36 results
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2. Heat Index Estimation of Ventilating Air-Conditioning Heating Area Considering Thermal Comfort.
- Author
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Zhibin Luo
- Subjects
- *
THERMAL comfort , *AIR conditioning , *ENERGY conservation , *HUMAN comfort , *ENERGY consumption , *THERMAL insulation , *SOLAR heating - Abstract
The heat metering of heating is a main link in energy conservation of ventilating airconditioning (VAC) heating. It is of great practical significance to study the heat metering of heating. However, not many scholars have estimated the heat index based on building heating area, in the light of thermal comfort. Therefore, this paper estimates the heat index of VAC heating area considering thermal comfort. Firstly, we analyzed the various factors affecting human thermal comfort. Then, four environmental factors were selected, namely, indoor air temperature, relative air humidity, mean radiation temperature of envelope surface on human body, and indoor vertical air error. In addition, we selected suitable thermal comfort indices to predict and assess the thermal environment under indoor VAC heating. After that, we analyzed the indoor heat flow under VAC heating, examined the components of energy consumption of indoor VAC heating, and estimated the heat index of VAC heating area. Next, a mathematical model was constructed for heat metering, according to the heat consumption of the building VAC, and the composition of the heat consumption of occupants. Experimental results verify the effectiveness of the proposed thermal metering model. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
3. Control strategy for dynamic operation of multiple chillers under random load constraints.
- Author
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Liu, Xuefeng, Huang, Bin, and Zheng, Yulan
- Subjects
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COOLING systems , *MARKOV processes , *AIR conditioning , *IMPACT loads , *ENERGY consumption , *PREDICTION models - Abstract
Under the influence of building load stochasticity and thermal inertia of central air conditioning system, the lag of control strategy makes it difficult for the cooling source system to meet the cooling demand of users in real time, which affects the operational energy efficiency ratio of the cooling source system. In this regard, this paper proposes a chiller dynamic optimization method based on Markov chain model predictive control algorithm, which studies the optimization of parallel operation characteristics of multiple chillers on the basis of correcting the occurrence of small probability events and avoiding frequent chiller starts and stops, reveals the prediction law of hourly load distribution of the future air conditioning system, explores the balance point between the prediction time of building load and the calculation time of chiller control strategy, provides a theoretical basis and reference for determining the time limit of the optimal calculation and the output of the optimal control strategy. The study provides a theoretical basis and reference for determining the time limit of the optimal calculation and the output of the optimal control strategy. It is found that the optimal control strategy not only has good optimization effect, but also the confidence is significantly increased by 56.7%. • Markov chain predictions of building loads are time-bound. • Consider the impact of the randomness of the load time distribution. • The model takes into account the occurrence of small probability events. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. Realisable 10-year reductions in European energy consumption for air conditioning.
- Author
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Hitchin, Roger, Pout, Christine, and Butler, David
- Subjects
- *
ENERGY consumption , *AIR conditioning , *ENERGY conservation , *ENERGY policy , *COOLING loads (Mechanical engineering) - Abstract
This paper summarises the results of a study to identify and quantify the potential impact of measures and policies to reduce the energy consumption of air conditioning in European countries over a 10-year period. The market penetration of air conditioning in Europe has increased steadily over several decades. On a “business as usual” basis, its energy consumption would increase by over 50% by 2020. Measures to restrict this increase are therefore important, but the savings potential straddles several overlapping areas which are subject to different constraints including those imposed by the replacement rates of systems and products, and the refurbishment rates of existing buildings. This work reported in this paper is based on the use of information from a variety of sources in a highly disaggregated model to assess the “realisable” savings over a 10-year period, taking into account relevant constraints. The paper summarises results at a European level, focussing on those cases that generate the greatest realisable savings. Savings are possible in three areas: improved equipment and system efficiency, reduced cooling loads, and more effective operation. The cases that offer the largest savings provide the basis for recommendations for policy measures, often using existing policy instruments. In addition, areas where further work is needed are identified. More detailed results and information about the study and additional recommendations can be found at http://www.bre.co.uk/searchresults.jsp?category=5&q=energy+management [1] . [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
5. Application of Energy Conservation Measures and Their Impact on the Thermal-Energetic Performance of a Building in the Brazilian Amazon Region: A Case Study.
- Author
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Aguilar, Heliana M. C., Galhardo, Marcos A. B., and Pinho, João T.
- Subjects
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ENERGY conservation , *HEAT , *CONSTRUCTION - Abstract
This paper focuses on the thermal and energetic behavior of a building located in the Brazilian Amazon Region, a region climatically characterized by elevated temperatures and high humidity levels, where achieving adequate thermal comfort demands a high-energy consumption due to the use of air-conditioning systems. Therefore, different energy conservation measures (ECMs) need to be evaluated to reduce the thermal load for cooling. The use of a thermal insulation material on the west wall and on the roof, and a photovoltaic (PV) system integrated as an architectural element and adapted to the roof of the building are considered. The building is simulated with the software energyplus, with its thermal behavior and energy consumption analyzed for an entire year and for a chosen design day, defined with data measured by a weather station installed close to the building. According to the evaluations carried out, it is determined that the ECMs have a direct and major influence on the reduction of the thermal load for cooling, on the reduction of the effects caused by radiation with the shading on the eaves, and the reduction of the transmittance on the surfaces that were modified in the study. In terms of energy consumption and economic feasibility, the ECMs reach an annual energy saving percentage of 74% for the building chosen as the case study, and the solutions adopted provide the return of the financial investment, proving suitable for energy saving and economically viable for regions with similar climatic characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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6. Study on energy-saving design and operation of hospital purification air conditioning system.
