This type of machine superconducting magnet refrigeration system uses closed-circuit helium circulation, the compressor is independent from the cold head, connected by a flexible pressure pipe. In the cold head, the high pressure helium is controlled by a rotary valve mounted on the shaft of the electronic synchronous motor. The rotary valve rotates on the control panel, controls the piston to compress the gas to drive the filter and the regenerator, and passes the additional eccentricity on the control panel. The small holes form an alternating cycle of the high pressure gas chamber and the low pressure gas chamber, complete the inhalation and exhaust processes, and bring the heat in the cold head to the BCC. The BCC converts the cold-pressure high-temperature helium from the cold head into a high-pressure low-temperature helium gas and sends it back to the cold head, and cools the cold head motor. The heat released in this conversion is taken away by the cold water in the water cooler connected to the BCC. Due to the water quality and the existence of iron pipes in the water circulation system, the water cooler and BCC are corroded and fouled after working for several years, causing the water volume in the water pipe to be too small, which directly leads to insufficient heat exchange with the high temperature helium in the BCC. , causing the helium temperature to be too high alarm, protection shutdown; or heat exchange with the compressor cooling oil is not good, resulting in excessive oil temperature protection shutdown. From the circuit analysis, if the helium temperature is too high and stop, the temperature controller TSH2 or TSH1 will operate, the relay K2 will be disconnected, the K4 coil will work, the suction will be closed, the hightemp1 light will be on, and the K1 will be turned off to de-energize the compressor and the cold head motor. . The fault is due to the fact that the heat of the compressor cooling oil cannot be fully exchanged with the cooling water, and the oil temperature is too high, causing the compressor to overheat protection and stop; because there is no linkage between the compressor and the cold head motor during the design of the machine, the compressor After the overheat protection is stopped, the cold head motor power supply is not cut off, the motor is still in working state, its working heat is cooled by BCC shutdown without low temperature helium gas, and the internal coil is burned and short-circuited for a long time, causing the F2 fuse overload protection. Turn off the BCC power supply.
A shell and tube heat exchanger is a type of heat exchanger that is commonly used for heating, cooling and condensing applications. lt consists of a shell with an internal bundle of tubes,which allows the hot and cold fluids to pass through the walls of the exchanger and exchange their energy. Shell and tube exchangers are classified in several ways, including design, operational construct, and construction materials. Mainly Fixed Tube Heat Exchanger, Floating Head Heat Exchanger, U-tube Heat Exchanger, and double tube heat exchanger.
The working principle of a shell and tube heat exchanger is relatively simple. The system is designed with two separate flows on either side of the heat exchanger. The primary flow of the hot fluid passes through the tubes, while the secondary flow of the cold fluid passes through the spaces between the tubes. Heat is then transferred from the hot side to the cold side via conduction, leading to an exchange of temperatures.
Shell and tube heat exchangers are normally used in process plants and used in a wide range of applications. A case in point is the cooling of condensates in refineries and nuclear power plants. In this application, condensate is heated using an external source and passed through the tube section of the heat exchanger. This condensate is then cooled and condensed as it passes through the shell side, where the heat is transferred to a cooling medium such as water, steam or oil.
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