Single-effect lithium bromide absorption type water chilling unit design method, device, equipment and medium

Abstract

The invention discloses a single-effect lithium bromide absorption type water chilling unit design method and device, equipment and a medium, and the method comprises the steps: building a hydraulic and thermal coupling calculation model based on the thermodynamic characteristics of a single-effect lithium bromide absorption type water chilling unit; and obtaining input variables, inputting the input variables into the constructed hydraulic and thermal coupling calculation model, and outputting various operation parameters of the water chilling unit. According to the method, various operation parameters of the water chilling unit can be calculated based on external input variable coupling, the inaccuracy of a traditional design calculation method is avoided, and the problems of complex calculation and low precision of the single-effect lithium bromide absorption type water chilling unit under the multivariable coupling condition are solved. The invention can be widely applied to the technical field of central air conditioners.

Description

Technical Field

[0001] The present invention relates to the technical field of central air conditioning, and in particular to a design method, device, equipment and medium for a single-effect lithium bromide absorption chiller. Background Art

[0002] According to statistics, the energy consumption of central air-conditioning systems accounts for more than 40% of the total energy consumption of public buildings. At the same time, due to the long-term extensive management mode of central air-conditioning system operation and maintenance managers in my country, the actual operating state of the system has long deviated from the optimal working condition. Therefore, optimizing and controlling the central air-conditioning system is an important measure for energy conservation and consumption reduction. The optimization operation of the cold source side of a large central air-conditioning system is a complex system engineering. At present, it is difficult to solve the problem of system stability by relying on human experience and simple control methods, and it is impossible to achieve the maximum energy saving. It is necessary to carry out reasonable hydraulic and thermal modeling of the entire cold source side. With the advancement of the dual carbon policy, various energy-saving technologies and strategies have developed rapidly. Among them, lithium bromide absorption chillers use low-grade thermal energy, such as steam, hot water, solar energy, etc. as driving energy instead of directly using electricity. This makes it have great advantages in the use of low-grade energy, especially suitable for the use of industrial waste heat and waste heat. Large central air-conditioning systems usually contain multiple subsystems and complex pipe network structures. Lithium bromide absorption chillers have significant interactions with these subsystems. Existing modeling methods are difficult to fully describe the dynamic behavior of the system and the interaction between multiple variables. The calculation efficiency is low, resulting in large deviations in the calculation results and limited optimization effects. Existing lithium bromide absorption chiller modeling methods mostly focus on static analysis under specific design conditions and lack the ability to dynamically model actual operating conditions. This method is difficult to reflect the actual performance of the equipment under different loads and environmental conditions. The determination of some key parameters, such as solution concentration, solution temperature, heat transfer coefficient, etc., is too vague, resulting in poor versatility of the model and difficulty in meeting actual application needs. Summary of the invention

[0003] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the object of the present invention is to provide a design method, device, equipment and medium for a single-effect lithium bromide absorption chiller.

[0004] The first technical solution adopted by the present invention is:

[0005] A design method for a single-effect lithium bromide absorption chiller comprises the following steps:

[0006] Based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller, a hydraulic-thermal coupling calculation model is constructed.

[0007] Obtain input variables, input the input variables into the constructed hydraulic and thermal coupling calculation model, and output various operating parameters of the chiller;

[0008] The working mode of the hydraulic and thermal coupling calculation model is as follows:

[0009] Set the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculate the absorption pressure of the absorber and the generation pressure of the generator;

[0010] Calculate the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculate the state point parameters of the system;

[0011] Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow required by the generator;

[0012] The evaporation temperature of the evaporator and the condensation temperature of the condenser are calculated iteratively, and when the preset iteration termination condition is reached, the calculated values ​​of the evaporation temperature and the condensation temperature are output. Exemplarily, the iteration termination condition here can be that the error between the calculated value of the evaporation temperature and the assumed value and the error between the calculated value of the condensation temperature and the assumed value are less than a preset value (such as 0.0001); after the iteration termination condition is reached, the calculated value of the evaporation temperature and the calculated value of the condensation temperature are output, and specifically, the output parameters also include the heat load of the absorber, the generator, the condenser, the evaporator, the solution heat exchanger, the cooling water outlet parameters, etc.

[0013] Furthermore, the single-effect lithium bromide absorption chiller comprises an evaporator, an absorber, a generator, a condenser and a solution heat exchanger;

[0014] The evaporator and the absorber are connected via a refrigerant water pipeline, the absorber and the generator are connected via a solution pipeline, the generator and the condenser are connected via a refrigerant water pipeline, the condenser and the evaporator are connected via a refrigerant water pipeline, and the solution heat exchanger is connected to the absorber and the generator via a solution pipeline.

[0015] Further, the setting of the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and the calculation of the absorption pressure of the absorber and the generation pressure of the generator include:

[0016] According to the given evaporation temperature and condensation temperature calculated by the outermost iteration, the liquid refrigerant water temperature at the condenser outlet, the liquid refrigerant water specific enthalpy at the condenser outlet, the refrigerant water vapor temperature at the evaporator outlet, the refrigerant water vapor specific enthalpy at the evaporator outlet and the refrigerant water circulation flow rate are calculated; and the evaporation pressure of the evaporator and the condensation pressure of the condenser are calculated;

[0017] According to the calculated evaporation pressure and condensation pressure, as well as the layout of the absorber and generator of the lithium bromide absorption chiller, the absorption pressure of the absorber and the generation pressure of the generator are calculated.

