Central air-conditioning system adaptive to number of phase change balls and control method of central air-conditioning system

Abstract

The invention belongs to the technical field of central air conditioner virtual energy storage, and provides a central air conditioner system matched with the number of phase change balls and a control method thereof.The central air conditioner system comprises a central air conditioner group arranged in a building and an energy storage type fire water tank connected with the central air conditioner group; a plurality of phase change cold storage balls are arranged in the energy storage type fire water tank; the cold storage capacity of the fire-fighting water tank is determined according to the cold load requirement of a building, then the number of the phase change balls is selected by comprehensively considering the heat exchange performance and the economic performance of the water tank, and the contradictory problems that the cold storage requirement cannot be met due to the too small number of phase change materials and the cost is increased due to the too large number of phase change materials can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of central air-conditioning virtual energy storage, and in particular relates to a central air-conditioning system adapted to the number of phase change balls and a control method thereof. Background Art

[0002] Phase change materials change their state of matter and provide a large amount of latent heat without changing the temperature, so that the phase change process of phase change materials can store and release energy. Therefore, a phase change material-based energy storage device can be added to the central air-conditioning virtual energy storage system to store excess cold energy and use it during the peak period of the power grid, thereby extending the dispatchable time of the power grid.

[0003] At present, among the phase change materials used in the virtual energy storage system of central air-conditioning, only the layout of the phase change materials in the water tank is considered to achieve sufficient heat exchange and improve the utilization efficiency of cold energy; however, the number of phase change materials is set arbitrarily. When determining the number of phase change materials, the type of building is not considered, and the heat exchange performance and economic performance of the water tank are not considered. There are problems such as too little phase change material to meet the cold storage demand, and too much phase change material will lead to increased costs. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a central air-conditioning system and a control method thereof that are adapted to the number of phase change balls. The cold storage capacity of the fire water tank is determined according to the cold load demand of the building, and then the number of phase change balls is selected by comprehensively considering the heat exchange performance and economic performance of the water tank. This can solve the contradiction between the fact that too few phase change materials cannot meet the cold storage demand and that too many phase change materials will increase costs.

[0005] In order to achieve the above-mentioned purpose, in the first aspect, the present invention provides a central air conditioning system for adapting the number of phase change balls, which adopts the following technical solutions:

[0006] A central air-conditioning system adapted to the number of phase change balls, comprising a central air-conditioning group arranged in a building, and an energy storage type fire water tank connected to the central air-conditioning group;

[0007] A plurality of phase-change cold storage balls are arranged in the energy storage type fire water tank; wherein, the process of determining the number of phase-change cold storage balls in the energy storage type fire water tank is as follows: determining the cold storage capacity of the energy storage type fire water tank according to the ratio of the cold load demand to the heat exchange efficiency of the building; determining the number of phase change balls according to the equation relationship between the cold storage capacity and the number of phase change cold storage balls, the volume of a single phase change cold storage ball, the density of the phase change material and the product of the phase change latent heat of the phase change material, and the total construction cost of the energy storage type fire water tank, and the equation relationship between the number of phase change cold storage balls, the volume of a single phase change cold storage ball, the phase change latent heat of the phase change material and the unit price of the phase change material.

[0008] Furthermore, the energy storage type fire water tank includes a fire water tank body, and a flow equalizing plate and a phase change cold storage ball arranged in the fire water tank body.

[0009] Furthermore, a water inlet is provided at the geometric center of the top of the fire water tank body, and a water outlet is provided at the geometric center of the bottom; two flow equalizing plates are provided inside the fire water tank body, and multiple layers of phase change cold storage balls are alternately arranged between the flow equalizing plates.

[0010] Furthermore, the flow balancing plate is evenly distributed with flow balancing holes.

[0011] Furthermore, the phase change cold storage ball comprises a shell, and a phase change material arranged inside the shell; the phase change material includes but is not limited to Na 2 CrO 4 10H 2 O. KF·4H 2 O and C 16 H 34 .

