Thermoelectric air conditioning systems based on the Peltier effect had two modes:heating and cooling.In this work,the proposed design provides continuous improvement in COP from the first minute of operation.In cooli...Thermoelectric air conditioning systems based on the Peltier effect had two modes:heating and cooling.In this work,the proposed design provides continuous improvement in COP from the first minute of operation.In cooling mode,the coefficient of performance(COP)was 1.176 due to the techniques used in this device,and it increased to 1.24 in the last minute of operation.Concerning the steady-state scenario,from the first minute,the Qc was larger than the W for the entire duration of the operation.The output temperature reaches 18.97℃ ,and the temperature on the cold side reaches 4.96℃ in the fifteen minutes of operation.The cooling mood was checked in Iraq/Baghdad in October with a temperature of 31℃ .Furthermore,the heating mode was checked in December with a temperature of 22℃ .Due to the size of the component on the cold side being small compared with the size of the component on the heat side,it reached a steady state in 13 min.This means the COP in heating mode reached 1.01 in 14 min.Furthermore,due to the presence of a thermal insulator made inside the device to separate the cold side and the hot side,the difference in temperature causes a noticeable little ascent.This is why the COP increased because it kept the degree differences low.Performance enhancements were achieved by optimizing the behavior of thermoelectric materials.The device contains 3 Peltier elements,a water-cooled system with one Peltier,a heat sink,and a fan.The design of the dehumidification system addresses the humidity issue commonly associated with thermoelectric air conditioners.In this context,the results indicate that the humidity rates had decreased and the cooling rate had increased with these innovative techniques,and thus,excellent performance can be achieved even if the Seebeck coefficient is not at its highest based on the condition of providing the Peltier elements’reliability and optimal thermal performance for various applications requiring both cooling and heating functions.The insulation plays a critical role in maintaining the efficiency of the system,reducing energy consumption,and ensuring long-term functionality.The proposed system is valuable for devices or environments that demand precise and dual thermal control with minimal energy wastage.展开更多
LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals...LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals,nursing homes,and food factories,where humidity control is required.However,LiCl(lithium chloride),a conventional humidity control liquid,is highly corrosive to metals,requiring the use of highly corrosion-resistant materials for the pipes and the heat exchangers.These lead to the problem that the manufacturing cost of the air conditioner increases.Therefore,we developed an inexpensive and compact LDAC by adopting a novel IL(ionic liquid)that does not corrode the metals commonly used in air conditioners.In this study,we evaluated the metal solubilities and sterilizing properties of the IL.Based on the physical properties of the IL,the humidity control module was improved for the purpose of downsizing and cost reduction of the unit.Moreover,we conducted a performance evaluation of the LDAC in the environmental test room under the condition in which temperature and humidity change rapidly in short period of time to simulate the condition of sudden showers of rain in summer.Test results showed that processed air was supplied at very stable level.展开更多
As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy ...As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy consumption,how to improve the energy efficiency ratio of air conditioning systems and reduce energy consumption has become an important issue in research and practice.The purpose of this paper is to discuss the impact of humidity control strategies on energy saving in centralized central air conditioning systems,with a view to providing a theoretical basis and practical guidance for realizing building energy efficiency.展开更多
The central air conditioning system in an intelligent building (IB) was analyzed and modeled in order to perform the optimization scheduling strategy of the central air conditioning system. A set of models proposed ...The central air conditioning system in an intelligent building (IB) was analyzed and modeled in order to perform the optimization scheduling strategy of the central air conditioning system. A set of models proposed and a type of periodically autoregressive model (PAR) based on the improved genetic algorithms (IGA) were used to perform the optimum energy saving scheduling. The example of the Liangmahe Plaza was taken to show the effectiveness of the methods.展开更多
This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilizat...This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.展开更多
