Search

Heat transfer can be intensified in shell-and-tube heat exchangers for improved heat transfer performance. Such intensification has been widely studied from the point of view of individual heat exchangers (HEs). The use of heat transfer enhancement in Process Integration has many benefits. First, enhanced heat exchangers require less heat transfer area for a given heat duty because of higher heat transfer coefficients. Second, the heat transfer capacity for the given HE can be increased without changing physical size of the exchanger. Third, the use of enhancement can reduce pumping requirement in some cases, as enhanced HE can achieve higher overall heat transfer coefficients with lower velocities, which may lead to lower friction losses. Using enhancement techniques has practical advantages in Heat Exchanger Network (HEN) retrofit, as it can avoid modification of the network structure. The implementation of enhancement is a relatively simple task that can be easily achieved within a normal maintenance period, allowing production losses to be kept to a minimum level and no civil engineering requirement. This chapter provides an introduction to the enhancement methods of commercial shell-and-tube heat exchangers and their engineering application. The key aspects of enhancing shell-and-tube heat exchangers in HEN retrofit are presented and illustrated with examples involving both energy saving and fouling considerations.

Integration of energy recovery section with thermal desalination systems improves their performance from thermodynamics, economics, and environmental viewpoints. This is because it significantly reduces input energy, heat transfer area, and capital cost requirements. Above all, the system outlet streams can achieve thermal equilibrium with the environment by supplying heat for useful preheating purposes thus reducing the environmental impacts. The plate heat exchangers are generally employed for this purpose as preheaters. The current paper presents a comprehensive investigation and optimization of these heat exchangers for thermal desalination systems applications. An experimentally validated numerical model employing Normalized Sensitivity Analysis and Genetic Algorithm based cost optimization is developed to investigate their performance at assorted operating conditions. The analysis showed that the heat transfer coefficient, pressure drop, and outlet water cost were improved by an increase in feed flow rate. However, with an increased flow rate, the comprehensive output parameter (h/ΔP) decreased due to the high degree increase in pressure drop. Moreover, an increase in the chevron angle reduced the heat transfer coefficient, pressure drop, and water cost. Finally, the optimization lowered the heat transfer area by ~79.5%, capital investment by ~62%, and the outlet cost of the cold stream by ~15.7%. The operational cost is increased due to the increased pressure drop but the overall impact is beneficial as Ctotal of equipment is reduced by ~52.7%.

In this study, electroless plating of nickel, copper, and silver is applied to stainless steel 316 (SUS316) plate heat exchanger (PHE) to enhance thermal-hydraulic efficiency. The electroless plating experiment was first performed on small samples (30 × 30 × 1 mm) to determine optimum control parameters, i.e. solution concentration, current density, etching time prior to commercial PHE. The characteristics of the coating surfaces were indicated by static contact angle, thermal shock, roughness profile, Vickers hardness, SEM images, and EDS analysis. In order to research the effect of each electroless coating on PHE performance, a single-phase water flow heat transfer experiment was performed. The thermal-hydraulic efficiency was evaluated using the Overall Heat Transfer Coefficient (OHTC), Friction Factor, Number of Transfer Units (NTU), effectiveness and Performance of Evaluation Criterion (PEC). As a consequence, aqua regia solution with a volumetric ratio of 1HNO3: 2HCl: 75H2O, a current density of 0.1 A/cm2 and a 12-min etching were determined to be the optimum process parameters for optimizing surface area and minimizing mass loss. After electroless coating, the surface was completely changed from smooth to rough, resulting in a change from hydrophobicity to hydrophobicity, as well as a change in surface morphology. More significantly, all coated PHEs displayed a substantial increase in their performance, as shown by PEC ranging from 1.21 to 1.30 in the case of Silver-coated PHE, followed by 1.20–1.24 and 1.11–1.15 in the case of Copper and Nickel respectively.

The optimisation of heat treatment processes in the dairy industry is of high practical interest. Models are key to understanding and optimising equipment design, operating conditions, energy and water utilization, heating and cleaning cycles and economics. Decades of research have led to the development of many models, however, there is still a lack of understanding about the role and mechanism of denaturation and deposition of proteins from whey solutions. Extensive validation of the more recent thermal and fouling models against experimental data is also incomplete. Here, five sets of detailed data from dynamic experiments in typical Plate Heat Exchangers (PHEs) are used to validate a 2D-distributed, dynamic model under fouling. The model accounts for the exchanger geometry, operating conditions and prevailing local conditions. Three reaction mechanisms for β-lactoglobulin (β-LG) protein unfolding, aggregation and deposition are considered, one of which is novel. First, a validation was carried out of the thermal PHE model alone (i.e. under clean conditions, with no fouling) against a water-water dynamic experiment, with excellent results. The exit temperatures predictions match the experimental observations within

In the passive residual heat removal system of a molten salt reactor, one of the residual heat removal methods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residual heat of fuel salts. An experimental loop is designed and built with a single heat transfer element to analyze the heat transfer and flow characteristics. In this research, the influence of the size of a three-layer thimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are used to obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gas gap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gas gap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. In addition, a natural circulation startup process is described in this paper. Finally, flashing natural circulation instability has been observed in this thimble-type heat transfer element.

