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Rabas and Taborek correlation, for heat transfer in banks of low fin tubes, Rackett equation (modified) for liquid density Radiation: Radiation shields, in radiation heat transfer, Radiation source analysis, Radiative heat transfer: Radiators, automotive, construction, Radiometers, application in gas radiation property measurement, Radiosity, Stephan's law for, Radiosity-irradiation formulations in radiative heat transfer, Rankine cycle in refrigeration, Rao, B K Raoult's law for partial pressure, Rating of heat exchangers, Rayleigh instability, in free convection, Rayleigh number Reay, D Reboilers: Reciprocal mode integrating sphere, for reflection and transmission measurements in radiation, Rectangles: Rectangular ducts: Rectangular enclosures, free convective heat transfer in: Rectangular fins, for plate fin exchangers Reduced pressure, correlations for pool boiling using, Reference temperature: Refinery processes, fouling in, Reflection, of thermal radiation, from solid surfaces: Reflectivity, of solid surfaces, Reflectometer, heated cavity, Reflux condensers, Refractories, density of, Refractory surfaces, Refrigerants: Refrigerant 11 (Trichlorofluoromethane): Refrigerant 12 (Dichlorodifluoromethane): Refrigerant 13 (Chlorotrifluoromethane): Refrigerant 21 (Dichlorofluoromethane): Refrigerant 22 (Chlorodifluoromethane): Refrigerant 116: Refrigerant plant, entropy generation in, Refrigeration, heat transfer in, Regenerators and thermal energy storage, Regimes of heat transfer, in ducts, single phase flow, Reidel method, for predicting enthalpy of vaporisation, Reinforcing rings, for expansion bellows, Relaminarization, of turbulent flow, Reichenberg method, for effect of pressure on gas viscosity, Relief system design for shell-and-tube heat exchangers with tube side failure, Removal of fouling deposits: Renewable fuels, properties of, Renotherm, heat transfer medium, Repair, of expansion bellows, Residence times, in dryers: Resistance network analysis, Resistance (thermal) due to fouling:
definition of, effect of various parameters on, measurement of,
Measurement and Modelling of Fouling
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A B C D E F G H I J K L M N O P Q R
Rabas and Taborek correlation, for heat transfer in banks of low fin tubes, Rackett equation (modified) for liquid density Radiation: Radiation shields, in radiation heat transfer, Radiation source analysis, Radiative heat transfer: Radiators, automotive, construction, Radiometers, application in gas radiation property measurement, Radiosity, Stephan's law for, Radiosity-irradiation formulations in radiative heat transfer, Rankine cycle in refrigeration, Rao, B K Raoult's law for partial pressure, Rating of heat exchangers, Rayleigh instability, in free convection, Rayleigh number Reay, D Reboilers: Reciprocal mode integrating sphere, for reflection and transmission measurements in radiation, Rectangles: Rectangular ducts: Rectangular enclosures, free convective heat transfer in: Rectangular fins, for plate fin exchangers Reduced pressure, correlations for pool boiling using, Reference temperature: Refinery processes, fouling in, Reflection, of thermal radiation, from solid surfaces: Reflectivity, of solid surfaces, Reflectometer, heated cavity, Reflux condensers, Refractories, density of, Refractory surfaces, Refrigerants: Refrigerant 11 (Trichlorofluoromethane): Refrigerant 12 (Dichlorodifluoromethane): Refrigerant 13 (Chlorotrifluoromethane): Refrigerant 21 (Dichlorofluoromethane): Refrigerant 22 (Chlorodifluoromethane): Refrigerant 116: Refrigerant plant, entropy generation in, Refrigeration, heat transfer in, Regenerators and thermal energy storage, Regimes of heat transfer, in ducts, single phase flow, Reidel method, for predicting enthalpy of vaporisation, Reinforcing rings, for expansion bellows, Relaminarization, of turbulent flow, Reichenberg method, for effect of pressure on gas viscosity, Relief system design for shell-and-tube heat exchangers with tube side failure, Removal of fouling deposits: Renewable fuels, properties of, Renotherm, heat transfer medium, Repair, of expansion bellows, Residence times, in dryers: Resistance network analysis, Resistance (thermal) due to fouling:
definition of, effect of various parameters on, measurement of,
Measurement and Modelling of Fouling
Reversible (minimum) work, in Reynolds number, Reynolds stress models, for turbulence, Rheologically complex materials, properties of: Rheological properties of drag reducing agents Rheology, shear flow experiments used in, Rhine, J M, Ribatski, G, Riblets for drag reduction, Richardson number, Richie, J M, Ring cells, in free convection, RODbaffles, in tube bundles with longitudinal flow, Rod bundles: Rohsenow correlation, for nucleate boiling, Roll cells, in free convection, Roller expansion, of tubes into tube sheets, Rose, J W, Rossby number, Rotary dryer, Rotating drums, heat transfer to particle bed in, Rotating surface, in an annular duct Rotation, as device for heat transfer augmentation, Roughness, surface: Rough walled passages, radiative heat transfer down, Rubber (sponge) balls, in fouling mitigation, Ryznar index for water quality,
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R Resistance (thermal) due to fouling: measurement of,
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Measurement and Modelling of Fouling

DOI 10.1615/hedhme.a.000360

3.17 FOULING IN HEAT EXCHANGERS
3.17.4 Measurement and modeling of fouling

G. F. Hays

A. On-line monitoring of operating heat exchangers

The ability to monitor fouling of operating heat exchangers is especially critical in the heat exchangers that are currently process bottlenecks or have the potential of becoming such, possibly as a result of fouling. However, a significant amount of instrumentation is required. Thus the benefits must be measured against the cost. For complete monitoring of fouling in operating heat exchangers to be achieved, the inlet and outlet temperatures of each fluid must be measured, preferably with Resistance Temperature Device (RTD) technology, and so must the flow rates and pressure drops. Finally, all of the data must be collected and processed in real-time. Data storage and processing may be done on a Distributed Control System (DCS) or on a stand-alone computer. There are a number of very good software programs available for that purpose. One critical aspect of such monitoring is that it must include data trending over a prolonged period.

In some instances, with certain types of processes, there are shortcuts, which may be sufficient. For example, for compressor intercoolers and aftercoolers, one may plot the approach temperature, that is, the temperature of the compressed gas leaving the heat exchanger to the temperature of the entering cooling water. For turbine condensers, a plot of actual vs. ideal vacuum, in mm Hg, may suffice. Ideal vacuum would be, for instance, a plot of mm Hg versus inlet cooling water temperature with zero fouling. In refrigeration machines it may be inlet cooling water temperature versus head pressure.

B. On-line modeling of operating heat exchangers

There are two generally accepted means for modeling process heat exchangers, heat transfer models and pressure drop models. Heat transfer is a more universal technique because it can be used to model either side of a heat exchanger and can be applied to a wider range of heat exchanger designs. On the other hand, pressure drop models can be applied to non-heat transfer applications such as deposition in circulating lines. On-line monitoring usually involves a side stream. The major advantage and disadvantage of on-line modeling is that it must utilize the same circulating fluid as the operating heat exchanger. That is an advantage, because it is the same, including the amount of any anti-foulant/dispersant, which may be in use. If the purpose of modeling is to evaluate another anti-foulant/dispersant technology, that can only be done in addition to what is already in the stream. In order to evaluate an alternate anti-foulant or dispersant as a full substitution, the evaluation must be done either by terminating one treatment and initiating the substitute or use an off-line method such as in the laboratory.

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