Papers by Keyword: Vacuum Glazing

Abstract: This document deals with the determination of thermal transmission properties of wood-aluminium window with vacuum glazing. Test measurements are performed with guarded hot-box method at defined temperature difference. They describe how the support pillars influence temperature distribution on the surface and how the edge vacuum glazing influence the heat flow through window. The deformation of the temperature field due to support pillars is surprisingly small and its range is from 0.20 K to 0.46 K with temperature difference on both sides of approximately 20 K. Decrease of internal surface temperature from the middle of glass to the edge is about 20.04 – 16.15 = 3.89 K.

Abstract: Insulating glass is the main function material of the building curtain wall and building windows and doors, which plays a significant role in the energy-saving function more than 50% of the whole building. In recent years, the thermal insulating property and sound insulating property of insulating glass improves greatly with the combination of vacuum glazing. With the combination of PV (photovoltaic) glass, insulating glass has structural-function integration characteristics. Vacuum glazing and BIPV are two important types of insulating glass which are developing rapidly. In this paper, research developments and test experience of vacuum glazing and BIPV were summarized. Through analyzing the energy-saving test data of vacuum glazing and BIPV, the energy-saving influencing factors were given.

Abstract: Vacuum failure will lead to insulation function failure and increasing huge potential security problems for vacuum glazing, it is necessary to inspect the vacuum degree value of the vacuum glazing in service. In this work, the relationship between the bearing behavior and vacuum degree value of the vacuum glazing was studied by experiment, the experiment results show that the bearing behavior of vacuum glazing showed a greater than 50% reduction after the vacuum degree lose completely in vacuum cavity of the vacuum glazing. One test technique for degradation ratio of vacuum degree of vacuum glazing by photoelastic method was developed in this study. Through linear proportional relationship between support stress spot size and degradation ratio of vacuum degree observed via photoelastic method, vacuum degree completely disappear and stress spot size is 0. So, the ratio R(less than or equal to 1) represent the relative differential pressure between the support stress spot size tested in-situ and the support stress spot size measured in vacuum degree intact environment. The degradation ratio of vacuum degree is (1-R) %. Obtaining qualitative or semi-quantitative assessment of vacuum degree degradation ratio of vacuum glazing through observe support stress spot size with photoelastic apparatus.

Abstract: The retrofit of the historical building stock has gained significance due to energy efficiency requirements in the building sector. Major attention is drawn to windows as they are typically the building components with the highest heat transfer coefficient of the building envelope. Therefore, vacuum glazing is a potential option for improving the thermal performance of casement windows. In this context, specific considerations regarding building physics and heritage protection regulations are required.The present contribution describes the current progress of the research project VIG-SYS-RENO. New double glazing products with durable vacuum layer are emerging on the market. Such developments can be regarded as a major step toward energy-efficient windows with U-values close to conventional opaque building elements. Small thickness and excellent thermal resistance of vacuum insulation glazing renders it an attractive option in thermal retrofit of historical buildings. Vacuum glazing systems could potentially offer a feasible balance between conservation and thermal performance of windows. However, prior to any application, a set of aspects and potential issues have to be assessed and explored. These include: (i) thermal bridging effects in different joint positions, for instance the glass edge seal and the frame & wall joint; (ii) the positioning of tight layers in composite or casement windows; (iii) aspects of structural integrity of windows equipped with vacuum glazing. The present contribution structures the different aspects that need to be considered in utilization of vacuum glazing in thermal retrofit, describes applied evaluation methods, first results of the ongoing research project, and illustrates the influence of various rebate depth and length of the edge seal on thermal transmission of the window.

Abstract: The existence of a temperature difference across a vacuum glazing causes dimensional differences between the hot and cold glass sheets, with associated mechanical stresses and bending. In order to understand the distribution characteristics of the stresses and deformation in vacuum glazing due to temperature difference, in this work, the mechanical models were established and the calculation formula of the shear stress in the edge seal and bending tensile stress on the surface of the two glass sheets of the vacuum glazing were given. A test device was designed and the maximum tensile stresses and deflection of the vacuum glazing with various temperature difference were tested by experimental, it was shown that they are identical between the experiments and the theories.

