Chapter 5 heat exchangers faculty of engineering and. Materials and application techniques have been developed for. At some point the heat exchanger will need to be taken out of operation for cleaning. Fouling, not only for preheat exchangers of crude distillation units, but also for other units, is one of the most serious operating problem and source for energy loss in oil refineries. A heat exchanger is a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. Heat exchanger fouling and cleaning challenges and opportunities. May, 2020 advanced lowsurface energy coating materials targeted for heat exchanger fouling in a range of crude fouling services have expanded curran internationals tube coating portfolio. It has extensive domestic and industrial applications.
Fouling of dod shipboard heat exchangers is a chronic and costly operating problem that requires significant maintenance. Scaling is the most common type of fouling and is commonly associated with inverse solubility salts such as calcium carbonate caco 3 found in water. In order to consider heat exchanger fouling, specification of the fouling factor for each particular unit is allowed. Engineering page heat exchangers typical fouling factors. Fouling is one of the most important problems of the heat transfer equipment such as. In general, they are subject to the accumulation of contaminants, termed fouling, on the waterside of heat transfer surfaces. A heat exchanger is a system used to transfer heat between two or more fluids. Fire tube or smoke tube heat exchanger arguably, the most cleanable design is a shell and tube style heat exchanger in which the exhaust travels through the tubes with no bends. Fouling phenomenon and its effect on heat exchanger.
The phenomenon usually associated with water systems, e. The dirty truth about heat exchanger fouling heatcalc. For shell and tube heat exchanger, the common method is to use fouling factors. Fouling in heat exchangers 61 detailed analysis of deposits from the heat exchanger may provide an excellent clue to fouling mechanisms. The worldwide costs, associated specifically with crude oil fouling in preheat trains were equated to around 20% of all heat exchanger fouling mullersteinhagen. In fact, fouling has been recognised for a long time, and research on heat exchanger fouling was conducted as early as 1910 and the first practical application of this research was implemented in the 1920s. A truly zero fouling heat exchanger must have zero fouling on the tubeside as well as on the shellside. These water systems may be closed or open loop systems. Heat exchanger fouling in phosphoric acid evaporators evaluation of field data, r. Heat exchanger fouling and estimation of remaining useful life. Biological fouling may be defined as the growth of living matter on heat exchanger surfaces. C4 fouling of heat exchanger surfaces springerlink. Heat exchanger fouling and cleaning conference series. The sondex spiral heat exchanger is a circular heat exchanger with two.
Figure 2 shows the fouling resistances for cooling water inside a plate heat exchanger in comparison with fouling resistances on the tubeside inside a shell and tube heat exchanger for the same velocity. May 04, 2009 coefficient of the heat exchanger is 640 wm 2 k, determine the length of the heat exchanger required to achieve the desired heating. Fouling factors in heat exchangers the fouling factors to be used in the design of heat exchangers are normally specified by the client based on their experience of running the plant or process. Examples of components that may be subject to fouling and the corresponding effects of fouling. Fouling of heat exchangers chemical engineering monographs advisory editor.
This section introduces the basic mechanisms of heat excahnger fouling, hx physical model, aakr and gpm with bayesian updating. Maintenance of fouled tubular heat exchangers can be performed by several. The heat transfer performance and efficiency decreases due to the fouling of the heat exchanger plates and tubes. Heat exchangers consist primarily of bundles of pipes, tubes or plate coils. A lot of the headache from fouling can be avoided through informed design choices. Apr 23, 2016 design and operation of heat exchangers are still to a major extent determined by the processrelated formation of deposits on the heat transfer surfaces, i. Pdf on sep 26, 2012, hassan alhaj ibrahim published fouling in heat exchangers find, read and cite all the research you need on researchgate. Heat exchangers are used in both cooling and heating processes.
However, fouling is a selffulfilling prophecy and the selection of fouling factors or excess area must be done carefully. Biyearly conferences on heat exchanger fouling have been organised by. The zero fouling heat exchanger explained in this article is derived from the wellknown selfcleaning fluidized bed heat exchange technology where the selfcleaning action is only employed in the tubes. Fouling of a specific heat exchanger is, besides from the fouling agent. Bott fouling of heat exchangers chemical engineering.
