CN113343405B - Optimization design method of three-sleeve phase-change heat storage heat exchange unit - Google Patents
Optimization design method of three-sleeve phase-change heat storage heat exchange unit Download PDFInfo
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Abstract
The invention discloses an optimal design method of a three-sleeve phase-change heat storage heat exchange unit, which comprises the following steps: 1. determining an optimization variable and an optimization objective function; the optimization variable is the radius of the inner tube, the sleeve and the outer tube; the optimization objective function is: a heat exchange efficiency function, a time efficiency function and a quality function; 2. selecting a group intelligent optimization algorithm according to the requirements of an optimization objective function and computer configuration conditions; 3. determining the latent heat storage capacity S of the heat exchange unit according to the load requirement of a user side and site conditions; then determining the upper limit and the lower limit of the optimization variable; 4. determining an optimized variable constraint condition meeting the actual requirement according to the requirement of a user load side; 5. and optimizing an objective function through a group intelligent optimization algorithm to obtain the optimal set of the optimization variables Pareto. The technical scheme can overcome the limitations of low heat exchange efficiency, long heat storage time and heavy body size of the existing three-sleeve phase-change heat storage and exchange unit, and improves the comprehensive performance of the three-sleeve phase-change heat storage and exchange unit.
Description
Technical Field
The invention belongs to the technical field of chemical machinery, and particularly relates to an optimal design method of a three-sleeve phase-change heat storage heat exchange unit.
Background
With the increasing problems of warming climate and energy shortage, the utilization of renewable energy sources such as solar energy and wind energy is becoming more and more trend. However, the renewable energy has the disadvantages of intermittency, instability, large fluctuation, uneven regional distribution and the like, and the development of the renewable energy is greatly limited. The energy storage technology can store energy when the energy supply quantity is larger than the demand quantity, and release energy when the output quantity does not meet the demand quantity so as to match the balance problem of the supply and demand sides. Therefore, a phase change latent heat storage system with high energy storage density and constant temperature in the heat storage process becomes a popular target for researching energy storage technology. At present, phase change heat exchangers of different structural forms, such as sleeve type, shell and tube type, packing type, etc., have been developed.
The three-sleeve phase-change heat exchanger has attracted extensive attention due to its characteristics of large heat exchange area, high heat storage performance, good economy and the like. At present, the research aiming at the three-sleeve type phase change latent heat storage system is mainly carried out on the following aspects: the phase-change material selection, the phase-change material melting and solidification process characteristic research and the heat exchange enhancement technology are lack of optimization of the structure forms such as the pipe diameter and the pipe length.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides an optimal design method of a three-sleeve phase-change heat storage and exchange unit, can overcome the limitations of low heat exchange efficiency, long heat storage time and heavy body size of the conventional three-sleeve phase-change heat storage and exchange unit, provides an optimal design method of the three-sleeve phase-change heat storage and exchange unit, and improves the comprehensive performance of the three-sleeve phase-change heat storage and exchange unit.