- Author
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Chen, Yunyu
- Subjects
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AIR conditioning , *AIR purification , *ENERGY conservation , *ENERGY consumption , *HOSPITALS - Abstract
In order to ensure the cleanliness of operating room, clean air conditioners are installed in the clean operation departments in hospitals in China. Purification air conditioning system is an air conditioning system with a special function that ensures the cleanliness of the operating room and the required temperature and humidity in the operating room to avoid infection. This paper took the energy-saving design of the clean air-conditioning system of the clean operation department of the First Affiliated Hospital of Wenzhou Medical College, Zhejiang, China, as an example to illustrate the energy-saving methods such as layout optimization, air-conditioning division, secondary return air setting and operation mode adjustment. The energy consumption of primary return air technology and secondary return air technology was calculated. The results showed that energy-saving design could save nearly one-third of energy, improve the level of air-conditioning operation and management, reduce costs, and improve resource utilization, which is of great significance to social development. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
7. Energy-Saving Benefits of Adiabatic Humidification in the Air Conditioning Systems of Semiconductor Cleanrooms.
- Author
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Min-Suk Jo, Jang-Hoon Shin, Won-Jun Kim, and Jae-Weon Jeong
- Subjects
- *
VENTILATION , *HEATING , *AIR conditioning , *HUMIDITY control , *ENERGY conservation , *ENERGY consumption - Abstract
This paper aimed to evaluate the applicability of adiabatic humidification in the heating, ventilation, and air conditioning (HVAC) systems of semiconductor cleanrooms. Accurate temperature and humidity control are essential in semiconductor cleanrooms and high energy consumption steam humidification is commonly used. Therefore, we propose an adiabatic humidification system employing a pressurized water atomizer to reduce the energy consumption. The annual energy consumption of three different HVAC systems were analyzed to evaluate the applicability of adiabatic humidification. The studied cases were as follows: (1) CASE 1: a make-up air unit (MAU) with a steam humidifier, a dry cooling coil (DCC), and a fan filter unit (FFU); (2) CASE 2: a MAU with the pressurized water atomizer, a DCC, and a FFU; and (3) CASE 3: a MAU, a DCC, and a FFU, and the pressurized water atomizer installed in the return duct. The energy saving potential of adiabatic humidification over steam humidification has been proved, with savings of 8% and 23% in CASE 2 and CASE 3 compared to CASE 1, respectively. Furthermore, the pressurized water atomizer installed in the return duct exhibits greater energy saving effect than when installed in the MAU. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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8. Relationship between Energy Wheel Speed and Effectiveness and Its Transient Response, Part I:Mathematical Development of the Characteristic Time Constants and Their Relationship with Effectiveness.
- Author
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Abe, Oyetope O., Besant, Robert W., Simonson, Carey J., and Wei Shang
- Subjects
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MATHEMATICAL models , *ELECTRIC machinery rotors , *COST effectiveness , *FEASIBILITY studies , *ENERGY conservation , *ENERGY consumption , *HEATING & ventilation industry , *AIR conditioning , *ARCHITECTURE & energy conservation - Abstract
Testing energy wheels to determine their effectiveness under steady-state operating conditions has proved to be difficult, time consuming, and costly if accurate results are to be obtained. This paper investigates the theoretical feasibility of using transient response tests on a stationary energy wheel to determine the effectiveness of the same energy wheel rotating at a specified rate. In this paper mathematical models for predicting first the characteristic time constants and, second, the effectiveness of an energy wheel are developed using only the expected transient response functions for the wheel. These time constants for sensible and latent (phase change) energy transient response are directly related to the corresponding sensible and latent effectiveness of an energy wheel operating at steady state at a specified rotor speed. It is concluded that it is feasible to use a simple transient parallel flow test on a stationary energy wheel and use these data to predict the sensible and latent effectiveness of the same energy wheel operating at a known speed. Furthermore, the energy wheel and HVAC designer can use the equations developed for the time constants and the effectiveness to provide guidance toward better performance. [ABSTRACT FROM AUTHOR]
- Published
- 2006
9. A novel compressed air energy storage (CAES) system combined with pre-cooler and using low grade waste heat as heat source.
- Author
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Chen, Long-Xiang, Hu, Peng, Sheng, Chun-Chen, and Xie, Mei-Na
- Subjects
- *
ENERGY consumption , *COMPRESSED air energy storage , *ENERGY conservation , *WASTE heat , *AIR conditioning - Abstract
Decreasing fuel consumption in compressed air energy storage (CAES) system is a general trend for conserving energy and protecting the environment. Waste heat recovery is an interesting technology to compact energy storage system. However, CAES system has a low thermal efficiency when using low grade waste heat as heat source directly. In this paper, an integrated energy system consisting of a CAES system and a precooling system (PC-CAES) is proposed to decrease the energy consumption of compression train in the charging process, and enhance the round trip efficiency (RTE) of the system. Air conditioner is utilized as pre-cooler to precool the inlet air of compressor and five refrigerants are investigated. The thermodynamic analysis is performed by using steady-state mathematical model and thermodynamic laws. The calculation results show that the RTE of the proposed PC-CAES system is improved by more than 3% than that of the conventional CAES system and more economical than CAES with additional compression stages. Meanwhile, a parametric analysis is also carried out to evaluate the effects of several key parameters on the system performance of two CAES systems. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
10. Analysis of an energy efficient building design through data mining approach
- Author
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Kim, Hyunjoo, Stumpf, Annette, and Kim, Wooyoung
- Subjects
- *
CONSTRUCTION , *ENERGY consumption , *ENERGY conservation , *DATA mining , *CONTRACTORS , *BUILDING designers , *VENTILATION , *AIR conditioning , *CIVIL engineers - Abstract
Abstract: Incorporating energy efficiency and sustainable green design features into new/existing buildings has become a top priority in recent years for building owners, designers, contractors, and facility managers. This paper intends to address why delivery of an energy efficient building is not just the result of applying one or more isolated technologies. Rather, it can best be obtained using an integrated whole building process throughout the entire project development process, which leads building designers to generate a large amount of data during energy simulations. The authors observed that even a simple energy modeling run generated pages of data with many different variables. The volumes of energy modeling data clearly overwhelm traditional data analysis methods such as spreadsheets and ad-hoc queries with so many factors to be considered. An integrated or whole building design process involves studies of the energy-related impacts and interactions of all building components, including the building location, envelope (walls, windows, doors, and roof), heating, ventilation and air conditioning (HVAC) system, lighting, controls, and equipment, which shows why it is so difficult to find the correlation between different systems. The objective of this research is to develop an energy efficient building design process using data mining technology which can help project teams discover important patterns to improve the building design. This paper utilizes the data mining technology to extract interrelationships and patterns of interest from a large dataset. Case study revealed that data mining based energy modeling help project teams discover useful patterns to improve the energy efficiency of building design during the design phase. The method developed during this research could be used to guide designers and engineers through the process of completing an early design energy analysis based on energy simulation models. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
11. Applying water cooled air conditioners in residential buildings in Hong Kong
- Author
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Chen, Hua, Lee, W.L., and Yik, F.W.H.
