How Shell and Tube Heat Exchangers Work (Engineering)

Summary

This video offers an insightful exploration into shell and tube heat exchangers, detailing their structure, operation, and the distinction between single and multi-pass models. It highlights the advantages of these heat exchangers, such as cost-effectiveness, simple maintenance, and suitability for high pressures and temperatures, while also addressing their limitations, including lower efficiency and inflexibility in cooling capacity compared to plate heat exchangers.

Takeaways

• 🔧 Shell and tube heat exchangers are crucial in engineering for transferring heat between two fluids.
• 🏭 The video provides an overview of the main components, design features, advantages, and disadvantages of shell and tube heat exchangers.
• 🌐 The shell, which acts as a pressure vessel, houses the tubes through which one fluid flows, while the other fluid flows in the shell.
• 💧 Both the tube side fluid and the shell side fluid play integral roles in heat exchange, with their flows being designed for maximum efficiency.
• 🔄 The video explains different types of flow designs, including counter flow, cross flow, and parallel flow, each with its own efficiency and application.
• 🛠️ Maintenance of shell and tube heat exchangers is relatively straightforward due to their simple design and the ease of accessing the tubes.
• 💹 They are cost-effective and suitable for high pressures and temperatures, which are advantages over plate heat exchangers.
• 🚫 However, they are less efficient than plate heat exchangers, require more space, and do not allow for easy adjustments to cooling capacity.
• 🔬 The video uses 3D models to illustrate the internal structure and flow paths, enhancing understanding of how these heat exchangers operate.
• 📚 For further learning, the video suggests visiting the provided website for articles and interactive 3D models, as well as considering online courses for deeper knowledge.

Q & A

What is the main topic of the video?

The main topic of the video is the shell and tube heat exchanger, discussing its components, design features, advantages, disadvantages, and how it works.

What are the two main fluids involved in a shell and tube heat exchanger?

The two main fluids involved are the tube side fluid and the shell side fluid, which flow through the tubes and the shell respectively.

What is the purpose of the shell in a shell and tube heat exchanger?

The shell serves as a pressure vessel that houses the tubes and provides a space for the shell side fluid to flow and exchange heat with the tube side fluid.

Why are baffles used in a shell and tube heat exchanger?

Baffles are used to create a path for the shell side fluid to flow around the tubes, promoting turbulent flow which enhances heat transfer and helps prevent fouling.

What is the function of tube sheets in a shell and tube heat exchanger?

Tube sheets are used to hold the tubes in position and seal the inside of the shell to ensure the shell side fluid stays within the space between the two tube sheets.

What is the purpose of turbulators or tube inserts in the tubes?

Turbulators or tube inserts are used to create turbulent flow within the tubes, which increases the heat transfer capacity and helps keep the tubes clean by reducing the buildup of deposits.

What is the difference between a single pass and a multi-pass heat exchanger?

In a single pass heat exchanger, the fluid flows through the tubes once before exiting. In a multi-pass heat exchanger, the fluid makes multiple passes over the tubes, enhancing heat transfer.

What is a U-tube shell and tube heat exchanger?

A U-tube shell and tube heat exchanger is a design where the tubes are bent into a U-shape, allowing for expansion and contraction without stressing the tube sheets.

What are the advantages of shell and tube heat exchangers over plate heat exchangers?

Shell and tube heat exchangers are generally cheaper, simpler to maintain, suitable for higher pressures and temperatures, have less pressure drop, and are less prone to fouling compared to plate heat exchangers.

What are the disadvantages of shell and tube heat exchangers compared to plate heat exchangers?

Shell and tube heat exchangers are less efficient, require more space for maintenance, and do not allow for easy adjustment of cooling capacity like plate heat exchangers do.

What type of flow design is the most efficient for a heat exchanger?

Counter flow design is the most efficient type of flow for a heat exchanger, where the tube side fluid and shell side fluid flow in opposite directions.

Outlines

00:00

🔧 Introduction to Shell and Tube Heat Exchangers

The narrator, John, introduces the topic of shell and tube heat exchangers, explaining that the video will cover the main components, design features, advantages, disadvantages, and the working mechanism of these devices. He clarifies that the video is intended for both those who are familiar with the subject and those who are new to it. John then demonstrates the external appearance of a standard shell and tube heat exchanger, highlighting the shell, which acts as a pressure vessel, and the four main connections for fluid flow. He explains the concept of tube side and shell side fluids, and their respective flow paths within the heat exchanger. The video uses a cross-sectional view to illustrate the internal structure, including the straight tubes for the tube side fluid and the baffles for directing the shell side fluid. John also touches on the broader concept of 'fluids' being applicable to both liquids and gases.