The invention is realized by the following technical scheme:
an optimal design method of a three-sleeve phase-change heat storage heat exchange unit comprises the following steps:
step one, determining an optimization variable and an optimization objective function; the optimized variable is the radius r of the inner pipe, the sleeve and the outer pipe of the three-sleeve phase-change heat storage heat exchange unit1，r2，r3(ii) a The optimization objective function is: a heat exchange efficiency function, a time efficiency function and a quality function;
the heat exchange efficiency function is defined as follows:
s is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, Q is the heat (kJ) input by the heat exchange fluid, and W is the power consumption (kJ) of the water pump for overcoming the resistance loss of the three-sleeve phase-change heat storage and exchange unit;
the time efficiency function is defined as follows:
s is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, and t is the time for completing the latent heat storage process;
the quality function is:
wherein r is1，r2，r3The diameters (m) of the inner pipe, the sleeve and the outer pipe respectively, delta is the wall thickness (m), L is the length of the three-sleeve phase-change heat storage and exchange unit, and rhoMIs the density (kg/m) of the pipe3) S is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, and H is the phase-change latent heat (kJ/kg) of the phase-change material;
selecting a proper group intelligent optimization algorithm according to the requirements of an optimization objective function and computer configuration conditions;
preferably, the group intelligence optimization algorithm may be: a multi-target genetic algorithm NSGA-II, a multi-target particle swarm algorithm MOPSO, a multi-target artificial bee colony algorithm MOABC and a multi-target ant colony algorithm MOACA;
determining the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit according to the load requirement of the user side and the site condition; then determining the upper limit and the lower limit of an optimized variable according to the latent heat storage capacity S;
preferably, the first and second electrodes are formed of a metal,
when S is less than or equal to 800kJ, r is more than or equal to 0.0081≤0.015，0.037≤r2≤0.045，0.044≤r3≤0.060；
When 800<When S is less than or equal to 1000kJ, r is more than or equal to 0.0081≤0.020，0.040≤r2≤0.050，0.048≤r3≤0.065；
When 1000<When S is less than or equal to 1500kJ, r is less than or equal to 0.0101≤0.023，0.045≤r2≤0.055，0.050≤r3≤0.065；
When 1500<When S is less than or equal to 2000kJ, r is more than or equal to 0.0121≤0.028，0.050≤r2≤0.065，0.055≤r3≤0.075；
And step four, determining an optimized variable constraint condition meeting the actual requirement according to the requirement of the user load side.
The constraint may be: the length L of the three-sleeve phase-change heat storage and exchange unit, the time T for completing the latent heat storage process, the power consumption W of the water pump for overcoming the resistance loss of the phase-change heat exchange unit, and the temperature difference delta T between the inlet and the outlet of the heat exchange fluid flowing through the inner pipe and the outer pipe1,ΔT2；
And fifthly, optimizing an objective function through the selected group intelligent optimization algorithm to obtain the optimized variable Pareto optimal set.
In the above technical solution, the heat input by the Q heat exchange fluid of the heat exchange efficiency function is calculated by the following method:
Q＝Q1+Q2＝cpt(ms1ΔT1+ms2ΔT2)
wherein, cpM is the specific heat capacity of the heat exchange fluids1,ms2Mass flow, Δ T, of the inner and outer tubes, respectively1,ΔT2The temperature difference of the heat exchange fluid flowing through the inlet and the outlet of the inner pipe and the outer pipe is respectively.
In the above technical solution, t is the time for completing the latent heat storage process, and the determining method is as follows:
wherein, lambda is the heat conductivity coefficient of the phase change material, w/(m.k), TinFor the inlet temperature, T, of the heat-exchange fluidpFor the phase change temperature of the phase change material, DEG C, hd is the thickness of the phase change material layer, and the value is the solution satisfying the following equation:
in the above technical solution, the Δ T1,ΔT2Calculated in the following manner, respectively:
ΔT1＝Tin-Tp-ΔTp1
wherein, Delta Tp1Is a three-sleeve phase-change heat storage and exchangeThe temperature difference between the heat exchange fluid at the outlet of the inner tube of the unit and the phase-change material in the latent heat storage process is expressed as,
ΔT2＝Tin-Tp-ΔTp2
wherein, Delta Tp2The temperature difference between the heat exchange fluid at the outlet of the outer pipe of the three-sleeve phase-change heat storage and exchange unit and the phase-change material in the latent heat storage process is expressed as,
in the technical scheme, L is the tube length of the three-sleeve phase-change heat storage and exchange unit, and the expression is
Wherein S is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, H is the phase-change latent heat (kJ/kg) of the phase-change material, and rhobIs a modified density (kg/m) of the phase change material taking into account natural convection3)，r1,r2The radius (m) of the inner pipe and the radius (m) of the sleeve of the three-sleeve phase-change heat storage heat exchange unit are respectively, and delta is the wall thickness (m).
