•Numerical modeling of PCM panels used in building envelope was studied.•Numerical result was validated well with the experiment data.•Temperature variations of the PCM wall and roof were analyzed ...numerically.•Internal temperature developments were researched for the PCM wall and roof.•Thermal energy savings for the PCM systems were analyzed.
The phase change material (PCM) used in the building envelope can decrease the building energy consumption and improve the thermal comfort by enhancing the thermal energy storage capacity of the wall and the roof. In this research, two new PCM systems, i.e., PCMOW (capric acid contained in the panels installed on the outside surface of building) and PCMIW (capric acid and 1-dodecanol contained in the panels installed on the inside surface of building), have been developed numerically. The main study constitutes four parts: (1) the model and its validation; (2) the analysis on temperature variations of the wall and the roof; (3) the analysis on the internal temperature developments of the wall and the roof; (4) the study of thermal energy saving. A mathematical model and its corresponding numerical solution were presented. Relative error analysis inclusive of maximum and average errors and Bland–Altman analysis were employed for validation. It is found that the numerical simulation achieved good validity. The theoretical analysis of temperature variations of the walls and the roofs for the PCMOW, PCMIW and reference rooms has been conducted. Then, the internal temperature developments of PCMOM and PCMIW systems were analyzed to reveal the operation of the PCM panel in the wall and the roof. This study also explored the analysis method of thermal energy savings for the two PCM systems to maintain the indoor temperature within thermal comfort zone.
This paper is focused on preparation and performance analysis of a series of form-stable phase change materials (FSPCMs), based on eutectic mixtures as phase change materials (PCMs) for thermal ...energy storage and high-density polyethylene (HDPE)-ethylene-vinyl acetate (EVA) polymer as supporting materials. The PCMs were eutectic mixtures of tetradecanol (TD)-capric acid (CA), TD-lauric acid (LA), and TD-myristic acid (MA), which were rarely explored before. Thermal properties of eutectic mixtures and FSPCMs were measured by differential scanning calorimeter (DSC). The onset melting/solidification temperatures of form-stable PCMs were 19.13 °C/13.32 °C (FS TD-CA PCM), 24.53 °C/24.92 °C (FS TD-LA PCM), and 33.15 °C/30.72 °C (FS TD-MA PCM), respectively, and latent heats were almost greater than 90 J/g. The surface morphologies and chemical stability of form-stable PCM were surveyed by scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The thermal cycling test revealed that the thermal reliability of these three form-stable PCMs was good. Thermal storage/release experiment indicated melting/solidification time was shortened by introducing 10 wt % aluminum powder (AP). It is concluded that these FSPCMs can act as potential building thermal storage materials in terms of their satisfactory thermal properties.
•A one-dimensional phase change heat transfer model (Type272) was established.•The latent heat utilization ratio (α) was proposed.•The model was validated using mathematical analysis under two ...different conditions.•Using the ‘BOUNDARY’ connected Type56 and Type272.
The aim of the present work is to set up an apparent specific heat capacity phase change heat transfer model and a new TRNSYS component (Type272). A PCM (phase change material) room model is established by combining Type272 and some TRNSYS components (Type 56, 109, 16, 69, 33, and Type 65). The latent heat utilization ratio (α) is proposed in Type272 which treats the melting and the solidification process, respectively. To validate the new model, a full-scale experiment room installed with PCM panels is built, and two different working conditions (passive/active cool storage condition) are set up. It is found that both the trend and the simulation data of the model are agreed well with the experiment results. In the two different conditions, the MREs (mean relative error) between the simulated and the measured data are less than 3% and 7.59%, respectively, and the consistent match degree lies between 90.10% and 98.81%. The new model, with simplicity, adaptability and practicality, can accurately simulate indoor temperature and the surface wall temperatures. Our work provides an effective tool to optimize the design of the PCM room by simulating different kinds of PCMs, locations, and different combinations with cold and heat source.
•A new kind of phase change material eutectic mixture was prepared.•A novel energy efficiency roof coupled with PCM and cool materials was proposed.•Experiments of full-scale rooms built with new ...type roof were performed.•Thermal performance of three rooms with different roofs were analyzed.
