CN113446077B - Temperature optimization method for organic Rankine cycle system with heat conduction oil circulation - Google Patents

Abstract

The invention relates to the technical field of low-temperature waste heat recovery, and discloses a method for optimizing the temperature of an organic Rankine cycle system with heat-conducting oil circulation, aiming at the evaporation temperature and condensation of the evaporator and condenser in the organic Rankine cycle system with heat-conducting oil circulation The temperature is optimized, the gray wolf algorithm is improved, the non-linear improvement of its position update formula is improved, and its convergence factor is improved by adding Latin hypercube sampling and chaotic search to improve the algorithm's optimization ability and speed, and prevent it from falling into local optimum. Combined with the improved gray wolf algorithm to optimize the evaporation temperature and condensation temperature, so as to achieve the effect of optimizing the overall performance of the organic Rankine cycle system. Compared with the existing technology, the present invention can improve the energy utilization rate and improve the system thermal efficiency and output power.

Description

A Method for Optimizing Temperature of Organic Rankine Cycle System with Thermal Oil Circulation

technical field

The invention relates to the technical field of low-temperature waste heat recovery, in particular to a method for optimizing the temperature of an organic Rankine cycle system with heat transfer oil circulation.

Background technique

With the acceleration of the industrialization process, the problem of energy shortage has become a global problem. With the burning of fossil fuels, the problem of environmental pollution is becoming more and more serious, and the energy crisis has become an urgent problem that threatens our lives. Human beings cannot live without energy, but not all energy sources are sustainable. Therefore, people began to shift their attention from fossil energy to clean, renewable energy and industrial waste energy to reduce pollution and use energy in a more efficient manner. Renewable energy sources such as wind, solar and geothermal energy are gaining more and more attention. In the process of industrial production, internal combustion engines or gas turbines emit a large amount of high-temperature exhaust gas, and the temperature of the exhaust gas usually exceeds 200°C, while industrial wastewater contains a large amount of medium and low temperature heat, but the recovery rate of these heat is low, and most of them are discharged as waste heat, resulting in energy waste. Therefore, an effective means of energy recovery and utilization is needed to improve energy utilization and reduce environmental pollution, so as to achieve sustainable development goals. The Organic Rankine Cycle (ORC) uses waste heat or renewable energy as a heat source to convert thermal energy into electrical energy, which is an effective way to improve energy utilization.

Although the traditional organic Rankine cycle system improves energy utilization, the thermal efficiency and net output power of the system are affected by many factors, such as heat source temperature, working fluid, turbine efficiency, etc., so the performance of the system is not stable and superior, and there are Certain limitations.

The evaporator and condenser are the key components of the organic Rankine cycle system, and their temperature changes have a great influence on the system. The evaporation temperature is an important parameter in the organic Rankine cycle system. In the organic Rankine cycle system, the evaporation temperature directly affects the thermodynamic state parameters of the circulating working fluid in the evaporator and expander, and then affects the flow rate of the circulating working fluid, the power consumption of the circulating pump and the enthalpy drop of the unit working fluid in the expander etc., which in turn affects the thermal efficiency and net output power of the system. In a subcritical ORC system, the evaporation temperature is limited by the critical temperature of the working fluid and the inlet temperature of the heat source fluid. When the organic Rankine cycle system is running, if the evaporation temperature is infinitely close to the critical temperature of the working medium, the enthalpy rise in the two-phase region tends to zero, which may cause the flow rate of the working medium to be too large, and the working medium will appear in a wet state in the expander, and the working medium will be stable Sex can also be affected. Therefore, the evaporation temperature is a key factor affecting the system performance and stability.

The condenser is also the key equipment in the organic Rankine cycle system. The condensation temperature is a key factor affecting the pump work consumption in the cooling water cycle. The decrease of the condensation temperature increases the output work of the turbine and the flow of cooling water. increase. The change of condensing temperature also affects the net output work of the system. If the condensing temperature is lower than the optimum condensing temperature, the net output work will drop sharply with the decrease of condensing temperature.