- Subjects
- *
AIR conditioning , *COOLING loads (Mechanical engineering) , *ENERGY conservation , *ENERGY consumption , *POWER resources , *ELECTRIC power consumption - Abstract
Abstract: The objective of this study is to conduct a realistic prediction of the potential energy saving for using water cooled air conditioners in residential buildings in Hong Kong. A split type air conditioner with air cooled (AAC) and water cooled (WAC) options was set up for experimental study at different indoor and outdoor conditions. The cooling output, power consumption and coefficient of performance (COP) of the two options were measured and calculated for comparison. The experimental results showed that the COP of the WAC is, on average, 17.4% higher than that of the AAC. The results were used to validate the mathematical models formulated for predicting the performance of WACs and AACs at different operating conditions and load characteristics. While the development of the mathematical models for WACs was reported in an earlier paper, this paper focuses on the experimental works for the AAC. The mathematical models were further used to predict the potential energy saving for application of WACs in residential buildings in Hong Kong. The predictions were based on actual building developments and realistic operating characteristics. The overall energy savings were estimated to be around 8.7% of the total electricity consumption for residential buildings in Hong Kong. Wider use of WACs in subtropical cities is, therefore, recommended. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
12. An Optimization-Based Approach for Facility Energy Management with Uncertainties.
- Author
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Jun Xu, Luh, Peter B., Jerdonek, Ron, Blankson, William E., and Shaikh, Khalil
- Subjects
- *
FACILITY management , *ENERGY conservation , *ENERGY consumption , *COST control , *HEATING , *VENTILATION , *AIR conditioning , *DIGITAL control systems - Abstract
Effective energy management for facilities is becoming increasingly important in view of rising energy costs, the government mandate on reduction of energy consumption, and human comfort requirements. This paper presents a daily energy management formulation and the corresponding solution methodology for HVAC systems. The problem is to minimize the energy and demand costs through control of HVAC units while satisfying human comfort, system dynamics, load limit constraints, and other requirements. The problem is difficult in view of the facts that the system is nonlinear, time-varying, building-dependent, and uncertain and that the direct control of a large number of HVAC components is difficult. In this paper, HVAC setpoints are control variables developed on top of a direct digital control (DDC) system. A method that combines Lagrangian relaxation, neural networks, stochastic dynamic programming, and heuristics is developed to predict system dynamics and uncontrollable load and to optimize the setpoints. Numerical testing and prototype implementation results show that our method can effectively reduce total costs, manage uncertainties, and shed the load; is computationally efficient; and is significantly better than existing methods. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
13. Applicability and energy efficiency of temperature and humidity independent control systems based on dual cooling sources.
- Author
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Chen, Tingting, Yin, Yonggao, and Zhang, Xiaosong
- Subjects
- *
ENERGY consumption , *ENERGY conservation , *AIR conditioning , *VAPOR compression cycle , *CHILLERS (Refrigeration) , *MATHEMATICAL optimization - Abstract
Temperature and humidity independent control (THIC) systems demonstrate promising energy-saving potential compared with the conventional air conditioning systems. One type of THIC systems is proposed to use dual cooling sources with different temperatures since they could be produced easily by traditional vapor compression refrigeration chillers. This paper investigates the applicable condition of the THIC system based on dual cooling sources (DCSTHIC system). It is found that the DCSTHIC system has limited conditions (such as scopes of the heat moisture ratio and the fresh air rate) when applied, otherwise the indoor air temperature and humidity can’t be fulfilled, and further available scope of the heat moisture ratio realized by the DCSTHIC system is disclosed for air conditioned spaces. The minimum realized heat moisture ratio depends on the temperature of low-temperature cooling sources ( t LCS ). A parametric study is also conducted to analyze effects on the energy efficiency of DCSTHIC systems. These parameters include the heat moisture ratio ( ε ) and temperatures of dual cooling sources. Results show that DCSTHIC systems show more significant energy-saving potential in the air conditioned spaces with higher ε . The system COP improvement ranges from 3.1% to 17.5% compared with conventional air conditioning systems when the heat moisture ratio changes from 8000 kJ/kg to 15,000 kJ/kg. This study helps to guide the design and optimization of DCSTHIC systems. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
14. Development and application of a simple BEMS to measure energy consumption of buildings.
- Author
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Yuan, J., Farnham, C., and Emura, K.
- Subjects
- *
HOME energy use , *ENERGY management , *ELECTRIC power in dwellings , *HOME air conditioning , *CARBON dioxide mitigation , *ENERGY conservation - Abstract
This paper shows development of a simple, cheap “Building Energy Management System” (BEMS) to monitor energy consumption, and an application to measure energy consumption, including electricity and gas consumption in buildings. The system uses current transformers to measure electric consumption at each distribution box. Web cameras monitor lighting in each room, as well as air conditioning status by recognizing the movement of a ribbon at the outlet. Web cameras can also monitor gas consumption at the meter through character recognition. The data is sent via network to a computer for monitoring and analysis. As an example, key components of this BEMS were tested to measure building energy consumption of Osaka City University Sugimoto Campus in Japan for a period of 2 years (2013, 2014). The electric consumption of campus as well as the electric and gas consumption for air conditioning use was measured. Web cameras were installed in several rooms in one section of the campus to record lighting and air conditioning use data. The data was analyzed to reveal a correlation between hourly outdoor temperature and hourly electric consumption, with a stronger correlation between hourly outdoor temperature and hourly electric consumption for air conditioning. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
15. Energy Saving Using Mixed Air in Rooms Conditioned by Chilled Ceiling Displacement Ventilation System.
- Author
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Chakroun, W., Ghali, K., and Ghaddar, N.
