The simulation model for performance of chiller (ASHRAE model in this study) disclosed in ASHRAE Guideline 14 in 2002 is implemented in Taiwan to verify the efficiency of energy-saving methods adopted by energy servic...The simulation model for performance of chiller (ASHRAE model in this study) disclosed in ASHRAE Guideline 14 in 2002 is implemented in Taiwan to verify the efficiency of energy-saving methods adopted by energy service companies (ESCO). Since the accuracy of the simulation model for performance of chillers has influenced on the promotion of the ESCO business, the author used practical measurement data to compare the accuracy between the ASHRAE model and the commonly used energy consumption model of chillers (XY model in this study) and concluded that the XY model had much higher accuracy than the ASHRAE model.展开更多
Fault detection is beneficial for chiller routine operation management in building automation systems.Considering the limitations of traditional principal component analysis(PCA)algorithm for chiller fault detection,a...Fault detection is beneficial for chiller routine operation management in building automation systems.Considering the limitations of traditional principal component analysis(PCA)algorithm for chiller fault detection,a so-called kernel entropy component analysis(KECA)method has been developed and the development results are reported in this paper.Unlike traditional PCA,in KECA,the feature extraction or dimensionality reduction is implemented in a new space,called kernel feature space.The new space is nonlinearly related to the input space.The data set in the kernel feature space is projected onto a principal component subspace constructed by the feature space principal axes determined by the maximum Rényi entropy rather than the top eigenvalues.The proposed KECA is more suitable to deal with nonlinear process without Gaussian assumption.Using the available experimental data from ASHRAE RP-1043,seven typical chiller faults were tested by the proposed KECA method,and the results were compared to that of PCA.Two statistics,i.e.T2 and squared prediction error(SPE),were employed for fault detection monitoring.The fault detection results showed that the proposed KECA method had a better performance in terms of a higher detection accuracy in comparison to the traditional PCA.For the seven typical faults,the fault detection ratios were over 55%,even at their corresponding least severity level when using the proposed KECA based chiller fault detection method.展开更多
Practical applications of data-driven fault detection(FD)are limited by their portability.The costs of model training and validation are extremely high when each system requires a model retrained on its own fault and ...Practical applications of data-driven fault detection(FD)are limited by their portability.The costs of model training and validation are extremely high when each system requires a model retrained on its own fault and fault-free data.Therefore,this paper proposes a statistical-based online cross-system FD method to address the problem of model portability.The proposed FD model can be cross-utilized between building chillers with various specifications while it only needs to update the original fault detection model by the normal operation data of the new chiller system,thus saving huge fault experimental costs for the fault detection of new chiller.First,a theoretical basis for the proposed cross-system fault detection method is presented.Then,experiments were conducted on three building chillers with different specifications.Both fault and fault-free data were collected from the three chillers.The development and validation of the proposed cross-system fault detection method are then conducted.Results show that the cross-system fault detection models perform well when used with different chillers.For instance,when the fault detection model of system#1 was cross-utilized to system#2,the detection accuracies of refrigerant leakage,refrigerant overcharge,and reduced evaporator water flow were 99.73%,90.17%,and 96.94%,respectively.Compared with original models,the detection accuracies were improved by 33.78%,84.07%,and 65.56%,respectively.Therefore,the proposed cross-system fault detection method has potential for online application to practical engineering FD.展开更多
Thermal adsorption cooling systems have gained significant attention due to their potential for energy savings and eco-environmental impact. An analytic investigation of the heat transfer inside an adsorption chiller ...Thermal adsorption cooling systems have gained significant attention due to their potential for energy savings and eco-environmental impact. An analytic investigation of the heat transfer inside an adsorption chiller with various bed silica gel-water pairs is presented. A comprehensive model has been designed to accurately predict the correlation between the overall performance of the proposed chiller system and the functional and structural condition of the building. This model takes into account various factors such as temperature, humidity, and air quality to provide a detailed analysis of the system’s efficiency. At least 20 collectors consisting of a 34.4 m area (each) with a full-cycle time of 480 seconds are essential to improper run conditions. It is necessary to adjust the optimum cycle time for optimal performance. During the investigation, the base condition shows that the cooling capacity is 14 kw, 0.6 COPcycle, and 0.35 COPsolar at noon. Also, conduct a thorough investigation into the chiller’s performance under varying cooling water supply temperatures and various chilled water flow rates.展开更多
A dynamic model is presented for a chiller working with a composite adsorbent(silica activated carbon/CaCl2)–water pair in a solar-biomass cooling installation.The main objective is determining a link between two pos...A dynamic model is presented for a chiller working with a composite adsorbent(silica activated carbon/CaCl2)–water pair in a solar-biomass cooling installation.The main objective is determining a link between two possible evaporator configurations and the refrigerator’s performances.The two considered evaporators work at different pressure levels.The related time evolution profiles of temperature,pressure and water content are studied.Moreover,the effects of hot water inlet temperature and cooling water inlet temperature on the specific cooling capacity(SCP)and coefficient of performance(COP)are predicted by means of numerical simulations.The results show that an increase in the temperature of hot water and a decrease in the temperature of the cooling water allow an increase in COP and SCP.In particular,for a hot water inlet temperature of 85°C and a cooling water inlet temperature of 40°C,the COP and Qev are 0.67 and 4.3 kW,respectively.展开更多
