Showing papers on "NTU method published in 2003"
25 Jul 2003
TL;DR: In this paper, the authors present a classification of Heat Exchanger design according to the number of fluids and their properties, such as surface heat transfer, flow arrangement, and number of transfer units.
Abstract: Preface. Nomenclature. 1 Classification of Heat Exchangers. 1.1 Introduction. 1.2 Classification According to Transfer Processes. 1.3 Classification According to Number of Fluids. 1.4 Classification According to Surface Compactness. 1.5 Classification According to Construction Features. 1.6 Classification According to Flow Arrangements. 1.7 Classification According to Heat Transfer Mechanisms. Summary. References. Review Questions. 2 Overview of Heat Exchanger Design Methodology. 2.1 Heat Exchanger Design Methodology. 2.2 Interactions Among Design Considerations. Summary. References. Review Questions. Problems. 3 Basic Thermal Design Theory for Recuperators. 3.1 Formal Analogy between Thermal and Electrical Entities. 3.2 Heat Exchanger Variables and Thermal Circuit. 3.3 The ?(Epsilon)-NTU Method. 3.4 Effectiveness - Number of Transfer Unit Relationships. 3.5 The P-NTU Method. 3.6 P-N TU R elat ionships. 3.7 The Mean Temperature Difference Method. 3.8 F Factors for Various Flow Arrangements. 3.9 Comparison of the ?(Epsilon)-NTU, P-NTU, and MTD Methods. 3.10 The ?(Psi)-P and P1-P2 Methods. 3.11 Solution Methods for Determining Exchanger Effectiveness. 3.12 Heat Exchanger Design Problems. Summary. References. Review Questions. Problems. 4 Additional Considerations for Thermal Design of Recuperators. 4.1 Longitudinal Wall Heat Conduction Effects. 4.2 Nonuniform Overall Heat Transfer Coefficients. 4.3 Additional Considerations for Extended Surface Exchangers. 4.4 Additional Considerations for Shell-and-Tube Exchangers. Summary. References. Review Questions. Problems. 5 Thermal Design Theory for Regenerators. 5.1 Heat Transfer Analysis. 5.2 The ?(Epsilon)-NTUo Method. 5.3 The ?(Lambda)-?(Pi) Method. 5.4 Influence of Longitudinal Wall Heat Conduction. 5.5 Influence of Transverse Wall Heat Conduction. 5.6 Influence of Pressure and Carryover Leakages. 5.7 Influence of Matrix Material, Size, and Arrangement. Summary. References. Review Questions. Problems. 6 Heat Exchanger Pressure Drop Analysis. 6.1 Introduction. 6.2 Extended Surface Heat Exchanger Pressure Drop. 6.3 Regenerator Pressure Drop. 6.4 Tubular Heat Exchanger Pressure Drop. 6.5 Plate Heat Exchanger Pressure Drop. 6.6 Pressure Drop Associated with Fluid Distribution Elements. 6.7 Pressure Drop Presentation. 6.8 Pressure Drop Dependence on Geometry and Fluid Properties. Summary. References. Review Questions. Problems. 7 Surface Basic Heat Transfer and Flow Friction Characteristics. 7.1 Basic Concepts. 7.2 Dimensionless Groups. 7.3 Experimental Techniques for Determining Surface Characteristics. 7.4 Analytical and Semiempirical Heat Transfer and Friction Factor Correlations for Simple Geometries. 7.5 Experimental Heat Transfer and Friction Factor Correlations for Complex Geometries. 7.6 Influence of Temperature-Dependent Fluid Properties. 7.7 Influence of Superimposed Free Convection. 7.8 Influence of Superimposed Radiation. Summary. References. Review Questions. Problems. 8 Heat Exchanger Surface Geometrical Characteristics. 8.1 Tubular Heat Exchangers. 8.2 Tube-Fin Heat Exchangers. 8.3 Plate-Fin Heat Exchangers. 8.4 Regenerators with Continuous Cylindrical Passages. 8.5 Shell-and-Tube Exchangers with Segmental Baffles. 8.6 Gasketed Plate Heat Exchangers. Summary. References. Review Questions. 9 Heat Exchanger Design Procedures. 9.1 Fluid Mean Temperatures. 9.2 Plate-Fin Heat Exchangers. 9.3 Tube-Fin Heat Exchangers. 9.3.4 Core Mass Velocity Equation. 9.4 Plate Heat Exchangers. 9.5 Shell-and-Tube Heat Exchangers. 9.6 Heat Exchanger Optimization. Summary. References. Review Questions. Problems. 10 Selection of Heat Exchangers and Their Components. 10.1 Selection Criteria Based on Operating Parameters. 10.2 General Selection Guidelines for Major Exchanger Types. 10.3 Some Quantitative Considerations. Summary. References. Review Questions. Problems. 11 Thermodynamic Modeling and Analysis. 11.1 Introduction. 11.2 Modeling a Heat Exchanger Based on the First Law of Thermodynamics. 11.3 Irreversibilities in Heat Exchangers. 