In the technical scheme, the power consumption W of the water pump for overcoming the resistance loss of the three-sleeve phase-change heat storage heat exchange unit is calculated by the following method:
W＝W1+W2
W1＝πr1 2u1Δp1t
W2＝π(r3 2-r2 2)u2Δp2t
wherein u is1,u2Phase change of three sleeves respectivelyThe flow velocity of the heat exchange fluid in the inner tube and the outer tube of the heat storage and exchange unit, Δ p is the resistance loss of the heat exchange fluid flowing through the inner tube and the outer tube, and can be calculated as follows:
in the case of the inner tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
dh＝2r1
in the case of the outer tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
ξ＝[1.8log10(φRe)-1.5]-2
dh＝2(r3-r2)。
the invention has the advantages and beneficial effects that:
the comprehensive performance evaluation of the three-sleeve phase-change heat storage and exchange unit is carried out by applying a plurality of angles, and mainly relates to the three aspects of heat storage efficiency, time efficiency and self quality of the phase-change heat exchange unit. The application group intelligent algorithm aims at three functions of heat storage efficiency, time efficiency and quality, multi-objective optimization is carried out on the structural size of the three-sleeve phase-change heat storage and exchange unit, the comprehensive performance of the three-sleeve phase-change heat storage and exchange unit can be effectively improved, and the application group intelligent algorithm has great significance for the application of the three-sleeve phase-change heat storage and exchange unit and the efficient utilization of energy.
According to the technical scheme, mathematical expressions of heat exchange efficiency, time efficiency and quality of the three-sleeve phase-change heat exchange unit with the inner pipe, the sleeve pipe and the outer pipe of the three-sleeve phase-change heat storage heat exchange unit as independent variables are determined, a Pareto optimal set is obtained through a multi-objective group intelligent optimization algorithm, selection basis is provided for determination of the pipe diameters r1, r2 and r3 of the inner pipe, the sleeve pipe and the outer pipe of the three-sleeve phase-change heat storage heat exchange unit, and a user can select an optimal size meeting requirements according to actual requirements and personal preference. The three-sleeve phase-change heat exchange unit has the advantages that the quality of the three-sleeve phase-change heat exchange unit is enabled to be as small as possible, the heat exchange efficiency of the three-sleeve phase-change heat exchange unit is improved, the phase-change heat storage time is shortened, the comprehensive performance of the three-sleeve phase-change heat storage heat exchange unit is improved, the practicability is increased, and the popularization of a phase-change energy-saving technology is facilitated.
Drawings
Fig. 1 is a schematic structural diagram of a three-sleeve phase-change heat storage heat exchange unit.
Fig. 2 is a cross-sectional view of a three-sleeve phase-change thermal storage heat exchange unit.
Wherein:
1: inner tube, 2: sleeve, 3: an outer tube.
For a person skilled in the art, without inventive effort, other relevant figures can be derived from the above figures.
Detailed Description
In order to make the technical solution of the present invention better understood, the technical solution of the present invention is further described below with reference to specific examples.
Example one
The optimal design method of the three-sleeve phase-change heat storage heat exchange unit comprises the following steps:
step one, influence fromAnd selecting an optimization variable and an optimization target from the structural parameters of the comprehensive performance of the three-sleeve phase-change heat storage heat exchange unit. Selecting the pipe diameters r of the inner pipe, the sleeve and the outer pipe of the three-sleeve phase-change heat storage and exchange unit1，r2，r3As optimization variables. Determining an optimized objective function as: heat exchange efficiency, time efficiency and quality.
The heat exchange efficiency of the objective function 1 is defined as follows:
s is latent heat storage capacity (kJ) of the phase change heat exchange unit, and in this embodiment, the latent heat storage capacity S of the three-tube phase change heat storage heat exchange unit to be optimized at this time is determined to be 700kJ according to the heat storage capacity of the three-tube phase change heat storage heat exchange unit before optimization. Q is the heat (kJ) input by the heat exchange fluid, and W is the power consumption (kJ) of the water pump for overcoming the resistance loss of the phase change heat exchange unit.
The method for determining the heat input Q of the heat exchange fluid comprises the following steps:
Q＝Q1+Q2＝cpt(ms1ΔT1+ms2ΔT2)
wherein, cpThe specific heat capacity of the heat exchange fluid is 4.182 kJ/(kg. K), ms1,ms2The mass flow rates of the inner pipe and the outer pipe are respectively 0.2775kg/s and delta T1,ΔT2The temperature difference of the heat exchange fluid flowing through the inlet and the outlet of the inner pipe and the outer pipe is respectively, the temperature is DEG C, and t is the time for completing the latent heat storage process, s.