[0012] Furthermore, the diameter of the phase change cold storage ball and the number of phase change balls are determined by the following calculation method:

[0013] E=Q PCM =n×V×ρ C16H34 ×[r+C P ×(T C16H34 -T st )]

[0014] Cost = n × V × ρ C16H34 ×P C16H34 +V 水 ×P 水

[0015] V 水 =n×d 3

[0016] Where E is the cold storage capacity of the energy storage fire water tank; Q PCM is the total cold storage capacity of the phase change cold storage ball; n is the number of phase change cold storage balls; V is the volume of a single phase change cold storage ball; ρ C16H34 is the density of the phase change material; r is the latent heat of phase change material; C P is the thermal conductivity of the phase change material; T C16H34 is the phase change temperature of the phase change material; T st is the initial temperature in the energy storage fire water tank; Cost is the total cost of the energy storage fire water tank; P C16H34 is the unit price of phase change material; P 水 is the cost of the fire water tank; V 水is the volume of the fire water tank; d is the diameter of the phase change cold storage ball.

[0017] Furthermore, the central air-conditioning group and the energy storage fire water tank are connected to a controller, and the controller is used to adjust the refrigerant water flow rate through an adaptive controller during the peak period of urban electricity consumption to control the room temperature within a preset range.

[0018] Furthermore, during peak hours, based on the heat exchange relationship between the temperature change in the room and the refrigerant water flowing through the room, the first-order transfer function of the process of adjusting the room temperature by the speed of the fire pump is derived as follows:

[0019]

[0020] Among them, T r is the room temperature; T out is the temperature outside the room; R is the equivalent thermal resistance; C is the heat capacity of the gas in the room; Q is the heat exchange amount of the refrigerant water; N is the speed of the fire pump; ρ and c p are the density and specific heat of fire water respectively; ΔT is the temperature difference between the inlet and outlet of the fire water tank; V c The displacement of the fire pump.

[0021] Furthermore, the correction factor is introduced to obtain the first-order transfer function G(z) expressed as:

[0022]

[0023] Where u(z) and y(z) are the input and output; a and b are the coefficients of the transfer function to be determined; a 1 and b 1 is the correction factor; the performance index of real-time correction is:

[0024]

[0025] in, is the parameter matrix to be estimated; λ is the genetic factor, 0≤λ≤1; y(k) is the system output; is the system input.

[0026] In order to achieve the above-mentioned purpose, in a second aspect, the present invention also provides a central air conditioning system control method for adapting the number of phase change balls, which adopts the following technical solution:

[0027] A central air-conditioning system adapted to the number of phase change balls uses the central air-conditioning system adapted to the number of phase change balls as described in the first aspect, comprising: the energy storage type fire water tank obtains cold energy from the central air-conditioning group, and the phase change material inside the energy storage type fire water tank solidifies and stores cold energy; during the peak period of urban electricity consumption, the phase change material inside the energy storage type fire water tank melts and releases cold energy, and provides the cold energy to the user side.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention determines the cold storage capacity of the fire water tank according to the cold load demand of the building, and then selects the number of phase change balls by comprehensively considering the heat exchange performance and economic performance of the water tank, thereby solving the contradiction between too little phase change material failing to meet the cold storage demand and too much phase change material resulting in increased costs.

[0030] In the present invention, a flow equalizing plate is provided inside the energy storage type fire water tank, so that the refrigerant water and the phase change cold storage ball can fully exchange heat. The outside is arranged with a thermal insulation material with good performance to reduce the heat exchange between the energy storage type fire water tank and the outside world and improve the energy utilization efficiency.

[0031] The dynamic changes in the external environment have brought a series of problems to the refrigerant water flow regulation of the energy storage fire water tank during the peak period of urban electricity consumption, including system nonlinearity and unpredictable disturbances. Based on this, the present invention introduces an adaptive temperature control method, which can ensure high-precision room temperature control during the peak period of urban electricity consumption, enable the system to show better stability, and improve its adaptability under changes in the external dynamic environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification that constitute a part of this embodiment are used to provide a further understanding of this embodiment. The schematic embodiments of this embodiment and their descriptions are used to explain this embodiment and do not constitute improper limitations on this embodiment.

