Discontinuous operation central air conditioner operation control method

Abstract

The invention discloses a non-continuous operation central air conditioner operation control method which comprises the following steps: 1, selecting proper model calculation parameters according to a project location; secondly, the temperature and the relative humidity in the room are collected through a temperature and humidity sensor, and an indoor air enthalpy value is obtained through calculation; 3, constructing an indoor personnel thermal comfort model; and fourthly, a room control model is built, and the starting time of the room air conditioner system is obtained. The energy consumption of pre-cooling / pre-heating treatment of the non-continuously operating central air conditioner before operation of a building is started can be reduced, meanwhile, the thermal comfort level of indoor personnel is improved, and a cold and heat source system of the air conditioner is efficiently configured.

Description

Technical Field

[0001] The present invention relates to the field of energy-saving operation of central air conditioners, and in particular to room pre-cooling / pre-heating processing based on air conditioner load prediction with the goal of maximizing the operating efficiency of cold and heat sources. Background Art

[0002] Central air conditioning systems are a common means of artificial environmental conditioning in large public buildings. Common office buildings, shopping malls, theaters, and stadiums all utilize central air conditioning to meet occupants' requirements for room temperature and humidity. Furthermore, energy consumption during central air conditioning operation is a significant contributor to energy consumption in public buildings, accounting for approximately 50% of total building energy consumption. Of this, commercial buildings consume approximately 47.2% of this energy; office buildings consume approximately 46.7%; and hotels consume a whopping 50.7%.

[0003] Due to the high energy consumption of central air conditioning, public buildings typically employ two energy-saving operation strategies during non-operational periods: 1. Shutting down the air conditioning system and restarting it before the start of operation; 2. Low-frequency operation of the air conditioning system to maintain the designated operating temperature. Both approaches effectively reduce energy consumption during non-operational periods in public buildings, but they also have drawbacks. First, with the direct shutdown approach, the air conditioning startup time relies on a fixed set time. Furthermore, without predicting the air conditioning's partial load, full load operation is often used, making it impossible to predict the actual effect achieved during the operational period. Secondly, with the strategy of maintaining the indoor environment on-duty, it's difficult to accurately determine when to increase the air conditioning's cooling / heating capacity before the start of operation to ensure thermal comfort for occupants during operational hours. This strategy relies solely on the experience of operation and maintenance personnel. Therefore, a central air conditioning operation control method is urgently needed to address these issues. Summary of the Invention

[0004] In response to the practical problems encountered in the operation of the above-mentioned central air-conditioning, the present invention proposes a discontinuous operation central air-conditioning operation control method, which can realize precise pre-cooling / preheating of the building by the central air-conditioning, avoiding waste caused by excessive operation and poor comfort for personnel caused by insufficient pre-cooling and preheating.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for controlling the operation of a discontinuous central air conditioner, comprising the following steps:

[0006] The first step is to select appropriate model calculation parameters based on the project location;

[0007] The second step is to collect the temperature and relative humidity in the room through the temperature and humidity sensor to calculate the indoor air enthalpy value;

[0008] The third step is to build a thermal comfort model for indoor occupants;

[0009] The fourth step is to build a room control model to obtain the start time of the room air conditioning system.

[0010] Preferably, the model calculation parameters include the hourly cooling load calculation temperature t of the exterior wall and roof wlq , t wlm ; Hourly cooling load calculation temperature t of external window heat transfer wlc .

[0011] Preferably, the indoor air enthalpy value is calculated using a psychrometric table under the atmospheric pressure of the project location, using two parameters: temperature and relative humidity.

[0012] Preferably, the indoor occupant thermal comfort model calculates the target indoor temperature and relative humidity of the building by selecting a reasonable mean thermal sensation index (PMW).

[0013] Preferably, the hourly air-conditioning load of the room is calculated according to the room control model to obtain the start time of the room air-conditioner.

[0014] Preferably, a cold and heat source control scheme is constructed based on the room control model, and the hourly air-conditioning load is predicted before the building operation time.

[0015] Preferably, the hourly partial load factor is determined based on the hourly air-conditioning load forecast of the building, and a control plan for the cold and heat source hosts is formulated based on the partial load factor and the energy consumption of the cold and heat source hosts, with the goal of minimizing the overall energy consumption.