An optimum energy saving scheduling strategy of the central air conditioning system in an intelligent building (IB) was proposed. Based on the system analysis a set of models of the central air conditioning system w...An optimum energy saving scheduling strategy of the central air conditioning system in an intelligent building (IB) was proposed. Based on the system analysis a set of models of the central air conditioning system was established. The periodically autoregressive models (PARM) based on genetic algorithms (GA) were used to predict the next day’s cold load. The improved genetic algorithms (IGA) with stochastic real number coding were used to finish the optimum energy saving scheduling of the system. The simulation results for the building of the Liangmahe Plaza show that the proposed strategy can save energy up to about 24 5%.展开更多
The vast potential of system health monitoring and condition based maintenance on modern commercial aircraft is being realized through the innovative use of Airplane Condition Monitoring System(ACMS) data.However ther...The vast potential of system health monitoring and condition based maintenance on modern commercial aircraft is being realized through the innovative use of Airplane Condition Monitoring System(ACMS) data.However there are few methods addressing the issues of failure prognostics and predictive maintenance for commercial aircraft Air Conditioning System(ACS).This study developed a Bayesian failure prognostics approach using ACMS data for predictive maintenance of ACS.First, a health index characterizing the ACS health state is inferred from a multiple sensor signals using a data driven method.Then a dynamic linear model is proposed to describe the degradation process for failure prognostics.Bayesian inference formulas are carried out for degradation estimation and prediction.The developed approach is applied on a passenger aircraft fleet with ACMS data recorded for one year.The analysis of the case study shows that the developed method can produce satisfactory prognostics results, where all the ACS failure precursors are identified in advance, and the relative errors for the failure time prediction made when just entering the degradation warning stage are less than 8%.This would allow operators to proactively plan future maintenance.展开更多
In this paper,based on the generalized heat transfer law,an air conditioning system is analyzed with the entropy generation minimization and the entransy theory.Taking the coefficient of performance（denoted as COP） ...In this paper,based on the generalized heat transfer law,an air conditioning system is analyzed with the entropy generation minimization and the entransy theory.Taking the coefficient of performance（denoted as COP） and heat flow rate Qout which is released into the room as the optimization objectives,we discuss the applicabilities of the entropy generation minimization and entransy theory to the optimizations.Five numerical cases are presented.Combining the numerical results and theoretical analyses,we can conclude that the optimization applicabilities of the two theories are conditional.If Qout is the optimization objective,larger entransy increase rate always leads to larger Qout,while smaller entropy generation rate does not.If we take COP as the optimization objective,neither the entropy generation minimization nor the concept of entransy increase is always applicable.Furthermore,we find that the concept of entransy dissipation is not applicable for the discussed cases.展开更多
Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent stud...Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent studies, R1234 yf is considered as one of the top candidates to replace R134 a. In this article, the performances of R1234 yf "drop-in" system and the optimization to the R1234 yf system are experimentally studied and investigated.The expansion valve used for the R1234 yf system is optimized by changing the charged fluid and adjusting the spring force. The results indicate that it can improve the performance of R1234 yf system significantly through adjusting the thermostatic expansion valve. For the thermostatic expansion valves(TEVs) charged with R134 a in thermal bulb, the system performance is optimal. Compared to the original expansion valve, for the R1234 yf system applying the adjusted expansion valves, under different working conditions the cooling capacity increases by 11.3% averagely and the coefficient of performance(COP) increases by 8% averagely.展开更多
An aircraft cabin is a narrow,closed-space environment.To keep the air quality in cabin healthy for passengers,especially during an epidemic such as SARS-CoV-2(or 2019-nCoV)in 2020,a novel aircraft air conditioning sy...An aircraft cabin is a narrow,closed-space environment.To keep the air quality in cabin healthy for passengers,especially during an epidemic such as SARS-CoV-2(or 2019-nCoV)in 2020,a novel aircraft air conditioning system,called the ultra-high-temperature instantaneous sterilization air conditioning system(UHTACS),is proposed.Based on the proposed system,a simulation of the UHT-ACS is analysed in various flight states.In the UHT-ACS,the mixing air temperature of return and bleed air can reach temperature up to 148.8°C,which is high enough to kill bacilli and viruses in 2一8 s.The supply air temperature of the UHT-ACS in a mixing cavity is about 12 C in cooling mode both on the ground and in the air.The supply air temperature is about 42 C in heating mode.Compared with the air conditioning systems(ACS)of traditional aircraft the supply air temperatures of the UHT-ACS in the mixing cavity are in good agreement with those of a traditional ACS with 60%fresh air and 40%return air.Furthermore the air temperature at the turbine outlet of the UHT-ACS is higher than that of a traditional ACS which will help to reduce the risk of icing at the outlet.Therefore the UHT-ACS can operate normally in various flight states.展开更多
Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing i...Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing interest from the stand point of reducing energy consumption during dehumidification. In order to find the appropriate ionic liquids(ILs) as a desiccant for the liquid desiccant air-conditioner system, we conducted a systematic evaluation of the humidification capability of 16 types of ILs. Among the tested ILs, tributyl(methyl)phosphonium dimethyl phosphate([P4441][DMPO_4]) exhibited the best dehumidification capacity and had a less corrosive effect on four types of metals as possible piping materials. It should be noted that this [P_(4441)][DMPO_4] has a very stable nature and produced no odor while conducting the experiment and storing for over 1 year at room temperature under ambient conditions. Furthermore, it was revealed that a 77%(w/w) aqueous solution of [P4441][DMPO_4] worked as an efficient desiccant liquid for the liquid desiccant air-conditioner system.展开更多
As an environmentally harmless and feasible alternate refrigerant, CO 2 has attracted worldwide attention, especially in the area of automobile air conditioning (AAC). The thermal property of CO 2 and its trans cr...As an environmentally harmless and feasible alternate refrigerant, CO 2 has attracted worldwide attention, especially in the area of automobile air conditioning (AAC). The thermal property of CO 2 and its trans critical refrigeration cycle is very different from that of the traditional CFC or HCFC system. The detailed process of CO 2 system thermal cycle design and optimization is described in this paper. System prototype and performance test bench were developed to analyze the performance of the CO 2 AAC system.展开更多
Screening similar historical fault-free candidate data would greatly affect the effectiveness of fault detection results based on principal component analysis(PCA).In order to find out the candidate data,this study co...Screening similar historical fault-free candidate data would greatly affect the effectiveness of fault detection results based on principal component analysis(PCA).In order to find out the candidate data,this study compares unweighted and weighted similarity factors(SFs),which measure the similarity of the principal component subspace corresponding to the first k main components of two datasets.The fault detection employs the principal component subspace corresponding to the current measured data and the historical fault-free data.From the historical fault-free database,the load parameters are employed to locate the candidate data similar to the current operating data.Fault detection method for air conditioning systems is based on principal component.The results show that the weighted principal component SF can improve the effects of the fault-free detection and the fault detection.Compared with the unweighted SF,the average fault-free detection rate of the weighted SF is 17.33%higher than that of the unweighted,and the average fault detection rate is 7.51%higher than unweighted.展开更多
Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeli...Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeling is given for AC energy-saving control and effectiveness optimization is made. To facilitate the implement of the control and energy saving, priorities have been assigned to the major control steps based on logical reasoning. Forward-looking tree modeling based on FDES has been simplified to help further optimization, and a simple and concrete example has been put forward illustrating energy-saving control in AC system.展开更多
According to the requirements of welding process for vortex type compressor of air conditioner manufactured in product line, a special girth welding machine with PLC as control core was developed, which had both uprig...According to the requirements of welding process for vortex type compressor of air conditioner manufactured in product line, a special girth welding machine with PLC as control core was developed, which had both upright and 45 ° incline service positions. And some key technologies were researched, such as structural design of machine body, reliable conduction of rotary weldments and quality control of welding process and so on. The experimental results showed that this machine could satisfy the requirements of welding quality and girth welding technology, results also proved the machine was a high-effwiency and low-cost automatic welding device.展开更多
