or pollutant may cause product defects, thereby affecting the performance and reliability of the final product. In addition, minor temperature fluctuations may also have a significant impact on the manufacturing process, resulting in changes in material properties or a decrease in equipment accuracy. Therefore, in the manufacturing and packaging and testing links, the requirements for the production environment are extremely strict, and it is necessary to ensure a high degree of cleanliness, stable temperature and humidity control, and strict dust and pollution prevention measures.

[0003] The "Code for Design of Cleanrooms" GB 50073-2013 stipulates that for cleanrooms with temperature and humidity requirements in the production process, the indoor temperature and humidity should be determined according to the production process requirements. The "Code for Architectural Design of Industrial Buildings in the Machinery Industry" GB50681-2011 stipulates that air-conditioning areas with a room temperature allowable fluctuation of -0.1°C to 0.2°C should be arranged on the ground floor, should not have exterior walls and roofs, and an air-conditioning area or suite with a room temperature allowable fluctuation of ±1.0°C should be arranged around it. Thus, it can be seen that if the indoor temperature fluctuation is to be controlled within a very small range, a "suite" (or buffer zone) needs to be set outside the core cleanroom, and the temperature control accuracy of the buffer zone can be appropriately reduced.

[0004] In recent years, with the rise of the chip industry, there have been more and more cleanrooms with high-precision temperature control requirements. However, the current specifications in China only make requirements for the architectural layout of cleanrooms and do not give the width requirements or calculation methods for "suites". This has led to the situation that during the design process, designers often can only determine the width of the "suite" based on personal experience or the process conditions provided by the owner. When the designed width is too large, the space inside the "suite" is large enough, and the influence of external disturbances on the environment inside the "suite" can be eliminated by the air-conditioning system in a timely manner, and almost no impact will be caused to the core area. However, this will reduce the space utilization rate and increase the investment. If the designed size is too small, the space inside the "suite" is too small to eliminate the influence caused by external disturbances in a timely manner, which will lead to an increase in the temperature fluctuation in the core area and affect the normal progress of related processes. Therefore, while ensuring that the core area is not affected, the designed width should be minimized as much as possible.

[0005] This width can be obtained through calculation. However, due to the complexity of the heat transfer process, strictly solving according to the calculation formula will lead to a very difficult analysis process. If the influence of the buffer zone under different widths is analyzed through CFD-related software simulation, it will consume a large amount of time and is not conducive to the development of the project. Therefore, this patent simplifies the relevant heat transfer process for the building layout of a typical high-precision temperature-controlled clean room and proposes a simple calculation method. Summary of the Invention

[0006] Therefore, to address the above deficiencies, the present invention provides a calculation method for the buffer zone width of a clean room with high-precision temperature control requirements.

[0007] The present invention is implemented as follows. A calculation method for the buffer zone width of a high-precision temperature-controlled clean room is constructed, characterized by the following operations:

[0008] 1. Establish a physical model of the clean room;

[0009] 1.1 Structural division: Core area: including upper and lower technical mezzanines and return air ducts, with a planar size of length × width = a × b and a return air duct width of c; Buffer zone: surrounding the core area in a ring, with a width of the parameter x to be determined, a return air duct width of d, and a height of H; All wall surfaces use clean wall panels (thermal conductivity λ, thickness δ, surface emissivity ε), and heat insulation measures are added to the buffer zone floor.

[0010] 1.2 Environmental assumptions:

[0011] The heat generation in the core area is stable, and the inner surface heat flux density is q n1 ;

[0012] The outer surface temperature of the buffer zone periphery (wall surface ④) is equal to the external environmental temperature t outdoor ;

[0013] The outer surface temperature of the buffer zone ceiling (wall surface ⑤) is equal to the upper technical mezzanine temperature t interlayer r;

[0014] The air temperature in the return air duct is equal to the set temperature t of the clean room n ;

[0015] 2. Simplify the heat transfer process;

[0016] 2.1 Conduction model: The length and width of each wall surface are much larger than the thickness, regarded as one-dimensional steady-state infinite large flat plate conduction, and analyzed by Fourier's law; The inner surface temperature t of the core area wall surface ① 1内 needs to meet the process requirement range: t 1min ≤t 1内 ≤t 1max ;

[0017] 2.2 Convection and Radiation Model: The inner and outer surfaces of the return air duct (wall surfaces ① to ④): The air flow distance is long, and the convection heat transfer analysis is based on a one-dimensional steady-state infinite plate convection heat transfer analysis, and the convection coefficient is calculated in combination with the Nusselt number (Nu);

[0018] Ceiling and floor (walls ⑤⑥): perpendicular to the airflow, and the return air outlet is on the side, so convection is ignored and only radiation heat transfer is considered;

[0019] Radiation heat transfer: The enclosed buffer space is equivalent to a four-surface radiation heat network model, which is solved by simultaneously solving the view factor and the effective radiation equation. The two surfaces in the return air duct space are equivalent to the radiation heat transfer of two infinitely large plates.