11.4 Thermodynamic Irreversibility and Temperature Cross Phenomena. 11.5 A Heuristic Approach to an Assessment of Heat Exchanger Effectiveness. 11.6 Energy, Exergy, and Cost Balances in the Analysis and Optimization of Heat Exchangers. 11.7 Performance Evaluation Criteria Based on the Second Law of Thermodynamics. Summary. References. Review Questions. Problems. 12 Flow Maldistribution and Header Design. 12.1 Geometry-Induced Flow Maldistribution. 12.2 Operating Condition-Induced Flow Maldistribution. 12.3 Mitigation of Flow Maldistribution. 12.4 Header and Manifold Design. Summary. References. Review Questions. Problems. 13 Fouling and Corrosion. 13.1 Fouling and its Effect on Exchanger Heat Transfer and Pressure Drop. 13.2 Phenomenological Considerations of Fouling. 13.3 Fouling Resistance Design Approach. 13.4 Prevention and Mitigation of Fouling. 13.5 Corrosion in Heat Exchangers. Summary. References. Review Questions. Problems. Appendix A: Thermophysical Properties. Appendix B: ?(Epsilon)-NTU Relationships for Liquid-Coupled Exchangers. Appendix C: Two-Phase Heat Transfer and Pressure Drop Correlations. C.1 Two-Phase Pressure Drop Correlations. C.2 Heat Transfer Correlations for Condensation. C.3 Heat Transfer Correlations for Boiling. Appendix D: U and CUA Values for Various Heat Exchangers. General References on or Related to Heat Exchangers. Index.
2,672 citations
TL;DR: In this paper, the influence of mass transfer on heat transfer rates and on the heat transfer coefficient was identified and the relative significance of each heat transfer mechanism was evaluated, and the role of spacers in heat transfer improvement was analyzed.
545 citations
TL;DR: In this article, the authors present a method to evaluate the characteristics and performance of a single stage lithium bromide (LiBr) -water absorption machine, where the necessary heat and mass transfer equations and appropriate equations describing the properties of working fluids are specified.
428 citations
TL;DR: In this paper, a literature search is presented on plate heat exchangers and new correlations for evaporation heat transfer coefficient and friction factor are introduced, which are applicable to various system pressure conditions and plate chevron angles.
Abstract: Plate heat exchangers are used regularly in the heating, ventilating, air conditioning, and refrigeration industry. There is an urgent need for detailed and systematic research regarding heat transfer and the fluid flow characteristics of these types of exchangers. As an initiative in this respect, a literature search is presented on plate heat exchangers. New correlations for evaporation heat transfer coefficient and friction factor are introduced, which are applicable to various system pressure conditions and plate chevron angles. The correlations are based on actual field data collected during several years of installation and operation of chillers, and they are intended to serve as design tools and perhaps as a starting point for future research.
285 citations
TL;DR: In this article, a one-dimensional analytical method is used to analyse the influence of the design parameters of the heat exchanger on the thermo-hydraulic performance and a relation is derived for the specific pressure drop, linking thermal effectiveness with pressure drop of the air inside the tube.
219 citations
TL;DR: In this paper, experiments on the evaporation heat transfer and pressure drop in the brazed plate heat exchangers were performed with refrigerants R410A and R22, and the empirical correlations of Nusselt number and friction factor were suggested for the tested PHEs.
216 citations
TL;DR: In this paper, the effect of dimensionless parameters on the characteristics of heat transfer in a closed-end oscillating heat pipe (CEOHP) was studied and the results showed that the correlation equation could be used to predict the heat flux and that the operation map could predict the operational range and the inner diameter.
123 citations
TL;DR: In this paper, the temperature transient response of a single-phase fluid and a wall in a heat exchanger is investigated for when the other constant temperature fluid is subjected to a step change in temperature or when the single phase fluid is subject to an increase in mass flow rate.
