Key Laboratory of Building Safety and Energy Efficiency

Hunan, China

Key Laboratory of Building Safety and Energy Efficiency

Hunan, China

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Du C.,Hunan University | Du C.,Key Laboratory of Building Safety and Energy Efficiency | Chen Y.,Hunan University | Chen Y.,Key Laboratory of Building Safety and Energy Efficiency
Renewable Energy | Year: 2011

Analysis of borehole thermal resistance is important for the standard sizing of ground heat exchanger (GHE). In this paper, a p-linear dimensionless average fluid temperature is proposed to estimate borehole thermal resistance. A p-linear dimensionless fluid temperature and p-linear dimensionless average fluid temperature are introduced, and the p-linear dimensionless fluid temperature is compared with theoretical dimensionless fluid temperature calculated by quasi-three-dimensional model for both single and double U-tubes. Results show that the p-linear dimensionless temperatures with parameters p→. 0 and p= -1/2 are respectively in good agreement with the theoretical dimensionless fluid temperatures of single and double U-tubes. Therefore, the dimensionless logarithmic mean temperature for p→. 0 and the dimensionless geometric mean temperature for p= -1/2 should respectively be adopted to reasonably estimate the thermal resistance of single and double U-tube boreholes. © 2010 Elsevier Ltd.


Wang L.,Hunan University | Wang L.,Key Laboratory of Building Safety and Energy Efficiency | Ma J.,Hunan University | Zhao Y.,Hunan University | Liu Q.,Hunan University
Journal of Applied Mechanics, Transactions ASME | Year: 2013

In this study, the nonlinear equation of motion of the beam on the elastic foundation is obtained via the Newton's second law of motion, and its free vibration nature is investigated. Considering the inextensional condition, the planar model of the beam accounting for the effects of the rotary inertia is derived. Then, the linear vibration and nonlinear vibration of the beam on the elastic foundation are examined. It is shown that the cut-off frequency can be observed in the frequency spectrum of the beam response. The effects of the rotary inertia on the natural frequencies are systematically investigated. Finally, the frequency differences, due to the different foundation models, and the possible modal interaction of the beam are discussed. Copyright © 2013 by ASME.


Wang L.,Hunan University | Wang L.,Key Laboratory of Building Safety and Energy Efficiency | Ma J.,Hunan University | Li L.,Hunan University | Peng J.,Hunan University
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2013

The large amplitude vibrations of the inextensional beam resting on the elastic foundation under three-to-one internal resonance are investigated. The inextensional condition and multimodal discretization are used to obtain the equation of in-plane motion and modulation equations. Due to the second-order moment of the subgrade reaction, the quadratic nonlinearity is included in the present model. Moreover, this moment destroys the conservative character of the system. The nonlinear response and the associated stability are examined by means of frequency (force)-response curves, and the shooting method is applied to investigate the dynamic solutions. Particular attention is placed on the effects of the cut-off frequency and boundary conditions. The results show that the cut-off frequency and boundary conditions do not significantly affect the contribution of nonresonant modes to the nonlinear coefficients. Moreover, the effects of foundation models on the three-to-one resonant dynamics of the beam are discussed. © 2013 American Society of Mechanical Engineers.


Wang H.,Hunan University | Wang H.,Henan University of Technology | Wang H.,Key Laboratory of Building Safety and Energy Efficiency | Chen Y.,Hunan University | And 5 more authors.
Energy and Buildings | Year: 2012

An online model-based fault detection and diagnosis (FDD) strategy is presented in this paper to diagnose abrupt faults of variable-air-volume (VAV) air handling units (AHU). The FDD strategy proposed adopts a hybrid approach integrating model-based FDD method and rule-based FDD method. Self-tuning model is used to detect the faults in AHU systems. Model parameters are adjusted by a genetic algorithm-based optimization method to reduce the residual between prediction and measurement. If the residual exceeds the corresponding fault detection threshold, it indicates the occurrence of fault or abnormality in AHU systems. Meanwhile, an online adaptive scheme is proposed to estimate the fault detection threshold, which varies with system operating conditions. Furthermore, three rule-based fault classifiers are developed and utilized to find fault sources. The FDD strategy proposed was tested and validated on real VAV air-conditioning systems involving multiple faults. The validation results show that the FDD strategy proposed can provide an effective tool for detecting and diagnosing the faults of air handling units. © 2012 Elsevier B.V. All rights reserved.


Wang L.,Hunan University | Wang L.,Key Laboratory of Building Safety and Energy Efficiency | Ma J.,Hunan University | Peng J.,Hunan University | Li L.,Hunan University
International Journal of Mechanical Sciences | Year: 2013

The nonlinear vibration and parametric instability of the inextensional beam on the elastic foundation are investigated. Considering the inextensional condition and second-order moment of the subgrade reaction, the motion equation of the beam on the elastic foundation is obtained via the Hamilton principle. Then the Galerkin method is applied to obtain the discretized model. The periodic motion is examined by means of the continuation method. Whereas, the numerical simulation is performed to study the nonperiodic motion, particular attention is placed on the nonlinear response of two resonant beams and the parametric instability. Finally, the effects of the boundary conditions and foundation models on the nonlinear vibration of the beams are discussed. © 2012 Published by Elsevier Ltd. All rights reserved.


Wang L.,Hunan University | Wang L.,Key Laboratory of Building Safety and Energy Efficiency | Rega G.,University of Rome La Sapienza
International Journal of Solids and Structures | Year: 2010

In this study, the 3D nonlinear equations of motion of the suspended cable with moving mass are obtained via the Hamilton principle, and its transient linear planar dynamics is investigated. Considering the quasi-static assumption, the condensed planar model accounting for the effect of the moving mass is derived, and it is then discretized by choosing the static deflection and sine series as shape functions. It is shown that this expansion shows good convergence features. The Newmark method is used to investigate the transient response. The effects of the inertia force, mass, sag and velocity of the moving mass on the transient dynamics of the suspended cable are systematically investigated. Finally, the horizontal tension of the suspended cable and the case of sequentially moving masses are examined. © 2010 Elsevier Ltd. All rights reserved.