[0033] Figure 1 This is a system schematic diagram of Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the system operation of Embodiment 1 of the present invention;

[0035] Figure 3 This is a schematic diagram of the configuration of a central air conditioning unit according to Embodiment 1 of the present invention;

[0036] Figure 4 This is a schematic diagram of an energy storage fire water tank according to Embodiment 1 of the present invention;

[0037] Figure 5 Schematic diagram of the phase change ball of Example 1 of the present invention;

[0038] Among them, 1. Central air-conditioning group; 11. Evaporator; 12. Throttle valve; 13. Condenser; 14. Compressor; 15. Separator; 2. User side; 3. Energy storage fire water tank; 31. Fire water tank body; 32. Flow equalizing plate; 33. Phase change cold storage ball; 331. Phase change material; 332. Shell. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0041] Embodiment 1:

[0042] As the load of urban power grids during peak periods continues to rise, the peak load regulation demand of power grids is increasing. Among them, the power consumption of central air-conditioning systems accounts for 40%-60% of the total power demand of buildings, and has the characteristics of concentrated use time. The central air-conditioning load has become the main component of the peak load. Therefore, using central air-conditioning to alleviate the peak load of the power grid is of great significance to alleviate the peak-to-valley difference of the power grid and the pressure of power grid operation.

[0043] Central air conditioners consume electricity from the power grid to generate cold air and store it in the room. The amount of cold air stored in the room is adjusted by adjusting the cooling temperature of the air conditioner, which makes the central air conditioner have certain energy storage characteristics. Without affecting the comfort level in the room, the excess cold air is stored in the room during low power consumption and released during peak power consumption. The load on the power grid is reduced by reducing the energy consumption of the central air conditioner during peak power consumption. However, the storage capacity of the central air conditioner virtual energy storage is affected by many factors such as the size of the room and the heat exchange effect between the room and the surrounding structure, resulting in a short dispatchable time of the power grid.

[0044] Phase change materials change the state of matter and provide a large amount of latent heat when the temperature remains unchanged, so that the phase change process of phase change materials can realize energy storage and release. Therefore, an energy storage device based on phase change materials can be added to the central air-conditioning virtual energy storage system, and the excess cold can be stored through the energy storage device and used during the peak period of the power grid, thereby extending the dispatchable time of the power grid. However, as recorded in the background technology, at present, among the phase change materials used in the central air-conditioning virtual energy storage system, only the layout form of the phase change material in the water tank is considered to achieve sufficient heat exchange and improve the utilization efficiency of cold energy; however, the number of phase change materials is set arbitrarily, and when determining the number of phase change materials, the type of building is not considered, nor is the heat exchange performance and economic performance of the water tank considered, resulting in the inability to solve the contradiction between the small number of phase change materials that cannot meet the cold storage demand and the excessive number of phase change materials that will increase costs.

[0045] In order to solve at least one of the above problems, Figure 1 As shown, this embodiment provides a central air-conditioning system that adapts to the number of phase change balls, including a central air-conditioning group 1 and an energy storage type fire water tank 3. Figure 2As shown, during the period of low electricity consumption in the city, the central air-conditioning group 1 operates at an overclocked frequency and provides cooling energy to the user side 2 and the energy storage type fire water tank 3 at the same time; during the period of peak electricity consumption in the city, the central air-conditioning group 1 operates at a low frequency or is shut down, and the energy storage type fire water tank 3 provides cooling energy to the user side 2, thereby increasing the virtual energy storage density of the central air-conditioning.

[0046] like Figure 3 As shown, the central air-conditioning group 1 includes a series of air-conditioning units, which adopt a steam compression refrigeration cycle, mainly including an evaporator 11, a throttle valve 12, a condenser 13, a compressor 14 and a separator 15; low-pressure refrigerant vapor is compressed by the compressor 14 to become high-temperature and high-pressure refrigerant vapor, and the high-temperature and high-pressure refrigerant vapor is cooled in the condenser 13 to become a high-pressure liquid, and then flows through the throttle valve 12 to throttle and reduce the pressure to become a low-temperature and low-pressure refrigerant liquid, and the low-pressure refrigerant liquid enters the evaporator 11, absorbs the heat of the room-temperature refrigerant water, evaporates into low-pressure steam and flows into the compressor 14 to complete the cycle.