89 citations
TL;DR: In this paper, the authors present a numerical model of a heat exchanger in which the effects of axial conduction, property variations, and parasitic heat losses to the environment are explicitly modeled.
85 citations
TL;DR: In this paper, a quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchanger.
Abstract: Taking the fluid temperature distribution along the borehole depth into account, a new quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchangers. On this basis the efficiency of the borehole has been defined and its analytical expression derived. Comparison with the previous two-dimensional model shows that the quasi-three-dimensional model is more rational and more accurate to depict the practical feature of the conduction of geothermal heat exchanger, and the efficiency notion can be easily used to determine the inlet and outlet temperature of the circulating fluid inside the heat exchanger.
79 citations
TL;DR: In this article, the authors proposed a method of data reduction that improves the predictions of correlations obtained from heat exchanger measurements using genetic algorithms, simulated annealing and interval analysis.
TL;DR: In this paper, a new methodology is proposed to include pressure drop and fouling effects in heat exchanger network synthesis, as well as in retrofit designs, and the results show differences between heat exchangers, with and without the detailed design, relative to heat transfer area, fouling and pressure drop.
TL;DR: In this article, heat transfer coefficients in a liquid/solid fluidized bed heat exchanger are investigated for application in ice slurry generators and a range of temperature driving forces are determined in which ice slurgery generation is stable.
TL;DR: In this paper, a numerical method was employed to divide the heat exchanger in a number of sections, for which fluid properties, capacity rates and heat transfer coefficients were considered constant.
TL;DR: In this paper, an iterative technique is developed and reported for accurate estimation of heat transfer coefficients in a helical triple tube heat exchanger based on the experimental temperature rise of whole milk.
10 Feb 2003
TL;DR: In this article, the authors investigated the temperature and velocity profiles in banks with circular finned-tubes in cross flow and found that the boundary layer developments and horseshoe vortices between the adjacent fins and tube surface are dependent substantially on the fin spacing and Reynolds number.
Abstract: Numerical Investigation of Air-Side Heat Transfer and Pressure Drop in Circular Finned-Tube Heat Exchangers The present numerical study has been carried out to investigate the temperature and velocity profiles in banks with circular finned-tubes in cross flow. The purpose of this investigation is to develop satisfactory correlations and concurrently providing complements to the local convective characteristics. The coolant passes through the tubes, which are maintained at a constant temperature and the dry air is used as the convective heat transfer medium. To demonstrate the influence of the geometric parameters, numerical investigations are carried out for different finning geometries and number of rows. In addition, attempts are made to validate which tube configuration is more constructive. A large computational effort is involved for the memory access of the computers and computing time for the simulation of the complex geometries associated with the dense grids. The available computational fluid dynamics software package FLUENT is applied to determine the related problems. Renormalization group theory (RNG) based k ε turbulence model is allowed to predict the unsteady three-dimensional flow and the conjugate heat transfer characteristics. The numerical flow visualization results reveal the important aspects of the local heat transfer and flow features of the circular finned-tube bundles. These include boundary layer developments between the fins, the formation of the horseshoe vortex system, the local variations of the velocity and temperature on the fin geometries and within the bundles. The boundary layers developments and horseshoe vortices between the adjacent fins and tube surface are found to be dependent substantially on the fin spacing and Reynolds number. The local temperature distributions over the fin surface vary both circumferentially and radially, and there is no significant difference over the fin surface and in the middle of the fin for both tube arrays. To determine the optimum dimension of the geometries, comparisons are prepared in terms of the bundle performance parameter. These data indicate that for the benefit of pumping power, the in-line array has a better performance than the staggered arrangement at low Reynolds number. However, the margin between the inline and staggered arrays becomes narrower when the Reynolds number is increased. The average heat transfer and pressure drop results for both tube configurations are presented. All proposed correlations, based on the numerical and relevant experimental data, are recommended for a wide range of Reynolds numbers (based on the air velocity through the minimum free flow area and the tube outside diameter) from 5 x 10 to 7 x 10. The heat transfer and pressure drop results agree well with several existing experimental correlations. The present numerical investigations suggest a good estimate of the Nusselt number and Euler number for circular finned-tube heat exchangers.
1 Jan 2003
TL;DR: In this paper, a simulated annealing method is employed with a trained neural network representing the heat transfer and pressure drop characteristics of a specified tube bank, and three types of micro bare-tube heat exchanger are designed and compared to conventional commercial heat exchangers.