Principal component analysis(PCA)has been already employed for fault detection of air conditioning systems.The sliding window,which is composed of some parameters satisfying with thermal load balance,can select the ta...Principal component analysis(PCA)has been already employed for fault detection of air conditioning systems.The sliding window,which is composed of some parameters satisfying with thermal load balance,can select the target historical fault-free reference data as the template which is similar to the current snapshot data.The size of sliding window is usually given according to empirical values,while the influence of different sizes of sliding windows on fault detection of an air conditioning system is not further studied.The air conditioning system is a dynamic response process,and the operating parameters change with the change of the load,while the response of the controller is delayed.In a variable air volume(VAV)air conditioning system controlled by the total air volume method,in order to ensure sufficient response time,30 data points are selected first,and then their multiples are selected.Three different sizes of sliding windows with 30,60 and 90 data points are applied to compare the fault detection effect in this paper.The results show that if the size of the sliding window is 60 data points,the average fault-free detection ratio is 80.17%in fault-free testing days,and the average fault detection ratio is 88.47%in faulty testing days.展开更多
It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, t...It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.展开更多
The energy consumption of a Split air conditioning unit(ACU)inside a building is extremely large,and efforts to decrease this issue are ongoing.The current work aims to experimentally investigate the thermal performan...The energy consumption of a Split air conditioning unit(ACU)inside a building is extremely large,and efforts to decrease this issue are ongoing.The current work aims to experimentally investigate the thermal performance of ACU using an external cooling-water loop for pre-cooling the condenser to improve the efficiency and to reduce energy consumption by reducing refrigerant temperature before entering the condenser,thereby reducing the coefficient of performance.The experiments are performed on ACU with and without using an external cooling-water loop under different climate conditions.By using the experimental data,the systems’performances for both cases are evaluated based on the energy,exergy,and pressure drop analysis.Effects of several parameters,e.g.,ambient temperature,inlet water temperature,and water volume flow rate,on the energy and exergy performances of ACU systems are presented for the purpose of comparison.The outcomes display that the use of an external cooling water loop system has a significant impact on the system performance as compared to conventional ACU.The results display that the addition of an external cooling-water loop leads to a reduction in the compressor power consumption and to an increase in the coefficient of performance(COP)as compared to a normal ACU.The maximum reduction in compressor power consumption is obtained equal 37%at T_(w)=15℃and 11 L/min,whereas the maximum enhancement in COP is obtained equal 21.5%at T_(w)=30℃,11 L/min,and T_(amb)=45℃.The modified model shows an increase in exergy efficiency with the maximum enhancement of about 17%at T_(w)=30℃and 15.8 L/min.The use of an external cooling water loop leads to a reduction in the irreversibility process of the compressor,evaporator and expansion valve and to an increase in the condenser losses.The outcomes show that the pressure drop is reduced by using a cooling water loop as compared to a normal ACU,where the reduction becomes more evident with a reduction in water volume flow rate and inlet temperature.Finally,the present study reveals that the use of an external cooling water loop system leads to an improvement in the performance of ACUs.展开更多
In the background of reform of higher education in the new era,how to organically integrate innovation and entrepreneurship education with curriculum ideology and politics has become a key proposition for deepening th...In the background of reform of higher education in the new era,how to organically integrate innovation and entrepreneurship education with curriculum ideology and politics has become a key proposition for deepening the reform of education and teaching.As an important branch in the field of engineering,the refrigeration and air conditioning major not only undertakes the professional mission of cultivating technical talents in the industry,but also shoulders the era responsibility of implementing the fundamental task of cultivating morality and talents.Combining with the characteristics of the refrigeration and air conditioning major,this paper systematically analyzes the internal logic and practical significance of the integration of innovation and entrepreneurship education and curriculum ideology and politics,and explores its implementation paths in aspects such as the excavation of curriculum content,the innovation of teaching methods,the construction of practical platforms and the optimization of evaluation systems.It aims to provide practical reference and theoretical support for promoting the collaborative education of professional education and ideological and political education.展开更多
Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393-473 K/293-323 K/263-273 K. Property tests showed that...Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393-473 K/293-323 K/263-273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance （COP） is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1-1.6 W/（m-K）, which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.展开更多
文摘Thermoelectric air conditioning systems based on the Peltier effect had two modes:heating and cooling.In this work,the proposed design provides continuous improvement in COP from the first minute of operation.In cooling mode,the coefficient of performance(COP)was 1.176 due to the techniques used in this device,and it increased to 1.24 in the last minute of operation.Concerning the steady-state scenario,from the first minute,the Qc was larger than the W for the entire duration of the operation.The output temperature reaches 18.97℃ ,and the temperature on the cold side reaches 4.96℃ in the fifteen minutes of operation.The cooling mood was checked in Iraq/Baghdad in October with a temperature of 31℃ .Furthermore,the heating mode was checked in December with a temperature of 22℃ .Due to the size of the component on the cold side being small compared with the size of the component on the heat side,it reached a steady state in 13 min.This means the COP in heating mode reached 1.01 in 14 min.Furthermore,due to the presence of a thermal insulator made inside the device to separate the cold side and the hot side,the difference in temperature causes a noticeable little ascent.This is why the COP increased because it kept the degree differences low.Performance enhancements were achieved by optimizing the behavior of thermoelectric materials.The device contains 3 Peltier elements,a water-cooled system with one Peltier,a heat sink,and a fan.The design of the dehumidification system addresses the humidity issue commonly associated with thermoelectric air conditioners.In this context,the results indicate that the humidity rates had decreased and the cooling rate had increased with these innovative techniques,and thus,excellent performance can be achieved even if the Seebeck coefficient is not at its highest based on the condition of providing the Peltier elements’reliability and optimal thermal performance for various applications requiring both cooling and heating functions.The insulation plays a critical role in maintaining the efficiency of the system,reducing energy consumption,and ensuring long-term functionality.The proposed system is valuable for devices or environments that demand precise and dual thermal control with minimal energy wastage.
文摘LDACs(liquid desiccant air-conditioners)with heat pump can perform cooling dehumidification or heating humidification,and have high energy-saving and sterilization performance.Therefore,they are installed in hospitals,nursing homes,and food factories,where humidity control is required.However,LiCl(lithium chloride),a conventional humidity control liquid,is highly corrosive to metals,requiring the use of highly corrosion-resistant materials for the pipes and the heat exchangers.These lead to the problem that the manufacturing cost of the air conditioner increases.Therefore,we developed an inexpensive and compact LDAC by adopting a novel IL(ionic liquid)that does not corrode the metals commonly used in air conditioners.In this study,we evaluated the metal solubilities and sterilizing properties of the IL.Based on the physical properties of the IL,the humidity control module was improved for the purpose of downsizing and cost reduction of the unit.Moreover,we conducted a performance evaluation of the LDAC in the environmental test room under the condition in which temperature and humidity change rapidly in short period of time to simulate the condition of sudden showers of rain in summer.Test results showed that processed air was supplied at very stable level.
文摘As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy consumption,how to improve the energy efficiency ratio of air conditioning systems and reduce energy consumption has become an important issue in research and practice.The purpose of this paper is to discuss the impact of humidity control strategies on energy saving in centralized central air conditioning systems,with a view to providing a theoretical basis and practical guidance for realizing building energy efficiency.
文摘The central air conditioning system in an intelligent building (IB) was analyzed and modeled in order to perform the optimization scheduling strategy of the central air conditioning system. A set of models proposed and a type of periodically autoregressive model (PAR) based on the improved genetic algorithms (IGA) were used to perform the optimum energy saving scheduling. The example of the Liangmahe Plaza was taken to show the effectiveness of the methods.