In order to improve the utilization efficiency of waste heat and improve the stability of the organic rankine cycle power generation system, it is necessary to optimize the key operating parameters of the organic rankine cycle system to make the system operate at the best evaporation temperature and the best condensation temperature, and maintain the best operating status, thereby improving the overall performance of the system.

In the existing optimization schemes, it is difficult to manually adjust the parameters and the optimization effect is difficult to achieve the ideal, which cannot fully reflect the system performance. Although the use of algorithms such as genetic algorithms has improved the optimization speed, such algorithms have appeared for a long time. There are defects in the algorithm itself, and the optimization accuracy is not superior enough.

Therefore, there is an urgent need for a new algorithm with fast optimization speed and high accuracy to optimize the parameters of the organic Rankine cycle system, so as to maximize the thermal efficiency and net output power of the power generation system, while meeting the requirements of environmental protection and saving operating costs. Require.

Contents of the invention

Purpose of the invention: Aiming at the problems existing in the prior art, the present invention provides a method for optimizing the temperature of an organic Rankine cycle system with heat conduction oil circulation, which can realize the deep utilization of heat sources, maximize the utilization rate of waste heat and the net output power of the system, Improve overall system performance.

Technical solution: The present invention provides a method for optimizing the temperature of an organic Rankine cycle system with heat transfer oil circulation, comprising the following steps:

Step 1: Obtain the evaporation temperature and condensation temperature of the current evaporator and condenser of the organic Rankine cycle system, and establish a dynamic mathematical model of the evaporator and condenser according to the law of conservation of mass and energy; and initialize the model parameters, which include Population size, maximum number of iterations and dimensions;

Step 2: Use Latin hypercube sampling to initialize the population, determine the convergence factor a and the coefficient vectors A, C, and the convergence factor a is determined by the following formula:

Among them, t _max is the maximum number of iterations;

Step 3: Calculate the fitness value of gray wolf individuals, and save the top three wolves with the best fitness as α, β and δ;

Step 4: Based on the improved position update strategy, the current gray wolf position is updated, and the improved position update strategy is a non-linear improvement to the position update formula;

Step 5: Update a, A and C, calculate the fitness value of all gray wolves, and select n intelligent individuals with the highest fitness;

Step 6: Perform chaotic search on the n intelligent individual populations with the highest fitness, and update the optimal solution α, the optimal solution β and the suboptimal solution δ;

Step 7: Judging whether the maximum number of iterations is reached, if the maximum number of iterations is reached, then output the optimal result and end the optimization process, otherwise return to step 4.

Further, the establishment of the dynamic mathematical model of the evaporator and condenser in the step 1 is based on the following conditions: assuming that the organic working fluid and the cooling water are all in one-dimensional flow in the evaporator and condenser, ignoring the pressure drop and energy In order to avoid the influence of external conditions such as loss, the moving boundary method is used to divide the evaporator into three parts: subcooling zone, two-phase zone and superheating zone, and the refrigerant in the condenser is divided into superheating zone, condensation zone and supercooling zone.

Further, the specific steps of Latin hypercube sampling in the step 2 are as follows:

Step 2.1: Determine the size of the dimension space as N, and divide each dimension into m non-overlapping intervals, so that each interval has the same probability;

Step 2.2: Randomly select a point in each interval in each dimension;

Step 2.3: Randomly extract the points selected in step 2.2 from each dimension, and form them into a vector.

Further, performing chaotic search in step 6 is specifically: using Tent mapping to perform local search optimization, the formula of which is as follows:

In the formula, the value range of x _n is [0,1].

Further, in the step 4, a non-linear improvement is performed on the position update formula, specifically:

Among them, t _max is the maximum number of iterations, X ₁ , X ₂ , and X ₃ are the directions of gray wolf individuals moving toward α, β, and δ, which are three vectors.

Further, the organic Rankine cycle system with heat transfer oil circulation includes an organic Rankine cycle system, a preheating cycle system and a heat transfer oil cycle system, and the preheating cycle system is connected to the organic Rankine cycle system for Preheating the working fluid in the organic Rankine cycle system; the heat transfer oil circulation system is connected to the organic Rankine cycle system, and the heat transfer oil in the heat transfer oil cycle system is heated and sent into the organic Rankine cycle In the system, heat exchange is performed with the working fluid flowing through the organic Rankine cycle system to realize the evaporation of the working fluid.

