Shell and Tube Heat Exchanger

Heat Capacity
Heat exchangers have to be able to handle a wide range of temperatures, varying by application. Their ability to deal with extreme temperatures helps maintain production and keep operations moving. Shell and tube heat exchangers have a high temperature working capacity and can be adapted to fit any conditions.

Pressure
The high pressure of a shell and tube heat exchanger requires the use of thick materials that makes the exchanger very heavy or too expensive if nickel alloys are used. High pressure creates major problems and leads to a loss of production. The shell and tubes of shell and tube heat exchangers are tested and designed to withstand the extremes caused by pressure variances and adhere to the Codes of the ASME and PED.

Pressure Loss
Pressure loss is a loss of energy and causes downstream pressure loss that slows the velocity of flow. Shell and tube heat exchangers are designed to deal with pressure loss and keep it to a minimum within the design criteria. There are several variables that are affected by pressure loss, one of them being a fouling of the shell and tubes. With the minimal pressure loss allowed by shell and tube heat exchangers, this problem is eliminated.

Adjustments
The design of shell and tube heat exchangers can be adjusted for adaptation to any production process. Changes in pipe diameter, number of pipes, length of pipes, pipe pitch, and pipe arrangement can be altered to specifically fit the needs of an application.

Thermal Expansion
The multi-tube design of shell and tube heat exchangers allows for thermal expansion between the tubes and shell. This configuration gives the heat exchanger the ability to handle flammable and toxic fluids.

Let’s break down how heat exchangers work. Two fluids at different temperatures flow through the heat exchanger. One, the tube-side fluid, flows inside the tubes. The other, the shell-side fluid, goes around the outside of the tubes inside the shell. The tube walls separate the fluids, so they never mix, but heat can jump across from the hot fluid to the cold, thanks to our good old pal, thermal conductivity.

Heat Transfer
Heat transfer in a shell and tube heat exchanger occurs primarily via two modes: conduction (the heat travelling through the tube wall) and convection on both sides (the heat being carried away by the moving fluids). The efficiency of heat transfer is influenced by stuff like the process fluids used, the total surface area of the tubes, and the velocities of the fluids, among many other factors.

Fluid Flow
In the tubes and the shell, fluids can flow in a smooth or turbulent manner. Turbulent flow is actually a good thing in heat exchangers because it mixes the fluid against the tube walls, which helps transfer more heat. Thermal Design Engineers tweak things like tube counts and baffle configurations to improve fluid velocity, turbulence, and maximize heat transfer relative to exchanger cost.

Thermal Efficiency
You want your heat exchanger to be efficient, meaning you get as much heat as possible from the hot side to the cold side without oversizing the exchanger. Factors like the design of the exchanger, the temperature difference between the fluids, and the properties of the fluids themselves all play into how efficient and compact an exchanger can be.

Outlet Nozzles
Once the fluids have exchanged heat, they’ve got to exit the heat exchanger. The tube-side fluid may leave from the same end it entered (in a multi-pass exchanger like a BEU type) or the opposite end (in a single -pass system typical of a NEN or BEM TEMA type). The shell-side fluid will usually exit at the top if being heated, or the bottom of the shell if being cooled, but it depends on the process design.

Co-Current and Counter Flow
There are two common arrangements for the flow of fluids in a shell and tube heat exchanger: co-current and counter flow. In co-current flow, both fluids go the same direction. In counter flow, the fluids head in opposite directions. Counter flow is typically more desireable because it can achieve greater heat transfer due to a larger temperature difference between the fluids. Quite often, shell & tube heat exchangers have a mix of co-current and counter-current flows due to the multiple tube-side passes inside the shell.

Regular Inspection: Conduct routine visual inspections to check for signs of corrosion, fouling, leaks, or any physical damage. Inspect the tubes, tube sheets, shell, gaskets, and seals.

Cleaning: Fouling is a common issue that reduces heat transfer efficiency. Depending on the fluids being processed, fouling can occur due to scaling, deposits, or biological growth. Cleaning methods may include chemical cleaning, mechanical cleaning (tube brushing), or high-pressure water jetting.

Tube Integrity: Check the integrity of the tubes by conducting non-destructive testing (NDT) methods such as ultrasonic testing or eddy current testing. Look for signs of tube wall thinning or corrosion.

Seal and Gasket Inspection: Inspect gaskets and seals for wear, damage, or leakage. Replace any damaged or worn-out gaskets and seals.
 

Fluid Analysis: Regularly analyze the properties of the fluids circulating through the heat exchanger. This can help identify potential issues, such as corrosion, scaling, or contamination.

Tube Bundle Cleaning: Periodically remove the tube bundle and clean it thoroughly to remove fouling. This may require shutting down the heat exchanger, so plan for maintenance during scheduled shutdowns.

Fluid Velocity: Ensure that the fluid velocity inside the tubes is within the recommended range to promote efficient heat transfer and avoid erosion or vibration-related issues.

Insulation: Check the insulation around the heat exchanger for damage or deterioration. Proper insulation helps maintain temperature control and energy efficiency.

Supports and Alignment: Inspect supports, brackets, and alignment to ensure the heat exchanger is properly secured and aligned. Vibrations or misalignment can lead to damage over time.

Our factory covers an extensive area and is equipped with advanced production equipment, including 14 flat vulcanizing machines, and the maximum heating plate size can be adapted to various production requirements. The company has more than 750 sets of molds of various models, which can meet the specifications of most heat exchanger brands in the market.