[0047] When electricity consumption is low, the separator 15 divides the refrigerant water flowing out of the central air-conditioning group 1 into two parts, which respectively provide cooling capacity for the energy storage type fire water tank 3 and the user side 2; the refrigerants used in the central air-conditioning group 1 include but are not limited to R410a and R134a.

[0048] like Figure 4 As shown, the energy storage type fire water tank 3 comprises a fire water tank body 31, a flow equalizing plate 32 and a phase change cold storage ball 33. A water inlet is provided at the geometric center of the top of the fire water tank body 31, and a water outlet is provided at the geometric center of the bottom; two flow equalizing plates 32 are provided inside the fire water tank body 31, and multiple layers of phase change cold storage balls 33 are arranged alternately between the flow equalizing plates 32, so that the refrigerant water entering the fire water tank body 31 can fully exchange heat with the phase change cold storage balls 33, thereby improving the utilization efficiency of cold energy.

[0049] like Figure 5 As shown, the phase change cold storage ball 33 includes a shell 332 and an internal phase change material 331. The molten phase change material 331 is injected into the shell 332 by vacuum injection. The temperature range of the phase change material 331 can be 16-19°C, including but not limited to Na 2 CrO 4 10H 2 O. KF·4H 2 O and C 16 H 34 etc.; the shell 332 is required to have a higher heat transfer coefficient, good stability and good strength, and the materials that can be used include but are not limited to stainless steel, aluminum alloy and copper materials.

[0050] Optionally, the outside of the energy storage type fire water tank 3 is wrapped with thermal insulation material, and thermal insulation materials with a thermal conductivity of 0.02-0.03W / (m·℃) can be selected, including but not limited to polyurethane thermal insulation materials, aerogel thermal insulation materials or extruded polystyrene boards and other materials. The use of materials with lower thermal conductivity can minimize the heat dissipation of the energy storage type fire water tank 3 to the external environment, thereby improving the utilization efficiency of cold energy.

[0051] This embodiment also provides a method for determining the design parameters of a phase-change cold storage ball in an energy storage type fire water tank, comprising the following steps:

[0052] S1. Determine the type of building. The differences in the functions of different buildings will lead to differences in the operating time of the air-conditioning system, the density of people, electricity consumption, etc. Common public buildings are mainly divided into two categories: office and commercial buildings.

[0053] S2. Calculate the cooling load of the building, the cooling load of the building Q x The demand is the sum of the cooling loads of each room in the building. Usually, the heat transfer of the enclosure structure, the heat gain from solar radiation, the heat dissipation of the human body, the heat dissipation of lighting devices and the heat dissipation of other equipment are taken into consideration. The cooling capacity E of the energy storage fire water tank is defined as follows:

[0054]

[0055] Where E is the cold storage capacity of the energy storage fire water tank; Q x is the cooling load demand of the building; η is the heat exchange efficiency, η=0.9.

[0056] S3. Select phase change materials. The selection and performance of phase change materials are important prerequisites for phase change heat storage systems. Good phase change materials should have appropriate phase change temperature (16-19°C), large phase change latent heat, appropriate thermal conductivity, stable thermal properties, and good economic performance. After selecting the phase change material, it is necessary to query its important thermal properties such as phase change latent heat, phase change temperature, and specific heat capacity for further calculation;

[0057] S4. Calculate the number of cold storage balls corresponding to different phase change cold storage ball diameters d according to the heat exchange relationship:

[0058] E=Q PCM =n×V×ρ C16H34 ×[r+C P ×(T C16H34 -T st )]

[0059] Among them, Q PCM is the total cold storage capacity of the phase change cold storage ball; n is the number of phase change cold storage balls; V is the volume of a single phase change cold storage ball; ρ C16H34is the density of the phase change material; r is the latent heat of phase change material; C P is the thermal conductivity of the phase change material; T C16H34 is the phase change temperature of the phase change material; T st It is the initial temperature inside the energy storage type fire water tank.

[0060] S5. Estimate the volume of the water tank and calculate the cost of the energy storage fire water tank:

[0061] Cost = n × V × ρ C16H34 ×P C16H34 +V 水 ×P 水

[0062] V 水 =n×d 3

[0063] Among them, Cost is the total cost of the energy storage fire water tank; P C16H34 is the unit price of phase change material, which is 75 yuan / kg; 水 The cost of the fire water tank is 600 yuan / m 3 ; V 水 is the volume of the fire water tank, which is roughly estimated to be the volume of the space occupied by the phase change cold storage ball.