[0018] Furthermore, the connection mode between the absorber and the generator includes two operation modes: a solution pump variable frequency without bypass and a solution pump fixed frequency with bypass.

[0019] Furthermore, the calculation of the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and the calculation of the state point parameters of the system include:

[0020] Set the operation mode of lithium bromide absorption chiller;

[0021] According to the frequency of the solution circulation pump, an external input variable, the resistance of the pipeline from the absorber to the generator is obtained, the lift required by the solution pump is calculated, and the operating parameters of the solution pump and the solution circulation flow rate are iteratively calculated;

[0022] The circulation ratio is calculated based on the calculated solution circulation flow rate, and the mass fraction of the dilute solution at the absorber outlet and the mass fraction of the concentrated solution at the generator outlet are calculated in combination with the preset lithium bromide solution filling concentration;

[0023] The heat balance calculation of the solution heat exchanger is used to solve the outlet temperature of the concentrated solution side of the heat exchanger, the outlet specific enthalpy of the concentrated solution side of the heat exchanger, the outlet temperature of the dilute solution side of the heat exchanger and the outlet specific enthalpy of the dilute solution side of the heat exchanger, and a crystallization judgment is made.

[0024] Furthermore, the heat exchange mechanism model of each component of the refrigeration system is constructed, the heat transfer coefficient and heat transfer temperature difference of each heat exchange component of the model are calculated, and the heat source flow rate required by the generator is calculated, including:

[0025] According to the given chilled water flow rate and inlet and outlet water temperatures, calculate the total heat transfer coefficient and logarithmic mean temperature difference of the evaporator, and find the calculated value of the evaporation temperature t'0;

[0026] According to the dilute solution flow rate and concentrated solution flow rate of the solution heat exchanger, the heat transfer coefficient of the dilute solution surface on the inner side of the tube, the heat transfer coefficient of the concentrated solution surface on the outer side of the tube and the total heat transfer coefficient of the solution heat exchanger are calculated, and the outlet temperature of the concentrated solution side and the outlet temperature of the dilute solution side of the heat exchanger are respectively calculated through the heat balance equation of the solution heat exchanger to make a crystallization judgment;

[0027] Based on the given heat source parameters and the calculated state point parameters, the total heat transfer coefficient, the average heat transfer temperature difference and the heat load of the generator are calculated, and the heat source flow rate is calculated;

[0028] For the spray absorber, the external input variables are the total cooling water flow and inlet water temperature. It is necessary to calculate the absorber concentrated solution spray state point parameters, heat load and cooling water outlet temperature, and calculate the absorber total heat transfer coefficient and heat transfer temperature difference;

[0029] Based on the obtained state point parameters of the refrigeration system, calculate the condenser heat load and water outlet temperature, and calculate the total heat transfer coefficient and logarithmic mean temperature difference of the absorber to obtain the calculated value of the condensing temperature t' k .

[0030] Further, the iterative calculation of the evaporation temperature of the evaporator and the condensation temperature of the condenser includes:

[0031] The evaporation temperature and the condensation temperature are taken as two-dimensional variables for iterative calculation at the same time, the initial values ​​of the evaporation temperature and the condensation temperature are set, and the range of the evaporation temperature and the condensation temperature needs to be limited, and the initial iteration step is set;

[0032] Construct a square area, including the detection center point and four vertices, a total of five points, that is, five two-dimensional variable combinations;

[0033] Five thermal calculations were performed respectively, with the assumed value t0 and calculated value t'0 of evaporation temperature, the assumed value t k and the calculated value t' k As a constraint, the error values ​​of the five points are calculated, and the point with the smallest error value is used as the new detection center point to determine the new calculation search range.

[0034] The second technical solution adopted by the present invention is:

[0035] A single-effect lithium bromide absorption chiller design device, comprising:

[0036] Model building module, used to build a hydraulic and thermal coupling calculation model based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller;

[0037] The coupling calculation module is used to obtain input variables, input the input variables into the constructed hydraulic and thermal coupling calculation model, and output various operating parameters of the chiller;

[0038] The working mode of the hydraulic and thermal coupling calculation model is as follows:

[0039] Set the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculate the absorption pressure of the absorber and the generation pressure of the generator;

[0040] Calculate the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculate the state point parameters of the system;

[0041] Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow required by the generator;

[0042] The evaporation temperature of the evaporator and the condensation temperature of the condenser are calculated iteratively, and when the preset iteration termination condition is reached, the calculated values ​​of the evaporation temperature and the condensation temperature are output.

[0043] The third technical solution adopted by the present invention is:

[0044] An electronic device comprises a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, at least one program, the code set or the instruction set is loaded and executed by the processor to implement a single-effect lithium bromide absorption chiller design method as described above.

[0045] The fourth technical solution adopted by the present invention is:

[0046] A computer-readable storage medium stores at least one instruction, at least one program, a code set or an instruction set, wherein the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by a processor to implement a single-effect lithium bromide absorption chiller design method as described above.