[0020] 3. Step-by-step calculation process;

[0021] 3.1 Core area wall ① Heat transfer analysis: Combine the heat conduction equation, convection equation and radiation equation (1)(2)(3) to derive t 1内 With adjacent wall t 2内 Temperature relationship;

[0022] 3.2 Heat transfer analysis of buffer zone wall ②~⑥:

[0023] Analyze the heat conduction, convection and radiation processes of each wall in turn and establish a set of equations;

[0024] Wall surface ②: (5)~(14);

[0025] Wall surface ③: (20)~(22);

[0026] Wall surface ④: (16)~(19);

[0027] Wall surface ⑤: (23)~(25);

[0028] Wall ⑥: The buffer zone floor has been insulated and is considered an insulating surface;

[0029] 3.3 Solve the buffer width x: Constrain the core temperature t 1min ≤t 1内 ≤t 1max Substituting into the equations, we can finally get the expression of x (26); solving for the allowable range of x: x min ≤x≤x max .

[0030] According to the method for calculating the buffer width of a high-precision temperature-controlled clean room of the present invention, the specific operation of step 1 is:

[0031] Its main structure consists of two parts: the core area and the buffer area. The core area includes the upper and lower technical mezzanines and their return air ducts, and the buffer area includes the upper technical mezzanine and its return air ducts.

[0032] The surrounding walls of the core area are denoted as wall surface ①, the outer wall surface of the return air duct in the core area is denoted as wall surface ②, the outer wall surface of the buffer area is denoted as wall surface ③, the outer wall surface of the return air duct in the buffer area is denoted as wall surface ④, the ceiling of the buffer area is denoted as wall surface ⑤, and the floor is denoted as wall surface ⑥;

[0033] Among them, the length of the core area is a, the width is b, and the width of its return air duct is c; it is assumed that the buffer area is an annular shape with equal width, the width is x, the width of its return air duct is d, and the room height is H;

[0034] Among them, all the walls forming the clean room are special clean wall panels, and additional heat insulation measures are taken for the floor of the buffer area. For the clean wall panels, their thermal conductivity is λ, the thickness is δ, and the surface emissivity is ε;

[0035] The heat flux density entering the inner surface of wall surface ① is denoted as q n1 ; The outer area of wall surface ④ is generally outdoors or other rooms. For the convenience of analysis, it is assumed that the heat flux density received by its outer surface is q n4 , and the outer surface temperature is equal to the external environment temperature, denoted as t 4外 , t 4外 =t outdoor ; The outer area of wall surface ⑤ (the upper technical mezzanine) has no equipment and other internal disturbance factors, and it can be considered that its outer surface temperature is equal to the temperature of the upper technical mezzanine, denoted as t 5外 , t 5外 =t interlayer ; The air in the return air duct has been fully heat exchanged in the room, and it can be considered that it has reached the set indoor temperature, that is, t f =t n ;

[0036] If it is necessary to ensure that the temperature of the core area meets the requirements, it is necessary to maintain the inner surface temperature t1 of the clean wall panel in the core area within the range of the indoor temperature requirements. Otherwise, the convective heat transfer and radiative heat transfer processes between it and the indoor air will affect the indoor temperature; according to the process requirements, the range of the inner surface temperature of the clean room should be t 1min ≤t 1内 ≤t 1max .

[0037] According to the calculation method of the buffer area width of a high-precision temperature-controlled clean room described in the present invention, its characteristics are as follows; the specific operation of step 3 is:

[0038] Taking the buffer area as the center, calculate this heat transfer process in the order from inside to outside; for the convenience of analysis, first calculate the inner surface temperature t of the clean room 1内 as a known parameter, and finally organize it into a relational expression about x;

[0039] 1) The heat transfer process of wall surface ① includes:

[0040] Ⅰ. Heat flux q transferred from the interior to the inner surface of wall ① n1 ;

[0041] Ⅱ. Heat conduction inside wall ①;

[0042] Ⅲ. Convective heat transfer between the outer surface of wall ① and the air in the return air duct, and radiative heat transfer with the inner surface of wall ②;

[0043] Since the heat transfer process of the wall is regarded as one-dimensional, the above three heat fluxes are equal, and thus we can obtain:

[0044]

[0045] where, t 1外 can be calculated by Equation (28), and the Nusselt number Nu 1外 can be calculated by selecting a suitable correlation formula according to the physical properties of the air and the corresponding flow conditions and then solving Equation (30) simultaneously, and then the convective heat transfer coefficient h 1外 ;

[0046] Through the above calculations, t 1内 Regarding t 2内 The relationship is obtained, that is

[0047] t 1内 = f(t 2内 ) (4)

[0048] 2) The heat transfer process of wall ② includes:

[0049] Ⅰ. Convective heat transfer between the inner surface of wall ② and the air in the return air duct, and radiative heat transfer with the outer surface of wall ①;

[0050] Ⅱ. Heat conduction inside wall ②;

[0051] Ⅲ. Convective heat transfer between the outer surface of wall ② and the air in the buffer zone, and radiative heat transfer with the inner surfaces of walls ③, ⑤, and ⑥;

[0052] Similar to wall ①, the heat fluxes of the above three heat transfer processes should be equal, and thus we can obtain:

[0053]

[0054] q2 = q h2外 + q Rad2,356 = h 2外 (t f - t 2外 ) + q Rad2,356 (8)

[0055]

[0056] q Rad2,356 = J 2外 (10)

[0057]

[0058] Similar to wall surface ①, the value of t can be obtained by calculating through equations (32) and (33). 2内 The relational expression between q2 can be obtained by substituting the relational expression between q and t into equation (34). 2外 The relational expression between q2 and t can be obtained by calculating through equations (35) to (37). 2外 The relational expression between t and J 2外 That is, t 2内 = f(J 2外 ) and then we can get

[0059] t 1内 = g(J 2外 ) (15)

[0060] In equations (38) to (41), all view factors can be calculated by mathematical methods and can be expressed as relational expressions regarding the buffer width x; among the remaining seven terms of E b2外 , E b3内 , E b5内 , J 2外 , J 3内 , J 5内 , J6, E b2外 can be calculated according to the relational expression between t 2外 and J 2外 , E b3内 , E b5内 can be calculated according to the analysis of wall surfaces ③ to ⑤;

[0061] 3) The heat transfer process of wall surface ④ includes:

[0062] Ⅰ. The heat flux q n4 transferred from the external region to the outer surface of wall surface ④;

[0063] Ⅱ. The heat conduction inside wall surface ④;

[0064] Ⅲ. The convective heat transfer between the inner surface of wall surface ④ and the air in the return air duct, and the radiative heat transfer with wall surface ③;

[0065] Similar to wall surfaces ① and ②, the heat fluxes of the above three heat transfer processes should be equal, and thus we can get:

[0066] t 4外 = t outdoor (16)

[0067]

[0068] Similar to walls ① and ②, t can be obtained by calculating using equations (43) and (44). 4内 , substituting into equations (45) and (46) gives E b3外 Furthermore, t can be obtained 3外 ;

[0069] 4) The heat transfer process of wall ③ includes:

[0070] Ⅰ. Convective heat transfer between the outer surface of wall ③ and the air in the return air duct, and radiative heat transfer with wall ④;

[0071] Ⅱ. Heat conduction inside wall ③;

[0072] Ⅲ. Convective heat transfer between the inner surface of wall ③ and the air in the buffer zone, and radiative heat transfer with the outer surface of wall ② and the inner surfaces of walls ⑤ and ⑥;

[0073] Similar to walls ①, ②, and ④, the heat fluxes of the above three heat transfer processes should be equal, from which we can obtain:

[0074]

[0075]

[0076] Similar to walls ①, ②, and ④, q3 can be obtained by calculating using equations (47) and (48), substituting into equation (49) gives t 3内 and E b3内 , which can be substituted into equations (38) - (41) for calculation;

[0077] 5) The heat transfer process of wall ⑤ includes:

[0078] Ⅰ. Heat conduction inside wall ⑤;

[0079] Ⅱ. Radiative heat transfer between the inner surface of wall ⑤ and the outer surface of wall ② and the inner surfaces of walls ③ and ⑥;

[0080] Similarly, we can obtain:

[0081] t 5外 = t interlayer (23)

[0082]

[0083] q5 = q Rad5,236 = J 5内 (25)

[0084] The relationship between t 5内 and J 5内 can be obtained by calculating using equations (50) - (52), which can be substituted into equations (38) - (41) for calculation;

[0085] Through the above calculations, only J remains in equations (38) - (41).2外 , J 3内 , J 5内 , J6, x five unknowns. Taking x as a known parameter, four effective radiation relationships with respect to x can be obtained; and during the calculation process of walls ① and ②, t 1内 = g(J 2外 ) has been obtained. Then substituting the relationship of J 2外 with respect to x can obtain the relationship of t 1内 with respect to x

[0086] t 1内 = h(x) (26)

[0087] According to the process requirements, t 1min ≤ t 1内 ≤ t 1max . Thus, the range requirement of the buffer width x can be solved according to Equation (53), that is

[0088] t 1min ≤ h(x) ≤ t 1max (27)

[0089] Finally, x min ≤ x ≤ x max can be obtained, that is, the buffer width should be within this range during design.

[0090] The present invention has the following advantages: For a clean room with high-precision temperature control requirements, it provides a certain reference for the calculation of the buffer width.

