Central air conditioning system adapting number of phase change balls and control method thereof

Abstract

The application belongs to the technical field of central air conditioning virtual energy storage, and proposes a central air conditioning system and a control method thereof which are 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 with the central air conditioning group; a plurality of phase change cold storage balls are arranged in the energy storage type fire water tank; according to the cooling load demand of the building, the cold storage capacity of the fire water tank is determined, and then the number of phase change balls is selected by comprehensively considering the heat exchange performance and economic performance of the water tank, so that the contradictory problem between the fact that too few phase change materials cannot meet the cold storage demand and the fact that too many phase change materials will increase the cost can be solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of central air conditioning virtual energy storage, and particularly relates to a central air conditioning system with adaptive phase change ball quantity and a control method thereof. BACKGROUND

[0002] The phase change material changes the state of matter and provides a large amount of latent heat under constant temperature, so that the phase change process of the phase change material can realize energy storage and release. Therefore, an energy storage device based on the phase change material can be added in the central air conditioning virtual energy storage system to store excess cold and be used in the peak period of the power grid, thereby prolonging the dispatchable time of the power grid.

[0003] At present, only the layout form of the phase change material in the water tank is considered in the phase change material used in the central air conditioning virtual energy storage system to achieve sufficient heat exchange and improve the utilization efficiency of cold energy. However, the quantity of the phase change material is set at will, and when the quantity of the phase change material is determined, the building type is not considered, and the heat exchange performance and economic performance of the water tank are not considered. There are problems such as that the too small quantity of the phase change material cannot meet the cold storage demand, and that the too large quantity of the phase change material will increase the cost. SUMMARY

[0004] To solve the above problems, the application provides a central air conditioning system with adaptive phase change ball quantity and a control method thereof. According to the cold load demand of the building, the cold storage capacity of the fire water tank is determined, and then the quantity of the phase change ball is selected by comprehensively considering the heat exchange performance and economic performance of the water tank, so that the contradiction between the too small quantity of the phase change material and the too large quantity of the phase change material can be solved.

[0005] To achieve the above purpose, in a first aspect, the application provides a central air conditioning system with adaptive phase change ball quantity, which adopts the following technical scheme:

[0006] The central air conditioning system with adaptive phase change ball quantity comprises a central air conditioning group arranged in a building and an energy storage type fire water tank connected with the central air conditioning group.

[0007] The energy storage type fire water tank is provided with a plurality of phase change cold storage balls. The determination process of the quantity of the phase change cold storage balls in the energy storage type fire water tank is as follows: according to the ratio of the cold load demand of the building to the heat exchange efficiency, the cold storage capacity of the energy storage type fire water tank is determined; according to the equal equation relationship between the cold storage capacity, the quantity of the phase change cold storage balls, the volume of a single phase change cold storage ball, the density of the phase change material and the phase change latent heat of the phase change material, and the equal equation relationship between the total cost of the energy storage type fire water tank, the quantity of the 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, the quantity of the phase change balls is determined.

[0008] Further, the energy storage type fire-fighting water tank comprises a fire-fighting water tank body, and a flow equalizing plate and phase change cold storage balls arranged in the fire-fighting water tank body.

[0009] Further, the geometric center of the top of the fire-fighting water tank body is provided with a water inlet, and the geometric center of the bottom is provided with a water outlet; the inside of the fire-fighting water tank body is provided with two flow equalizing plates, and a plurality of layers of phase change cold storage balls are arranged staggeredly between the flow equalizing plates.

[0010] Further, the flow equalizing plate is uniformly provided with flow equalizing holes.

[0011] Further, the phase change cold storage ball comprises an outer shell and a phase change material arranged in the outer shell; the phase change material comprises but is not limited to Na2CrO4·10H2O, KF·4H2O and C 16 H 34 .

[0012] Further, the diameter of the phase change cold storage ball and the number of phase change balls are determined according to 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] Wherein, E is the cold storage capacity of the energy storage type fire-fighting 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 of the 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 type fire-fighting water tank; Cost is the total cost of the energy storage type fire-fighting water tank; P C16H34 is the unit price of the phase change material; P 水 is the cost of the fire-fighting water tank body; V 水 is the volume of the fire-fighting water tank body; and d is the diameter of the phase change cold storage ball.

[0017] Further, the central air conditioning group and the energy storage type fire water tank are connected with a controller, and the controller is used for adjusting the refrigerant water flow through the self-adaptive controller to control the room temperature in the preset interval during the urban power peak period.

