CN108151246A - Air quantity variable air conditioner wind system Optimization of Energy Saving control method and device - Google Patents
Air quantity variable air conditioner wind system Optimization of Energy Saving control method and device Download PDFInfo
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Abstract
The present invention discloses a kind of air quantity variable air conditioner wind system Optimization of Energy Saving control method and device, establishes the hydraulic calculation model of air quantity variable air conditioner wind system, related data is obtained by data acquisition module；According to the mathematical model of each component of air conditioning system with variable, the pressure drop in each circuit is calculated, finds out the least favorable circuit in wind system, calculates the pressure drop in least favorable circuit in each circuit at this time, and in this, as the pressure head of wind turbine；Using the sum of the air quantity needed for each air-conditioned room and inleakage as the setting total blast volume of air conditioning system with variable, by air quantity variable air conditioner wind system least favorable loop pressure drop and the setting total blast volume of system, it is brought into the mathematical model of fan performance curve, calculate the frequency needed for wind turbine at this time, wind turbine frequency is adjusted by frequency converter, realizes the optimal control of wind turbine in air quantity variable air conditioner wind system.The present invention can improve the control effect of each end room air quantity in air conditioning system with variable, and with certain energy-saving benefit.
Description
Technical Field
The invention relates to an optimized energy-saving control method and device for an air system of a variable air volume air conditioner. In particular to an optimized energy-saving control method and device for an air system of a variable air volume air conditioner.
Background
Along with the improvement of the living standard of people in the development of society, the environment in the building is more and more emphasized by people, and the application of the variable air volume air conditioning system with higher comfort and easy adjustability is gradually and widely realized by the application and development of a direct digital control technology and a building automation system technology in the heating ventilation air conditioning field. In a control loop of the variable air volume air conditioning system, a control strategy of a fan directly influences the control effect of the air volume of each terminal room, so that the thermal comfort of the rooms and the transmission and distribution energy consumption of the air system are influenced, and therefore, the control of the fan is a key link of the control of the variable air volume air conditioning system.
In the field of air volume control research of variable air volume air conditioning systems, most of the air volume control methods are used for researching an optimal control method of a fan in an air system, and the research is mainly based on machine learning methods such as a genetic algorithm, a particle swarm algorithm, a self-adaptive algorithm and the like. In short, a large amount of actual data is used to perform regression analysis of multiple iterative learning, and then the result after iterative analysis calculation is obtained. The whole process is like a black box process, the physical significance of each part of the variable air volume system cannot be shown, and the control and energy conservation of the air conditioning system cannot be analyzed from the structural angle of the system. In the actual operation process of the variable air volume air-conditioning system, the air volume of the system changes in real time along with the change of the load at the tail end of each room, the strong dynamic characteristic is embodied, and the coupling exists among all control loops of the variable air volume air-conditioning system, so that the stability of the system in operation is poor.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an optimized energy-saving control method and device for an air volume-variable air-conditioning air system based on a hydraulic characteristic dynamic change model, which can improve the control effect of the air volume of each terminal room in the air volume-variable air-conditioning system and have certain energy-saving benefit.