[0016] Compared with the prior art, the present invention has the following advantages: by constructing an environmental parameter and processing model, the model is used to obtain predicted values ​​for outdoor temperature, predicted solar heat gain, and indoor air enthalpy. A thermal comfort model for indoor occupants is constructed, and the model is used to determine the target temperature and relative humidity for air conditioning operation. A room control model is constructed, and the cumulative air conditioning load value before the room begins to be used is calculated based on the predicted outdoor temperature, solar heat gain, indoor air enthalpy, target temperature, target relative humidity, and the thermal performance of the room's enclosure. The air conditioning system startup time for the room is determined based on the cumulative air conditioning load value, the enthalpy difference between the air conditioning supply and return air, and the supply air volume. A cold and heat source control model is constructed, and based on the room air conditioning system startup time, the central air conditioning part load rate during non-use hours is calculated. The number of operating cold and heat source units and the operating part load rate of each unit are determined based on the operating characteristic curves and part load rates of the cold and heat source units. Using environmental parameters and data processing models, thermal comfort models, room control models, and cooling and heating source control models, the system calculates the operating time of each room's air conditioning system, the number of cooling and heating source units activated, and the operating frequency. This reduces energy consumption during pre-cooling / pre-heating of non-continuously operating central air conditioning units before building operations begin, while also improving indoor thermal comfort and enabling efficient configuration of cooling and heating source systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0018] Hereinafter, the present invention will be described in detail through exemplary embodiments.

[0019] A method for controlling the operation of a non-continuous central air conditioner, see Figure 1 , including the following steps: 1. Model parameter selection and processing

[0020] 1.1 The simplified calculation method is used for the cooling load of room air conditioners in summer. The hourly cooling load of each item is calculated according to the non-steady-state method. The hourly cooling load calculation temperature of the room's external envelope structure adopts the correction coefficient method of representative cities and locations. The hourly cooling load calculation temperature of the exterior wall and roof is t wlq , t wlm Correction factors for representative cities and locations are as follows:

[0021]

[0022]

[0023]

[0024]

[0025] 1.2 Hourly cooling load calculation temperature t of external window heat transfer wlc ,According to the city selection, the value between two moments is determined by linear interpolation;

[0026] 1.3 Calculation of the average daily outdoor temperature in summer t p Select by city;

[0027] 1.4 Solar radiation cooling load coefficient C through standard unshaded glass clC Use data representing different orientations of the city;

[0028]

[0029] 1.5 Maximum solar radiation intensity through standard glass windows in summer D Jmax Determined by the direction of the city and exterior windows;

[0030] 1.6 Collect indoor air temperature and relative humidity. Use the psychrometric table corresponding to the city where the project is located to obtain the indoor air enthalpy value h i ;

[0031] 2. Constructing personnel thermal comfort model

[0032] 2.1 Parameter selection, the mean thermal sensation index (PMV) scale is as follows:

[0033] Table 1.1 Seven-level thermal sensation scale

[0034] PMV value Thermal sensation +3 hot +2 warm +1 slightly warm 0 Moderate -1 Slightly cool -2 cold -3 cold

[0035] The range of the average thermal sensation index (PMW) adopted in the present invention is -0.5≤PMW≤0.5.

[0036] 2.2 Target temperature and relative humidity calculation

[0037] The target temperature, relative humidity and PMW have the following relationship:

[0038] PMW=(0.303e -0.036M +0.028)×{(MW)-3.05×10 -3 ×[5733-6.99(MW)-P a ]-0.42×[(MW)-58.15]-1.7×10 -5 M(5867-P a )-0.0014M(34-t n )-3.96×10 -8 f cl [(t cl +273) 4 -(tr +273) 4 ]-f cl h c (t cl -t n )}

[0039] t cl = 35.7 - 0.028(M-W)-I cl {3.96x10 -8 f cl x[(t cl +273) 4 -(t r +273) 4 ]+f cl h c (t cl -t n )}

[0040]

[0041] In the formula:

[0042] PMW is the average thermal sensation index, and the value range of the present application is -0.5≤PMW≤0.5;

[0043] M is the metabolic rate of different activities, unit W / m2; according to the building function, the following data is selected:

[0044]

[0045] W is the effective mechanical power, unit W / m2;

[0046] I cl is the clothing thermal resistance, unit m2·K / W; 0.105 in summer and 0.200 in winter.

