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. Expresstm, novel heat exchanger analysis software for heat exchanger fouling in the pre heat train of a crude oil distillation unit. The evaluation results on platetype heat exchangers show that the overall performance in each heat exchanger are elucidated and are quantitatively compared. Costs due to overdesign, additional fuel consumption and maintenance, loss of production, etc. A heatexchanger system consisting of a bundle of u tubes. Engineering page heat exchangers typical fouling factors. The tubes carry a fluid through them, while the shell is also provided with an inlet and outlet for flow of another fluid. Over 90% of all heat exchangers suffer from fouling. The former may include bacteria, fungi or algae, while the latter includes mussels and barnacles. I am developing heat exchanger monitoring spreadsheet. Heat exchanger fouling and cleaning conference series. Fouling resistance an overview sciencedirect topics. As a consequence, the challenge is to optimise heat and mass trans. 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.
If it is too high, revise the heat exchanger configuration until the pressure drop is acceptable. This section introduces the basic mechanisms of heat excahnger fouling, hx physical model, aakr and gpm with bayesian updating. While we were working with a local engineer on a heat exchanger application, she asked why the office always specified a. Heat exchanger fouling and estimation of remaining useful life tutpol ardsomang1, j. Proceedings of 7th international conference on heat exchanger fouling and cleaning challenges and opportunities, editors hans mullersteinhagen, m. For typical residential heat pump and air conditioning residential buildings. The effects of fouling on heat exchanger performance is discussed in a later section. A bundle of tubes contained in a shell or container. When operating the heat exchanger based on the higher fouling resistance it was found that the demineralised water temperature was reduced to 26. The design, installation, commissioning and operation of heat exchangers to minimise fouling. Calculate the required heat transfer rate, q, in btuhr from specified information about fluid flow rates and temperatures. Fouling factor monitoring industrial professionals. The fouling materials can consist of either living organisms or a nonliving substance inorganic or organic. An step further is the analysis of alternative cleaning schedules and their influence in the total annual cost applying techniques existing in the literature odonnell et al 2001.
Make a more detailed estimate of the overall heat transfer coefficient, u, based on the preliminary heat exchanger configuration. During operation with liquids and gases a dirt film may build up on the heat exchanger surfaces. Pdf fouling phenomenon and its effect on heat exchanger. Fouling phenomenon and its effect on heat exchanger. This unique and comprehensive text considers all aspects of heat exchanger fouling from the basic science of how surfaces become fouled to very practical ways of mitigating the problem and from mathematical modelling of different fouling mechanisms to practical methods of heat exchanger cleaning. If other systems are used then different field fouling allowances may be required. Dec 07, 2016 the fouling factor represents the theoretical resistance to heat flow due to a build up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger but they are often. 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. Hi,i usually advise people to use the following equation to monitor fouling factor. Antifouling he new technology can reduce heat exchanger. The semiempirical formula to predict asymptotic value of fouling thermal resistance velocity dependence based on heat and momentum transfer analogy is. Use of cfactor for monitoring of fouling in a shell and tube heat exchanger.
Heat exchanger fouling and cleaning challenges and. Fouling of heat exchangers me485 heat exchanger and steam generator design fouling accumulation of undesirable deposit on a hex surface. Heat exchanger fouling calculation posted in process heat transfer. Heat exchanger fouling and estimation of remaining useful life. 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. Make an initial estimate of the overall heat transfer coefficient, u, based on the fluids involved. Due to different designs, composition, and transfer fluid, each type of heat exchanger will suffer fouling in unique ways. Fouling of heat exchangers heat exchanger heat transfer. Accounting for fouling in plate heat exchanger design. Different types of heat exchangers are shown in figure 42. Heat exchanger fouling and estimation of remaining useful.
Different fouling deposit structures can lead to underdeposit corrosion of the substrate. Apr 18, 2016 shell and tube heat exchanger fouling factors engineers are often faced with interoffice scheduling traditions. I already calculated current u value with current operating conditions and i have design u value of exchangers from the spec. Lmtd can be calculated by using the following formula, where. For shell and tube heat exchanger, the common method is to use fouling factors. Pdf fouling of heat exchangers hamza shafiq academia. Tm is the log mean temperature difference given as t t.
