U tube heat exchanger is suitable for the large temperature difference between tube side and shell side. The shell side media is easy to scale and needs cleaning, while the tube side media is clean and not easy to scale. It is also suitable for high temperature, high pressure, fluid corrosive working conditions.
Each heat exchange tube is bent into U-shape, the two ends are fixed in the upper and lower areas of the same Tube Sheet, and divided into two chambers of inlet and outlet with the partition in the tube box. This kind of heat exchanger completely eliminates the thermal stress, the structure is simpler than the floating type, but the tube side is not easy to clean.
The number of tubes is small, the utilization of the tube sheet is not frequent, and the shell side fluid is easy to short circuiting, which is unfavorable to heat transfer. If there is a leak or damage in the tube, the external U-tube can be replaced, while the broken inner tube can not be replaced, only plugged, and one broken U-tube means two broken, so the U-tube easily scrapped.
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Gao Hongbin made the above remarks at the press conference on the special rectification of agricultural product quality and safety held on the 29th. Gao Hongbin said that although we are strictly controlling the production of highly toxic pesticides, we are only exporting and not domestic sales. However, it is realistic to say that if production is allowed, it may be sold domestically. In order to resolutely stop this and stop the production and circulation of highly toxic pesticides, we must control it from the source and we must not reproduce it. A total of only 20 million US dollars in sales, if allowed to produce exports, it is also possible to sell through different channels in the country. So what we mean is that in order to control the source, even if it is exported, it is not allowed to reproduce.
Gao Hongbin said that for the management of highly toxic pesticides, the source must be controlled and the inspection of highly toxic pesticides should be intensified. Since the special rectification, we focused on these five highly toxic pesticides. The country has mobilized nearly 320,000 law enforcement personnel and collected 479 tons of highly toxic pesticides such as methamidophos.
Thirdly, the Ministry of Agriculture announced to the public 29 types of highly toxic pesticides to replace pesticides and 43 matching technologies. If these highly toxic pesticides are not allowed, they must have alternative pesticides. Therefore, the production of alternative pesticides is also very important.
Fourth, the Ministry of Agriculture has launched a nationwide pesticide supervisory and management network linkage covering all provinces' agricultural administrative law enforcement agencies, which has achieved the goal of information sharing for pesticide supervision, joint case investigation and joint inspection and co-examination and co-ordination and multi-provincial linkage. At present, there are indeed many domestic problems with relatively large numbers of pesticides, confusing names, and non-standard labeling. The Ministry of Agriculture is prepared to strengthen the standardization work in this area in the next phase, drafting some rules and regulations, and making it known to the public.
Gao Hongbin, vice minister of the Ministry of Agriculture of China, stated that in order to stop the production and circulation of highly toxic pesticides, we must control it from the source and we must not reproduce it.