The specification design of this heat exchanger has been taken from a real project executed by Clough. The process data given matches the real application exactly and was used to design the heat exchanger. The Regeneration Gas Heater was manufactured in Malaysia, and was shipped to a fabrication yard in Thailand for installation within a pre-assembled module. This paper illustrates fully thermal and mechanical design for this heat exchanger. Here, the redesign takes place to improve the design by reselect different parameters which can enhance the heat transfer through the exchanger. As well as, new correlation is developed to predict Nusselt number for tube side which reduces the error percent with Kern's method from 15.25% to 12.64% based on simulation data. Where, the proposed and Kern's correlations compared against experimental data to show that the proposed correlation is quite accurate. After many iterations, the new design suggested that four tubes passes need to be used with 1.38 m tube length. In addition, the tube arrangement chosen to be square type with 0.9 m shell diameter. With these parameters, the exchanger achieves high enough heat transfer coefficient and the pressure drop within specification.

There exist numerous methods of experimentally testing designs for heat sinks in the laboratory, especially for microscale fluidic devices, which can lead to a problem for comparison between new studies and those in the literature. To explore this issue, laboratory-based experiments on the heat transfer and flow impedance properties of a sample microchannel heat sink were repeated over a varying range of equipment. Three types of heat source (hot plate, film heater and copper block with cartridge heaters), two types of piping (polymer and metal), and the presence or absence of manifolds were investigated and the differences in heat sink performance were noted. Overall, especially in terms of achieving consistent, repeatable results, it was found that the arrangement of copper block heater, metal piping and the inclusion of manifolds was superior for this particular microchannel device. Hence, it is suggested that future testing of heat sinks and heat exchanger devices employ a similar arrangement of equipment for greater accuracy and comparability. In particular, the plastic tubing and hot plate configurations were found to have relatively poor consistency when testing the heat sink, and the film heater produced non-uniform heating, even over a small surface area.

The energy equations of the fluids are applied to different flow arrangements, leading to analytical expressions for the calculation of temperature changes in heat exchangers. The degree of performance is expressed with an effectiveness ɛ, defined as the ratio of actual heat load to maximal possible heat load. As a measure of heat exchanger size or potential, the number of transfer units NTU is used, defined with the lower capacity rate in this analysis. Analytical relationships between NTU and ɛ are given for the following flow arrangements: parallel and counterflow including the case of phase change in one fluid; shell-and-tube heat exchangers with one shell-side and one to four tube-side passes; one-pass unmixed-unmixed, mixed-unmixed, and mixed-mixed crossflow; various multipass crossflow arrangements; parallel and counterflow spiral plate heat exchangers; and plate-fin heat exchangers. Multistream arrangements are considered for plate heat exchangers, shell-and-tube heat exchangers, and plate-fin heat exchangers. Heat transfer and pressure drop correlations are also given for the previous constructions. To facilitate the application of the equations, five rating and sizing examples are presented.

Heat transfer correlations are given for all boiling and condensation regimes relevant for evaporator and condenser design. First, pool boiling is considered with the regimes of natural convection, nucleate boiling and film boiling, and then flow boiling in vertical and horizontal tubes. Flow regimes are described with flow pattern maps. One example is calculated for nucleate boiling on a horizontal tube; the program is attached. Special correlations for heat transfer and friction factor are given for plate heat exchangers. Then, condensation is considered. Heat transfer correlations are given for laminar and turbulent film condensation on vertical plates, horizontal single tubes, and tube bundles and condensation inside tubes under different flow regimes. Special correlations are recommended for condensation in plate heat exchangers. Finally, a cell method is presented for the iterative calculation of the combined heat and mass transfer process during condensation of vapor mixtures.

Heat treatment of milk for hygiene and preservation is carried out in energy integrated pasteurisers units which include several plate heat exchangers (PHEs), a holding tube and ancillary piping. Fouling reduces energy efficiency and cleanings generate downtime and wastes. No detailed dynamic models are currently available of full heating-cleaning cycles for an overall unit. Using a first principle modelling approach, a 2D dynamic thermal model, coupled with semi-mechanistic fouling and cleaning in place (CIP) models, is developed for the whole pasteurisation process, and used to test various heating-cleaning cycles. The model generality and flexibility are demonstrated for high temperature short time (HTST) and ultra-high temperature (UHT) treatments. The whole unit thermal model is validated against experimental data for a HTST process, with excellent agreement. Fouling evolution, distribution and impact are assessed for both processes. A UHT heating-cleaning cycle simulation enables quantifying the amounts of cleaning agent and waste water produced. The new model is suitable for control, optimisation of heating and cleaning strategies, and waste reduction studies.