[0047] f cl is the clothing surface area coefficient;

[0048] t n is the indoor target temperature, ℃;

[0049] t r is the average radiation temperature, ℃;

[0050] v ar is the indoor relative wind speed, unit m / s;

[0051] P a is the water vapor partial pressure, unit Pa;

[0052] h c is the convective heat transfer coefficient, unit W / (m2·K);

[0053] t cl is the surface temperature of the clothing, in °C;

[0054] 3. Building a room air conditioning control model

[0055] 3.1 Air conditioning load forecast

[0056] (1) Room hourly load forecast

[0057] During the air conditioning pre-cooling process before the building is put into operation, the cooling load of the room at the time of calculation mainly includes: heat transferred from the enclosing structure and heat from solar radiation.

[0058] q i冷 =q i围 +q i辐

[0059] In the formula

[0060] q i冷 is the room cooling load at time i, in kW;

[0061] q i围 is the cooling load generated by the room enclosure structure at time i, in kW;

[0062] q i辐 is the cooling load generated by solar radiation at time i, in kW;

[0063] q i围 =K 外墙 ×F 外墙 ×(t wlq -t n )+K 屋面 ×F 屋面 ×(t wlm -t n )+K 外窗 ×F 外窗 ×(t wlc -t n )+K 内墙 ×F 内墙 ×(t p -t n )

[0064] In the formula

[0065] K 外墙 is the heat transfer coefficient of the exterior wall, unit: W / (㎡·℃);

[0066] F 外墙 is the heat transfer area of ​​the exterior wall, in m2;

[0067] t wlq The hourly cooling load calculation temperature of the exterior wall, in °C;

[0068] t n Room target temperature, unit ℃;

[0069] K 屋面 Roof heat transfer coefficient, unit W / (㎡·℃);

[0070] F 屋面 Roof heat transfer area, unit㎡;

[0071] t wlm Roof heat transfer hourly cooling load calculation temperature, unit ℃;

[0072] K 外窗 Outside window heat transfer coefficient, unit W / (㎡·℃);

[0073] F 外窗 Outside window heat transfer area, unit㎡;

[0074] t wlc Outside window heat transfer hourly cooling load calculation temperature, unit ℃;

[0075] K 内墙 Internal wall heat transfer coefficient, unit W / (㎡·℃);

[0076] F 内墙 Internal wall area, only calculate the internal partition wall of adjacent space without air conditioning system, unit㎡;

[0077] t p Summer outdoor calculation daily average temperature, unit ℃;

[0078] q i辐 = C clC × C w × C n × C s × D Jmax × F c

[0079] In the formula:

[0080] C clC Solar radiation cooling load coefficient through standard glass without shading;

[0081] C w External shading correction coefficient;

[0082] C n Internal shading correction coefficient;

[0083] C s Glass correction coefficient;

[0084] D Jmax Maximum value of summer solar heat radiation;

[0085] F c Net area of ​​exterior window glass, unit: m2.

[0086] During the air conditioning preheating process before the building is put into operation, the formation of room heat load at the time of calculation mainly includes heat transfer of the enclosing structure.

[0087] q i热 =α×K×F×(t n -t w )

[0088] In the formula

[0089] α is the temperature difference correction coefficient of the enclosure structure, which is selected according to the following table;

[0090] Enclosure structure characteristics α Exterior walls, roofs, floors, and floors connected to the outdoors, etc. 1.00 Floor slabs above dead ceilings and non-heated basements ventilated to outdoor air, etc. 0.90 Partition walls adjacent to unheated stairwells with exterior doors and windows (1-6 storey buildings) 0.60 Partition walls adjacent to unheated stairwells with exterior doors and windows (7-30 storey buildings) 0.50 Floor slab above non-heated basement, when there are windows on the exterior wall 0.75 The floor above the unheated basement has no windows on the exterior wall and is above the outdoor floor 0.60 The floor above the unheated basement has no windows on the exterior wall and is located below the exterior grade 0.40 Partition walls adjacent to unheated rooms with exterior doors and windows 0.70 Partition walls adjacent to unheated rooms without exterior doors or windows 0.40

