Yeah, we're runnin' a little bit hot tonight.
I can barely see the road from all the heat comin' off of it.

("Panama," by Van Halen, 1984)

 

BEEN THERE.   DONE THAT.   SUPER BUMMER!

Oh no. There it is. The smell of steam with a touch of toasted glycol.

A glance at the temperature gauge on the dashboard confirms the situation; the pointer is well within the red zone.

The cooling system in the car is on the fritz.

It's geyser time again!

Thar she blows!

Where were you the last time that your car overheated?  In the middle of a highway stuck in rush hour traffic? Or were you a Nowhere Man/Nowhere Woman stranded alone in the boonies on a blazing hot summer day?

 

CAR RADIATORS AND FIN FANS
HAVE THE SAME PURPOSE

The radiator in your car's cooling system has the same purpose as process industry equipment known as Fin-Fan Heat Exchangers.

Radiators and Fin Fans get rid of heat pronto.

Fin Fans HExes are also known as "air-cooled exchangers."

Fin Fan HExes that make certain that the process stream being cooled down is all in the liquid phase are called "Fin Fan Condensers" or "Air Cooled Condensers."  

The PTOA will use the term "Fin Fans" for both Fin Fan HExes and Fin Fan Condensers.

PTOA Readers and Students already know that shell and tube HExes conserve energy (and therefore save $$$) by exchanging heat between a process stream that needs to be cooled down and a process stream that needs to be heated up.

Car radiators and Fin Fans are not installed to conserve heat and save money.

The car radiator and the process industry Fin Fan intentionally waste heat!

That's right!

The purpose of the radiator in your car's cooling system and the Fin Fan in a processing plant is to get rid of process stream heat and make sure the process stream is in the liquid phase before the process stream flows into the next piece of processing equipment.

 

THE ROLE OF THE RADIATOR
IN AN AUTOMOBILE COOLING SYSTEM

The process fluid used as circulating coolant in your car's cooling system is a mixture of water and a petrochemical called glycol.

This coolant is the "cold fluid" that picks up the heat generated within the engine block and cylinder head.

If heat is not removed from the engine block and cylinder head, the engine will eventually fuse into a useless lump of metal. Therefore, the priority is put on getting rid of heat instead of conserving it.

The below graphic features the engine and cooling system found under the hood of a car.

PTOA Readers and Students should notice:

• Red hot coolant enters the radiator via an Upper Hose.
• The red hot coolant is cooled into a cool blue stream as it flows from the right side to the left side of the radiator (from the Reader's point of view).
• See those fan blades in the cut-away portion of the radiator? The fan draws ambient air through the radiator. The colder air indirectly picks up the heat from the red hot coolant as the coolant flows through the radiator. The hot air (invisible in the graphic as in real life) is released into the surroundings.
• The coolant gets cooler and cooler (until it turns blue in the graphic) and exits the radiator via the Lower Hose.
• The cold blue coolant enters the Water Pump and is pumped back into the engine block and cylinder head where it once again picks up the engine's heat.

Some radiators have the warm coolant entering at the top and exiting colder at the bottom.

Whatever their structure, all radiators separate the warm coolant that flows into the radiator tubes and then aggregate the cold coolant into one process stream at the exit of the radiator.

The many fins on the radiator tubes increase the heat transfer surface area which enhances the heat transfer between the entering hot liquid coolant and the colder air.

PTOA Readers and Students will soon learn why surface area is a big deal with regard to heat transfer so don't stress about that now. Basically, the fins force the air to flow around nooks and crannies which maximized indirect heat transfer between hot and cold streams.

 

STRUCTURE AND FUNCTION OF FIN FANS

Fin Fans have many similar features to car radiators.

This puny Fin Fan shows the structure of a Fin Fan. The process Inlet is the red pipe. The casing frame for the Finned Tubes is the rectangular box. The Fans below force air through the layers of (unseen) Finned Tubes.

The flat vertical surface of a car radiator is replaced by multiple rows of horizontal tubes housed in the flat, box-like Fin Fan frame.

The process stream flows into the Header Inlet where it is divided in a Tube Sheet into multiple layers of Finned Tubes.

The fins on the tubes increase heat transfer by increasing the surface area of indirect contact between the hot process stream flowing though the Finned Tubes and the cold air that flows around the outside of the tubes.

The multiple process stream tube flows are recombined at Header Outlet and a single process stream exits the Fin Fan much cooler.

The boxes that in case the Finned Tubes are normally physically located high above ground level; Process Operators become accustomed to the sound of whirring fans above their heads.

Perched up high, the fans draw air in and force the air to flow in between the layers of tubes.

The air exits above the top layer of tubes and is much hotter.

The heat that is extracted from the process stream is wasted and blown into the atmosphere above the Fin Fan.

Even on coldest day of the year, any Process Operator willing to climb the ladder to the bank of Fin Fan boxes can warm his/her hands by extending them over the manifold in the area above the tubes.

 

THE ROLE OF THE FIN FAN HEx 
IN PROCESS INDUSTRIES

The photo below shows many green-covered Fin Fans being used in an industrial process. The green cover  protects the exchangers from blowing sand or other environmental concerns.

Note that the fans of these Fin Fan Condensers are situated on top of the Finned Tubes and therefore draw air in to make it flow in between the Finned Tubes.

A fan placed on the bottom of boxes of Finned Tubes forces air ...meaning pushes air...to flow in between the rows of Finned Tubes.

Forced air flow is the more common Fin Fan Condenser architecture but the Induced Fan model takes a much better picture!

Just like the radiator, the role of the Fin-Fan is to get rid of heat before the process stream flows into the next piece of processing equipment.

For example, a Fin-fan is typically the last piece of processing equipment that a process stream flows through before going to tankage in a tank farm.

The process stream must be in the liquid phase prior to flowing into tankage because hot vapors would collect above the surface level and put too much pressure on the tank roof.

The priority of meeting safe tankage temperature requirements trumps any interest in conserving energy.

 

Take Home Messages:  The familiar car radiator in a car's cooling system and a process industry Fin Fan have the same job of getting rid of process stream heat before the process stream flows into the next piece of equipment.

One reason process industry streams must be cooled down is to meet safe storage requirements.

Process streams must meet tank temperature requirements and the process stream must all be in the liquid phase before it flows into a tank.

Fin fans are temperature-lowering process equipment. Removing the Heat of Condensation that evolves when a gas turns into a liquid makes the flowing liquid process stream much cooler.

The priority of both the car radiator and process industry Fin Fan is to cool and condense the process stream, not conserve energy.  The heat that is removed from the process is injected into the atmosphere.

The fins on the radiator and the Fin Fan HEx tubes increase the surface area which enhances heat transfer.

Hardware nomenclature associated with Fin Fan HExes and Condensers include:

• Header Inlet/Manifold
• Tubesheet
• Finned Tubes
• Outlet Header/Manifold
• Fans

©2015 PTOA Segment 00038
Process Industry Temperature Changing Equipment.

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