Temperature and humidity are two important factors that influence both indoor thermal comfort and air quality.Through varying compressor and supply fan speeds of a direct expansion(DX)air conditioning(A/C)unit,the air...Temperature and humidity are two important factors that influence both indoor thermal comfort and air quality.Through varying compressor and supply fan speeds of a direct expansion(DX)air conditioning(A/C)unit,the air temperature and humidity in the conditioned space can be regulated simultaneously.However,most existing controllers are designed to minimize the tracking errors between the system outputs with their corresponding settings as quickly as possible.The energy consumption,which is directly influenced by the compressor and supply fan speeds,is not considered in the relevant controller formulations,and thus the system may not operate with the highest possible energy efficiency.To effectively control temperature and humidity while minimizing the system energy consumption,a model predictive control(MPC)strategy was developed for a DX A/C system,and the development results are presented in this paper.A physically-based dynamic model for the DX A/C system with both sensible and latent heat transfers being considered was established and validated by experiments.To facilitate the design of MPC,the physical model was further linearized.The MPC scheme was then developed by formulating the objective function which sought to minimize the tracking errors of temperature and moisture content while saving energy consumption.Based on the results of command following and disturbance rejection tests,the proposed MPC scheme was capable of controlling temperature and humidity with adequate control accuracy and sensitivity.In comparison to linear-quadratic-Gaussian(LQG)controller,better control accuracy and lower energy consumption could be realized when using the proposed MPC strategy to simultaneously control temperature and humidity.展开更多
The purpose of this research is to reveal the exergy variation of each component in a direct-expansion solar-assisted heat pump(DX-SAHP)system.Exergy analysis of the DX-SAHP system with R134a is conducted.and the perf...The purpose of this research is to reveal the exergy variation of each component in a direct-expansion solar-assisted heat pump(DX-SAHP)system.Exergy analysis of the DX-SAHP system with R134a is conducted.and the performance evaluation is done.The proposed system is mainly composed of a bare plate solar collec-tor/evaporator,a hermetic variable-frequency rotary-type compressor,a micro-channel condenser and an electronic expansion valve.The experimental data include the exergy loss rates.irreversibility rates and exergy loss ratios of all components and the infuences of ambient temperature on these parameters.The analysis results show that the average irreversibility rate of the compressor is 204.8 W at an ambient temperature of 16℃,and 149.9 W atan ambient temperature of 27℃.The highest irreversibility rate occurs in the compression process,followed by the throttling process.the evaporation process and the condensation process.展开更多
基金supports for the Science and Technology Project of Zhejiang Province(No.LGG21F030009)the Natural Science Foundation of Zhejiang Province(No.LY20F030010)the Key R&D Projects in Zhejiang Province(No.2020C01164)are gratefully acknowledged.
文摘Temperature and humidity are two important factors that influence both indoor thermal comfort and air quality.Through varying compressor and supply fan speeds of a direct expansion(DX)air conditioning(A/C)unit,the air temperature and humidity in the conditioned space can be regulated simultaneously.However,most existing controllers are designed to minimize the tracking errors between the system outputs with their corresponding settings as quickly as possible.The energy consumption,which is directly influenced by the compressor and supply fan speeds,is not considered in the relevant controller formulations,and thus the system may not operate with the highest possible energy efficiency.To effectively control temperature and humidity while minimizing the system energy consumption,a model predictive control(MPC)strategy was developed for a DX A/C system,and the development results are presented in this paper.A physically-based dynamic model for the DX A/C system with both sensible and latent heat transfers being considered was established and validated by experiments.To facilitate the design of MPC,the physical model was further linearized.The MPC scheme was then developed by formulating the objective function which sought to minimize the tracking errors of temperature and moisture content while saving energy consumption.Based on the results of command following and disturbance rejection tests,the proposed MPC scheme was capable of controlling temperature and humidity with adequate control accuracy and sensitivity.In comparison to linear-quadratic-Gaussian(LQG)controller,better control accuracy and lower energy consumption could be realized when using the proposed MPC strategy to simultaneously control temperature and humidity.
基金the National Natural Science Foundation of China(No.51776115)the Shandong Province Graduate Student Supervisor Guidance Ability Promotion Program(No.SDYY17037)the Shandong University of Science and Technology Graduate Student Supervisor Guidance Ability Promotion Program(No.KDYC17009)。
文摘The purpose of this research is to reveal the exergy variation of each component in a direct-expansion solar-assisted heat pump(DX-SAHP)system.Exergy analysis of the DX-SAHP system with R134a is conducted.and the performance evaluation is done.The proposed system is mainly composed of a bare plate solar collec-tor/evaporator,a hermetic variable-frequency rotary-type compressor,a micro-channel condenser and an electronic expansion valve.The experimental data include the exergy loss rates.irreversibility rates and exergy loss ratios of all components and the infuences of ambient temperature on these parameters.The analysis results show that the average irreversibility rate of the compressor is 204.8 W at an ambient temperature of 16℃,and 149.9 W atan ambient temperature of 27℃.The highest irreversibility rate occurs in the compression process,followed by the throttling process.the evaporation process and the condensation process.