Wang H.,Hunan University | Wang H.,Key Laboratory of Building Safety and Energy Efficiency | Chen Y.,Hunan University | Chen Y.,Key Laboratory of Building Safety and Energy Efficiency | And 2 more authors.
Automation in Construction | Year: 2012

Proper design, reliable control and health of variable-air-volume (VAV) terminals are essential for reliable operation and energy efficiency of VAV air-conditioning systems. This paper presents an online fault diagnosis tool for pressure-independent VAV terminals and its implementation. The fault diagnosis tool is developed using a robust fault detection and diagnosis strategy for VAV terminals. Cumulative sum (CUSUM) control chart with estimated process parameters is utilized to detect faults in VAV terminals. A rule-based fault classifier is designed and utilized to find the sources of faults in VAV terminals. The fault diagnosis tool relies only upon the sensor data and control signals that are commonly available in building management control systems (BMCS). The fault diagnosis tool can be installed in BMCS to online read the operating data of all VAV terminals in a building through local area network and diagnose faults of VAV terminals in the building. The fault diagnosis tool has been validated in a large-scale office building located in Hong Kong and can effectively find all faults occurring in VAV terminals. © 2011 Elsevier B.V. All rights reserved.


Guo Y.,Key Laboratory of Building Safety and Energy Efficiency | Guo Y.,Hunan University | Guo Y.,Henan University of Science and Technology | Zhang G.,Key Laboratory of Building Safety and Energy Efficiency | And 7 more authors.
Applied Thermal Engineering | Year: 2012

This paper reports a techno-economic comparison between a direct expansion ground-source heat pump system (DX-GSHP) and a secondary loop ground-coupled heat pump system (SL-GCHP). For this purpose, a DX-GSHP and an SL-GCHP system are designed and installed in parallel for same space cooling load in a demonstrating building in Hunan province, China. The structures of the two systems are described. The performances of the two systems were experimentally determined from June to September in cooling season of 2009. The average cooling performance coefficients (PFsys) of the DX-GSHP system was obtained to be 6.03 and that of the SL-GCHP system was determined to be 5.64. The average input power values for the DX-GSHP system and the SL-GCHP system are found to be 1.39 and 1.715 kWh, respectively, which means that DX-GSHP has a 23.8% higher efficiency than SL-GCHP in cooling mode. The paper studied the initial investment, the annual cost (AC) and the present worth (PW) of the two systems. It is concluded that the DX-GSHP is more economic than the SL-GCHP. Further more, the advantage and disadvantage of the DX-GSHP are analyzed. The minimal refrigerant velocity in order to ensure oil return is derived. It is shown that DX-GSHP could be vigorously pushed when oil return problem is solved satisfactorily. © 2011 Elsevier Ltd. All rights reserved.


Wang H.,Hunan University | Wang H.,Key Laboratory of Building Safety and Energy Efficiency | Chen Y.,Hunan University | Chen Y.,Key Laboratory of Building Safety and Energy Efficiency | And 2 more authors.
Energy and Buildings | Year: 2011

A robust fault detection and diagnosis (FDD) strategy using a hybrid approach is presented for pressure-independent variable air volume (VAV) terminals in this paper. The residual-based cumulative sum (CUSUM) control charts are utilized to detect faults in VAV terminals. The residuals between the temperature error and its predication are generated using autoregressive time-series models. The standard CUSUM control charts are used to monitor the residuals which are statistically independent. If the CUSUM value exceeds the chart limits, it means the occurrence of fault or abnormity in the corresponding VAV terminal. The residual-based CUSUM control chart can improve the accuracy of fault detection through eliminating the effects of serial correlation on the performance of control charts. Also, the residual-based CUSUM control chart can enhance the robustness and reliability of fault detection through reducing the impacts of normal transient changes. A rule-based fault classifier consisting of expert rules and fault isolation algorithms is developed to isolate 15 fault sources. The FDD strategy was online tested and validated using in real time data collected from real VAV air-conditioning systems. © 2011 Elsevier B.V. All rights reserved.


Zhou J.,Hunan University | Zhou J.,Key Laboratory of Building Safety and Energy Efficiency | Chen Y.,Hunan University | Chen Y.,Key Laboratory of Building Safety and Energy Efficiency
Renewable and Sustainable Energy Reviews | Year: 2010

The need to energy conservation and sustainable development in buildings is causing a new interest towards passive solar systems. Among them, double-skin facade (DSF) proves to be extremely attractive and promising. DSF is building envelope formed by two layers of different glazing facades which are separated by a ventilated air cavity. The cavity of DSF is used to collect or evacuate the solar radiation absorbed by the facades, thereby improving the thermal comfort and the indoor air quality while conserving energy for heating and cooling. Being a technique developed for colder climates, DSF has been widely applied in commercial buildings across Europe. Nowadays buildings with DSF also appear in the hot-summer and cold-winter zone in China where the weather conditions in summer seem to be not so good for the application. In fact, the thermal analysis of the DSF system is essential to its application in such hot-summer zone. This paper seeks to describe the existing main research methods on the thermal performance of DSF and the shading devices. Problems and possibilities are concomitant. Applying ventilated DSF with controlled shading device system would be a new efficient way for the commercial buildings in the hot-summer and cold-winter zone to meet the task of sustainable building design in China. © 2009 Elsevier Ltd. All rights reserved.

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