Further, the organic Rankine cycle system includes an evaporator, an expander, a generator, a condenser, a working medium pump, and a preheater, the evaporator is connected to the expander, and the expander is connected to the power generation The output end of the expander is connected to the condenser, the condenser is connected to the preheater through a working medium pump, the output end of the preheater is connected to the evaporator, and the The preheating circulation system is connected with the preheater, and the heat transfer oil circulation system is connected with the evaporator.

Further, the preheating circulation system is composed of a diesel engine and the preheater, and the preheater is provided with a preheater organic working medium inlet, a preheater organic working medium outlet, a preheater jacket water inlet and Preheater jacket water outlet, the diesel engine is provided with a diesel engine jacket water inlet, a diesel engine jacket water outlet, the diesel engine jacket water outlet is connected to the preheater jacket water inlet, and the preheater jacket water The outlet is connected to the jacket water inlet of the diesel engine; the organic working medium inlet of the preheater is connected to the condenser through the working medium pump; the organic working medium outlet of the preheater is connected to the evaporator.

Further, the heat transfer oil circulation system is composed of a heat exchanger, the evaporator and an oil pump, the heat exchanger is provided with a heat transfer oil inlet of the heat exchanger, and a heat transfer oil outlet of the heat exchanger, and the evaporator is provided with an evaporation The organic working medium inlet of the preheater, the organic working medium outlet of the preheater, the heat transfer oil inlet of the evaporator, and the heat transfer oil outlet of the evaporator; the heat transfer oil inlet of the heat exchanger is connected with the heat transfer oil inlet of the evaporator, and the heat transfer oil of the evaporator The outlet is connected to the heat transfer oil inlet of the heat exchanger through an oil pump; the organic working medium inlet of the evaporator is connected to the organic working medium outlet of the preheater, and the organic working medium outlet of the preheater is connected to the input port of the expander connect.

Further, the diesel engine is also provided with a waste heat flue gas outlet of the diesel engine, and the heat exchanger is also provided with a heat exchanger waste heat flue gas inlet and a heat exchanger waste heat flue gas outlet, and the diesel engine waste heat flue gas outlet is connected to the The waste heat flue gas inlet of the heat exchanger is connected, and the waste heat flue gas outlet of the heat exchanger is directly discharged through the pipeline.

Beneficial effect:

1. The present invention combines the improved gray wolf algorithm to optimize the evaporation temperature and condensation temperature, so that the system can obtain the best operating parameters, improve the thermal efficiency and net output power of the system, and also improve the stability of the system operation and the comprehensive performance of the system Improved.

2. The present invention uses Latin hypercube sampling to initialize the gray wolf population, and Latin hypercube sampling is more efficient than ordinary sampling methods. Latin hypercube sampling has the characteristics of uniform stratification, and can also obtain tail sample values with less sampling, so Latin hypercube sampling is more efficient than ordinary sampling methods.

3. According to the problems of slow convergence speed, instability, and easy to fall into local optimum in the traditional gray wolf algorithm, the present invention uses Tent mapping for local search optimization to improve the accuracy of the algorithm and prevent it from falling into local optimum. The present invention nonlinearizes the position update formula, which balances the global search and local search processes. A nonlinear convergence factor adjustment strategy is designed to accurately reflect the complex pursuit process.

4. Compared with the traditional organic Rankine cycle system, the present invention increases the preheating cycle system and the heat conduction oil cycle system, first utilizes the preheating cycle system to heat the waste heat of the working medium in the organic Rankine cycle system and then enters the evaporator, It is convenient for the evaporation of the working fluid. In addition, by adding a heat transfer oil circulation system, the heated heat transfer oil is used to heat and evaporate the working fluid in the organic Rankine cycle system, so that the organic Rankine cycle system can continue to circulate, which can improve the stability of the power generation system.

5. The jacket water of the diesel engine of the present invention is used to preheat the working medium, which improves the evaporation effect of the working medium in the subsequent link, makes the working medium completely evaporate into high-temperature and high-pressure gas and then enters the expander, and improves the power generation capacity while improving Utilization of low temperature waste heat.

