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By pexpipeman, 10/11/2012

Heat exchangers of this type consist of a number of series-connected units. Each link consists of two coaxial tubes. For easy cleaning and replacement of the inner tubes are usually interconnected. Double-tube heat exchangers with significant heating surface consists of a number of sections, parallel-connected manifolds. If one of the coolant is saturated steam, it is usually sent to the annular (ring) space. These heat exchangers are often used as a liquid or gas-liquid. Selection of the inner and outer diameters of the tubes can be provided to both the working environment, participating in the heat transfer, the necessary speed to achieve a high heat transfer rate.

Advantages of double pipe heat exchanger: a high heat transfer coefficient, suitable for heating or cooling media at high pressure, ease of fabrication, installation and maintenance.
Disadvantages twin tube heat exchanger – bulky, high cost due to the large consumption of metal on the outer tube, are not involved in the heat exchange, the complexity of cleaning the annulus.

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By pexpipeman, 12/16/2011

Heat exchangers are the sub devices used for exchanging the heat, as its names suggests. It transfers the heat efficiently from one medium to another. Heat exchangers are generally used in all the devices which can control temperature and humidity of a proper volume space. For example, these are used in chemical and power plants, natural gas processing, in refrigeration, air conditioning or you can say in HVAC industries.

There are many types of heat exchangers depending upon the shells, tubes, wheels, plates and fluid used in them. Few of them are:

Adiabatic wheel type: This type of heat exchanger uses a transitional fluid or solid to store the heat and has the capability of absorbing the heat. Further, the heat stored in transitional state’s fluid or solid moves to the other side of heat exchanger for releasing it.
Examples: Cold fluid adiabatic wheels heat exchangers have a large wheel that consists of threads and these fine threads are rotated by heat.

Plate fin type:  This type of exchangers has the passages which are sandwiched in between. And passages consist of fins. These fins are responsible for more efficiency. The fins have several shapes like offset fin, wavy fins and straight fins.

The fins and plates need to have higher heat transfer rate, so they are made up of metal alloys such as aluminum which makes them more effective.
High heat transmission, resisting extreme pressure, huge amount of heat transfer and lighter in weight are a few advantages of plate fin type heat exchangers.

Shell and tube: This type of heat exchangers contains sequences of PEX tubes or pipe like bodies.  And these tubes are filled with fluid which acts as heat transferring medium. The other tubes used in this may have some different fluid. The second fluid surrounds the tubes which are facing the thermal conditions such as cooling or heating.

Main advantage of this type of heat exchangers is that they can resist very high pressure, around or more than 30 bars. The shape of this heat exchanger is also responsible for resisting high pressure.

Plate type: This is further divided into categories depending upon the number of plates and their gaps between each other. Plate type heat exchangers are used widely in HVAC applications. These are also called as Plate and Frame type heat exchangers. The plate’s arrangements such as number of plates and gap in between them are interrelated with the efficiency of heat absorbing and transferring.

Fluid type: This is the most widely used type of heat exchangers. These are more economical than others. Espresso machines are the most common, which use this type of heat exchangers. In fluid heat exchanger’s process, two simultaneously process are held which improves its working efficiency.

Spiral type: As the name suggests, the shape of these types of heat exchangers is spiral or helical because they look like coils and have different sheets. Whole heat exchanger is divided into channels in which few channels act as reservoir of fluid which exchanges the heat.

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By pexpipeman, 04/28/2011

The plate and frame heat exchanger has some detail sheets and  ribbed sheets that are perched in a carbon steel frame. There are dishes balanced from the top drive and attached to the bottom of the bar. A weld encloses the liquid conduits that part the liquids in the device. Covers surround the entire heat exchanger unit.

Plate and frame heat exchangers are widely used in industrialized processes, such as food processing, chemicals, nuclear deposits and industrial refrigeration processes. For example, they used to chill the hydraulic oil in sulfuric acid manufacturing metal. It is also used in copper mines and for extremely sticky substances, such as eggs, sauces, honey, or starches, in food processing.