In order to solve the technical problems, the technical scheme of the invention is as follows:
an optimized energy-saving control method for an air system of a variable air volume air conditioner comprises the following steps:
1) determining a fan model in the variable air volume air-conditioning air system and a hydraulic model of an electric air valve in a variable air volume tail end VAV-box according to a manufacturer and initial debugging data, obtaining the hydraulic calculation model of the variable air volume air-conditioning air system by utilizing data fitting of air pipes with different shapes and specifications in an on-the-way loss calculation table and data of an air pipe local resistance coefficient table, and solidifying each model parameter in configuration software of an upper computer;
2) the method comprises the steps of obtaining running data of a fan, air quantity of an air pipe, set temperature and actual temperature of an air-conditioning room, set air quantity Qi of a variable air quantity tail end VAV-box and set valve position theta of the variable air quantity tail end VAV-box through a data acquisition modulei；
3) Reading the set air quantity Qi of each variable air quantity terminal VAV-box and the set valve position theta of the electric air valvei(ii) a According to the mathematical model of each component of the variable air volume air-conditioning system, the pressure drop of each loop of the variable air volume air-conditioning system under the working condition is calculated, and the most important loop in the air system is found outThe adverse circuit is characterized in that the opening degree of an electric air valve in a variable air volume tail end VAV-box on the most adverse circuit is set to be in a fully-opened state, the pressure drop of the most adverse circuit in each circuit at the moment is calculated and is used as the pressure head of the fan;
4) the sum of the air volume and the air leakage volume required by each air-conditioning room is taken as the set total air volume of the variable air volume air-conditioning system, the pressure drop of the worst loop of the variable air volume air-conditioning system and the set total air volume of the system are brought into a mathematical model of a fan characteristic curve, the frequency required by the fan at the moment is calculated, the frequency of the fan is adjusted through a frequency converter, and the optimal control of the fan in the variable air volume air-conditioning system is realized.
As a further improvement of the present invention, step 2) is specifically:
the method comprises the steps of obtaining the running frequency and the power consumption of a fan through a fan data collector, obtaining the set temperature and the actual temperature of an air-conditioning room through an indoor wall-mounted module which is matched with and installed on the air-conditioning room through a variable air volume terminal VAV-box, obtaining the air volume passing through each variable air volume terminal VAV-box through a cross air volume sensor on the variable air volume terminal VAV-box, obtaining the set air volume of the air-conditioning room and the set valve position of a variable air volume terminal VAV-box electric air valve through calculation of a programmable controller on the variable air volume terminal VAV-box, obtaining the air speed of each part of an air system through data obtained through air speed sensors installed at each part of an air pipe, and further obtaining the air volume passing through different air pipes through calculation of different specifications of air.
As a further improvement of the invention, the hydraulic calculation model of the variable air volume air-conditioning air system comprises an on-way resistance loss calculation model and a local resistance loss calculation model;
the on-way resistance loss calculation model is obtained by fitting impedance and wind speed by using data in a wind pipe on-way loss calculation table to obtain the corresponding relation between the wind speed and the impedance of wind pipes with different specifications, and the relation between the wind speed and the impedance is as follows:
S＝aV2+bV+c
in the formula: s-impedance of pipe section, Pa/m;
v is wind speed in the wind pipe, m/s;
a, b and c are coefficients determined by the shape and specification of the air duct;
the calculation formula of the local resistance loss is as follows:
in the formula: ζ -local drag coefficient;
v-air velocity in the local resistance element, m/s;
rho-air density, Kg/m3。
As a further improvement of the method, the specific calculation steps of the hydraulic calculation model of the variable air volume air-conditioning air system are as follows:
and calculating the wind speed in each numbered pipe section as follows by using the set wind volume of the VAV-box at the tail end of the variable wind volume when the set wind volume is reached:
in the formula: v. ofi-air flow rate, m/h, in the pipe sections of different numbers;
Qbox-i-variable air volume end VAV-box air volume required for each room, m3/h；
AiCross-sectional areas of differently numbered pipe sections, m2；
And fitting the relationship between the impedance and the wind speed of the air pipes according to the flow velocity in each pipe section by using the data of the air pipes of various materials, shapes and specifications in a calculation table to obtain an impedance mathematical calculation formula of the on-way resistance of the air pipes:
