Application Of Heat Transfer Enhancement Research Articles

Analytical study and heat transfer analysis of on couple stress flow of hybrid nanofluid over a nonlinear stretching surface

This research paper investigates a two-dimensional couple stress flow of hybrid nanofluid (HN) over a nonlinear stretching surface with heat transfer analysis. HNs are well-known for their exceptional heat transfer properties compared to conventional fluids. The mathematical modeling of the problem involves the formulation of basic governing equations, namely, continuity, momentum and energy equations. To simplify the analysis, a similarity transformation technique is employed to convert the dimensional NLPDEs into dimensionless NODEs. Subsequently, the obtained governing equations are analytically solved using the HAM. The investigation explores the impact of several parameters, including magnetic field inclination, slip parameter, couple stress parameter, nanoparticle volume fraction, nonlinear stretching parameter, EN, thermophoresis parameter and PN. This study presents graphical representations of temperature and velocity distribution to visualize the effects of these parameters on the HN flow. Furthermore, different graphs and tables are employed to explain the impact of the factors on SF and NN. Notably, the results indicate that the HN exhibits significantly enhanced heat transfer properties over the base fluid, particularly under the influence of an inclined magnetic field. This research is expected to contribute to the advancement of the field of condensed nanostructure and nanomaterials, opening new avenues for further exploration in heat transfer enhancement applications.

Heat transfer in heat sinks: An analytical approach based on integral transforms

Heat sinks are crucial components in electronic devices, dissipating heat generated by the device’s components. Analyzing heat transfer in heat sinks is crucial for efficient device design. In this article, an analytical approach is proposed for obtaining temperature field in heat sinks. The approach utilizes a 3D formulation for the base and a 2D formulation for the fins, which are solved using the Classical Integral Transform Technique (CITT) and coupled through eigenfunction expansions to determine the interface contact heat fluxes on each fin. An important advantage of the proposed eigenfunction expansion coupling for the interface heat fluxes is that the transform of the interface heat flux is already included in the analytical expressions for the fins and base. This eliminates the need to use the inversion formula, thus avoiding any additional truncation errors and improving the accuracy of the results. The proposed methodology is demonstrated to be effective through different symmetrical and non-symmetrical test cases using CITT and verifying the achieved results with OpenFOAM simulations. The suitability of the partial lumping approach in the fin’s thickness for heat sink problems is also demonstrated. The proposed methodology provides a reliable and efficient fully analytical solution for heat sinks used in devices that require heat transfer enhancement applications.

Cattaneo-Christov heat flux model in radiative flow of (Fe3O4– TiO2/Transformer oil) and (Cu– TiO2/Transformer oil) magnetized hybrid nanofluids past through double rotating disks

Recent progresses in nanotechnologies and nanoscience have led to the creation of hybrid nanofluids, which are a complicated category of fluids with superior thermal features to regular nanofluids. The current framework demonstrates the importance of a two-dimensional steady incompressible axisymmetric flow of Maxwell hybrid nanofluid over double disks with thermal radiation. This investigation analyzes a novel idea regarding the execution of the Cattaneo-Christov heat theory and melting phenomenon by considering transformer oil as a base fluid. Two dissimilar classes of hybrid nanofluid, Iron–Titanium oxide/Transformer oil (Fe3O4–TiO2/TO) and Copper–Titanium oxide/Transformer oil (Cu–TiO2/TO) have been taken into our research work. The main equations (PDEs)are translated into a present set of ODEs using the necessary similarity variables. In MATLAB, the shooting scheme is utilized to evaluate the numerical and graphical outcomes of physical flow parameters. The radial velocity rose as the volume fraction of nanoparticles increased. The radial velocity field is increased as the porosity parameter is enhanced. The temperature profile is decreased with increasing the values of the thermal redaction parameter. Furthermore, because of the higher compactness of the copper nanoparticles, the addition of the volume fraction of nanoparticles slows the flow profile, and because copper is an excellent conductor of heat, it raises the fluid temperature throughout the domain. The mathematical fallouts also tackle the idea of employing magnetized spinning discs in space engines and nuclear propulsion, and such a model carries useful applications in heat transfer enhancement in a wide range of industrial thermal management devices and renewable energy generation systems.