Phase change materials (PCM) and cool materials used in construction field cannot only effectively reduce buildings energy consumption, but also improve indoor thermal comfort and mitigate the urban heat island (UHI) condition. A novel energy efficiency roof coupled with PCM and cool materials has been conducted a field test in Tianjin of China. A kind of PCM-eutectic mixture was prepared, which was encapsulated in the polyethylene of raised temperature resistance (PE-RT) pipe, for using in building roofs. Thermal performances such as the roof surface temperatures and heat fluxes have been studied. The results indicated that, compared with reference rooms, the novel energy efficiency roof has shown good effect on decreasing the peaks of temperature and heat flux, which means that the influence of the outdoor circumstance on indoor environment has been weakened. In conclusion, it has been proved that the novel roof has good thermal insulation effect and energy efficiency potential.
•The aluminum alloy 6082 in this study is an extruded material after aging.•Compare the traditional constitutive equation of the material and the strain-compensated Arrhenius model with the newly ...established PSO-BP network model.•Use statistical analysis methods for data analysis.
It is important to model the flow behavior of an aged aluminum alloy AA6082 as an extrusion material before design and optimize of the forming process. In this study, the isothermal compression tests were carried out on Gleeble-3800 thermal simulator in the temperature range of 423−773 K and the deformation condition of 0.01–1.0 s−1 to study the cold temperature and hot deformation behavior of aluminum alloy AA6082. Considering the experimental error, the discussion based on friction and temperature correction is carried out. According to the modified data, based on the traditional Arrhenius constitutive model, a method combining the strain compensation Arrhenius model and PSO-BP neural network was proposed to describe the flow behavior of aluminum alloy AA6082. The prediction ability and stability of the model are evaluated by using the linear correlation coefficient(r), the average relative errors (AARE), the Root mean square errors(RMSE) and the relative errors (RE) in statistical analysis. The results show that the 3-10-8-1 double hidden layer neural network model based on PSO-BP has higher effect in predicting the flow characteristics of aging aluminum alloy AA6082 than that of Arrhenius model based on strain compensation. The linear correlation coefficient, mean relative error and root mean square error are 0.9996 %, 2.001 % and 1.665 MPa respectively.
In order to improve the lubrication performance of polytetrafluoroethylene (PTFE) coating. Modified graphene (RGO) was prepared by Hummers method and ion modification method. RGO/PTFE composites were ...prepared by solvent-assisted blending. The surface morphology and microstructure of RGO, PTFE and composites with different concentrations were characterized and analyzed by scanning electron microscopy (SEM), Raman spectroscopy (XRD) and X-ray diffraction (XRD). The tribological properties of RGO, PTFE and composite coatings based on 45# steel were studied by ball-disk friction tests. The wear marks were characterized by scanning electron microscope (SEM), energy dispersive instrument (EDS) and 3D profiler. The results show that 5 wt% RGO/ PTFE composite has lower friction coefficient and the best wear resistance. The friction coefficient of the composite is as low as 0.11, which is 37% and 51% lower than that of single-component RGO and PTFE, respectively. The wear resistance of the composite is 155.8% higher than that of single-component RGO and PTFE. The formulations of lubricating coatings in this paper are independently developed and have excellent antiwear effects. The synergistic mechanism of RGO and PTFE is proposed to explain the improvement of friction properties of composite coatings.
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Research and development on UV-LIGA at HUST Zhimou Xu; Shaowei He; Xong Li ...
Fifth International Conference onElectronic Packaging Technology Proceedings, 2003. ICEPT2003,
2003
Conference Proceeding
UV-LIGA utilizes, instead of the X-ray an ultraviolet source to expose the resists. Such a source can be provided by mercury lamps. The mask involved is a simple chromium mask. These factors are ...decisive in making the UV-LIGA much cheaper than the LIGA fabrication. UV-LIGA fills the gap existing in fabrication technologies between the methods of classical mechanics and the technologies of microelectronics, offering completely new design and construction possibilities for sensors, actuators and microsystems, such as microfluidic systems. In addition, UV-LIGA technology has been extensively applied in the fields of Microelectromechanical System (MEMS). UV-LIGA technology has been studied for several years at Huazhong University of Science and Technology (HUST). In particular, the important development of UV-LIGA was obtained in the past two years. In this paper, the research and development on UV-LIGA technology at HUST will be described.
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