One Stop Heat Exchanger Information

Do you think that all steel can be used for high temperatures? There some which we can use while some others are not suitable. Well, for your information, there are various types and species of steel that we can use in the industry and processes. I recently stumble upon a site that shares this information on the types of steel that can be used for high-temperature services.

Four different types of steel used for high-temperature service:

• Carbon steels – for most usage up to 750 degrees F (400 degrees C). Carbon steels are cheaper, very strong, with highest thermal conductivity. Above 750 degrees F, their creep increases; above 950 degrees F (510 degrees C) they get oxidized too.
• Chromium-molybdenum steels – resist oxidation up to 1200 degrees F (650 degrees C). But their thermal conductivity is lower; and chromium-molybdenum steels are more expensive than carbon steels.
• Ferritic stainless steels – can be used up to 1500 degrees F (820 degrees C).  Ferritic stainless steels have higher thermal conductivity, lower thermal expansion coefficient, and less expensive than other materials for the same service. Ferritic stainless steels can resist oxidation as well as attack from sulfur- and carbon-containing flue gases. Coefficient of thermal expansion of ferritic stainless steels is lower than for austenitic stainless steels. Loose strength after a very long usage at high temperatures.
• Austenitic stainless steels – the strongest among steels for use at high temperatures and do not loose strength after very long usage at high temperatures. Austenitic stainless steels resist oxidation at high temperatures and are widely used in boilers, super-heaters, refinery services, etc., where chlorine is not present.

These are part of the steels that can be used for the manufacturing of various heat exchanger including shell and tubes, spiral heat exchanger and plate heat exchanger.

This information is credited to http://brazedplateheatexchangers.wordpress.com/2010/07/01/which-types-of-steel-can-be-used-for-high-temperature-service/

Leak Testing of a heat exchanger tube and tube-tube sheet was successfully performed by SGS from March 16-17, 2010 in a refinery in Ulsan, Korea. SGS used this Non-Destructive Testing (NDT) method for the very first time on a heat exchanger.

SGS Korea (www.kr.sgs.com/home_kr_v2.htm?selen=1) was awarded a contract to provide Leak Testing of a heat exchanger tube and tube-tube sheet in a refinery in Ulsan, Korea on March 16, 2010. This Non-Destructive Testing (NDT) method was used for the very first time on a heat exchanger.

The SGS team of four experts successfully performed Leak Testing (link to: www.kr.sgs.com/srs/special_leak_test_srs/helium_leak_test_srs.ht ..) of a heatexchanger tube and tube-tube sheet using helium gas during the two days of testing. The gas was introduced into the internal space of the heat exchanger and over pressurized. Consequently, the gas flew through welding flaws, cracks or pin holes and was sucked into a sniper attached to a helium mass spectrometer. Following the ionization of the gas in the ion chamber by an electronic beam, the helium ion collector gathered the helium ions and sent an amplified signal to the indicator. The leakage could be measured by the signal strength.

Due to SGS’s extensive experience in Non-Destructive Testing (www.ndt.sgs.com/) the leakage in the welding area of the heat exchanger was successfully identified and reported to the client. The successful completion of the project resulted in SGS receiving further contracts for NDT services from this client.

For the very first time, SGS applied Leak Testing, which had been limited to LNG carriers until now, to a completely new field. As Leak Testing of a heat exchanger tube and tube-tube sheet proved to be successful, SGS will expand its NDT technologies to new industrial fields.

In addition to Leak Testing of heat exchangers, SGS provides Heat Exchanger Life Assessment System (HELAS) (www.sgs.com/ndt-heat-exchanger-life-assessment-system?serviceId= ..), which is based on the measurement of ultrasonic immersion length, converted into the corrosion depth inside cooling water or air fin type tubes.

About SGS Industrial Services

As the world’s leading inspection, verification, testing and certification company, SGS offers a complete package of inspection in and around heat exchangers, in order to create a full set of data which is easy accessible and ready for follow-up. Several inspection and testing technologies and tools can be applied depending on your preferences and technical requirements.

The SGS Group is the global leader and innovator in inspection, verification, testing and certification services. Founded in 1878, SGS is recognized as the global benchmark in quality and integrity. With more than 56,000 employees, SGS operates a network of over 1,000 offices and laboratories around the world.

The article is taken from the following press release:

Leak testing of heat exchanger provided by SGS.

Press Release.

