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Heat exchangers are widely used in petrochemical and other industries. Improving the efficiency of heat exchangers to increase energy utilization is crucial. Passive enhanced heat transfer technology is widely studied in heat exchanger research due to its low energy consumption and simple operation. Helical baffle–corrugated tube heat exchangers have not been extensively studied as a promising new class of these devices. This paper investigates the key structural parameters of a helical baffle-corrugated heat exchanger through numerical simulation. This study focuses on the factors affecting heat transfer and flow resistance performance. The results show that reducing the helical angle from 28.42° to 10.81° increases the total heat transfer coefficient by approximately 20%. The overall performance of the heat exchanger is evaluated using the efficiency evaluation coefficient (EEC). Optimal levels of each structural factor are determined for different working conditions based on this evaluation. [ABSTRACT FROM AUTHOR]

The potential of hybrid nanofluids to boost thermal efficiency of heat exchanger systems is the focus of this review study. The primary focus is on addressing the associated issues of nanoparticle clumping, system obstruction, and reduced efficacy of heat exchanger due to increased fluid thickness. Accordingly, this review intends to demonstrate the innovative practices (experimentally and theoretically) that helps improving the heat transfer and thermal performance of heat exchangers. In this regard, a critical analysis is conducted to appraise the experimental and numerical simulations, which introduce the impact of different nanoparticle concentrations and compositions on heat exchanger thermal performance. The findings of this review has shown that the hybrid nanofluid of CuO–Cu/water has the greatest thermal performance factor (1.065), following Al2O3–Cu/water (1.055), and Cu–TiO2/water (1.039). Also, the utilization of turbulator heat exchangers has enabled improving the thermal performance by 126 % with a 6 % rise in volume fraction at the maximum Reynolds number. This study underlines the need for further research into novel nanomaterial combinations, fine-tuning of fluid characteristic, and comprehensive stability assessments to enhance the utilization of hybrid nanofluids in heat exchanger systems. Finally, discussions of limitations associated with such systems and proposed potential solutions will lead to a valuable contribution in the possible future development of cost-effective heat exchanger systems. [ABSTRACT FROM AUTHOR]

Heat exchangers are necessary in most engineering systems that move thermal energy from a hot source to a colder location. The development of additive manufacturing technology facilitates the design and optimization of heat exchangers by introducing triply periodic minimal surface (TPMS) structures. TPMSs have shown excellent mechanical and thermal performance, which can improve heat energy transfer efficiency in heat exchangers. This current study intends to design and develop efficient, lightweight heat exchangers for aerospace and space applications. Using the TPMS structure, a porous construction encloses a horizontal tube that circulates heated fluid. Low-temperature water circulates inside a rectangular box that houses the complete system to remove heat from the horizontal pipe. Three porous structures, the gyroid, diamond, and FKS structures, were employed and examined. Porous models with various porosities and surface areas (15 cm2 and 24 cm2) were investigated. The results revealed that the gyroid structure exhibits the highest Nusselt number for heat removal (Nu max = 2250), confirming the highest heat transfer and lowest pressure drop among the three structures under investigation. The maximum Nusselt number obtained for the FKS structure is less than 1000, whereas, for the diamond structure, it is near 1250. A linear variation in the average Nusselt number as a function of the structure surface area was found for the FKS and diamond structures. In contrast, nonlinearity was observed in the gyroid structures. [ABSTRACT FROM AUTHOR]

Thermal storage technology has received increasing attention under the policy of encouraging the development of renewable energy and new clean energy. Optimizing the heat exchange system of phase change thermal storage heat exchangers to obtain better performance has become increasingly urgent. This study comprehensively investigated the actual process of heat transfer and assessed the heat transfer correlation laws between the heat transfer fluids, heat exchange tubes, fins, and phase change materials. Taking the heat exchange efficiency of the heat exchanger as a guide, a simulation was conducted on the effect of the presence and quantity of fins as well as the flow rate of the cooling liquid on the heat exchange efficiency of the heat exchanger. The simulation results showed that too many or too few fins were not conducive to improving heat transfer efficiency. In addition, no positive correlation was observed between the flow rate of the cooling liquid in the heat exchanger and the heat transfer efficiency of the heat exchanger. Specifically, models with slightly slower cooling liquid flow rates had a higher heat transfer efficiency. After a sensitivity analysis, it was found that the number of fins had a more significant effect on the heat transfer efficiency of the heat exchanger than the flow rate of the cooling liquid. The heat exchanger with five fins and a cooling liquid flow rate of 0.1 m/s demonstrated the best heat transfer effect, achieving a temperature drop of 14.76% within 5 min. [ABSTRACT FROM AUTHOR]