Forming experiment of extruded tube with crossed ellipsoidal dimples and numerical investigation on heat transfer enhancement and flow characteristics

In this paper, an extruded tube with crossed ellipsoidal dimples was proposed to achieve heat transfer enhancement. This extruded tube was produced by mechanical extrusion, and an experiment was carried out to confirm the validity and rationality of the manufacture. The experimental results revealed that the error between geometric models built by mechanical simulation and actual manufacture was less than 15%. On this basis, the thermo-hydraulic characteristics were analyzed by numerical simulations. The CFD analysis indicated that the extruded tube improves thermo-hydraulic performance because the structure of dimples promotes mixing degree and boundary layer destruction. In addition, the dimensionless number Nu/Nu0, f/f0 and PEC were presented to illustrate the effects of geometry, such as dimple depth, pitch, the semi-major axis of rigid ellipsoidal blocks and dimple configuration. It was found that the maximum PEC = 2.4 was observed when D = 3 mm, P = 25 mm, a = 10 mm and the dimples configuration is cross. The range of Nu/Nu0, f/f0 and PEC for ETCED is 2.1–4.2, 1.75–7.24 and 1.7–2.4. Finally, the overall performance was compared among different enhanced tubes. The results showed that the extruded tube provided better overall performance than other enhanced tubes. The achievement of this paper can be extended to engineering applications in heat transfer enhancement.

Selection of nanoparticles for battery thermal management system using integrated multiple criteria decision‐making approach

The selection of suitable nanoparticles is an important task for their applications as heat transfer promoters for the mitigation of thermal issues in energy storage systems. This paper aims to present a systematic framework for the selection of nanoparticles based on multiple attribute decision-making tools. A hybrid Grey relational analysis-based technique for order preference by similarity to ideal solution (GRA-TOPSIS) approach combining the advantages of both GRA and TOPSIS methodologies is proposed and opted for evaluation, comparison, and ranking of different alternatives under the influence of several objective and subjective criteria weights. The criteria importance through inter-criteria correlation (CRITIC) and entropy weighing methods are employed to determine the objective weights, while the subjective weights are calculated using the analytic hierarchy process (AHP). Also, an attempt is made to present a generalized weight integration formula that combines several objective and subjective weights of attributes. The results demonstrate Al2O3 nanoparticles as the most acceptable alternative. The sensitivity analysis performed proves the robustness and feasibility of the adopted decision framework. Additionally, the rank reversal issue is also addressed to present the qualitative assessment of estimated results. Thus, the evaluation methodology discussed in this paper seems to provide a theoretical reference strategy for nanoparticle selection in heat transfer enhancement applications. Highlights A novel integrated multiple criteria decision making scheme for nanoparticle selection is presented An attempt is made to present a generalized weight integration formula combining several objective and subjective weights of attributes Thermal conductivity and specific surface area are reported as the most significant attributes. Al2O3 is highlighted as the best choice. The sensitivity analysis and rank-reversal test have also been performed to check the robustness of suggested procedures and Al2O3 has outperformed all other alternatives under consideration.

Rational fabrication of superhydrophobic surfaces with coalescence-induced droplet jumping behavior for atmospheric corrosion protection

Coalescence-induced droplet jumping behavior on superhydrophobic surfaces has a potential application in atmospheric corrosion protection by spontaneously removing the corrosive water film/droplets. However, the design guidelines for superhydrophobic surfaces to realize coalescence-induced droplet jumping behavior remain lacking, and the antifogging ability of droplet jumping behavior for atmospheric corrosion protection is unknown. Herein, two kinds of superhydrophobic surfaces, namely, the sheet-like structure superhydrophobic surface and the cluster-like structure superhydrophobic surface, were rationally fabricated over the copper substrate by the different solution-immersion process followed by the same hydrophobized treatment. First, the correlations of the microstructure and droplet jumping behavior of the two surfaces were studied, and a droplet jumping phase map that divided the jumping and non-jumping regions was formulated from the perspective of energy. The sheet-like structure superhydrophobic surface with a higher contact angle and a lower surface roughness is more favorable to droplet jumping behavior due to a lower solid/liquid contact area and interfacial adhesion. Second, the antifogging ability of droplet jumping behavior for atmospheric corrosion protection was experimentally demonstrated. Comparatively, the sheet-like structure superhydrophobic surface presents a superior anti-corrosion performance due to droplet jumping-induced wetting transition. This work offers design guidelines for superhydrophobic surfaces to realize coalescence-induced droplet jumping behavior in self-cleaning, anti-icing/anti-frosting, and condensation heat transfer enhancement applications, and provides insights into designing efficient technologies in the application of atmospheric corrosion protection.