6. The existence of heat transfer oil circulation in the present invention also makes full use of the heat of waste heat flue gas of diesel engine, and the circulation of heat transfer oil in the circuit continuously heats the working medium to make it evaporate completely. The heat transfer oil continuously absorbs the heat of the waste heat flue gas, which not only improves the stability of the vaporization state of the working medium in the organic Rankine cycle, but also improves the system's continuous utilization of waste heat energy, reducing energy waste, and the correlation with the preheating link. Combined to realize the deep utilization of energy.

Description of drawings

Fig. 1 is the organic Rankine system structure schematic diagram that the present invention has heat conduction oil circulation;

Fig. 2 is the algorithm flowchart of the present invention;

Fig. 3 is a comparison chart of primary energy saving rate of the present invention;

Figure 4 is a comparison chart of the thermal efficiency of the cycle of R245fa as the working fluid varies with the temperature of the heat source;

效率随热源温度变化对比图。Figure 5 shows that the working fluid is R245fa cycle

Efficiency versus heat source temperature comparison chart.

Among them, 1 is evaporator, 2 is expander, 3 is generator, 4 is condenser, 5 is working medium pump, 6 is preheater, 7 is oil pump, 8 is heat exchanger, 9 is diesel engine, 11 is 12 is the organic working medium outlet of the evaporator, 13 is the organic working medium inlet of the expander, 14 is the organic working medium outlet of the expander, 15 is the organic working medium inlet of the condenser, and 16 is the organic working medium of the condenser Outlet, 17 is the inlet of preheater organic working fluid, 18 is the outlet of organic working fluid of preheater, 19 is the inlet of evaporator heat transfer oil, 20 is the outlet of evaporator heat transfer oil, 21 is the inlet of heat transfer oil of heat exchanger, 22 is the outlet of heat exchanger The outlet of the heat transfer oil of the heat exchanger, 23 is the inlet of the waste heat flue gas of the heat exchanger, 24 is the outlet of the waste heat flue gas of the heat exchanger, 25 is the inlet of the jacket water of the preheater, 26 is the outlet of the jacket water of the preheater, and 27 is the diesel engine clamp Jacket water inlet, 28 is the jacket water outlet of the diesel engine, and 29 is the waste heat flue gas outlet of the diesel engine. .

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

A method for optimizing the temperature of an organic Rankine cycle system with heat transfer oil circulation proposed by the present invention is realized based on an organic rankine cycle system with heat transfer oil circulation. The specific structure of the system is shown in Figure 1, including the organic rankine cycle Circulation system, preheating circulation system and heat transfer oil circulation system, the preheating circulation system is connected with the organic Rankine cycle system to preheat the working medium in the organic Rankine cycle system; the heat transfer oil circulation system and the organic Rankine cycle The system is connected, and the heat transfer oil in the heat transfer oil circulation system is heated and sent to the organic Rankine cycle system to exchange heat with the working fluid flowing through the organic Rankine cycle system to realize the evaporation of the working fluid. The preheating circulation system is also connected with the heat transfer oil circulation system, and the preheating circulation system provides waste heat for the connection of the heat transfer oil circulation system, and heats the heat transfer oil in the heat transfer oil circulation system.

It specifically includes an evaporator 1, an expander 2, a generator 3, a condenser 4, a working medium pump 5, a preheater 6, an oil pump 7, a heat exchanger 8, and a diesel engine 9. The heat transfer oil circulation system is composed of a heat exchanger 8 , an evaporator 1 and an oil pump 7 , and the preheating circulation system is composed of a diesel engine 9 and a preheater 6 .

The evaporator 1 is provided with an evaporator organic working medium inlet 11 , an evaporator organic working medium outlet 12 , an evaporator heat transfer oil inlet 19 and an evaporator heat transfer oil outlet 20 .

The expander 2 is provided with an expander organic working medium inlet 13 and an expander organic working medium outlet 14 .

The condenser 4 is provided with a condenser organic working medium inlet 15 and a condenser organic working medium outlet 16 .