This chapter addresses the issue of advanced temperature control in plate heat exchangers. The rationale justification of moving to advanced control approaches, even if for classical control, for instance, proportional integral (PI) and proportional integral and derivative (PID) used in more than 90% of industrial processes, is the search of optimization, energy saving, and product quality. Indeed, it is noticed that PID often gives a relatively large variance when controlling temperature, especially when the process is highly nonlinear and contains time delays. In the case of pasteurization temperature control, a higher reference control temperature is often considered to avoid violating the pasteurization temperature (i.e., 72°C). This introduces energy loss as well as overheating the treated product (milk in this case) when the temperature variance is positive, increasing the risk of burning proteins. Advanced control may overcome the problem and help reduce the temperature set point with no risk of violating the pasteurization temperature. In this chapter, some advanced control approaches including an optimal PID tuned using genetic algorithms as well as linear and nonlinear predictive control are proposed as a control alternative and compared with classical approaches.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. A solar assisted ground source heat pump (SAGSHP) system is a promising technology which pairs two widely abundant renewable energy sources, solar and shallow geothermal. In space heating dominated regions, the addition of solar collectors to conventional ground source systems improves their feasibility. There are many aspects which influence the system’s efficiency; but experimentation to optimize these would requires high capital investment and take a very long time. Therefore, mathematical modeling and computer-based simulations are preferable methods to conduct sensitivity and feasibility analyses. In this work, a PVT based solar assisted ground source heat pump system was modeled using TRNSYS program, and sensitivity analyses were conducted. For the PVT collectors, an experimentally verified transient model was utilized, while experimental data were used to validate a novel very shallow borefield. For the heat pump model, manufacturer’s performance data along with a new novel method were combined, and a new component was created in the simulation platform. A single family dwelling with domestic hot water demand was assumed for the heating load, and weather data from Birmingham, West Midlands, UK was used. The simulation results were evaluated by utilizing the annual specific productivity metric rather than the systems seasonal performance factor, which is the current choice for SAGSHP systems. The proposed evaluation approach was found be capable of clarifying, in detail, the effect of the parametric variation on the system’s energy performance. The sensitivity analyses are focused on six parameters on the energy conversion side, with the heat pump’s evaporator as the physical boundary. It was found that the storage capacity and the plate heat exchanger’s effectiveness, contribute the most to the system’s and PVTs’ heat productivity. Whilst heat productivity depended more on the parameters’ variation, the power generation was influenced mainly by the collectors’ tilt. The results of this study are significant for design and operation of these systems.

The current research presents a comprehensive model of a 100 kWe Trilateral Flash Cycle TFC system composed of sub-modules for the plate heat exchangers and twin-screw expanders to assess and identify the operating parameters that mostly affect the TFC performance at off-design conditions. The modelling approach for heat exchangers and piping is based on 1D CFD while considering the operating maps for pump and expander. The simulation process takes into account variations of the heat source temperature and mass flow rate from the design point. The TFC performance is analysed in terms of efficiency and power output while the expander performance is discussed in terms of volumetric and isentropic efficiencies. A sensitivity analysis is carried out to assess the most suitable parameter for control purposes and system performance optimisation. The results point out a large sensitivity of the inlet quality at the expander due to the revolution speed of the machine but also the off-design behaviour of the heater.

Organic Rankine Cycle is one of the most efficient, profitable and feasible technology for low-to-medium temperature heat recovery. The boost to the development of small-scale systems that could easily enter the market poses challenges in the design and selection of components, and in the choice of the operating conditions. This work deals with a micro-scale Organic Rankine Cycle (ORC) unit that has been designed to be cheap, efficient and compact, and tested to analyze performance and transient response under large variations of the heat source temperature. A dynamic model is also built and validated against two sets of experimental data: the first one refers to maximum power operation of the system and the second one to partial load operation close to the occurrence of two-phase expansion. The goal is to understand the potential of the system to face market applications, for which best design choices, operational limits and response time to variable heat sources must be identified. The choice of scroll expander, volumetric pump and plate heat exchangers has been made according to the lowest cost-to-efficiency ratio to keep the investment cost below 2500 euro/kW, already in the pre-market phase, in the power range of 3–4 kW. Results of the experiments show a fast time response, with a prompt reaction of the system to variations of the heat source temperature. Simulations demonstrated the ability of the model to capture with good accuracy the system dynamics. In particular, the validation process at maximum power operation (expander power output of 3300 W) shows maximum relative errors of about 4% in the prediction of measurements, whereas, the validation process at partial load operation yields slightly higher errors, namely 5.2% and 6.6% in the prediction of the evaporation pressure and the expander power output, respectively.

Plate heat exchangers (PHEs), widely used in the food industries, use large amounts of energy. Fouling reduces their thermal and hydrodynamic performance, and requires periodic cleaning (often after few hours), with productivity losses. Cleaning uses large amounts of water and produces wastes. Improving productivity, minimising energy, water and wastes, while ensuring effective pasteurization is of high interest and can be supported by simulation models. Current models describing the dynamic behaviour of PHEs with fouling typically rely on simplified assumptions, with limited predictive ability. More detailed models based on Computational Fluid Dynamics (CFD) are very computationally expensive for complete PHEs, not always better at fitting experimental data, and practically infeasible to use for operations optimisation and control. A 2D distributed, dynamic model described by Guan and Macchietto (2018) for a single PHE channel, is extended to enable the modelling of full PHEs with multiple plates arranged in any design configuration (e.g. with parallel, countercurrent, mixed parallelcountercurrent flow). The model is validated here for two such arrangements (A1 and A2) against experimental results. Four milk fouling models are assessed: two deposition mechanism (due to aggregate or denatured proteins), each with/without deposit re-entrainment. No single model was found capable of describing both arrangements. A1 was predicted best by models with aggregate proteins deposition, A2 with fouling by denatured proteins. A dynamic model for cleaning of fouled surfaces was integrated with the moving boundary model and validated against experimental data. This enabled for the first time in the literature the simulation of Cleaning-in-Place (CIP) procedures, establishing the duration of cleanings, and the seamless simulation of entire single and multiple heating-CIP cycles, with either pre-set or condition-based termination conditions for each phase. It is shown there is large scope for optimising the performance and productivity of overall heating-CIP cycles, and an optimal operation is demonstrated for arrangement A1.