Sj＝avj 2+bvj+c (j∈1～5)
in the formula: sjImpedance of pipe sections of different dimensions, kg/m7；
vj-air flow rate, m/h, in the pipe sections of different numbers;
the air conditioning air system is divided into a fixed air valve impedance part and an air duct impedance part:
Si＝Sd+Svalve
in the formula: siImpedance of differently numbered sections of pipe, kg/m7；
Svalve-air valve impedance of different specifications, kg/m7；
Sd-air duct impedance under the same numbered duct section, kg/m7；
Air pipe impedance S of same numbered pipe sectiondThe resistance of each numbered pipe section is obtained according to the method, and the pressure drop of the air pipe of each numbered pipe section under the corresponding air quantity is obtained by combining the set air quantity of the corresponding VAV-box read by the upper computer:
in the formula: delta PiNumbering the pipe section pressure drop values under the condition of corresponding wind speed and valve opening;
calculating the pressure drop value of each loop by combining the structural form of the actual air pipe system of the variable air volume experiment platform, comparing the pressure drop values of the loops of each room on the experiment platform, and finding out the worst loop of the variable air volume air conditioning system; and setting the opening degree of an electric air valve in a VAV-box at the tail end of the variable air volume on the most unfavorable loop to be in a full-open state, calculating the pressure drop of the most unfavorable loop in each loop at the moment, and taking the pressure drop as the pressure head of the fan to obtain a mathematical model of the air duct system in the variable air volume air-conditioning system constructed by taking the variable air volume experimental platform as a template.
As a further improvement of the invention, when the actual temperature or the set temperature of the air-conditioned room is changed, the set valve position of the variable air volume end VAV-box electric air valve in the air-conditioned room and the set air volume of the air-conditioned room are correspondingly changed, and the steps 2) -4) are repeated.
An optimized energy-saving control device of a variable air volume air conditioning system based on a hydraulic characteristic dynamic change model comprises an upper computer, a lower computer programmable controller, an expansion module, a fan data collector, an air speed sensor, a fan frequency converter, a variable air volume tail end VAV-box and an indoor wall-hanging module; wherein,
the fan data acquisition unit is used for acquiring the running frequency and the power consumption of the fan;
the variable air volume tail end VAV-box is matched with an indoor wall-mounted module arranged in an air-conditioning room to obtain the set temperature and the actual temperature of the air-conditioning room, a cross air volume sensor on the variable air volume tail end VAV-box obtains the air volume passing through each variable air volume tail end VAV-box, and a programmable controller on the variable air volume tail end VAV-box calculates the set air volume of the air-conditioning room and the set valve position of a variable air volume tail end VAV-box electric air valve;
the wind speed sensors are arranged at all parts of the wind pipe and used for acquiring data to obtain wind speeds of all parts of the wind system;
the lower computer programmable controller and the expansion module control the fan data collector, the wind speed sensor, the variable air volume tail end VAV-box and the indoor wall hanging module to collect related data; the lower computer programmable controller and the expansion module are communicated with the Ethernet switch through the communication module and then connected with the upper computer, and the upper computer adjusts the frequency of the fan by controlling the fan frequency converter to realize the optimal control of the fan in the variable air volume air conditioning system.
The indoor wall-hung module comprises a temperature and humidity sensor.
The invention has the following beneficial effects:
the invention provides an energy-saving optimization control method of a variable air volume air conditioning system based on a hydraulic characteristic dynamic change model, which takes the minimum pressure drop of the variable air volume air conditioning system as a control optimization target on the premise of meeting the air volume required by an air conditioning room according to models of all parts in the variable air volume air conditioning air system. The method considers the condition that the system impedance changes along with the change of the system wind speed, judges the most unfavorable loop of the wind system under the real-time operation condition of the variable air volume system, and utilizes the self-balancing property of the fluid pipe network to calculate the minimum pressure drop value of the most unfavorable loop of the system when the air volume at the tail end of a room is met in real time on line according to the opening condition of an air valve on the most unfavorable loop, thereby controlling the fan and obtaining the energy-saving operation condition of the fan. The energy-saving optimization control method of the variable air volume air system based on the hydraulic characteristic dynamic change model belongs to feed-forward control, and the control basis is a set value calculated in advance by a control system, so that the control is stable, and the oscillation cannot occur.