The design of a microchannel heat exchanger can be achieved using various approaches. The design includes various materials, such as ceramics, silicon, metals, and polymers, that are used to make microchannels, depending on their specific requirements. Polymers such as silicon, glass, and other polymeric materials are utilized on metallic substrates. The current study includes microchannels fabricated from metallic copper. Further, the design solutions do not consider the implications of the second law of thermodynamics. Hence, performing an energetic analysis of microchannels is imperative to design and assess thermodynamic systems that use them efficiently. One technique to improve a thermodynamic system's efficiency is using a well-designed microchannel heat exchanger with excellent energetic performance. This can be achieved by creating a thermodynamic system that eliminates energetic losses and limits only unavoidable losses. The use of high-conductivity material like copper also achieves this. To identify possible reasons for exergy loss and perhaps address them, a thorough energetic analysis of an existing heat exchanger is necessary. A microchannel heat exchanger with 19 microchannels in a flat tube is considered for this study. The study finds the energetic losses, which are useful for the thermal design of the heat exchanger. [ABSTRACT FROM AUTHOR]

In the present study, using a combination of theoretical discussions, practical examples, and case studies, we sought to gain a comprehensive understanding of how numerical solutions could be used to improve the design and optimize the thermal efficiency of a heat exchanger that utilizes wastewater to reduce the domestic consumption of hot water. To this end, we developed a validated numerical model. We also carried out simulations and experiments, the results of which are presented in this paper. The novelty of this work derives from our use of a new heat exchanger design for a domestic shower, and from the presented experimental–numerical evidence that proves its efficiency. We found that use of our newly designed appliance improved thermal efficiency from 14% to 27%. Moreover, we estimated that the cost of manufacturing and installing such a device did not exceed that of a widely available drain grid. Using our newly designed exchanger, a family of four living in Poland could save EUR 38 (at 2022 values) and reduce CO2 emissions by 192 kg. An average European family could save EUR 68 and reduce CO2 emissions by 76 kg. [ABSTRACT FROM AUTHOR]

The heat exchanger is a core component of all thermal systems. Thus, high-efficiency heat exchangers that can save energy and material are required. Heat transfer improvement in heat exchangers by applying the newly designed fin configuration increases the heat exchanger efficiency. Moreover, the newly designed finned heat exchanger improved heat transfer, resulting in a significant reduction in the heat exchanger size. A compact countercurrent water–water heat exchanger with a high rate of heat transfer while using the least amount of space was achieved. The newly designed finned tube on the outer surface of the inner tube in this study increased the heat transfer characteristics of the double-pipe heat exchanger. An insulated Perspex shell with an inner diameter of 54 mm, 2000 mm in length, and 3 mm thick. Copper tubes with and without rectangular copper fins are studied and compared. The smooth copper tube was 2250 mm in length with 20 mm and 22 mm inner and outer diameters, respectively. The experimental results showed that the Nusselt number and effectiveness of the newly proposed finned tube increased by 95% and 127%, respectively, compared to those of the smooth tube at the same Reynolds number, while the heat transfer coefficient increased by 53% over a smooth tube. [ABSTRACT FROM AUTHOR]

This research introduces an Artificial Intelligence (AI) based model designed to concurrently optimize energy supply management, biocide dosing, and maintenance scheduling for heat exchangers. This optimization considers energetic, technical, economic, and environmental considerations. The impact of biofilm on heat exchangers is assessed, revealing a 41% reduction in thermal efficiency and a 113% increase in flow frictional resistance of the fluid compared to the initial state. Consequently, the pump's power consumption, required to maintain hydraulic conditions, rises by 9%. The newly developed AI model detects the point at which the heat exchanger's performance begins to decline due to accumulating dirt, marking day 44 of experimentation as the threshold to commence the antifouling biocide dosing. Leveraging this AI model to monitor heat exchanger efficiency represents an innovative approach to optimizing antifouling biocide dosing and reduce the environmental impact stemming from industrial plants. [ABSTRACT FROM AUTHOR]