文摘This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.
文摘An optimum energy saving scheduling strategy of the central air conditioning system in an intelligent building (IB) was proposed. Based on the system analysis a set of models of the central air conditioning system was established. The periodically autoregressive models (PARM) based on genetic algorithms (GA) were used to predict the next day’s cold load. The improved genetic algorithms (IGA) with stochastic real number coding were used to finish the optimum energy saving scheduling of the system. The simulation results for the building of the Liangmahe Plaza show that the proposed strategy can save energy up to about 24 5%.
基金supported by National Natural Science Foundation of China(91860139)China Postdoctoral Science Foundation(2015M581792)。
文摘The vast potential of system health monitoring and condition based maintenance on modern commercial aircraft is being realized through the innovative use of Airplane Condition Monitoring System(ACMS) data.However there are few methods addressing the issues of failure prognostics and predictive maintenance for commercial aircraft Air Conditioning System(ACS).This study developed a Bayesian failure prognostics approach using ACMS data for predictive maintenance of ACS.First, a health index characterizing the ACS health state is inferred from a multiple sensor signals using a data driven method.Then a dynamic linear model is proposed to describe the degradation process for failure prognostics.Bayesian inference formulas are carried out for degradation estimation and prediction.The developed approach is applied on a passenger aircraft fleet with ACMS data recorded for one year.The analysis of the case study shows that the developed method can produce satisfactory prognostics results, where all the ACS failure precursors are identified in advance, and the relative errors for the failure time prediction made when just entering the degradation warning stage are less than 8%.This would allow operators to proactively plan future maintenance.
基金Project supported by the Youth Programs of Chongqing Three Gorges University,China(Grant No.13QN18)
文摘In this paper,based on the generalized heat transfer law,an air conditioning system is analyzed with the entropy generation minimization and the entransy theory.Taking the coefficient of performance（denoted as COP） and heat flow rate Qout which is released into the room as the optimization objectives,we discuss the applicabilities of the entropy generation minimization and entransy theory to the optimizations.Five numerical cases are presented.Combining the numerical results and theoretical analyses,we can conclude that the optimization applicabilities of the two theories are conditional.If Qout is the optimization objective,larger entransy increase rate always leads to larger Qout,while smaller entropy generation rate does not.If we take COP as the optimization objective,neither the entropy generation minimization nor the concept of entransy increase is always applicable.Furthermore,we find that the concept of entransy dissipation is not applicable for the discussed cases.
基金the National Key Technologies Research and Development Program of China During the 12th Five-Year Plan Period(No.SQ2011GX03D03999)
文摘Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent studies, R1234 yf is considered as one of the top candidates to replace R134 a. In this article, the performances of R1234 yf "drop-in" system and the optimization to the R1234 yf system are experimentally studied and investigated.The expansion valve used for the R1234 yf system is optimized by changing the charged fluid and adjusting the spring force. The results indicate that it can improve the performance of R1234 yf system significantly through adjusting the thermostatic expansion valve. For the thermostatic expansion valves(TEVs) charged with R134 a in thermal bulb, the system performance is optimal. Compared to the original expansion valve, for the R1234 yf system applying the adjusted expansion valves, under different working conditions the cooling capacity increases by 11.3% averagely and the coefficient of performance(COP) increases by 8% averagely.