A Modern Review on Jet Impingement Heat Transfer Methods

Abstract Jet impingement cooling is considered as one of the most effective heat transfer enhancement techniques. The primary mode of heat transfer enhancement is due to the flow stagnation. The effectiveness of jet impingement as a cooling technique is well documented; however, the application of jet impingement to different problems has been hindered by inability of manufacturing methods to incorporate impingement systems easily into cooling designs. Impingement heat transfer effectiveness can be further improved by improving the jet strength by modifying the jet holes, enhancing surface features, or adding swirl. With an increased usage of this cooling technique and additional modifications in geometry to further enhance the heat transfer capacity to suit different applications, this paper provides a much-needed review of the advancements in the effectiveness of this cooling technique. A comprehensive look at impingement cooling over a variety of modifications and applications with a focus on improved manufacturing techniques impacting novel design and implementation is provided for a variety of heat transfer enhancement applications.

Radiative MHD bioconvective nanofluid flow due to gyrotactic microorganisms using Atangana–Baleanu Caputo fractional derivative

In this paper, the Atangana–Baleanu Caputo (ABC) sense is applied on the unsteady MHD bioconvection nanofluid boundary layer flow due to gyrotactic microorganisms. The effects of joule heating, convective boundary conditions and thermal radiation, and were studied. Also, it is focused on the Buongiorno’s nanofluid model and two cases of the nanoparticles boundary conditions are assumed, namely, passive control and active control. The solution methodology is starting by an approximation of the time fractional derivatives using ABC and the finite differences method (FDM) of Crank-Nicolson type is applied for the first and second derivatives. The main outcomes revealed that using ABC definitions gives a good approximation of the time fractional derivatives comparing with classical Caputo approximation. Also, values of the velocity and temperature in case of the passive control are higher than those of the active control indicating more physical realistic in this case. Furthermore, there is an enhancement in values of the local Nusselt number up to 0.2% when order of the fractional derivatives is varied from 0.8 to 1. The work finds applications in heat transfer enhancement in bio-inspired nanoparticle-doped fuel cells.

Experimental investigation on thermal-hydraulic characteristics in a traverse rib tube fitted with regularly spaced helical tapes

A synergy enhancement approach by simultaneously combing a traverse rib tube (TRT) with regularly spaced helical tapes (RSHTs) was devised to increase thermal performance of heat exchangers aiming for saving more energy. Air flow heat transfer and pressure drop tests were respectively performed under constant heat flow and isothermal conditions by analyzing different parameters comprising Reynolds numbers, pitch length ratios and space ratios. In contrast to the plain tube, the gained results in the alone use of TRT show that the heat transfer rate and flow resistance are respectively augmented by 35.3%-49.4% and 1.48–1.70 times. By further fitting RSHTs into the TRT, the heat transmission performance and friction loss are increased by about 108.1%-177.0% and 5.97–15.31 times, respectively. The flow patterns are dominated by transverse streams and swirl flows, which render enhanced turbulent intensity and improved fluid mixing in the air flow passage, leading to thermal enhancement. The maximum value in performance evaluation criterion of about 1.26 is achieved by both the TRT and the TRT fitted with RSHTs. Moreover, the empirical formulas are developed from experimental values with deviations within ±5% and ±8% for Nusselt number and friction factor, respectively. Compared with published studies of swirl flow devices, the proposed enhanced apparatus of the TRT fitted with RSHTs in present study can be regarded as a proper candidate for potential heat transfer enhancement applications.

The carbon-nanotube nanofluid sprayed on an unsteady stretching cylinder together with entropy generation

The water-based single- and multiple-wall carbon nanotubes nanofluid over the surface of an unsteady stretched cylinder has been studied. The thin film of the carbon-nanotube nanofluid has been focused for the heat transfer enhancement applications. The well-known thermal conductivity model for the revolving tube materials like single- and multiple-walled carbon nanotubes defined by Xue were used. The modeled problem has been solved through the optimal homotopy analysis method using the BVPh 2.0 package. The distribution of the thin layer has been regulated through the pressure term using the variable thickness of the nanoliquid. The entropy generation has mainly focused during the motion of the thin layer for the both sorts of carbon nanotubes. The important features of the entropy generation and Bejan number under the influence of the physical constraints have been compared for the both types of single-wall carbon nanotubes and multiple-wall carbon nanotubes and discussed. The well-known BVPh 2.0 package of the optimal homotopy analysis method has been used to find the outcomes.

