| The optimization of air-conditioning system is the key to energy saving for public build-ings. Chiller is the core component of air-conditioning system, accounted for 50% to 60% of the total system energy consumption. Therefore, it is necessary to study the optimal operation control strategy of the chiller. Optimal operation of the cooling water system is a multivaria-ble coupling complex engineering which needs considering the load characteristics, operation regulation characteristics and combinations of each device, pipe network characteristics and different operation control strategy to study it.The thermodynamic theory model of a multi-handpiece piston chiller was set up and validated by test based on the consideration of load characteristics and distribution strategy. These studies revealed that the relative error of the simulation results and measured of per-formance parameters of the chiller and outlet temperature of the cooling water is below 8.4% and 5%, respectively which verify the accuracy and reliability of the theoretical model. The operating characteristics of multi-handpiece piston chillers are analyzed based on the theoret-ical model considering the cooling load distribution strategy between the refrigerant loop and the compressor. After the optimal control strategy, the energy-saving efficiency is significant compared with the other three conventional control strategies.A mathematical model of variable-primary-flow pump cooling water system is proposed, the energy-saving efficiency of synchronous speed and asynchronous speed of the same type pumps is analyzed, and the energy saving effect of former is obtained. and the effect of changing in parameters on the chiller and cooling tower water temperature are analyzed con-sidering the energy consumption of a single multi-head piston chillers. Under different load-ing rates and operating strategies, the energy-saving efficiency of cooling water system with the different frequency of a single large pump and two small pumps with the same type is compared and analyzed. The results show that the two kinds of schemes can achieve the ideal energy-saving efficiency.The experimental studies on the combined frequencies regulation characteristics of the cooling water pump and cooling tower conversing simultaneously in the central air-conditioning cooling water system which placed in an office building were carried out, The coupling, adjusting inertia and stability regulation characteristics between the devices in the adjustment process will be analyzed. These studies revealed that the cooling water pump and cooling tower in the adjustment process are relatively stable. The outlet water temperature of cooling tower under control should not be too close to the ambient wet bulb temperature, and the time that required for adjusting the cooling water pump to the setting temperature dif-ference of some frequency is relatively fast. If the load, the cold water side and the atmos-pheric environment were fixed, It demonstrated that the condenser outlet subcooling degree barely changed while the compressor inlet superheat degree reduced when reducing the flow rate of cooling water or increasing inlet water temperature of condenser;additionally, the evaporation temperature increases with the rising of condensation temperature. The outlet water temperature of cooling tower changes little when the regulation is ongoing with the cooling tower fan’s frequency is 30 Hz ~ 50 Hz and the water flow ratio is 37%~70%. There-fore, when the cooling tower frequency transformer range is set at 30 Hz ~ 50 Hz, changing the fan speed will bring a certain energy-saving effect. At the same time, some experimental studies on the optimization of energy-saving control of cooling water system at different sea-sons were carried out based on the cooling load characteristics of the building. The advantage of combined frequency control strategy in the control of the cooling water pump and tower fans is analyzed and verified. |
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