[0091] 1. The heat generation in the core area of the clean room is basically stable, and the heat flux density entering the inner surface of wall ① is q n1 ;

[0092] 2. The external area of wall ④ is generally outdoors or other rooms, and the heat flux density received by its outer surface is q n4 , and the outer surface temperature is equal to the external environment temperature;

[0093] 3. There are no equipment and other internal disturbance factors in the external area (upper technical mezzanine) of wall ⑤, and its outer surface temperature is equal to the temperature of the upper technical mezzanine;

[0094] 4. The air in the return air duct has been fully heat-exchanged indoors, and its temperature has reached the indoor set temperature.

[0095] 5. The inner surface temperature t1 of the clean wall panel in the core area is maintained within the indoor temperature requirement range, t 1min ≤ t 1内 ≤ t 1max .

[0096] 6. The length and width of each wall surface in the cleanroom are much larger than the thickness. It is considered that the heat conduction process from one side of the clean wall panel to the other side is a one-dimensional steady-state heat conduction process of an infinitely large flat plate.

[0097] 7. The height of the cleanroom is generally above 4m, and the distance that the air sweeps over the surface of the clean wall panel is relatively long. The convective heat transfer process between the inner and outer surfaces of all the return air ducts and the air is regarded as the heat transfer of a one-dimensional steady-state infinitely large flat plate.

[0098] 8. Wall surfaces ⑤ and ⑥ are basically perpendicular to the air flow, and the convective heat transfer process is not obvious. The influence of convective heat transfer is ignored.

[0099] 9. The distance between the two clean wall panels of the return air duct is generally much smaller than the height of the cleanroom, and the radiation heat transfer between them is considered according to the radiation heat transfer between two parallel infinitely large flat plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 Cross-sectional view of a high-precision temperature-controlled cleanroom;

[0101] Figure 2 Plan view of a high-precision temperature-controlled cleanroom;

[0102] Figure 3 Radiation heat network diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0103] The following will combine the attached Figures 1 - 3 The present invention will be described in detail below. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0104] The present invention provides a calculation method for the buffer zone width of a high-precision temperature-controlled cleanroom herein, which provides a certain reference for the calculation and implementation of the buffer zone width for cleanrooms with high-precision temperature control requirements. The following will be described in detail with reference to the accompanying drawings. The implementation of this method is as follows:

[0105] 1. Assume a typical high-precision temperature-controlled cleanroom as an example for analysis. As Figure 1 shown, its main structure includes two parts: a core area and a buffer zone. The core area includes upper and lower technical mezzanines and their return air ducts, and the buffer zone includes an upper technical mezzanine and its return air duct.

[0106] Among them, as Figure 2As shown in the figure, the surrounding walls of the core area are denoted as wall surface ①, the outer wall surface of the return air duct in the core area is denoted as wall surface ②, the outer wall surface of the buffer area is denoted as wall surface ③, the outer wall surface of the return air duct in the buffer area is denoted as wall surface ④, the ceiling of the buffer area is denoted as wall surface ⑤, and the floor is denoted as wall surface ⑥.

[0107] Among them, the length of the core area is a, the width is b, and the width of its return air duct is c; it is assumed that the buffer area is an annular shape with equal width, the width is x, and the width of its return air duct is d. The height of the room is H.

[0108] Among them, all the walls that make up the clean room are special clean wall panels. The ground of the buffer area takes additional heat insulation measures. For the clean wall panels, their thermal conductivity is λ, the thickness is δ, and the surface emissivity is ε.

[0109] This type of clean room is generally a fully automated workshop. Therefore, the heat generation in the core area is basically stable. The heat flux density entering the inner surface of wall surface ① is denoted as q n1 ; the external area of wall surface ④ is generally outdoors or other rooms. For the convenience of analysis, it is assumed that the heat flux density received by its outer surface is q n4 , and the outer surface temperature is equal to the external environment temperature, denoted as t 4外 , t 4外 = t outdoor ; the external area (upper technical mezzanine) of wall surface ⑤ has no equipment and other internal disturbance factors, and it can be considered that its outer surface temperature is equal to the temperature of the upper technical mezzanine, denoted as t 5外 , t 5外 = t interlayer ; the air in the return air duct has been fully heat exchanged indoors, and it can be considered that it has reached the indoor set temperature, that is, t f = t n .

[0110] If the temperature of the core area is to meet the requirements, it is necessary to maintain the inner surface temperature t1 of the clean wall panels in the core area within the range of the indoor temperature requirements. Otherwise, the convective heat transfer and radiative heat transfer processes between it and the indoor air will affect the indoor temperature. According to the process requirements, the range of the inner surface temperature of the clean room should be t 1min ≤ t 1内 ≤ t 1max .

[0111] 2. For each wall surface of the clean room, its length and width are much larger than the thickness. Therefore, it can be considered that the heat conduction process from one side of the clean wall panel to the other side can be regarded as a one-dimensional steady-state heat conduction process of an infinite large flat plate.