- Subjects
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ENERGY conservation , *AIR conditioning , *DISPLACEMENT (Mechanics) , *VENTILATION , *AIR quality , *CARBON dioxide , *ENERGY consumption - Abstract
This paper aims to study the impact of introducing the return air concept into rooms conditioned by chilled ceiling displacement ventilation (CC/DV) system to save energy while limiting a time-dependent return fraction based on room load in order to maintain an acceptable air quality in the breathing zone. A transient coupled thermal and contaminant transport model is needed to assess the indoor air quality based on predicted levels of carbon dioxide concentrations in the radiant-cooled space under varying load conditions. For that reason, the Kanaan et al. (2010) contaminant transport model in CC/DV conditioned spaces is extended to transient applications that have substantial wall plumes induced by external loads. Experiments are performed to validate the extended model predictions of air quality expressed in the level of CO2 concentration in spaces conditioned by CC /DV system. Experiments are conducted in a chamber with two external walls in Kuwait Climate. Measurements are recorded in time of the air temperature and carbon dioxide concentration at selected location in the room and are compared with values predicted by the model. The experimental results agreed well with extended contaminant transport model predictions. The maximum errors in predicted CO2 concentrations are less than ± 25ppm in presence of external load. It was also found that the mixing fraction reaching up to 60% resulted in 37% less energy consumption of the system when compared with 100% fresh air CC/DV system. [ABSTRACT FROM AUTHOR]
- Published
- 2011
16. The Identification and Rebound Effect Evaluation of Equipment Energy Efficiency Improvement Policy: A Case Study on Japan's Top Runner Policy.
- Author
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Yu, Dan, Dewancker, Bart, and Qian, Fanyue
- Subjects
- *
ENERGY consumption , *ENERGY conservation , *REDUCTION potential , *AIR conditioning , *CASE studies , *AUTOMOBILE lighting - Abstract
The equipment energy efficiency improvement policy (EEEIP) is one of the important measures of energy conservation and emission reduction in various countries. However, due to the simultaneous implementation of variety policies, the effect of the single policy cannot be clearly reflected. In this paper, a method of identification and evaluation of EEEIP was proposed, and the application was verified by analyzing the example of EEEIP in Japan (Top Runner policy, TRP). Firstly, through the factor decomposition model, this paper studied the energy conservation and emission reduction potential of this policy area in Japan. Then, the TRP was identified by using moving windows and correlation analysis, and the impact of specific equipment in TRP was analyzed. Finally, through the calculation of the rebound effect of the carbon footprint (REC), this paper analyzed the energy consumption and emission reduction effects of TRP in the short-term and whole life cycle. It showed that the policy has a good effect in tertiary industry and transportation, while the effect in residential is poor. For life cycle, the TRP of air conditioning and passenger car can bring better CO2 emission reduction effect, but the emission reduction effect of lighting is basically offset. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
17. Laboratory Testing of Full-Scale In-Duct Gas Air Cleaners.
- Author
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VanOsdell, Douglas W., Rodes, Charles E., and Owen, M. Kathleen
- Subjects
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AIR quality , *AIR conditioning , *AIRTIGHTNESS of buildings , *ENERGY consumption , *ENERGY conservation , *AIR classifiers , *INTERIOR lighting , *HEATING & ventilation industry , *POWER resources - Abstract
Because of their ability to improve building air quality and their potential to reduce energy usage in some climates by allowing more conditioned air recirculation, use of gas contaminant filters in buildings is increasingly considered. Air cleaning is an option under ASHRAE Standard 62 and is required if the outdoor air is poor. New media and processes are becoming available, and their performance needs to be evaluated. Further, evaluation of existing technologies needs to be standardized. Both small-scale and full-scale testing is required, and there is not a standard method for systematic evaluation of commercial full-scale gas-phase air cleaners in a duct. A number of laboratory tests of full-scale gas-phase air filtration equipment (GPAFE) have been conducted at RTI over several years. The methods were developed during ASHRAE and EPA research and refined on later commercial projects. The full scale test method uses a modified ASHRAE Standard 52.2 test rig. This paper presents an overview of fullscale GPAFE testing and discussion of the considerations that go into design of a full-scale test. Selected results of full scale tests are presented. [ABSTRACT FROM AUTHOR]
- Published
- 2006
18. Accuracy Tests for Simulations of VAV Dual- Duct, Single-Zone, Four-Pipe Fan-Coil, and Four-Pipe Induction Air-Handling Systems.
