The Study On Characteristics Of Hydraulic Pipe Network Of The Fan-coil Water System

As the wider application of central air conditioning (AC) systems in large buildings, the energy consumption of AC systems becomes larger. The running time of AC systems is over 70% when the load is under 50% in most of the buildings while the energy consumption ratio of water pumps in an AC system is more than 20%. Therefore, the study on characteristics of hydraulic pipe network is to the benefit of pipe network designing and operation of AC system, and thus saves the energy consumption of buildings.Experiments, numerical simulation and theoretical analysis are adopted based on the AC system using 55 fan-coils. Around the operating characteristics of the pipe network of fan-coil water system, differential pressure bypass control and variable frequency pump control are analyzed and experimental researched respectively.Based on curve fitting of water pump characteristic and hydraulic principles, the hydraulic calculating program for pipe networks is established. The program computes hydraulic imbalance and shows the variation of hydraulic conditions. The main method of improving the hydraulic stability of the pipe network of fan-coil water system is proposed base on the computation results.To ensure that the components of differential pressure bypass control device can be selected properly and operate normally, the process of selecting calculation for differential pressure bypass valve is elaborated in details. By way of variable conditioning experiments, it concludes that differential pressure changes more gently and the bypass valve operating a lesser extent and effecting more sensitively.Analyses principles, characteristics and suitable occasions of several methods of variable frequency control in common use. And concludes that energy consumption of least resistance control is less and energy saving effects is better by comparing with other methods. Based on the least resistance control theory, develops simulative software for calculating pipe network of water system of AC and simulates the energy saving effects of variable frequency chilled water system. Experimental result shows that the simulation result is closed to the experimental data. When frequency of the pump is 45, 40, 35Hz(according to open degree of 70%, 60%, 45%), the corresponding actual energy conservation ratio is 14.46%, 34.2%, 50.74% . The lower the frequency is, the better the energy saving effect is. The actual power consumption is in proportion to 1.48, 1.88, 1.99 power of frequency, which proves that the actual power consumption of the pump is not fit for cubic law in variable conditions.