The preheater 6 is provided with a preheater organic working medium inlet 17 , a preheater organic working medium outlet 18 , a preheater jacket water inlet 25 and a preheater jacket water outlet 26 .

The heat exchanger 8 is provided with a heat transfer oil inlet 21 , a heat transfer oil outlet 22 , a waste heat flue gas inlet 23 of the heat exchanger, and a waste heat flue gas outlet 24 of the heat exchanger.

The diesel engine 9 is provided with a diesel engine jacket water inlet 27 , a diesel engine jacket water outlet 28 and a diesel engine waste heat flue gas outlet 29 .

In the organic Rankine link, the evaporator organic working medium outlet 12 of the evaporator 1 is connected to the expander organic working medium inlet 13 of the expander 2, and the expander organic working medium outlet 14 is connected to the condenser organic working medium inlet 15, condensing The organic working medium outlet 16 of the machine is connected to the input end of the working medium pump 5, the output end of the working medium pump 5 is connected to the organic working medium inlet 17 of the preheater, and the organic working medium outlet 18 of the preheater is connected to the organic working medium inlet 11 of the evaporator.

The working medium evaporates in the evaporator 1 into a high-temperature and high-pressure gas, flows out through the outlet 12 of the organic working medium of the evaporator, enters the expander 2 to do work, and the generator 3 performs power generation. The working medium flows out from the organic working medium outlet 14 of the expander 2, and enters the condenser 4 through the organic working medium inlet 15 of the condenser. . The organic working medium outlet 16 of the condenser is connected to the organic working medium inlet 17 of the preheater, and a working medium pump 5 is connected between the two. Provide power. The working fluid enters the preheater 6 from the organic working medium inlet 17 of the preheater. After being preheated by the heat source, it flows out through the organic working medium outlet 18 of the preheater and is sent to the evaporator organic working medium inlet 11 of the evaporator 1. In the evaporator 1, it is evaporated by the heat source into a high-temperature and high-pressure gas, and enters the expander 2 through the organic working medium outlet 12 of the evaporator, thereby completing the organic Rankine cycle.

In the preheating cycle link, the preheating cycle is composed of a diesel engine 9 and a preheater 6. The jacket water outlet 28 of the diesel engine is connected with the jacket water inlet 25 of the preheater. The jacket water flows out from the jacket water outlet 28 of the diesel engine and is preheated The jacket water inlet 25 of the heater flows into the preheater 6 to preheat the working fluid passing through it. After the preheating is completed, the jacket water flows out through the jacket water outlet 26 of the preheater and then enters the diesel engine through the jacket water inlet 27 of the diesel engine to cool the diesel engine, thereby completing the preheating cycle.

In the heat transfer oil cycle link, the heat transfer oil cycle includes a heat exchanger 8, an evaporator 1, and an oil pump 7. The diesel engine waste heat flue gas outlet 29 of the diesel engine 9 is connected to the heat exchanger waste heat flue gas inlet 23, and the heat transfer oil outlet of the heat exchanger is connected to the evaporation The heat transfer oil inlet of the evaporator is connected to the heat transfer oil inlet of the evaporator, and the heat transfer oil outlet 20 of the evaporator is connected to the heat transfer oil inlet of the heat exchanger, and an oil pump 7 is connected between the two.

The medium and low temperature waste heat exhaust gas discharged from the diesel engine 9 is discharged from the waste heat exhaust gas outlet 29 of the diesel engine, and sent to the heat exchanger 8 through the waste heat exhaust gas inlet 23 of the heat exchanger, and is heated by the heat transfer oil flowing through the heat exchanger 8. The waste heat flue gas outlet 24 of the heat exchanger is discharged. After being heated in the heat exchanger 8, the heat transfer oil flows out through the heat transfer oil outlet 22 of the heat exchanger, enters the evaporator 1 through the heat transfer oil inlet 19 of the evaporator, and exchanges heat with the working fluid passing through here, so as to realize the qualitative evaporation. The heat transfer oil flows out of the evaporator 1 through the heat transfer oil outlet 20 of the evaporator, is pressurized by the oil pump 7, and returns to the heat exchanger 8 through the heat transfer oil inlet 21 of the heat exchanger, and continues to exchange heat with the waste heat flue gas. The heat transfer oil outlet 22 of the heat exchanger flows out, and enters the evaporator 1 through the heat transfer oil inlet 19 of the evaporator, thereby realizing the heat transfer oil circulation.