- Author
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G. K. Yuill, J. S. Haberl, and J. S. Caldwell
- Subjects
- *
COMPUTER simulation , *HEATING & ventilation industry , *COOLING loads (Mechanical engineering) , *AIR conditioning , *THERMODYNAMICS , *COMPUTER software , *COMPUTER software developers , *ENERGY conservation , *ENERGY consumption - Abstract
This paper provides a method for verifying the accuracy of computer models that simulate the performance of the airhandling components of four types of heating, ventilating, and air-conditioning systems: the dual fan VAV dual-duct system, the single-zone system, the four-pipe fan coil system, and the four-pipe induction system. To accomplish this, a detailed description of each system and its operating parameters was developed and a set of eight test conditions was generated, consisting of carefully chosen space loads and weather conditions. Each of the systems was simulated at each of the defined conditions. The thermodynamic properties at each point in the system, as well as the heating and cooling coil loads, were calculated. The calculations were then repeated by a second analyst using an independently developed program. The maximum deviation in the total coil loads was 1.8%, and the average of the absolute deviations was 0.4%. These validated results can be used by program developers or users to test the performance of the air-side simulations contained in most building energy analysis computer programs. [ABSTRACT FROM AUTHOR]
- Published
- 2006
19. Energy Performances of Prototype VAV and CAV Systems under Simulated Humid Tropical Climates.
- Author
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Ameen, Ahmadul and Mahmud, Khizir
- Subjects
- *
VARIABLE air volume systems (Air conditioning) , *ENERGY consumption , *AIR conditioning , *OFFICE buildings , *HUMIDITY , *ENERGY conservation , *CLIMATOLOGY , *ENVIRONMENTAL engineering of buildings - Abstract
This paper reports the relative energy consumption of prototype VAV and CAV air-conditioning systems under various load conditions simulating those of a typical office building in humid tropical climates such as Singapore's. Tests were conducted inside two adjoining environmental chambers where space loading was varied from 0.217 to 0.295 kW/m² (68.81 to 93.54 Btu/h ft²) with corresponding sensible heat ratio (SHR) ranging from 0.65 to 0.9. The VAV system consistently consumed less energy compared to the CAV system under constant as well as variable load conditions. The percentage energy saving ranged from 21.97% at 0.217 kW/m² (68.81 Btu/h ft²) to 12.42% at 0.295 kW/m² (93.54 Btu/h ft²) under constant loading, and it decreased with increased space loading. The experiments measured moderate energy savings under the experimental conditions that are assumed to be the typical load condition in Singapore. Because the implementation costs are significant, it appears that a VAV system has marginal economic benefit in Singapore. [ABSTRACT FROM AUTHOR]
- Published
- 2005
20. Field Performance Assessment of VAV Control Systems to Determine the Longevity of Recommissioning.
- Author
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Klaczek, Wayne, Fleming, Pat, Ackerman, Mark, and Fleck, Brian
- Subjects
- *
VARIABLE air volume systems (Air conditioning) , *DIGITAL control systems , *FIELD research , *INDOOR air pollution , *ENERGY consumption , *ENERGY conservation , *HEATING , *REFRIGERATION & refrigerating machinery , *AIR conditioning , *PAYBACK periods - Abstract
This paper summarizes key results of ASHRAE Research Project RP-1137, which sought to quantify the benefits and longevity of the recommissioning process on variable air volume (VAV) systems that incorporate direct digital control (DDC). Field testing was completed in three diverse facilities over a period of up to two years, generating three data trends. General performance indicators were compared using the data collected prior to commissioning, immediately after commissioning, and long after commissioning was completed (a minimum of six months later). Key performance indicators included: improved DDC system accuracy, indoor air quality (IAQ), and energy efficiency/savings. It is important to note that RP-1137 did not seek to determine all possible recommissioning benefits, only to quantify some of the benefits using field testing and laboratory experiments. This research indicates that commissioning is beneficial and that system recommissioning is typically justified within a time period similar to the capital payback period. Conclusions are limited to the time period specified: thus, the longevity of recommissioning is at least equal to the payback period but cannot be predicted beyond this within RP-1137. [ABSTRACT FROM AUTHOR]
- Published
- 2005
21. Optimal control of combined air conditioning system with variable refrigerant flow and variable air volume for energy saving.
- Author
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Zhu, Yonghua, Jin, Xinqiao, Fang, Xing, and Du, Zhimin
- Subjects
- *
OPTIMAL control theory , *ENERGY conservation , *AIR conditioning , *ENERGY consumption , *VENTILATION , *TEMPERATURE effect , *LEAST squares - Abstract
Abstract: An optimal control strategy for minimizing the energy consumption of variable refrigerant flow (VRF) and variable air volume (VAV) combined air conditioning systems was presented. The combined system was proposed to take advantages of VAV systems to solve the ventilation problem of VRF systems. The VAV part consists of an outdoor air processing unit and air supply and distribution devices. To determine set-point of the optimal control variable, i.e. outdoor air supply temperature, this paper proposed an optimal control strategy based on adaptive predictive model and recursive least squares estimation technique. Typical days in summer and winter were selected to test the strategy. Results indicated that the optimal control strategy reduces energy consumption of the combined system by 32.17% in summer and 2.47% in winter. The overall energy efficiency is enlarged by 12.18% in summer and 3.37% in winter, compared with the benchmark operation strategy. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
22. Development of temperature and humidity independent control (THIC) air-conditioning systems in China—A review.
- Author
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Zhang, Tao, Liu, Xiaohua, and Jiang, Yi
- Subjects
- *
AIR conditioning , *HUMIDITY control , *TEMPERATURE control , *ENERGY conservation , *RESEARCH & development , *ENERGY consumption - Abstract
Abstract: A temperature and humidity independent control (THIC) system is a way to regulate indoor temperature and humidity separately through different approaches. Because of this distinction, THIC air-conditioning systems can satisfy the adjustment requirements of indoor temperature and humidity better than conventional systems can, and they show significant potential for energy conservation. In the past ten years, rapid improvements have been achieved in both theoretical research and the development of equipment related to THIC systems, and more and more applications are being put into use in non-residential buildings in China. This paper focuses on the development of THIC systems in China and reviews recent achievements and progress related to the main devices used for temperature and humidity control, including outdoor air handling dehumidification processors, sensible heat terminals, and high-temperature cooling sources. The energy performance of THIC systems is examined based on an analysis of established applications. Both the performance of key components and the energy consumption of entire systems indicate that THIC systems result in significant improvements in energy performance compared to conventional systems. Developmental trends and recommendations about design methodology, ways to improve the performance of handling devices, and feedback from applications of THIC systems are also discussed. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
23. Temperature control of the four-zone split inverter air conditioners using LMI expression based on LQR for mixed H 2/H ∞.
