How to Select Heat Exchangers                  Image Credit: Alstrom Energy Group | Tranter, Inc. | Advantage Engineering, Inc.   Heat exchangers are used to transfer heat energy from one fluid to another in order to control the temperature of a system or substance. Heat exchangers contain two streams of fluid, one hot and one cold, which are separated by a thermally conductive tube...
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Q & A on Heat Exchangers

We asked our users for their input on Heat Exchangers. Here are the results of 502 users familiar with Heat Exchangers.

Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice

Who Took Our Poll?Top

Design TrendsTop

Q:
What new technologies are influencing heat exchanger design?
112 answers
Answers:

I have a good impression about Compabloc welded plate heat exchanger from Alfa Laval. The larger models are laser welded. This results in a unit with less stress, improves reliability, extends the working life...and is a shorter and more flexible delivery time !

~GlobalSpec Registered User
There was some innovative developments through the mid 00's but it appears there is little new technology in the last 5 years in heat exchanger design, and operation. Internal design innovations in shell and tube exchangers in the mid 00's increased efficiencies, but these innovations are only just making it into commercial operations in Australia, however there appears much greater uptake in the rest of the world. Plate heat exchangers do not appear to have had much development in the last 25 years.
~GlobalSpec Registered User

Mostly computational analysis-design. Makes possible more complex arrangements & optimizations that would not otherwise be possible or would be too cumbersome. New welding technologies have also been helpful.

~GlobalSpec Registered User
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Q:
From your perspective, which companies are creating the most innovative heat exchangers?
94 answers
Answers:

Catalytic Products International has one of the most innovative designs on the market with the Floating Tube Heat Exchanger. On one end, the tubes are welded to a tube sheet. On the other end, they pass through the tube sheet and are allowed to expand and contract according to the temperatures each individual tube encounters. This eliminates the issues typically caused by expansion joint technology, such as bent or dropped tubes, failed tube sheets, or ruptured expansion joints. A pressurized air seal prevents any cross-contamination between the shell-side air flow and the outflow side tube sheet.

~GlobalSpec Registered User

From a design standpoint, Fluor has always been on the forefront of new and innovative heat exchangers as the industry demands exchangers to handle more aggressive and severe process services ranging from high pressure, temperature, highly corrosive, large duties and new technologies. The power industry that has started to see more business in the renewables and green energies has demanded a unique set of exchangers that must be designed for the specific processes.

From a manufacture standpoint, Alfa Laval has a different array of innovative heat exchangers when it comes down to non-conventional exchangers. Examples would be their steps in manufacturing larger welded plate exchangers, their Paqinox technology, spiral wound exchangers.

~GlobalSpec Registered User

JORD-Australia : Air Cooled Heat Exchangers Borsig- Germany : High pressure & WHR Exchangers OLMI ; High pressure Heat Exchangers KOCH : Double pipe and special twisted tube Heat exchangers HUDSON : Air Cooled Heat Exchangers. GEA : Air Cooled Heat Exchangers and a host of Finned Tube and other Exchangers. HAMMON : Air Cooled Heat Exchangers. Alfa Laval : Plate Heat Exchangers. Air Liquide : Cryogenic Heat exchangers. Balche-Durr : {ower plant Hea5 Exchangers. SPX : Vacuum Condensers Bronswerk : Special type of Heat Exchangers. Lummus : Heat Exchangers & Air Coolers, Breech Lock Heat Exchangers. Ecodyne : AIr Cooled Heat exchangers Evaporators.

~GlobalSpec Registered User
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Applications and UseTop

Q:
Please share with us any “non-standard” applications that a heat exchanger has been used for?
53 answers
Answers:

Since I deal mainly in the oil and gas industry, my "non-standard" applications are ones that deal with outside that industry, but are not really that non-standard. The solar power plant industry is starting to pick up and we are seeing molten salt used as the heating medium; exchangers have to be designed to handle this hot medium as well as the cyclic service that comes inherent to solar power plants. CO2 capture has also become an important technology, the exchangers designed for handling the heat transfer in this process are very large and unique in their design.

~GlobalSpec Registered User

We had a R-12 centrifugal chiller (now replaced with new R-134a). It was designed to cool 75 cu.m/h water from 20 to 5 deg C. We could use only about 50 to 60 cu.m/h water. We had one more requirement of cooling small quantity of argon gas from 45 to 10 deg C. We had used a small locally made exchanger as evaporator to cool argon by diverting some liquid refrigerant from main condenser and expanding before the tube side of this small evaporator successfully.

~GlobalSpec Registered User

BAHE in cryogenic process plants are "not standard". They are placed in a plant where they can be subject to severe fire and they cannot resist design temp higher than 70°C and cannot be depressurized quickly enough to prevent inside differential temperature, so the choice is unsafe in any case rupture for external fire (PSV are not able to protect this item when they are gas only) otherwise Emergency Depressurizing can not be done with the required speed. These exchangers are a weak point in plant safeguarding, and everybody is ignoring that. Exchanger Manufacturer, Plant Designers, Client Company, code & standard.