Abstract: An optimal design methodology is proposed for micro bare-tube heat exchangers. A simulated annealing method is employed with a trained neural network representing the heat transfer and pressure drop characteristics of a specified tube bank. A commercial CFD code, FLUENT5, is used to obtain the heat transfer and pressure drop data sets for in-line tube bundles, which are then used to train the neural network. Three types of micro bare-tube heat exchangers are designed and compared to conventional commercial heat exchangers. The optimized micro bare-tube heat exchangers show better performance than conventional gas-liquid heat exchangers.
Patent•
8 Aug 2003
TL;DR: In this article, a heat exchanger for delivery of heat transfer fluid to a process heat transfer surface is provided, where the heat exchange is in contact with a process fluid and the heat surface comprises at least five heat transfer conduits each having a cross sectional area for the flow path of less than 2000 square millimetres.
Abstract: A heat exchanger for delivery of heat transfer fluid to a process heat transfer surface is provided, the heat exchanger is in contact with a process fluid and the heat transfer surface comprises at least five heat transfer conduits each having a cross sectional area for the flow path of less than 2000 square millimetres wherein the linear velocity of the heat transfer fluid through the heat transfer conduits is from 0.5 to 20 m.s-1 and adapted so that the temperature of the heat transfer fluid changes by at least 1 °C when they system is operating at design load, the exchanger enables more accurate temperature measurement and control in physical and chemical reactions. Also provided is a heat transfer system in which the heat transfer conduit for passage of the heat transfer fluid is attached to an expansion plate which is in contact with the heat transfer surface and enables independent movement of the heat transfer conduit and the heat transfer surface as their temperature change due to changes in temperature and/or pressure.
Journal Article•
TL;DR: In this article, an analytical solution expression for the non-steady temperature field generated by a finite length linear heat source in semi infinite large media is presented, by comparing the time required for the temperature field to attain a nominal "steady state".
Abstract: Analyses and discussions were conducted of a non steady heat transfer model for the vertical embedded pipe of a geothermal heat exchanger. With the use of a virtual heat source and Green function method obtained is an analytical solution expression for the non steady temperature field generated by a finite length linear heat source in semi infinite large media. By way of comparison with a steady state temperature field solution discussed is the time required for the temperature field to attain a nominal "steady state". Meanwhile, an analysis is performed of the temperature field when it has reached a steady state. In this connection a mistake that appeared in current textbooks was indicated. Two representative steady state borehole wall temperatures, i.e., the temperature at the middle of the borehole and the integral mean temperature along the borehole, are defined. A comparison of the difference between these two temperatures has led to a simplified calculation formula, suitable for engineering applications. On the basis of the above analyses discussed further is the impact of the annual imbalance between heating and cooling loads of geothermal heat exchangers on their long term performance.
1 Jan 2003
TL;DR: In this paper, it is shown that the Arithmetic Mean Temperature Difference (AMTD), which is the difference between the average temperatures of hot and cold fluids, can be used instead of the log mean temperature difference (LMTD) in heat exchanger analysis.
Abstract: In this paper, it is shown that the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids, can be used instead of the Log Mean Temperature Difference (LMTD) in heat exchanger analysis. For a given value of AMTD, there exists an optimum heat transfer rate, Qopt , given by the product of UA and AMTD such that the rate of heat transfer in the heat exchanger is always less than this optimum value. The optimum heat transfer rate takes place in a balanced counter flow heat exchanger and by using this optimum rate of heat transfer, the concept of heat exchanger efficiency is introduced as the ratio of the actual to optimum heat transfer rate. A general algebraic expression as well as a chart is presented for the determination of the efficiency and therefore the rate of heat transfer for parallel flow, counter flow, single stream, as well as shell and tube heat exchangers with any number of shells and even number of tube passes per shell. In addition to being more intuitive, the use of AMTD and the heat exchanger efficiency allow the direct comparison of the different types of heat exchangers.Copyright © 2003 by ASME
TL;DR: In this article, the effects of air-side fouling and cleaning on the performances of various condenser coils used in unitary air-conditioning systems were investigated, and the authors concluded that a periodic application of the specified cleaning technique will be effective in maintaining the thermal performance of the condenser coil.
