Skip to content

Types of Heat Exchangers ?

TYPES OF HEAT EXCHANGERS

 

A typical refinery or chemical facility utilizes many different types of heat exchangers. The type chosen for use by that particular site for a particular use depends on many factors. Typical of those factors is the cleanliness of the fluid to be heated or cooled, the temperature range of the fluids to be heated or cooled, the viscosity of the fluid to be heated or cooled, the operating pressure of the fluid to be heated or cooled, the corrosion aspects of the fluid to be heated or cooled, and several other factors. These factors determine that plant’s selection of the heat exchanger type to utilized to perform the needed task at hand.


What are the Different types of Heat Exchangers
?

 

Let’s take a look at the Different types of heat exchangers and its applications. Below is a listing of the most common types of heat exchangers used and the factors listed above that determines why each type of heat exchanger is best suited to the decision to utilize that heat exchanger to solve that process requirement.

1PLATE & FRAME HEAT EXCHANGERS

Plate & Frame heat exchangers are the most economical heat exchanger of all the types available. However, that most economical choice comes with the most restrictions of the fluid to be introduced into the heat exchanger. The entering fluid must be exceptionally clean, operating at a low pressure, and the fluid temperature ceiling is limited. Violation of any of the operating parameters can and will cause failures and ruin the heat exchanger. Plus, and of great importance is the little or no variation of the process flow rate. Plate and Frame heat exchangers produce extremely high heat transfer rates which is the main reason for their being the most economical heat exchanger type.

They do not foul unless the process flow rate changes substantially which can and will cause excessive fouling. The heat exchanger immediately ceases to perform and requires immediate dismantling and cleaning, which is expensive and is costly downtime. All these factors must be considered when selecting a Plate & Frame Heat Exchanger as the choice to solve the plants process problem.  A small problem is that there are limited choices of qualified plate & frame manufacturers in the industry.  This may have a detrimental effect on available prices and deliveries. 
  

2.SHELL & TUBE HEAT EXCHANGERS

The shell & tube heat exchanger is by far and away the most popular choice of heat exchangers utilized by processing plants. It solves most of their processing situations and is the 2nd most economical choice behind the Plate & Frame Heat Exchanger. An added benefit to the plants is the fact that there are literally dozens and dozens of bona fide shell & tube manufactures in the world that assures the heat exchanger seeker the ability to secure multiple and probably the best choice of prices and deliveries that suite their project schedule.

The conventional metal shell & tube heat exchanger is the most durable heat exchanger available and can and will withstand the most operator abuse of all the heat exchanger types available.  Most are very fragile and need tender love and care by the plant maintenance personnel, which hardly never happens. Basically, shell & tube heat exchangers are straight forward and almost always survive despite the plant field staff. For these reasons, it is the “go-to” heat exchanger for all processing plants.

3.DOUBLE PIPE & HAIRPIN HEAT EXCHANGERS

Hairpin & double pipe heat exchangers are very similar to shell & tube heat exchangers but are constructed in “U” shaped construction. The size range does not match the shell & tube heat exchangers as the largest diameter shell available in hairpin and double pipe heat exchangers is about 16”.  Their main function in the processing plants is to handle the heating and cooling of processes where a temperature “cross” occurs between the process streams. When a temperature cross does occur, shell & tube heat exchangers have problems as no longer can the heat exchanger have multiple tube side passes which penalizes a shell & tube heat exchanger performance. This is because the fluids temperature cross dictates that fluids must flow in a counter current flow direction, which once again penalizes shell & tube heat exchangers. However, hairpin and double pipe heat exchangers ALWAYS flow in a counter current pattern. The only downside of hairpin and double pipe heat exchangers is their comparatively smaller size can push them into multiple heat exchangers which adds greatly to the initial expense and increases the field foundations and piping costs. 

An added benefit is that in the double pipe version of the hairpin heat exchangers, the large size of the single tube allows the fluid to be much dirtier without plugging the heat exchanger. There are very few viable manufacturers of hairpin and double pipe heat exchangers which severely limits available bidders limiting price and delivery choices.

4. SPIRAL HEAT EXCHANGERS

Spiral heat exchangers are the “last resort” heat exchanger that is utilized when no other heat exchanger can perform the heating/cooling task mainly due to the dirty, fouling, plugging nature of the process fluids. Therefore, they are the most expensive of the types of heat exchangers. While many different processing plants occasionally utilize spiral heat exchangers in the plants, the far and away number one user of spiral heat exchangers in the Pulp and Paper industry where almost all the process streams are easily the dirtiest, most fouling prone process streams in any plant. Spiral heat exchangers simply do not foul because of their unique construction and do not plug because of that same construction method. However, that construction method is extremely labor intensive which is the main factor in the expensive selling price. However, some processes are so prone to foul and plug that a spiral heat exchanger is the only solution to the heating and/or cooling processing dilemma and must be used regardless of the cost.  

An added problem is that there are not many viable Spiral Heat Exchanger manufacturers available which severely limits choices having a detrimental effect on pricing and delivery choices.

5.SPECIALTY HIGH CORROSION RESISTANT HEAT EXCHANGERS

There are several types of specialty high corrosion resistant heat exchanger. All have their advantages over the others and have their disadvantages when compared to the others. They are Fluoropolymer Heat Exchangers, Graphite Heat Exchangers, and Glass Heat Exchangers.

Fluoropolymer heat exchangers are probably the most corrosion resistant and foul free heat exchangers but have many restrictions. Because of the poor heat transfer capabilities of fluoropolymer tubes, very small tubes must be used requiring very clean fluid be introduced into the heat exchanger. A major drawback to fluoropolymer heat exchangers is the maximum shell OD is 14” which creates the need for multiple shells in larger flow rates adding greatly to the expense in terms of both initial cost and foundation and field piping cost.

Graphite heat exchangers while probably less corrosion resistant than the Fluoropolymer heat exchangers utilize much larger tubes and the shells have no restrictions to shell sizes. Therefore, the Graphite heat exchanger can be made as large as required to meet the process demands. The (2) major drawbacks to Graphite heat exchangers are the way the tubes are connected to the tube sheet.  While the Graphite construction material may be corrosion resistant to the harsh chemicals that flow through the heat exchanger, the tube joint connecting those tubes to the tube sheet is a weak point.  Over a period, those harsh chemicals will “eat” away that joint leading to leaks and causing needed repairs leading to expensive down time. However, the major drawback to Graphite heat exchangers, both Shell & Tube and Block heat exchangers is the catastrophic failures due the thermal expansion of the graphite material. Any upset condition in the plant process stream causing a temperature spike can and will cause thermal expansion and immediate failure of all graphite heat exchangers many facilities will not allow them to be used at their facilities.  Also, there are very few domestic manufacturers of graphite heat exchangers. Almost all are made in Europe limiting choices and extending delivery times.

6.GLASS HEAT EXCHANGERS

Very few glass heat exchangers are even in existence nowadays. Their extremely fragile nature has force the plants using these heat exchangers to remove them and replace them with other more dependable synthetic heat exchangers made of materials like fluoropolymer, graphite, or exotic metals.

 

 

 

Archives

Skip Navigation Links.