Do you know Fixed Tube Sheet Heat Exchangers?

Fixed tube sheet heat exchangers are shell and tube heat exchangers where the tube sheets at both ends of the tube bundle are fixedly connected to the shell by welding.

The welded tube sheets can also function as flanges, which are bolted to the tube box flanges.

Advantages include simple structure and minimal shell inner diameter required to ensure equal heat transfer surface area.

Disadvantages include significant thermal stress generated when there is a large temperature difference between the shell-side and tube-side media, leading to pull-out and rupture at the tube to tube sheet joint, resulting in leaks or tube instability. Maintenance and shell-side cleaning are also inconvenient. While widely used in general applications, they are limited by temperature differences.

Fixed tube sheet heat exchangers consist of tube sheets at both ends and a shell. Due to their simple structure, they are widely used.

Fixed tube sheet heat exchangers are energy-saving devices for heat transfer between materials and are commonly used in industries such as petroleum, chemical, petrochemical, metallurgy, power, light industry, and food processing. In oil refining and chemical plants, heat exchangers account for approximately 40% of the total equipment and 30%-45% of the total investment. With the development of energy-saving technologies and the continuous expansion of their application areas, the use of heat exchangers for high- and low-temperature heat energy recovery has brought significant economic benefits.

Fixed tube sheet heat exchangers consist of components such as tube boxes, shells, tube sheets, and tubes. They have a compact structure, a large number of tubes, a larger surface area for the same diameter, and are relatively simple to manufacture.

The structural feature of a fixed tube sheet heat exchanger is that a tube bundle is arranged in the shell. The tubes at both ends of the tube bundle are fixed to the tube sheet by welding or expansion joints. The tube sheet is directly welded to the shell. The inlet and outlet tubes of the shell side are directly welded to the shell. The outer circumference of the tube sheet and the end flanges are fastened with bolts. The inlet and outlet tubes of the tube side are directly welded to the end caps. Several baffles are arranged inside the tube bundle according to the length of the heat exchange tubes. This type of heat exchanger can be divided into any number of passes using baffles.

Fixed tube sheet heat exchangers are widely used in engineering due to their simple structure, low manufacturing cost, convenient tube-side cleaning, multi-pass tube side, and double-pass shell side. They offer a wide range of specifications. However, shell-side cleaning is difficult, making them unsuitable for dirty or corrosive media. When the expansion difference is large, expansion joints can be installed on the shell to reduce thermal stress caused by the temperature difference between the tube and shell sides.

The characteristics of fixed tube sheet heat exchangers are:

1. Minimal bypass seepage;

2. Fewer forgings used, resulting in lower cost;

3. No internal leakage;

4. Heat transfer area 20%–30% larger than floating head heat exchangers.

Heat exchangers can be classified according to their structural form as: fixed tube sheet heat exchangers, floating head heat exchangers, U tube heat exchangers, and stuffing box heat exchangers.