Abstract: An experimental study was conducted to investigate the effects of air-side fouling and cleaning on the performances of various condenser coils used in unitary air-conditioning systems. A total of six condenser coils with different fin geometry and row number were tested. Performance tests were performed at three different conditions: clean-as-received, after fouling, and after cleaning. In all cases, it was observed that the fouling was mostly confined to the frontal face of the heat exchanger as reported in the previous investigations. The amount of deposited dust was more dependent on fin geometry for the single-row heat exchangers than for the double-row heat exchangers. The predominant effect of fouling was to cause a more significant increase in air-side pressure drop than a degradation in heat transfer performance. For the single-row heat exchangers, the pressure drop increased by 28 to 31%, while the heat transfer performance decreased by 7 to 12% at the standard air face velocity of 1.53 m/s depending on fin shape. For the double-row heat exchangers, the pressure drop increased by 22 to 37%, and heat transfer performance decreased by only 4-5% at the same air face velocity. Once the contaminated coils were cleaned according to the given cleaning procedure the original performance of the heat exchangers could almost be recovered completely. The pressure drop could be restored within 1 to 7% and the heat transfer performance could be recovered to within 1 to 5% of the originally clean heat exchangers. Therefore, it is concluded that a periodic application of the specified cleaning technique will be effective in maintaining the thermal performance of the condenser coils.
Patent•
23 Sep 2003
TL;DR: In this paper, a process and system for condensing a multi-component fluid is described, where the process and the system are designed to provide a substantial increase in a heat transfer coefficient during condensation of multichannel fluids resulting in a drastic reduction in size and cost of heat exchangers.
Abstract: A process and system for condensing a multi-component fluid is disclosed, where the process and system are designed to provide a substantial increase in a heat transfer coefficient during condensation of multi-component fluids resulting in a drastic reduction in size and cost of heat exchangers need to condense such fluids. The system and method includes a plurality of heat exchangers and at least one scrubber and splitters and mixers supporting streams that allow a mixed stream to be supplied to each heat exchange unit having parameters designed to increase, optimize or maximize the heat transfer coefficient in each heat exchanger.
Journal Article•
TL;DR: In this paper, the authors investigated the impact of groundwater advection on the performance of geothermal heat exchangers in ground-coupled heat pump systems, and an analytical solution was obtained for a line heat source in an infinite porous medium by means of the Green function analysis.
Abstract: A ground heat exchanger is devised for extraction or injection of thermal energy from/into the ground. In order to investigate the impact of groundwater advection on the performance of geothermal heat exchangers in ground-coupled heat pump systems, a governing equation of conduction-advection is established, and an analytical solution is obtained for a line heat source in an infinite porous medium by means of the Green function analysis. Being clear and concise, the solution of this transient two-dimensional problem has never been found in literature. On this basis an explicit expression has also been derived of the mean temperature on circles around the heat source. Dimensionless criteria that dictate the process are then summarized; influence of the groundwater flow on the heat transfer in ground heat exchangers is discussed accordingly. The analytical solution has provided a theoretical basis and practical tool for design and performance simulation of the ground heat exchangers.
1 Jan 2003
TL;DR: In this article, the authors present the results of an experimental study of heat transfer and pressure drop during condensation of refrigerant R410A inside a horizontal 9.4 mm I.D. tube.
Abstract: This paper presents the results of an experimental study of heat transfer and pressure drop during condensation of refrigerant R410A inside a horizontal 9.4 mm I.D. tube. The experiments were conducted at nominal pressures of 80% and 90% of the critical pressure of R410A. A novel technique that addresses the conflicting requirements imposed by the need for accurate measurement of low heat transfer rates for the small quality increments, and delineation of the tube-side heat transfer coefficient from the overall resistance, was used. Local heat transfer coefficients and pressure drops were measured for the mass flux range 200 < G < 800 kg/m2 -s in small quality increments over the entire vapor-liquid region, spanning several different two-phase flow regimes. These data were compared with the heat transfer and pressure drop data obtained under similar conditions for R404A by Jiang and Garimella [1]. The data were also compared with available correlations for condensation heat transfer according to the applicable flow regime to assess the validity of these models for refrigerant blend condensation at near-critical pressures. Possible explanations for deviations between the data and the models in the literature are also provided.Copyright © 2003 by ASME
1 Jan 2003
TL;DR: In this paper, a large number of heat exchanger data were collected from shell and tube heat exchangers of the Razi Petrochemical Complex (Iran) and the fouling deposits were analyzed with respect to appearance and composition.