The control device of the invention is based on the existing variable air volume air conditioning system, and controls a fan data collector, an air speed sensor, a variable air volume tail end VAV-box and an indoor wall-hung module to collect relevant data through a lower computer programmable controller and an expansion module; the lower computer programmable controller and the expansion module are communicated with the Ethernet switch through the communication module and then connected with the upper computer, and the upper computer adjusts the frequency of the fan by controlling the fan frequency converter, so that the optimal control of the fan in the variable air volume air conditioning air system is realized, and the automatic control process is realized. The air quantity control effect of each tail end room in the variable air quantity air conditioning system can be improved, and certain energy-saving benefit is achieved.
Drawings
FIG. 1 is a schematic diagram of the structure of the apparatus of the present invention;
FIG. 2 is a flow chart of a method embodying the present invention;
FIG. 3 is a graph of an example of the calculation of the method of the present invention.
Detailed Description
The invention is further illustrated by the following specific examples:
as shown in fig. 1, the device of the invention comprises an upper computer 1, an ethernet switch 2, a communication module 3, a lower computer programmable controller, an expansion module 4, a wind speed sensor 5, a fan frequency converter 6, a variable air volume terminal VAV-box 7 and an indoor wall-hanging module 8. The upper computer 1 is an industrial control computer, the Ethernet switch 2 is an 8-port industrial Ethernet switch, the communication module 3 is a CP243 Ethernet module, the lower computer programmable controller and the expansion module 4 are Siemens PLC S7-200CPU and EM235 expansion modules, the air speed sensor 5 is a hot wire air speed sensor, the tail end VAV-box 7 of the variable air volume is a Royal single-air-duct single-cooling pressure-independent variable air volume box and comprises a cross air volume sensor, an electric air valve, a controller 4 and an actuator, and the indoor wall-hanging module 8 is a matched device of the tail end VAV-box 7 of the variable air volume and comprises a temperature and humidity sensor.
As shown in fig. 2, the invention provides an optimized energy-saving control method for a variable air volume air conditioning system based on a hydraulic characteristic dynamic change model, which comprises the following steps:
the method comprises the steps of firstly, determining a fan model in the variable air volume air-conditioning air system and a hydraulic model of an electric air valve in a variable air volume tail end VAV-box according to factory or initial debugging data, obtaining the hydraulic calculation model of the variable air volume air-conditioning air system according to data of air pipes with different shapes and specifications in a path loss calculation table and data of an air pipe local resistance coefficient table in a design manual, and solidifying parameters of each model in configuration software of an upper computer.
And secondly, acquiring running data of a fan, air quantity of an air pipe, set temperature and actual temperature of an air-conditioning room, air quantity of a variable air quantity terminal VAV-box and set valve position and actual valve position of a variable air quantity terminal VAV-box electric air valve through a data acquisition module. These parameters are stored in a time series and the data sampling interval can be set to 60 seconds.
The configuration software obtains the running frequency and the power consumption of the fan through a fan data collector, obtains data through an indoor wall-mounted module which is matched with the variable air volume tail end VAV-box and installed in an air-conditioning room to obtain the set temperature and the actual temperature of the air-conditioning room, obtains the air volume passing through each variable air volume tail end VAV-box through a cross air volume sensor on the variable air volume tail end VAV-box, obtains the set air volume of the air-conditioning room and the set valve position of the variable air volume tail end VAV-box electric air valve through calculation of a programmable controller on the variable air volume tail end VAV-box, obtains the air speed of each part of an air system through the data obtained by air speed sensors installed at each part of an air pipe, and further obtains the air volume passing through different air pipes through calculation of different specifications of air pipe sizes.
And thirdly, calculating the pressure drop of the air system loop at the tail end of the air-conditioning room according to the set air volume of each air-conditioning room and the set valve position of the VAV-box electric air valve at the tail end of the variable air volume, comparing the pressure drop values of the loops, and determining the most adverse loop of the variable air volume air-conditioning air system at the moment.
