Absorption/desorption properties of some humidity controlling materials which contain gypsum as basic cement materials and activated Sepiolite powder as humidity controlling media were tested. The kinetics curve of mo...Absorption/desorption properties of some humidity controlling materials which contain gypsum as basic cement materials and activated Sepiolite powder as humidity controlling media were tested. The kinetics curve of moisture adsorption/desorption were drawn and humidity controlling performance in nature environment was verified. The experimental results show that moisture absorption/desorption rates are increased, and the speed is also accelerated. These materials, which can adjust environmental humidity effectively, are new ones with good humidity controlling performance.展开更多
Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based compos...Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.展开更多
Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum ...Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.展开更多
Phase change material(PCM)can reduce the indoor temperature fluctuation and humidity control material can adjust relative humidity used in buildings.In this study,a kind of composite phase change material particles(CP...Phase change material(PCM)can reduce the indoor temperature fluctuation and humidity control material can adjust relative humidity used in buildings.In this study,a kind of composite phase change material particles(CPCMPs)were prepared by vacuum impregnation method with expanded perlite(EP)as supporting material and paraffin as phase change material.Thus,a PCM plate was fabricated by mould pressing method with CPCMPs and then composite phase change humidity control wallboard(CPCHCW)was prepared by spraying the diatom mud on the surface of PCM plate.The composition,thermophysical properties and microstructure were characterized using X-ray diffraction instrument(XRD),differential scanning calorimeter(DSC)and scanning electron microscope(SEM).Additionally,the hygrothermal performance of CPCHCW was characterized by temperature and humidity collaborative test.The results can be summarized as follows:(1)CPCMPs have suitable phase change parameters with melting/freezing point of 18.23°C/29.42°C and higher latent heat of 54.66 J/g/55.63 J/g;(2)the diatom mud can control the humidity of confined space with a certain volume;(3)the combination of diatom mud and PCM plate in CPCHCW can effectively adjust the indoor temperature and humidity.The above conclusions indicate the potential of CPCHCW in the application of building energy efficiency.展开更多
PEM （Proton Exchange Membrane） fuel cell is a promising renewable energy source to a wide range of applications for its clean products and high power density. However, controlling its humidity is a challenging probl...PEM （Proton Exchange Membrane） fuel cell is a promising renewable energy source to a wide range of applications for its clean products and high power density. However, controlling its humidity is a challenging problem due to the interdependence of several phenomena contributing in membrane＇s water content. This work deals with efficiency improvement of PEM fuel cells via humidity control. An innovative strategy of control based on the model of Ref. [1] is proposed. It consists on regulating gas humidification rates according to the power demand so that to minimize power losses. The proposed control takes into consideration constraints related to humidification in order to avoid dry out or flooding of the membrane. Simulations results show that time-phasing between hydrogen and oxygen humidification rates plays an important role in minimizing power losses. The proposed control shows significant improvement in the fuel cell＇s efficiency up to 20%.展开更多
It is not easy to control humidity in a geomagnetic room. If humidity is too high or the change is too fast it will lead to an abnormal change on data. The intelligent real-time humidity analysis and monitoring system...It is not easy to control humidity in a geomagnetic room. If humidity is too high or the change is too fast it will lead to an abnormal change on data. The intelligent real-time humidity analysis and monitoring system of a geomagnetic room and probe can not only monitor and display the change of humidity in the geomagnetic room and send an alarm signal when it exceeds the pre-set range, but also dehumidify intelligently. One can arbitrarily control the sensor to monitor the ambient humidity of the probe in order to ensure that the data is stable and true. The design idea and main functions of the system are introduced in the paper.展开更多
