What Is Tube In Tube Heat Exchangers

The tube-in-tube heat exchanger is used for efficient heat transfer between two fluids. Tube-in-tube heat exchanger finds their application in industries where heat treatment is subjected to fluids of high viscosity, density, or high fiber or solid particle contamination. In this article, we find the best answer to the question of what is a tube-in-tube heat exchanger and discuss an overview of all you need to know about this type of heat exchanger. Follow this new blog in Linquip to find out more about diesel engine working procedures.

What Is Tube In Tube Heat Exchangers?

Double-tube heat exchangers are designed whereby one tube is concentrically positioned within a larger tube. The double tube composition allows for unrestricted flow of product, making it the ideal heat exchanger for viscous products. The product flows through the inner tube and the service fluid flows through the space between the two tubes, through the surrounding shell.

Tube-in-tube heat exchangers are specially designed for heating or cooling products with low-medium viscosity. The great advantage of the tube-in-tube heat exchangers is to be able to process products with fibers or particles, without the risk of clogging. The large diameter of the tubes ensures their free flow. This heat exchanger is dismountable which makes mechanical cleaning possible. Special construction and corrosion-resistant materials ensure its long service life.

Parts

To answer the question of what is a tube-in-tube heat exchanger, first, let us see what are the different parts of these exchangers. The equipment consists of a single tube mounted inside an outer shell tube, so that the product flows counter-current through the inner tube, with the service medium around it. The diameter of the inner tube is smaller than the outer tube. The inner tube is placed within the outer tube in a concentric circle kind of shape.

The tubular heat exchanger modules are normally connected in series and mounted on a frame. The product medium inside the tube flows in counter current to the service medium. The product tube is corrugated, or it can be smooth. The shell tube is always smooth.

Design

Its unique and compact design prevents thermal fatigue, increases efficiency, and reduces the overall size. It is ideal for high-temperature, high-pressure, and low-flow applications. The layout of tube-in-tube heat exchangers can be customized to fit the available installation footprint or other customer requests. The use of flanged connections allows these tubular heat exchangers to be disassembled to facilitate cleaning and maintenance tasks. The design is being used by major OEMs around the world and in the ever-expanding wholesale replacement market. The simplicity of design and installation makes this product ideal in both markets.

Performance Features

Heat transfer rates to 100,000 BTU/hr (29 kW)
Liquid flows to 10 GPM (38 LPM)
Pressures up to 4,500 psi (310 bar)
Working temperatures up to152°C
Can achieve Reynolds tubular flow
Corrugated internal tube to give added heat transfer area

Working Principle

The working principle of this heat exchanger is simple. A tube-in-tube heat exchanger can achieve a pure countercurrent flow, which allows a temperature crossover to be achieved so that the cold fluid can be heated above the hot fluid outlet temperature. The heated or cooled fluid never comes into contact with the fluid to which it is heating or cooling. The inner and the outer tube each one carries the heated or cooled fluid. This method is known as the indirect heat transfer method.

The fluid in the outer tube enters the tube from the opposite end of the tube to the fluid in the internal tube. This is called counter-flow or contraflow. Tube-in-tube heat exchangers find use in the preheating and cooling sections where a direct steam injection heat exchanger is needed. The heat exchangers on the preheat and cooling sections are by the indirect heat transfer method but the final heating is done by injecting steam directly into the product which is known as the direct steam injection or direct steam infusion.

Types

Three types of the tube in tube heat exchangers for a variety of applications are as follows:

Sanitary Double Tube Heat Exchangers

Sanitary tubes in tube heat exchangers consist of two tubes, an inner and an outer coiled together. These sanitary models are designed to meet the high-quality requirements and hygienic standards of the pharmaceutical industry. There is no risk of cross-contamination between the product and working fluids.

Industrial Double Tube Heat Exchangers

In this design, the inner tube is corrugated for increased heat transfer and reduced fouling. As the name suggests, it is designed for industrial applications

Industrial Double Tube Heat Exchangers with Removable Tube

In this type of heat exchanger, the inner tube is removable which allows for easier and faster inspection/cleaning consequently reducing operational downtime required for high-fouling products. The tube-in-tube concentric geometry makes it easy to work with fluids that contain particles, without having to worry about blockages impeding the flow of product. Special corrugated tubes make it more efficient than similar smooth tube heat exchanger designs.

Advantages

Higher thermal efficiency due to corrugated tubes
Easy to clean
Low maintenance
Robust
All hygienic fittings
High particulate capacities
Resistant to fouling
Flexibility in materials of construction from carbon steel to special alloys
Can handle high-viscosity product
Meets the required industry standard for CIP cleaning. Minimum 1.5 meters per second velocity

Disadvantages

Need more space due to the reduced heat exchange surface area

Applications

The tube-in-tube heat exchangers are typically applied for:

Multi-phase fluids and slurries
High thermal stress
Steam condensing
Seal cooling
Liquid/gas
Sampling
WFI (Water For Injection)

Tube-in-tube heat exchangers are specifically designed for use in water-cooled condensers, water chillers, paper industry, and water source heat pumps.

Here are some examples of the tube in tube heat exchangers uses in different fields:

Industrial

Palm Oil
Fine Chemicals
Solvents
Petrochemicals
Process Water

Pharmaceutical

Lotions
Creams
Gels
Cosmetics

Chemical

Heating of pastes in the production of PET pellets

Food

Prepared food
Vegetables
Fruit puree and concentrates
Fruit Dice, rounds, and slices
Fruit jams and marmalades
Soups
Baby foods
Mayonnaise
Soy
Puddings and desserts
Whey, casein, and lactose products
Yogurt and cultured milk
cream and ice cream
Sauces
Beverages

Environmental

Sewage treatment
Cooling or heating of wastewater
Anaerobic digestion (AD) and biogas
Pasteurization of sludge

So, there you have every single fact to the question of what is a tube-in-tube heat exchanger. If you enjoyed this article in Linquip, let us know by leaving a reply in the comment section. Is there any question we can help you with? Feel free to sign up on our website to get the most professional advice from our experts