- Author
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Yang, YauBin, Wu, Min-Der, and Chang, Yu-Choung
- Subjects
- *
TEMPERATURE control , *AIR conditioning , *ALGORITHMS , *ENERGY conservation , *ENERGY consumption , *COMPRESSORS , *LINEAR matrix inequalities , *TRANSFER functions , *HYDROGEN - Abstract
Highlights: [•] The optimal control gains were obtained from the linear matrix inequalities with mixed H 2 and H ∞ control algorithm. [•] The proposed method guaranteed convergence, stability, and provided a way for disturbance rejection and energy savings. [•] The coupling effects occurred among the compressor speed, opening degrees, evaporator temperatures and superheats. [•] The system identification and thermal dynamics equations could obtain the inner and outer loop transfer functions. [•] All simulations in this paper were in discrete time domain. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
24. Implementation conditions for energy saving technologies and practices in office buildings: Part 2. Double glazing windows, heating and air-conditioning
- Author
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Tsagarakis, Konstantinos P., Karyotakis, Konstantinos, and Zografakis, Nikolaos
- Subjects
- *
ENERGY conservation , *OFFICE building energy consumption , *HEATING , *AIR conditioning , *ENERGY policy , *ENERGY consumption , *BUSINESS enterprises - Abstract
Abstract: This paper provides a review of the energy saving policies and technologies on double glazing windows, central heating and air conditioning in office buildings. After which results of a face to face survey of 685 companies’ managers are presented, which give insights into the facts that have influenced them to invest in the installation of double glazing windows, installation of thermostatic regulators, inverter air-conditioning technologies and on proper maintenance and filter cleaning of the air-conditioning units. Finally, their willingness to install such technologies after a technico-economic information session is elicited. The results show that among factors that make managers have a more energy saving profile are ownership, awareness status, recent establishment of the company and companies dealing with trade. Among factors that influence willingness to undertake specific energy efficient measures for heating and cooling appear to be ownership, recently established companies, companies dealing with services, companies with a high number of personnel, and companies with high ratios of electricity bill per annual turnover. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
25. An Influence of Air Volume Flow Rate and Temperature Set Point on Performance of Inverter Split-Type Air-Conditioner.
- Author
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Rachapradit, N., Thepa, S., and Monyakulb, V.
- Subjects
- *
AIR conditioning , *ENERGY conservation , *TEMPERATURE , *COOLING , *ENERGY consumption - Abstract
This paper presents an experimental and analytical study on the inverter split-type air-conditioner for the purpose of energy saving and a proper balance between sensible and latent capacity. Performance of an inverter split-type air-conditioner is investigated at varied refrigerant mass flow rates, air volume flow rates, and set point temperatures. The performance investigated for a 2.54-kW inverter split-type air-conditioner includes cooling capacity, power consumption, the value of coefficient of performance (COP), and equipment sensible heat ratio (SHR). An increase of electrical frequency input to compressor from 34 to 66 Hz results in an increase of cooling capacity by 0.88 kW, a decrease of COP by 0.84, and a decrease of SHR by 0.11. An increase in cooling coil flow rate from 4.14 to 8.2 m3/min results in an increase in cooling capacity by 0.16 kW, an increase in COP by 0.10, and an increase in SHR by 0.15. An increase of set point temperature from 24 to 26°C results in an increase of the value of COP by 0.13 and a decrease of SHR by 0.03. The study offers guidelines for the application of small-size inverter split-type air-conditioners in hot and humid climates. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
26. Investigation on air-conditioning load profile and energy consumption of desiccant cooling system for commercial buildings in Hong Kong
- Author
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Qi, Ronghui, Lu, Lin, and Yang, Hongxing
- Subjects
- *
COMMERCIAL building energy consumption , *AIR conditioning , *COOLING loads (Mechanical engineering) , *THERMAL comfort , *DRYING agents , *ENERGY conservation , *SIMULATION methods & models - Abstract
Abstract: In Hong Kong, conventional air-conditioning (AC) systems cause a high energy consumption and poor indoor thermal comfort. This paper investigated the AC load profiles of three typical local commercial buildings, i.e. office, hotel and retail, and examined the energy consumption of liquid desiccant cooling system (LDCS) for these buildings. Simulation results showed that the cooling load contributed to more than 98% of total annual load, with high latent load proportion from March to September. The high reheating ratio, i.e. from 60% to 90%, is found to be the main reason for the poor thermal comfort. Therefore, the LDCS which could handle sensible and latent loads separately was proposed. However, the electricity-driven LDCS was found not suitable for local commercial buildings. significant energy saving could be achieved by the solar-assisted LDCS system with thermal storage, when the installation area for solar collectors is larger than the minimum required one, i.e. 9.7m2/(kWm−2) for office and 12.7m2/(kWm−2) for hotel buildings. Energy saving of different system types with different installation areas was also studied. The solar-assisted LDCS shows more energy saving in winter but less in summer. Results and conclusions can be useful for researchers and local engineers. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
27. Research on operating characteristics of direct-return chilled water system controlled by variable temperature difference
- Author
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Liu, Xue-feng, Liu, Jin-ping, Lu, Ji-dong, Liu, Lei, and Zou, Wei
- Subjects
- *
CHILLED water systems , *AIR conditioning , *SEASONAL temperature variations , *ENERGY conservation , *THERMODYNAMICS , *WATER pipelines , *ENERGY consumption , *ELECTRIC network topology - Abstract
Abstract: Terminal load distribution and pipe network structure are the key factors that affect the energy-saving potential of central air-conditioning chilled water systems, nonlinear thermodynamic performance of an air-conditioning system with large inertia will mainly exert influence on the stability and reliability of energy-saving operation control. Unreasonable variable flow control strategy can neither achieve an ideal energy-saving effect nor meet the air-conditioning comfortableness requirements. With a direct-return chilled water system as study object, this paper built a hydraulic calculation model of pipe network topology, bypass loop hydraulic calculation model, AHU thermodynamic model, and water pump variable frequency operation model. Operating frequency of a water pump for different flow ratio, pump power, temperature difference of pipe network supply and return water, pressure difference of pipe network supply and return water, bypass control valve characteristics, system adjustability coefficient, and pipe network resistance characteristics of a chilled water system are studied under the condition of given supply water temperature, and pipe network’s AHU node thermal and humid load. And energy consumption characteristics of constant temperature difference control and variable temperature difference control are also analyzed with comparison. The results can provide theoretical guidance for the stable and reliable energy-saving operation of a chilled water system. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
28. Thermal performance and cost effectiveness of wall insulation under Thai climate
- Author
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Chirarattananon, Surapong, Hien, Vu Duc, and Tummu, Preecha
- Subjects
- *