[0018] Further, during the peak period, the first-order transfer function of the process of adjusting the room temperature by the fire water pump speed is deduced according to the heat exchange relationship between the room temperature change and the refrigerant water flowing through the room as follows:

[0019]

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

[0021] Further, the first-order transfer function G(z) is obtained by introducing a correction factor and is expressed as:

[0022]

[0023] Wherein, u(z) and y(z) are input and output; a and b are transfer function coefficients to be solved; a1 and b1 are correction factors; the real-time corrected performance index is:

[0024]

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

[0026] In order to achieve the above purpose, in the second aspect, the application further provides a central air conditioning system control method for adapting the number of phase change balls, which adopts the following technical scheme:

[0027] A central air conditioning system for adapting the number of phase change balls uses the central air conditioning system for adapting 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 urban power peak period, 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 application has the following beneficial effects:

[0029] The application determines the cold storage capacity of the fire-fighting 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, so as to solve the contradiction between the fact that too little phase change material cannot meet the cold storage demand and the fact that too much phase change material will increase the cost.

[0030] The energy storage type fire-fighting water tank in the application is internally provided with a flow equalizing plate, so that the refrigerant water and the phase change cold storage balls can be fully heat exchanged, and the energy storage type fire-fighting water tank is externally provided with a good thermal insulation material, so as to reduce the heat exchange between the energy storage type fire-fighting water tank and the outside environment and improve the energy utilization efficiency.

[0031] The dynamic change of the external environment brings a series of problems to the refrigerant water flow regulation of the energy storage fire-fighting water tank during the city power peak period, including system nonlinearity, unmeasurable disturbance, etc.; based on this, the application introduces an adaptive temperature control method, which can ensure the high precision of room temperature control during the city power peak period, make the system show better stability, and improve the adaptability under the dynamic change of the external environment. BRIEF DESCRIPTION OF DRAWINGS

[0032] The drawings accompanying this specification form a part of this specification, and serve to further understand the embodiments of the present application. The schematic embodiments of the present application and the explanations thereof are used to explain the present application, and do not constitute an improper limitation on the present application.

[0033] Figure 1 It is a system schematic diagram of the embodiment 1 of the present application;

[0034] Figure 2 It is a system working schematic diagram of the embodiment 1 of the present application;

[0035] Figure 3 It is a central air conditioning unit configuration schematic diagram of the embodiment 1 of the present application;

[0036] Figure 4 It is a schematic diagram of the energy storage type fire-fighting water tank of the embodiment 1 of the present application;

[0037] Figure 5 It is a schematic diagram of the phase change ball of the embodiment 1 of the present application;

[0038] 1, central air conditioning group; 11, evaporator; 12, throttle valve; 13, condenser; 14, compressor; 15, separator; 2, user side; 3, energy storage type fire-fighting water tank; 31, fire-fighting water tank body; 32, flow equalizing plate; 33, phase change cold storage ball; 331, phase change material; 332, shell. DETAILED DESCRIPTION

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

[0040] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0041] Embodiment 1

[0042] With the continuous rise of urban power grid peak period load, the demand for power grid peak shaving is increasing. Among them, the use of electric energy of central air conditioning system accounts for 40%-60% of the total electric energy demand of the building, and has the characteristics of concentrated use of time. The central air conditioning load has become the main component of the peak load. Therefore, using central air conditioning to relieve the peak load of the power grid has important significance for relieving the peak-valley difference of the power grid and the operating pressure of the power grid.

[0043] The central air conditioning consumes the electric energy of the power grid to generate cold and store it in the room. By adjusting the cooling temperature of the air conditioner, the amount of cold stored in the room is adjusted, so that the central air conditioning has certain energy storage characteristics. On the premise of not affecting the comfort of the room, store excess cold in the room during the low electricity consumption period, and release it during the peak electricity consumption period. By reducing the energy consumption of central air conditioning during the peak electricity consumption period, the load of the power grid is reduced. However, the storage capacity of the virtual energy storage of the central air conditioning is affected by many factors such as the size of the room, the heat exchange effect between the room and the envelope, etc., resulting in a short power grid dispatchable time.

