What are heat exchangers used for

what are heat exchangers used for

Heat exchanger

A heat exchanger is a system used to transfer heat between two or more lovemeen.com exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural. Heat Exchangers Help Find Chocolate’s Sweet Spot. Tempering, or the controlled heating and cooling, of chocolate is an essential step in the manufacturing of chocolate and has traditionally been carried out in batches and much of the industry is still very traditional, sometimes using technology that has changed little in hundreds of years.

For over years Meggitt has designed and manufactured heat exchangers and mobile combustion heating units for aerospace, defence, transportation and energy applications. We pioneered the development of vacuum brazing techniques for heat exchangers and our engineering experts are researching the next generation of aerospace thermal management solutions.

In-house design and manufacturing customised for each application. Enquire Now. We are one of the largest designer and manufacturers of what are heat exchangers used for exchangers for the aerospace engine market, alongside our significant presence within the general aviation market.

Our solutions manage and change temperature, control and regulate the flow of system fluids to deliver the system performance required. Our heat exchangers combine the design, development capabilities and product portfolios of facilities formerly known as Stewart Warner South Wind Corporation and Serck Aviation. From 1, pounds of thrust on a small turboprop engine to over 80, pounds of thrust for a large commercial turbofan, we can provide how does a float carburetor work custom-engineered solution.

Mechanical-bonded interfaces allow complete freedom of movement during thermal expansion — unlike brazed units where stress fractures can occur. Its innovative design means that single tubes can be easily replaced during overhaul periods, minimising costs to operators.

The operational lifetime of a tubular unit is 3 million flying hours and 50 million Serck Aviation bonded interfaces in the field have never failed.

Our brazing process produces joints of extremely high integrity, ensuring operational life is not reduced by corrosion. Due to the removal of redundant channels required in some vacuum-brazed units, the overall unit size can be reduced too. Our brazed air-to-air coolers are uniquely designed to optimise the design and ensure a high operational life. We design and manufacture complete oil cooling systems, combining our plate and fin heat exchangers with a Meggitt manufactured fan.

We are the leading supplier of engine and transmission oil coolers to the helicopter industry. Some units are designed as multiple circuits with an excellent strength-to-weight-ratio and high vibration-resistance.

We supply thermal management systems for military vehicles. Our systems — overin service — can last as long as a properly maintained airframe. If the unit needs to be returned for maintenance, repair and overhaul we have FAA-approved repair stations and strategic partnerships with world-wide distributors. In the s in the USA, Stewart Warner was producing radiators and gasoline-fired heaters for the automotive industry.

Bywe had supplied 65, radiators andair coolers for aircraft in the UK. By the 21st century, our heat exchangers have evolved to become the multiple flow, multiple circuit heat management how to install internet browser on blackberry needed by the most advanced aero engines.

These compact and lightweight units now perform multiple functions including:. At Meggitt, we can provide you with a heat exchanger that is specifically designed for your application. To discuss what you need in more detail, please contact us. Contact Us In-house design and manufacturing customised for each application. Explore our full product range below:. Tubular heat exchangers. Best performance and lowest cost of ownership for bespoke applications. Aluminium, Stainless Steel and Inconel.

Plate and fin heat exchangers. Compact designs, long life The operational lifetime of a plate and fin unit is over 1million hours. Aluminium, Stainless steel. Air to air coolers. Tubular or plate and fin coolers.

Oil cooling systems for helicopters. Oil cooling systems and combustion heaters for military vehicles. What pharmaceutical company makes verapamil Lightweight Reliable We supply thermal management systems for military vehicles.

Repair and overhaul of Meggitt heat exchangers. History and evolution of Meggitt heat exchangers. Our roots date back to the dawn of aviation. InMeggitt acquired the Dunlop Group including the heat exchanger technology from Serck Aviation and Stewart Warner South Wind By the 21st century, our heat exchangers how to whitewash antique finish evolved to become the multiple flow, multiple circuit heat management systems needed by the most advanced aero engines.

Related Products. Product Ducting. Product Thermal Systems. Product Flow Control Valves.

Heat Exchangers

Tubular heat exchangers. Tubular heat exchangers (THE) are in some cases used for pasteurization and UHT treatment of dairy products. The tubular heat exchanger (Figure ), unlike plate heat exchangers, has no contact points in the product channel and . Mar 26,  · Heat exchangers used to minimize heat losses from buildings, engines, and machines are sometimes called recuperators or regenerators. These are two quite different things. A recuperator is typically used to capture heat that would otherwise be lost, for example, as stuffy air is ventilated from a building: cold, incoming fluid is channeled in. However, because regenerative heat exchangers tend to be used for specialist applications recuperative heat exchangers are more common. Recuperative heat exchangers. There are many types of recuperative exchangers, which can broadly be grouped into indirect contact, direct contact and specials. Indirect contact heat exchangers keep the fluids.