Researchers and engineers are actively working on enhancing the efficiency of heat exchangers in engineering applications by developing novel designs, exploring new materials, and utilizing nanofluids. Three kinds of nanofluids with varying concentrations are investigated in this paper. The objective is to assess the performance of N‐shaped double‐pipe heat exchanger used in thermoelectric power plants. The performance has been evaluated using COMSOL Multiphysics software. The findings show that higher nanofluid concentrations resulted in elevated heat transfer coefficients and improved efficiency of N‐shape double pipe heat exchanger. The analysis revealed that a mere 1% rise in the volume fraction of nanofluids enhanced the efficiency of the heat exchanger on average 23% when compared to the base fluid (water). In comparison to the N‐shape double pipe (Inconel 625) heat exchangers, the N‐shape double pipe (copper) heat exchangers appear to be more efficient. The introduction of nanoparticles has a notable impact on the heat transfer coefficients. Specifically, within an N‐shaped double pipe (copper) heat exchanger, the inclusion of a 1% volume fraction results in a 2.09% enhancement in the heat transfer coefficient for Al2O3/water, a 1.3% improvement for Fe3O4/water, and a 1.15% increase for TiO2/water. It also exposed that adding 1% Al2O3/water led to a significant 0.623% increase in effectiveness, while TiO2/water showed a 0.259% rise, and Fe3O4/water exhibited a 0.375% improvement. Moreover, increasing the Reynolds number enhances the Nusselt number for Al2O3/water and Fe3O4/water nanofluids by 55.22%, and for TiO2/water by 54.60% at a 6% volume concentration, leading to additional increases in exchanger efficiency. Therefore, the augmentation in nanofluid concentration leads to a reduction in the temperature pinch points both at the intake and outflow. This observation suggests that nanofluids exhibit a superior ability compared to conventional fluids when it comes to effectively lowering temperatures. [ABSTRACT FROM AUTHOR]

To achieve carbon neutrality and address global energy supply issues by 2050, there is active progress in the industrial sector for waste energy recovery and commercialization projects. It is necessary to consider both the energy recovery efficiency and economic feasibility based on the production volume for the resource utilization of waste energy, along with eco-friendly processing methods. In this study, a waste heat recovery system was designed to recover a large amount of thermal energy from high-temperature exhaust gases of gas engines for power generation by using biogas produced from organic waste in industrial complexes. Types and sizes of components for a waste heat recovery system that were suitable for various engine sizes depending on biogas production were designed, and the energy recovery efficiency was analyzed. The waste heat recovery system consisted of a smoke tube boiler that generated superheated steam at 161 °C under 490 kPa of pressure from the exhaust gas as the heat source, along with two economizers for heating both supply water and hot water. Heat exchangers that were suitable for three different engine sizes were configured, and their performance and energy flow were calculated. In particular, when operating two engines with a power output of 100 kW, the boiler showed the highest steam production efficiency, and the superheated steam production from high-temperature exhaust gas at 600 °C was designed to be 191 kg/h, while hot water at 58 °C was designed to be produced at 1000 kg/h. In addition, further research on the heat exchanger capacity ratio confirmed that it was within a certain range despite the difference in heat exchanger capacity and efficiency depending on the engine size. It was confirmed that the heat exchange capacity ratio of the boiler was important as an optimal-capacity design value for the entire system, as it ranged from 46% to 47% of the total heat exchanger size. [ABSTRACT FROM AUTHOR]

Heat exchangers enable processing plants to maintain maximum performance over time when handling variable process conditions. The most frequent heat exchanger issues, however, can occasionally be far more challenging to fix, resulting in high capital expenses and rising running costs. Consequently, there is a crucial need to redesign the current heat exchanger for improved performance. In this work, a shell and tube-type heat exchanger is designed with the help of CREO 8.0 parametric software. Transient thermal analysis is done to the designed model using ANSYS 2022 R2 software to investigate different shell and tube heat exchanger materials and assess the heat exchanger for its efficiency and temperature gradient. These results can be used to design appropriate heat exchangers in stationary energy systems, including power plants and fuel cell systems. [ABSTRACT FROM AUTHOR]