[0044] The phase change material changes the state of matter and provides a large amount of latent heat under constant temperature, so that the phase change process of the phase change material can realize the storage and release of energy. Therefore, an energy storage device based on phase change material can be added to the central air conditioning virtual energy storage system to store excess cold and be used during the peak period of the power grid, thereby extending the dispatchable time of the power grid. However, as described in the background art, at present, the phase change material used in the central air conditioning virtual energy storage system only considers the layout form of the phase change material in the water tank to achieve sufficient heat exchange and improve the utilization efficiency of cold energy. However, the amount of phase change material is randomly set. When determining the amount of phase change material, 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 contradictory problem between the insufficient amount of phase change material that cannot meet the cold storage demand and the excessive amount of phase change material that will increase the cost.

[0045] To solve at least one of the above problems, as shown in Figure 1 The embodiment provides a central air conditioning system adapted to the number of phase change balls, which comprises a central air conditioning group 1 and an energy storage type fire-fighting water tank 3. Figure 2As shown, during the city electricity low period, the central air conditioning group 1 over frequency operation, at the same time for user side 2 and energy storage type fire water tank 3 provide cold energy; during the city electricity peak period, the central air conditioning group 1 low frequency operation or shutdown, energy storage type fire water tank 3 for user side 2 provide cold energy, increase the virtual energy storage density of central air conditioning.

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

[0047] During the electricity low period, the separator 15 divides the refrigerant water flowing out of the central air conditioning group 1 into two parts, which provides cold energy for the energy storage type fire water tank 3 and the user side 2 respectively; the refrigerant used in the central air conditioning group 1 includes but is not limited to R410a and R134a.

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

[0049] As shown in the figure, Figure 5 The phase change cold storage ball 33 includes shell 332 and internal phase change material 331, and the molten phase change material 331 is injected into the inside of the shell 332 by vacuum injection method; the temperature range of the phase change material 331 can be 16-19℃, including but not limited to Na2CrO4·10H2O, KF·4H2O and C 16 H 34 Etc.; the shell 332 requires high 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, etc.

[0050] Optionally, the energy storage type fire water tank 3 is wrapped with thermal insulation material, and the thermal conductivity coefficient of the thermal insulation material can be 0.02-0.03 W / (m·℃), including but not limited to polyurethane thermal insulation material, aerogel thermal insulation material or extruded polystyrene board and the like. Using a material with a lower thermal conductivity coefficient 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] The embodiment also provides a method for determining the design parameters of the phase change cold storage ball in the energy storage type fire water tank, comprising the following steps:

[0052] S1, determining the type of the building. The difference in use function of different buildings will cause differences in the running time of the air conditioning system, the density of personnel, the power consumption and the like. Common public buildings are mainly divided into two categories of office type and commercial type buildings.

[0053] S2, calculating the cooling load of the building. The cooling load Q of the building is calculated according to the following formula: x The demand is the sum of the cooling loads of all rooms in the building. Generally, the heat transfer of the envelope structure, the solar radiation heat, the human body heat, the lighting device heat and the heat of other equipment are considered. The cold storage capacity E of the energy storage type fire water tank is defined as follows:

[0054]

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

[0056] S3, selecting the phase change material. The selection and performance of the phase change material are important prerequisites for the phase change heat storage system. A good phase change material should have a suitable phase change temperature (16-19℃), a large phase change latent heat, a suitable thermal conductivity, a stable thermal property and a good economic performance. After selecting the phase change material, the important thermal property parameters such as the phase change latent heat, the phase change temperature and the specific heat capacity need to be queried for further calculation;

[0057] S4, calculating the number of the cold storage balls with 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] Wherein, Q PCM is the total cold storage capacity of the phase change cold storage ball; n is the number of the phase change cold storage ball; V is the volume of a single phase change cold storage ball; ρ C16H34ρ is the density of the phase change material; r is the latent heat of the phase change material; C P k is the thermal conductivity of the phase change material; T C16H34 T is the phase change temperature of the phase change material; T st T is the initial temperature in the energy storage type fire-fighting water tank.

[0060] S5, estimate the volume of the water tank and calculate the cost of the energy storage type fire-fighting water tank:

[0061] Cost = n x V x p C16H34 x P C16H34 + V 水 x P 水

[0062] V 水 = n x d 3

[0063] wherein Cost is the total cost of the energy storage type fire-fighting water tank; P C16H34 is the unit price of the phase change material, taken as 75 yuan / kg; P 水 is the cost of the fire-fighting water tank body, taken as 600 yuan / m 3 ; V 水 is the volume of the fire-fighting water tank body, which is roughly estimated as the volume of the space occupied by the phase change cold storage balls.