A heat exchanger is a device used to transfer heat between two or more fluids. The fluids can be single or two phase and, depending on the exchanger type, may be separated or in direct contact. Devices involving energy sources such as nuclear fuel pins or fired heaters are not normally regarded as heat exchangers although many of the principles involved in their design are the same. In order to discuss heat exchangers it is necessary to provide some form of categorization.

There are two approaches that are normally taken. The first considers the flow configuration within the heat exchanger, while the second is based on the classification of equipment type primarily by construction.

Both are considered here. Figure 1 illustrates an idealized counterflow exchanger in which the two fluids flow parallel to each other but in opposite directions. This type of flow arrangement allows the largest change in temperature of both fluids and is therefore most efficient where efficiency is the amount of actual heat transferred compared with the theoretical maximum amount of heat that can be transferred. In cocurrent flow heat exchangers, the streams flow parallel to each other and in the same direction as shown in Figure 2 , This is less efficient than countercurrent flow but does provide more uniform wall temperatures.

Crossflow heat exchangers are intermediate in efficiency between countercurrent flow and parallel flow exchangers. In these units, the streams flow at right angles to each other as shown in Figure 3. In industrial heat exchangers, hybrids of the above flow types are often found. See for example Figure 4. In this section heat exchangers are classified mainly by their construction, Garland , see Figure 5.

The first level of classification is to divide heat exchanger types into recuperative or regenerative. A Recuperative Heat Exchanger has separate flow paths for each fluid and fluids flow simultaneously through the exchanger exchanging heat across the wall separating the flow paths.

A Regenerative Heat Exchanger has a single flow path, which the hot and cold fluids alternately pass through. In a regenerative heat exchanger, the flow path normally consists of a matrix, which is heated when the hot fluid passes through it this is known as the "hot blow". This heat is then released to the cold fluid when this flows through the matrix the "cold blow". A good overview of regenerators is provided by Walker The two main types of regenerator are Static and Dynamic.

Both types of regenerator are transient in operation and unless great care is taken in their design there is normally cross contamination of the hot and cold streams.

However, the use of regenerators is likely to increase in the future as attempts are made to improve energy efficiency and recover more low grade heat. However, because regenerative heat exchangers tend to be used for specialist applications recuperative heat exchangers are more common. There are many types of recuperative exchangers, which can broadly be grouped into indirect contact, direct contact and specials. Indirect contact heat exchangers keep the fluids exchanging heat separate by the use of tubes or plates etc..

Direct contact exchangers do not separate the fluids exchanging heat and in fact rely on the fluids being in close contact. This section briefly describes some of the more common types of heat exchanger and is arranged according to the classification given in Figure 5. In this type, the steams are separated by a wall, usually metal. Examples of these are tubular exchangers, see Figure 6 , and plate exchangers, see Figure 7. Tubular heat exchangers are very popular due to the flexibility the designer has to allow for a wide range of pressures and temperatures.

Tubular heat exchangers can be subdivided into a number of categories, of which the shell and tube exchanger is the most common. A Shell and Tube Exchanger consists of a number of tubes mounted inside a cylindrical shell. Figure 8 illustrates a typical unit that may be found in a petrochemical plant. Two fluids can exchange heat, one fluid flows over the outside of the tubes while the second fluid flows through the tubes.

The shell and tube exchanger consists of four major parts:. Rear end—this is where the tubeside fluid leaves the exchanger or where it is returned to the front header in exchangers with multiple tubeside passes. Tube bundle—this comprises of the tubes, tube sheets, baffles and tie rods etc. The popularity of shell and tube exchangers has resulted in a standard being developed for their designation and use. In general shell and tube exchangers are made of metal but for specialist applications e.

It is also normal for the tubes to be straight but in some cryogenic applications helical or Hampson coils are used. A simple form of the shell and tube exchanger is the Double Pipe Exchanger.

This exchanger consists of a one or more tubes contained within a larger pipe. In its most complex form there is little difference between a multi tube double pipe and a shell and tube exchanger. However, double pipe exchangers tend to be modular in construction and so several units can be bolted together to achieve the required duty. The book by E. Saunders [Saunders ] provides a good overview of tubular exchangers.