The impact of the magnetic field and viscous dissipation on the thin film unsteady flow of GO-EG/GO-W nanofluids

The unsteady flow of nanoliquid film over a flexible surface has been inspected. The water and ethylene glycol are used as the base liquids for the graphene oxide platelets. The comparison of the two sorts of the nanoliquids has been used for the heat transfer enhancement applications. The thickness of the nanoliquid film kept variable under the influence of applied magnetic field and viscous dissipation. The governing equations for the flow problem have been altered into the set of nonlinear differential equations. The BVP 2.0 package has been used for the solution of the problem. The sum of the square residual error has been calculated up to the 10th order approximations. It has been observed that the graphene oxide ethylene glycol based nanofluid (GO-EG) has more efficient for the heat transfer enhancement as compared to the graphene oxide water based nanofluid (GO-W). The impact of the physical parameters has been plotted and discussed. The problem has been solved through homotopy analysis method (HAM) as described by Liao et al. [26]. This method is frequently used for the solution of nonlinear problems and show that this method is quickly convergent to the approximate solution. This method gives us series solution in the form of function and all the physical parameter of the problem involved in this method.

Influence of Electrode Spacing on a Symmetrical Washer-Type Electrohydrodynamic Conduction Pump

Electrohydrodynamic (EHD) pumping is an attractive method that can be applied to drive a fluid in mass transport and heat transfer enhancement applications, and more particularly for microfluidic applications. EHD pumps are very interesting because they do not require moving parts. The electric energy is directly converted into kinetic energy via the Coulomb force. Three modes can generate this fluid motion: conduction, induction, and injection. This paper presents the experimental results of a parametric investigation on EHD conduction pumps with washer-type electrode geometry. Only symmetrical electrode configuration is investigated in order to highlight the influence of the positive/negative charge mobility ratio. The working fluid is a dielectric liquid (HFE-7100). The pumping mechanism is examined with several washer-type electrode geometries and different types of spacers. For each configuration, pressure and current time variations are recorded and compared.

The Impact of Viscous Dissipation on the Thin Film Unsteady Flow of GO-EG/GO-W Nanofluids

The unsteady flow of nanoliquid film over a flexible surface has been inspected. Water and ethylene glycol are used as the base liquids for the graphene oxide platelets. The comparison of two sorts of nanoliquids has been used for heat transfer enhancement applications. The thickness of the nanoliquid film is kept as a variable. The governing equations for the flow problem have been altered into the set of nonlinear differential equations. The BVP 2.0 package has been used for the solution of the problem. The sum of the square residual error has been calculated up to the 10th order approximations. It has been observed that the graphene oxide ethylene glycol based nanofluid (GO-EG) is more efficient for heat transfer enhancement as compared to the graphene oxide water based nanofluid (GO-W). The impact of the physical parameters has been plotted and discussed.

A Comparative Study of Performance of Low Reynolds Number Turbulence Models for Various Heat Transfer Enhancement Simulations

The goal of this study is to evaluate the computational fluid dynamic (CFD) predictions of friction factor and Nusselt number from six different low Reynolds number k–ε (LRKE) models namely Chang–Hsieh–Chen (CHC), Launder–Sharma (LS), Abid, Lam–Bremhorst (LB), Yang–Shih (YS), and Abe–Kondoh–Nagano (AKN) for various heat transfer enhancement applications. Standard and realizable k–ε (RKE) models with enhanced wall treatment (EWT) were also studied. CFD predictions of Nusselt number, Stanton number, and friction factor were compared with experimental data from literature. Various parameters such as effect of type of mesh element and grid resolution were also studied. It is recommended that a model, which predicts reasonably accurate values for both friction factor and Nusselt number, should be chosen over disparate models, which may predict either of these quantities more accurately. This is based on the performance evaluation criterion developed by Webb and Kim (2006, Principles of Enhanced Heat Transfer, 2nd ed., Taylor and Francis Group, pp. 1–72) for heat transfer enhancement. It was found that all LRKE models failed to predict friction factor and Nusselt number accurately (within 30%) for transverse rectangular ribs, whereas standard and RKE with EWT predicted friction factor and Nusselt number within 25%. Conversely, for transverse grooves, AKN, AKN/CHC, and LS (with modified constants) models accurately predicted (within 30%) both friction factor and Nusselt number for rectangular, circular, and trapezoidal grooves, respectively. In these cases, standard and RKE predictions were inaccurate and inconsistent. For longitudinal fins, Standard/RKE model, AKN, LS and Abid LRKE models gave the friction factor and Nusselt number predictions within 25%, with the AKN model being the most accurate.