The method for determining the time t for completing the latent heat storage process is as follows:
wherein, lambda is the heat conductivity coefficient of the phase change material and is taken as 0.2 w/(m.k), TinTo the inlet temperature, T, of the heat exchange fluidpTaking the phase change latent heat of the phase change material as 168kJ/kg at the temperature of DEG C and HbIs a corrected density, rho, of the phase change material taking into account natural convectionb＝ρP(1-β(Tin-TP) Where ρ isP＝867kg/m3，β＝0.76×10-3，Tin＝65℃,TPHd is the thickness of the phase change material layer at 50 ℃, which is a value that satisfies the following equation:
inlet and outlet temperature difference delta T of heat exchange fluid1,ΔT2The determination method of (2) is as follows:
ΔT1＝Tin-Tp-ΔTp1
wherein, Delta Tp1The temperature difference between the heat exchange fluid at the outlet of the inner tube of the three-sleeve phase-change heat exchanger and the phase-change material in the latent heat storage process is expressed as follows,
ΔT2＝Tin-Tp-ΔTp2
wherein, Delta Tp2The temperature difference between the heat exchange fluid at the outlet of the outer pipe of the three-sleeve phase-change heat exchanger and the phase-change material in the latent heat storage process is expressed as follows,
l is the tube length of the three-sleeve phase-change heat storage heat exchange unit
The method for determining the power consumption W of the water pump for overcoming the resistance loss of the phase-change heat exchange unit comprises the following steps:
W＝W1+W2
W1＝πr1 2u1Δp1t
W2＝π(r3 2-r2 2)u2Δp2t
wherein u is1,u2The flow rates of the heat exchange fluid in the inner tube and the outer tube, respectively, and Δ p is the resistance loss of the heat exchange fluid flowing through the inner tube and the outer tube, which can be calculated as follows:
In the case of the inner tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
dh＝2r1
in the case of the outer tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
ξ＝[1.8log10(φRe)-1.5]-2
dh＝2(r3-r2)
the time efficiency of the objective function 2 is defined as the ratio of the latent heat storage amount to the heat storage time, and is expressed as:
wherein S is the latent heat storage capacity (kJ) of the phase change heat exchange unit, and t is the time for completing the latent heat storage process.
The target function 3 is that the quality of the three-sleeve phase-change heat exchange unit is as follows:
wherein r is1，r2，r3The pipe diameters (m) of the inner pipe, the sleeve and the outer pipe, respectively, delta is the wall thickness (m), L is the pipe length, rhoMIs the density (kg/m) of the pipe3)，ρM＝8930kg/m3In this embodiment, the phase change material is paraffin, and H is a phase change latent heat of the phase change material taken as 168 kJ/kg.
And step two, selecting a proper group intelligent optimization algorithm according to the requirements of the optimization objective function and the configuration conditions of the computer. The optimization algorithm selected in the embodiment is a multi-objective genetic algorithm NSGA-II, the initial population size is set to be 100, the iteration times are set to be 200, and the optimized individual coefficient is set to be 0.7;
and step three, determining the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit according to the load requirement of the user side and the site condition. And then determining the upper limit and the lower limit of the optimized variable according to the latent heat storage capacity S. In this embodiment, the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit to be optimized at this time is determined to be 700kJ according to the heat storage capacity of the three-sleeve phase-change heat storage heat exchange unit before optimization. According to the latent heat storage capacity, the upper limit and the lower limit of the optimization variable are determined to be r which is more than or equal to 0.0081≤0.015，0.037≤r2≤0.045，0.044≤r3≤0.060。
And step four, determining an optimized variable constraint condition meeting the actual requirement according to the requirement of the user load side. The constraint conditions determined by the embodiment are the length of the three-sleeve phase-change heat storage and exchange unit, L is less than or equal to 1.5m, the time for completing the latent heat storage process, and t is less than or equal to 6000 s.