Abstract: In order to understand the carrying capacity and deformation characteristics of vacuum glazing, experimental and theoretical research were carried out on load bearing capacity of four sides supported vacuum glazing, the load-displacement and load-stress curves of the test samples under uniform load were obtained. The experimental result indicated that under the test samples have the same thickness, the capacity of resisting wind load of the vacuum glazing is not so strong as common glass plate. To design methods of the vacuum glazing plate, one of those is to calculate the stresses and the deflection with the equivalent thickness as an integral model. The equivalent thickness coefficient of the vacuum glazing is about 0.85~0.9, and the magnitudes of the equivalent thickness coefficient of the vacuum glazing is decreases with increasing of the glass thickness, but not been influenced by the length and width dimensions of the glass plate. Take into account the influence of long term tensile stresses in vacuum glazing due to atmospheric pressure on the glass strength, the calculation formula of resistance to wind load for the vacuum glazing was given.

Abstract: Vacuum glazing is a new building material with excellent energy conservation and sound insulation properties. Usually, the edge sealing layer between two sheets of glass substrates are prepared by spraying the seal glass paste and then sintering. In the present research, a more effective preparation method is reported. The edge sealing layer is prepared with a glass paste by screen printing, and then sintering. The glass paste for the preparation of edge sealing layer of vacuum glazing was prepared by using low melting glass powder, ZrW2O8 powder with negative coefficient of thermal expansion and ethyl cellulose terpineol solution. The test result of the shear strength of the sealing layer indicated that the sealing is reliable.

Abstract: Simulation analysis of thermal performance for vacuum glazing was conducted in this paper. The heat conduction through the support pillars and edge seal and the radiation between two glass sheets were considered. The heat conductance of residual gas in vacuum gap was ignored for a low pressure of less than 0.1Pa. Two pieces of vacuum glazing with sizes of 0.3 × 0.3 m and 1.0 × 1.0 m were simulated. In order to check the accuracy of simulations with specified mesh number, the thermal performance of a small central area (4mm×4mm) with a single pillar in the center was simulated using a graded mesh of 41×41×5 nodes. The heat transfer coefficients of this unit obtained from simulation and analytic prediction were 2.194Wm^-2K^-1 and 2.257Wm^-2K^-1 respectively, with a deviation of 2.79%. The three dimensional (3D) isotherms and two dimensional (2D) isotherms on the cold and hot surfaces of the specimens were also presented. For a validity of simulated results, a guarded hot box calorimeter was used to determine the experimental thermal performance of 1.0m×1.0m vacuum glazing. The overall heat transfer coefficients obtained from experiment and simulation were 2.55Wm^-2K-1 and 2.47Wm^-2K^-1 respectively, with a deviation of 3.14%.

Abstract: Vacuum glazing is a very choice in building energy efficiency. Therefore, it is necessary to study on evacuating process of vacuum glazing. Based on fundamental pumping equation of vacuum technique and simplified the existing pumping system for vacuum glazing, a mathematical model, which is described evacuating process of vacuum glazing, is established. An exact mathematical solution is obtained by solving the model. According to the solution, an example from a practical evacuating system is solved and analyzed, and two conclusions are summed up as follows: First, the evacuating time needed for vacuum glazing is mainly depended on the flow conductance at vacuum glazing’s bleeding point; Secondly, the ultimate pressure of vacuum chamber should two orders of magnitude lower than the required pressure in the vacuum glazing. Above model, solution and conclusions have a certain guiding significance in the actual production of vacuum glazing.

Abstract: The mathematical model of the braced stress-strain in the vacuum glazing was established with the crunode method by elastic mechanics. The braced stress-strain field of vacuum glazing was received, and the stress-strain distribution was analyzed at the same time. Electric test method was used to validate the stress distribution. The experimental results are shown that the maximal stress of vacuum glazing occurs in the second braced pillar of the four-square side. The maximal stress value by elastic mechanics is 11.057MPa, while the measured value by electric test method is 11.765MPa, and its tolerance is only 6.02%. The positive stress in the cross section of the braced pillar is 179MPa, the longitudinal strains of steel and glazing braced pillar are 0.2686μm and 0.7414μm, respectively. The tolerance of braced pillar height and the glazing level degree are controlled to guarantee force equality, which increases strength, dependability, and service life of vacuum glazing.