| The energy saving operation control of air conditioning system is of great significance to building energy saving.In the total energy consumption of air conditioning system,the proportion of energy consumption of air conditioning water system is large,which is one of the key energy saving points of air conditioning systems.In order to reduce the energy consumption of the air conditioning system,the variable frequency variable flow control method of pump has gradually become the main research direction of the air conditioning system energy saving operation regulation and control,and is widely used in practical projects.Through the study of practical projects and a large number of literatures,this paper finds that there are still the following problems to be solved urgently in the variable frequency control of water pump in air-conditioning water system.First,the control reference of the set value of the variable pressure difference of the circulating pump cannot reflect the energy supply demand of the end air-conditioning user with the most unfavorable heat supply in real time.The imbalance between the heat supply and heat demand of the end air-conditioning user has not been effectively introduced into the control process.Secondly,the universality of the concept and definition of the most unfavorable heat loop suitable for real-time control of the air-conditioning water system needs further studies.The existing identification methods of the most unfavorable heat loop still rely on the structural parameters,physical parameters and operating parameters of the air-conditioning water system,so it is not suitable for online identification application.Third,the existing method of optimal reforming of The variable pressure setting point for pump frequency conversion control is too empirical,lacks theoretical basis,and does not consider the role of the characteristics of the air conditioning water system pipe network in the optimal reforming of the variable pressure setting point.The above problems,the author of this paper,research progress both at home and abroad are analyzed in systematic review,on the basis of by introducing the fuzzy control theory,by the method of the combination of theory and experiment research,carried out the most unfavorable thermodynamic loop and air conditioning water system identification,water system pipe network model to predict online identification,variable pressure difference value restructuring and water pump frequency conversion fuzzy control theory and the experimental research work,the concrete research contents and results are as follows.First,this paper puts forward the end of the air conditioning water system branch thermal imbalance between supply and demand,and based on the concept of heat supply and demand balance of the most unfavorable thermodynamic loop,according to the heating/cooling fan coil heat transfer model,under the condition of fan-coil water system at the end of each branch is given the definition of heat supply and demand imbalance type and the solving method,puts forward the most unfavorable thermodynamic loop online to determine the basic method.Study based on the heat balance between supply and demand relations the most unfavorable thermodynamic loop can better reflect the regulation of air conditioning water system in the actual operation of the need to control the adjustment at the end of the branch,is the object of energy saving control should be immediately removed,as the most unfavorable thermodynamic loop water system energy saving control the most unfavorable hydraulic loop of the reference with the traditional control circuit has obvious advantages.Secondly,in order to meet the requirements of on-line identification and energy-saving regulation of the most unfavorable heat loop of the variable flow air conditioning water system,a test platform for the variable flow air conditioning water system with fan-coil units was designed and constructed,and the software and hardware development of the computer network monitoring system of the test system was completed.The test and debugging results show that the monitoring error of the test platform of the variable flow air conditioning water system is within±5.0%,and the room temperature at the end of the branch can be controlled within ±0.2℃,which can meet the requirements of variable flow energy saving regulation and control of the air conditioning water system.Thirdly,to give full play to the characteristics of air conditioning water system,a pipe network model of variable flow air conditioning water system is established,which is suitable for optimizing the reforming process of pump with variable pressure difference set value.The open-admittance model of electric continuous regulating valve and the mathematical model of fan coil unit and circulating pump in water system are obtained.Using the above model,the hydraulic characteristics of each end branch of the fan coil water system with two regulating mechanisms of electric on/off valve and electric continuous regulating valve are analyzed under four regulating conditions.The results show that an online identification method of the correlation matrix of the model of the fan coil air conditioning water system is presented.It can meet the on-line identification requirements of energy saving control of water system of variable flow air conditioning.After readjusting and adjusting the pressure difference between the inlet and outlet of the pump according to the most unfavorable heat loop,the imbalance between supply and demand of heat energy in the most unfavorable heat loop can be effectively improved or even eliminated.Fourth,to reduce the air conditioning water system is the most unfavorable thermodynamic loop online to determine the calculation difficulty,according to room temperature in the e-ec phase change characteristics of plane,defines the phase plane trajectory characteristic vector and the vector Angle,in room temperature was studied to characterize the air conditioning water system is the most unfavorable thermodynamic loop and phase plane trajectory characteristic vector and the vector Angle relationship,puts forward the air conditioning water system is the most unfavorable thermodynamic loop phase plane fuzzy identification method;The method of phase plane fuzzy identification of the most unfavorable heat loop is studied by using the test bed of the variable flow air conditioning water system established in this paper,and the feasibility and rationality of the method are verified.Results show that the temperature on the phase plane,a branch at the end of the real-time tracing direction vector Angle in the value,the greater the possibility of the branch to become the most unfavorable thermodynamic loop is larger;Where the state points out the phase plane in the I quadrant end branches should be the most unfavorable heat loop determination of the key branches.The imbalance degree of thermal energy supply in the end branches reflects the time variation characteristics of the most unfavorable heat loop in each end branch,and it is scientific and reasonable to take the most unfavorable heat loop with dynamic change as the control reference loop.Finally,this paper will be the most unfavorable thermodynamic loop phase plane fuzzy identification method,the air conditioning water system pipe.Pipe network model online identification method and function of the fuzzy subset reasoning,fuzzy control method is introduced into the water pump frequency conversion air conditioning water system control process,is proposed based on the most unfavorable thermodynamic loop pipe network model of the air conditioning water system variable differential pressure value fuzzy control method,study the control system architecture and implementation method of each function module theory,developed networked real-time control program,using the variable flow water system test bench,experimental study on the feasibility and energy saving effect of this method.The results show that the VPDFC-IMUTL method has excellent performance of energy saving control,such as better stability of room temperature control and more energy saving than the traditional linear variable pressure difference set value control.The pipeline network model in VPDFC-IMUTL method of air-conditioning hydraulic system and the prediction results of the pump value are accurate,so are the identification results of the phase plane’s most unfavorable heat loop,which is more suitable as the control reference information to realize the energy saving control of the pump value.This article studies to further clarify the concept of air conditioning water system the most unfavorable thermodynamic loop and in the air conditioning system energy saving control as important role to control the reference circuit,the better the optimization of air conditioning water system pressure difference value,restructuring,and further realize the fuzzy intelligent control and energy saving air conditioning water system control,has important theoretical significance and academic value.The energy saving control technology of variable frequency and variable pressure differential set point of water pump in air-conditioning hydraulic system developed in this paper has important engineering application value to solve the key technical problems needed for the operation regulation of air-conditioning hydraulic system in large public buildings. |
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