The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was u...The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.展开更多
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
Large-scale cryogenic air separation units(ASUs),which are widely used in global petrochemical and semiconductor industries,are being developed with high operating elasticity under variable working conditions.Differen...Large-scale cryogenic air separation units(ASUs),which are widely used in global petrochemical and semiconductor industries,are being developed with high operating elasticity under variable working conditions.Different from discrete processes in traditional machinery manufacturing,the ASU process is continuous and involves the compression,adsorption,cooling,condensation,liquefaction,evaporation,and distillation of multiple streams.This feature indicates that thousands of technical parameters in adsorption,heat transfer,and distillation processes are correlated and merged into a large-scale complex system.A lumped parameter model(LPM)of ASU is proposed by lumping the main factors together and simplifying the secondary ones to achieve accurate and fast performance design.On the basis of material and energy conservation laws,the piecewise-lumped parameters are extracted under variable working conditions by using LPM.Takagi–Sugeno(T–S)fuzzy interval detection is recursively utilized to determine whether the critical point is detected or not by using different thresholds.Compared with the traditional method,LPM is particularly suitable for“rough first then precise”modeling by expanding the feasible domain using fuzzy intervals.With LPM,the performance of the air compressor,molecular sieve adsorber,turbo expander,main plate-fin heat exchangers,and packing column of a 100000 Nm3 O2/h large-scale ASU is enhanced to adapt to variable working conditions.The designed value of net power consumption per unit of oxygen production(kW/(Nm3 O2))is reduced by 6.45%.展开更多
文摘The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.
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This work was funded by the National Natural Science Foundation of China(Grant Nos.51775494,51821093,and 51935009)the National Key Research and Development Project(Grant No.2018YFB1700701)Zhejiang Key Research and Development Project(Grant No.2019C01141).
文摘Large-scale cryogenic air separation units(ASUs),which are widely used in global petrochemical and semiconductor industries,are being developed with high operating elasticity under variable working conditions.Different from discrete processes in traditional machinery manufacturing,the ASU process is continuous and involves the compression,adsorption,cooling,condensation,liquefaction,evaporation,and distillation of multiple streams.This feature indicates that thousands of technical parameters in adsorption,heat transfer,and distillation processes are correlated and merged into a large-scale complex system.A lumped parameter model(LPM)of ASU is proposed by lumping the main factors together and simplifying the secondary ones to achieve accurate and fast performance design.On the basis of material and energy conservation laws,the piecewise-lumped parameters are extracted under variable working conditions by using LPM.Takagi–Sugeno(T–S)fuzzy interval detection is recursively utilized to determine whether the critical point is detected or not by using different thresholds.Compared with the traditional method,LPM is particularly suitable for“rough first then precise”modeling by expanding the feasible domain using fuzzy intervals.With LPM,the performance of the air compressor,molecular sieve adsorber,turbo expander,main plate-fin heat exchangers,and packing column of a 100000 Nm3 O2/h large-scale ASU is enhanced to adapt to variable working conditions.The designed value of net power consumption per unit of oxygen production(kW/(Nm3 O2))is reduced by 6.45%.