The present study investigates the effects of using a magnetic field on the flow field and heat transfer of ferromagnetic Fe3O4/H2O nanofluid considering two-phase model for nanofluid in heat exchanger equipped with helical ribs. Three methods are employed to enhance the thermal efficiency of heat exchanger, as employing of corrugations, utilizing nanofluid as heat transfer fluid, and employing the magnetic field. The performance evaluation criteria index (PEC) is employed to analyze the thermal-hydraulic characteristics of the heat exchanger. The main aim is to achieve an optimum model with the highest performance evaluation criteria value. Usaging of corrugated heat exchanger or nanofluid can increase the average Nusselt number and friction factor in the tube sharply. Also, it is understood that the presence of a magnetic field has a significant effect on the heat transfer enhancement inside the heat exchanger. The model with magnetic field of 600 G has the highest Nusselt number ratio among all studied models, which is followed with 400 G, 200 G, and 0 magnetic fields, respectively. Furthermore the effects of different corrugation heights, widths, and pitches have been studied. Finally, usage of the novel corrugated heat exchanger with 14 mm corrugation heights, 9 mm rib width, and 12.5 mm blade pitches filled with nanofluid, and under a magnetic field of 600 G it suggested as the most efficient configuration. Also, at the Reynolds number of 4,000, the highest performance evaluation criteria values are achieved. [ABSTRACT FROM AUTHOR]

The paper is dedicated to an issue of the influence of a nonuniform flow of mediums in a cross-flow water-air heat exchanger, the core of which is a bundle of elliptical finned tubes. The main purpose of the work is to determine the impact of non-uniform water inflow for various mass flow rates on the thermal efficiency of the heat exchanger. Multivariate analyses were carried out for various temperatures of water, and for measured nonuniform air distribution at the heat exchanger input. Two variants of water distribution were considered: non-uniform water distribution assumed considering a non-uniform air inflow and water distribution resulting from hydraulic resistances calculated for different locations of water inlet and outlet nozzles. Simulation results were compared with the experimental outcomes obtained in cases of the non-uniform natural inflow of both mediums and to the computation results for a case of the uniform media inflow. The results obtained in this work confirm the significant deterioration of the thermal efficiency of heat exchangers caused by a non-uniform media inflow (by as much as 18.5% compared to the case of a uniform media inflow) which is compliant with other numerous works. The control of the water flow through the individual heat exchanger tubes enables the improvement of thermal efficiency by 4.5% to 18.6% compared to the device with uncontrolled inflow of working fluids, which for some of the analyzed cases is even better than a completely uniform inflow of heat carriers. [ABSTRACT FROM AUTHOR]

At the city gate gas pressure reduction stations (CGSs), to prevent natural gas from forming a hydrate in the throttle valve, the natural gas is heated by the heater before reaching the pressure relief valve. Heat exchangers are an essential component of industrial processes that contribute significantly to total system energy. Since the element impacting heat exchanger performance is the fouling process, all fouling processes and models were dynamically simulated in this study. Through coding in the C++ language and simultaneous use of fluent functions, or, in other words, user‐defined function (UDF), fouling‐related models were defined for this software. The dynamic simulation was performed, and parameters such as fouling strength and layer thickness were calculated. The effects of changing operating conditions, such as gas inlet velocity, surface temperature, and fouling species concentration on fouling growth, were also evaluated. As the concentration of fouling species increased, the fouling rate also increased. The amount of supersaturation and fouling rate increased as the surface temperature increased. Due to the operational limitations of the system, to reduce the fouling rate, the gas inlet velocity should be as high as possible, and the fluid inlet temperature, surface temperature, and concentration of fouling species should be as low as possible. In this study, the required time to reach the efficiency of 70% of the heat exchanger was calculated using the modelling of this chamber, which was equivalent to 190 days. Additionally, the critical thickness of the fouling layer at this time was 3.5 cm. [ABSTRACT FROM AUTHOR]

Optimizing the efficiency of conventional heat exchangers is critical for improving the performance of various processes. This study proposed increasing the heat dissipation buffer space of heat exchangers by filling the gap between the heat exchanger and the shell with phase‐change materials for optimizing phase‐change heat exchangers. Comparative simulation analyses were performed by investigating the difference between the internal and external diameters of the inner ring ribs of the heat exchanger, the flow rate of the cooling liquid, the spacing distance, and the number of the inner ring ribs as independent variables. The results revealed that the heat transfer efficiency of heat exchangers can be improved by adding the inner ring rib structure to the heat exchange copper tube. The difference between the inner and outer diameters of the inner ring rib considerably influences heat dissipation. Furthermore, a sensitivity coefficient of 0.2457 can be obtained. The distance and number of inner ring ribs and the flow rate of cooling liquid exhibit certain effects on the heat transfer efficiency of the heat exchanger. The sensitivity coefficients were 0.1477 and 0.0935. The heat dissipation efficiency of the coil heat exchanger was improved by 3.8% by adding inner ring ribs in the coil heat exchanger channel. [ABSTRACT FROM AUTHOR]