[0091] K is the heat transfer coefficient of the enclosure structure, unit: W / (㎡·K);

[0092] F is the area of ​​the enclosure structure, in m2;

[0093] t w Calculate the outdoor temperature for heating in °C, selected according to the city where the building is located;

[0094] (2) Calculation of indoor air enthalpy difference

[0095] The amount of heat and cold processed by the pre-cooling / pre-heating treatment of the room should also include the difference between the enthalpy value of the air in the treatment room and the enthalpy value of the air corresponding to the target state.

[0096] Q 内 =A×H×ρ×|h i -h n | / 3600

[0097] Where:

[0098] Q 内 The cooling / heating capacity required for indoor air treatment, in kWh;

[0099] A is the room area, unit: m2;

[0100] H is the net height under the ceiling of the room, in meters;

[0101] ρ is the dry air density at the corresponding indoor temperature and relative humidity, in kg / m 3 ;

[0102] h i is the indoor air enthalpy value, unit is KJ / kg;

[0103] h n Air enthalpy at target indoor temperature and relative humidity, in kJ / kg;

[0104] 3.2 Determine room control strategy

[0105] Taking the time when the building starts operating as the benchmark, the predicted value of the room air-conditioning load at each time is calculated forward with a calculation step of 15 minutes.

[0106] time <![CDATA[i0]]> ​ <![CDATA[i2]]> …… i n ]] Air conditioning load <![CDATA[q0]]> q1 <![CDATA[q2]]> …… q n ]]>

[0107] Calculate the start time of the room air conditioning system. The start time is determined by the following relationship:

[0108]

[0109] In the formula

[0110] i n Indicates the starting time of the nth time step before the building operation time;

[0111] ρ 送 The dry air density of the room in the air-conditioning supply state, unit is kg / m;

[0112] h 回 is the enthalpy value corresponding to the return air state point of the room air conditioning system, unit is KJ / kg;

[0113] h 送 is the enthalpy value corresponding to the air supply state point of the room air conditioning system, unit is KJ / kg;

[0114] The calculated i n This is the time when the air conditioner in the room is turned on;

[0115] Optimization of four cooling and heating source control schemes

[0116] List the air conditioning on-times and corresponding room air conditioning loads (including the indoor air enthalpy difference) for all rooms in the building, and calculate the central air conditioning hourly load and part-load factor. Based on the part-load factor and the efficiency curves of the cooling and heating source units, develop an operation plan for the cooling and heating source units with the goal of minimizing overall energy consumption.

[0117]

[0118]

[0119] The following is an example of summer air conditioning operation in a six-story office building in Qingdao, Shandong Province. The building faces due south and north, and operates from 8:30 AM to 5:30 PM on weekdays. During non-operating hours, there are no lights, electrical equipment, or people staying for extended periods. The exterior wall construction and heat transfer performance are as follows:

[0120] The roofing methods and heat transfer performance are as follows:

[0121]

[0122]

[0123] The room divisions and functions of the building plan are shown in the attached figure.

[0124] 1. Model parameter selection and processing

[0125] 1.1 The office building is located in Qingdao, Shandong Province, and the corresponding representative city is Xi'an. The correction value is -3. According to the corresponding exterior wall construction, representative city and correction value, the hourly cooling load calculation temperature t of the office building's exterior walls in different directions is wlq As shown in the following table (only the times before the operating hours are listed):

[0126]

[0127] Hourly cooling load calculation temperature t of office building roof wlm As shown in the following table (only the times before the operating hours are listed):

[0128]

[0129] 1.2 Hourly cooling load calculation temperature t of external window heat transfer wlc As shown in the following table, the values ​​between two moments are determined using linear interpolation (only moments before the operating time are listed):

[0130]

[0131]

[0132] 1.3 Calculation of the average outdoor temperature in Qingdao during summer p 27.3℃;

[0133] 1.4 Solar radiation cooling load coefficient C through standard unshaded glass clC The data representing different directions of cities are used. The representative city for Qingdao is Xi'an. The specific values ​​are shown in the following table:

[0134]

[0135] 1.5 Maximum solar radiation intensity through standard glass windows in summer D Jmax Determined by the direction of the city and exterior windows;

[0136] City East South West north <![CDATA[青岛D Jmax ]]> 534 265 534 146

[0137] 1.6 Collect indoor air temperature and relative humidity. Use the psychrometric table corresponding to the city where the project is located to obtain the indoor air enthalpy value h i ;

[0138] 2. Constructing personnel thermal comfort model

[0139] 2.1 Parameter selection: The range of mean thermal sensation index (PMW) is -0.5≤PMW≤0.5.