Heat exchanger enhancement technologies have been widely used into heat exchanger networks (HENs) retrofit. However, the heat recovery is limited through the enhancement, which is restricted by the geometry of existing heat exchanger. Plate heat exchangers are widely used in energy-intensive process industries to increase heat recovery and reduce greenhouse gas emissions with the features of small minimum temperature approach and high effectiveness. Thus, plate heat exchangers are taken into consideration to replace conventional heat exchanger in crude oil preheat trains to enhance heat transfer coefficient and reduce energy consumption. A major limitation of applying plate heat exchanger is lack of reliable optimization method to quantity the energy saving effectively. Due to the high installation cost of plate heat exchangers, the optimization is based on the trade-off between energy reduction and capital cost. This work proposes a new methodology of application of plate heat exchanger in HENs retrofit with a fixed network structure. A change in one component in heat exchanger networks can have an effect on other downstream heat exchangers. Therefore, the proposed methodology also presents a way of eliminating the need for additional heat transfer area after replacement, while ensuring the stream target temperatures are met. Case studies highlight the benefits of the new approach.

This paper presents a mathematical programming approach for the design of counter current gasketed plate heat exchangers. The objective function corresponds to the minimization of the heat transfer area and the set of constraints includes the thermofluid-dynamic equations for evaluation of film coefficients and pressure drops, the heat transfer rate equation, and bounds on velocities and pressure drops. We also consider discrete geometric options. The expressions of the objective function and constraints are reformulated into a linear form, without loss of rigor, i.e. the solution of the linear problem is exactly the same of the original one. Therefore, problems related to nonconvergence or multiple local optima with different values of objective function are avoided. An example of a typical design task is employed to illustrate the performance of the proposed approach.

A mathematical model of a plate heat exchanger (PHE) as part of an amine scrubbing process for post-combustion CO2 capture has been developed and implemented in the Institute for the Design of Advanced Energy Systems (IDAES) process system engineering (PSE) framework. The thermal model is based on the effectiveness-Number of Transfer Units (e-NTU) approach where the non-smooth min-max capacitance rates are replaced by smooth functions to improve convergence characteristics of the optimization problem. Parameters for the convective heat transfer coefficient correlations are estimated using the data from National Carbon Capture Center (NCCC). The simulation results are found to be in good agreement with the pilot plant data. The model can be utilized for optimizing PHE designs to maximize energy efficiency.

Geothermal energy can play a vital role in the mitigation of climate change due to its CO2-neutral, renewable and non-fluctuating character. Because of the expensive preparation of the geothermal wells, the thermal water should be utilized with the highest efficiency. Therefore, the wells are often exploited in combined heat and power concepts. Consequently, the power plant operates in part load most of the time. However, this high portion of part load operation is often not fully considered in the design stage of the plant, due to a lack of suitable simulation models. Therefore, the purpose of this paper is to compare several approaches to simulate the part load behavior of the geothermal Kalina power plant in Unterhaching (Germany) and to validate them with operational data. Simulation approaches to calculate the isentropic efficiency of the turbine and the heat transfer coefficients of the heat exchangers are studied and compared on component level. An investigation of different combinations of these component models then follows. The results show that a detailed correlation to model the isentropic efficiency of the turbine is necessary to achieve sufficient accuracy. Furthermore, modeling plate heat exchangers with a power law approach for the heat transfer coefficient appears promising.

A parametric variation followed with Kern’s method of design of extended surface heat exchanger has been made for an unbaffled shell-and-tube heat exchanger problem. For this analysis, the rectangular and trapezoidal fin shapes longitudinally attached to the fin tubes are taken. In comparison with the attachment of trapezoidal fins, it is found that the heat transfer rate was lesser than the rectangular cross section by keeping a constant outer diameter of the shell along with all other constraints of a heat exchanger design, namely, number of passes, tube outer diameter, tube pitch layout, etc. But when the total volume of the fin over a tube was kept constraint, using trapezoidal fins the heat transfer rate is found to be increased and consequently the pressure drop decreases much more than in the case of fins with rectangular cross section. This optimization has shown beneficial results in all the cases of different constraints of heat exchanger design analysis. & 2015 Published by Elsevier Ltd.