The thermal efficiency of heat exchangers, heat sinks, solar heaters, etc., could be optimized by improving the heat transfer in the system without increasing the exergy destruction. It is important to consider pressure loss as well as heat transfer enhancement to increase overall energy efficiency. One of the most effective methods to increase heat transmission with minimal pressure drop penalty is by deploying vortex generators. In this paper, a detailed review of the synergy angle, angle of attack, friction factor, Nusselt number, flow configuration, Reynolds number, and the impact of geometry of the vortex generators on the enhancement of heat transfer and exergy is presented. The principles of field synergy and exergy are utilized to predict the thermo-hydraulic performance of the vortex generators. Different geometries of vortex generators such as rectangular, delta, trapezoidal winglets, and other novel geometries of vortex generators are installed in varied flow configurations and analyzed based on field synergy and exergy principles which were not the matter of interest in review papers in the past. [ABSTRACT FROM AUTHOR]

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The high demand for compact heat exchangers has led researchers to develop high-quality and energy-efficient heat exchangers at a lower cost than conventional ones. To address this requirement, the present study focuses on improvements to the tube/shell heat exchanger to maximize the efficiency either by altering the tube's geometrical shape and/or by adding nanoparticles in its heat transfer fluid. Water-based Al2O3-MWCNT hybrid nanofluid is utilized here as a heat transfer fluid. The fluid flows at a high temperature and constant velocity, and the tubes are maintained at a low temperature with various shapes of the tube. The involved transport equations are solved numerically by the finite-element-based computing tool. The results are presented using the streamlines, isotherms, entropy generation contours, and Nusselt number profiles for various nanoparticles volume fraction 0.01 ≤ φ ≤ 0.04 and Reynolds numbers 2400 ≤ Re ≤ 2700 for the different shaped tubes of the heat exchanger. The results indicate that the heat exchange rate is a growing function of the increasing nanoparticle concentration and velocity of the heat transfer fluid. The diamond-shaped tubes show a better geometric shape for obtaining the superior heat transfer of the heat exchanger. Heat transfer is further enhanced by using the hybrid nanofluid, and the enhancement goes up to 103.07% with a particle concentration of 2%. The corresponding entropy generation is also minimal with the diamond-shaped tubes. The outcome of the study is very significant in the industrial field and can solve many heat transfer problems. [ABSTRACT FROM AUTHOR]

A study of heat recovery in a façade ventilation unit was carried out under laboratory conditions using a climate chamber that allowed stable outdoor and indoor conditions to be simulated. The unit, equipped with a reversible fan and a chamber for the heat exchanger, controlled by an automation control system, was designed to exchange air in the room by alternating supply and exhaust cycles of specific durations. Three types of heat exchangers were tested, which were filled with different phase change materials, in order to estimate the efficiency of the façade ventilation unit in terms of its heat recovery capability. The efficiency of the unit was determined based on the temperature efficiency of heat recovery for 144 setting combinations. The best efficiency results between 73.56% and 76.29% were obtained with a solution using a heat exchanger consisting of cylinders with an external diameter of 10 mm and a wall thickness of 1 mm filled with jojoba oil in a one minute cycle. The tests confirmed that the heat exchangers, which are part of the façade ventilation unit, fulfil their function and allow heat recovery from the exhaust air to pre-heat the supplied air. The study complements the existing scientific knowledge on the efficiency of heat exchangers filled with phase change material, operating in winter conditions with work cycles up to 5 min. [ABSTRACT FROM AUTHOR]