[0047] The fifth technical solution adopted by the present invention is:

[0048] A computer program product or a computer program, the computer program product or the computer program includes computer instructions, the computer instructions are stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the above-mentioned single-effect lithium bromide absorption chiller design method.

[0049] The beneficial technical effect of the present invention is: based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller, the present invention constructs a hydraulic-thermal coupling calculation model, which can calculate various operating parameters of the chiller based on external input variable coupling, avoiding the inaccuracy of referring to traditional design calculation methods, and solving the problem of complex calculation and low precision of a single-effect lithium bromide absorption chiller under multi-variable coupling conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1It is a schematic diagram of a single-effect lithium bromide absorption chiller system in an embodiment of the present invention;

[0052] Figure 2 It is a flow chart of the iterative calculation logic of the hydraulic and thermal coupling calculation model in an embodiment of the present invention;

[0053] Figure 3 It is a flow chart of the calculation logic of the thermal calculation model of the spray type evaporator in the embodiment of the present invention;

[0054] Figure 4 It is a flow chart of the calculation logic of the thermal calculation model of the shell and tube liquid heat exchanger in the embodiment of the present invention;

[0055] Figure 5 It is a flow chart of the calculation logic of the thermal calculation model of the immersion generator in an embodiment of the present invention;

[0056] Figure 6 It is a flow chart of the calculation logic of the thermal calculation model of the spray absorber in the embodiment of the present invention;

[0057] Figure 7 It is a flow chart of the calculation logic of the condenser thermal calculation model in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0059] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0060] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0061] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0062] The central air conditioning system uses chillers to generate cooling capacity, and most types of chillers are electric refrigeration. However, how to reduce the energy consumption of chillers has become one of the research directions. Using waste heat to provide energy for chillers is a rapidly developing method. However, the existing modeling methods are difficult to fully describe the dynamic behavior of the system and the interaction between multiple variables. The calculation efficiency is low, resulting in large deviations in the calculation results and limited optimization effects. Therefore, a calculation model of a single-effect lithium bromide absorption chiller is proposed. Figure 1 It is the iterative calculation idea for the whole system, including the iteration of the evaporation temperature and condensation temperature of the outermost layer, as well as the calculation idea of ​​the heat exchangers of the nested components in the middle.

[0063] Example 1

[0064] This embodiment provides a single-effect lithium bromide absorption chiller design method, comprising the following steps:

[0065] Step 1: Based on the thermodynamic characteristics of the single-effect lithium bromide absorption chiller, a hydraulic and thermal coupling calculation model is constructed;

[0066] Step 2: Obtain input variables, input the input variables into the constructed hydraulic-thermal coupling calculation model, and output various operating parameters of the chiller.

[0067] See also Figure 1 The single-effect lithium bromide absorption chiller comprises an evaporator, an absorber, a generator, a condenser and a solution heat exchanger; the evaporator and the absorber are connected by a refrigerant water pipeline, the absorber and the generator are connected by a solution pipeline, the generator and the condenser are connected by a refrigerant water pipeline, the condenser and the evaporator are connected by a refrigerant water pipeline, and the solution heat exchanger is connected to the absorber and the generator by a solution pipeline.

[0068] See also Figure 2 The working mode of the hydraulic and thermal coupling calculation model specifically includes the following steps:

[0069] S1. Set the initial values ​​of the evaporator evaporation temperature and the condenser condensation temperature, and calculate the absorption pressure of the absorber and the generation pressure of the generator.

[0070] In some embodiments, step S1 specifically includes the following steps:

[0071] S11. According to the given evaporation temperature and condensation temperature calculated by the outermost iteration, the liquid refrigerant water temperature at the condenser outlet, the liquid refrigerant water specific enthalpy at the condenser outlet, the refrigerant water vapor temperature at the evaporator outlet, the refrigerant water vapor specific enthalpy at the evaporator outlet and the refrigerant water circulation flow rate are calculated.

[0072] S12. According to the arrangement of absorber and generator of lithium bromide absorption chiller, calculate the absorption pressure of absorber and the generation pressure of generator.

[0073] The outermost iterative calculation gives the evaporation temperature t0 and the condensation temperature t k Therefore, the condenser outlet liquid refrigerant water temperature, condenser outlet liquid refrigerant water specific enthalpy, evaporator outlet refrigerant water vapor temperature, evaporator outlet refrigerant water vapor specific enthalpy can be calculated. Under the premise of knowing the external input variable cooling load, the refrigerant water circulation flow G can be calculated. m . Given the evaporation temperature t0 and the condensation temperature t k Then the evaporation pressure p0 and condensation pressure p k Usually, the evaporator and absorber of the lithium bromide absorption chiller are placed in the same cylinder, and the generator and condenser are placed in the same cylinder. Therefore, the flow resistance between the evaporator and absorber, and between the condenser and the generator can be ignored. It is approximately assumed that the pressure p g Equal to p k , absorption pressure p a Equal to p0.

[0074] S2. Calculate the solution circulation flow rate of the solution pump according to the connection method of the absorber and the generator, and calculate the state point parameters of the system.