And fourthly, assigning the opening degree of the electric air valve in the variable air volume terminal VAV-box on the worst loop to be 95% (in a fully open state), calculating the pressure drop of the worst loop at the moment, and taking the pressure drop as the pressure head of the fan.
It should be noted that in the whole control strategy, the valve opening is assigned manually. The value is only assigned in the calculation process, the variable air volume tail end electric air valve is not actually adjusted, the tail end is provided with a control loop, and if the value is forcibly adjusted, the system is disturbed.
And fifthly, taking the sum of the set air volume of each air-conditioning room and the air leakage volume at the interface of each air pipe as the set air volume of a fan of the variable air-conditioning air system.
And sixthly, bringing the pressure drop of the worst loop of the variable air volume air-conditioning air system and the set air volume of the fan of the variable air volume air-conditioning air system into a mathematical model of a fan characteristic curve, calculating the frequency required by the fan at the moment, and adjusting the frequency of the fan through a variable frequency controller of the fan to realize the optimal control of the fan of the variable air volume air-conditioning system.
Seventhly, when the actual temperature or the set temperature of the air-conditioning room changes, the set valve position of the VAV-box electric air valve at the variable air volume end in the air-conditioning room and the set air volume of the air-conditioning room correspondingly change. Thus, the second to sixth steps are repeated.
In this example, the hydraulic calculation model of the variable air volume air conditioning system is described as follows:
due to the change of the air volume of the air-conditioning room, the resistance of the air valve is changed in real time due to the change of the opening degree of the tail end electric air valve in the variable air volume air-conditioning air system, and the impedance of the air pipe is also changed in real time along with the change of the air speed in the air pipe. In order to obtain the instantaneous impedance of the air system of the variable air volume air conditioner at a certain moment, the complex process of directly calculating the impedance of the air pipe is avoided exceeding the calculation range of the programmable controller 4. The hydraulic calculation model of the variable air volume air conditioning system in the method comprises an on-way resistance loss calculation model and a local resistance loss calculation model.
The on-way resistance loss calculation model is obtained by fitting impedance and wind speed by using data in a wind pipe on-way loss calculation table in a practical heat supply and air conditioner design manual to obtain the corresponding relation between the wind speed and the impedance of wind pipes with different specifications. The specific method is that for air pipes with different specifications, a formula (1) for calculating the pressure drop of the air pipes is used for deducing a formula (2):
ΔP＝SQ2(1)
and respectively carrying out numerical value fitting according to the air pipe impedances corresponding to different air speeds under the air pipes with the same specification to obtain a relational expression (3) of the air speed and the impedance under a certain specific specification.
S＝aV2+bV+c (3)
In the formula: s-impedance of pipe section, Pa/m;
v is wind speed in the wind pipe, m/s;
a, b and c are coefficients determined by the shape and specification of the air duct.
The method of the invention separately considers two factors influencing the on-way resistance of the air pipe, namely the air pipe size structure and the air speed of the pipeline, and is simpler than the method of directly calculating the on-way resistance of the air pipe according to a formula, thereby solving the problems that the air speed provided by a table look-up calculation method is not comprehensive and the value of an interpolation method is not accurate enough. The fitting data uses a pipe section pressure loss calculation table in a design manual, and has high reliability. Compared with a simplified algorithm of on-the-way resistance provided in a practical heating and air conditioning design manual, the method can more accurately reflect the real-time change of the impedance of the variable air volume air system.
The calculation formula of the local resistance loss is formula (4):
in the formula: ζ -local drag coefficient;
v-air velocity in the local resistance element, m/s;
rho-air density, Kg/m3。
The local resistance coefficient values are also obtained by table lookup.