The fouling factor is a complex non-linear function of several feature variables. Accurate estimation of this measurable factor is applicable for controlling the heat transfer efficiency of heat exchangers. Artificial neural network (ANN) and adaptive neural-based fuzzy inference system (ANFIS) techniques are accurate approaches for the understanding treatment of the most complicated systems. The cascade-feedforward (CFF), multi-layer perceptron (MLP), radial basis function (RBF), and generalized regression (GR) neural networks and ANFIS were applied for predicting the fouling factor of the hot wire probe from some measured variables using a huge databank, including 1870 empirical dataset. Pearson's and Spearman's techniques confirmed the highest relation between considered features and the first order of fouling factor. The results demonstrate that the cascade feed-forward neural network containing eight hidden neurons was the best artificial intelligence (AI) model with excellent overall AARE = 3.44 %, MSD = 0.0000315, RMSD = 0.0056, and R2 = 0.9982. This work's significance lies in presenting an applicable and accurate tool for estimating fouling factors on hot wire probes to the research community and industry. This model can be considered a reliable replacement for empirical analyses that are often expensive and time-consuming. [Display omitted] • Hot wire probe has used in academic studies of fouling in heat transfer surfaces. • Five powerful artificial intelligence models are used for fouling factor estimation. • The Levenberg-Marquardt is found as the best training algorithm. • An accurate CFF neural network with eight neurons in one hidden layer developed. • Effects of less studied and various independent variables on fouling is simulated. [ABSTRACT FROM AUTHOR]

A novel efficiency reduction model to tubular heat exchanger based on heat transfer losses by biofilm adhesion is proposed, which included a modified equation based on the real data-dependent time, seawater, hydrodynamics and heat transfer resistance using computational fluid dynamics (CFD). The biofilm growth model based on Verhulst model and experimental data has been obtained and simulated in a CFD software tool to analyze the tubular heat exchanger performance prediction cooled by seawater. The biofilm CFD model with appropriate fit, and the correlation coefficient (R2) values are between 0.97 and 0.99, was validated by experimental data obtained at different flow velocity. The final results of in/outlet difference temperatures were from 3.9 °C to 2.2 °C for different flow velocity with R2 > 0.97. The simulation results demonstrate that the novel CFD model is capable of predicting the efficiency losses during the development period of biofilm growth in in open-loop cooling seawater systems. [ABSTRACT FROM AUTHOR]

The present research utilizes an inverse 3D CFD technique, coupled with the least squares approach and laboratory temperature readings, to predict the suitable turbulence flow model and unknown heat transfer rates within a cubic hot box. This enclosure features four cylindrical horizontal tubes arranged in a diamond configuration, functioning as heaters to generate heat within the space. Furthermore, the heat dissipation from each tube, flow field and temperature contours are also established. The energy equation for tubes and the governing equations for air are solved by coupling. The present estimates are obtained assuming a constant heat transfer rate. The range of the Rayleigh number is from 60,294 to 76,824. Testing various turbulence models revealed that the zero-equation turbulence model reduces the root mean square discrepancy between the simulated thermal behavior and laboratory outcomes compared to other methodologies. To verify the chosen flow model’s accuracy, the Nusselt numbers and flow field distributions aress compared with existing correlations and interferometer photographs. The maximum errors between the estimates of heat loss and heat transfer rate and the corresponding values from previous studies are 44 and 28% for St = 0.036, 34 and 3% for St = 0.045, and 37 and 18% for St = 0.054. To assess the impact of tube surface and spacing on the flow field model, calculation results are compared with those from four square-arranged tubes, revealing a lack of existing studies on this specific investigation. [ABSTRACT FROM AUTHOR]

Heat exchanger studies have been conducted for several decades since the beginning of the development of heat transfer theories due to their widespread use in various industries. The ongoing research topics include heat exchanger efficiency, design parameter optimization, material development, and heat transfer technology exploration. Research has been continued to evolve nanofluid compositions, concentrations, and operating conditions that affect heat exchanger efficiency. They have used hybrid nanofluids in heat exchangers, which contain multiple types of nanoparticles or nanoparticles with additional additives, as hybrid nanofluids improve thermal performance. As a result, the development and optimization of hybrid nanofluids as a working medium in heat exchangers are gaining popularity, and the use of hybrid nanofluids in heat exchangers has already drawn a lot of interest as a viable strategy in industrial sectors. Therefore, such a surge of interest in using hybrid nanofluids in heat exchangers has resulted in a significant body of literature on this. In this review paper, the authors aim to incorporate the findings of these studies and offer a thorough evaluation of the state-of-the-art research on the application of hybrid nanofluids in various types of heat exchangers. This review provides a synopsis of the published literature on the efficacy of heat exchangers utilizing hybrid nanofluid. The researchers have also encountered and documented several challenges, including stability and aggregation, improving thermal conductivity, fluid flow characteristics, corrosion and material compatibility, cost and scalability, and determining the ideal size and shape of nanoparticles while considering environmental and health concerns. In addition, this review identifies research gaps in preventing agglomeration, ensuring nanoparticle dispersion, optimizing fluid composition to minimize flow effects, exploring and identifying materials compatible with hybrid nanofluids, investigating cost-effective methods for hybrid nanofluid production, and addressing scalability issues for widespread implementation in industrial heat exchangers. This review paper will be a valuable resource for researchers and practitioners seeking to overcome these challenges and advance the field of hybrid nanofluids for heat exchanger applications. [ABSTRACT FROM AUTHOR]