This paper proposes a modified golden jackal optimization(IGJO)algorithm to solve the OCL(which stands for optimal cooling load)problem to minimize energy consumption.In this algorithm,many tools have been developed,s...This paper proposes a modified golden jackal optimization(IGJO)algorithm to solve the OCL(which stands for optimal cooling load)problem to minimize energy consumption.In this algorithm,many tools have been developed,such as numerical visualization,local field method,competitive selectionmethod,and iterative strategy.The IGJO algorithm is used to improve the research capabilities of the algorithm in terms of global tuning and rotation speed.In order to fully utilize the effectiveness of the proposed algorithm,three famous examples of OCL problems in basic ventilation systems were studied and compared with some previously published works.The results show that the IGJO algorithm can find solutions equal to or better than other methods.Underpinning these studies is the need to reduce energy consumption in air conditioning systems,which is a critical business and environmental decision.The Optimal Chiller Load(OCL)problem is well-known in the industry.It is the best method of operation for the refrigeration plant to satisfy the requirement of cooling.In order to solve the OCL problem,an improved Golden Jackal optimization algorithm(IGJO)was proposed.The IGJO algorithm consists of a number of parts to improve the global optimization and rotation speed.These studies are intended to address more effectively the issue of OCL,which results in energy savings in air-conditioning systems.The performance of the proposed IGJO algorithm is evaluated,and the results are compared with the results of three known OCL problems in the ventilation system.The results indicate that the IGJO method has the same or better optimization ability as other methods and can improve the energy efficiency of the system’s cold air.展开更多
Use of district heating and cooling systems has many environmental advantages compared to individual heating and cooling. Recent advances in solar energy technologies for heat and power generation have reduced their c...Use of district heating and cooling systems has many environmental advantages compared to individual heating and cooling. Recent advances in solar energy technologies for heat and power generation have reduced their cost and promoted their use instead of fossil fuels. Solar-PV energy for electricity generation and solar thermal energy for hot water production are broadly used today. Solar energy resources in the Mediterranean region are abundant while space cooling in buildings is required when solar irradiance is high. The possibility of using solar energy for fuelling water chillers providing cold water in district cooling systems in the Mediterranean basin has been investigated. Existing literature and studies concerning the use of district cooling systems globally as well as the energy sources used in them have been examined. Solar-PV energy combined with compression chillers and solar thermal energy combined with thermally driven chillers can be used for cold water production. Their overall efficiencies, converting solar energy to cold water, vary between 22% and 56% compared with 45% for compression chillers using grid electricity. It is concluded that various solar energy technologies could be used with different types of water chillers for fuelling district cooling networks in the future in the Mediterranean region.展开更多
Computer-empowered detection of possible faults for Heating,Ventilation and Air-Conditioning(HVAC)subsystems,e.g.,chillers,is one of the most important applications in Artificial Intelligence(AI)integrated Internet of...Computer-empowered detection of possible faults for Heating,Ventilation and Air-Conditioning(HVAC)subsystems,e.g.,chillers,is one of the most important applications in Artificial Intelligence(AI)integrated Internet of Things(IoT).The cyber-physical system greatly enhances the safety and security of the working facilities,reducing time,saving energy and protecting humans’health.Under the current trends of smart building design and energy management optimization,Automated Fault Detection and Diagnosis(AFDD)of chillers integrated with IoT is highly demanded.Recent studies show that standard machine learning techniques,such as Principal Component Analysis(PCA),Support Vector Machine(SVM)and tree-structure-based algorithms,are useful in capturing various chiller faults with high accuracy rates.With the fast development of deep learning technology,Convolutional Neural Networks(CNNs)have been widely and successfully applied to various fields.However,for chiller AFDD,few existing works are adopting CNN and its extensions in the feature extraction and classification processes.In this study,we propose to perform chiller FDD using a CNN-based approach.The proposed approach has two distinct advantages over existing machine learning-based chiller AFDD methods.First,the CNN-based approach does not require the feature selection/extraction process.Since CNN is reputable with its feature extraction capability,the feature extraction and classification processes are merged,leading to a more neat AFDD framework compared to traditional approaches.Second,the classification accuracy is significantly improved compared to traditional methods using the CNN-based approach.展开更多
The relationship among the working temperature,pressure and current density of a Solid oxide fuel cell(SOFC)and its output power and efficiency are analyzed in the framework of a theoretical model able to provide,amon...The relationship among the working temperature,pressure and current density of a Solid oxide fuel cell(SOFC)and its output power and efficiency are analyzed in the framework of a theoretical model able to provide,among other things,the volt ampere characteristic curve.In particular,following the principle of temperature matching and cascade utilization,we consider a gas turbine(GT)and a LiBr absorption chiller to recycle the high-grade exhaust heat produced by the considered SOFC.This distributed total energy system is set up with the intent to meet typical needs of buildings for cooling,heating and power(CCHP).The total power generated by the considered SOFC and gas turbine is about 222 kW and the total power generation efficiency by low heat value of fuel(LHV)is 63.7%.In the CCHP system,the high temperature exhaust of GT is further used to drive LiBr absorption unit,which can produce about 34.8 kW cooling capacity or 84.5 kW of heat(the total energy utilization 78.03%).展开更多