Autonomous indoor humidity control is gaining more and more attention but is limited by the trade-offs among pore volume,pore size and water stability of water adsorbents.We solve this problem by using a unique coordi...Autonomous indoor humidity control is gaining more and more attention but is limited by the trade-offs among pore volume,pore size and water stability of water adsorbents.We solve this problem by using a unique coordination network topology combined with hydrolytically stable M(Ⅲ)carboxylate clusters.By extending the ligand length from 9.0 to 11.2 and 13.7?,the pore volume significantly increases from 0.99 to 1.40 and 1.78 cm^(3)g^(-1),which proportionally increases the saturated water adsorption capacity.Meanwhile,the pore size slightly increases from 10.4 to 11.0 and 13.5A,which restricts the isotherm inflection pressure and hysteresis width to meet the requirement of indoor humidity control.Large single-crystals suitable for Xray diffraction studies were obtained by using Fe(Ⅲ)salts,while isostructural frameworks with sufficiently high water stabilities were synthesized by using Cr(Ⅲ)salts,which offer record working capacity of 0.90 and 1.10 g g^(-1)for indoor humidity control.展开更多
Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which inte...Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.This work establishes a novel coefficient of performance(COP)model of VMD-ACERS.The main parameters affecting the COP of conventional fan coil unit cooling system(FCUCS)and VMD-ACERS are investigated.The performance of FCUCS and VMD-ACERS are compared,and the energy-saving potential of VMD-ACERS is proved.Results indicate that,for FCUCS,the importance ranking of parameters is basically stable.However,for VMD-ACERS,the importance ranking will be affected by FCU and refrigerant.The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure.On the contrary,superheating,subcooling are relatively less important parameters.For VMD-ACERS,it is not necessary to pursue the membrane with very high selectivity,because the selectivity of membrane would also be a less important parameter when it reaches 500.The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 k Pa.The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC,and can extend the application of THIC air-conditioning system.展开更多
Variable air volume(VAV)air-conditioning(AC)systems are widely employed to achieve a comfortable room thermal and humid environment depending on its better regulation performance and energy efficiency.In the single co...Variable air volume(VAV)air-conditioning(AC)systems are widely employed to achieve a comfortable room thermal and humid environment depending on its better regulation performance and energy efficiency.In the single coil VAV AC system,conventional proportional-integral(PI)control algorithm is usually adopted to track the set-points of the room temperature and humidity by regulating the supply air flow rate and the chilled water flow rate,respectively.However,the control performance is usually not good due to the high coupling of the heat and mass transfer in the air-handling unit(AHU).A model-based control method is developed to realize the decoupling control of the room temperature and humidity according to the bilinear characteristics of the temperature and humidity variation.In this control method,a bilinear room temperature controller is used to track the room temperature set-point based on the real-time cooling load,while a room humidity controller is used to track the room humidity set-point depending on the real-time humidity load.The control performance was validated in a simulated VAV AC system.The test results show that comparing with the conventional PI control,the room temperature and humidity are controlled much more robustly and accurately by using the proposed model-based control method.展开更多
Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for...Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices was observed by increasing the relative humidity in the range of 0-95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increasing the relative humidity, the oscillator＇s frequencies were also increased in the range of 4.2-12.0 kHz for 65μm thick film sample, 4.1-9.0 kHz for 88μm thick film sample, and 4.2-9.0 kHz for 210μm sample. Effects of film thickness on the oscillator＇s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.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
A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences （C...A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences （CAMS） in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station （SDZ） outside Beijing during winter, from December 2005 to January 2006. Measurements were carded out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function （or factor） of the aerosol scattering coefficientf（RH） increased continuously with increasing relative humidity （RH） and showed no obvious ＂step-like＂ deliquescent behavior at both sites during the experiment. The average growth factorf（RH） at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f（RH = 80 ± 1%）, was found to be about 1.26 ±0.15 at CAMS and 1.24 ±0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.展开更多
Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas,and it is difficult to achieve simultaneous control of temperature and humidity.A combined absorption refrigeratio...Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas,and it is difficult to achieve simultaneous control of temperature and humidity.A combined absorption refrigeration(AR)and liquid desiccant dehumidification(LDD)air-conditioning system based on cascade utilization of low-grade heat source is proposed.The system can realize independent control of temperature and humidity and carry out profound recovery of low-grade heat sources.Under the design conditions,the heat utilization rate C reaches 21.05%,which is 2.73 times that of the conventional absorption refrigeration reference system.A parametric sensitivity analysis is performed to optimize the system.The C increases from 9.79%to 18.55%and the coefficient of performance C O P t increases from 0.33 to 0.35 with an increase in chilled water temperature from 7°C to 15°C.With an increase in regenerant solution temperature from 60°C to 70°C,the C achieves the optimal value of 21.05%at 68°C.C decreases from 21.05%to 15.05%as the concentration of the regenerant solution increases from 36%to 40%.Under variable environmental temperature and humidity,the C the proposed system changes within a small range and stays much higher than that of the reference system with the same quality heat source,which indicates that the proposed system has a better adaptability to changing environmental parameters.展开更多
The liquid desiccant air-conditioning system is considered as an energy-efficient alternative to the vapor compression system.The dynamic response characteristics of the system under variable cooling load play an impo...The liquid desiccant air-conditioning system is considered as an energy-efficient alternative to the vapor compression system.The dynamic response characteristics of the system under variable cooling load play an important role in the air temperature and humidity control performance of the system.However,the dynamic response characteristics have not been fully revealed in previous studies.Thus,a dynamic model for a heat pump driven liquid desiccant air-conditioning(HPLDAC)system is established to investigate the dynamic response characteristics of the system in this study.Subsequently,experiments were conducted to validate the accuracy of the dynamic model.The simulation results show a good agreement with the experimental data.The simulation results reveal that evaporating water from the solution is a time-consuming process,compared to adding water to the solution.It spends a long time for the HPLDAC system to decrease the high relative humidity of supply air to a low value,which limits the air temperature and humidity control performance of the system.The upper band for the water replenishing value opening(△φup)is a crucial parameter to improve the limitation.When△φup decreases from 1.0%产to 0.25%,the time consumed to reduce the supply air relative humidity to the new lower set value can be saved by 30.6%.展开更多
文摘Absorption/desorption properties of some humidity controlling materials which contain gypsum as basic cement materials and activated Sepiolite powder as humidity controlling media were tested. The kinetics curve of moisture adsorption/desorption were drawn and humidity controlling performance in nature environment was verified. The experimental results show that moisture absorption/desorption rates are increased, and the speed is also accelerated. These materials, which can adjust environmental humidity effectively, are new ones with good humidity controlling performance.
基金Funded by the National Natural Science Foundation of China(No.51678254)。
文摘Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.
基金financially supported by the National Natural Science Foundation of China(51172176)
文摘Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.
基金Project(51408184)supported by the National Natural Science Foundation of ChinaProject(E2017202136)supported by the Natural Science Foundation of Hebei Province,China+1 种基金Project(BSBE2017-05)supported by the Opening Funds of State Key Laboratory of Building Safety and Built Environment and National Engineering Research Center of Building Technology,ChinaProject(QG2018-3)supported by Hebei Provincial Department of Transportation,China
文摘Phase change material(PCM)can reduce the indoor temperature fluctuation and humidity control material can adjust relative humidity used in buildings.In this study,a kind of composite phase change material particles(CPCMPs)were prepared by vacuum impregnation method with expanded perlite(EP)as supporting material and paraffin as phase change material.Thus,a PCM plate was fabricated by mould pressing method with CPCMPs and then composite phase change humidity control wallboard(CPCHCW)was prepared by spraying the diatom mud on the surface of PCM plate.The composition,thermophysical properties and microstructure were characterized using X-ray diffraction instrument(XRD),differential scanning calorimeter(DSC)and scanning electron microscope(SEM).Additionally,the hygrothermal performance of CPCHCW was characterized by temperature and humidity collaborative test.The results can be summarized as follows:(1)CPCMPs have suitable phase change parameters with melting/freezing point of 18.23°C/29.42°C and higher latent heat of 54.66 J/g/55.63 J/g;(2)the diatom mud can control the humidity of confined space with a certain volume;(3)the combination of diatom mud and PCM plate in CPCHCW can effectively adjust the indoor temperature and humidity.The above conclusions indicate the potential of CPCHCW in the application of building energy efficiency.