Fouling depends on the type of heat exchanger, and the kind of fluids being transferred. 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. Here, we will cite only those that are immediately useful for design in shell and tube heat exchangers with sensible heat transfer on the shellside. Examples of components that may be subject to fouling and the corresponding effects of fouling. Fouling factor monitoring posted in industrial professionals. Monitoring the thermal efficiency of fouled heat exchangers core. In order to achieve the desired temperature the cooling water flow rate was drastically reduced to 22. Calculation of fouling factors based on measured extreme temperatures also is possible by using the heat exchanger network calculator approach. Fouling is the accumulation of unwanted material on solid surfaces. Little attention was paid to the heat exchanger fouling and the associated inefficiencies of heat exchanger operation till the socalled oil crisis of the 1970s, when it became vital to make efficient use of available energy.
Heat exchanger analysis and design therefore involves both. The phenomenon usually associated with water systems, e. Traditionally rf is computed from the difference between the two overall thermal resistances takemoto, 1997. Proven dramatic results show it can help companies save thousands of hours of cleaning and millions of dollars in costs every year. 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. Fouling of heat exchangers in processing industries is a chronic operating problem. The fouling level is then translated into an effective flow resistance, pressure.
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. The fouling factor represents the theoretical resistance to heat flow due to. Technologies, design, performance analysis, and building industry trends 1. The worldwide costs, associated specifically with crude oil fouling in preheat trains were equated to around 20% of all heat exchanger fouling mullersteinhagen. 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. The fouling factor represents the theoretical resistance to heat flow due to a build up of a layer of dirt or other fouling substance on the tube surfaces of. Deposition process fouling in a waterintube heat exchanger. Residence time the main restriction of heat exchangerreactors is the short residence time, typically from few seconds to few minutes.
Increased thermal resistance caused by the deposit can normally only be obtained from tests or experience. R d fouling factor or unit thermal resistance of deposit m 2 kw u d overall heat transfer coefficient of heat exchanger after fouling wm 2 k u overall heat transfer coefficient of clean heat exchanger wm 2 k 1 can also be expressed as. Paul watkinson, engineering conferences international, tomar, portugal, july 1 6, 2007 produced by the berkeley electronic press, 2016. 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. Biological fouling may be defined as the growth of living matter on heat exchanger surfaces.
Heat exchanger fouling calculation process heat transfer. Basic heat exchanger performance evaluation method on otec. Pdf use of cfactor for monitoring of fouling in a shell. Fouling factors in heat exchangers resources hrs heat. Introduction hex are designed for thermal processes to work within allowable pressure drop limits and for a specified time period. The two most common heat exchanger design problems are those of rating and sizing. The basic design equation and overall heat transfer coefficient the basic heat exchanger equations applicable to shell and tube exchangers were developed in chapter 1. Estimate the pressure drop across the heat exchanger. Rf 1ud 1uc 1 exact monitoring of rf, addition to ud, needs an updated overall thermal resistance of the exchangers for the new. Fouling and reduced heat transfer in heat exchangers. This means that the plate heat exchanger can remain in service far longer between cleaning intervals. Heat exchanger fouling of course reduces the opportunity for heat recovery with its attendant effect on primary energy.
The heat load of a heat exchanger can be derived from the following two formulas. Shell and tube heat exchangers basic calculations pdh online. Heat exchanger fouling and cleaning vii, july 1 6, 2007, tomar, portugal also, an output information template is filled up with the results of the execution to be retrieved. Fex17 the history and status of research in fouling of heat exchangers in cooling water service 1976 fex18 plate heat exchanger fouling study 1976 fex19 seawater studies of fouling on copper and its alloys 1978. If uncontrolled, levels of fouling can negate any benefits produced by careful heat exchanger design. Pdhonline course m371 2 pdh shell and tube heat exchangers. It was developed over a period of more than five years in close collaboration with the oil industry fouling working party, a team of oil refiners, heat transfer equipment manufacturers and chemical suppliers. However, fouling is a selffulfilling prophecy and the selection of fouling factors or excess area must be done carefully. The fouling factor represents the theoretical resistance to heat flow due to a build. Plate heat exchanger calculation method alfa laval. The development of fouling depends on a number of things, 5 and 16.
Expresstm, novel heat exchanger analysis software for heat exchanger fouling in the preheat train of a crude oil distillation unit. Selection of heat transfer models and fouling coefficients for shell side and tube side. However, calculating the remaining useful life rul of the hx when the fouling is first noticeable has not yet been fully explored. Analysis overview the prediction of the fouling times and energy consequences of coil fouling is based on a model of heat exchanger fouling that we developed specifically for residential heat exchangers. For a new heat exchanger the fouling factor is zero and it increases with time with increased fouling. Shell and tube heat exchanger fouling factors engineers are often faced with interoffice scheduling traditions.
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