And step five, optimizing the objective function through the group intelligent optimization algorithm selected in the step two to obtain a Pareto optimal set.
Thus, 70 Pareto optimal solutions meeting the constraint condition are obtained. The user can select a Pareto optimal solution as the final optimal size according to actual requirements or personal preference setting. It can be seen that the Pareto optimal set can be obtained through the group intelligent optimization algorithm by determining the latent heat storage capacity of the three-sleeve phase-change heat storage heat exchange unit according to the actual load demand and selecting appropriate upper and lower limits and constraint conditions. The method is simple and easy to implement, occupies less computer resources and has low time cost.
Example two
An optimal design method of a three-sleeve phase-change heat storage heat exchange unit comprises the following steps:
step one, selecting an optimization variable and an optimization target from structural parameters influencing the comprehensive performance of the three-sleeve phase-change heat storage heat exchange unit. Selecting the pipe diameters r of the inner pipe, the sleeve and the outer pipe of the three-sleeve phase-change heat storage and exchange unit1，r2，r3As optimization variables. Determining an optimized objective function as: heat exchange efficiency, time efficiency and quality.
The heat exchange efficiency of the objective function 1 is defined as follows:
s is latent heat storage capacity (kJ) of the phase-change heat exchange unit, and in this embodiment, the latent heat storage capacity S of the three-tube phase-change heat storage heat exchange unit to be optimized at this time is determined to be 1200kJ according to the heat storage capacity of the three-tube phase-change heat storage heat exchange unit before optimization. Q is the heat (kJ) input by the heat exchange fluid, and W is the power consumption (kJ) of the water pump for overcoming the resistance loss of the phase-change heat exchange unit.
The method for determining the heat input Q of the heat exchange fluid comprises the following steps:
Q＝Q1+Q2＝cpt(ms1ΔT1+ms2ΔT2)
wherein, cpThe specific heat capacity of the heat exchange fluid is 4.182 kJ/(kg. K), ms1,ms2The mass flow rates of the inner pipe and the outer pipe are respectively 0.1kg/s and 0.3kg/s, and delta T1,ΔT2The temperature difference of the heat exchange fluid flowing through the inlet and the outlet of the inner pipe and the outer pipe is respectively, the temperature is DEG C, and t is the time for completing the latent heat storage process, and s.
The method for determining the time t for completing the latent heat storage process is as follows:
wherein, lambda is the heat conductivity coefficient of the phase change material and is taken as 0.2 w/(m.k), TinFor the inlet temperature, T, of the heat-exchange fluidpTaking the phase change latent heat of the phase change material as 168kJ/kg at the temperature of DEG C and HbIs a corrected density, rho, of the phase change material taking into account natural convectionb＝ρP(1-β(Tin-TP) Where ρ isP＝867kg/m3，β＝0.76×10-3，Tin＝65℃,TPHd is the thickness of the phase change material layer at 50 deg.c, which is a value that satisfies the following equation:
inlet and outlet temperature difference delta T of heat exchange fluid1,ΔT2The determination method of (2) is as follows:
ΔT1＝Tin-Tp-ΔTp1
wherein, Delta Tp1The temperature difference between the heat exchange fluid at the outlet of the inner tube of the three-sleeve phase-change heat exchanger and the phase-change material in the latent heat storage process is expressed as follows,
ΔT2＝Tin-Tp-ΔTp2
wherein, Delta Tp2The temperature difference between the heat exchange fluid at the outlet of the outer pipe of the three-sleeve phase-change heat exchanger and the phase-change material in the latent heat storage process is expressed as follows,
l is the tube length of the three-sleeve phase-change heat storage heat exchange unit
The method for determining the power consumption W of the water pump for overcoming the resistance loss of the phase-change heat exchange unit comprises the following steps:
W＝W1+W2
W1＝πr1 2u1Δp1t
W2＝π(r3 2-r2 2)u2Δp2t
wherein u is1,u2The flow rates of the heat exchange fluid in the inner tube and the outer tube, respectively, and Δ p is the resistance loss of the heat exchange fluid flowing through the inner tube and the outer tube, which can be calculated as follows:
In the case of the inner tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
dh＝2r1
in the case of the outer tube, it is,
when the flow is laminar flow (Re. ltoreq.2100),
when the flow is turbulent (Re >2100),
ξ＝[1.8log10(φRe)-1.5]-2
dh＝2(r3-r2)
the time efficiency of the objective function 2 is defined as the ratio of the latent heat storage amount to the heat storage time, and is expressed as:
wherein S is the latent heat storage capacity (kJ) of the phase change heat exchange unit, and t is the time for completing the latent heat storage process.