文摘PEM （Proton Exchange Membrane） fuel cell is a promising renewable energy source to a wide range of applications for its clean products and high power density. However, controlling its humidity is a challenging problem due to the interdependence of several phenomena contributing in membrane＇s water content. This work deals with efficiency improvement of PEM fuel cells via humidity control. An innovative strategy of control based on the model of Ref. [1] is proposed. It consists on regulating gas humidification rates according to the power demand so that to minimize power losses. The proposed control takes into consideration constraints related to humidification in order to avoid dry out or flooding of the membrane. Simulations results show that time-phasing between hydrogen and oxygen humidification rates plays an important role in minimizing power losses. The proposed control shows significant improvement in the fuel cell＇s efficiency up to 20%.
基金sponsored by the Scientific Research Foundation of Earthquake Administration of Henan Province
文摘It is not easy to control humidity in a geomagnetic room. If humidity is too high or the change is too fast it will lead to an abnormal change on data. The intelligent real-time humidity analysis and monitoring system of a geomagnetic room and probe can not only monitor and display the change of humidity in the geomagnetic room and send an alarm signal when it exceeds the pre-set range, but also dehumidify intelligently. One can arbitrarily control the sensor to monitor the ambient humidity of the probe in order to ensure that the data is stable and true. The design idea and main functions of the system are introduced in the paper.
基金supported by the National Natural Science Foundation of China(22090061,22231012,21821003,22071272)。
文摘Autonomous indoor humidity control is gaining more and more attention but is limited by the trade-offs among pore volume,pore size and water stability of water adsorbents.We solve this problem by using a unique coordination network topology combined with hydrolytically stable M(Ⅲ)carboxylate clusters.By extending the ligand length from 9.0 to 11.2 and 13.7?,the pore volume significantly increases from 0.99 to 1.40 and 1.78 cm^(3)g^(-1),which proportionally increases the saturated water adsorption capacity.Meanwhile,the pore size slightly increases from 10.4 to 11.0 and 13.5A,which restricts the isotherm inflection pressure and hysteresis width to meet the requirement of indoor humidity control.Large single-crystals suitable for Xray diffraction studies were obtained by using Fe(Ⅲ)salts,while isostructural frameworks with sufficiently high water stabilities were synthesized by using Cr(Ⅲ)salts,which offer record working capacity of 0.90 and 1.10 g g^(-1)for indoor humidity control.
基金The National Key Technology Support Program(2015BAJ03B01)the Hunan Provincial Innovation Foundation for Postgraduate Studies(CX20190287)。
文摘Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.This work establishes a novel coefficient of performance(COP)model of VMD-ACERS.The main parameters affecting the COP of conventional fan coil unit cooling system(FCUCS)and VMD-ACERS are investigated.The performance of FCUCS and VMD-ACERS are compared,and the energy-saving potential of VMD-ACERS is proved.Results indicate that,for FCUCS,the importance ranking of parameters is basically stable.However,for VMD-ACERS,the importance ranking will be affected by FCU and refrigerant.The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure.On the contrary,superheating,subcooling are relatively less important parameters.For VMD-ACERS,it is not necessary to pursue the membrane with very high selectivity,because the selectivity of membrane would also be a less important parameter when it reaches 500.The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 k Pa.The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC,and can extend the application of THIC air-conditioning system.
基金This work presented in this paper is financially supported by a grant(No.51678263)of National Science Foundation of China.
文摘Variable air volume(VAV)air-conditioning(AC)systems are widely employed to achieve a comfortable room thermal and humid environment depending on its better regulation performance and energy efficiency.In the single coil VAV AC system,conventional proportional-integral(PI)control algorithm is usually adopted to track the set-points of the room temperature and humidity by regulating the supply air flow rate and the chilled water flow rate,respectively.However,the control performance is usually not good due to the high coupling of the heat and mass transfer in the air-handling unit(AHU).A model-based control method is developed to realize the decoupling control of the room temperature and humidity according to the bilinear characteristics of the temperature and humidity variation.In this control method,a bilinear room temperature controller is used to track the room temperature set-point based on the real-time cooling load,while a room humidity controller is used to track the room humidity set-point depending on the real-time humidity load.The control performance was validated in a simulated VAV AC system.The test results show that comparing with the conventional PI control,the room temperature and humidity are controlled much more robustly and accurately by using the proposed model-based control method.
