Fixed tube heat exchanger consists of tube bundle, tube plate, shell, head, folded plate, etc. Tube bundle ends fixed in the tube plate, the tube can be expanded (the inner hole of the tube with mechanical expansion, so that the tube wall from the inward to outward extrusion and fixed in the tube plate) or welded to the tube plate. The tube bundle is placed within the tube shell, with headers and flanges fixed at both ends. In this way, one fluid flows from the inside of the tube and the other from the outside. The space between the two heads and the tube plate is used to distribute or collect the fluids inside the tube. The two fluids do not mix with each other, but only exchange heat through the tube wall.
Advantages: simple and compact structure, high pressure resistance, low cost and easy to clean the tube side.
Disadvantages: Risk of blockage when the tube is damaged or needs to be replaced.
When the difference between the wall temperature of the tube bundle and the shell or the coefficient of linear expansion of the material is large, a large thermal stress will be generated in the shell and the tube bundle. A flexible compensation ring (also called expansion joint) should be installed on the shell to reduce the thermal stress.
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On August 5th, 2011, the Qingling original refrigerated truck debuted in Shanghai. This model is a strategic high-end refrigerated truck jointly developed by Isuzu and Qingling, marking that Qingling Company formally entered into the production of high-end refrigerated special vehicles.
According to reports, with the increase of national strength, China has become the world's largest producer of fruits, vegetables, and meat, and a major consumer. Fast-frozen foods have increased by an average of 20% per year, with fruit production of 80 million tons and vegetable production of 300 million tons. At present, the status quo of cold-chain logistics transportation cannot meet the development needs. In Japan, Europe and the United States, more than 80% of agricultural products are transported by refrigerated trucks, while China is less than 20%. The “Development Plan for Cold Chain Logistics of Agricultural Products†formulated by the National Development and Reform Commission clearly stated that by 2015, the refrigerated transport rate of fruits and vegetables, meat, and aquatic products in China will increase to 30%, 50%, and 65%, respectively. 
The key to improving the refrigerated transportation rate is to simultaneously increase the manufacturing level and service level of domestic refrigerated special vehicles. The current production of refrigerated special vehicles is due to the fact that a considerable part of the company’s production scale is small, and the main components of the chassis and cold machines are from the outside. Assembled procurement, the overall product quality is low, the cost is high, and there is no perfect after-sales service system, resulting in a significant gap between the manufacturing and service levels of refrigerated trucks and developed countries.
As the only manufacturing company in China that has introduced the full range of Isuzu technology in Japan, Chongqing Qingling Company aims at the backwardness of China's cold chain transportation, relying on its Isuzu original factory to produce chassis with high quality, low fuel consumption, low maintenance cost, and medium price. The Isuzu Refrigerator Partners Denso, Carrier and other brand cold-pressing companies invested 200 million yuan in Chongqing to build a refrigerated special-purpose vehicle production line, and successfully developed Isuzu original plants ranging from 3 tons to 15 tons in various deadweight tonnages. Refrigerated truck. 
Compared with similar domestic products, Qingling original refrigerated truck highlights three unique advantages:
Firstly, the status quo of the disjoint quality technology of the chassis, refrigerator, and car body has been completely solved, and the Trinity R&D system and matching design have been implemented. This provides a truly high-end product for the domestic refrigerator car market. In the field test of the conference, Isuzu After the refrigerator car started for half an hour, it lowered the temperature of the cabin from 30°C to -18°C and won a cheering voice from the guests.
The second is to thoroughly solve the status quo of the disconnection between the chassis, the refrigerator and the car body. The more than 200 Qingling 4S stores throughout the country provide one-stop lifelong service for customers, eliminating the need for customers in the past. The back and forth labor between the refrigerator factory and the chassis factory suffers. 
Third, the price and delivery time have obvious advantages. Because the chassis, the car body, and the cold storage system are all produced in one place, the logistics and manufacturing costs are greatly saved, and the starting point of the production scale is high, so that the price of the Qingling refrigerator car can be lower than that of the market with the same specifications. Low 10%-20% positioning, delivery cycle is shortened by more than 30%.
Qingling original refrigerated trucks rely on the advantages of technology, service and cost-effectiveness, and will undoubtedly build a new development pattern for the majority of cold-chain logistics transportation users, and become the emerging main force to improve the quality of urban life.