The Dynamic Energy Consumption Simulation And Energy-saving Research In The Plant Of Variable Primary-flow System

The central air-conditioning system consumes high percent(about 65%)energy of building.Now the most building's air-conditioning system is the constant flow system. They can not adjust chilled-water with the actual load of air conditioning,and the pumps always run with the constant speed.But in a majority of time the air-conditioning system work with parts of load.Therefore there would be a great deal of water the pump transport energy was wasted.In recent years,as energy problem become more important,and nation require further intensify energy-saving work.As one of the most effective energy-saving measures,we begin to pay more attention to the research and application of variable primary-flow system.In this paper the basic theories and detection and control system of variable primary flow system are expatiated first,and several key problems in variable primary-flow system's design and application are proposed.The influence of variable flow rate of chilled water and cooling water on efficiency of the chiller's efficiency is analyzed,and finds it is feasible and energy efficient to let chilled-water and cooling-water through the chiller to be variable.Next the hydraulic characteristics of different control modes in variable primary-flow system are analyzed and compared, the stability of hydraulic characteristics is discussed,it is verified by an example,and the equilibrium measures of hydrothermal are proposed.There are remarkable energy-saving benefits of variable frequency control of pump,and it is deemed to be the best in VWV system.But there is consanguineous relationship between the energy-saving benefit of pump and networks' characteristics. Considering the influence of water pump efficiency,electric engine efficiency,the relations of the energy-saving benefits and the constant pressure are researched by theoretic analysis and calculation of an example.The combine of variable frequency and running number of the pumps,according to a goal flow,there are a few combined schemes,and their energy consumption is different.Using three parallel pumps,in this paper the energy consumption of various schemes of pumps is analyzed and compared,and the optimal(the lowest energy) combined scheme of pumps is educed.Its conclusion is instructional in optimizing the operational number of variable frequency pumps.In addition,combining with a project instance,in this paper a model of a building's energy consumption through DeST-c of Tsing-Hua University,and the hourly dynamic air-conditioning load of this building is simulated.According to the hourly dynamic air-conditioning load,the dynamic energy consumption of chillers with different running states is simulated.According to the optimal(the lowest energy) combined scheme of parallel pumps,the dynamic energy consumption of chilled water pumps with different control modes,and dynamic energy consumption of cooling water pumps with variable water flow and constant water flow are simulated,the total energy-saving benefit in the plant of The central air-conditioning system which variable primary-flow system is adopted is educed by compared with the energy consumption of chillers,chilled water pumps and cooling water pumps which are operated in different states.In the end,the energy-saving benefit of variable primary-flow system in different outdoors weather parameters is researched,and its conclusion is instructional in design of variable primary-flow system.