Compact convective heat exchangers are becoming increasingly important in various areas of applications dealing with micro-devices. Metallic fiber networks are highly porous materials having certain thermal and mechanical characteristics which offer several advantages for heat exchangers. However, optimization of the material and the structure is subject to several conflicting requirements. A high internal surface area favors rapid heat exchange with the fluid, but may be associated with a relatively low permeability, inhibiting fluid flow. This introduces uncertainty about the optimal scale of the porosity. There are relatively complex interplays between performance, exchanger size, and pore (fiber network) architecture. It is difficult to just use experimental data as a guide, and modeling approaches should be explored.

Efficient heat recuperation is of primary concern in resolving the problem of optimal energy usage. To achieve best results it requires the use of efficient compact heat exchangers among which Plate Heat Exchanger (PHE) is one of the most promising types. Its flexibility allows finding economically viable solutions in different processes of heat utilisation. But the fouling formation on surfaces of plates can lead to energy losses, additional power consumption and the costs of cleaning. This practical operational problem is a significant challenge in the progression towards sustainable development. The traditional two approaches to account for fouling in heat exchanger design are (1) to increase heat transfer surface by employing fixed fouling thermal resistance or (2) by introducing margin for heat transfer surface area. However the reliable data on fouling factors for different streams in PHEs are limited and both approaches can lead to significant errors in estimation of required heat transfer area in PHE, the increase of which can lead to lower flow velocities and higher fouling tendencies. The method of PHE based on the mathematical model accounting for local process parameters distribution along heat transfer surface is proposed. It is incorporating earlier developed fouling model (Arsenyeva et al., 2013). It requires the data of fouling monitoring for any heat exchanger working with considered streams to identify model parameters. Having these data the method can be used for design of new PHEs or for retrofitting the existing PHEs on considered enterprise for optimal performance. The applicability of the method is demonstrated with a case study for PHE working in food industry application. The PHE (290 plates) with heat transfer area 259.2 m2 was initially designed to heat glucose solution by another stream of glucose solution coming with 140 °C. The heavy fouling was observed, which required cleaning after one week of operation due to drop in heat transfer load and increase in pressure drop up to 1 bar. The redesigning of PHE with the proposed method has shown the possibility to decrease heat transfer area to 137.7m2 (155 plates) of the PHE by rearranging plates with different corrugation geometry and reducing their number on the same frame. The monitoring of PHE performance during one year of operation have shown that the same drop in heat transfer load and increase in pressure drop was observed only after a month of operation, the cleaning during that period was not required. It has reduced the capital cost of PHE, operating cost for cleaning and prolonged the service life time of rubber gaskets. The case study demonstrated the ability of the proposed method of PHE design to optimise the PHE performance with proper selection of PHE plates and complete use of available pressure drop to mitigate fouling formation.

Pillow-Plate Heat Exchangers (PPHEs) represent an innovative equipment type, with space-effective, light and pressure-resistant construction. In this work, an experimental study of air cooling by water in small-scale pillow plates was carried out and an analysis of the hydraulic resistance and heat transfer inside the PPHEs was performed based on the experimental data. The correlations for friction factor and heat transfer in PPHEs channels were proposed and validated by the measurements of small-scale PPHEs. The correlation for the heat transfer coefficients in the channel with hot heat carrier is based on the modified Reynolds analogy between heat and momentum transfer; it is valid for fully developed turbulent flow with the Reynolds numbers between 2,000 and 20,000. The deviation of the data predicted by the proposed correlations from the experimental results is within ± 10 %. The experimental data processing was realised using the developed software. The proposed correlations can be applied for the mathematical modelling of PPHE design parameters.

The modelling of plate heat exchangers (PHEs) for dairy applications is revisited utilising recent concepts that have proved very effective in different but related areas, in particular dealing with fouling in tubular exchangers and crude oil refinery applications. The approach initially proposed by Georgiadis and Macchietto (2000) is followed, but coupled with a more detailed 2D distributed model capable of describing and characterising deposit layer growth. The proposed model, illustrated for a single channel in a PHE, includes an improved milk and protein aggregation/deposition model, independent deposition on the plates at each side of the channel, the interaction of local operating conditions and deposit formation (via a moving boundary at the fluid-deposit interface), and the asymmetric deposition due to different boundary conditions at the two sides of a plate. It is shown that the model adequately predicts the distribution of deposit along the plates and provides useful insights into problematic plate regions.

A design problem for a shell and tube heat exchanger that combines a parabolic trough solar collector and an organic Rankine cycle was formed to find the desired output parameters for certain fluid types and operating conditions. The design problem was modeled mathematically and the equations originating from this model were solved using Engineering Equation Solver. A parametric study was then performed to study the effect of some of the important parameters (e.g., pipe diameter, pipe length, and baffle spacing and configuration) on the output parameters (e.g., overall heat transfer coefficient and pressure drop). Furthermore, an exergy assessment was conducted to study the effect of solar radiation and different working fluids on the exergetic efficiency of the shell and tube heat exchanger. The results showed that noncontinuous baffle type yielded a higher shell-side heat transfer coefficient and thus increased the overall heat transfer coefficient. On the other hand, when the solar radiation changed from 800 to 2700 W/m2, the overall heat transfer coefficient decreased from 1579 to 1491 W/m2 K, the heat transfer surface area increased from 7 to 25.25 m2, and the pumping power increased from 0.8723 to 0.9227 kW.