基金GIK Institute of Engineering Sciences and Technology for the support extended to this work
文摘Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices was observed by increasing the relative humidity in the range of 0-95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increasing the relative humidity, the oscillator＇s frequencies were also increased in the range of 4.2-12.0 kHz for 65μm thick film sample, 4.1-9.0 kHz for 88μm thick film sample, and 4.2-9.0 kHz for 210μm sample. Effects of film thickness on the oscillator＇s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.
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supported by projects from NSFC (40675009)National Key Basic Research project (2006CB403701)+1 种基金Climate Change Research Foundation of CMA (CCSF2005-3-DH03)partly supported by China MOST project(2001DIA10009).
文摘A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences （CAMS） in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station （SDZ） outside Beijing during winter, from December 2005 to January 2006. Measurements were carded out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function （or factor） of the aerosol scattering coefficientf（RH） increased continuously with increasing relative humidity （RH） and showed no obvious ＂step-like＂ deliquescent behavior at both sites during the experiment. The average growth factorf（RH） at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f（RH = 80 ± 1%）, was found to be about 1.26 ±0.15 at CAMS and 1.24 ±0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.
基金The authors express gratitude for the support of the National Key Research and Development Program of China(No.2018YFB0905103)the National Natural Science Foundation of China(No.51806213)Beijing Key Laboratory of Distributed Combined Cooling Heating and Power System.
文摘Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas,and it is difficult to achieve simultaneous control of temperature and humidity.A combined absorption refrigeration(AR)and liquid desiccant dehumidification(LDD)air-conditioning system based on cascade utilization of low-grade heat source is proposed.The system can realize independent control of temperature and humidity and carry out profound recovery of low-grade heat sources.Under the design conditions,the heat utilization rate C reaches 21.05%,which is 2.73 times that of the conventional absorption refrigeration reference system.A parametric sensitivity analysis is performed to optimize the system.The C increases from 9.79%to 18.55%and the coefficient of performance C O P t increases from 0.33 to 0.35 with an increase in chilled water temperature from 7°C to 15°C.With an increase in regenerant solution temperature from 60°C to 70°C,the C achieves the optimal value of 21.05%at 68°C.C decreases from 21.05%to 15.05%as the concentration of the regenerant solution increases from 36%to 40%.Under variable environmental temperature and humidity,the C the proposed system changes within a small range and stays much higher than that of the reference system with the same quality heat source,which indicates that the proposed system has a better adaptability to changing environmental parameters.
基金This research was supported by the National Key Research Program of China(No.2018YFC0705202)National Natural Science Foundation of China(No.51638010).
文摘The liquid desiccant air-conditioning system is considered as an energy-efficient alternative to the vapor compression system.The dynamic response characteristics of the system under variable cooling load play an important role in the air temperature and humidity control performance of the system.However,the dynamic response characteristics have not been fully revealed in previous studies.Thus,a dynamic model for a heat pump driven liquid desiccant air-conditioning(HPLDAC)system is established to investigate the dynamic response characteristics of the system in this study.Subsequently,experiments were conducted to validate the accuracy of the dynamic model.The simulation results show a good agreement with the experimental data.The simulation results reveal that evaporating water from the solution is a time-consuming process,compared to adding water to the solution.It spends a long time for the HPLDAC system to decrease the high relative humidity of supply air to a low value,which limits the air temperature and humidity control performance of the system.The upper band for the water replenishing value opening(△φup)is a crucial parameter to improve the limitation.When△φup decreases from 1.0%产to 0.25%,the time consumed to reduce the supply air relative humidity to the new lower set value can be saved by 30.6%.