THERMAL insulation , *AIR conditioning efficiency , *AIR conditioning , *PUBLIC buildings , *DWELLINGS , *EFFECT of temperature on building materials , *ENERGY conservation , *ENERGY consumption , *ECONOMICS - Abstract
Abstract: Traditional houses and public buildings in Thailand were constructed from materials of low thermal mass and the walls were not insulated. Brick and concrete began to replace wood as walling material before air-conditioning was introduced into the country. New large buildings have glazed and closed windows so interior spaces require air-conditioning and forced ventilation. Up to the present, no insulation is used on walls. This paper presents results from an experimental and simulation study on comparative energy and economic performance of walls used to enclose air-conditioned spaces. The walls are externally and internally insulated to different thicknesses. The spaces are assumed to serve three commercial functions. Results show that insulation can generally help improve thermal performance of walls, but the function that a space serves dictates where insulation should be placed and how cost effective it is. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
29. Energy savings in a building using regenerative evaporative cooling
- Author
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Khandelwal, Ankur, Talukdar, Prabal, and Jain, Sanjeev
- Subjects
- *
EVAPORATIVE cooling , *ENERGY consumption , *ENERGY conservation , *AIR conditioning , *LIBRARY buildings , *COMPUTER simulation , *THERMAL comfort , *HEATING & ventilation industry , *TEMPERATURE , *HUMIDITY , *THERMAL properties of buildings - Abstract
Abstract: This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between −1 and +1 for most of the hours in the year. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
30. Energy performance and consumption for biogas heat pump air conditioner
- Author
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Xu, Zhenjun, Wu, Huaizhi, and Wu, Meiling
- Subjects
- *
BIOGAS , *ENERGY consumption , *HEAT pumps , *AIR conditioning , *HEAT exchangers , *INTERNAL combustion engines , *HUMIDITY , *ENERGY conservation , *POWER resources - Abstract
Abstract: Biogas engine-driven heat pump air conditioner is a new-style system which includes biogas engine-driven heat pump, primary heat exchanger, second heat exchanger, sprayed room and fans, pumps, etc. In summertime, the air can be reheated by the waste heat water from the biogas engine in the system, while the air can be reheated and humidified by the waste heat water in winter. Reducing or displacing electrical heating requirements can achieve the great opportunity for significant energy savings. This paper, therefore, aims to improve the energy performance of the AC system by using the waste heat from the biogas engine. The mathematic model was used to research the BHPAC. Explicitly, we investigated the influence of various factors including the outdoor air temperature and humidity in summer and winter. Results show that the biogas engine-driven heat pump air conditioner can save more energy than the electrical power heat pump. In summer, the minimum for percentage of primary energy saving for BHPAC is over 25%. With the outdoor air dry-bulb temperature and the relative humidity rises, the saving energy percentage rises. In winter, the minimum for percentage of primary energy saving for BHPAC is 37%. The more the outdoor air relative humidity of the outdoor air decreases, the more the BHPAC saves energy. It is proved that the system which is a highly actively fully utilizing energy technology has good partial load characteristic and good effects of energy saving. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
31. The phenomenon of evaporative cooling from a humid surface as an alternative method for air-conditioning.
- Author
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Gómez, E. Velasco, Martínez, F. C. Rey, and González, A. Tejero
- Subjects
- *
EVAPORATIVE cooling , *ENERGY consumption , *ENERGY conservation , *AIR conditioning , *AIR conditioning industry , *VAPOR pressure , *ENVIRONMENTAL engineering , *SUSTAINABLE living , *GREEN movement - Abstract
The phenomenon of evaporative cooling is a common process in nature, whose applications for cooling air are being used since the ancient years. In fact, it meets this objective with a low energy consumption, being compared to the primary energy consumption of other alternatives for cooling, as it is simply based in the phenomenon of reducing the air temperature by evaporating water on it. This process can be an interesting alternative to conventional systems in these applications where no very low temperatures are needed, like the case of air-conditioning during the summer. However, the risk of contamination by legionnaire's disease, commonly related to evaporative cooling systems, has led in recent years to the substitution of these devices in the industry by less-efficient systems, like the case of cooling towers or evaporative condensers substituted by air-condensing refrigerating processes. Therefore, these systems based in the evaporative cooling are rarely used for cooling buildings. To reduce this risk, evaporative cooling is produced from humid surfaces, in such a way that water evaporates due to the difference of vapor pressure between the surface and the air, and thus minimizing the generation of aerosols, responsible for the spread of legionnaire disease. Aerosols are nevertheless produced in conventional systems where water is sprayed or directly in contact with the stream of air; and the problem worsens if the water, which is recirculated, has been still in any moment or its temperature is adequate for the bacteria proliferation. This paper aims to introduce the thermodynamic basis in which the process is based, as well as the commercial evaporative systems and the problem associated to legionnaire's disease in this kind of systems. Furthermore, three different experimental devices based in evaporative cooling are described, which have been designed and manufactured in the Thermal Engineering Research Group of the University of Valladolid., describing their characteristics of operation and providing the experimental results obtained during their characterization, for outside air conditions typical of hot and dry summers. [ABSTRACT FROM AUTHOR]
- Published
- 2010
32. Solar-powered cooling systems: Technical and economic analysis on industrial refrigeration and air-conditioning applications
- Author
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Desideri, Umberto, Proietti, Stefania, and Sdringola, Paolo
- Subjects
- *
SOLAR air conditioning , *REFRIGERATION & refrigerating machinery , *SOLAR thermal energy , *ENERGY consumption , *ENERGY conservation , *SOLAR technology , *ENERGY economics , *POWER resources - Abstract
Abstract: In the last years, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the technologies which allows to obtain, by using the renewable solar source, an important energy saving compared to traditional air conditioning plants. The paper describes different technical installations for solar cooling, their way of operation, advantages and limits. The objective of the present study has been to analyze the technical and economic feasibility of solar absorption cooling systems, designed for two different application fields: industrial refrigeration and air conditioning. The possibility to replace or integrate the existing plants is studied, by considering the refrigeration requirements of a company, which works in meat manufacturing, and the heating and cooling demands of a hotel located in a tourist town in Italy. In the first case, the system comprises an absorption chiller coupled to solar flat plate collectors, whereas the second application is about a hybrid trigeneration plant, known as thermo-solar trigeneration; this option allows having greater operational flexibility at sites with demand for energy in the form of heating as well as cooling, for example in a hotel. In this way the authors could compare different results obtained by a technical and economic experimental analysis based on existing users and evaluate the advantages and disadvantages in order to suggest the best solution for the two studied cases. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
