Professional guide to the working principle, type classification, selection and maintenance of tube and tube heat exchangers

Tube and tube heat exchangers are one of the most widely used general heat exchange equipment in chemical, pharmaceutical, food, energy and other industrial fields. Its core structure consists of a shell, a tube bundle, a tube plate, a head, a baffle, and connecting pipes. Heat transfer is achieved through the orderly flow of two fluids, the tube side and the shell side. With its obvious advantages such as simple structure, strong durability, wide application range, and easy maintenance and repair, the tube and tube heat exchanger has become a standard configuration in many industries such as petroleum refining, fine chemicals, biopharmaceuticals, dairy beverages, and cogeneration.

Structure and working principle

The working principle of the tube heat exchanger is based on the basic law of heat transfer between two fluids through a solid wall. Inside the heat exchanger, one type of fluid flows in the tube, which is called the tube-side fluid, and the other type of fluid flows in the tube shell side, which is called the shell-side fluid. The two fluids exchange heat through the tube wall of the tube bundle.——The hot fluid transfers heat to the tube wall, and the cold fluid absorbs heat from the tube wall. The core design of the tube and tube heat exchanger is to maximize the heat transfer area while minimizing flow resistance.

Main type classification

The tube plates at both ends of the fixed tube plate heat exchanger are rigidly connected to the shell. It has the simplest and most compact structure and is suitable for working conditions where the shell side fluid is clean and does not require mechanical cleaning. The tube plate at one end of the floating head heat exchanger can float freely in the shell, which can effectively eliminate the stress caused by thermal expansion and is suitable for situations where the temperature difference between the tube side and the shell side is large.UType tube heat exchanger adoptsUType tube bundle requires only one tube plate and has high design flexibility. The stuffing box heat exchanger realizes the free expansion and contraction of the tube bundle through the stuffing box.

Key points for selection

In the selection process of tube and tube heat exchangers, multiple factors such as process parameters, medium characteristics and economy need to be comprehensively considered. The primary parameters include design pressure, design temperature, allowable pressure drop, heat transfer, and fluid flow rate and inlet and outlet temperatures. For highly corrosive media, all metal parts in contact with the fluid need to be made of corresponding corrosion-resistant materials, such as stainless steel, titanium, Hastelloy, etc.

Routine maintenance

Preheat slowly before driving to prevent seal leakage caused by temperature difference stress. During operation, the heat transfer efficiency and pressure drop changes of the heat exchanger should be regularly monitored. When the heat transfer coefficient drops significantly, the machine needs to be shut down for chemical cleaning or physical flushing. For media prone to scaling, it is recommended to perform offline cleaning every three to six months of operation. Instrument accessories such as safety valves, pressure gauges and thermometers of the heat exchanger should be calibrated periodically to ensure accurate and reliable monitoring data.