The target function 3 is that the quality of the three-sleeve phase-change heat exchange unit is as follows:
wherein r is1，r2，r3The pipe diameters (m) of the inner pipe, the sleeve and the outer pipe, respectively, delta is the wall thickness (m), L is the pipe length, rhoMIs the density (kg/m) of the pipe3)，ρM＝8930kg/m3In this embodiment, the phase change material is paraffin, and H is a phase change latent heat of the phase change material taken as 168 kJ/kg.
And step two, selecting a proper group intelligent optimization algorithm according to the requirements of the optimization objective function and the configuration conditions of the computer. The optimization algorithm selected in the embodiment is a multi-target particle swarm optimization (MOPSO), the initial population size is set to be 50, and the maximum iteration number is set to be 200;
and step three, determining the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit according to the load requirement of the user side and the site condition. And then determining the upper limit and the lower limit of the optimized variable according to the latent heat storage capacity S. In this embodiment, the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit to be optimized at this time is determined to be 1200kJ according to the heat storage capacity of the three-sleeve phase-change heat storage heat exchange unit before optimization. According to the latent heat storage capacity, the upper limit and the lower limit of the optimization variable are determined to be r which is more than or equal to 0.0101≤0.023，0.045≤r2≤0.055，0.050≤r3≤0.065。
And step four, determining an optimized variable constraint condition meeting the actual requirement according to the requirement of the user load side. The constraint conditions determined by the embodiment are the length of the three-sleeve phase-change heat storage and exchange unit, L is less than 2.0m, and t is less than 7000s when the latent heat storage process is completed.
And step five, optimizing the objective function through the group intelligent optimization algorithm selected in the step two to obtain a Pareto optimal set.
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.
Claims (7)
1. An optimal design method of a three-sleeve phase-change heat storage heat exchange unit is characterized by comprising the following steps:
step one, determining an optimization variable and an optimization objective function;
the optimized variable is the radius r of the inner pipe, the sleeve and the outer pipe of the three-sleeve phase-change heat storage heat exchange unit1，r2，r3(ii) a The optimization objective function is: a heat exchange efficiency function, a time efficiency function and a quality function;
the heat exchange efficiency function is defined as follows:
s is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, Q is the heat (kJ) input by the heat exchange fluid, and W is the power consumption (kJ) of the water pump for overcoming the resistance loss of the three-sleeve phase-change heat storage and exchange unit;
the time efficiency function is defined as follows:
s is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, and t is the time for completing the latent heat storage process;
the quality function is:
wherein r is1，r2，r3The diameters (m) of the inner pipe, the sleeve and the outer pipe respectively, delta is the wall thickness (m), L is the length of the three-sleeve phase-change heat storage and exchange unit, and rhoMIs the density (kg/m) of the pipe3) S is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, and H is the phase-change latent heat (kJ/kg) of the phase-change material;
selecting a proper group intelligent optimization algorithm according to the requirements of an optimization objective function and computer configuration conditions;
determining the latent heat storage capacity S of the three-sleeve phase-change heat storage heat exchange unit according to the load requirement of the user side and the site condition; then determining the upper limit and the lower limit of an optimized variable according to the latent heat storage capacity S;
determining an optimized variable constraint condition meeting the actual requirement according to the requirement of the user load side;
the constraint may be: the length L of the three-sleeve phase-change heat storage and exchange unit, the time T for completing the latent heat storage process, the power consumption W of the water pump for overcoming the resistance loss of the phase-change heat exchange unit, and the temperature difference delta T between the inlet and the outlet of the heat exchange fluid flowing through the inner pipe and the outer pipe1,ΔT2；
And fifthly, optimizing an objective function through the selected group intelligent optimization algorithm to obtain the optimized variable Pareto optimal set.
