Analysis of several common problems in pressure calibration table calibration:
The device that detects the spring hammer in the pressure calibration table will become a calibration device. Because there is no corresponding calibration procedure, a calibration certificate should be issued, and the calibration certificate should specify the measurement uncertainty. The "measurement standard assessment specification" requires "N-repeat measurement times, N should be as large as possible, generally not less than 10. If the repetitive introduction of the uncertainty component is not the main measurement uncertainty in the verification or calibration results Component, which allows to reduce the number of repeated measurements appropriately, but at least N>=6" should be satisfied. However, the use of the calibration device of the pressure calibration table emphasizes that “the impact element should be turned to different positions after each operation. The average value of the three readings on the calibration device can be used as the actual value of the impact energy of the measured spring hammer.†Therefore, the number of repeated measurements is insufficient.
Domestic and foreign production of the pressure calibration table spring hammer calibration device impact kinetic energy measured value using the dial pointer readings, due to the size of the dial and the diameter of the pointer caused the reading error is too large. There are two reasons for this: (1) Large division values. Because the impact kinetic energy of the spring hammer of the pressure checkbench is very small, it is difficult to achieve a small division value by conducting a small-scale 2J split on the disk by using the principle of potential energy. At present, the PDL company's domestic sales of the pressure calibration table spring hammer calibration device has a division value of 0.02J, scale line spacing of about 1MM, a few companies in the country production of pressure calibration table spring hammer calibration device indexing value 0.01J, tick spacing is less than 1MM. Taking a 0.14J spring impactor as an example, the accuracy of the calibration device is calculated as 3%, and its index value should be 0.004J. It is difficult to achieve the internal subdivision scale line on the 1MM pitch of the dial. (2) The pointer diameter greatly affects the reading. The calibration device manufactured at home and abroad uses a 0.7MM piano wire as a pointer, and the pointer of 0.7MM occupies 2/3 space of 1MM between two scale lines, resulting in a large error in estimation. Even if the scale is subdivided between the marks with a pitch of only 1 mm, the indexing value is increased. However, due to the effect of the 0.7MM indicator, the small value of the indexing is also invalid, and the estimation error is still large.
Through the above analysis, the spring hammer calibration device in the pressure calibration table can not meet the calibration of all the spring hammers. At the same time, there are no uniform calibration standards for the measurement institutions throughout the country, so the calibration methods and calibration devices are different. Therefore, in order to improve product quality and strengthen measurement management, the device has a uniform calibration standard across the country, and it is very important to develop a scientific and effective calibration device for pressure calibration tables.
A heat exchanger is a device used to transfer heat, usually to transfer heat from one fluid to another without them mixing. A heat exchanger usually consists of a number of parallel pipes in which one fluid flows through the pipe and another fluid flows through the outside of the pipe. In this way, heat can be transferred from one fluid to another for heating or cooling purposes. Heat exchangers are widely used in many industries, such as chemical, pharmaceutical, food processing, air conditioning and heating systems, etc.
Heat exchanger usually consists of the following components:
1. Heat exchange pipe: Pipe used to transfer heat, usually made of metal materials, such as copper, stainless steel, etc.
2. Heat exchange surface: A surface used to transfer heat, usually consisting of metal sheets or pipes. The greater the surface area, the higher the heat transfer efficiency.
3. Housing: Housing, usually made of metal or plastic, used to secure heat exchange pipes and surfaces.
4. Seals: Seals used to prevent media leakage, usually made of rubber or silicone rubber.
5. Support: A support used to support a heat exchanger, usually made of steel or cast iron.
6. Import and export pipes: pipes used for medium entry and exit, usually made of metal or plastic.
7. Cleaning hole: A hole used to clean the inside of the heat exchanger, usually located on the upper or side of the heat exchanger.
8. Insulation layer: Insulation layer used to keep the temperature of the heat exchanger stable, usually made of glass wool or polyurethane foam.
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