As shown in fig. 3, a hydraulic calculation model of the variable air volume air-conditioning air system is demonstrated by using an example. Assuming that the arrangement and specification of air pipes of the variable air volume air conditioning air system are shown in fig. 3, the air pipes are made of galvanized steel sheets. The air supply pipe of the experimental platform is divided into the following parts, and calculation is respectively carried out. Calculating the wind speed in each numbered pipe section as shown in the formula (5) by using the set wind volume of the variable wind volume terminal VAV-box when the wind volume reaches the set wind volume state:
in the formula: v. ofi-air flow rate, m/h, in the pipe sections of different numbers;
Qbox-i-variable air volume end VAV-box air volume required for each room, m3/h；
AiCross-sectional areas of differently numbered pipe sections, m2。
According to the flow velocity v in each pipe section1,v2,v3,v4,v5,v6,v7And fitting the relation between the impedance and the wind speed by using the data of the wind pipes of various materials, shapes and specifications in the calculation table to obtain an impedance mathematical calculation formula (6) of the on-way resistance of the wind pipes. The method of the invention assumes that the used rectangular air pipe data is fitted, and the impedance-fan fitting coefficients of air pipes with different specifications are shown in the following table 1:
Sj＝avj 2+bvj+c (j∈1～5) (6)
in the formula: sjImpedance of pipe sections of different dimensions, kg/m7；
vj-air flow rate, m/h, in the pipe sections of different numbers;
TABLE 1 fitting coefficient table of the impedance-wind speed of galvanized steel sheet wind pipe under different specifications
The impedance of each pipe section number is composed of the on-way resistance and the local resistance of the pipe section and the resistance of an electric air valve in a VAV-box at the tail end of variable air volume, wherein the on-way resistance and the local resistance are determined after the size and the form of a pipe network are determined, and the resistance is only related to the air speed in the air pipe; the electric air valve in the VAV-box of the variable air volume air conditioner has the advantage that the resistance coefficient of the air valve is changed all the time due to the real-time change of the opening of the electric air valve. Therefore, the air conditioning system is divided into a constant impedance part and a variable impedance part, as shown in formula (7)
Si＝Sd+Svalve(7)
In the formula: siImpedance of differently numbered sections of pipe, kg/m7；
Svalve-air valve impedance of different specifications, kg/m7；
Sd-constant impedance under the same numbered pipe section, kg/m7；
Constant impedance S of same number pipe sectiondConsisting of the on-way and local coefficients of resistance of the respective pipe sections. And (3) calculating the impedance of each numbered pipe section according to the method, and combining the set air volume of the corresponding VAV-box read by the upper computer to obtain the pressure drop of the air pipe of each numbered pipe section under the corresponding air volume, wherein the pressure drop is as shown in a formula (8):
in the formula: delta PiNumbering the pipe section pressure drop values under the condition of corresponding wind speed and valve opening.
And calculating the pressure drop value of each loop by combining the structural form of the actual air pipe system of the variable air volume experimental platform.
And comparing the pressure drop of each loop to find out the most unfavorable loop of the variable air volume air conditioning system. The method is a mathematical model of the air duct system in the variable air volume air conditioning system constructed by taking the variable air volume experimental platform as a template.