Furnaces —the process fluid passes through the furnace in straight or helically wound tubes and the heating is either by burners or electric heaters. Tubes in plate—these are mainly found in heat recovery and air conditioning applications. The tubes are normally mounted in some form of duct and the plates act as supports and provide extra surface area in the form of fins. Electrically heated—in this case the fluid normally flows over the outside of electrically heated tubes, see Joule Heating.

Air Cooled Heat Exchangers consist of bundle of tubes, a fan system and supporting structure. The tubes can have various type of fins in order to provide additional surface area on the air side. Air is either sucked up through the tubes by a fan mounted above the bundle induced draught or blown through the tubes by a fan mounted under the bundle forced draught. They tend to be used in locations where there are problems in obtaining an adequate supply of cooling water.

A heat pipe consists of a pipe, a wick material and a working fluid. The working fluid absorbs heat, evaporates and passes to the other end of the heat pipe were it condenses and releases heat. The fluid then returns by capillary action to the hot end of the heat pipe to re-evaporate. Agitated vessels are mainly used to heat viscous fluids. They consist of a vessel with tubes on the inside and an agitator such as a propeller or a helical ribbon impeller.

The tubes carry the hot fluid and the agitator is introduced to ensure uniform heating of the cold fluid. Carbon block exchangers are normally used when corrosive fluids need to be heated or cooled. They consist of solid blocks of carbon which have holes drilled in them for the fluids to pass through. The blocks are then bolted together with headers to form the heat exchanger.

Plate heat exchangers separate the fluids exchanging heat by the means of plates. These normally have enhanced surfaces such as fins or embossing and are either bolted together, brazed or welded. Plate heat exchangers are mainly found in the cryogenic and food processing industries. However, because of their high surface area to volume ratio, low inventory of fluids and their ability to handle more than two steams, they are also starting to be used in the chemical industry.

Plate and Frame Heat Exchangers consist of two rectangular end members which hold together a number of embossed rectangular plates with holes on the corner for the fluids to pass through. Each of the plates is separated by a gasket which seals the plates and arranges the flow of fluids between the plates, see Figure 9. This type of exchanger is widely used in the food industry because it can easily be taken apart to clean. If leakage to the environment is a concern it is possible to weld two plate together to ensure that the fluid flowing between the welded plates can not leak.

However, as there are still some gaskets present it is still possible for leakage to occur. Brazed plate heat exchangers avoid the possibility of leakage by brazing all the plates together and then welding on the inlet and outlet ports. Plate Fin Exchangers consist of fins or spacers sandwiched between parallel plates. The fins can be arranged so as to allow any combination of crossflow or parallel flow between adjacent plates. It is also possible to pass up to 12 fluid streams through a single exchanger by careful arrangement of headers.

They are normally made of aluminum or stainless steel and brazed together. Their main use is in gas liquefaction due to their ability to operate with close temperature approaches. Lamella heat exchangers are similar in some respects to a shell and tube.

Rectangular tubes with rounded corners are stacked close together to form a bundle, which is placed inside a shell.

One fluid passes through the tubes while the fluid flows in parallel through the gaps between the tubes.

They tend to be used in the pulp and paper industry where larger flow passages are required. Spiral plate exchangers are formed by winding two flat parallel plates together to form a coil. The ends are then sealed with gaskets or are welded.

They are mainly used with viscous, heavily fouling fluids or fluids containing particles or fibres. This category of heat exchanger does not use a heat transfer surface, because of this, it is often cheaper than indirect heat exchangers. However, to use a direct contact heat exchanger with two fluids they must be immiscible or if a single fluid is to be used it must undergo a phase change. See Direct Contact Heat Transfer. The most easily recognizable form of direct contact heat exchanger is the natural draught Cooling Tower found at many power stations.

These units comprise of a large approximately cylindrical shell usually over m in height and packing at the bottom to increase surface area. The water to be cooled is sprayed onto the packing from above while air flows in through the bottom of the packing and up through the tower by natural buoyancy. The main problem with this and other types of direct contact cooling tower is the continuous need to make up the cooling water supply due to evaporation.

Direct contact condensers are sometimes used instead of tubular condensers because of their low capital and maintenance costs. There are many variations of direct contact condenser. In its simplest form a coolant is sprayed from the top of a vessel over vapor entering at the side of the vessel.

The condensate and coolant are then collected at the bottom. The high surface area achieved by the spray ensures they are quite efficient heat exchangers.

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