Compact heat exchangers for heat removal has become one of the most effective cooling techniques. In this paper, numerical scheme to simulate conjugated heat transfer using additively manufactured heat exchanger is presented. A lattice structure as porous medium is used as effective cooling techniques for heat removal. The objective of these lattices is to transmit heat from the hot part to the cold part while letting the system benefit from two phenomena, heat conduction and convection. An optimization procedure using response surface method is proposed for the presented compact heat exchanger to improve the efficiency. This method was introduced in order to reach the global optimum with a limited number of computer experiments. Two optimization variables are identified: edge thickness for the lattices and the inlet velocity. A constraint optimization problem is formulated to maximize the heat flux through the heat exchanger. Hence at the same time, limiting the increase of the pressure drop and the decrease of the exit temperature. [ABSTRACT FROM AUTHOR]

Featured Application: Cooling of Power Electronic Devices, Electromechanical Machines, Thermoelectric Devices, and Bioengineering Applications. The capabilities of nanofluids in boosting the heat transfer features of thermal, electrical and power electronic devices have widely been explored. The increasing need of different industries for heat exchangers with high efficiency and small dimensions has been considered by various researchers and is one of the focus topics of the present study. In the present study, forced convective heat transfer of an ethylene glycol/magnesium oxide-multiwalled carbon nanotube (EG/MgO-MWCNT) hybrid nanofluid (HNF) as single-phase flow in a heat exchanger (HE) with elliptical corrugated tubes is investigated. Three-dimensional multiphase governing equations are solved numerically using the control volume approach and a validated numerical model in good agreement with the literature. The range of Reynolds numbers (Re) 50 < Re < 1000 corresponds to laminar flow. Optimization is carried out by evaluation of various parameters to reach an optimal case with the maximum Nusselt number (Nu) and minimum pressure drop. The use of hybrid nanofluid results in a greater output temperature, a higher Nusselt number, and a bigger pressure drop, according to the findings. A similar pattern is obtained by increasing the volume fraction of nanoparticles. The results indicate that the power of the pump is increased when EG/MgO-MWCNT HNFs are employed. Furthermore, the thermal entropy generation reduces, and the frictional entropy generation increases with the volume fraction of nanoparticles and Re number. The results show that frictional and thermal entropy generations intersect by increasing the Re number, indicating that frictional entropy generation can overcome other effective parameters. This study concludes that the EG/MgO-MWCNT HNF with a volume fraction (VF) of 0.4% is proposed as the best-case scenario among all those considered. [ABSTRACT FROM AUTHOR]

Numerical analysis is carried out on heat transfer performance of industrial-length double-tube heat exchanger, by using hybrid nanofluid as a coolant with the effect of external magnetic field. The double-tube heat exchanger contains two tubes, namely inner and outer, and has lengths of 1.39 m and 1.03 m, respectively. The hot oil passes into the outer tube, and the coolant (hybrid nanofluid) passes into the inner tube. Two types of hybrid nanofluids are used for this investigation: (a) CNT-Al2O3/water and (b) CNT-Fe3O4/water. Volume fraction and Reynolds number are considered as 0.1% to 0.5% and 800 to 2400, respectively. This study is carried out with mixture model wherein the equations are solved with control volume approach combined with second-order upwind scheme. Results indicate that Nusselt number is found higher for CNT-Fe3O4/water hybrid nanofluid in the presence of magnetic field. On using hybrid nanofluid, higher thermal efficiency and better performance index of heat exchanger are achieved. The effectiveness increased nearly ~ 30% at higher Reynolds number with Ha = 20. About 40% better performance index is achieved at lower Reynolds number for CNT-Fe3O4/water when compared with CNT-Al2O3/water hybrid nanofluid. Increment in thermal efficiency of heat exchanger is improved almost 30% by increasing the Reynolds number. [ABSTRACT FROM AUTHOR]