A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating ...A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.展开更多
Gas turbine (GT) power plants operating in arid climates suffer a decrease in output power during the hot summer months because of the high specific volume of air drawn by the compressor. Cooling the air intake to the...Gas turbine (GT) power plants operating in arid climates suffer a decrease in output power during the hot summer months because of the high specific volume of air drawn by the compressor. Cooling the air intake to the compressor has been widely used to mitigate this shortcoming. Energy and exergy analysis of a GT Brayton cycle coupled to a refrigeration air cooling unit shows a promise for increasing the output power with a little decrease in thermal efficiency. A thermo-economics algorithm is developed to estimate the economic feasibility of the cooling system. The analysis is applied to an open cycle, HITACHI-FS7001B GT plant at the industrial city of Yanbu (Latitude 24o 05” N and longitude 38o E) by the Red Sea in the Kingdom of Saudi Arabia. Result show that the enhancement in output power depends on the degree of chilling the air intake to the compressor (a 12 - 22 K decrease is achieved). For this case study, maximum power gain ratio (PGR) is 15.46% (average of 12.25%), at an insignificant decrease in thermal efficiency. The second law analysis show that the exergetic power gain ratio drops to an average 8.5%. The cost of adding the air cooling system is also investigated and a cost function is derived that incorporates time-dependent meteorological data, operation characteristics of the GT and the air intake cooling system and other relevant parameters such as interest rate, lifetime, and operation and maintenance costs. The profit of adding the air cooling system is calculated for different electricity tariff.展开更多
To a kind of centrifugal water chiller with R22 and about 1 745 kW of cooling capacity,a heat exchanger was added between the outlet of compressor and original condenser to get part of or all the condensing heat.Conde...To a kind of centrifugal water chiller with R22 and about 1 745 kW of cooling capacity,a heat exchanger was added between the outlet of compressor and original condenser to get part of or all the condensing heat.Condensing heat can be recovered by compound condensing method,which adopts air-cooling model +water-cooling model or water-cooling model +water-cooling model at the condensing side of the system.By exergy analysis and experiment research on compound condensing heat recovery of centrifugal chiller,the results are obtained that the capability of the whole system increases,the energy efficiency ratio(EER)becomes 3.2~5.0 from 2.2~3.4,which implies the EER increases about 1.0~1.5,the exergy efficiency increases about 10%,and the chiller runs more stably after reformation.展开更多
A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship betwe...A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship between pressure, temperature and concentration of the lithium bromide solution have been analyzed. The result obtained indicates that the pressure of the high pressure generator and the temperature of the exhausted smoke are the most sensitive parameters. It is also found that the transition time from a full load to a part load condition is quite long, and part load relative cooling capacity is almost near the intermittent running time ratio and oil consumption ratio.展开更多
The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will ...The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will greatly deepen the coupling of the electricity-gas integrated energy system,improve the flexibility and safety of the operation of the power system,and bring a deal of benefits to the power system.On this background,an optimal dispatch model of RIES combined cold,heat,gas and electricity with SOP is proposed.Firstly,RIES architecture with SOP and P2G is designed and its mathematical model also is built.Secondly,on the basis of considering the optimal scheduling of combined cold,heat,gas and electricity,the optimal scheduling model for RIES was established.After that,the original model is transformed into a mixed-integer second-order cone programming model by using linearization and second-order cone relaxation techniques,and the CPLEX solver is invoked to solve the optimization problem.Finally,the modified IEEE 33-bus systemis used to analyze the benefits of SOP,P2G technology and lithium bromide absorption chillers in reducing systemnetwork loss and cost,as well as improving the system’s ability to absorb wind and solar and operating safety.展开更多
Hybrid<span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family...Hybrid<span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">chiller plants (HCPs)</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">using multiple chillers and different energy sources</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">are highly recommended in several energy applications in non-residential buildings such as hospitals and hotels. Time of use and cooling load profiles are significant factors that should be carefully considered either in chiller plant design or in chiller sequencing operation. This article aims to present an operation planning of HCP which consists of both electric and non-electric chillers. Four operational strategies are proposed and solved to compare their coefficients of performance and economics of running costs. A typical hotel building located on the Nile river in Egypt is selected to perform the current thermal and economic case study. The total cooling load profile of this hotel building is 4000 refrigeration tonnage (TR), which </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">simulated to optimize chiller sequence of operation and to select optimal design conditions of both numbers for electric and non-electric chillers used in HCP. The results of this comparative study for running cost are defined using various design configurations with different several chiller sequences available for each configuration. Then, the results of COPs, and operational running cost and initial cost are presented in this article also. The comparison aims to find the optimal design and operational sequencing for HCPs on thermal basis and economic analysis which were attached in this article. Recommendations and suggestions for future work are attached at the end of this article.</span></span></span>展开更多
