Development Of Measuring Instrument For Heat Transfer Coefficient Of Vacuum Glass

With the development of a fossil energy to be used in the process of environmental pollution, energy saving and emission reduction as a basic national policy has been particularly concerned by the community. Under this policy, building energy consumption accounts for about 40% of the energy consumption of the whole society which expands the area of the window glass to increase indoor ventilation and lighting so as to improve the quality of life, at the same time, causes new problem of the rising energy consumption. With the development of science and technology, vacuum glass windows in buildings are used as the ideal lighting and heat insulation material compared with ordinary glass and insulating glass has greatly improved, but as the cost is higher, the industrialized production conditions are not mature enough and vacuum degree on-line measurement devices become the bottleneck of the development of this technology.The vacuum glass heat insulation and sound insulation performance is reflected in the main parameters-heat transfer coefficient K. The application of vacuum glass heat transfer coefficient measuring instrument is still in the stage of laboratory measurements, which can only be in a sealed environment of a small vacuum glass sample for K value measurement. And in the process of the industrialization of production, vacuum glass is used in accordance with the actual needs with a certain size, due to its own inalienable characteristics, therefore, it is urgent to develop a kind of measuring instrument with open structure to realize the function of on-line detection. Commissioned the research is supported by Xi’an MERS company, according to the "2008 China promulgated the vacuum glass national standards" JC/T1079-2008, for the the design of on-line detecting instrument of vacuum glass heat transfer coefficient based on the microprocessor GD32, the project includes hardware design, software design, mechanical structure design and the final production of the prototype. The main work includes the following parts:(1) Design and implementation of temperature control system. According to the provisions of the national standard of vacuum glass, there is a difficult problem in the control system to make a hot plate’s temperature unchanged at 40oC and a cold plate’s temperature unchanged at 10oC and constant temperature control has stability, accuracy and real-time. The PT1000 thin film platinum resistance is selected as temperature sensor because of its good stability and high accuracy and the BP neural network is adopted for its nonlinear correction. The loop temperature control system consist of the electric furnace wire selected for the heating source, the water cooling plate selected for the cooling source and the controller. The four ring structure is adopted to achieve the effect of thermal insulation outside the hot plate and the cold plate detection.(2) Design and manufacture of constant pressure control system. The pressure has a great influence for vacuum glass plate to measure K value and it is analyzed that the influence is showed in contacting conductance between the measurement plate and hollow glass, but the important factors hasn’t stated in the national standard and the constant pressure must be selected as one of the necessary conditions for the measurement of complement. The natural counterweight is adopted to achieve constant pressure conditions in Prototype, and it has an advantage over pressure sensor consisting of a constant pressure closed loop control system in the reliability and price advantages.(3) Design and manufacture of open structure measuring instrument. Aimed at the current situation in which the status is only measured in laboratory sealed environment for small pieces of vacuum glass, the re-design open structure makes the mechanical structure of the system in the static table and move the table clamp synthetic three terminal opening, and there is no limitation for measuring glass, which is fully meet the measurement needs of industrial production line of various size of glass vacuum.This research completes the expected goal, designs and implements of the system hardware circuit prototype production, completes the system software part of the preparation and debugging, the system can run smoothly, the vacuum glass heat transfer coefficient measurement meets the national standard, especially the constant discovery and implementation, it makes the system more precise measurements with the requirements for measuring instrument company, this provides a strong technical support for the large-scale industry of production and application of vacuum glass.