In fact, fouling has been recognised for a long time, and research on heat exchanger fo uling was conducted as early as 1910 and the. Reverse solubility salts become less solute as the temperature increases and thus deposit on the heat exchanger surface. Awad 2011 studied the fouling of heat transfer surfaces in general. In the co2 scrubbing process three plate heat exchangers are switched in parallel, two in operation a and b and one in standby c. Specifying shellandtube heat exchangers understand what heat exchanger design specialists need to know and remember, you know your process best asif raza shellandtube heat exchangers are one of the most important and commonly used process equipment items in the chemical process industries cpi. While we were working with a local engineer on a heat exchanger application, she asked why the office always specified a. He found out that fouling agents can contain inorganic materials such as airborne dust and grit, waterborne mud and silt, as well as organic materials including biological substances and elemental carbon. Heat exchanger is equipment used to transfer heat from one fluid to another. For other types of heat exchangers, excess heat transfer area is often used. The following provides background information on many different types of heat exchanger enhancements. Fouling of heat exchangers occurs in a variety of different industries. The new heat transfer coefficient for the heat exchanger is calculated by adding the additional resistance due to fouling.
Detailed chemical analysis shows that fouling deposits formed in operating heat exchangers contain mainly inorganic material bonded by heavy hydrocarbons. Pdf fouling of heat exchangers hamza shafiq academia. Heat exchanger fouling and cleaning challenges and. Jamialahmadi article pdf bayer process heat exchangers cleaning efficiency. Heat exchanger enhancement must always satisfy the primary goal of providing a cost advantage relative to the use of a conventional heat exchanger6. Fouling and reduced heat transfer in heat exchangers. It can be used to identify and provide valuable information about such mechanisms. The operating time of an uncoated heat exchanger varies between 6 to 9 months depending on the season where thereafter the increase in thepressure drop to unacceptable values together with the inability to cool the. Fouling layers with a thickness of 3 mm are indicated in dark grey, and with a thickness of 1 mm in light grey. The deposits consist primarily of organic material that is predominantly. Pdf fouling and cleaning of modified stainless steel plate heat exchangers processing milk products, m. Nonetheless, heat exchanger fouling remains today one of the major unresolved problems in thermal science, and prevention or mitigation of the fouling problem.
The design, installation, commissioning and operation of heat exchangers to minimise fouling. If uncontrolled, levels of fouling can negate any benefits produced by careful heat exchanger design. In fact, fouling has been recognised for a in fact, fouling has been recognised for a long time, and research on heat exchanger fo uling was. An apparatus was built to study heat transfer fouling on different heat exchanger pipe surfaces by visually observing the progressive fouling deposition under the. It is very detrimental to the heat exchanger performance since it leads to a loss of its thermal duty and an increase of its pressure drop. Since the thermal conductivity of such deposits is low, see table 1, their resistance to heat transfer may well exceed that of the clean fluids, resulting in significantly. Tm is the log mean temperature difference given as t t. Published online coatings and some of the results will be presented in this paper. The two papers present an introduction to the relationships between flow velocity, surface temperature, heat exchanger construction materials, water quality, entering and exiting temperatures, and.
The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. Heat exchanger foul release coatings for crude refining tubular heat transfer services. Fouling resistance an overview sciencedirect topics. In contrast to the parallel flow heat exchanger, the counter flow heat exchanger can have the hottest coldfluid temperature greater than the coldest hotfluid temperatue. Since the fluid flows continuously in one single channel the force of the fluid acts against. Fouling factors in heat exchangers resources hrs heat. Other factors that should be addressed include fouling potential, reliability and safety. A 2shell passes and 4tube passes heat exchanger is used to heat glycerin from 20c to 50c by hot water, which enters the thinwalled 2cmdiameter tubes at 80c and leaves at 40c.
Counter flow heat exchangers are the most efficient of the three types. Pdf fouling phenomenon and its effect on heat exchanger. Fired heaters the selection of a heat exchanger depends on many factors including capital and operating costs, fouling, corrosion tendency, pressure drop, temperature ranges, and safety issues tolerance to leakage. Costs due to overdesign, additional fuel consumption and maintenance, loss of production, etc. While some improvements in fouling and cleaning were observed for some of the coatings, there is. The consequences of fouling accumulation include not only the. Apr 18, 2016 shell and tube heat exchanger fouling factors engineers are often faced with interoffice scheduling traditions. Heat exchanger surfaces reduces thermal efficiency, decreases heat flux, increases temperature on the hot side, decreases temperature on the cold side, induces underdeposit corrosion, increases use of cooling water. R sekulib university of kentucky introduction a heat exchanger is a device that is used for transfer of thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a. Optimizing the acid dissolution of sodalite scale, sebastien fortin and raymond breault article. Fouling detection in heat exchangers is still challenging.
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