Finally, it should be noted that the above examples are only for illustrating the technical solutions of the present invention, and are not intended to limit the embodiments. It will be apparent to those skilled in the art that various other changes and modifications can be made in the above-described embodiments without departing from the spirit and scope of the invention, and it is intended that all such changes and modifications be within the scope of the invention as defined by the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. An optimized energy-saving control method for an air system of a variable air volume air conditioner is characterized by comprising the following steps:
1) determining a fan model in the variable air volume air-conditioning air system and a hydraulic model of an electric air valve in a variable air volume tail end VAV-box according to a manufacturer and initial debugging data, obtaining the hydraulic calculation model of the variable air volume air-conditioning air system by utilizing data fitting of air pipes with different shapes and specifications in an on-the-way loss calculation table and data of an air pipe local resistance coefficient table, and solidifying each model parameter in configuration software of an upper computer;
2) tong (Chinese character of 'tong')The data acquisition module acquires fan operation data, air pipe air volume, air-conditioning room set temperature and actual temperature, set air volume Qi of variable air volume tail end VAV-box and set valve position theta of variable air volume tail end VAV-boxi；
3) Reading the set air quantity Qi of each variable air quantity terminal VAV-box and the set valve position theta of the electric air valvei(ii) a According to mathematical models of all parts of the variable air volume air-conditioning system, calculating the pressure drop of all loops of the variable air volume air-conditioning air system under the working condition, finding out the most unfavorable loop in the air system, setting the opening of an electric air valve in a variable air volume tail end VAV-box on the most unfavorable loop to be in a full-open state, calculating the pressure drop of the most unfavorable loop in all the loops at the moment, and taking the pressure drop as the pressure head of a fan;
4) the sum of the air volume and the air leakage volume required by each air-conditioning room is taken as the set total air volume of the variable air volume air-conditioning system, the pressure drop of the worst loop of the variable air volume air-conditioning system and the set total air volume of the system are brought into a mathematical model of a fan characteristic curve, the frequency required by the fan at the moment is calculated, the frequency of the fan is adjusted through a frequency converter, and the optimal control of the fan in the variable air volume air-conditioning system is realized.
2. The optimized energy-saving control method for the variable air volume air conditioning system according to claim 1 is characterized in that: the step 2) is specifically as follows:
the method comprises the steps of obtaining the running frequency and the power consumption of a fan through a fan data collector, obtaining the set temperature and the actual temperature of an air-conditioning room through an indoor wall-mounted module which is matched with and installed on the air-conditioning room through a variable air volume terminal VAV-box, obtaining the air volume passing through each variable air volume terminal VAV-box through a cross air volume sensor on the variable air volume terminal VAV-box, obtaining the set air volume of the air-conditioning room and the set valve position of a variable air volume terminal VAV-box electric air valve through calculation of a programmable controller on the variable air volume terminal VAV-box, obtaining the air speed of each part of an air system through data obtained through air speed sensors installed at each part of an air pipe, and further obtaining the air volume passing through different air pipes through calculation of different specifications of air.
3. The optimized energy-saving control method for the variable air volume air conditioning system according to claim 1 is characterized in that: the hydraulic calculation model of the variable air volume air conditioning system comprises an on-way resistance loss calculation model and a local resistance loss calculation model;
the on-way resistance loss calculation model is obtained by fitting impedance and wind speed by using data in a wind pipe on-way loss calculation table to obtain the corresponding relation between the wind speed and the impedance of wind pipes with different specifications, and the relation between the wind speed and the impedance is as follows:
S＝aV2+bV+c
in the formula: s-impedance of pipe section, Pa/m;
v is wind speed in the wind pipe, m/s;
a, b and c are coefficients determined by the shape and specification of the air duct;
the calculation formula of the local resistance loss is as follows:
in the formula: ζ -local drag coefficient;
v-air velocity in the local resistance element, m/s;
rho-air density, Kg/m3。
4. The optimized energy-saving control method for the variable air volume air conditioning system according to claim 2 is characterized in that: the specific calculation steps of the hydraulic calculation model of the variable air volume air-conditioning system are as follows:
and calculating the wind speed in each numbered pipe section as follows by using the set wind volume of the VAV-box at the tail end of the variable wind volume when the set wind volume is reached:
in the formula: v. ofi-air flow rate, m/h, in the pipe sections of different numbers;
Qbox-i-variable air volume end VAV-box air volume required for each room, m3/h；
AiCross-sectional areas of differently numbered pipe sections, m2；
And fitting the relationship between the impedance and the wind speed of the air pipes according to the flow velocity in each pipe section by using the data of the air pipes of various materials, shapes and specifications in a calculation table to obtain an impedance mathematical calculation formula of the on-way resistance of the air pipes:
Sj＝avj 2+bvj+c (j∈1～5)
in the formula: sjImpedance of pipe sections of different dimensions, kg/m7；
vj-air flow rate, m/h, in the pipe sections of different numbers;
the air conditioning air system is divided into a fixed air valve impedance part and an air duct impedance part:
Si＝Sd+Svalve
in the formula: siImpedance of differently numbered sections of pipe, kg/m7；
Svalve-air valve impedance of different specifications, kg/m7；
Sd-air duct impedance under the same numbered duct section, kg/m7；
Air pipe impedance S of same numbered pipe sectiondThe resistance of each numbered pipe section is obtained according to the method, and the pressure drop of the air pipe of each numbered pipe section under the corresponding air quantity is obtained by combining the set air quantity of the corresponding VAV-box read by the upper computer:
ΔPi＝Si×(∑Qbox-i)2
in the formula: delta PiNumbering the pipe section pressure drop values under the condition of corresponding wind speed and valve opening;
calculating the pressure drop value of each loop by combining the structural form of the actual air pipe system of the variable air volume experiment platform, comparing the pressure drop values of the loops of each room on the experiment platform, and finding out the worst loop of the variable air volume air conditioning system; and setting the opening degree of an electric air valve in a VAV-box at the tail end of the variable air volume on the most unfavorable loop to be in a full-open state, calculating the pressure drop of the most unfavorable loop in each loop at the moment, and taking the pressure drop as the pressure head of the fan to obtain a mathematical model of the air duct system in the variable air volume air-conditioning system constructed by taking the variable air volume experimental platform as a template.
5. The optimized energy-saving control method for the variable air volume air conditioning system according to claim 1 is characterized in that: when the actual temperature or the set temperature of the air-conditioning room is changed, the set valve position of the variable air volume terminal VAV-box electric air valve in the air-conditioning room and the set air volume of the air-conditioning room are correspondingly changed, and the steps 2) -4) are repeated.
6. An optimized energy-saving control device of a variable air volume air conditioning system based on a hydraulic characteristic dynamic change model is characterized by comprising an upper computer (1), a lower computer programmable controller, an expansion module (4), a fan data collector, an air speed sensor (5), a fan frequency converter (6), a variable air volume tail end VAV-box (7) and an indoor wall-mounted module (8); wherein,
the fan data acquisition unit is used for acquiring the running frequency and the power consumption of the fan;
the variable air volume tail end VAV-box (7) is matched with an indoor wall-mounted module (8) arranged in an air-conditioning room to obtain the set temperature and the actual temperature of the air-conditioning room, a cross air volume sensor on the variable air volume tail end VAV-box (7) obtains the air volume passing through each variable air volume tail end VAV-box, and a programmable controller on the variable air volume tail end VAV-box (7) calculates the set air volume of the air-conditioning room and the set valve position of a variable air volume tail end VAV-box electric air valve;
the wind speed sensors (5) are arranged at all parts of the wind pipe and used for acquiring data to obtain wind speeds of all parts of the wind system;
the lower computer programmable controller and the expansion module (4) control the fan data collector, the wind speed sensor (5), the variable air volume tail end VAV-box (7) and the indoor wall-mounted module (8) to collect related data; the lower computer programmable controller and the extension module (4) are communicated with the Ethernet switch (2) through the communication module (3) and then connected with the upper computer (1), and the upper computer (1) adjusts the frequency of the fan through controlling the fan frequency converter (6) to realize the optimal control of the fan in the variable air volume air conditioning air system.
7. The optimized energy-saving control device for the variable air volume air-conditioning air system based on the hydraulic characteristic dynamic change model as claimed in claim 6, wherein the indoor wall-hung module (8) comprises a temperature and humidity sensor.
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