[0064] S6. Select the number of phase change balls by comprehensively considering the heat transfer performance and economic performance of the water tank.

[0065] The working process or control method of this embodiment is:

[0066] One hour before the peak of urban electricity consumption, the cooling temperature of the central air-conditioning group 1 is lowered, and the central air-conditioning group 1 runs in overclocking. A part of the refrigerant water provides cooling for the user side 2, reducing the temperature in the room of the user side 2 to about 22°C and storing the excess cold energy in the room. At the same time, another part of the refrigerant water cools the phase change material 331 in the energy storage type fire water tank 3 and stores cold energy through the solidification process of the phase change material 331, which serves as a backup cold source for the user side 2 during the peak electricity consumption period.

[0067] When the peak of urban electricity consumption comes, the central air-conditioning group 1 is shut down for low-frequency operation or shut down, and the power grid load is reduced and the purpose of peak shaving is achieved by reducing the energy consumption of high-power equipment air conditioners. At this time, the room on the user side 2 exchanges heat with the enclosure structure, so that the temperature in the room rises to the set temperature of 24°C, and at the same time releases the cold energy stored in the room to maintain the temperature in the room stable at the preset temperature. Since the cold energy storage in the room is limited, the refrigerant water obtains cold energy from the melting process of the phase change material in the energy storage fire water tank and provides cold energy to the user side 2. The refrigerant water releases the cold energy to the room, maintaining the temperature in the room at around 24°C to ensure human comfort, increasing the virtual energy storage density of the central air-conditioning and extending the dispatchable time of the power grid.

[0068] Optionally, during the peak period of urban electricity consumption, the refrigerant water flow rate is adjusted by an adaptive controller to control the room temperature within the human comfort range. The control variable of the adaptive controller is the speed of the fire pump, the controlled variable is the room temperature, and the controller type is a PI controller, and its expression is as follows:

[0069]

[0070] Among them, r(t) is the set value; e(t) is the error after subtracting the set value from the feedback value; u(t) is the input variable; τ I is the integration time; K p , K I are the proportional and integral coefficients respectively.

[0071] During peak hours, based on the heat exchange relationship between the temperature change in the room and the refrigerant water flowing through the room, the first-order transfer function of the process of adjusting the room temperature by the speed of the fire pump is derived as follows:

[0072]

[0073] Among them, T r is the room temperature; T out is the temperature outside the room; R is the equivalent thermal resistance; C is the heat capacity of the gas in the room; Q is the heat exchange amount of the refrigerant water; N is the speed of the fire pump; ρ and c p are the density and specific heat of fire water respectively; ΔT is the temperature difference between the inlet and outlet of the fire water tank; V c The displacement of the fire pump;

[0074] Introducing correction factor a 1 and b 1 The first-order transfer function G(z) can be expressed as:

[0075]

[0076] Where u(z) and y(z) are the input and output, and a and b are the coefficients of the transfer function to be determined, which are expressed as follows:

[0077]

[0078] Affected by the external environment, the transfer function in the first-order transfer function G(z) is non-steady. Therefore, the recursive least squares algorithm with genetic factors is used to modify the transfer function model in the first-order transfer function G(z) in real time, and the control parameters are adjusted according to the real-time modified transfer function model, so as to achieve the purpose of adaptively adjusting the room temperature during the peak period of urban electricity consumption. Among them, the performance indicators of real-time correction are:

[0079]

[0080] in, is the parameter matrix to be estimated; λ is the genetic factor, 0≤λ≤1; y(k) is the system output; is the system input; the parameter estimation formula is:

[0081]

[0082] Among them, K(k) is the gain coefficient; P(k) is the error covariance matrix.

[0083] By introducing active control methods, the speed of the fire pump is adjusted to effectively cope with the fluctuation of the ambient temperature in the room, so that the ambient temperature is stabilized at a comfortable temperature for the human body, and the control accuracy and stability of the system are improved.