Cold energy generation systems must be improved to prevent catastrophic climate change. In this study, we focused on an absorption chiller cycle with HFC-134a and an ionic liquid pair as the refrigerant and absorbent,...Cold energy generation systems must be improved to prevent catastrophic climate change. In this study, we focused on an absorption chiller cycle with HFC-134a and an ionic liquid pair as the refrigerant and absorbent, respectively. It was expected that this absorption chiller cycle could generate cold heat below 0°C. Two liquids were selected and their absorption equilibrium with this pair was evaluated for the absorption chiller cycle. We measured the adsorbed amount at equilibrium with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][Tf2N] and N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide [N1113][Tf2N]. The experimental results were reproduced using the non-random two liquid (NRTL) model. This analysis model corresponded well in terms of the amount of adsorption at equilibrium with the experimental results. A Duhring diagram was also generated the NRTL model, and the absorption cycle characteristics as a function of temperature were determined. The absorption chiller cycle obtained cold heat at 10°C with a regeneration temperature of 70°C in addition to generating cold heat below 0°C.展开更多
Large amounts of waste heat below 100oC from the industrial sector are re-leased into the atmosphere. It has been suggested that energy system efficiency can be increased with adsorption chillers. However, the cooling...Large amounts of waste heat below 100oC from the industrial sector are re-leased into the atmosphere. It has been suggested that energy system efficiency can be increased with adsorption chillers. However, the cooling power and coefficient of performance (COP) of conventional adsorption chillers significantly decrease with the desorption temperature. In this paper, we proposed a mechanical booster pump (MBP)-assisted adsorption chiller cycle, and evaluated its performances. In the cycle, a MBP was incorporated into a zeolite-water-type adsorption chiller for facilitating water vapor transportation between an adsorber and an evaporator/condenser. We have experimentally studied the effect of the input electrical power of MBP on the performances of adsorption chiller cycle. It has been demonstrated that the heat input achieved by using MBP at the desorption temperature of 50oC was 1.6 times higher than that of without MBP at the desorption temperature of 60oC. And the increase of pump power was found to be effective in increasing the heat input. Therefore, it was confirmed that the operation range of desorption temperature, which can be generated by using the waste heat, was extended and the cooling power was increased directly by using MBP.展开更多
The research was aimed at providing water for cooling recycled cyclohexane in polyethylene plant to 15°C. This research could be redounding to the benefit of polyethylene plants that are using solution based poly...The research was aimed at providing water for cooling recycled cyclohexane in polyethylene plant to 15°C. This research could be redounding to the benefit of polyethylene plants that are using solution based polymerization technique. A chiller unit of 630 T, which has compressor power input of 378.33 kW and can provide chilled water capable of cooling recycle cyclohexane to 15°C, was designed using Aspen Hysys version 7.1. Four different refrigerants were tested to know the best fit refrigerant for the design and the best among them was R134a. The designed chiller has a coefficient of performance of 6.3 and a capacity greater than that of the defective chiller (550 TR). Unlike the defective chiller, with the increased cooling capacity and corresponding increase in compressor power from 296 kW to 378.6 kW, it could discharge chilled water capable of cooling recycle cyclohexane from 38°C to 15°C without tripping of the unit. With this design, ethylene absorption rate could increase to 40 T/h. Evaporator and condenser were designed and duties were 2166.39 KJ/sec and 2544.72 KJ/sec respectively. A thermostatic expansion valve with flow coefficient of 46.17 gpm was designed. The designed suction and discharge pressure were 414 kpa and 1053 kpa respectively while condenser temperature of 40°C was used for the design. The cooling of recycle cyclohexane from 38°C to 15°C using the chilled water supplied by the designed chiller was simulated using Aspen Hysys.展开更多
In this paper, the model of chiller power consumption is built by using the regression analysis. While taking the parameters from the operation data of chiller into consideration simultaneously, i.e. Partial Load Rati...In this paper, the model of chiller power consumption is built by using the regression analysis. While taking the parameters from the operation data of chiller into consideration simultaneously, i.e. Partial Load Ratio (PLR), chilled water supply temperature and cooling water return temperature, the prediction results are quite accurate, and its accuracy reaches over 99% in short-term prediction when compared with the actual power consumption. This method can be used to validate the benefits of the chiller’s energy saving method. The validation items include: the effect of water flow change on chiller’s performance while multiple chillers operate in parallel;the power consumption analysis of centrifugal chiller operating with or without frequency conversion;as well as the discussion on whether the cleaning of condenser coil can improve the Coefficient of Performance (COP) of chiller or not. The case study results show that, while multiple chillers operate in parallel, the water flow change has limited effect on the performance of chiller. However, about 36% electricity can be saved averagely when the chiller controls the frequency of electric power source at partial load, and the cleaning of condenser coil can increase the COP by 3.08%.展开更多
文摘The simulation model for performance of chiller (ASHRAE model in this study) disclosed in ASHRAE Guideline 14 in 2002 is implemented in Taiwan to verify the efficiency of energy-saving methods adopted by energy service companies (ESCO). Since the accuracy of the simulation model for performance of chillers has influenced on the promotion of the ESCO business, the author used practical measurement data to compare the accuracy between the ASHRAE model and the commonly used energy consumption model of chillers (XY model in this study) and concluded that the XY model had much higher accuracy than the ASHRAE model.