~GlobalSpec Registered User
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Q:
Do you know of any disastrous mistakes that occurred due to the incorrect usage of a heat exchanger?
42 answers
Answers:

Yes. Heating water from cold, using steam can lead to unexpected sub-atmospheric pressure that prevents condensate from exiting through a steam trap. Then steam cannot reach the tubes because they are submerged in cool condensate. If the surface of the water is large and the boiler output is small, the system can "lock up". The surface of the condensate is heated but does not circulate down. The condensate is heated to about 90C, but poor heat transfer from condensate to the tubes does not adequately heat the water passing through them. One solution is to allow the water temperature in the tubes to rise above 100C. That may not always be acceptable. Another solution is to use a condensate extraction pump. It is difficult to find small ones other than expensive piston pumps. Another solution is to use a steam trap with solenoid valves operated by a control system. An extra valve will be needed to let steam or air into the heat exchanger so the condensate can flow out. A vacuum pump or bleed valve may also be essential to remove air or allow air to escape.

~GlobalSpec Registered User

Freezing up and breaking because of not enough glycol to prevent freezing, using salt water to prevent freezing, corrosion will destroy standard heat exchangers. Be sure to figure in the cost of propylene glycol when bidding your job, or costing your new systems.

~GlobalSpec Registered User

Yes, lessons learned would be always inspect and maintain high risk exchangers and services to avoid catastrophic failures. High risk would include severe services (hydrogen, H2S), high pressure, high temperature, and aged equipment. Most exchangers have a life of 30 years, any operation past that mark must be diligently observed with frequent inspection on the mechanical components, welds and flange connections.

~GlobalSpec Registered User
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FeaturesTop

Q:
What would your design or feature "wish list" be for this product?
89 answers
Answers:

My ultimate "wish list" as a design engineer would be to have access to the design programs for all of the new and innovative products in the industry. Often the new technologies are "black box", as we request the designs from the proprietary manufacturer, we are not given access to how those designs are rated. When it comes down to comparing competitive manufacture designs, say for welded plate exchangers, we as the engineering company have to take the vendor's word for if the exchanger will perform as designed. The most innovative technologies require a leap of faith in respect to both the engineering company and ultimately the client who is purchasing the technology

~GlobalSpec Registered User

1. For air compressor inter stage and after coolers the auto condensate drain system should work perfectly. My experience is very discouraging on this aspect. 2. Tube bundle should be easy to handle with special arrangements if needed. 3. Special coating for water boxes for corrosion prevention.

~GlobalSpec Registered User

A)Product which can take care of external impurities in the cooling medium. b)Unit which can be easily serviceable. In fact this is one of the important points on which the selection lies. The shell and tube configuration scores over plate heat exchanger in spite of compactness and efficiency of PHE

~GlobalSpec Registered User
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Q:
Is there any advice you want to share with users to help them avoid common errors in selection or usage of a heat exchanger?
61 answers
Answers:

Be sure that you include provisions for adequate instrumentation...Pressure gauges, thermometers, and flow meters. Also include provisions for Clean In Place so that the heat exchanger can be cleaned early in the fouling stages. Do not specify "clip on" style gaskets unless it is an application that requires frequent changing of the gaskets. In typical non corrosive applications, glued on style are much more user friendly when opening to service the equipment.

~GlobalSpec Registered User

Look at the exchanger with the entire system in mind. If you only design the exchanger from the required duty, flow rate, allowable pressure drop, you might miss an opportunity to possibly reduce the amount of exchangers required for your overall process. Sometimes if you can have a higher allowable pressure drop, you can make the design more efficient with higher shellside/tubeside velocities which also can discourage fouling.

~GlobalSpec Registered User
If not an expert, use sizing programs available from company websites. Get quotes from various suppliers & compare...watch your specs, the cheapest supplier may cut corners in a way that hurts you later. Use consulting services to help you evaluate competing bids. An independent expert's opinion will help save you a lot of money over time.
~GlobalSpec Registered User
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Buying AdviceTop

Q:
Do you have any advice for people relative to buying or using heat exchangers?
51 answers
Answers:

Make sure the design is right before rushing into purchasing the equipment. Have a competent design engineer either design the exchanger or check the design coming back from the manufacturer before it is built to avoid unseen cost further down the road in manufacturing and operational costs. Heat exchangers are highly optimizable in how they handle duty, designed to minimize fouling and operational costs (ie water).

~GlobalSpec Registered User

First well definition of all operations conditions (minimum. normal and maximum) and abnormal conditions. Second choose the type (shell and tube, plate,..) Specify the correct materials, Check the design, Test the equipment. If using water to cool, never allow the work temperature over 40 ºC. Pay attention about control system. If the tube fails, pay attention to other equipment connected.

~GlobalSpec Registered User

Fittings can have a large impact on heat exchanger pressure drop. Flow configuration (cross, counter, cross-counter, parallel) as well as flow type (mixed or unmixed) can be important depending on the effectiveness requirements.

~GlobalSpec Registered User
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