[0064] S6, the number of phase change balls is selected by comprehensively considering the heat exchange performance and economic performance of the water tank.

[0065] The working process or control method of the embodiment is as follows:

[0066] An hour before the city's power peak, the cooling temperature of the central air conditioning group 1 is lowered, the central air conditioning group 1 is operated at a high frequency, a part of the refrigerant water is used to cool the user side 2, the room temperature of the user side 2 is reduced to about 22℃, and the excess cold energy is stored in the room, while another part of the refrigerant water cools the phase change material 331 in the energy storage type fire-fighting water tank 3 and stores cold energy through the solidification process of the phase change material 331, which serves as a standby cooling source for the user side 2 during the power peak period.

[0067] When the city's power peak arrives, the central air conditioning group 1 is closed or operated at a low frequency, thereby reducing the power consumption of the large power equipment air conditioner to reduce the load on the power grid and achieve the purpose of peak shaving. At this time, the room in the user side 2 exchanges heat with the envelope structure, so that the room temperature rises to the set temperature of 24℃, and the cold energy stored in the room is released to maintain the room temperature at the preset temperature. Since the room has limited cold energy storage capacity, the refrigerant water obtains cold energy from the melting process of the phase change material in the energy storage type fire-fighting water tank and provides cold energy for the user side 2. The refrigerant water releases the cold energy to the room to maintain the room temperature at about 24℃ to ensure the comfort of the human body, increase the virtual energy storage density of the central air conditioning, and prolong the dispatchable time of the power grid.

[0068] Optionally, during the city electricity peak period, the refrigerant water flow is adjusted by the 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 water pump, the controlled variable is the room temperature, and the type of the controller is a PI controller, whose expression is as follows:

[0069]

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

[0071] During the peak period, according to 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 water pump is derived as follows:

[0072]

[0073] Wherein, T r is the temperature in the room; 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 refrigerant water heat exchange amount; N is the speed of the fire water pump; ρ and c p are the density and specific heat of the fire water respectively; ΔT is the temperature difference between the inlet and outlet of the fire water tank; V c is the displacement of the fire water pump;

[0074] The first-order transfer function G(z) can be obtained by introducing correction factors a1 and b1, and is expressed as:

[0075]

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

[0077]

[0078] Affected by the external environment, the transfer function in the first-order transfer function G(z) is non-stationary, so 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 adaptive adjustment of the room temperature during the city electricity peak period. The performance index of real-time modification is:

[0079]

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

[0081]

[0082] wherein, K(k) is a gain coefficient; P(k) is an error covariance matrix.

[0083] By introducing an active control method, the rotation speed of the fire pump is adjusted to effectively respond to the fluctuation of the room environment temperature, so that the environment temperature is stabilized at the human comfortable temperature, and the control precision and system stability of the system are improved.

[0084] The embodiment is aimed at the problem that the urban power consumption peak load is large and the central air conditioner energy consumption is huge. In the urban power consumption valley period, the central air conditioner group is overclocked, and cold energy is provided for the user side and the energy storage type fire water tank, and the excess cold is stored in the phase change material in the energy storage type fire water tank and the room of the user side in advance; in the urban power consumption peak period, the central air conditioner group is low-frequency operated or turned off, and the energy storage type fire water tank provides cold energy for the user side, and the storage and release of cold energy realize virtual storage and utilization of electric energy, effectively realize the peak shaving strategy and save the peak power consumption.

[0085] In view of the problem that the virtual energy storage is limited by the room size, in the embodiment, the fire water tank provided by the building group itself is taken as the basis, the phase change cold storage ball is added in the fire water tank, in the urban power consumption valley period, the energy storage type fire water tank obtains cold energy from the central air conditioner group, the phase change material in the energy storage type fire water tank is solidified and stores cold energy; in the urban power consumption peak period, the phase change material in the energy storage type fire water tank is melted and releases cold energy, and provides cooling for the user side, so that the temperature in the room of the user side can also be stabilized at the set temperature when the central air conditioner group is low-frequency operated or turned off, and the comfort degree in the room is ensured. The setting of the energy storage type fire water tank actually increases the virtual energy storage density of the central air conditioner and prolongs the dispatchable time of the power grid.