[0140] 2.2 Calculation of target temperature and relative humidity: The target temperature of the office room in summer is 26℃ and the relative humidity is 58%. The outdoor atmospheric pressure in Qingdao in summer is 100040Pa. The air enthalpy corresponding to the target temperature and relative humidity is 57.76KJ / kg. 干空气 .

[0141] Three-room air conditioning control model

[0142] Taking the time when the building starts operating as the benchmark, the predicted value of the room air conditioning load at each time is calculated forward with a calculation step of 15 minutes (excluding the indoor air enthalpy difference).

[0143]

[0144] Based on the cooling capacity of the air conditioning terminal in each room, the start time of the room air conditioning system is calculated. The calculation results of the start time are as follows:

[0145]

[0146]

[0147] Four cooling and heating source control scheme

[0148] The office building's maximum summer cooling load is 540 kW. Four air-source heat pump units are used for the cooling system, with a design cooling capacity of 133.3 kW. The equipment capacity control range is 50% to 100%. According to the cooling system's product manual, energy consumption at different cooling capacities is shown in the following table:

[0149]

[0150] The hourly air conditioning cooling load and part load factor statistics for the central air conditioning pre-cooling stage are shown in the following table.

[0151]

[0152] Based on the partial load factor and the power consumption of the cold and heat source hosts during partial load operation, the comprehensive energy consumption under different operation schemes is analyzed.

[0153]

[0154] Comparing the power consumption of the two operating schemes during pre-cooling operation, Scheme 1 consumed a total of 52.2 kWh, while Scheme 2 consumed a total of 46.45 kWh. Scheme 2 should be adopted as the cooling and heat source control scheme for the pre-cooling phase, saving 11% of power consumption during the pre-cooling phase before the office building is put into use each day.

[0155] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for controlling the operation of a discontinuous central air conditioner, characterized in that: The following steps are involved: The first step is to select appropriate model calculation parameters based on the project location; The second step is to collect the temperature and relative humidity in the room through the temperature and humidity sensor to calculate the indoor air enthalpy value; The third step is to build a thermal comfort model for indoor occupants; The fourth step is to build a room control model to obtain the start time of the room air conditioning system.

2. The method for controlling the discontinuous central air conditioner operation according to claim 1, characterized in that: The model calculation parameters include the hourly cooling load calculation temperature t of the exterior wall and roof wlq , t wlm ; Hourly cooling load calculation temperature t of external window heat transfer wlc .

3. The method for controlling the discontinuous central air conditioner operation according to claim 1, characterized in that: The indoor air enthalpy value is calculated using the enthalpy hygrometer under the atmospheric pressure of the project location, using the two parameters of temperature and relative humidity.

4. The method for controlling the discontinuous central air conditioner operation according to claim 1, characterized in that: The indoor occupant thermal comfort model calculates the indoor target temperature and relative humidity of the building by selecting a reasonable mean thermal sensation index (PMW).

5. The method for controlling the discontinuous central air conditioner operation according to claim 1, characterized in that: The hourly air-conditioning load of the room is calculated according to the room control model to obtain the start time of the room air-conditioner.

6. The method for controlling the discontinuous central air conditioner operation according to claim 5, characterized in that: A cooling and heating source control scheme is constructed based on the room control model, and hourly air-conditioning loads are predicted before the building operation time.

7. The method for controlling the discontinuous central air conditioner operation according to claim 6, characterized in that: Determine the hourly partial load factor based on the hourly air-conditioning load forecast of the building, and formulate a control plan for the cold and heat source main unit based on the partial load factor and the energy consumption of the cold and heat source main unit with the goal of minimizing the overall energy consumption.

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