05:02

🛠 Components and Design of Shell and Tube Heat Exchangers

This section delves into the detailed components of the shell and tube heat exchanger, starting with the tube sheets that hold the tubes in place and seal the shell to contain the shell side fluid. Baffles are introduced as structural elements that support the tubes and maintain their alignment. The concept of turbulators or tube inserts is explained, which are designed to induce turbulent flow within the tubes to enhance heat transfer and prevent fouling. The video then shifts focus to the shell side fluid, detailing how it flows around the tubes, facilitated by baffles, to maximize heat exchange and minimize the risk of deposits. A different design, the U-tube shell and tube heat exchanger, is presented, highlighting the U-shaped tubes as a variation from the straight tubes seen earlier. The concept of single pass versus multi-pass heat exchangers is introduced, explaining how the number of times the fluids pass through the exchanger affects its design and efficiency.

10:04

🌡️ Flow Designs and Efficiency in Heat Exchangers

The video discusses various flow designs in heat exchangers, including counter flow, cross flow, and parallel flow, each with its own efficiency and application considerations. Counter flow is described as the most efficient design due to the opposing flow directions of the two fluids, which maximizes heat transfer. In contrast, parallel flow and cross flow designs are explained, with the latter involving fluids flowing at a 90-degree angle to each other. The narrator then compares shell and tube heat exchangers with plate heat exchangers, highlighting the advantages such as lower cost, simplicity, suitability for high pressures and temperatures, and ease of maintenance and leak detection. Disadvantages are also mentioned, including lower efficiency, larger space requirements, and the inability to adjust cooling capacity without major modifications.

15:05

📚 Conclusion and Further Learning Opportunities

In the concluding part, the narrator directs viewers to the website for more detailed information on shell and tube heat exchangers through associated articles and 3D models. He also promotes the platform's online video courses covering a wide range of engineering topics, including heat exchangers, and offers a discount coupon for viewers interested in these courses. The video ends with a call to action for viewers to share, like, and subscribe to the YouTube channel for more content.

Keywords

💡Shell and Tube Heat Exchanger

A shell and tube heat exchanger is a type of heat exchanger that facilitates the transfer of heat between two or more fluids within a closed system. It consists of a shell (a large pressure vessel) and many tubes through which one fluid flows. The other fluid flows over the tubes, allowing heat to be transferred between the fluids. In the video, the narrator explains that this type of heat exchanger is a standard design and goes on to describe its various components and how it operates.

💡Tube Side Fluid

The tube side fluid refers to the fluid that flows through the tubes of the heat exchanger. It is called 'tube side' because it is contained within the tubes, as opposed to the 'shell side' fluid which flows outside the tubes. The video script describes how the tube side fluid enters at the lower left, flows straight up, and then exits, illustrating the flow path within the heat exchanger.

💡Shell Side Fluid

The shell side fluid is the fluid that flows outside the tubes, within the shell of the heat exchanger. It moves around the tubes, facilitated by baffles, and is discharged at the outlet. The video explains that the shell side fluid's movement is crucial for heat exchange, and it contrasts this with the tube side fluid's path.

💡Baffles

Baffles are structural components within the shell of the heat exchanger that guide the flow of the shell side fluid around the tubes. They help create turbulence, which enhances heat transfer efficiency. The video script mentions that baffles are used to maintain the tubes' alignment and support the tube bundle, ensuring efficient heat exchange.

💡Tube Sheets

Tube sheets are large plates that seal the ends of the tubes and hold them in place within the heat exchanger. They create a barrier between the tube side fluid and the shell side fluid, ensuring that the fluids do not mix. The video script describes how tube sheets are essential for maintaining the structural integrity and functionality of the heat exchanger.

💡Turbulators or Tube Inserts

Turbulators, also known as tube inserts, are devices placed within the tubes of a heat exchanger to promote turbulent flow. This turbulence increases the heat transfer rate and helps prevent fouling by keeping the fluid in motion and reducing the chance of deposits forming on the tube walls. The video script explains the role of turbulators in enhancing the performance of the heat exchanger.

💡U-Tube Shell and Tube Heat Exchanger

A U-tube shell and tube heat exchanger is a variation where the tubes are bent into a U-shape, allowing one end of the tube to be fixed while the other end can expand and contract freely. This design helps accommodate thermal expansion and reduces stress on the tubes. The video script introduces this design as an alternative to the straight tube configuration.

