Study On Variable Pressure Control For VWV Chilled Water Systems

The energy consumption of air conditioning system has a lagrge proportion of thebuildings’ energy consumption. As a mainly department of air conditioning system’senergy consumption,70%of the entire system’s energy consumption is occupied bythe water system. Study on energy-saving of the air-conditioning water system hassignificance for Energy saving and Emission reduction.In variable water volume system of HVAC, the secondary pump makes thevolume of chilled water meeting the need of the user by changing the pump’s motorfrequency. Except for saveing transport energy consumption, the system maintain aconstant temperature difference between the chilled supply water and return water. Asa result, the COP of the chiller runs at a high efficiency. But how to control thesecondary pump under the variable frequency operation has become a difficultproblem.In this paper, the differential pressure of both ends of the user who is the most faraway is taked as the secondary pump control signals. Firstly, the load of buildingsthroughout the cooling season is simulated. By zoning the air-conditioning load,variale control setting values of the differential pressure for each load partition iscalculated. Afterthen, takeing the TRNSYS simulation as platform, the energyconsumption of the secondary pumps and chillers are calculated throughout thecooling season.According to the result of the the energy consumption of the secondary pumpsand chillers,6.49%of the secondary pump energy consumption is saved. At the sametime,5.10%of the chiller’s energy consumption is saved too. The calculated resultshows that, comparing with the fixed-pressure control strategy, variable pressurecontrol strategy is practical and has better energy-saving effect.