If you plan to design a heat exchanger, do you know where you should start?  You’ve done it before, unfortunately you hate the feeling of getting half way through the design and realizing that you forgot to consider one other important element.  The thought process involved is just as important as the calculations involved.  Let’s map out a heat exchanger design strategy.  We’ll do so with a series of questions. We’ll let you think first and in a few days, we’ll gradually post the answers.

1.  Is there a phase change involved in my system?

2.  How many “zones” are involved in my system?

3.  What are the flowrates and operating pressures involved in my system?

4.  What are the physical properties of the streams involved?

5.  What are the allowable pressure drops and velocities in the exchanger?

6.  What is the heat duty of the system?

7.  What is the estimated area of the exchanger?

8.  What geometric configuration is right for my exchanger?

9.  Now that I have a geometry in mind, what is the actual overall heat transfer coefficient?

10.  What is the actual area of the exchanger using the ‘actual’ heat transfer coefficient?

11. What are the materials of Construction, ease of maintenance, cost of exchanger and overall heat integration

Think of the questions…

We’ll provide answers for it in latter posts.

Are you those person who loves or wants to design heat exchangers? Well, here is a download for a heat exchanger design software. You can design heat exchangers using “HTRI Exchanger Suite (5)”. Please share with us how is the software?

http://rapidshare.com/files/97482312/HTRI_5.part1.rar.html

http://rapidshare.com/files/97496005/HTRI_5.part2.rar.html

http://rapidshare.com/files/97659439/HTRI_5.part3.rar.html

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The NitroJet technology blasts through the hardest deposits without damaging the tubes. Secondary waste streams are minimized through this dry process.

Shell and tube heat exchangers can be used in a variety of industries for a various of applications. A shell and tube heat exchanger composition consists of a series of tubes. Some of the tubes or pipes contain fluid that is heated or cooled depending on a the application. Another set of tubes is used to manipulate the other, hence the first heat exchanger can provide or absorb heat. Shell and tube heat exchangers are usually conducted in high-pressure effort. In this case, heat exchanger tubing is very crucially important as it is the medium where heat is transferred.

Heat exchangers are usually composed of fluoropolymers. Fluoropolymers such as PTFE, PFA, FEP, PVDF are usually utilized in many different areas because of their versatile and tenacious character.

If you are intend to purchase a shell and tube heat exchangers, you must consider 7 critical factors before deciding to purchase one. Consider the following:

1) Heat exchanger tube diameter

The diameter of the tube can be manipulated by the provider. A key point to consider is the nature of the particular liquids used in the pipes. Smaller pipes warrant will clean faster, yet more pipes may be less effective and less compact with respect to space.

2) Thickness of the tube

The thickness of the pipe refers to several factors. Corrosion, flow resistance, axial force, pressure, and the availability of spare parts in connection with a heat exchanger tube thickness.

3) Heat exchanger shell diameter and tube length

A heat exchanger costs is directly influenced by the shell diameter and tube length. Customers who are concerned about the cost of heat exchangers questions which the longest length of pipe to provide without compromising its effectiveness. The possibility of long tubes may be limited because of the limited space, specific job specifications, capabilities and replacement.

4) Tube corrugation

The corrugation of tubes influences the performance of a shell and tube heat exchanger. Corrugated cardboard, the tube increased turbulence of fluids in turn deliver better results.

5) Tube Layout

“Tube layout ‘refers to how a heat exchanger tube is placed in the skull. To date, four major layouts to consider: triangular, twisted triangular, square and rotated square. Triangular tube facilitates a better heat transfer, while the square tubing provides a longer period of purity.

6) Tube pitch

“Tube pitch” refers to the distance between the centers of separate but interconnected tubes. A general rule determines the pitch of a pipe shall not be less than 1.25 times the outside diameter tubes.

7) Heat exchanger baffles

“Baffles” are used in shell and tube heat exchangers for liquid flow in the direct beam. Baffles prevent tubes from sagging, and can also prevent them from vibrating. Baffle spacing is important in relation to pressure drop and heat transfer. Baffles closely shared a greater pressure drop causes, but still too far apart may cause cooler spots between them.

Heat exchanger tubing is an essential part for a shell and tube heat exchanger. The types, materials and quality of the tube depend on the application and industry. Before an engineer decides to purchase heat exchanger tubing, he needs to inspect and consider several aspects and specifications.

The engineer should first either choose which type of specification he want to refer to. It can be either Welded ASTM or Seamless ASTM.

