Shell and Tube Heat Exchanger Design Technical Requirements

This article is about Shell and Tube Heat Exchanger Design Technical Requirements in process industry, U Tube Heat Exchanger and types of shell and tube heat exchanger of chemical plants and oil & gas industry.

What is Shell and Tube Heat Exchanger?

A shell and tube heat exchanger is a type of heat exchanger widely used in various industries for transferring heat between two fluids. It consists of a shell (outer vessel) with a bundle of tubes (inner vessel) running through it. The two fluids, often at different temperatures, flow through separate paths—the hot fluid passing through the tubes, and the cold fluid surrounding the tubes in the shell. Heat is transferred between the two fluids through the tube walls, enabling efficient heat exchange.

The design of a shell and tube heat exchanger allows for a large surface area for heat transfer, ensuring effective thermal performance. The shell and tube configuration also allows for flexibility in handling different flow rates, pressures, and temperature differentials. This type of heat exchanger is commonly used in applications such as refrigeration, power generation, chemical processing, and HVAC systems.

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Shell and Tube Heat Exchanger Design Technical Requirements

Following section, we explain about Shell and Tube Heat Exchanger Design and technical requirements you need for process industry.

a. Sizing Criteria

1. All condensing heating fluids will be throttled going to the heat exchanger. Condensate will drain by gravity to a drain drum with level control. Provide pumps where needed to return low-pressure condensate. Provide condensing pressure indication in the control room.

2. Fouling resistance will conform to TEMA unless specified otherwise.

3. The minimum fouling factors that will be used for utility services are given below:

4. Where practical, critical exchangers in fouling service shall be provided with an installed spare.

5. Cooling water shall not be throttled to achieve heat transfer control; instead process side temperature control shall be achieved by providing an exchanger by-pass control on the process side. (Subject to Company’s Approval).

6. Check valves shall be provided in low-pressure steam lines to re-boilers and exchangers to prevent header contamination in case of tube leakage.

b. Nozzles

1. The minimum size of all process and utility vent and drain nozzles will be 2 inch. Cold blow down nozzles will be 1 – ½ inch.

2. Temperature and pressure connections will be located in adjacent piping unless otherwise specified in data sheet.

3. Couplings for pressure gauges and thermowell connections shall not be supplied on exchanger nozzles unless otherwise specified on data sheet.

4. Thermowell connections, if specified, will be 1-1/2 inch flanged.

5. Nozzle sizes of 2-1/2, 3-1/2, 5 and 7 inch are not to be used.

c. Isolation and Valving

1. Block valves with slip blinds will be provided for exchangers in fouling service, except for the Ethylene Furnace Transfer Line heat exchangers.

2. The steam inlet to re-boilers will be equipped with a check valve or other back flow prevention device.

3. Block valves shall be installed in the steam inlet and condensate return from all exchangers in hydrocarbon service. Additionally, the steam inlet to re boilers operating at a higher pressure than the steam header shall also be equipped with a check valve.

4. Block valves shall be provided in the water inlet and outlet piping of exchanger units.

d. Layout requirement:

All heat exchangers shall have free space for easy maintenance and head channel / tube bundle removal and connected piping, shall also be considered for all heavy equipments & valves.

What are types of shell and tube heat exchanger?

There are several types of shell and tube heat exchangers, each with its own design and configuration to suit specific applications. Here are some common types:

1. Fixed Tube Sheet Heat Exchanger: This is the simplest and most common type of shell and tube heat exchanger. The tube sheets are fixed, meaning the tubes are permanently attached to the shell. It is suitable for applications with low temperature and pressure variations.
2. U-Tube Heat Exchanger: In this design, the tubes are bent in a U-shape, allowing both ends of the tubes to be fixed to the same tube sheet. This configuration facilitates thermal expansion and contraction of the tubes and is commonly used when one fluid has a higher temperature change than the other.
3. Floating Head Heat Exchanger: This design allows for differential thermal expansion between the shell and tube bundle. One end of the tubes is fixed to the tube sheet, while the other end is attached to a floating head that can move to accommodate temperature changes. This type is suitable for high-pressure and high-temperature applications.
4. Double Tube Sheet Heat Exchanger: This design uses two tube sheets with an air gap in between. It provides an additional layer of safety by preventing cross-contamination between the two fluids in case of tube failure.
5. Multi-Shell Pass Heat Exchanger: This type consists of multiple shells arranged in series or parallel. It allows for increased heat transfer surface area and can handle large flow rates or difficult-to-handle fluids.

The selection of the appropriate type depends on factors such as the operating conditions, fluid properties, space limitations, and required thermal performance.

U Tube Heat Exchanger

A U tube heat exchanger is a type of shell and tube heat exchanger in which the tubes are bent in a U-shape. The U-tube configuration allows both ends of the tubes to be fixed to the same tube sheet.

The U tube design offers some advantages, such as:

1. Thermal Expansion: The U-shape allows for differential thermal expansion between the shell and tube bundle, accommodating temperature changes without excessive stress on the tubes.
2. Compact Design: The U-tube configuration offers a more compact design compared to straight tube heat exchangers, making it suitable for applications with space constraints.
3. Easy Maintenance: The U-tube design allows for easy inspection and cleaning of the tubes. The tube bundle can be easily removed for maintenance or replacement.
4. Versatility: U tube heat exchangers can handle both liquids and gases and are suitable for a wide range of applications and industries, including HVAC systems, power plants, and chemical processing.

However, there are also some limitations to consider:

1. Limited Tube Length: The U-bend in the tubes restricts the maximum tube length, which may affect heat transfer efficiency in certain applications.
2. Higher Pressure Drop: The U-bend can result in a higher pressure drop compared to straight tube heat exchangers, which may require higher pumping power.
3. Tube Cleaning Challenges: The U-bend can make it more challenging to clean the tubes thoroughly, potentially leading to reduced heat transfer performance over time.

Overall, the selection of a U-tube heat exchanger depends on factors such as the specific application requirements, fluid properties, space availability, and maintenance considerations.

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FAQs about shell and tube heat exchanger