基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)and the Foundation of Jiangsu Postdoctoral(No.2019K126)。
文摘An aircraft cabin is a narrow,closed-space environment.To keep the air quality in cabin healthy for passengers,especially during an epidemic such as SARS-CoV-2(or 2019-nCoV)in 2020,a novel aircraft air conditioning system,called the ultra-high-temperature instantaneous sterilization air conditioning system(UHTACS),is proposed.Based on the proposed system,a simulation of the UHT-ACS is analysed in various flight states.In the UHT-ACS,the mixing air temperature of return and bleed air can reach temperature up to 148.8°C,which is high enough to kill bacilli and viruses in 2一8 s.The supply air temperature of the UHT-ACS in a mixing cavity is about 12 C in cooling mode both on the ground and in the air.The supply air temperature is about 42 C in heating mode.Compared with the air conditioning systems(ACS)of traditional aircraft the supply air temperatures of the UHT-ACS in the mixing cavity are in good agreement with those of a traditional ACS with 60%fresh air and 40%return air.Furthermore the air temperature at the turbine outlet of the UHT-ACS is higher than that of a traditional ACS which will help to reduce the risk of icing at the outlet.Therefore the UHT-ACS can operate normally in various flight states.
基金supported by a fund for environmental research from Tottori University
文摘Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing interest from the stand point of reducing energy consumption during dehumidification. In order to find the appropriate ionic liquids(ILs) as a desiccant for the liquid desiccant air-conditioner system, we conducted a systematic evaluation of the humidification capability of 16 types of ILs. Among the tested ILs, tributyl(methyl)phosphonium dimethyl phosphate([P4441][DMPO_4]) exhibited the best dehumidification capacity and had a less corrosive effect on four types of metals as possible piping materials. It should be noted that this [P_(4441)][DMPO_4] has a very stable nature and produced no odor while conducting the experiment and storing for over 1 year at room temperature under ambient conditions. Furthermore, it was revealed that a 77%(w/w) aqueous solution of [P4441][DMPO_4] worked as an efficient desiccant liquid for the liquid desiccant air-conditioner system.
文摘As an environmentally harmless and feasible alternate refrigerant, CO 2 has attracted worldwide attention, especially in the area of automobile air conditioning (AAC). The thermal property of CO 2 and its trans critical refrigeration cycle is very different from that of the traditional CFC or HCFC system. The detailed process of CO 2 system thermal cycle design and optimization is described in this paper. System prototype and performance test bench were developed to analyze the performance of the CO 2 AAC system.
基金Research Project of China Ship Development and Design Center。
文摘Screening similar historical fault-free candidate data would greatly affect the effectiveness of fault detection results based on principal component analysis(PCA).In order to find out the candidate data,this study compares unweighted and weighted similarity factors(SFs),which measure the similarity of the principal component subspace corresponding to the first k main components of two datasets.The fault detection employs the principal component subspace corresponding to the current measured data and the historical fault-free data.From the historical fault-free database,the load parameters are employed to locate the candidate data similar to the current operating data.Fault detection method for air conditioning systems is based on principal component.The results show that the weighted principal component SF can improve the effects of the fault-free detection and the fault detection.Compared with the unweighted SF,the average fault-free detection rate of the weighted SF is 17.33%higher than that of the unweighted,and the average fault detection rate is 7.51%higher than unweighted.
基金PhD Programs Foundation of Ministry of Education of China( No.20060255006)Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (No.706024)
文摘Air conditioning (AC) system is the one with asynchronous and uncertain nature. In this paper, the fuzzy discrete event system (FDES) is introduced to the research of AC energy-saving control. A fuzzy automaton modeling is given for AC energy-saving control and effectiveness optimization is made. To facilitate the implement of the control and energy saving, priorities have been assigned to the major control steps based on logical reasoning. Forward-looking tree modeling based on FDES has been simplified to help further optimization, and a simple and concrete example has been put forward illustrating energy-saving control in AC system.
文摘According to the requirements of welding process for vortex type compressor of air conditioner manufactured in product line, a special girth welding machine with PLC as control core was developed, which had both upright and 45 ° incline service positions. And some key technologies were researched, such as structural design of machine body, reliable conduction of rotary weldments and quality control of welding process and so on. The experimental results showed that this machine could satisfy the requirements of welding quality and girth welding technology, results also proved the machine was a high-effwiency and low-cost automatic welding device.
