Optimization Analysis Of Energy Consumption Of Water Source Heat Pump System Under Variable Condition

With the improvement of living quality requirements,heating and air-conditioning energy consumption grows gradually every year. It not only consumed a large amount of energy, meanwhile it brings great pressure to the environment. Heat pump is a kind of technology which can provide heating and air-conditioning function by using low grade energy. So it has apparent economic and environment profit. However the current heat pump systems possess some defects such as unreasonable design and high water pump operating energy consumption so that it cannot be regarded as an environment protection and energy saving system. In order to reduce water system transportation energy consumption a method which aims at minimizing energy consumption as an optimization goal was proposed, so that it will provide guidance for the design and operation of system.The changing tendency of performance parameters of water pumps along with water flow rate in parallel condition was analyzed. The fitted equations between performance parameters and water flow rate was obtained by fitting tool 1stopt. The water pump energy consumption in different working conditions was programmed by MATLAB. One kind of water pump energy consumption in different working conditions was calculated.With the constant speed pump energy consumption as a benchmark, when the flow rate is140m3/h, three parallel water pumps in variable speed simultaneously could save 21%energy consumption, as well two in variable speed and one in constant speed 19%. When the flow rate is 95m3/h, two water pumps in variable speed simultaneously could save50% energy consumption, as well one in variable speed and one in constant speed save42%. The results were showed that keeping water pump in variable speed simultaneously was the most energy-saving consumption operation mode.Taking screw type water heat pump unit as research object the mathematical models of four major components of the unit were established. Owe to the use of REFPROP software the physical parameters of refrigerant was simplified. The COP changing tendency under variable cooling water flow rate, variable chilled water flow rate, variable cooling water inlet temperature, variable chilled water outlet temperature conditions in the basic of theoretical compression refrigeration cycle was simulated. The results were as follows:(1)the maximum influence ratio of cooling water and chilled water were12.43% and 6.7% respectively. It can be concluded that variable cooling water flow rate had a bigger influence on COP; 2. Cooling water inlet temperature ascended per 1℃,COP decreased by about 4.5%~7%, chilled water outlet temperature decreased per 1℃,COP decreased 3.2%~5.8%.The water source heat pump system was classified briefly. The composition of water system transportation energy consumption(refrigerant circulation system, chilled watercirculation system, cooling circulation system) was introduced. The water system transportation energy consumption mathematical model was established. The total transportation energy consumption of direct system was optimized. Taking a practical project as an example the total transportation energy consumption in different conditions was calculated. The results showed that: When load rate ranged from 0.5 to 1, adopting three water pumps in variable speed simultaneously could save the most energy consumption in an average 6.5% compared with three pumps in constant speed. When load rate ranged from 0.2 to 0.5, adopting two water pumps in variable speed simultaneously could save the most energy consumption in an average 13.4% compared with three pumps in constant speed. Furthermore the lower the load rate was, the smaller the energy saving ratio was. For example when load rate were 0.5 and 0.2 respectively,the energy saving ratio were 12.4% and 23.4%.