Heat Exchangers

Introduction to air-cooled heat exchangers

Water shortage and increasing costs, together with more recent concerns about water pollution and cooling tower plumes, have greatly reduced industry's use of water cooled heat exchangers. Consequently, when further heat integration within the plant is not possible, it is now usual to reject heat directly to the atmosphere, and a large proportion of the process cooling in refineries and chemical plants takes place in Air Cooled Heat Exchangers (AC-HEs).

There is also increasing use of Air Cooled Condensers for power stations. The basic principles are the same but these are specialized items and are normally configured as an A-frame or "roof type". These condensers may be very large-the condensers for a 4000 MW power station in South Africa have over 2300 tube bundles, 288 fans each 9.1 m in diameter and a total plot area 500 m X 70 m.

AC-HEs for process plants are normally just called Aircoolers, but should not be confused with devices for cooling air (best described as Air Chillers).

The design of an AC-HE is more complex than for a Shell and Tube Heat Exchanger, as there are many more components and variables.

The structure of an AC-HE is painted or galvanized, depending on customer specification. However, the costs are roughly the same if a multiple coat paint system is specified. Often the painted units are more expensive. There seems to be a trend toward more galvanized structures because they require virtually no maintenance. Painted structures require touch-up after installation and they often rust anyway.

Air-cooled heat exchangers are used extensively throughout the oil and gas industry, from upstream production to refineries and petrochemical plants, under high pressure and high temperature conditions, as well as corrosive fluids and environments.

Fundamental Working and Purpose of Heat Exchanger

The heat exchanger is a system that helps transfer the heat into two or more fluids. Heat exchangers have their applications in both the heating and cooling processes. The fluids in the heat exchangers are kept separate with a solid wall in between them. One fluid's heat passes across the metal used to keep both of the fluids separate, and the heated metal then increases the other fluid's temperature. High turbulence, high fluid velocity, significant temperature differential, and high surface area; all these factors immensely contribute to efficient heat transfer. However, different designs can get tested for even better heat transfer, which prompted us to build Box Type Heat transfer that offers an improved heat transfer compared to the shell and tube type heat exchanger.

The heat exchange plate of the fully welded plate heat exchanger is made of special stainless steel and pressed with a special mold. The surface is smooth and not easy to scale. Its unique corrugated design enables the fluid to generate turbulent flow even at low flow rates, and has high heat transfer efficiency. No non-metallic sealing material is used, so it has high temperature and pressure resistance. It can be used for extreme working conditions with a working temperature of 300°C and a pressure of 3.0Mpa. The advantage is that it has a corrugated plate structure similar to the plate heat exchanger. At the same time, it adopts a more advanced all-welding process to seal, no gasket design, and a variety of metal and alloy materials to choose from, ensuring the applicable temperature of the all-welded plate heat exchanger. Almost all heat exchange process occasions from -195℃ to 538℃ and working pressure from vacuum to 8.2MPa. And it has the characteristics of compact structure, efficient heat transfer and flexible use.

Leveraging on rich expertise and advanced manufacturing facility, we are counted as one of the reckoned manufacturers and exporters of Paddy Dryer Heat Exchanger. Quality is our prime focus, hence we source tested quality materials from authentic vendors to manufacture these heat exchangers as per industrial standards. Finds application in chemical, oil and refinery plants, our Paddy Dryer Heat Exchanger is demanded among our clients for its impeccable performance, easy installation and rust proof finish.

 Features of Paddy Dryer Heat Exchanger :

• Uniform and reliable heat transfer
• Rust proof body
• Hassle free installation

• We manufacture Shell & Tube type Heat Exchangers in a wide variety of sizes & materials. We have a complete facility to design (Thermal and Mechanical) and manufactures complete range of Shell and Tube Heat Exchangers for cooling, condensing and heating application.
• A Shell & Tube Heat Exchanger Consists of a Shell with Traditional plain tubes or enhanced surface tubes for high thermal performance.
• Our manufacturing facility is well supported by in house design facility equipped with latest software’s & design codes and welding development department to establish manufacturing process for any new material.

U Tube bundle Heat Exchanger can build "U" tube bundles, straight tube "floating" tube bundles, or we can retube fixed tubesheet heat exchangers when the bundles is not removable and multitherm is not locked into any one material. Heat-exchanger system consisting of a bundle of U tubes hairpin tubes surrounded by a shell outer vessel, one fluid flows through the tubes, and the other fluid flows through the shell, around tubes.Multitherm can duplicate any existing bundle to include dimensions, materials and performance.Some bundles tend to be build with copper tubes and steel tubesheets. U Tube bundle Heat Exchanger of each tube are connected to plenums (sometimes called water boxes) through holes in tubesheets. The tubes may be straight or bent in the shape of a U, called U-tubes.

Specifications :

• U Tube bundle Heat Exchanger which typically have U-tubes.
• U Tube bundle Heat Exchanger can be used to boil water recycled from a surface condenser into steam to drive a turbine to produce power.
• Most U Tube bundle Heat Exchanger are either 1, 2, or 4 pass designs on the tube side.
• This refers to the number of times the fluid in the tubes passes through the fluid in the shell.