33. A Reliable Energy Information System for Promoting Voluntary Energy Conservation Benefits.
- Author
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Yute Chen and Jeng Kuang Hwang
- Subjects
- *
ENERGY conservation , *POWER resources , *ENERGY consumption , *AIR conditioning , *DEBIT cards , *CONSUMERS - Abstract
This paper presents the design and development of a reliable PLC/RF ENergy Information System (ENIS) for promoting voluntary energy conservation benefits. With the help of monitoring and browsing energy information immediately, the price signal and visible energy saving profile can provide incentives for customers to migrate peak demand elastically and economically. Two real-world applications of the ENIS are then reported. First, shedding peak load and diminishing energy consumption at NCTU University are explored by managing air conditioners through debit cards and energy meters (EMs). Second, in an aggregate community, the real-time pricing signals can motivate end users to shift peak demand by means of manual or automatic load controls. These examples illustrate that EMs and energy information displays with enhanced reliability are highly applicable for voluntary energy conservation in densely populated areas. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
34. Ventilated facades energy performance in summer cooling of buildings
- Author
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Ciampi, M., Leccese, F., and Tuoni, G.
- Subjects
- *
ROOFS , *VENTILATION , *HEAT , *ENERGY consumption , *AIR conditioning , *ENERGY conservation - Abstract
The use of ventilated facades and roofs can help to reduce summer thermal loads and, therefore, the energy consumption due to air-conditioning systems. This paper discusses a simple analytical method for the calculation of the energy saving achievable by using ventilated facades in which the air flow inside the air duct is due to stack effect. Two particular cases of outstanding importance are investigated. The first in which the inner masonry wall is given, and the air duct and the outer facing have to be optimized. The second in which the outer facing is given, and the inner masonry wall and the air duct have to be optimized. The first case can occur in existing buildings renovation, while the second case can occur during the design process. Finally, the influence of the variation of some quantities necessary for calculation on the energy performance of ventilated facades is investigated. In particular, the energy performance of such facades results to be strongly influenced by the air duct width, the insulating material distribution, the solar radiation intensity, the wall outer surface thermal resistance and the roughness of the slabs delimiting the air duct. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
35. Control de sistemas de energía en centros de telecomunicaciones con autómatas programables.
- Author
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García, Rolando Chávez and Yero, Rafael Millán
- Subjects
- *
ELECTRIC generators , *AIR conditioning , *TELECOMMUNICATION , *ENERGY conservation , *ENERGY consumption - Abstract
This paper suggests an adequate use of C200HX logic controller to substitute, as far as possible, the UP1-LCD controller of generators and the Zelio-logic controller of air conditioning systems, due to their high failure rates, specialized repayment needs and tall costs at international markets. C200HX logic controller's existing functions and added control on other events for saving energy in telecommunication facilities are also introduced. [ABSTRACT FROM AUTHOR]
- Published
- 2008
36. Efficient Operation of Air-Side Economizer Using Extremum Seeking Control.
- Author
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Pengfei Li, Yaoyu Li, and Seem, John E.
- Subjects
- *
AIR conditioning , *HEATING & ventilation industry , *DETECTORS , *ACTUATORS , *CONTROL theory (Engineering) , *AUTOMATION , *PROCESS control systems , *SIMULATION methods & models - Abstract
As the heating, ventilating, and air conditioning (HVAC) systems accounts for a major sector of energy consumption for commercial buildings, there has been a greater demand for improving the efficiency of such systems. The air-side economizers have been developed as a class of energy-saving HVAC devices that may increase the energy efficiency by taking advantage of outdoor air during cool or cold weather. However, many economizers do not operate in the expected manner and waste even more energy than before installation, mostly due to the unreliable sensors and actuators in practice. Better control strategy is needed for optimal and robust operation. In this paper, an extremum-seeking control (ESC) based self-optimizing strategy is proposed to minimize the energy consumption, with the feedback of chilled water supply command rather than the temperature and humidity measurements. The mechanical cooling load is minimized by seeking the optimal outdoor air damper opening in real time. Such scheme does not need temperature and humidity sensors, and depends much less on the knowledge of the economizer model. Simulation was performed on a MODELICA based transient model of a single-duct air-handling unit developed with DYMOLA and AIRCONDITIONING LIBRARY. The simulation results demonstrated the potential of using ESC to achieve the minimal mechanical cooling load in a self-optimizing manner. In addition, an antiwindup ESC scheme is proposed to handle the ESC windup issue due to actuator (damper) saturation. The simulation results validated the effectiveness of the proposed antiwindup ESC. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
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