[0112] The height of the cleanroom is generally above 4m, and the distance that air sweeps across the surface of the clean wall panels is relatively long. Therefore, the convective heat transfer process between the inner and outer surfaces (wall surfaces ① - ④) of all return air channels can be regarded as the heat transfer of a one-dimensional steady-state infinite large flat plate. Since the air-conditioning airflow in the cleanroom is mostly from top to bottom, and wall surfaces ⑤ and ⑥ are basically perpendicular to the airflow, the convective heat transfer process is not obvious, so the influence of convective heat transfer is ignored.

[0113] The distance between the two clean wall panels of the return air channel is generally much smaller than the height of the cleanroom, and the radiative heat transfer between them can be considered as that between two parallel infinite large flat plates. The buffer zone is a closed space, and when considering its radiative heat transfer, it can be equivalent to a four-surface radiative heat transfer model of a closed space, as Figure 3 shown, and the radiative heat network method can be used for analysis.

[0114] 3. Taking the buffer zone as the center, calculate this heat transfer process in the order from inside to outside. For the convenience of analysis, first take the inner surface temperature t 1内 of the cleanroom as a known parameter for calculation, and finally organize it into a relational expression about x.

[0115] 1) The heat transfer process of wall surface ① includes:

[0116] Ⅰ. The heat flux q n1 transferred from the room to the inner surface of wall surface ①;

[0117] Ⅱ. The heat conduction inside wall surface ①;

[0118] Ⅲ. The convective heat transfer between the outer surface of wall surface ① and the air in the return air channel, and the radiative heat transfer with the inner surface of wall surface ②.

[0119] Since the heat transfer process of the wall surface is regarded as one-dimensional, the above three heat fluxes are equal, and thus we can get:

[0120]

[0121] Among them, t 1外 can be calculated through formula (28), the Nusselt number Nu 1外 can be calculated by selecting an appropriate correlation formula according to the physical properties of the air and the corresponding flow conditions and combining formula (30), and then the convective heat transfer coefficient h 1外 can be obtained.

[0122] Through the above calculations, the relational expression of t 1内 about t 2内 can be obtained, that is

[0123] t 1内 = f(t 2内 ) (31)

[0124] 2) The heat transfer process of wall surface ② includes:

[0125] Ⅰ. Convective heat transfer between the inner surface of wall ② and the air in the return air duct, and radiative heat transfer with the outer surface of wall ①;

[0126] Ⅱ. Heat conduction inside wall ②;

[0127] Ⅲ. Convective heat transfer between the outer surface of wall ② and the air in the buffer zone, and radiative heat transfer with the inner surfaces of walls ③, ⑤, and ⑥;

[0128] Similar to wall ①, the heat fluxes of the above three heat transfer processes should be equal. Thus, we can obtain:

[0129]

[0130]

[0131] q2 = q h2外 +q Rad2,356 = h 2外 (t f -t 2外 )+q Rad2,356 (35)

[0132]

[0133] q Rad2,356 = J 2外 (37)

[0134]

[0135] Similar to wall ①, by calculating through equations (32) and (33), the relationship between t 2内 and q2 can be obtained. Substituting it into equation (34), the relationship between q2 and t 2外 can be obtained. Then, by calculating through equations (35) to (37), the relationship between t 2外 and J 2外 can be obtained, that is, t 2内 = f(J 2外 ). Furthermore, we can obtain

[0136] t 1内 = g(J 2外 ) (42)

[0137] In equations (38) to (41), all view factors can be calculated by mathematical methods and can be expressed as a relationship with the buffer zone width x. Among the remaining seven terms of E b2外 、E b3内 、E b5内 、J 2外 、J 3内 、J 5内 、J6, E b2外According to t 2外 With J 2外 The relationship is calculated, E b3内 、E b5内 It can be calculated based on the analysis of wall surfaces ③ to ⑤, see below for details.

[0138] 3) The heat transfer process on the wall ④ includes:

[0139] Ⅰ. Heat flux q from the external region to the outer surface of the wall ④ n4 ;

[0140] Ⅱ. Heat conduction inside the wall ④;

[0141] III. Convective heat transfer between the inner surface of wall ④ and the air in the return air duct, and radiative heat transfer between the inner surface of wall ③ and the air in the return air duct.

[0142] Similar to wall ①②, the heat fluxes of the above three heat transfer processes should be equal, so we can get:

[0143] t 4外 =t outdoor (43)

[0144]

[0145] The same as for wall ①②, we can calculate t by formula (43) (44) 4内 , substituting into equations (45) and (46) we can get E b3外 Then we can get t 3外 .