[0075] Specifically, the single-effect lithium bromide absorption chiller model has two connection modes: solution pump variable frequency without bypass and solution pump fixed frequency dilute solution bypass. The lithium bromide solution flow, solution pump head and power of the solution pump are iteratively calculated according to the selected operation mode, and the main state point parameters of the system are calculated. The state point parameters here include parameters such as enthalpy, temperature, solution mass fraction, etc. Figure 1 Point 1, point 2, etc. are all unknown points in the equation.

[0076] As an optional implementation, step S2 includes the following steps:

[0077] S21. Set the operation mode of the lithium bromide absorption chiller.

[0078] S22. According to the frequency of the solution circulation pump, which is an external input variable, the resistance of the pipeline from the absorber to the generator is obtained, the lift required to be provided by the solution pump is calculated, and the operating parameters of the solution pump and the solution circulation flow rate are iteratively calculated.

[0079] S23. Calculate the circulation ratio based on the calculated solution circulation volume, and calculate the mass fraction of the dilute solution at the absorber outlet and the mass fraction of the concentrated solution at the generator outlet in combination with the lithium bromide solution filling concentration.

[0080] S24. The outlet temperature of the concentrated solution side of the heat exchanger, the outlet specific enthalpy of the concentrated solution side of the heat exchanger, the outlet temperature of the dilute solution side of the heat exchanger and the outlet specific enthalpy of the dilute solution side of the heat exchanger are calculated by heat balance calculation of the solution heat exchanger, and a crystallization judgment is made.

[0081] See also Figure 2 , Figure 2 This is the iterative calculation logic diagram of the hydraulic and thermal coupling calculation model. The operation modes of the lithium bromide absorption chiller include solution pump fixed frequency dilute solution bypass and solution pump variable frequency without bypass. The operation mode must be set first. The frequency of the solution circulation pump n pump The head Δp required by the solution pump is the external input variable pump for (p g -p a ) and the solution overcome the resistance Δp of the pipeline from the absorber to the generator a-g The sum [i.e. Δp pump =(p g -p a )+Δp a-g ], it is necessary to iteratively calculate the effective head of the solution pump, and fit the parameters according to the performance curve of the solution pump with Δp pump As a constraint, the effective head of the water pump can be iterated, and the flow rate G1 of the lithium bromide solution at the outlet of the absorber can be calculated. If the operation mode is the solution pump variable frequency without bypass, the circulation volume G2 of the lithium bromide solution of the entire chiller is equal to G1; if the operation mode is the solution pump fixed frequency dilute solution bypass, since the flow rate of the bypass dilute solution is controlled by the electric three-way valve, it can be considered that the bypass flow rate is known, that is, the absorber dilute solution recirculation ratio f is controllable, then the circulation volume G2 of the lithium bromide solution can be calculated, that is, the flow rate of the dilute solution entering the generator.

[0082] G2 and G m The circulation ratio a can be calculated, and then according to the circulation ratio a and the mass fraction of lithium bromide solution charged in the unit ξ0, the mass fraction of dilute solution at the absorber outlet ξ can be calculated a And the mass fraction of concentrated solution at the generator outlet ξ g [Simultaneous equations ξ a +ξ g=2ξ0 and a=ξ g / (ξ g -ξ a )], and the absorber outlet dilute solution temperature, absorber outlet dilute solution specific enthalpy, generator outlet concentrated solution temperature, and generator outlet concentrated solution specific enthalpy can be calculated at the same time. Then, the outlet temperatures of the concentrated solution side and the dilute solution side of the heat exchanger are calculated respectively through the solution heat exchanger thermodynamic calculation model. At this time, the states of all state points of the refrigeration system are known.

[0083] S3. Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow rate required by the generator.

[0084] Exemplarily, step S3 specifically includes the following steps:

[0085] S31. According to the given chilled water flow rate and inlet and outlet water temperatures, calculate the total heat transfer coefficient and logarithmic mean temperature difference of the evaporator, and obtain the calculated value of the evaporation temperature t'0.

[0086] S32. Given the mass fraction of the dilute solution at the absorber outlet and the mass fraction of the concentrated solution at the generator outlet, calculate the surface heat transfer coefficient of the dilute solution on the inside of the tube, the surface heat transfer coefficient of the concentrated solution on the outside of the tube and the total heat transfer coefficient of the solution heat exchanger based on the calculated dilute solution flow rate and concentrated solution flow rate of the solution heat exchanger. Calculate the outlet temperature of the concentrated solution side and the outlet temperature of the dilute solution side of the heat exchanger through the heat balance equation of the solution heat exchanger to make a crystallization judgment.

[0087] S33. Based on the given heat source parameters and the calculated state point parameters, calculate the total heat transfer coefficient, average heat transfer temperature difference and heat load of the generator, and calculate the heat source flow rate.

[0088] S34. For the spray absorber, the external input variables are the total cooling water flow rate and the inlet water temperature. It is necessary to calculate the absorber concentrated solution spray state point parameters, heat load and cooling water outlet temperature, and calculate the total heat transfer coefficient and heat transfer temperature difference of the absorber.

[0089] S35. Based on the obtained refrigeration system state point parameters, calculate the condenser heat load and water outlet temperature, and calculate the total heat transfer coefficient and logarithmic mean temperature difference of the absorber to obtain the calculated value of the condensing temperature t' k .

