U-Tube exchangers

The diagram illustrates the design of U-tube heat exchangers, explaining the origin of their name. The tube bundle is composed of continuous tubes bent into a “U” shape and secured to the shell using a tube sheet (shown at the top). The cooling fluid flows through the U-shaped tubes from the top half of the inlet, then exits from the bottom half. This bend allows for thermal expansion of the fluids without requiring any expansion in the joints, as the bent portion floats freely in the shell, providing space for expansion/contraction. These exchangers perform exceptionally well when there are significant temperature differences and expansion is expected. The structure of these exchangers can also be designed with multiple passes and multiple passes.

The ends of all tubes are connected to the slope tube, and in fact, its function is to restrain and seal the tubes with respect to each other.
The material of the tube sheet is also related to the fluid, pressure, temperature, properties, and corrosiveness, which is mainly made of ST52 or ST37 carbon steel in air conditioning applications.

The thickness of the tube sheet is also determined based on the tube diameter, the number of tubes, and the corresponding pressures inside and outside the shell based on various standards, including TEMA and API 660.

Inside the shell, plates called baffles are installed to act as fluid flow directing plates, creating turbulent flow in the fluid flowing inside the shell and maximizing heat transfer efficiency.
In a shell and tube heat exchanger with baffles (flow directing plates), the flow of fluid towards the shell is directed crosswise to the tubes between two adjacent baffles. The material of the baffles used varies depending on the type of fluid, corrosion, temperature, and pressure, but in air conditioning applications, PTFE with a thickness of 5 to 10 mm is commonly used.

The material and thickness of the baffles depend on various factors. The type of fluid or medium inside the shell, coefficients and temperature differences, the corrosiveness of the fluid, and more are factors that influence the type and thickness of the baffles.

Installation of a half coupling on the exchanger for draining the fluid inside the shell and the fluid inside the tubes, as well as venting the exchanger.
Precise welding of the outer shell.
Seamless tubes are used in the coil construction.
Welding with MTIG and MAG/MIG equipment.
Construction of the exchanger with a very strong body and completely sealed with anti-rust internal and external surfaces and insulation of its shell with 19 mm thick foam.
Rolling and welding of tubes to the tube sheet in accordance with ASME and TEMA standards.
Design of exchangers with easy assembly and disassembly of parts for servicing and maintenance.
Design of the exchanger based on technical information and requirements provided by the customer and in the best and most suitable way in terms of design and price.
Body made of stainless steel, carbon steel, or brass, and internal tubes made of copper, brass, stainless steel, or carbon steel (depending on the type of fluid and corrosion of the fluid flowing through it).

To maximize efficiency, the heat transfer surface between the two fluids (which are the tubes) must be increased as much as possible. Therefore, a large number of tubes made of copper, steel, etc., are used. Most shell-and-tube heat exchangers are designed with 1, 2, or 4 passes. The number of passes refers to the number of return paths that the fluid takes from inside the tubes towards the outlet. For example, in a single-pass design, the fluid enters the tubes from one side and exits directly from the other side. In a two-pass design, after entering the tubes and reaching the end, the fluid changes direction by 180 degrees and exits from the same inlet side.