When the present invention is in use, the jacket water discharged from the diesel engine firstly preheats the working medium in the organic Rankine cycle, and the exhausted waste heat flue gas is circulated through the heat conduction oil to realize the evaporation of the working medium flowing out of the preheater. The working medium enters the expander for power generation, and after being condensed by the condenser, the working medium is pressurized by the working medium pump, and finally returns to the preheater for preheating, and thus circulates.

For the above-mentioned organic Rankine cycle system with heat transfer oil circulation, during the working process, the change of the evaporation temperature and condensation temperature of the evaporator 1 and the condenser 4 has a great influence on the system. The evaporation temperature directly affects the thermodynamic state parameters of the circulating working fluid in the evaporator and expander, which in turn affects the flow rate of the circulating working fluid, the power consumption of the circulating pump, and the enthalpy drop of the unit working fluid in the expander, etc., which in turn affects the thermal efficiency and efficiency of the system. net output power. Condensation temperature is a key factor affecting pump work consumption in cooling water circulation. The decrease of condensing temperature will increase the output work of turbine and the flow rate of cooling water, which will lead to the increase of circulating water pump work. The change of condensing temperature also affects the net output work of the system. If the condensing temperature is lower than the optimum condensing temperature, the net output work will drop sharply with the decrease of condensing temperature. In order to improve the utilization efficiency of waste heat and improve the stability of the organic rankine cycle power generation system, it is necessary to optimize the key operating parameters of the organic rankine cycle system to make the system operate at the best evaporation temperature and the best condensation temperature, and maintain the best operating status, thereby improving the overall performance of the system.

The invention discloses a method for optimizing the temperature of an organic Rankine cycle system with heat conduction oil circulation, which mainly includes the following steps:

Step 1: Obtain the current evaporation temperature and condensation temperature of the evaporator 1 and condenser 4 of the organic Rankine cycle system, and establish a dynamic mathematical model of the evaporator 1 and condenser 4 according to the law of conservation of mass and energy; and initialize the model parameters , the parameters include population size, maximum number of iterations and dimensions. The establishment of the dynamic mathematical model of the evaporator and condenser is based on the following conditions: Assume that the organic working medium and cooling water are both in one-dimensional flow in the evaporator 1 and condenser 4, ignoring the influence of external conditions such as pressure drop and energy loss , using the moving boundary method, the evaporator 1 is divided into three parts: a subcooling zone, a two-phase zone and a superheating zone, and the refrigerant in the condenser 4 is divided into a superheating zone, a condensation zone and a supercooling zone.

Step 2: Use Latin hypercube sampling to initialize the population, and determine the convergence factor a and coefficient vectors A and C.

When |A|>1, the gray wolf group will expand the encirclement to find better prey, which corresponds to the global search; when |A|<1, the gray wolf group will shrink the encirclement to complete the final search for the prey. The attack behavior at this time corresponds to local search. The value of A has a great relationship with the global search and local search capabilities of the GWO algorithm. A changes continuously with the change of the convergence factor a, and the convergence factor a decreases linearly from 2 to 0 as the number of iterations increases. But in the actual search process, the linear reduction of a cannot accurately reflect the complex pursuit process at all. Therefore, the present invention designs a nonlinear convergence factor adjustment strategy,

The convergence factor a is determined by the following formula:

Among them, t _max is the maximum number of iterations.

The specific steps of Latin hypercube sampling are as follows:

Step 2.1: Determine the size of the dimension space as N, and divide each dimension into m non-overlapping intervals, so that each interval has the same probability;

Step 2.2: Randomly select a point in each interval in each dimension;

Step 2.3: Randomly extract the points selected in step 2.2 from each dimension, and form them into a vector.

Step 3: Calculate the fitness value of gray wolf individuals, and save the top three wolves with the best fitness as α, β and δ.

