Preset and development of frozen soil thermal conductivity data monitoring device
The design of the incubator is 500mm × 200mm × 500mm. The contact surface with the test block is made of copper plate, and the heat transfer effect is good. The other five faces are made of steel plate. A baffle is provided in the box to ensure uniform flow and structure. The design of low-temperature cold waters is to cool the return water of the incubator and then send it to the incubator. The design should take into account the volume occupied by the liquid in the circulating state and the cooling state. Therefore, the size of the box is 500mm×500mm. ×400mm, which is twice the volume of the incubator. An evaporation pipe and an electric heating pipe are provided below 1/2 of the height of the cold water tank to adjust the temperature of the cold liquid. The box body is made of stainless steel plate, plus 50mm thick extruded board as insulation material, and its structure is as shown.
Refrigeration system design of thermal conductivity tester, design of refrigeration system The device includes 2 sets of water system in -10 °C water and -25 °C water area, with R22 as refrigerant, which can be detected by its thermal property table, evaporation temperature tz=-15 At °C, the evaporation pressure Pz=0.2964MPa; the evaporation temperature tz=-30°C, the evaporation pressure Pz=0.1640MPa; the condensation temperature tl=35°C, the condensation pressure Pl=1.3496MPa. Therefore, Pl/Pz<10, both are adopted. For single-stage compression, the following two design options are available.
The test of the cooling time curve of the low-temperature cold water area measures the initial temperature of the cold liquid in the cold water area to be the same as the ambient temperature, both of which are 22 ° C ± 1 ° C. The cold liquid is always kept circulating throughout the test, and the compressor does not stop. The specific steps of the measurement are as follows: 1) Arranging and fixing the temperature probe sensor, connecting with the digital temperature display, connecting the display power supply; 2) starting the refrigeration unit to cool the cold water; 3) recording the cooling time every 5 minutes Record once; 4) When the temperature reaches the lower limit of the set value, start the electric heating tube to start heating; when the temperature reaches the upper limit of the set value, the electric heating tube stops heating.
The cold liquid temperature control curve meter consists of two low temperature cold waters of -10 ° C and -25 ° C, a refrigeration system, an incubator, a temperature control system, a temperature measuring system and a sample box. The key point and difficulty in the design of the thermal conductivity measuring instrument is the guarantee of the temperature accuracy of the circulating cold liquid in the low temperature cold water. To this end, the PID regulation principle is adopted to control the temperature of the cold liquid by controlling the electric heating tube in the water tank of the cold water zone, so that the temperature control precision is kept within the range of ±0.5 °C, and the test is performed to meet the design requirements.
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