[0146] 4) The heat transfer process on wall ③ includes:

[0147] Ⅰ. Convective heat exchange between the outer surface of wall ③ and the air in the return air duct, and radiative heat exchange with wall ④;

[0148] Ⅱ. Heat conduction inside wall ③;

[0149] III. Convective heat transfer between the inner surface of wall ③ and the air in the buffer zone, and radiative heat transfer between the inner surface of wall ③ and the outer surface of wall ② and the inner surfaces of wall ⑤ and ⑥;

[0150] Similar to the wall ①②④, the heat flux of the above three heat transfer processes should be equal, so we can get:

[0151]

[0152] Similar to the wall ①②④, q3 can be obtained by calculating through formula (47) (48), and substituting it into formula (49) to obtain t 3内 and E b3内 , which can be substituted into formulas (38) to (41) for calculation.

[0153] 5) The heat transfer process on the wall ⑤ includes:

[0154] Ⅰ. Heat conduction inside the wall ⑤;

[0155] II. Radiation heat transfer between the inner surface of wall ⑤, the outer surface of wall ②, and the inner surfaces of wall ③⑥;

[0156] Similarly, we can get:

[0157] t 5外 =t interlayer (50)

[0158]

[0159] q5=q Rad5,236 =J 5内 (52)

[0160] By using formulas (50) to (52), we can get t 5内 With J 5内 The relationship can be substituted into equations (38) to (41) for calculation.

[0161] Through the above calculations, only J remains in equations (38) to (41) 2外 、J 3内 、J 5内 , J6, x are five unknowns. Taking x as a known parameter, we can get four relations of effective radiation with respect to x. In the calculation process of wall ①②, we have already obtained t 1内 =g(J 2外 ), then J 2外 Substituting the relational expression about x into t 1内 The relationship about x

[0162] t 1内 =h(x) (53)

[0163] According to process requirements, t 1min ≤t 1内 ≤t 1max , then the range requirement of the buffer width x can be solved according to formula (53), that is,

[0164] t 1min ≤h(x)≤t 1max (54)

[0165] Finally, we can get x min ≤x≤x max , that is, the buffer width should be within this range during design.

[0166] The beneficial effects of the present invention are:

[0167] For clean rooms with high-precision temperature control requirements, this provides a certain reference for the calculation of buffer zone width.

[0168] 1. The heat generation in the core area of the cleanroom is basically stable, and the heat flux density entering the inner surface of wall ① is q n1 ;

[0169] 2. The external area of wall ④ is generally outdoors or other rooms, and the heat flux density received by its outer surface is q n4 , and the temperature of the outer surface is equal to the external environmental temperature;

[0170] 3. There are no equipment and other internal disturbance factors in the external area (upper technical mezzanine) of wall ⑤, and the temperature of its outer surface is equal to the temperature of the upper technical mezzanine;

[0171] 4. The air in the return air duct has been fully heat-exchanged indoors, and its temperature has reached the indoor set temperature.

[0172] 5. The temperature t1 of the inner surface of the clean wall panel in the core area is maintained within the range required for the indoor temperature, t 1min ≤t 1内

[0173] ≤t 1max .

[0174] 6. The length and width of each wall of the cleanroom are much larger than the thickness, and the heat conduction process from one side of the clean wall panel to the other side is considered as the heat conduction process of a one-dimensional steady-state infinite large flat plate.

[0175] 7. The height of the cleanroom is generally above 4m, the distance that the air passes over the surface of the clean wall panel is long, and the convective heat transfer processes between the inner and outer surfaces of all return air ducts and the air are regarded as the heat transfer of a one-dimensional steady-state infinite large flat plate.

[0176] 8. Walls ⑤ and ⑥ are basically perpendicular to the air flow, and the convective heat transfer process is not obvious, so its convective heat transfer effect is ignored.

[0177] 9. The distance between the two clean wall panels of the return air duct is generally much smaller than the height of the cleanroom, and the radiation heat transfer between them is considered according to the radiation heat transfer between two parallel infinite large flat plates.