[0090] like Figure 3 The calculation logic of the spray evaporator thermal calculation model is shown in the figure. The chilled water flow rate G is known. chand inlet and outlet temperatures, the flow rate, thermal conductivity, viscosity and Prandtl number of the chilled water inside the tube can be calculated, and then the heat transfer coefficient of the chilled water surface inside the tube can be calculated. Since the outer iteration assumes an evaporation temperature, the refrigerant water flow rate can be calculated based on the assumed condensation temperature, and the thermal conductivity, density, viscosity, Prandtl number and spray volume of the refrigerant water outside the tube are calculated, and then the heat transfer coefficient of the refrigerant water surface outside the tube is calculated. Furthermore, the total heat transfer coefficient and logarithmic mean temperature difference of the evaporator are calculated to obtain the calculated value of the evaporation temperature t'0.

[0091] like Figure 4 The calculation logic of the shell and tube solution heat exchanger thermal calculation model is shown. If the mass fraction of the dilute solution at the absorber outlet and the absorption pressure are known, the dilute solution temperature at the absorber outlet and the specific enthalpy of the dilute solution at the absorber outlet can be calculated. The inlet temperature t'3 of the dilute solution side of the solution heat exchanger is equal to the dilute solution temperature t2 at the absorber outlet. Taking t'3 as the qualitative temperature, the thermal conductivity, viscosity and Reynolds number Re of the dilute solution side can be calculated. in and Prandtl number and other physical parameters, due to Re in Different ranges of heat transfer coefficients need to be calculated using different formulas, so it is necessary to calculate the heat transfer coefficient according to Re in Select the corresponding calculation formula to calculate the heat transfer coefficient K of the dilute solution surface inside the solution heat exchanger tube i,ex ; If the mass fraction of the concentrated solution at the generator outlet and the generated pressure are known, the concentrated solution temperature and specific enthalpy at the generator outlet can be calculated. The inlet temperature t'3 of the concentrated solution side of the solution heat exchanger is equal to the concentrated solution temperature t2 at the generator outlet. Taking t'3 as the qualitative temperature, the thermal conductivity, viscosity and Reynolds number Re of the concentrated solution side can be calculated. out and Prandtl number and other physical parameters, so as to calculate the surface heat transfer coefficient K of the concentrated solution on the outside of the solution heat exchanger tube o,ex Furthermore, the total heat transfer coefficient K of the solution heat exchanger is calculated based on the known thermal resistance of the dirt inside and outside the tube. ex With heat load Q ex But in fact, the outlet temperature t3 of the dilute solution side and the outlet temperature t5 of the concentrated solution side of the heat exchanger are unknown. Further, through the two heat balance equations of the solution heat exchanger [Q = F·K·Δt and Q = G2c p,3' (t3-t 3' )=(G2-G m )c p,4 (t3-t 3' )], t5 and t3 can be calculated. It should be noted that when the mass fraction of lithium bromide solution is too high or the temperature is too low, there is a possibility of crystallization. Solution crystallization may block the pipe and the surface of the heat exchanger, increase the flow resistance of the system, reduce the heat exchange efficiency, and affect the refrigeration effect. The state point where the lithium bromide chiller is most likely to crystallize is at the outlet of the concentrated solution side of the solution heat exchanger, so it is necessary to calculate the crystallization temperature t of the lithium bromide solution at this points , if t5>t s , then there is no risk of crystallization during the operation of the lithium bromide unit.

[0092] like Figure 5 The calculation logic of the immersion generator thermal calculation model shown in the figure corresponds to the generating pressure. The dilute solution at the generator inlet is in a supercooled state. The generating process begins when the dilute solution absorbs the heat from the heat source in the generator and reaches a saturated state, thereby generating refrigerant water vapor. At this time, the solution saturation temperature is t 3s When the generation of refrigerant water vapor ends, the solution temperature is t4, and the refrigerant water vapor temperature at the generator outlet, i.e., the condenser inlet, is t7 = (t 3s +t4) / 2, and then calculate the generator heat load Q gen The known external input variables of the generator are the heat source parameters: if the heat source is saturated water vapor, then the saturated water vapor temperature or the saturated water vapor pressure is known. Since the heat released by the phase change process of water vapor is much greater than the heat released by the supercooling state, it is approximately assumed that the outlet of the heat source side of the generator is saturated liquid water. What needs to be calculated is the saturated water vapor flow rate G h ; If the heat source is hot water, the inlet and outlet water temperatures on the heat source side of the generator are generally specified. The hot water flow rate G can be calculated based on the heat balance equation h Furthermore, the physical parameters related to the heat source inside the tube are calculated, and then the heat transfer coefficient K of the heat source surface inside the tube is calculated. i,gen ; For the solution outside the tube, the solution heat flux density has been calculated, and the average mass fraction of the dilute solution at the generator inlet and the concentrated solution at the outlet is taken as the average mass fraction of the generator solution, and then the surface heat transfer coefficient K of the solution outside the tube is calculated. o,gen Furthermore, the total heat transfer coefficient K of the generator is calculated based on the known thermal resistance of the dirt inside and outside the tube. gen and heat transfer temperature difference Δt gen .