Abstract: Multistage evaporators are frequently used in phosphoric acid plants to increase the concentration of dilute phosphoric acid to 52-55 wt% P2O5. The concentrated phosphoric acid solution is supersaturated with respect to calcium sulfate. As a result, part of the calcium sulfate in the liquor deposits on the heat exchanger tube walls. Since the thermal conductivity of these scales is very low, thin deposits can create a significant resistance to heat transfer. Therefore, regular cleaning of heat exchangers is required, frequently at less than biweekly intervals. As the major costs in modern phosphoric acid plants are the cost of energy, a thorough understanding of the fouling kinetics and of the effects of various operational parameters on the behavior of calcium sulfate is required to improve operation and design of the shell and tube heat exchangers, which are extensively used. In this investigation, a large number of heat exchanger data were collected from shell and tube heat exchangers of the phosphoric acid plant of the Razi Petrochemical Complex (Iran) and the fouling deposits were analyzed with respect to appearance and composition. The overall heat transfer coefficients and fouling resistances were evaluated at different times and a kinetic model for the crystallization fouling was developed. It is shown that the crystallization rate constant obeys an Arrhenius relationship with activation energy of 57 kJ/mol. The predictions of the suggested model are in good agreement with the plant data.
Journal Article•
TL;DR: In this paper, the temperature distribution of fluid working media along borehole depth direction was investigated and the heat transfer process in the borehole of a vertical embedded tube geothermal heat exchanger was derived.
Abstract: In pursuit of a more advanced study of ground source heat exchangers the temperature distribution of fluid working media along borehole depth direction was investigated. By analyzing the heat transfer process in the borehole of a vertical embedded tube geothermal heat exchanger derived was an analytical expression of the efficiency of the said exchanger. Thus, it is possible to abandon the irrational assumptions contained in former simplified models and provide a more accurate and rational theoretical basis as well as a calculation method for the design and simulation of geothermal heat exchangers.
1 Jan 2003
TL;DR: In this article, it was shown that the functional dependence of the efficiency of these heat exchangers on this parameter is identical to that of a constant area fin with an insulated tip, and a general algebraic expression as well as a generalized chart was presented for the determination of the heat exchanger efficiency with any number of shells and even number of tube passes per shell, when the Number of Transfer Units (NTU) and the capacity ratio are known.
Abstract: The heat exchanger efficiency is defined as the ratio of the actual heat transfer in a heat exchanger to the optimum heat transfer rate. The optimum heat transfer rate, qopt , is given by the product of UA and the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids. The actual rate of heat transfer in a heat exchanger is always less than this optimum value, which takes place in a balanced counter flow heat exchanger. It is shown that for parallel flow, counter flow, and shell and tube heat exchanger the efficiency is only a function of a single nondimensional parameter called Fin Analogy Number. Remarkably, the functional dependence of the efficiency of these heat exchangers on this parameter is identical to that of a constant area fin with an insulated tip. Also a general algebraic expression as well as a generalized chart is presented for the determination of the efficiency of shell and tube heat exchangers with any number of shells and even number of tube passes per shell, when the Number of Transfer Units (NTU) and the capacity ratio are known. Although this general expression is a function of the number of shells and another nondimensional group, it turns out to be almost independent of the number of shells over a wide range of practical interest. The same general expression is also applicable to parallel and counter flow heat exchangers.Copyright © 2003 by ASME
TL;DR: In this paper, the authors present a simple probabilistic approach to characterize various fouling models that are commonly encountered in many industries and investigate the impact on risk based thermal effectiveness, overall heat transfer coefficient and the hot-and cold-fluid outlet temperatures of a plate-and-frame heat exchanger.
Abstract: Plate-and-frame heat exchangers (PHEs) operating in process industries are fouled to a greater or lesser extent depending on surface temperature, surface condition, material of construction, fluid velocity, flow geometry and fluid composition This fouling phenomenon is time-dependent and will result in a decrease in the overall heat transfer coefficient and increase in the pressure drop of the PHE Once the overall heat transfer coefficient decreases to a minimum acceptable level, cleaning of the equipment becomes necessary to restore the performance In this paper, we present a simple probabilistic approach to characterize various fouling models that are commonly encountered in many industries These random fouling growth models are then used to investigate the impact on risk based thermal effectiveness, overall heat transfer coefficient and the hot- and cold-fluid outlet temperatures of a PHE All the results are presented in a generalized form in order to demonstrate the generality of the risk-based procedure discussed in this paper