💡Single Pass and Multi-Pass

These terms refer to the number of times a fluid passes through the heat exchanger. A single pass means the fluid flows through the heat exchanger once, while a multi-pass design involves the fluid flowing through multiple times, enhancing heat transfer. The video script uses these concepts to explain the efficiency and design variations of heat exchangers.

💡Counter Flow, Cross Flow, and Parallel Flow

These terms describe the directional relationship between the tube side fluid and the shell side fluid in a heat exchanger. Counter flow is when the fluids move in opposite directions, which is the most efficient design. Parallel flow occurs when both fluids move in the same direction, and cross flow is when they move at a 90-degree angle to each other. The video script discusses these flow designs in the context of heat exchanger efficiency.

💡Advantages and Disadvantages

The video script outlines the pros and cons of shell and tube heat exchangers compared to other types, such as plate heat exchangers. Advantages include lower cost, simplicity, suitability for high pressures and temperatures, and ease of maintenance. Disadvantages include lower efficiency, larger size requirements, and fixed cooling capacity. These points are crucial for understanding the practical applications and limitations of shell and tube heat exchangers.

Highlights

Introduction to shell and tube heat exchangers, suitable for those new to the topic or those looking to reinforce their knowledge.

Exploration of the main components that constitute a shell and tube heat exchanger.

Design features of shell and tube heat exchangers, including their advantages and disadvantages.

Visual demonstration of how a shell and tube heat exchanger operates.

Description of the shell as a pressure vessel and its role in fluid dynamics within the heat exchanger.

Explanation of the fluid flow paths for both the tube side and shell side fluids.

Detailed look at the tube side fluid's flow path, including its entry, travel through tubes, and exit.

Discussion on the shell side fluid's journey through baffles and its discharge.

Clarification that 'fluids' can refer to both liquids and gases in the context of heat exchangers.

Introduction to the tube bundle or stack and its role in holding tubes in position.

Explanation of how tube sheets, baffles, and tie rods contribute to the structural integrity of the heat exchanger.

Description of turbulators or tube inserts and their function in enhancing heat transfer and preventing tube fouling.

Analysis of the shell side fluid dynamics, including its path around the tubes and the importance of turbulent flow.

Presentation of a U-tube shell and tube heat exchanger design and its distinctive features.

Differentiation between single pass and multi-pass heat exchangers and their operational implications.

Discussion on counter flow, cross flow, and parallel flow designs and their efficiency.

Advantages of shell and tube heat exchangers such as cost-effectiveness, simplicity, and suitability for high pressures.

Disadvantages of shell and tube heat exchangers compared to plate heat exchangers, including efficiency and space requirements.

Invitation to access further resources and courses for deepening knowledge on heat exchangers.

Encouragement for viewers to engage with the content by sharing, liking, and subscribing.

Transcripts

- [Narrator] Hi, John here and welcome

to another exciting and interesting video

on engineering machinery.

Now, in this video we're gonna be talking

about the shell and tube heat exchanger.

Some of you might think you know a lot about

shell and tube heat exchanges

and that's fine.

Then you can watch this video

and it will just reinforce what you already know.

Some of you might not know anything

about shell and tube heat exchanges

and that's also fine

because you're going to learn a lot in this video.

We're gonna look at all of the main components

that make up a shell and tube heat exchanger.

I'm gonna show you some of its design features,

its advantages and disadvantages

and I'm also gonna show you how it works.

So, let's get started.

Now, this is not how a shell and tube heat exchanger

normally looks in the workplace.

If it was, it would be a lot easier to understand

how it works.

So, let's reset the configurator tool for a moment

and now you can see the shell and tube heat exchanger

as it would normally be in the workplace.

There are different designs of variations

but this one here is quite standard.

So, let's start by looking at the outside

of the heat exchanger.

We've got the shell, it's a pressure vessel

which means it's gonna be pressurized

to match the fluid or the system pressure

that's flowing through it

or specifically flowing through the shell.

Sometimes people refer to the shell also as the housing.

We've also got a front and a rear of the heat exchanger.

Other than that, we've got four main connections

to the heat exchanger.

One, two, three and four.

We have two inlets and two outlets

because we have two fluids that are flowing into

and out of the heat exchanger.

This heat exchanger is called

a shell and tube heat exchanger

because it has a shell

and because within the shell there are some tubes.

Let's take a cross-section.

And we can now see exactly what's happening

inside the heat exchanger.

So, we have a tube side fluid.

