Study On Optimization Of Allocation For Central Air-conditioning System

The central air-conditioning system consumes high percent (about 65%) energy of building. For central air-conditioning system, besides the performance of equipment, the form of system, the main factors that can influence it energy consumption also including the chiller allocation and operational mode. The energy-saving of system is taken as the study target, Study on optimization of allocation for central air-conditioning system in the design layer.In this paper, taking an office building in Shenzhen for example, from the selecting of chiller, we analyze the energy conservation potential, and study the following four specific issues in-depth. First, for the selection of chiller, this paper uses DesT software to compute the air-conditioning's dynamic load of this building in cooling period, then according to the investigation of current chiller allocation and the characteration of this building's air-conditoning load, this paper offers three kind of chiller allocation programs which are repersentitive and technical reasonable. Comparing the annual electricity consumption and annual coefficient of performance (COP) of programs, we evaluate energy conservation pential of each program under variable operating modes and various allocation modes.Second, for the research on variable chilled water flow, the energy saving of variable-primary-flow system is dissertated. By comparing the annual electricity consumption of primary chilled water system work under constant flow and variable flow, we evaluate energy conservation potential of primary chilled water system. Third, for the research on variable cooling water flow, the energy-saving of chiller and cooling water pump during year-round was taken as the optimal target, the influences of different variable speed control strategies on energy consumption of chiller and cooling water pump were analyzed. The operation energy consumption was calculated under different control strategies and different cooling load conditions, and therefore the optimal control strategy was obtained. Fourth, the transient simulation is done with Smulink software and used for simulate electricity consumption of central air-condition system under different building load. The result of simulation and existing literature are compared. Finally, has carried on the briefly discussing the further research work later.Three conclusions are draw through the above research: First, chillers work under average load operation is more energy saving than work under by-chiller start operation. Chiller allocation with unequal allocation of capacity is more energy saving than equal allocation of capacity,Chiller allocationâ…¢with unequal allocation of capacity is more energy saving compared to Chiller allocationâ… with unequal allocation of capacity, the annual energy-saving rate is 2.74% and annual integrated coefficient of performance (COP) is 6.22. Second, primary chilled water system work under variable flow is more energy saving than work under contant flow circumstances, the annual energy-saving rate is 28.08%. Third, it is feasible to adopt the variable flow strategy of cooling water system and the corresponding energy-saving effect was significant. In addition, the control strategy of constant temperature difference with the minimum pressure difference was more energy efficient compared to constant flow control strategy, the annual energy-saving rate was 6.07%.