[0084] This embodiment aims to solve the problem of large power load during peak hours of urban electricity consumption and huge energy consumption of central air conditioners. During the period of low electricity consumption in the city, the central air conditioner group operates at an overclocked frequency, and at the same time provides cold energy to the user side and the energy storage type fire water tank, and stores excess cold energy in the room on the user side and in the phase change material of the energy storage type fire water tank in advance; during the period of peak electricity consumption in the city, the central air conditioner group operates at a low frequency or is shut down, and the energy storage type fire water tank provides cold energy to the user side, and realizes virtual storage and utilization of electric energy through the storage and release of cold energy, effectively realizing the peak shaving strategy and saving electricity consumption during peak hours.

[0085] In order to solve the problem that virtual energy storage is limited by the size of the room, this embodiment relies on the fire water tank equipped by the building group itself as a basis, and adds a phase change cold storage ball inside the fire water tank. During the low period of urban electricity consumption, the energy storage fire water tank obtains cold energy from the central air conditioning group, and the phase change material inside the energy storage fire water tank solidifies and stores cold energy; during the peak period of urban electricity consumption, the phase change material inside the energy storage fire water tank melts and releases cold energy to provide cooling for the user side, so that the temperature in the room on the user side can be stabilized at the set temperature even when the central air conditioning group is running at a low frequency or turned off, ensuring the comfort in the room. The setting of the energy storage fire water tank effectively increases the virtual energy storage density of the central air conditioning and extends the dispatchable time of the power grid.

[0086] Embodiment 2:

[0087] This embodiment uses specific examples to illustrate and supplement the system and method in Embodiment 1. Optionally, consider a 15-story building with a building area of ​​about 20,000 square meters. The summer cooling load is 600kW. Consider that the energy storage fire water tank 3 provides a cooling load for the building for 1 hour during peak hours. Assume that the initial temperature T st The temperature is 15° C., and the phase change cold storage ball 33 inside the energy storage type fire water tank 3 of this embodiment is analyzed.

[0088]

[0089] Phase change material uses C 16 H 34 The parameters of phase change cold storage ball are listed in Table 1.

[0090] Table 1 Phase change cold storage ball parameters

[0091]

[0092]

[0093]

[0094] According to the cooling demand of the building, the number of phase change cold storage balls under different phase change cold storage ball diameters and the cost of the energy storage type fire water tank can be calculated as shown in Table 2.

[0095] Table 2 Energy storage fire water tank

[0096]

[0097] The larger the diameter of the phase change cold storage ball, the worse the heat transfer performance will be. Considering the construction cost and heat exchange performance of the energy storage fire water tank, a phase change ball with a diameter of 0.2m should be selected.

[0098] Embodiment 3:

[0099] The present embodiment provides a central air-conditioning system that adapts the number of phase change balls, using the central air-conditioning system that adapts the number of phase change balls as described in Embodiment 1, including: the energy storage type fire water tank obtains cold energy from the central air-conditioning group, and the phase change material inside the energy storage type fire water tank solidifies and stores cold energy; during the peak period of urban electricity consumption, the phase change material inside the energy storage type fire water tank melts and releases cold energy, and provides the cold energy to the user side.

[0100] The above description is only a preferred embodiment of the present embodiment and is not intended to limit the present embodiment. For those skilled in the art, the present embodiment may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present embodiment shall be included in the protection scope of the present embodiment.

Claims

1. A central air conditioning system adapted to the number of phase change balls, characterized in that: It includes a central air-conditioning group arranged in a building, and an energy storage type fire water tank connected to the central air-conditioning group; A plurality of phase-change cold storage balls are arranged in the energy storage type fire water tank; wherein, the process of determining the number of phase-change cold storage balls in the energy storage type fire water tank is as follows: determining the cold storage capacity of the energy storage type fire water tank according to the ratio of the cold load demand to the heat exchange efficiency of the building; determining the number of phase change balls according to the equation relationship between the cold storage capacity and the number of phase change cold storage balls, the volume of a single phase change cold storage ball, the density of the phase change material and the product of the phase change latent heat of the phase change material, and the total construction cost of the energy storage type fire water tank, and the equation relationship between the number of phase change cold storage balls, the volume of a single phase change cold storage ball, the phase change latent heat of the phase change material and the unit price of the phase change material.