Step 4: Based on the improved position update strategy, the current gray wolf position is updated. The improved position update strategy is a non-linear improvement of the position update formula.

A non-linear improvement is made to the position update formula, specifically:

Among them, t _max is the maximum number of iterations, X ₁ , X ₂ , and X ₃ are the directions of gray wolf individuals moving toward α, β, and δ, which are three vectors.

Step 5: Update a, A and C, calculate the fitness value of all gray wolves, and select n intelligent individuals with the highest fitness.

Step 6: Perform chaotic search on the n intelligent individual populations with the highest fitness, and update the optimal solution α, the optimal solution β and the suboptimal solution δ.

Using Tent mapping for local search optimization, the formula is as follows:

In the formula, the value range of x _n is [0,1].

Step 7: Judging whether the maximum number of iterations is reached, if the maximum number of iterations is reached, then output the optimal result and end the optimization process, otherwise return to step 4.

The simulation effects of Fig. 3 to Fig. 5 are explained as follows:

It can be seen from Figure 3 that compared with the traditional organic Rankine system, the energy saving rate of the improved organic Rankine cycle system can be increased by about 5% when the operation time is 12 hours.

效率得到提升，且随着热源温度的升高而升高，热源温度为450K时性能最优。It can be seen from Figure 4 and Figure 5 that: compared with the unimproved system, the thermal efficiency and

The efficiency is improved and increases with the temperature of the heat source, and the performance is optimal when the temperature of the heat source is 450K.

The above-mentioned embodiments are only for illustrating the technical concept and characteristics of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. The temperature optimization method of the organic Rankine cycle system with the heat conduction oil cycle is characterized by comprising the following steps of:

step 1: acquiring the evaporation temperature and the condensation temperature of a current evaporator and a current condenser of the organic Rankine cycle system, and establishing a dynamic mathematical model of the evaporator and the condenser according to a mass energy conservation law; initializing model parameters, wherein the parameters comprise population size, maximum iteration times and dimensionality;

step 2: initializing the population using latin hypercube sampling, determining a convergence factor a and a coefficient vector A, C, said convergence factor a being determined by the following equation:

wherein, t _max Is the maximum iteration number;

and 3, step 3: calculating the fitness value of the wolf individual, and storing the first 3 wolfs with the best fitness as alpha, beta and delta;

and 4, step 4: updating the current grey wolf position based on an improved position updating strategy, wherein the improved position updating strategy is to perform nonlinear improvement on a position updating formula;

and 5: updating a, A and C, calculating the fitness values of all wolfs, and selecting n intelligent individuals with the front fitness;

step 6: performing chaotic search on n intelligent individual populations with the former fitness, and updating an optimal solution alpha, an optimal solution beta and a suboptimal solution delta;

and 7: and (4) judging whether the maximum iteration times is reached, if so, outputting an optimal result, and ending the optimization process, otherwise, returning to the step (4).

2. The method for optimizing the temperature of the organic Rankine cycle system with the conduction oil cycle according to claim 1, wherein the step 1 of establishing the dynamic mathematical model of the evaporator and the condenser is based on the following conditions: assuming that the organic working medium and the cooling water flow in one dimension in the evaporator and the condenser, neglecting the influence of external conditions such as pressure drop, energy loss and the like, a moving boundary method is adopted to divide the evaporator into an supercooling zone, a two-phase zone and a superheating zone, and divide the refrigerant into the superheating zone, a condensation zone and the supercooling zone in the condenser.

3. The temperature optimization method for the organic Rankine cycle system with the conduction oil cycle as claimed in claim 1, wherein the specific steps of Latin hypercube sampling in the step 2 are as follows:

step 2.1: determining the space of dimension as N, and dividing each dimension into m intervals which are not overlapped with each other, so that each interval has the same probability;

step 2.2: randomly extracting a point in each interval in each dimension;

step 2.3: the points selected in step 2.2 are then randomly extracted from each dimension and grouped into vectors.