[0178] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A calculation method for the width of a high-precision temperature-controlled clean room buffer zone, characterized in that it includes the following operations; 1. Establish a physical model of the clean room; 1.1 Structural Division: Core Area: It includes upper and lower technical mezzanines and a return air duct. The planar dimension is length × width = a × b, and the width of the return air duct is c; Buffer zone: surrounds the core zone in a ring, with the width being the unknown parameter x, the return air duct width being d, and the height being H; all walls are made of clean wall panels (thermal conductivity λ, thickness δ, surface emissivity ε), and insulation measures are added to the ground of the buffer zone; 1.2 Environmental assumptions: The heat generation in the core area is stable, and the heat flux density on the inner surface is q n1 ; The outer surface temperature of the buffer periphery (wall surface ④) is equal to the external ambient temperature t outdoor ; The outer surface temperature of the buffer ceiling (wall surface ⑤) is equal to the temperature t of the upper technical mezzanine interlayer r; The air temperature in the return air duct is equal to the set temperature t of the clean room n ; 2. Simplify the heat transfer process; 2.1 Heat conduction model: The length and width of each wall are much larger than its thickness, and it is regarded as a one-dimensional steady-state infinite plate heat conduction, and analyzed using Fourier's law; Inner surface temperature t of the core area wall ① 1内 shall meet the process requirement range: t 1min ≤t 1内 ≤t 1max ; 2.2 Convection and Radiation Model: The inner and outer surfaces of the return air duct (wall surfaces ① to ④): The air flow distance is long, and the convection heat transfer analysis is based on a one-dimensional steady-state infinite plate convection heat transfer analysis, and the convection coefficient is calculated in combination with the Nusselt number (Nu); Ceiling and floor (walls ⑤⑥): perpendicular to the airflow, and the return air outlet is on the side, so convection is ignored and only radiation heat transfer is considered; Radiation heat transfer: The enclosed buffer space is equivalent to a four-surface radiation heat network model, which is solved by simultaneously solving the view factor and the effective radiation equation. The two surfaces in the return air duct space are equivalent to the radiation heat transfer of two infinitely large plates.

3. Step-by-step calculation process; 3.1 Core area wall ① Heat transfer analysis: Combine the heat conduction equation, convection equation and radiation equation (1)(2)(3) to derive t 1内 With adjacent wall t 2内 Temperature relationship; 3.2 Heat transfer analysis of buffer zone wall ②~⑥: Analyze the heat conduction, convection and radiation processes of each wall in turn and establish a set of equations; Wall surface ②: (5)~(14); Wall surface ③: (20)~(22); Wall surface ④: (16)~(19); Wall surface ⑤: (23)~(25); Wall ⑥: The buffer zone floor has been insulated and is considered an insulating surface; 3.3 Simultaneously solve for the buffer width x: Substitute the core area temperature constraint t 1min ≤t 1内 ≤t 1max into the system of equations and finally organize it into the expression (26) of x; solve for the allowable range of x: x min ≤x≤x max .

2. The calculation method of the width of the high-precision temperature-controlled clean room buffer zone according to claim 1, characterized in that; The specific operations of step 1 are: Its main structure consists of two parts: the core area and the buffer area. The core area includes the upper and lower technical mezzanines and their return air ducts, and the buffer area includes the upper technical mezzanine and its return air ducts. The walls around the core area are recorded as wall surface ①, the outer wall of the return air duct in the core area is recorded as wall surface ②, the outer wall of the buffer area is recorded as wall surface ③, the outer wall of the return air duct in the buffer area is recorded as wall surface ④, the ceiling of the buffer area is recorded as wall surface ⑤, and the floor is recorded as wall surface ⑥; The core area has a length, b width, and c return air duct width. The buffer area is assumed to be a ring with equal width, x width, d return air duct width, and H room height. Among them, all the walls of the clean room are made of special clean wall panels, and additional insulation measures are taken for the buffer zone floor. For the clean wall panels, their thermal conductivity is λ, thickness is δ, and surface emissivity is ε; Denote the heat flux density entering the inner surface of wall ① as q n1 ; The external area of wall ④ is generally outdoors or other rooms. For the convenience of analysis, assume that the heat flux density received by its outer surface is q n4 , and the outer surface temperature is equal to the external environment temperature, denoted as t 4外 , t 4外 = t outdoor ; There are no equipment and other internal disturbance factors in the external area (upper technical mezzanine) of wall ⑤. It is considered that the outer surface temperature is equal to the upper technical mezzanine temperature, denoted as t 5外 , t 5外 = t interlayer ; The air in the return air duct has been fully heat-exchanged indoors and can be considered to have reached the indoor set temperature, that is, t f = t n ; To ensure that the temperature in the core area meets the requirements, it is necessary to maintain the inner surface temperature t1 of the clean wall panel in the core area within the range of the indoor temperature requirements. Otherwise, the convective heat transfer and radiative heat transfer processes between it and the indoor air will affect the indoor temperature; according to the process requirements, the range of the inner surface temperature of the clean room should be t 1min ≤t 1内 ≤t 1max .