[0086] Embodiment 2:

[0087] The embodiment illustrates and supplements the system and method in embodiment 1 through specific examples. Optionally, considering a 15-storey building with a building area of about 20,000 square meters, the summer cooling load is 600 kW, the energy storage type fire water tank 3 provides 1 hour of cooling load for the building at the peak time, and it is assumed that the initial temperature T of the water tank is 15℃. The phase change cold storage ball 33 in the energy storage type fire water tank 3 of the embodiment is analyzed. st

[0088] ​

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

[0090] Table 1 Parameters of phase change cold storage ball

[0091]

[0092]

[0093]

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

[0095] Table 2 Energy storage type fire water tank

[0096]

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

[0098] Embodiment 3:

[0099] The embodiment provides a central air conditioning system adapted to the number of phase change balls, which uses the central air conditioning system adapted to the number of phase change balls as described in Embodiment 1, comprising: the energy storage type fire water tank obtains cold energy from the central air conditioning group, 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 only describes the preferred embodiments of the present embodiment and is not used to limit the present embodiment. For those skilled in the art, the present embodiment can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present embodiment should be included in the protection scope of the present embodiment.

Claims

1. A central air conditioning system that adjusts the number of phase change balls, characterized by, The application relates to a central air conditioner group arranged in a building and a storage energy type fire-fighting water tank connected with the central air conditioner group. The storage energy type fire-fighting water tank is internally provided with a plurality of phase change cold storage balls; wherein the calculation method of the number of phase change cold storage balls in the storage energy type fire-fighting water tank is as follows: wherein, E is the cold storage capacity of the energy storage type fire water tank; Q PCM is the total cold storage capacity of the phase change cold storage balls; n is the number of phase change cold storage balls; is the volume of a single phase change cold storage ball; is the density of the phase change material; r is the latent heat of phase change of the 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 type fire water tank; Cost is the total cost of the energy storage type fire water tank; is the unit price of the phase change material; is the cost of the fire water tank body; is the volume of the fire water tank body; is the diameter of the phase change cold storage ball; is the building cooling load demand; is the heat exchange efficiency.

2. The central air conditioning system of claim 1, wherein the number of phase change balls is adapted. The storage energy type fire-fighting water tank comprises a fire-fighting water tank body and flow uniformizing plates and phase change cold storage balls arranged in the fire-fighting water tank body.

3. The central air conditioning system of claim 2, wherein the number of phase change balls is adapted. The geometric center of the top of the fire-fighting water tank body is provided with a water inlet, and the geometric center of the bottom is provided with a water outlet; the inside of the fire-fighting water tank body is internally provided with two flow uniformizing plates, and a plurality of layers of phase change cold storage balls are arranged between the flow uniformizing plates.

4. The central air conditioning system of claim 2, wherein the number of phase change balls is adapted. The flow uniformizing plates are uniformly provided with flow uniformizing holes.

5. The central air conditioning system of claim 1, wherein the number of phase change balls is adapted. The phase change cold storage ball comprises an outer shell and a phase change material arranged inside the outer shell; the phase change material comprises Na2CrO4·10H2O, KF·4H2O and C 16 H 34 .

6. The central air conditioning system of claim 1, wherein the number of phase change balls is adapted. The central air conditioner group and the storage energy type fire-fighting water tank are connected with a controller, and the controller is used for adjusting the refrigerant water flow through the self-adaptive controller to control the room temperature in a preset range during the urban power peak period.

7. The central air conditioning system of claim 6, wherein the number of phase change balls is adapted. During the peak period, the first-order transfer function of the process of adjusting the room temperature by the fire-fighting water pump speed is deduced according to the heat exchange relationship between the temperature change in the room and the refrigerant water flowing through the room. wherein, T r T is the temperature in the room; T out T is the temperature outside the room; R R is the equivalent thermal resistance; C C is the heat capacity of the gas in the room; Q Q is the heat exchange of the coolant water; N N is the rotational speed of the fire water pump; The application uses the central air conditioner system with the adaptive phase change ball number as claimed in any one of claims 1-7, wherein the storage energy type fire-fighting water tank obtains cold energy from the central air conditioner group, the phase change material in the storage energy type fire-fighting water tank is solidified and stores the cold energy; during the urban power peak period, the phase change material in the storage energy type fire-fighting water tank is melted and releases the cold energy, and the cold energy is provided to the user side. and c p respectively, the density and specific heat of the fire water; Δ T ΔT is the temperature difference between the inlet and outlet of the fire water tank; V c Q is the displacement of the fire water pump.

8. A central air conditioning system control method of adapting the number of phase change balls, characterized by, ​

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