4. The method for optimizing the temperature of the organic Rankine cycle system with the conduction oil cycle according to claim 1, wherein the chaotic search in the step 6 specifically comprises the following steps: local search optimization is carried out by using Tent mapping, and the formula is as follows:

in the formula, x _n Has a value range of [0,1]。

5. The temperature optimization method for the organic Rankine cycle system with the conduction oil cycle as claimed in claim 4, wherein the step 4 is to perform nonlinear improvement on a position updating formula, and specifically comprises the following steps:

wherein, t _max Is the maximum number of iterations, X ₁ 、X ₂ 、X ₃ Is the direction in which the wolf individual advances toward alpha, beta and delta, and is three vectors.

6. The method for optimizing the temperature of the organic Rankine cycle system with the conduction oil cycle according to any one of claims 1 to 5, wherein the organic Rankine cycle system with the conduction oil cycle comprises an organic Rankine cycle system, a preheating cycle system and a conduction oil cycle system, and the preheating cycle system is connected with the organic Rankine cycle system and used for preheating working media in the organic Rankine cycle system; the heat conduction oil circulation system is connected with the organic Rankine circulation system, heat conduction oil in the heat conduction oil circulation system is heated and then sent into the organic Rankine circulation system to exchange heat with working media flowing through the organic Rankine circulation system, and therefore evaporation of the working media is achieved.

7. The temperature optimization method of the organic Rankine cycle system with the conduction oil cycle is characterized in that the organic Rankine cycle system comprises an evaporator (1), an expander (2), a generator (3), a condenser (4), a working medium pump (5) and a preheater (6), wherein the evaporator (1) is connected with the expander (2), the expander (2) is connected with the generator (3), the output end of the expander (2) is connected with the condenser (4), the condenser (4) is connected with the preheater (6) through the working medium pump (5), the output end of the preheater (6) is connected with the evaporator (1), the preheating cycle system is connected with the preheater (6), and the conduction oil cycle system is connected with the evaporator (1).

8. The temperature optimization method of the organic Rankine cycle system with the conduction oil cycle according to claim 7, wherein the preheating cycle system consists of a diesel engine (9) and the preheater (6), the preheater (6) is provided with a preheater organic working medium inlet (17), a preheater organic working medium outlet (18), a preheater jacket water inlet (25) and a preheater jacket water outlet (26), the diesel engine (9) is provided with a diesel jacket water inlet (27) and a diesel jacket water outlet (28), the diesel jacket water outlet (28) is connected with the preheater jacket water inlet (25), and the preheater jacket water outlet (26) is connected with the diesel jacket water inlet (27); the organic working medium inlet (17) of the preheater is connected with the condenser (4) through the working medium pump (5); the organic working medium outlet (18) of the preheater is connected with the evaporator (1).

9. The temperature optimization method for the organic Rankine cycle system with a thermal oil cycle according to claim 8, wherein the thermal oil cycle system is composed of a heat exchanger (8), the evaporator (1) and an oil pump (7), the heat exchanger (8) is provided with a heat exchanger thermal oil inlet (21) and a heat exchanger thermal oil outlet (22), the evaporator (1) is provided with an evaporator organic working medium inlet (11), a preheater organic working medium outlet (18), an evaporator thermal oil inlet (19) and an evaporator thermal oil outlet (20); the heat conducting oil inlet (21) of the heat exchanger is connected with the heat conducting oil inlet (19) of the evaporator, and the heat conducting oil outlet (20) of the evaporator is connected with the heat conducting oil inlet (21) of the heat exchanger through an oil pump (7); the organic working medium inlet (11) of the evaporator is connected with the organic working medium outlet (18) of the preheater, and the organic working medium outlet (18) of the preheater is connected with the input end of the expansion machine (2).

10. The temperature optimization method of the organic Rankine cycle system with the conduction oil cycle as claimed in claim 9, wherein the diesel engine (9) is further provided with a diesel engine waste heat flue gas outlet (29), the heat exchanger (8) is further provided with a heat exchanger waste heat flue gas inlet (23) and a heat exchanger waste heat flue gas outlet (24), the diesel engine waste heat flue gas outlet (29) is connected with the heat exchanger waste heat flue gas inlet (23), and the heat exchanger waste heat flue gas outlet (24) is directly discharged through a pipeline.

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