The tube side fluid enters here and is discharged here.

We have a shell side fluid

which enters here and goes a long here

and it's discharged here.

The reason we call the tube side fluid the tube side fluid

is because it flows through tubes.

See it comes into the heat exchanger

and once it enters this area,

it has to flow through these tubes

because it's the only place it can go.

Once it flows through the tubes,

it's gonna get to the other end of the tubes.

These tubes are just straight tubes.

The fluid comes out on the lower section here

and re-enters in the top section here.

When the tube side fluid re-enters

through the top section of these tubes here,

it's gonna flow again in a straight line

to the opposite end of the heat exchanger

and it's gonna come out here

and then gonna be discharged or exit the heat exchanger

through the outlet.

That is the flow path of the tube side fluid.

The shell side fluid enters the heat exchanger here

and then it comes through

and it'll pass through a series of baffles

which we'll take a look at in a moment.

And it's gonna be discharged

through the shell side fluid outlet down here.

So, tube side fluid in on the lower left, along here,

straight flow, up, back the other way and then out.

Shell side fluid down through here,

passed all the baffles and then out

on the lower right-hand side.

Although, I refer to fluids in this video,

sometimes it's a little bit easier

to think of them as flowing mediums.

I say that because doctors say,

you should drink a lot of fluids

but realistically a fluid can also be a gas.

Let's have a look at the tube side flowing medium

in a bit more detail.

What I'm actually gonna do,

I'm gonna remove everything but the tubes

so that we can focus on those first.

So, here are our tubes.

The tubes are collectively known as a tube stack

or a tube bundle.

For example, the upper half of the tube bundle

would be all of the tubes above this row here

and the lower half of the tube bundle

would be all of the tubes below this row here.

So, that is our tube bundle or tube stack.

In order to hold the tube bundle

in the correct position,

we're gonna use baffles, tube sheets and also tie rods.

Let's add the tube sheets first.

These are our tube sheets the tube sheets.

The tube sheets are used to first,

hold the tubes in position

and secondly, to seal the inside of the shell

so that the shell side fluid stays within this space

between the two tube sheets.

So, here's one tube sheet,

sometimes known as the real tube sheet.

Here's the front tube sheet

and the shell side fluid is gonna remain in this space.

So, that's the pressure boundary for the shell side fluid.

We wanna fix the tubes in position

using more than just two anchor points.

So, we use baffles as well.

And the baffles just add some extra support

to help keep the tubes in alignment.

You'll also sometimes see tie rods.

And the tie rods are used to connect the tube sheets

or the baffles together

which again adds structural support to the tubes.

Within the tubes,

what you're actually going to have

are turbulators or tube inserts.

You'll push the tube inserts

into every one of these tube holes.

So, for example we'd push a tube insert in here

or a turbulator.

And that turbulator is gonna create turbulent flow.

This turbulent flow helps increase

the heat transfer capacity of the heat exchanger

and also it helps us keep the inside of the tubes clean.

We reduce the likelihood of deposits

building up on the inside of the tubes

because we have turbulent flow

rather than laminar flow.

So, that's everything related to the tube side fluid.

Let's load up some parts now.

So, we can have a look at the shell side fluid.

Now, we've already discussed the tubes

so I think we can remove those.

And we can see now exactly what's happening

with the shell side fluid.

The shell side fluid is entering through here.

It's going round the baffles

and then it is being discharged here.

We can see that around the tubes

there is space for the fluid to flow

because the tubes are not all directly next to each other.

There's a bit of a gap, you can see here.

If I come across, all of these gaps

where my mouse is going now

is where the shell side fluid is going to flow

around the tubes.

We wanna have turbulent flow,

the same as what we had in the tubes.

And in order to get that we use the baffles.

So, the shell side fluid comes in here,

flows around the tubes because of the baffles.

It will exchange heat with the fluid within the tubes

and then it's gonna drop out

of the shell side fluid outlet here.

Once again this turbulent flow increases

the heat transfer capacity of the heat exchanger

which makes it more efficient

but also helps us prevent or reduce

the likelihood of deposits building up

on the outside of the tubes.

Let's load up another 3D model,

so I can show you a slightly different design

of a shell and tube heat exchanger.

So, here is the first design

that I wanna show you.

It's slightly different from what we looked at before.

You can see that externally it looks pretty much the same

but if I show you the tubes

and we reverse that around.

You can see that the tubes themselves

are no longer just straight.

They're actually rounded into a u-shape.