Applications :

• U Tube bundle Heat Exchanger fluid goes in one end of each tube and out the other.Surface condensers in power plants are often 1-pass straight-tube heat exchangers see Surface condenser for diagram.
• U Tube bundle Heat Exchanger are two and four pass designs are common because the fluid can enter and exit on the same side. U Tube bundle Heat Exchanger construction much simpler.
• U Tube bundle Heat Exchanger are often baffles directing flow through the shell side so the fluid does not take a short cut through the shell side leaving ineffective low flow volumes.
• U Tube bundle Heat Exchanger are generally attached to the tube bundle rather than the shell in order that the bundle is still removable for maintenance. Counter current heat exchangers are most efficient and they allow the highest log mean temperature difference between the hot and cold streams.
• U Tube bundle Heat Exchanger companies however do not use single pass heat exchangers and they can break easily in addition to being more expensive to build.
• Often multiple heat exchangers can be used to simulate the counter current flow of a single large exchanger.

Advantages :

• The simple design of a shell & tube heat exchanger makes it ideal cooling solution for a wide variety of applications.
• One of the most common applications is the cooling of Hydraulic Fluid and oil in engines, transmissions and hydraulic power packs.
• With right choice of materials they can also be used to cool or heat other mediums,
• Particularly with models where a floating tube bundle (where the tube plates are not welded to the outer shell) is available. Can also be used on fixed tube sheet heat exchangers.

After cooler:
Water or moisture is not desirable in the transmission lines of an air compression system. Water carried through the lines washes away lubricating oil from the tools the compressed air is running. This causes the tools to operate sluggishly & increases the need for maintenance. The effect is compounded in high speed tools, where wearing surfaces are limited in size & excessive wear reduces efficiency by creating air leakage.

Further problem results from the decrease of temperature caused by sudden expansion of air at the end. This low temperature creates condensation, which freezes around port and valves & impairs efficiency. These conditions can be minimized by removing the moisture from the air directly after compression, before the air enters the distribution system.

The compressed air discharged from compressor is hot. Compressed air at these temperatures contains large quantities of water in vapor form. As the compressed air cools this water vapor condenses into a liquid form. As an example if an after cooler is not used, a 200 scfm compressor operating at 100 psig introduces 45 gallons of water into the compressed air system each day.

Functions of compressed air after coolers

• Cool air discharged from air compressors via the heat exchanger

• Reduce risk of fire (Hot compressed air pipes can be a source of ignition)

• Reduce compressed air moisture level

• Increase system capacity

• Protect downstream equipment from excessive heat

Inter cooler:
Most industrial compressors operating today are a multistage design. To optimize the cost of compressing gases it is popular to use multi-stage industrial compressor. When the Air compressor compresses air, heat is generated this causes the air to expand requiring an increase of horsepower for further air compression. If we remove the heat generated by compressing air, the total horsepower required for addition air compression is reduced up to 15%. For a multi stage compressor is to cool the gas between compression stages. Thus the role of the compressor intercooler is to provide colder, dryer, denser air to the next stage of compression. In addition to inter stage coolers, the compressor's final discharge is usually routed through an after cooler, which also provides colder and dryer gas to the end use point.

We provide Intercooler to suit compressor mounting by maintaining critical nozzle distance, as well as side mountings with volume bottles to avoid pulsation.

EFFICIENCY
Moisture Separator are largely used for the separation of coarse mist (or spray) from gases and vapors. A limit drop size (Dp) is used to characterize them and it is defined as the smallest particle which can be removed to an extent of 99%.

PRESSURE DROP
Due to the large percentage of the cross section available for gas flow, the pressure drop in a vast majority of applications is less than 250-500 mm WC. As mentioned above, for high efficiency applications, a larger pressure drop is to be expected.
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CHARGE AIR COOLERS are suitable for a variety of applications including Marine engine and Generator cooling. The Charge Air Coolers can be adapted for use on marine and land based equipment in a variety of sizes.

With engine efficiency constantly improving, the demand for more efficient oil cooling has never been greater. Bowman is a leading UK manufacturer of efficient, durable oil coolers for both industrial and marine engines and transmissions. Designed specifically for lubrication oil cooling, these high-quality units can be used with engines rated up to 8900 kW and are suitable for use with a range of cooling media, including sea water, fresh water or engine coolant.

Vessels & Tanks :- We Design, Engineering and manufacture customized Vessels and Tank with various material of construction line MS, SS 304, SS 316L, FRP coated or MS Rubber Lined, PTFE lined and many more. We are working with nos. of OEM for their routine requirement of vessels and tanks in their projects.

Reactors:- Reactor Vessel is the heart of process of any industry. We offer customized design (process and mechanical) and do fabrication in our own workshop as per Good Engineering Practice as well as for ASME codes also.

We deal in all types of reactor vessel like jacket, non jacketed , agitated and limped. We also deal in pillow plate jacket reactor vessel also which provided high heat transfer with low operating cost and capital cost too.