基金The financial supports for the Natural Science Foundation of Zhejiang Province(Project No.LQ19E060007)are gratefully acknowledged.
文摘Fault detection is beneficial for chiller routine operation management in building automation systems.Considering the limitations of traditional principal component analysis(PCA)algorithm for chiller fault detection,a so-called kernel entropy component analysis(KECA)method has been developed and the development results are reported in this paper.Unlike traditional PCA,in KECA,the feature extraction or dimensionality reduction is implemented in a new space,called kernel feature space.The new space is nonlinearly related to the input space.The data set in the kernel feature space is projected onto a principal component subspace constructed by the feature space principal axes determined by the maximum Rényi entropy rather than the top eigenvalues.The proposed KECA is more suitable to deal with nonlinear process without Gaussian assumption.Using the available experimental data from ASHRAE RP-1043,seven typical chiller faults were tested by the proposed KECA method,and the results were compared to that of PCA.Two statistics,i.e.T2 and squared prediction error(SPE),were employed for fault detection monitoring.The fault detection results showed that the proposed KECA method had a better performance in terms of a higher detection accuracy in comparison to the traditional PCA.For the seven typical faults,the fault detection ratios were over 55%,even at their corresponding least severity level when using the proposed KECA based chiller fault detection method.
基金This work was supported by the Natural Science Foundation of Chongqing(No.cstc2019jcyj-msxmX0537)the China Postdoctoral Science Foundation(No.2021M693714)+3 种基金the Chongqing Postdoctoral Science Foundation(No.cstc2020jcyj-bshX0073)the National Natural Science Foundation of China(No.51906181)the Excellent Young and Middle-aged Talent in Universities of Hubei(No.Q20181110)the Graduate Research and Innovation Foundation of Chongqing(No.CYS20013).
文摘Practical applications of data-driven fault detection(FD)are limited by their portability.The costs of model training and validation are extremely high when each system requires a model retrained on its own fault and fault-free data.Therefore,this paper proposes a statistical-based online cross-system FD method to address the problem of model portability.The proposed FD model can be cross-utilized between building chillers with various specifications while it only needs to update the original fault detection model by the normal operation data of the new chiller system,thus saving huge fault experimental costs for the fault detection of new chiller.First,a theoretical basis for the proposed cross-system fault detection method is presented.Then,experiments were conducted on three building chillers with different specifications.Both fault and fault-free data were collected from the three chillers.The development and validation of the proposed cross-system fault detection method are then conducted.Results show that the cross-system fault detection models perform well when used with different chillers.For instance,when the fault detection model of system#1 was cross-utilized to system#2,the detection accuracies of refrigerant leakage,refrigerant overcharge,and reduced evaporator water flow were 99.73%,90.17%,and 96.94%,respectively.Compared with original models,the detection accuracies were improved by 33.78%,84.07%,and 65.56%,respectively.Therefore,the proposed cross-system fault detection method has potential for online application to practical engineering FD.
文摘Thermal adsorption cooling systems have gained significant attention due to their potential for energy savings and eco-environmental impact. An analytic investigation of the heat transfer inside an adsorption chiller with various bed silica gel-water pairs is presented. A comprehensive model has been designed to accurately predict the correlation between the overall performance of the proposed chiller system and the functional and structural condition of the building. This model takes into account various factors such as temperature, humidity, and air quality to provide a detailed analysis of the system’s efficiency. At least 20 collectors consisting of a 34.4 m area (each) with a full-cycle time of 480 seconds are essential to improper run conditions. It is necessary to adjust the optimum cycle time for optimal performance. During the investigation, the base condition shows that the cooling capacity is 14 kw, 0.6 COPcycle, and 0.35 COPsolar at noon. Also, conduct a thorough investigation into the chiller’s performance under varying cooling water supply temperatures and various chilled water flow rates.