2. A central air conditioning system for adapting the number of phase change balls as claimed in claim 1, characterized in that: The energy storage type fire water tank comprises a fire water tank body, and a flow equalizing plate and a phase change cold storage ball arranged in the fire water tank body.

3. A central air conditioning system for adapting the number of phase change balls as claimed in claim 2, characterized in that: A water inlet is arranged at the geometric center of the top of the fire water tank body, and a water outlet is arranged at the geometric center of the bottom; two flow equalizing plates are arranged inside the fire water tank body, and multiple layers of phase change cold storage balls are arranged alternately between the flow equalizing plates.

4. A central air conditioning system for adapting the number of phase change balls as claimed in claim 2, characterized in that: The flow balancing plate is provided with flow balancing holes evenly distributed thereon.

5. A central air conditioning system for adapting the number of phase change balls as claimed in claim 1, characterized in that: The phase-change cold storage ball comprises a shell and a phase-change material arranged inside the shell; the phase-change material includes but is not limited to Na2CrO4·10H2O, KF·4H2O and C 16 H 34 .

6. A central air conditioning system for adapting the number of phase change balls as claimed in claim 1, characterized in that: The diameter of the phase change cold storage ball and the number of phase change balls are determined by calculation as follows: E=Q PCM =n×V×ρ C16H34 ×[r+C P ×(T C16H34 -T st )] Cost=n×V×ρ C16H34 ×P C16H34 +V 水 ×P 水 In 水 =n×d 3 Where E is the cold storage capacity of the energy storage fire water tank; Q PCM is the total cold storage capacity of the phase change cold storage ball; n is the number of phase change cold storage balls; V is the volume of a single phase change cold storage ball; ρ C16H34 is the density of the phase change material; r is the latent heat of phase change material; C P is the thermal conductivity of the phase change material; T C16H34 is the phase change temperature of the phase change material; T st is the initial temperature in the energy storage fire water tank; Cost is the total cost of the energy storage fire water tank; P C16H34 is the unit price of phase change material; P 水 is the cost of the fire water tank; V 水 is the volume of the fire water tank; d is the diameter of the phase change cold storage ball.

7. A central air conditioning system for adapting the number of phase change balls as claimed in claim 1, characterized in that: The central air conditioning group and the energy storage fire water tank are connected to a controller, and the controller is used to adjust the refrigerant water flow rate through an adaptive controller during the peak period of urban electricity consumption to control the room temperature within a preset range.

8. A central air conditioning system for adapting the number of phase change balls as claimed in claim 7, characterized in that: During peak hours, based on the heat exchange relationship between the temperature change in the room and the refrigerant water flowing through the room, the first-order transfer function of the process of adjusting the room temperature by the speed of the fire pump is derived as follows: Among them, T r is the room temperature; T out is the temperature outside the room; R is the equivalent thermal resistance; C is the heat capacity of the gas in the room; Q is the heat exchange amount of the refrigerant water; N is the speed of the fire pump; ρ and c p are the density and specific heat of fire water respectively; ΔT is the temperature difference between the inlet and outlet of the fire water tank; V c The displacement of the fire pump.

9. A central air conditioning system for adapting the number of phase change balls as claimed in claim 8, characterized in that: Introducing the correction factor, the first-order transfer function G(z) is expressed as: Among them, u(z) and y(z) are input and output; a and b are the coefficients of the transfer function to be determined; a1 and b1 are correction factors; the performance index of real-time correction is: in, is the parameter matrix to be estimated; λ is the genetic factor, 0≤λ≤1; y(k) is the system output; is the system input.

10. A central air conditioning system adapted to the number of phase change balls, characterized in that: A central air-conditioning system using an adaptive number of phase change balls as described in any one of claims 1 to 9 comprises: the energy storage type fire water tank obtains cold energy from the central air-conditioning group, and the phase change material inside the energy storage type fire water tank solidifies and stores cold energy; during the peak period of urban electricity consumption, the phase change material inside the energy storage type fire water tank melts and releases cold energy, and provides the cold energy to the user side.

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