基金Fundamental Research Funds for the Central Universities of Ministry of Education of China。
文摘Principal component analysis(PCA)has been already employed for fault detection of air conditioning systems.The sliding window,which is composed of some parameters satisfying with thermal load balance,can select the target historical fault-free reference data as the template which is similar to the current snapshot data.The size of sliding window is usually given according to empirical values,while the influence of different sizes of sliding windows on fault detection of an air conditioning system is not further studied.The air conditioning system is a dynamic response process,and the operating parameters change with the change of the load,while the response of the controller is delayed.In a variable air volume(VAV)air conditioning system controlled by the total air volume method,in order to ensure sufficient response time,30 data points are selected first,and then their multiples are selected.Three different sizes of sliding windows with 30,60 and 90 data points are applied to compare the fault detection effect in this paper.The results show that if the size of the sliding window is 60 data points,the average fault-free detection ratio is 80.17%in fault-free testing days,and the average fault detection ratio is 88.47%in faulty testing days.
文摘It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.
文摘The energy consumption of a Split air conditioning unit(ACU)inside a building is extremely large,and efforts to decrease this issue are ongoing.The current work aims to experimentally investigate the thermal performance of ACU using an external cooling-water loop for pre-cooling the condenser to improve the efficiency and to reduce energy consumption by reducing refrigerant temperature before entering the condenser,thereby reducing the coefficient of performance.The experiments are performed on ACU with and without using an external cooling-water loop under different climate conditions.By using the experimental data,the systems’performances for both cases are evaluated based on the energy,exergy,and pressure drop analysis.Effects of several parameters,e.g.,ambient temperature,inlet water temperature,and water volume flow rate,on the energy and exergy performances of ACU systems are presented for the purpose of comparison.The outcomes display that the use of an external cooling water loop system has a significant impact on the system performance as compared to conventional ACU.The results display that the addition of an external cooling-water loop leads to a reduction in the compressor power consumption and to an increase in the coefficient of performance(COP)as compared to a normal ACU.The maximum reduction in compressor power consumption is obtained equal 37%at T_(w)=15℃and 11 L/min,whereas the maximum enhancement in COP is obtained equal 21.5%at T_(w)=30℃,11 L/min,and T_(amb)=45℃.The modified model shows an increase in exergy efficiency with the maximum enhancement of about 17%at T_(w)=30℃and 15.8 L/min.The use of an external cooling water loop leads to a reduction in the irreversibility process of the compressor,evaporator and expansion valve and to an increase in the condenser losses.The outcomes show that the pressure drop is reduced by using a cooling water loop as compared to a normal ACU,where the reduction becomes more evident with a reduction in water volume flow rate and inlet temperature.Finally,the present study reveals that the use of an external cooling water loop system leads to an improvement in the performance of ACUs.
基金Undergraduate Teaching Research and Reform Project of the University of Shanghai for Science and Technology(Project No.:JGXM202526)。
文摘In the background of reform of higher education in the new era,how to organically integrate innovation and entrepreneurship education with curriculum ideology and politics has become a key proposition for deepening the reform of education and teaching.As an important branch in the field of engineering,the refrigeration and air conditioning major not only undertakes the professional mission of cultivating technical talents in the industry,but also shoulders the era responsibility of implementing the fundamental task of cultivating morality and talents.Combining with the characteristics of the refrigeration and air conditioning major,this paper systematically analyzes the internal logic and practical significance of the integration of innovation and entrepreneurship education and curriculum ideology and politics,and explores its implementation paths in aspects such as the excavation of curriculum content,the innovation of teaching methods,the construction of practical platforms and the optimization of evaluation systems.It aims to provide practical reference and theoretical support for promoting the collaborative education of professional education and ideological and political education.
基金Project (No. 50276063) supported by the National Natural Science Foundation of China
文摘Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393-473 K/293-323 K/263-273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance （COP） is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1-1.6 W/（m-K）, which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.