3. The calculation method for the width of a high-precision temperature-controlled cleanroom buffer zone according to claim 1, characterized in that; The specific operations of step 3 are: Centering on the buffer zone, calculate this heat transfer process in the order from the inside out; for the convenience of analysis, first take the temperature t of the inner surface of the clean room 1内 as a known parameter for calculation, and finally organize it into a relational expression about x; 1) The heat transfer process on the wall ① includes: Ⅰ. Heat flux q transmitted from the interior to the inner surface of the wall ① n1 ; Ⅱ. Heat conduction inside the wall ①; III. Convective heat transfer between the outer surface of wall ① and the air in the return air duct, and radiative heat transfer between the outer surface of wall ① and the inner surface of wall ②; Since the heat transfer process on the wall is considered as one-dimensional, the above three The heat flows are equal, so we can get where t 1外 can be calculated by Equation (1). The Nusselt number Nu 1外 can be calculated by selecting an appropriate correlation formula according to the physical properties of air and the corresponding flow conditions and combining it with Equation (3), and then the convective heat transfer coefficient h1 outside can be obtained; Through the above calculations, t is obtained 1内 Regarding t 2内 The relational expression of, that is t 1内 = f(t 2内 ) (4) 2) The heat transfer process on wall ② includes: Ⅰ. Convective heat exchange between the inner surface of wall ② and the air in the return air duct, and radiative heat exchange between the inner surface of wall ② and the outer surface of wall ①; Ⅱ. Heat conduction inside wall ②; III. Convective heat transfer between the outer surface of wall ② and the air in the buffer zone, and radiative heat transfer between the outer surface of wall ③, ⑤, and ⑥; Similar to the wall ①, the heat fluxes of the above three heat transfer processes should be equal, so we can get: q2 = q h2外 +q Rad2,356 = h 2外 (t f - t 2外 ) + q Rad2,356 (8) q Rad2,356 = J 2外 (10) Similarly to the wall surface ①, the relationship between t and q2 can be obtained by calculating using equations (5) and (6). Substituting it into equation (7) can obtain the relationship between q2 and t. Then, by calculating using equations (8) to (10), the relationship between t and J can be obtained, that is, t = f(J), and then 2内 Similarly to q2, the relationship between t and q2 can be obtained by calculating using equations (5) and (6). Substituting it into equation (7) can obtain the relationship between q2 and t. 2外 The relationship between t and J can be obtained by calculating using equations (8) to (10), that is, t 2外 and J 2外 The relationship between t and J, that is, t 2内 = f(J 2外 ), and then t 1内 = g(J 2外 ) (15) In formulas (11) to (14), all view factors can be calculated mathematically and can be expressed as relations with respect to the buffer width x; for the remaining seven terms of E b2外 , E b3内 , E b5内 , J 2外 , J 3内 , J 5内 , J6, E b2外 can be calculated according to the relation between t 2外 and J 2外 , and E b3内 , E b5内 can be calculated based on the analysis of walls ③ to ⑤; 3) The heat transfer process on the wall ④ includes: Ⅰ. Heat flux q from the external region to the outer surface of wall ④ n4 ; Ⅱ. Heat conduction inside the wall ④; Ⅲ. Convective heat transfer between the inner surface of wall ④ and the air in the return air duct, and radiative heat transfer with wall ③; Similar to walls ① and ②, the heat fluxes of the above three heat transfer processes should be equal. From this, we can obtain: t 4外 = t outdoor (16) Similar to the wall surfaces ① and ②, t can be obtained by calculating with equations (16) and (17). 4内 , substituting into equations (18) and (19) gives E b3外 Furthermore, t can be obtained 3外 ; 4) The heat transfer process of wall ③ includes: Ⅰ. Convective heat transfer between the outer surface of wall ③ and the air in the return air duct, and radiative heat transfer with wall ④; Ⅱ. Heat conduction inside wall ③; Ⅲ. Convective heat transfer between the inner surface of wall ③ and the air in the buffer zone, and radiative heat transfer with the outer surface of wall ② and the inner surfaces of walls ⑤ and ⑥; Similar to walls ①, ②, and ④, the heat fluxes of the above three heat transfer processes should be equal. From this, we can obtain: Similarly to the wall surfaces ①②④, q3 can be calculated through equations (20) and (21), and substituting it into equation (22) gives t 3内 and E b3内 , which can be substituted into equations (11) to (14) for calculation; 5) The heat transfer process of wall ⑤ includes: Ⅰ. Heat conduction inside wall ⑤; Ⅱ. Radiative heat transfer between the inner surface of wall ⑤ and the outer surface of wall ② and the inner surfaces of walls ③ and ⑥; Similarly, we can obtain: (23) t 5外 = t interlayer q5 = q Rad5,236 = J 5内 (25) It can be calculated that t through formulas (23) to (25). 5内 and J 5内 The relational expressions can be substituted into formulas (11) to (14) for calculation. Through the above calculations, only J remains in equations (11) to (14). 2外 , J 3内 , J 5内 , J6, and x are the five unknowns. Taking x as a known parameter, four relationships of the effective radiation with respect to x can be obtained; and during the calculation of walls ① and ②, t 1内 = g(J 2外 ) has already been obtained. Then, substituting the relationship of J 2外 with respect to x, the relationship of t 1内 with respect to x can be obtained. t 1内 = h(x) (26) According to the process requirements, t 1min ≤ t 1内 ≤ t 1max , so the range requirement of the buffer width x can be solved according to Equation (26), that is t 1min ≤h(x)≤t 1max (27) Finally, x can be obtained min ≤x≤x max , that is, the buffer width should be within this range when designing.

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