Research On Characteristics Of Fluid Transmission, Distribution And Heat Transfer For Heating And Air Conditioning Pipeline System

With the constant expansion of HVAC system, the air-conditioning water system is becoming more complex, which also causes increasing energy consumption. Generally, the energy consumption of air conditioning system takes more than 30～50% of the total building power consumption. The "Design standard for energy efficiency of public buildings" issued in 2005 sets higher standards for the energy-saving design of the air conditioning system. The investigation of the air conditioning network characteristics is helpful to reduce the energy consumption. What's more, the good command of its characteristics and changing patterns can smooth network regulation and operating management.However, up to now the research on the overall characteristics of the consumer side water system is still insufficient, without adequate simulating achievements. Systematic investigating approaches towards the resistant and hydraulic changing patterns are almost absent. Thus this paper deals with the characteristics of the transmission and distribution system, which is valuable in engineering applications.In this paper, theoretical analysis, computer simulation and experiment verification are combined to conduct the research.Firstly, the characteristic equations for main components of steady fluid network are introduced and their mathematical models are constructed. Using a flowrate iteration process derived from real-value functions, detailed calculating procedures are listed under given precision ratio. Meanwhile, combined with the heat exchange and balance equations, mathematical model and coupling equations of unsteady flow and heat exchange network are built.Secondly, referring to the relevant conceptions of electric network, the conception of differential sensitivity, which means the influence on the whole network performances exerted by minor changes of certain components, are put forward, when the topological structure and pressure head remain unchanged.Thirdly, a large change sensitivity (LCS) theory is presented with the expansion of constructed real-value functions. This LCS theory, whose correctness is proved, deals with the influence on the whole network when the components parameters changes, using linear approximation methods.Fourthly, fuzzing mathematics principles are introduced, which can deal with subjective factors and fuzzy phenomenon during the parameter choosing process. Fuzzy minimum tree can be obtained if general algorithms in the graph theory are properly adjusted in an unchanged network. This achievement supplies an alternative decision making method in the optimization problem of air conditioning system, which deals with minimum resistance, shortest pipe length or lowest investing and operating cost of air conditioning system. Finally, using a ground water heat pump system, experimenting analysis and verification are conducted under various consumer side loads.Through the researches mentioned above, equations for pipe networks regulating and optimizing are obtained, which brings minimum power consumption, lowest pipe resistance, thus reaches the energy-saving goal. The investigation of water system characteristics provides theoretical basis during the network regulating and monitoring process, which is helpful in the design or reconstruction of real projects.