Factors That Determine Fluid Allocation in Shell and Tube Heat Exchangers

With the global concerns on the greenhouse effect, industries have adopted various waste recovery strategies. Towards this end, factories are using the shell and tube heat exchanger design to regulate excess heat. The phenomenon of heat transfer using this design has proven to be revolutionary.

Using a heat exchanger is an environmentally friendly way of curbing wasted gas. A heat exchanger is a device used for heat transfer from one fluid to another. Based on the temperature requirements for your heat exchanger, you can transfer heat between a solid surface and a liquid.

If the particles are in thermal contact, a heat exchanger can transfer heat from solid particles to fluids. The shell and tube heat exchanger design is popular in the chemical process industries. This article helps you understand the various factors affecting fluid allocation in a shell and tube heat exchanger.

1. Determine Fluid Pressure

It is essential to decide on where to place high-pressure fluids when constructing a shell and tube heat exchanger. Thicker metal walls should contain high-pressure fluids. Fluids at extreme pressures are best placed on the tube side because of the increased metal thickness.

The tubes are smaller in diameter compared to the shell hence can withstand high pressure. It is easier to make the tubes resist high forces rather than the entire shell. The metal thickness on the tube side has a higher pressure-rating than the same metal thickness on the shell.

If the shell side needs to be designed to accommodate high pressure, the wall thickness will increase, making the design uneconomical. Building thicker metal tubes requires lesser materials than building a thicker metal shell. Keeping in mind the pressure variation of fluids will guide you when designing your heat exchanger.

2. Check Fouling Factors for Each Fluid

Taking into account the fouling of fluids can have a high impact on the heat transfer rate in a heat exchanger. Generally, fouling influences the overall function of the shell and tube heat exchanger. Fouling also affects the ease of cleaning a heat exchanger.

When choosing fluids that foul, consider the heat exchanger configuration you have chosen to use. Utilizing a fixed tube requires putting a clean fluid on the shell side. Dirty fluids are likely to cause fouling and should go on the tube side.

A fluid susceptible to fouling should go on the tube side. Typically, tubes are easier to clean as opposed to the shell. The shell is harder to clean mechanically, and chemical cleaning is usually the only option.

3. Materials Used to Construct the Heat Exchanger

It is crucial to consider the materials used in constructing the heat exchanger and the nature of fluids you intend to use. Fluids that are corrosive and lethal are primarily on the tube side. Corrosion fluids can cause a certain amount of damage to the heat exchanger.

To reduce this risk, choose corrosion-resistant alloys and materials. Fewer corrosion alloys are needed if the corrosive fluid is on the tube side since it has less metal than the shell side. Only the tubes, tube sheets, heads, and channels require the corrosion-resistant alloys.

If you put a corrosive fluid on the shell side, you would need to use the corrosion-resistant materials on the shell and tube heat exchanger.

4. Fluid Velocity

Fluids with high velocity such as water or propylene glycol for cooling are usually on the tube side. High speeds increase the heat transfer coefficient but are associated with potential pressure drop. Another advantage of high speeds is reduced tube fouling, which increases the thermal transfer as well.

The speed should not be so high that it would cause tube corrosion. A plastic cover is used on the tube input to reduce corrosion.

To Sum Up

Knowing the fluids you intend to use in your shell and tube heat exchanger can help guide the construction process. The goal is to obtain heat transfer coils with high heat transfer coefficients.

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