[0093] like Figure 6 The calculation logic of the thermal calculation model of the spray absorber shown in the figure, the external input variables are the total cooling water flow and the inlet water temperature. The operation modes of the lithium bromide absorption chiller include solution pump fixed frequency dilute solution bypass and solution pump variable frequency without bypass. If the operation mode is solution pump variable frequency without bypass, the specific enthalpy of the absorber spray solution h6=h5; if the operation mode is solution pump fixed frequency dilute solution bypass, it is necessary to calculate the flow, mass fraction and specific enthalpy h6 of the mixed spray solution. Calculate the absorber heat load Q according to the absorber heat balance equation ab , and then calculate the absorber cooling water outlet temperature t ab,co,out Knowing the cooling water flow rate and inlet and outlet water temperatures, the cooling water flow rate, thermal conductivity, viscosity and Prandtl number inside the absorber tube can be obtained, and then the surface heat transfer coefficient K of the cooling water inside the tube can be calculated. i,ab; Given the absorber spray solution flow rate, calculate the spray density T, and then calculate the heat transfer coefficient K of the solution surface outside the tube o,ab Then, the total heat transfer coefficient K of the absorber is calculated based on the known thermal resistance of the dirt inside and outside the tube. ab and heat transfer temperature difference Δt ab .

[0094] like Figure 7 The calculation logic of the condenser thermal calculation model shown in the figure has obtained the inlet and outlet specific enthalpy of the condenser refrigerant water and the circulation flow rate G m , and then calculate the condenser heat load Q con and heat flux q con The cooling water of the present invention is a series process, that is, the cooling water first cools the absorber and then cools the condenser, so the inlet temperature of the cooling water of the condenser is t con,co,in is the absorber cooling water outlet temperature t ab,co,out , the condenser cooling water outlet temperature t can be calculated if the condenser heat load is known ab,co,out Furthermore, the physical properties of the cooling water inside the tube, including thermal conductivity, viscosity and Prandtl number, are calculated based on the average values ​​of the inlet and outlet temperatures of the cooling water, and then the surface heat transfer coefficient K of the cooling water inside the tube is calculated. i,con ; Then, the condensation temperature assumption value is used as the qualitative temperature to calculate the relevant physical properties of the refrigerant water outside the tube, including latent heat of vaporization, density, viscosity and thermal conductivity, and then the heat transfer coefficient K of the refrigerant water surface outside the tube is calculated. o,con Then, the total heat transfer coefficient K of the condenser is calculated based on the known thermal resistance of dirt inside and outside the tube. con and heat transfer temperature difference Δt m , and calculate the condensation temperature t' k .

[0095] S4. Iteratively calculate the evaporation temperature of the model evaporator and the condensation temperature of the condenser.

[0096] As an optional implementation, step S4 includes the following steps:

[0097] S41. Iterative calculation initialization module, the evaporation temperature and the condensation temperature are iteratively calculated simultaneously as two-dimensional variables, the initial values ​​of the evaporation temperature and the condensation temperature are set, and the range of the evaporation temperature and the condensation temperature needs to be limited, and the initial iteration step is set.

[0098] S42. Iterate the calculation search module to construct a square area, including the detection center point and four vertices, a total of five points, that is, five two-dimensional variable combinations.

[0099] S43. Iterative calculation error judgment module, five thermal calculations, respectively, with the evaporation temperature assumed value t0 and the calculated value t'0, the condensation temperature assumed value t k and the calculated value t'k As a constraint, the error values ​​of the five points are calculated, and the point with the smallest error value is used as the new detection center point to determine the new calculation search range.

[0100] In summary, the method of the present invention has at least the following advantages and beneficial effects compared to the prior art:

[0101] (1) The present invention adopts a multivariable global coupling calculation method to convert some artificially assumed parameters into coupling calculations, thereby improving the accuracy and versatility of the model.

[0102] (2) The modeling method provided by the present invention can simulate the operating characteristics of the chiller under various working conditions, establish the thermodynamic processes of the key components of the single-effect lithium bromide absorption chiller, such as the generator, absorber, evaporator and condenser, and solve the complex variable interaction problem in the single-effect lithium bromide absorption chiller.

[0103] (3) The present invention adopts an efficient algorithm structure, reduces multiple iterative calculation processes, improves calculation efficiency, and can generate a large amount of data in a short time, obtain operating data characteristics under different working conditions, solve the problem of data sparsity, and provide a basis for the subsequent rapid diagnosis of the air-conditioning system.

[0104] (4) The present invention can calculate the operating conditions of different heat source types, including steam type and hot water type, based on the same model, thereby solving the problem of a wide variety of models.

[0105] Example 2

[0106] This embodiment provides a single-effect lithium bromide absorption chiller design device, comprising:

[0107] Model building module, used to build a hydraulic and thermal coupling calculation model based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller;

[0108] The coupling calculation module is used to obtain input variables, input the input variables into the constructed hydraulic and thermal coupling calculation model, and output various operating parameters of the chiller;

[0109] The working mode of the hydraulic and thermal coupling calculation model is as follows:

[0110] Set the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculate the absorption pressure of the absorber and the generation pressure of the generator;

[0111] Calculate the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculate the state point parameters of the system;

[0112] Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow required by the generator;

[0113] The evaporation temperature of the evaporator and the condensation temperature of the condenser are calculated iteratively.