This chapter deals with heat transfer and mass transfer principles that are based on essentially similar physical principles. In principle, they all obey a universal law, similar to the familiar Ohm's law, which can be expressed, in general terms as: the rate of transport (i.e., the quantity transported per unit time) is proportional to the driving force and inversely proportional to the resistance of the medium to the transport. The basic principles of heat and mass transfer are described together while their applications are treated separately. All transport phenomena (fluid flow, heat and mass transfer, electric current etc.) are the result of lack of equilibrium between parts of the system. Heat transfer occurs via three fundamental mechanisms: conduction, convection, and radiation. Conduction refers to the transfer of heat through a stationary medium. Convection occurs when heat travels along with a moving fluid. Radiation is the transfer of heat in the form of electromagnetic radiation. Unlike the former two mechanisms, radiative heat transfer does not require the presence of a material medium between the two points. Further, heat exchangers are devices for the exchange of heat between two fluids separated by a heat conducting partition. Heat exchangers are extensively used in the food industry for heating (e.g., pasteurizers), cooling (chilled water generators), and heat induced phase change (freezing, evaporation). Each one of the two fluids may be confined or unconfined (free), stagnant or flowing. The partition is a heat conducting solid wall, usually made of metal. The design of a heat exchanger usually involves two main domains, namely thermal analysis and hydraulic calculations.

Heat transfer enhancement technologies have been widely used in heat exchanger network (HEN) retrofit due to its relatively low retrofit cost. However, for enhancement to be effective, one of the side film coefficients must be controlling on one of the side that presents a higher magnitude. Alternatively, plate heat exchangers (PHE) have relatively small minimum approach temperature and high heat transfer coefficient, and they do not rely on the differences between coefficients. Applying PHE into retrofit design of HEN is considered as an attractive option as it can enhance heat recovery and reduce energy consumption. The first part of this paper proposes an optimal design of two-stream multi-pass plate heat exchangers, including gasket plate heat exchangers and welded plate heat exchangers. An MINLP model is formulated to minimize the total area of a PHE by selecting the best plate geometries, chevron angle and flow arrangement. The second part of this paper presents a new cost-effective methodology of applying the optimized PHE model in HEN retrofit with a fixed network structure. Sensitivity analysis is used to identify the best heat exchangers to replace. A non-linear optimization based model is formulate to deal with downstream effect after replacement. A case study highlights the benefits of the new approach of applying PHE in HEN retrofit.

Despite the increasing number of Organic Rankine Cycle (ORC) installations at megawatt scale, the waste heat rejected by industrial processes can vary substantially from a few kW to many megawatts. Hence, ORC units with a power output in the range of tens of kilowatts should be developed to tackle the opportunity for heat recovery and business opportunities that can arise from it. In the current research activity, a dynamic model of a small scale ORC system was developed using a commercial software platform. The unit is equipped with two plate heat exchangers, a centrifugal pump and a radial turbine designed and optimized using an in-house code and a commercial 1D modelling tool. The off design behavior of the ORC system has been characterized by varying the inlet conditions of heat source and sink, and the turbomachine’s revolution speeds. Moreover, the response to transient thermal inputs at different time scales has also been investigated. Finally, four control strategies have been compared from the performance and energy efficiency perspectives. The results show that the turbine based regulation strategies achieve better control performance while pump based controls are able to regulate the system by maintaining the net power output closer to the design point.

In this study, the temperature and velocity variations were examined in a solar-geothermal shell and tube heat exchanger (STHX) in a COMSOL Multiphysics environment. The velocity and temperature distributions within the shell, the heat transfer between the shell and tubes, and the exergetic efficiency and heat exchanger effectiveness are examined when the shell-side mass flow rate is varied from 28 to 138 kg/s. As a result of this study, it was observed that when the mass flow rate of shell-side fluid increases, the temperature difference along the heat exchanger decreases, and the shell-side fluid velocity increases. On the other hand, the amount of heat transfer and exergetic efficiency increases with increasing of shell-side mass flow rate. In addition, the effectiveness of the heat exchanger decreases with increasing the shell-side mass flow rate. The aim of this study is to provide guidance to heat exchanger designers and researchers on methods to improve the unit's heat transfer and thermodynamic performance, and methods to reduce the total pressure drop.

Vertical ground heat exchangers (VHEs), in the form of either Borehole Heat Exchanger (BHE) or thermo-active piles, are increasingly being deployed to provide low cost and sustainable heating and cooling to buildings. These are often installed within densely built urban environments, where adjacent foundation systems and underground structures can be affected by soil temperature changes induced by the heat exchangers. Therefore, they need to be considered in the geotechnical design of such structures, which typically involves carrying out two dimensional finite element plane strain analyses in order to assess their stability and performance. In such a scenario, it is common to model a line of heat exchangers as a planar source with one infinite dimension and a heat flux rate calculated by dividing the design extraction rate of a single heat exchanger by their spacing in the out-of-plane direction. This study shows that this approach largely overestimates the generated temperature field and proposes a simplified but accurate procedure to estimate the required heat flux to be applied to the planar heat sources in a 2D analysis. For this purpose, a correction factor, T ∗ , is introduced which is shown to depend on geometric parameters and thermal ground properties.