Regardless of the industries, when an engineer needs a heat exchanger tube parts, he should search for a full service manufacturer and distributor that offers highest quality heat exchanger tubing and the one that has the largest inventories. The heat exchanger tubing company should have unique blend of manufacturing and distribution capabilities and is able to meet critical lead times. The heat exchanger company should also be very capable to offer all testing and added value services to the heat exchanger tubing specifications.

Anderson Tube is an example of a stocking distributor of high quality pressure tubing certified to SA-178 Grade A and SA-214. The company specialized in boiler tubes, condenser tubes, heat exchanger tubes, ferrules, and boiler tube plugs. The entire Anderson Tube products are made in the USA. Their customers include mechanical contractors, original equipment manufacturers, fabricators, end users, exporters, tourist railroads, utility power plants and other distributors located throughout the U.S., Canada and overseas.

Photo credited to ameritube.net 4MG7TD5JDG7K

Heat exchanger is a very important equipment in processing industry. A ‘heat exchanger’ may be defined as equipment that transfers the energy from a hot fluid to a cold fluid. The process of heating or cooling occurs in the heat exchanger. In heat exchangers the temperature of each fluid changes as it passes through the exchangers.

There are various types of heat exchangers and the function depends very much on its dedicated applications. Among them are:

• Inter-coolers and heaters
• spiral heat exchanger
• shell and tube heat exchanger
• plate and frame heat exchanger
• Regenerators – refrigeration units
• Automobile radiators
• Milk chiller of a pasteurizing plant
• Condensers and boilers in steam plant
• Evaporators
• Oil coolers of heat engine

CLASSIFICATION
Heat exchangers may be classified according to the following main criteria:

1. Nature of heat exchanger process
2. Flow arrangement
3. Physical state of fluids
4. Geometry and construction

1. Classification based on Nature of heat exchanger process

(i) Direct contact:
Heat transfer will occurs by direct mixing of two fluids. This is preferred when the direct mixing is harmless or desirable.
Ex: cooling towers
(ii) Indirect contact:
Heat transfer will occurs through a separating wall between two fluids
Ex: Regenerators and Recuperators

2. Classification based on Flow arrangement

According to the relative directions of two fluid streams the heat exchangers are classified into the following three categories:

(i) Parallel flow or co-current flow heat exchangers
(ii) Counter-flow heat exchangers
(iii) Cross-flow heat exchangers

(i) In a parallel or co-current flow heat exchanger

As the name suggests, the two fluid streams (hot and cold) travel in the same direction. The two streams enter at one end and leave at the other end. The flow arrangement and variation of temperatures of the fluid streams in case of parallel flow heat exchangers, are shown in the below figure. It is evident from the figure that the temperature difference between the hot and cold fluids goes on decreasing from inlet to outlet.

In parallel flow, it is not possible to bring the outlet temperature of the cold fluid nearly to the inlet temperature of the hot fluid. This type of heat exchanger needs a large heat transfer area, so, it is rarely used in practice.
It is particularly useful when sudden cooling or sudden heating is required.
Examples: Oil coolers, oil heaters, water heaters etc.

(II) Counter-flow heat exchangers

In a counter-flow heat exchanger, the two fluids flow in opposite direction. The hot and cold fluids enter at the opposite ends. The flow arrangement and temperature distribution for such a heat exchanger are shown schematically in the below figure.

In this flow, it is possible to bring the outlet temperature of the cold fluid nearly to the inlet temperature of the hot fluid. This type of heat exchanger needs a small heat transfer area, so, it is widely used in practice.
Examples: Oil coolers, oil heaters, water heaters etc.

(iii) Cross-flow heat exchangers

In cross-flow heat exchangers, the two fluids (hot and cold) cross one another in space, usually at right angles. The flow arrangement and temperature distribution for such a heat exchanger are shown schematically in the below figure.

Source: enggyd.blogspot.com/2010/03/description-of-heat-exchange-equipment.html

The Sandia mini-reactor would be about the size of a two- or three-storey office building. At its heart is a small uranium core submerged in a tank of liquid sodium. The sodium capturies the high temperatures of the core and carries it to a heat exchanger, where liquid carbon dioxide then absorbs the heat. The CO2 expands rapidly, forcing its way through a jet-like turbine that spins an electric generator. It would be a closed-loop system, meaning the CO2 would be recycled over and over again.

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