[0114] Since the device is a single-effect lithium bromide absorption chiller design device of an embodiment of the present invention, and the principle of solving the problem by the device is similar to that of the method, the implementation of the device can refer to the implementation process of the above-mentioned method embodiment, and the repeated parts will not be repeated.

[0115] Example 3

[0116] An embodiment of the present invention further provides an electronic device, the electronic device comprising a processor and a memory, the memory storing at least one instruction, at least one program, a code set or an instruction set, the at least one instruction, the at least one program, the code set or the instruction set being loaded and executed by the processor to implement the following Figure 2 The method shown.

[0117] It is understood that the memory may include a random access memory (RAM) or a read-only memory (ROM). Optionally, the memory includes a non-transitory computer-readable storage medium. The memory may be used to store instructions, programs, codes, code sets, or instruction sets. The memory may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function, instructions for implementing the above-mentioned various method embodiments, etc.; the data storage area may store data created according to the use of the server, etc.

[0118] The processor may include one or more processing cores. The processor uses various interfaces and lines to connect the various parts of the entire server, and executes various functions of the server and processes data by running or executing instructions, programs, code sets or instruction sets stored in the memory, and calling data stored in the memory. Optionally, the processor can be implemented in at least one hardware form of digital signal processing (DSP), field programmable gate array (FPGA), and programmable logic array (PLA). The processor can integrate one or a combination of a central processing unit (CPU) and a modem. Among them, the CPU mainly processes the operating system and application programs; the modem is used to process wireless communications. It can be understood that the above-mentioned modem may not be integrated into the processor, but implemented separately through a chip.

[0119] Since the electronic device is an electronic device corresponding to a single-effect lithium bromide absorption chiller design method of an embodiment of the present invention, and the principle of solving the problem by the electronic device is similar to that of the method, the implementation of the electronic device can refer to the implementation process of the above-mentioned method embodiment, and the repeated parts will not be repeated.

[0120] Example 4

[0121] The embodiment of the present invention further provides a computer-readable storage medium, wherein the storage medium stores at least one instruction, at least one program, code set or instruction set, and the at least one instruction, the at least one program, the code set or instruction set is loaded and executed by a processor to implement the following Figure 2 The method shown.

[0122] Those skilled in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium includes a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable rewritable read-only memory (EEPROM), a compact disc (CD-ROM) or other optical disc storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium that can be used to carry or store data.

[0123] Since the storage medium is the storage medium corresponding to the single-effect lithium bromide absorption chiller design method of an embodiment of the present invention, and the principle of solving the problem by the storage medium is similar to that of the method, the implementation of the storage medium can refer to the implementation process of the above-mentioned method embodiment, and the repeated parts will not be repeated.

[0124] Example 5

[0125] In some possible implementations, various aspects of the method of the embodiment of the present invention can also be implemented in the form of a program product, which includes a program code. When the program product is run on a computer device, the program code is used to enable the computer device to execute the steps of a single-effect lithium bromide absorption chiller design method according to various exemplary embodiments of the present application described above in this specification. Among them, the executable computer program code or "code" for executing each embodiment can be written in a high-level programming language such as C, C++, C#, Smalltalk, Java, JavaScript, Visual Basic, structured query language (e.g., Transact-SQL), Perl, or in various other programming languages.

[0126] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0127] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0128] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a single-effect lithium bromide absorption chiller, characterized in that: The following steps are involved: Based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller, a hydraulic-thermal coupling calculation model is constructed. Obtain input variables, input the input variables into the constructed hydraulic and thermal coupling calculation model, and output various operating parameters of the chiller; The working mode of the hydraulic and thermal coupling calculation model is as follows: Set the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculate the absorption pressure of the absorber and the generation pressure of the generator; Calculate the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculate the state point parameters of the effective lithium bromide absorption refrigeration system; Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow required by the generator; The evaporation temperature of the evaporator and the condensation temperature of the condenser are calculated iteratively, and when the preset iteration termination condition is reached, the calculated values ​​of the evaporation temperature and the condensation temperature are output.

2. A single-effect lithium bromide absorption chiller design method according to claim 1, characterized in that: The single-effect lithium bromide absorption chiller comprises an evaporator, an absorber, a generator, a condenser and a solution heat exchanger; The evaporator and the absorber are connected via a refrigerant water pipeline, the absorber and the generator are connected via a solution pipeline, the generator and the condenser are connected via a refrigerant water pipeline, the condenser and the evaporator are connected via a refrigerant water pipeline, and the solution heat exchanger is connected to the absorber and the generator via a solution pipeline.

3. The design method of a single-effect lithium bromide absorption chiller according to claim 1, characterized in that: The step of setting the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculating the absorption pressure of the absorber and the generation pressure of the generator includes: According to the given evaporation temperature and condensation temperature calculated by the outermost iteration, the liquid refrigerant water temperature at the condenser outlet, the liquid refrigerant water specific enthalpy at the condenser outlet, the refrigerant water vapor temperature at the evaporator outlet, the refrigerant water vapor specific enthalpy at the evaporator outlet and the refrigerant water circulation flow rate are calculated; and the evaporation pressure of the evaporator and the condensation pressure of the condenser are calculated; According to the calculated evaporation pressure and condensation pressure, as well as the layout of the absorber and generator of the lithium bromide absorption chiller, the absorption pressure of the absorber and the generation pressure of the generator are calculated.