This is actually called

a u-type shell and tube heat exchanger

or a u-tube shell and tube heat exchanger

which is slightly confusing.

But anyway, you can see that the tubes

have this u-shape.

Let's load up a more simple design

cause I just want to explain to you

what a one pass and a multi pass heat exchanger is.

So, here we have a heat exchanger

without a header or a bonnet.

And if we take away the shell,

in fact what we can do we can actually

just take a cross-section.

Can see that this time the tube side fluid

comes in here, flows through the tubes

and exits on this side here.

So, in on the right out on the left.

And what's interesting about this particular heat exchanger

is that the tube side fluid

represents a single pass of the heat exchanger.

You'll often hear people referring to heat exchangers

as either single or multi pass.

The shell side fluid has a multi pass design.

It's passing multiple times over the tubes.

The tube side fluid does not have a multi pass design

because it's traveling directly through the tubes

and then out.

If the tube side fluid was to come in from the right,

come out on the left and then go back around

and then exit on the right,

then this would be a multi pass design.

Because it too, would be passing through

the heat exchanger multiple times.

This heat exchanger would be described as a

multi pass heat exchanger

just because the shell side fluid

or one of the fluids is passing multiple times

over the other fluid.

If the shell side fluid came in from the top

and dropped out at the bottom with no baffles,

then the shell side fluid

would have a single pass design

and so with the tube side fluid.

And we would say, this is a single pass heat exchanger.

That's actually quite rare though.

You don't see that very often

because it's not very efficient.

If you have a look at steam condenses though,

you will see that design.

And generally, whenever you convert a vapor into a liquid

or whenever you're changing the state of something,

you'll often use a single pass design.

People also talk about counter flow, cross flow

and parallel flow.

This particular design is a counter flow design

because the tube side fluid enters on the right

and exits on the left.

And the shell side fluid enters on the left

and is discharged on the right.

So, they're flowing in opposite directions to one another,

right to left and left to right.

That is a counter flow design.

It is the most efficient type of flow design

you can have for a heat exchanger.

If the shell side fluid came in on the right

and exited on the left

then we'd have a parallel flow design

because both the tube side fluid

and the shell side fluid

are flowing from right to left.

If the shell side fluid came in at the top

and which discharged straight out of the bottom

this would be a cross flow design

because the fluids are flowing at a 90 degree angle

relative to each other.

So, different flow designs depend on

what you wanna use the heat exchanger for.

Let's have a talk now

about some of the advantages and disadvantages

associated with this type of heat exchanger.

When we talk about advantages and disadvantages

associated with the shell and tube heat exchanger,

we're often comparing it to the plate heat exchanger

because in the industrial world

we're either using plate heat exchangers

or shell and tube heat exchangers.

Normally, there are some other designs

but those two are the most dominant

within the industrial engineering world.

Now, shell and tube heat exchangers are relatively cheap.

They have a simple design

and they're quite easy to maintain.

They're also suitable for higher pressures and temperatures

compared to plate heat exchangers.

The pressure drop across shell and tube heat exchanger

is less than that of a plate heat exchanger.

It's also easy to find and isolate leaks in the tubes

compared to trying to find and isolated leak

in a plate heat exchanger.

Shell and tube heat exchangers also don't foul

as easily as plate heat exchangers

because they don't have the very fine clearances

that a plate heat exchanger has.

There are however some disadvantages.

They're less efficient than plate heat exchangers.

They also require more space to open

and remove the tubes.

And you can't increase the cooling capacity

of a shell and tube heat exchanger.

With the plate heat exchanger,

you can simply add more plates or remove plates

in order to vary the cooling capacity.

With the shell and tube type heat exchanger,

this is not possible.

If you wanna learn more about shell and tube heat exchangers

then I suggest you go to the website.

I'll put the link in the video description area

and you can read through one of our articles

which will tell you a little bit about

shell and tube heat exchangers

and discuss more of the topics

that we've covered in this video.

If you still wanna learn even more

about heat exchangers after that,

then you can check some of our other associated articles

within our 3D encyclopedia.

You can see here we have an associated article

for a plate heat exchanger.

If you want to access some free interactive 3D models,

then go to the website

and select any model from the 3D models menu

those highlighted green.

And if you wanna take your engineering knowledge

to the next level,

then check out some of that online video courses.

We have over 30 hours of video courses, currently online.

And they cover everything from valves to diesel engines

to pumps to heat exchangers.

I've pasted a discount coupon in the video description area

so if you do decide to purchase any courses,

then be sure to use that discount coupon.

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