Turbulence closure models for free electroconvection

Electroconvection has been simulated in a number of recent studies, given its application in heat transfer enhancement, electrostatic atomizers and flow control. In practical applications, such as in charge injection atomizers, the electric Reynolds number can be sufficiently high such that the well-described ordered large scale electrohydrodynamic (EHD) instabilities that normally appear in electroconvection can dissipate and form into a wider distribution of length-scales. This purely electrohydrodynamically driven chaotic flow has features that resemble turbulent natural convection, and can dominate the operational regime of practical devices. Despite its practical relevance, Reynolds averaged turbulence model closures for EHD are unavailable, which currently makes direct numerical simulation the main viable option for EHD flows. Closure of EHD turbulence in free electro-convection is examined here through implementation of Reynolds stress model (RSM) closures using EHD specific timescales for the unclosed terms appearing in the turbulent scalar flux and space-charge scalar variance equations. A new closure for the highly non-linear triple correlation (q′E′u′¯), a term which is specific to EHD, is also presented. The work demonstrates that Reynolds stress closures are a feasible modeling route for EHD flows, with errors approaching similar values as in thermal Rayleigh–Benard convection at analogous levels of turbulence.

Tiwari-Das nanofluid model for magnetohydrodynamics (MHD) natural-convective flow of a nanofluid adjacent to a spinning down-pointing vertical cone

In this article, the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied. The mathematical model has been formulated based on Tiwari-Das nanofluid model. Three different types of water-based nanofluid with copper, aluminum oxide (alumina) and titanium dioxide (titania) as nanoparticles are considered in this investigation. Two cases of heat transfer analysis are discussed. These are: (i) the spinning cone with prescribed surface temperature and (ii) the spinning cone with prescribed surface heat flux. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of three equations, which is solved numerically using the fourth-order Runge-Kutta method with shooting technique. The current solution demonstrates very good agreement with those of the previously published studies in the especial cases. The effects of the three key thermophysical parameters governing the flow; the nanoparticle volume fraction, the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions, skin friction coefficient, Nusselt number and entropy generation number are presented graphically and discussed in details. Our results demonstrate that, the enhancement of heat transfer is a function of particle concentration, small fraction of metallic particles leading to significant changes in all three quantities of skin friction coefficient, local Nusselt number and entropy generation number. The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction coefficient value, and also copper and titania nanoparticles have the largest and lowest local Nusselt number. Moreover, it is observed that the magnetic parameter has a decreasing effect on both skin friction coefficient and local Nusselt number and an increasing effect on entropy generation number. In addition, our computation shows that all three quantities of skin friction coefficient, local Nusselt number and entropy generation number are the increasing functions of spin parameter. Finally, this simulation represents the feasibility of using magnetic rotating body drives in novel nuclear space propulsion engines and this model has important applications in heat transfer enhancement in renewable energy systems and industrial thermal management.

Cost-effective strategy for heat exchanger network retrofit

Cost-effective retrofit of heat exchanger networks (HENs) remains a significant challenge. This paper explores different methods for achieving cost-effective retrofit. The first part of this article presents a novel methodology for the application of heat transfer enhancement in HEN retrofit with a fixed network structure considering pressure drop constraints. Heat transfer enhancement is a low-cost option. However, heat transfer enhancement on its own without changes to the network structure provides a limited scope for energy reduction. The second part of this paper presents a new pinch retrofit method that identifies network structural changes sequentially to meet the retrofit target. However, the high capital cost associated with installing new heat exchangers, relocating existing exchangers, and augmenting the heat transfer area of existing heat exchangers most often leads to uneconomic retrofits. Low-cost retrofit requires few modifications. Therefore, the third part of this paper combines the new pinch retrofit method with the use of heat transfer enhancement to provide low-cost retrofit by combining the merits of both approaches. A case study highlights the benefits of the new approach.