4. The design method of a single-effect lithium bromide absorption chiller according to claim 1, characterized in that: The connection mode of the absorber and the generator includes two operation modes: a solution pump variable frequency without bypass and a solution pump fixed frequency with bypass.

5. A single-effect lithium bromide absorption chiller design method according to claim 1 or 4, characterized in that: The method of calculating the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculating the state point parameters of the system, includes: Set the operation mode of lithium bromide absorption chiller; According to the frequency of the solution circulation pump, an external input variable, the resistance of the pipeline from the absorber to the generator is obtained, the lift required by the solution pump is calculated, and the operating parameters of the solution pump and the solution circulation flow rate are iteratively calculated; The circulation ratio is calculated based on the calculated solution circulation flow rate, and the mass fraction of the dilute solution at the absorber outlet and the mass fraction of the concentrated solution at the generator outlet are calculated in combination with the preset lithium bromide solution filling concentration; The heat balance calculation of the solution heat exchanger is used to solve the outlet temperature of the concentrated solution side of the heat exchanger, the outlet specific enthalpy of the concentrated solution side of the heat exchanger, the outlet temperature of the dilute solution side of the heat exchanger and the outlet specific enthalpy of the dilute solution side of the heat exchanger, and a crystallization judgment is made.

6. A single-effect lithium bromide absorption chiller design method according to claim 1, characterized in that: The heat exchange mechanism model of each component of the refrigeration system is constructed, the heat transfer coefficient and heat transfer temperature difference of each heat exchange component of the model are calculated, and the heat source flow rate required by the generator is calculated, including: According to the given chilled water flow rate and inlet and outlet water temperatures, calculate the total heat transfer coefficient and logarithmic mean temperature difference of the evaporator, and find the calculated value of the evaporation temperature t'0; According to the dilute solution flow rate and concentrated solution flow rate of the solution heat exchanger, the heat transfer coefficient of the dilute solution surface on the inner side of the tube, the heat transfer coefficient of the concentrated solution surface on the outer side of the tube and the total heat transfer coefficient of the solution heat exchanger are calculated, and the outlet temperature of the concentrated solution side and the outlet temperature of the dilute solution side of the heat exchanger are respectively calculated through the heat balance equation of the solution heat exchanger to make a crystallization judgment; Based on the given heat source parameters and the calculated state point parameters, the total heat transfer coefficient, the average heat transfer temperature difference and the heat load of the generator are calculated, and the heat source flow rate is calculated; For the spray absorber, the external input variables are the total cooling water flow and inlet water temperature. It is necessary to calculate the absorber concentrated solution spray state point parameters, heat load and cooling water outlet temperature, and calculate the absorber total heat transfer coefficient and heat transfer temperature difference; Based on the obtained state point parameters of the refrigeration system, calculate the condenser heat load and water outlet temperature, and calculate the total heat transfer coefficient and logarithmic mean temperature difference of the absorber to obtain the calculated value of the condensing temperature t' k .

7. The design method of a single-effect lithium bromide absorption chiller according to claim 1, characterized in that: The iterative calculation of the evaporation temperature of the evaporator and the condensation temperature of the condenser includes: The evaporation temperature and the condensation temperature are taken as two-dimensional variables for iterative calculation at the same time, the initial values ​​of the evaporation temperature and the condensation temperature are set, and the range of the evaporation temperature and the condensation temperature needs to be limited, and the initial iteration step is set; Construct a square area, including the detection center point and four vertices, a total of five points, that is, five two-dimensional variable combinations; Five thermal calculations were performed respectively, with the assumed value t0 and calculated value t'0 of evaporation temperature, the assumed value t k and the calculated value t' k As a constraint, the error values ​​of the five points are calculated, and the point with the smallest error value is used as the new detection center point to determine the new calculation search range.

8. A single-effect lithium bromide absorption chiller design device, characterized in that: include: Model building module, used to build a hydraulic and thermal coupling calculation model based on the thermodynamic characteristics of a single-effect lithium bromide absorption chiller; The coupling calculation module is used to obtain input variables, input the input variables into the constructed hydraulic and thermal coupling calculation model, and output various operating parameters of the chiller; The working mode of the hydraulic and thermal coupling calculation model is as follows: Set the initial value of the evaporation temperature of the evaporator and the initial value of the condensation temperature of the condenser, and calculate the absorption pressure of the absorber and the generation pressure of the generator; Calculate the solution circulation flow rate of the solution pump according to the connection mode of the absorber and the generator, and calculate the state point parameters of the system; Construct a heat exchange mechanism model for each component of the refrigeration system, calculate the heat transfer coefficient and heat transfer temperature difference of each heat exchange component in the model, and calculate the heat source flow required by the generator; The evaporation temperature of the evaporator and the condensation temperature of the condenser are calculated iteratively, and when the preset iteration termination condition is reached, the calculated values ​​of the evaporation temperature and the condensation temperature are output.

9. An electronic device, characterized in that: The electronic device includes a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by the processor to implement the method described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The storage medium stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by the processor to implement the method according to any one of claims 1 to 7.

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