文摘A dynamic model is presented for a chiller working with a composite adsorbent(silica activated carbon/CaCl2)–water pair in a solar-biomass cooling installation.The main objective is determining a link between two possible evaporator configurations and the refrigerator’s performances.The two considered evaporators work at different pressure levels.The related time evolution profiles of temperature,pressure and water content are studied.Moreover,the effects of hot water inlet temperature and cooling water inlet temperature on the specific cooling capacity(SCP)and coefficient of performance(COP)are predicted by means of numerical simulations.The results show that an increase in the temperature of hot water and a decrease in the temperature of the cooling water allow an increase in COP and SCP.In particular,for a hot water inlet temperature of 85°C and a cooling water inlet temperature of 40°C,the COP and Qev are 0.67 and 4.3 kW,respectively.
文摘This paper proposes a modified golden jackal optimization(IGJO)algorithm to solve the OCL(which stands for optimal cooling load)problem to minimize energy consumption.In this algorithm,many tools have been developed,such as numerical visualization,local field method,competitive selectionmethod,and iterative strategy.The IGJO algorithm is used to improve the research capabilities of the algorithm in terms of global tuning and rotation speed.In order to fully utilize the effectiveness of the proposed algorithm,three famous examples of OCL problems in basic ventilation systems were studied and compared with some previously published works.The results show that the IGJO algorithm can find solutions equal to or better than other methods.Underpinning these studies is the need to reduce energy consumption in air conditioning systems,which is a critical business and environmental decision.The Optimal Chiller Load(OCL)problem is well-known in the industry.It is the best method of operation for the refrigeration plant to satisfy the requirement of cooling.In order to solve the OCL problem,an improved Golden Jackal optimization algorithm(IGJO)was proposed.The IGJO algorithm consists of a number of parts to improve the global optimization and rotation speed.These studies are intended to address more effectively the issue of OCL,which results in energy savings in air-conditioning systems.The performance of the proposed IGJO algorithm is evaluated,and the results are compared with the results of three known OCL problems in the ventilation system.The results indicate that the IGJO method has the same or better optimization ability as other methods and can improve the energy efficiency of the system’s cold air.
文摘Use of district heating and cooling systems has many environmental advantages compared to individual heating and cooling. Recent advances in solar energy technologies for heat and power generation have reduced their cost and promoted their use instead of fossil fuels. Solar-PV energy for electricity generation and solar thermal energy for hot water production are broadly used today. Solar energy resources in the Mediterranean region are abundant while space cooling in buildings is required when solar irradiance is high. The possibility of using solar energy for fuelling water chillers providing cold water in district cooling systems in the Mediterranean basin has been investigated. Existing literature and studies concerning the use of district cooling systems globally as well as the energy sources used in them have been examined. Solar-PV energy combined with compression chillers and solar thermal energy combined with thermally driven chillers can be used for cold water production. Their overall efficiencies, converting solar energy to cold water, vary between 22% and 56% compared with 45% for compression chillers using grid electricity. It is concluded that various solar energy technologies could be used with different types of water chillers for fuelling district cooling networks in the future in the Mediterranean region.
基金supported by two Ministry of Education(MoE)Singapore Tier 1 research grants under grant numbers R-296-000-208-133 and R-296-000-241-114.
文摘Computer-empowered detection of possible faults for Heating,Ventilation and Air-Conditioning(HVAC)subsystems,e.g.,chillers,is one of the most important applications in Artificial Intelligence(AI)integrated Internet of Things(IoT).The cyber-physical system greatly enhances the safety and security of the working facilities,reducing time,saving energy and protecting humans’health.Under the current trends of smart building design and energy management optimization,Automated Fault Detection and Diagnosis(AFDD)of chillers integrated with IoT is highly demanded.Recent studies show that standard machine learning techniques,such as Principal Component Analysis(PCA),Support Vector Machine(SVM)and tree-structure-based algorithms,are useful in capturing various chiller faults with high accuracy rates.With the fast development of deep learning technology,Convolutional Neural Networks(CNNs)have been widely and successfully applied to various fields.However,for chiller AFDD,few existing works are adopting CNN and its extensions in the feature extraction and classification processes.In this study,we propose to perform chiller FDD using a CNN-based approach.The proposed approach has two distinct advantages over existing machine learning-based chiller AFDD methods.First,the CNN-based approach does not require the feature selection/extraction process.Since CNN is reputable with its feature extraction capability,the feature extraction and classification processes are merged,leading to a more neat AFDD framework compared to traditional approaches.Second,the classification accuracy is significantly improved compared to traditional methods using the CNN-based approach.
