Shell and tube heat exchangers

Shell and tube heat exchangers are among the most widely used types of heat exchangers in the oil and gas industry. Their simple design, ability to withstand high pressures and temperatures, and versatility in various applications make them extensively utilized in industrial processes.

Applications of Shell and Tube Heat Exchangers

Shell and tube heat exchangers are extensively used in the oil and gas industry for heat transfer between two fluids. These exchangers consist of a bundle of tubes housed within a larger shell. Key applications include:

Cooling and Heating Fluids: Used in refineries and petrochemical plants to cool crude oil, petroleum products, and various gases. They are also employed to heat crude oil before distillation.
Heat Recovery: Recovering heat from hot streams to cold streams to enhance energy efficiency and reduce operational costs. For example, recovering heat from exhaust gases to preheat air entering boilers.
Heat Exchange in Various Processes: Used in chemical processes in refineries and petrochemical plants to transfer heat between reactants and reaction products.
Equipment Cooling: Cooling sensitive equipment such as compressors, turbines, and large engines used in the oil and gas industry.
Preheating Feedstock: Preheating feedstock to chemical reactors and refining units to improve efficiency and chemical reactions.
Gas Separation and Fractionation: In natural gas processing units for cooling and separating components like methane, ethane, propane, and butane.

Overall, shell and tube heat exchangers are considered essential and critical equipment in many sectors of the oil and gas industry due to their simple structure, high-pressure and temperature tolerance, and high efficiency.

Types of Shell and Tube Heat Exchangers

Shell and tube heat exchangers can be categorized based on various criteria:

Based on Fluid Flow Arrangement

Parallel Flow: Both fluids flow in the same direction.

Counter Flow: Fluids flow in opposite directions, generally providing higher efficiency.

Cross Flow: Fluids intersect each other perpendicularly.

Based on Tube Passes

Single Pass: Fluid passes through the tubes once from one end to the other.

Two Pass: Fluid passes through the tubes twice, usually by reversing flow with a tube sheet.

Multi Pass: Fluid passes through the tubes multiple times for increased heat transfer.

Based on Installation and Application

Power Plant Heat Exchangers: Designed for power generation plants.

Refinery Heat Exchangers: Designed for oil and gas refineries.

Marine Heat Exchangers: Designed for marine environments and ships.

Based on Tube Arrangement

Straight Tube: Tubes extend straight from one end to the other.

U-Tube: Tubes are bent into a U-shape, with both ends in the same tube sheet.

Based on Shell Structure

Single Shell Pass: Fluid passes through the shell once from one end to the other.

Multi Shell Pass: Fluid passes through the shell multiple times.

Based on Design Standards:

TEMA Standards: Includes TEMA R (for refinery and oil services), TEMA C (for commercial services), and TEMA B (for general services).

These categorizations help in the precise selection and design of shell and tube heat exchangers based on specific industry needs and applications.

Structure and Design of Shell and Tube Heat Exchangers

Shell and tube heat exchangers consist of a shell and a bundle of internal tubes. In this design, one fluid flows through the tubes, while the other flows around the tubes within the shell, facilitating efficient heat transfer between the two fluids.

Thermal Design

Thermal Calculations: Include determining the required heat transfer area, length, number of tubes, and type of flow (counterflow, parallel flow, or cross flow).
Design Software: Tools such as HTRI and Aspen HYSYS are used for simulation and optimization of thermal design.

Key Components

Shell: Typically cylindrical and holds the external fluid.
Tubes: Made from corrosion-resistant metals and carry the internal fluid.
Tube Sheets: Secure the tubes at both ends and connect them to the shell.
Heads or Bonnets: Located at both ends of the shell, they direct the flow of fluids.
Baffles: Vertical or horizontal plates inside the shell that guide and enhance the flow of the external fluid.

Materials Used in Shell and Tube Heat Exchangers

Material selection for shell and tube heat exchangers depends on operational conditions such as temperature, pressure, and the corrosiveness of fluids:

Stainless Steel: Suitable for many applications due to high corrosion resistance and temperature tolerance.
Nickel Alloys: Used in highly corrosive environments and high temperatures.
Copper and Copper Alloys: Ideal for applications requiring high thermal conductivity.
Titanium: Used in highly corrosive environments like seawater and strong acids.

Installation and Commissioning of Shell and Tube Heat Exchangers

Proper installation and commissioning are crucial for optimal performance:

Installation Location: Heat exchangers should be installed in locations allowing easy access for maintenance.
Supports: Strong, stable bases are required to support the weight of the exchanger and fluids.
Connections: Tube connections must be done accurately to prevent leaks.
Gaskets: Proper gaskets are necessary for sealing connections and preventing fluid leaks.
Testing: Exchangers should undergo pressure and leakage tests before operation, as well as performance tests to ensure efficient heat transfer.

Maintenance of Shell and Tube Heat Exchangers

Regular and proper maintenance is essential to maintain performance and extend the lifespan:

Periodic Inspection: Regular inspections to identify faults, corrosion, and fouling.
Cleaning: Deposits and contaminants should be regularly removed to maintain thermal efficiency. Chemical cleaning for mineral and organic deposits, and mechanical cleaning for solid particles.
Part Replacement: Worn-out components such as tubes and gaskets should be replaced promptly with high-quality, standard-compliant parts.

Heat Exchangers construction

Petro structure Company is a manufacturer of heat exchangers such as shell and tube exchanger, plate exchanger and air exchanger. This complex has the possibility of building heat exchangers by using the expert forces and required equipment. Contact our experts for more information.

References

“Perry’s Chemical Engineers’ Handbook” edited by Don W. Green and Robert H. Perry
“Chemical Engineering Design” by Gavin Towler and Ray Sinnott
“Heat Exchanger Design Handbook” by K. M. V. V. Prasad
“Heat Exchangers: Selection, Rating, and Thermal Design” by Sadik Kakaç, Hongtan Liu, and Anchasa Pramuanjaroenkij

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