In this paper the axial heat conduction in an isosceles right triangular microchannel heat exchanger is numerically investigated, for laminar, 3D, incompressible, single-phase, steady state flow. The behaviour of axial heat conduction in the separating wall under different conditions is studied. The solution was obtained by solving the continuity and Navier–Stokes equations for the hot and cold fluids by using the pressure-correction method to obtain the velocity distribution, and then the energy equations were solved for the two fluids and the separating wall simultaneously to obtain the temperature distribution. The governing equations are discretized using finite-volume and the hybrid differencing scheme with FORTRAN code was used. Various parameters that can have effect on the axial heat conduction were investigated. The results showed that, the axial heat conduction plays an important role in a parallel flow microchannel heat exchanger and the factors affecting the local and average axial heat conduction are; Reynolds number (Re), thermal conductivity ratio (Kr), hydraulic diameter (Dh), thickness of separating wall (ts) and channel volume. Increasing of Re, Kr and ts leads to an increase in the axial heat conduction while increasing of Dh and channel volume leads to a decrease in the axial heat conduction.

One of the most common uses of geothermal heat is in recirculation aquaculture systems (RAS) where the water temperature is accurately controlled for optimum growing conditions for sustainable and intensive rearing of marine and freshwater fish. This paper presents a design for RAS rearing tank and brazed heat exchanger to be used with geothermal energy as a source of heating water. The heat losses from the RAS tank are calculated using Geo Heat Center Software. Then a plate type heat exchanger is designed using the epsilon – NTU analysis method. For optimal growth and abundance of production, a Fuzzy Logic control (FLC) system is applied to control the water temperature (29 °C). A FLC system has several advantages over conventional techniques; relatively simple, fast, adaptive, and its response is better and faster at all atmospheric conditions. Finally, the total system is built in MATLAB/SIMULINK to study the overall performance of control unit.

In this paper, heat transfer performance of a 40 cm-length circular heat pipe with screen mesh wick is experimentally investigated. This heat pipe is made of copper with two diam- eters; larger in the evaporator and smaller in the adiabatic and condenser. Three different liquids including water, methanol, and ethanol are separately filled within the heat pipe. Low heat fluxes are applied (up to 2500 W/m 2 ) in the evaporator and constant temperature water bath is used at three levels including 15, 25, and 35 � C in the condenser. Results demonstrate that higher heat transfer coefficients are obtained for water and ethanol in comparison with methanol. Further- more, increasing heat flux increases the evaporator heat transfer coefficient. For the case of methanol, some degradation in heat transfer coefficient is occurred at high heat fluxes which can be due to the surface dryout effect. Increasing the inclination angle decreases the heat pipe thermal resistance.

Non-Darcian forced convection heat transfer over a horizontal flat plate in a porous medium of spherical particles has been studied experimentally. With air as the working fluid, the effects of particle diameter and particles materials of different thermal conductivities were examined. The heat transfer measurements were obtained by heating the test plate under the condition of constant heat flux. The experiments have been made for Reynolds numbers ranging from 105 to 106 based on the test plate length. The porous media used in the experiments were made of glass, rock, and steel covering a wide range of solid thermal conductivity. Particles diameters of 2.7 mm, 4.2 mm, 5.6 mm, 8.1 mm, and 11 mm for rock material and 11 mm particle diameter for glass and steel materials were used. It was found that higher heat transfer coefficients were obtained with larger particle size and higher particle thermal conductivity.

The present article addresses the design, mathematical modelling and analysis of a novel highly exergy-efficient air to air heat exchanger. An intricate design based on an hexagonal mesh is proposed for the cross-sectional area of the heat exchanger with aims to explore the performance gains that can be obtained by exploiting the capabilities and benefits offered by modern fabrication techniques such as additive manufacturing. Special attention is paid to understanding the relationship or trade-off that exists between the overall exergy efficiency of the heat exchanger and its cost. The iterative algorithm used to find the geometrical parameters that yield the best performance in terms of volume of material required per unit of exergy transfer at a certain level of efficiency, as well as the assumptions and simplifications made, are comprehensively explained. It has been found through the analyses carried out performed, which are thoroughly discussed throughout the paper, that if the characteristic dimension of the heat exchanger is scaled up by a factor of n, the volume of material per kW of exergy transfer at certain exergy efficiency will increase by a factor of n squared. This is a very important observation, possibly applicable to other types of heat exchangers, that indicates that performance improves dramatically at smaller scales. The overall performance of the case study presented is satisfactory, a volume of material as low as 84.8 cm3 for one kW of exergy transfer can be achieved with a 99% exergy efficiency.