Heat exchangers are necessary and frequently used in heat and electricity, air conditioning and refrigeration, heat recovery, transport and manufacturing industries. This equipment is also noteworthy in electronic cooling and environmental issues such as thermal pollution, waste disposal and sustainable development.

Plate heat exchangers are available in a variety of metal alloys handle highly corrosive liquids. The expansion and addition of services in one easy, because the building. Because of the heat transfer coefficients higher, the space is less than the peel and-tube unit, which reduces the cost of plant construction.

Gaskets that connect the disks are the main weakness of this heat exchanger’s frame. Depending on the speed of the fluid and corrosion, seals can begin to lose, after a period, after the downtime that require maintenance and replacement. Pressure drop in the heat exchanger is high, and this may require the purchase and operating costs and more efficient pumping system. Although the maintenance is easier for a plate heat exchanger, it can still become clogged. This leads to long periods of inactivity.

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By pexpipeman, 10/20/2010

Of shapes, sizes and design features of the PEX heat transfer plates depend on the intensity of heat transfer, reliability, staff, technology in production and labor for maintenance and repairs.

Corrugated plates are made by cold forming sheet metal, have increased stiffness compared to flat plates. On the wafer surface due to the presence of corrugation are slotted between plates winding channels of complex shape in which a relatively low flow rates is achieved by turbulence moving environments. In its position in the apparatus of the plate usually have different working fluid pressure on both sides, which can cause its deflection towards the lower pressure. To prevent such strains on each plate has vertical rows of remote (reference) projections, which create many points of mutual support between the plates. With full contact support protrusions between the plates of the assembled unit will hold a gap less than 4.5 mm.

Fluid after exiting the corner holes in between plates channel widening spreads on the input side, and then moves along the plate on a broad winding gap between them. During the washing liquid surface exposed to the turbulence which is caused by frequent rotations of the flow in the channels formed by corrugations.

Plates belonging to the same unit, also differ from each other constructively, which is due to their particular assignment and the relative position of the package. Multiples in the form of the plate at their destination in the apparatus is divided into three types: ordinary, boundary and limit.
Ordinary plate characterized by having a total number of holes in the corners, that is, each of which has four openings. Plates with these holes in the assembly apparatus form longitudinal collector channels. Ordinary plates make up the majority of plates in the apparatus. In each apparatus ordinary plate work in parallel in the same thermal and hydraulic conditions.

Boundary plates have an incomplete number of holes in the corners (at least four). Plates of this type are installed in locations where flow direction changes and, therefore, define the boundaries of packages.
End plates are placed at the ends of sections and directly adjacent to a fixed or pressure plate. End plates do not bear the heat load, as the working medium is washed on one side only.

In gasketed plate heat exchangers are used plate systems TL and VT. Brazed plate heat exchangers, as a special case of a fully collapsible, are collected based on laser-welded modules consisting of pairs of plates of TL.

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By pexpipeman, 10/07/2010

Brazed heat exchangers are mainly used in all types of heating systems provide comfort, economy of operation and safety. In addition to the transfer of heat from one medium to another, the apparatus performs additional hydraulic isolation between primary and secondary coolant circuit. The range of collapsible apparatus produced Brazetek covers all the necessary inquiries for the thermal systems from small to large capacity. Thanks to its flexible design aids can be adapted for any specific customer needs.

Using the PTO in hot water (DHW)
One of the most frequent sites of VET – the production of hot water in domestic hot water systems instead of conventional heating in capacitive systems with coil-heater. VET instantly heats the water to the desired temperature when it is passing through a heat exchanger. This implies that hot water is available immediately and at any time. Another aspect in favor of the use of plate heat exchanger for domestic hot water needs – the need to conserve space in the system of water heating: comparison with capacitive or shell and heating systems. In the case of solar panels for heating VET solves the problem of sharing water in the solar panels from the hot water tap, it is necessary to prevent corrosion, and contamination of the panels. Cleaning the same unit of pollution, due to its design, is not difficult.