2. The optimal design method according to claim 1, wherein the third step determines the upper and lower limits of the optimal variable according to the latent heat storage capacity S; the method comprises the following specific steps:
when S is less than or equal to 800kJ, r is more than or equal to 0.0081≤0.015，0.037≤r2≤0.045，0.044≤r3≤0.060；
When 800<When S is less than or equal to 1000kJ, r is more than or equal to 0.0081≤0.020，0.040≤r2≤0.050，0.048≤r3≤0.065；
When 1000<When S is less than or equal to 1500kJ, r is less than or equal to 0.0101≤0.023，0.045≤r2≤0.055，0.050≤r3≤0.065；
When 1500<When S is less than or equal to 2000kJ, r is more than or equal to 0.0121≤0.028，0.050≤r2≤0.065，0.055≤r3≤0.075。
3. The optimization design method according to claim 1, wherein in the second step, the group intelligence optimization algorithm is: a multi-target genetic algorithm NSGA-II, a multi-target particle swarm algorithm MOPSO, a multi-target artificial bee colony algorithm MOABC or a multi-target ant colony algorithm MOACA.
4. The optimal design method of claim 1, wherein the heat input by the Q heat exchange fluid of the heat exchange efficiency function is calculated by:
Q＝Q1+Q2＝cpt(ms1ΔT1+ms2ΔT2)
wherein, cpM is the specific heat capacity of the heat exchange fluids1,ms2Mass flow, Δ T, of the inner and outer tubes, respectively1,ΔT2The temperature difference of the heat exchange fluid flowing through the inlet and the outlet of the inner pipe and the outer pipe is respectively;
in the above technical solution, t is the time for completing the latent heat storage process, and the determining method is as follows:
wherein, lambda is the heat conductivity coefficient of the phase change material, w/(m.k), TinFor the inlet temperature, T, of the heat-exchange fluidpFor the phase change temperature of the phase change material, DEG C, hd is the thickness of the phase change material layer, and the value is the solution satisfying the following equation:
5. the optimal design method of claim 1, wherein the Δ T is1,ΔT2Calculated in the following manner, respectively:
ΔT1＝Tin-Tp-ΔTp1
wherein, Delta Tp1The temperature difference between the heat exchange fluid at the outlet of the inner tube of the three-sleeve phase-change heat storage and exchange unit and the phase-change material in the latent heat storage process is expressed as,
ΔT2＝Tin-Tp-ΔTp2
wherein, Delta Tp2The temperature difference between the heat exchange fluid at the outlet of the outer pipe of the three-sleeve phase-change heat storage and exchange unit and the phase-change material in the latent heat storage process is expressed as,
6. the optimal design method according to claim 1, wherein L is the tube length of the three-tube phase-change heat storage heat exchange unit and is expressed by
Wherein S is the latent heat storage capacity (kJ) of the three-sleeve phase-change heat storage and exchange unit, H is the phase-change latent heat (kJ/kg) of the phase-change material, and rhobIs a modified density (kg/m) of the phase change material taking into account natural convection3)，r1,r2The radius (m) of the inner pipe and the radius (m) of the sleeve of the three-sleeve phase-change heat storage heat exchange unit are respectively, and delta is the wall thickness (m).
7. The optimal design method according to claim 1, wherein the power consumption W of the water pump for overcoming the resistance loss of the three-sleeve phase-change heat storage heat exchange unit is calculated by the following method:
W＝W1+W2
W1＝πr1 2u1Δp1t
W2＝π(r3 2-r2 2)u2Δp2t
wherein u is1,u2The flow rates of the heat exchange fluid in the inner pipe and the outer pipe of the three-sleeve phase-change heat storage heat exchange unit are respectively, and delta p is the resistance loss of the heat exchange fluid flowing through the inner pipe and the outer pipe.
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