This paper investigates post-combustion capture in coal-fired power plants equipped with gas separation membranes. Simulations are conducted with the process engineering software, Aspen Plus®, with its Exchanger Design and Rating (EDR) tool utilized for heat exchanger design. The reference power plant chosen for the investigation is the Reference Power Plant North Rhine-Westphalia (RPP-NRW) in Germany. The Polyactive® membrane developed by the project partner, Helmholtz Zentrum Geesthacht, was used in the simulation. Because the membrane has different properties at different working temperatures in order to reach a higher degree of selectivity and less energy consumption, the flue gas should be cooled to 25 °C. This results in an efficient cooling system for the capture process, which merits further development. A rigorous heat exchanger design leads to a significant increase in the pressure drops at each heat exchanger and hence the pressure ratio required by the compression machines. The energy penalty of the membrane CCS system for 57% and 76% degrees of CO2 separation was increased from 4.7%-pts to 5.3%-pts and 7%-pts to 8.3%-pts, respectively, after implementing the rigorous heat exchanger design.

[EN] The use of air conditioning in all-electric cars reduces their driving range by 33% in average. With the purpose of reducing the energy consumption of the vehicle and optimising the performance of the batteries, the mobile air-conditioning can be integrated with the temperature control system of the powertrain by means of a coolant loop. In such layouts, the air-to-coolant heat exchangers must operate efficiently in both air heating and cooling modes. Dynamic simulation tools comprising the entire thermal system are essential to assess its performance. In this context, fast but accurate models of the system components are required. This paper presents the thermal characterisation of a commercial compact louvered-fin flat-tube heat exchanger (heater core) for this novel application, based on an experimental campaign comprising 279 working points that reflect real air-conditioning (heating and cooling) working conditions. A general methodology to fit a single correlation of the global heat transfer coefficient for both dry and wet working conditions is explained. The semiempirical correlation developed is employed in a single-node model of the heat exchanger that requires minimal computation time. The present model predicts the heat transfer rate with an average deviation of 3.5% in the cases with dehumidification and 1.9% in the cases when the heat exchanger remains dry., This work has been supported by the European Commission under the 7th European Community framework program as part of the ICE project ‘‘MagnetoCaloric Refrigeration for Efficient Electric Air-Conditioning”, Grant Agreement no. 265434. B. Torregrosa-Jaime acknowledges the Spanish Education, Culture and Sport Ministry (Ministerio de Educación, Cultura y Deporte) for receiving the Research Fellowship FPU ref. AP2010-2160.

Much of the projected potential promise of supercritical CO2 (sCO2) power generation cycles results from advances in heat exchangers, which greatly influence the overall system efficiency and system size. The heat exchangers in the sCO2 cycle are of three basic types, heaters, recuperators, and coolers. Typical closed Brayton cycles using sCO2 as the working fluid require a high degree of heat recuperation. Future heat exchangers may reduce the cost and increase the performance over the current state of the art with new concepts to transfer heat or new manufacturing methods. Additive manufacturing is one possibility to demonstrate new concepts to effectively transfer heat, which may be beneficial for complex geometry. Similar to conventional enhancements such as turbulators or fins, microstructures could be manufactured on a much smaller dimensional scale, which would be appropriate for the small passages in sCO2 heat exchangers. The microstructure layout and manufacturing method would have to be cost effective and be shown to perform better than conventional surface enhancements.

The basics of forced convection and overall heat transfer regarding fluid streams in contact with plain or finned surfaces are presented, including single phase, boiling, and condensation. Some procedures for predicting the relative film heat transfer coefficients in many different situations are treated in detail, with the specific purpose of outlining the type of approaches involved in this context. Finally, the main types of heat exchangers employed in organic Rankine cycle technology are presented and critically analyzed: tube-in-tube, shell-and-tubes, air-cooled, and plate (both gasketed and brazed) heat transfer apparatuses.

The selection of a proper heat transfer fluid (HTF) is a key factor to increase the efficiency of concentrated solar power plants and therefore, to reduce their internal associated CAPEX (capital expenditures of developing and constructing a plant, excluding any grid-connection charges) and OPEX (operating expenditures from the first year of a project's operation). This paper presents a comparative study of two commercial HTF which are widely used in different industries and CSP plants: thermal oil Therminol VP-1 and silicone fluid Syltherm 800. First, the authors theoretically studied the properties of both HTF based on the data given by the manufactures. Afterwards, the authors experimentally perform the comparison in a two-tank molten salt thermal energy storage pilot plant built at the University of Lleida (Spain). The study is focused on the plate heat exchanger of the facility during several charging processes with a counter flow arrangement. Results from both studies showed that, for the same working conditions, Therminol VP-1 is the best candidate for the above-mentioned purposes due to its higher heat transfer, lower thermal losses and lower power consumption associated to the HTF pump. However, it presents problems a low crystallization point, which should also be considered. The research leading to these results has received funding from Spanish goverment (Fondo tecnológico IDI-20090393, ConSOLida CENIT 2008-1005) and from Abengoa Solar NT. The work is partially funded by the Spanish government (ENE2008-06687-C02-01/CON, ENE2011-22722, ULLE10-4E-1305 and ENE2015-64117-C5-1-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). This project has also received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement NºPIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Jaume Gasia would like to thank the Departament d’Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2017FI_B1 00092). The authors would like to thank Dr. Eduard Oró from Catalonia Institute for Energy Research (Spain) and Dr. Antoni Gil from Massachusetts Institute of Technology (USA) for their help during the initial stages of the experimentation.