基金supported by the doctoral research initiation fund of Linyi University(Grant No.:204-40618051,Zhang,B.,http://www.lyu.edu.cn/).
文摘The relationship among the working temperature,pressure and current density of a Solid oxide fuel cell(SOFC)and its output power and efficiency are analyzed in the framework of a theoretical model able to provide,among other things,the volt ampere characteristic curve.In particular,following the principle of temperature matching and cascade utilization,we consider a gas turbine(GT)and a LiBr absorption chiller to recycle the high-grade exhaust heat produced by the considered SOFC.This distributed total energy system is set up with the intent to meet typical needs of buildings for cooling,heating and power(CCHP).The total power generated by the considered SOFC and gas turbine is about 222 kW and the total power generation efficiency by low heat value of fuel(LHV)is 63.7%.In the CCHP system,the high temperature exhaust of GT is further used to drive LiBr absorption unit,which can produce about 34.8 kW cooling capacity or 84.5 kW of heat(the total energy utilization 78.03%).
文摘A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.
文摘Gas turbine (GT) power plants operating in arid climates suffer a decrease in output power during the hot summer months because of the high specific volume of air drawn by the compressor. Cooling the air intake to the compressor has been widely used to mitigate this shortcoming. Energy and exergy analysis of a GT Brayton cycle coupled to a refrigeration air cooling unit shows a promise for increasing the output power with a little decrease in thermal efficiency. A thermo-economics algorithm is developed to estimate the economic feasibility of the cooling system. The analysis is applied to an open cycle, HITACHI-FS7001B GT plant at the industrial city of Yanbu (Latitude 24o 05” N and longitude 38o E) by the Red Sea in the Kingdom of Saudi Arabia. Result show that the enhancement in output power depends on the degree of chilling the air intake to the compressor (a 12 - 22 K decrease is achieved). For this case study, maximum power gain ratio (PGR) is 15.46% (average of 12.25%), at an insignificant decrease in thermal efficiency. The second law analysis show that the exergetic power gain ratio drops to an average 8.5%. The cost of adding the air cooling system is also investigated and a cost function is derived that incorporates time-dependent meteorological data, operation characteristics of the GT and the air intake cooling system and other relevant parameters such as interest rate, lifetime, and operation and maintenance costs. The profit of adding the air cooling system is calculated for different electricity tariff.
文摘To a kind of centrifugal water chiller with R22 and about 1 745 kW of cooling capacity,a heat exchanger was added between the outlet of compressor and original condenser to get part of or all the condensing heat.Condensing heat can be recovered by compound condensing method,which adopts air-cooling model +water-cooling model or water-cooling model +water-cooling model at the condensing side of the system.By exergy analysis and experiment research on compound condensing heat recovery of centrifugal chiller,the results are obtained that the capability of the whole system increases,the energy efficiency ratio(EER)becomes 3.2~5.0 from 2.2~3.4,which implies the EER increases about 1.0~1.5,the exergy efficiency increases about 10%,and the chiller runs more stably after reformation.
文摘A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship between pressure, temperature and concentration of the lithium bromide solution have been analyzed. The result obtained indicates that the pressure of the high pressure generator and the temperature of the exhausted smoke are the most sensitive parameters. It is also found that the transition time from a full load to a part load condition is quite long, and part load relative cooling capacity is almost near the intermittent running time ratio and oil consumption ratio.
基金Project Supported by National Natural Science Foundation of China(51777193).
文摘The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will greatly deepen the coupling of the electricity-gas integrated energy system,improve the flexibility and safety of the operation of the power system,and bring a deal of benefits to the power system.On this background,an optimal dispatch model of RIES combined cold,heat,gas and electricity with SOP is proposed.Firstly,RIES architecture with SOP and P2G is designed and its mathematical model also is built.Secondly,on the basis of considering the optimal scheduling of combined cold,heat,gas and electricity,the optimal scheduling model for RIES was established.After that,the original model is transformed into a mixed-integer second-order cone programming model by using linearization and second-order cone relaxation techniques,and the CPLEX solver is invoked to solve the optimization problem.Finally,the modified IEEE 33-bus systemis used to analyze the benefits of SOP,P2G technology and lithium bromide absorption chillers in reducing systemnetwork loss and cost,as well as improving the system’s ability to absorb wind and solar and operating safety.