Bioconvection nanofluid slip flow past a wavy surface with applications in nano-biofuel cells

A theoretical study is presented to examine free convective boundary layer flow of water-based bio-nanofluid containing gyrotactic microorganisms past a wavy surface. Buongiorno's nanofluid model with passively controlled boundary condition is applied to investigate the effects of the emerging parameters on the physical quantities namely, skin friction, Nusselt numbers and density number of motile microorganisms. The effects of the both hydrodynamic and thermal slips are also incorporated. Local similarity and non-similarity solutions are obtained using the seventh-order Runge–Kutta–Fehlberg method (RKF7) coupled with shooting quadrature. In order to compare our numerical results with the existing data, the active mass flux boundary condition is also used to benchmark MAPLE numerical solutions with earlier similar and non-similar solutions for a smooth stationary surface. It is found that the passive boundary condition reduces the skin friction and enhances local Nusselt numbers. Also the wavy surface is found to result in higher skin friction and higher local Nusselt numbers compared with a stationary surface. It is found that motile micro-organism density number is elevated with increasing bioconvection Péclet number whereas the motile micro-organism species boundary layer thickness is reduced with increasing bioconvection Lewis number. The work finds applications in heat transfer enhancement in bio-inspired nanoparticle-doped fuel cells.

Size control synthesis and characterization of ZnO nanoparticles and its application as ZnO-water based nanofluid in heat transfer enhancement in light water nuclear reactor

Abstract A novel and facile approach for size-tunable synthesis of ZnO nanoparticle (NPs) is reported. Size-tuning was attained by using PEG (polyethylene glycol) of molecular weights 400 and 4 000. ZnO NPs was synthesized using homogeneous chemical precipitation followed by hydrothermal. Here triethylamine (TEA) was used as a hydroxylating agent. As-synthesized ZnO NPs were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) analysis. Synthesized ZnO nanoparticle was used for the preparation of ZnO-water based nanofluid and its application in heat transfer enhancement in light water nuclear reactor. In this work, ZnO-water based nanofluid of different volume concentration (1 percnt;, 2 percnt; and 3 percnt;) and particle size of 10 nm and 20 nm is used for enhancement in heat transfer in annular channel by using two phase approach. The particle size of 10 nm gives better result for enhancing the heat transfer rate in comparison to 20 nm particle size in nuclear reactor.

Pressure drop considerations with heat transfer enhancement in heat exchanger network retrofit

The success of heat exchanger network (HEN) retrofit not only lies in the amount of energy savings that can be obtained but also being able to comply with any pressure drop constraints imposed on the network. The techniques used for heat transfer enhancement increase the performance of the heat exchanger but at a penalty of increased pressure drop. In order for a retrofit design with heat transfer enhancement to be realistic, pressure drop must be considered. The effects of heat transfer enhancement on pressure drop can be mitigated by applying different techniques. For shell and tube heat exchangers, the decision on the best technique to apply is dependent on the side that is constrained i.e. shell side or tube side. The variety of options available for pressure drop mitigation can make the process more complex. To effectively solve the problem, a step wise approach for the application of heat transfer enhancement with pressure drop consideration is proposed. The first step is the identification of the heat exchangers that bring about pressure drop violation when enhanced. Pressure drop mitigation techniques can then be applied. Considering there might be multiple mitigation techniques that can be used for a given heat exchanger, a ranking criterion has been defined for the identification of the best modification required. After mitigation techniques have been applied to candidate heat exchangers and the network is no longer constrained by pressure drop, a simple nonlinear optimisation based model is used, together with the new geometry of modified heat exchangers to apply heat transfer enhancement. The objective of the non-linear optimisation model is to maximise the retrofit profit i.e. the difference between profit from energy savings and the total cost of retrofit subject to a specified payback operating period. This is achieved by varying the overall heat transfer coefficient of candidate exchangers and fixing the heat transfer area of existing exchangers to maintain the target temperature of all streams in the network. Heat transfer enhancement, even with pressure drop considerations remains an attractive option for HEN retrofit as the costs associated with changing the network topology are eliminated, and it requires reduced time for implementation.