文摘Hybrid<span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">chiller plants (HCPs)</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">using multiple chillers and different energy sources</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">are highly recommended in several energy applications in non-residential buildings such as hospitals and hotels. Time of use and cooling load profiles are significant factors that should be carefully considered either in chiller plant design or in chiller sequencing operation. This article aims to present an operation planning of HCP which consists of both electric and non-electric chillers. Four operational strategies are proposed and solved to compare their coefficients of performance and economics of running costs. A typical hotel building located on the Nile river in Egypt is selected to perform the current thermal and economic case study. The total cooling load profile of this hotel building is 4000 refrigeration tonnage (TR), which </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">simulated to optimize chiller sequence of operation and to select optimal design conditions of both numbers for electric and non-electric chillers used in HCP. The results of this comparative study for running cost are defined using various design configurations with different several chiller sequences available for each configuration. Then, the results of COPs, and operational running cost and initial cost are presented in this article also. The comparison aims to find the optimal design and operational sequencing for HCPs on thermal basis and economic analysis which were attached in this article. Recommendations and suggestions for future work are attached at the end of this article.</span></span></span>
文摘Cold energy generation systems must be improved to prevent catastrophic climate change. In this study, we focused on an absorption chiller cycle with HFC-134a and an ionic liquid pair as the refrigerant and absorbent, respectively. It was expected that this absorption chiller cycle could generate cold heat below 0°C. Two liquids were selected and their absorption equilibrium with this pair was evaluated for the absorption chiller cycle. We measured the adsorbed amount at equilibrium with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][Tf2N] and N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide [N1113][Tf2N]. The experimental results were reproduced using the non-random two liquid (NRTL) model. This analysis model corresponded well in terms of the amount of adsorption at equilibrium with the experimental results. A Duhring diagram was also generated the NRTL model, and the absorption cycle characteristics as a function of temperature were determined. The absorption chiller cycle obtained cold heat at 10°C with a regeneration temperature of 70°C in addition to generating cold heat below 0°C.
文摘Large amounts of waste heat below 100oC from the industrial sector are re-leased into the atmosphere. It has been suggested that energy system efficiency can be increased with adsorption chillers. However, the cooling power and coefficient of performance (COP) of conventional adsorption chillers significantly decrease with the desorption temperature. In this paper, we proposed a mechanical booster pump (MBP)-assisted adsorption chiller cycle, and evaluated its performances. In the cycle, a MBP was incorporated into a zeolite-water-type adsorption chiller for facilitating water vapor transportation between an adsorber and an evaporator/condenser. We have experimentally studied the effect of the input electrical power of MBP on the performances of adsorption chiller cycle. It has been demonstrated that the heat input achieved by using MBP at the desorption temperature of 50oC was 1.6 times higher than that of without MBP at the desorption temperature of 60oC. And the increase of pump power was found to be effective in increasing the heat input. Therefore, it was confirmed that the operation range of desorption temperature, which can be generated by using the waste heat, was extended and the cooling power was increased directly by using MBP.
文摘The research was aimed at providing water for cooling recycled cyclohexane in polyethylene plant to 15°C. This research could be redounding to the benefit of polyethylene plants that are using solution based polymerization technique. A chiller unit of 630 T, which has compressor power input of 378.33 kW and can provide chilled water capable of cooling recycle cyclohexane to 15°C, was designed using Aspen Hysys version 7.1. Four different refrigerants were tested to know the best fit refrigerant for the design and the best among them was R134a. The designed chiller has a coefficient of performance of 6.3 and a capacity greater than that of the defective chiller (550 TR). Unlike the defective chiller, with the increased cooling capacity and corresponding increase in compressor power from 296 kW to 378.6 kW, it could discharge chilled water capable of cooling recycle cyclohexane from 38°C to 15°C without tripping of the unit. With this design, ethylene absorption rate could increase to 40 T/h. Evaporator and condenser were designed and duties were 2166.39 KJ/sec and 2544.72 KJ/sec respectively. A thermostatic expansion valve with flow coefficient of 46.17 gpm was designed. The designed suction and discharge pressure were 414 kpa and 1053 kpa respectively while condenser temperature of 40°C was used for the design. The cooling of recycle cyclohexane from 38°C to 15°C using the chilled water supplied by the designed chiller was simulated using Aspen Hysys.
文摘In this paper, the model of chiller power consumption is built by using the regression analysis. While taking the parameters from the operation data of chiller into consideration simultaneously, i.e. Partial Load Ratio (PLR), chilled water supply temperature and cooling water return temperature, the prediction results are quite accurate, and its accuracy reaches over 99% in short-term prediction when compared with the actual power consumption. This method can be used to validate the benefits of the chiller’s energy saving method. The validation items include: the effect of water flow change on chiller’s performance while multiple chillers operate in parallel;the power consumption analysis of centrifugal chiller operating with or without frequency conversion;as well as the discussion on whether the cleaning of condenser coil can improve the Coefficient of Performance (COP) of chiller or not. The case study results show that, while multiple chillers operate in parallel, the water flow change has limited effect on the performance of chiller. However, about 36% electricity can be saved averagely when the chiller controls the frequency of electric power source at partial load, and the cleaning of condenser coil can increase the COP by 3.08%.