• The model of external fin backfill coupled heat exchanger was established. • The thermal performance of FBCHE were simulated. • The materials and structures of different fins are compared. • The heat transfer factors affecting FBCHE were analyzed. There are abundant geothermal resources in mine goaf. The effective exploitation of geothermal energy is of great significance to realize the long-term sustainable development of mines. In this paper, a three-dimensional unsteady heat transfer model of a typical serpentine backfill coupled heat exchanger is established using COMSOL Multiphysics simulation software, and the accuracy of the model is verified. A serpentine external finned backfill coupled heat exchanger is proposed. Comparative analysis of the heat transfer performance of serpentine external finned backfill coupled heat exchanger and smooth backfill coupled heat exchanger is conducted. The effects of different fin materials, fin structures and system design parameters on the thermal performance of serpentine external finned backfill coupled heat exchanger are studied. The results show that the temperature difference between the inlet and outlet, total heat storage and total heat release increases with the increase of fin thickness, fin height, and surrounding rock temperature, decreases with the increase of inlet velocities and inlet temperature. The heat exchanger energy efficiency coefficient increases with increasing fin thickness and height, decreases with increasing surrounding rock temperature, inlet temperature and inlet velocities. The temperature difference between the inlet and outlet, total heat storage and total heat release of copper fins are higher than those of other materials. The energy efficiency coefficient of using round fin is higher than that of using square fin, square H-fin and round H-fin. When copper round fins are used, the heat storage of the system is 1457.03 kJ, the heat release is 2831.95 kJ, and the energy efficiency coefficient is 51.45%. [ABSTRACT FROM AUTHOR]

Elliptical fin-and-tube heat exchangers are commonly used in air conditioning, heating, refrigeration industries, and ventilation. This study numerically investigates the effect of vortex generators on the performance of elliptical fin-and-tube heat exchanger under different inclination angles. In this study, air flow that is in the transitional regime is selected as the working fluid. Reynolds numbers at the inlet are varied in a range of 1300 to 2100, and the shear stress transport k-ω turbulence model is selected to solve the non-closure of basic turbulence equations. The ellipticity ratios of the tubes which are used for the analysis are between 0.6 and 1.0, and the inclination angles are varied from 15° to 75°. The effects of different inclination angles of vortex generators on the Colburn factor j, friction factor f, and efficiency index j/f are analyzed. The friction and Colburn factors are observed to increase with increasing vortex generator inclination angles. It is found that the efficiency factors for a 15° vortex generator inclination angle at 0.6, 0.7, 0.8, and 0.9 ellipticity ratios improve compared to the corresponding cases with no vortex generator. However, the vortex generator cannot improve the efficiency factor of the circular tube heat exchanger. The 3D CFD method employed by this study has great potential for use in optimally designing the arrangement of the vortex generators to enhance the performance of heat exchangers. [ABSTRACT FROM AUTHOR]

There are the various types of heat exchangers. The selection of the heat exchanger right type is the first basic assumption for its optimal operation. The heat exchanger calculation itself is another prerequisite for its optimal operation. This article deals with the variables which are usually used to describe the stationary operation of any recuperative heat exchanger with two incoming and two outgoing streams. The knowledge of these variables, including the facts resulting from them, is necessary not only from the point of view of the calculation but also from the point of view of the evaluation of the experimental data of any heat exchanger. The variables values needed for the calculation of heat exchangers, so-called key variables, must always fall within the values range determined on the basis of generally valid knowledge about heat exchangers. The article also deals with the determination of the limit values defining the values range of these key variables.

An experimental analysis has been carried out to investigate the thermal and friction factor characteristics of fluid flow in a tube with double strip helical screw tape (DS-HST) inserts with different values of twist ratio and compared with single strip helical screw tape inserts and plain tube. Water is used as a working fluid at different flow rates with constant heat flux conditions. CFD analysis is also carried out to visualize thermal and fluid flow characteristics of fluid flow in tube with inserts. Experimental results have showed that Nusselt number and friction factor have attained excellent enhancement with double strip helical screw tape inserts in the range of flow rates than single strip helical screw tape inserts at the value of twist ratio 1.5. Correlation is also developed for Nusselt number with a range of Reynolds number, twist ratio and number of strips. Moreover, the performance ratio has attained maximum value at twist ratio of 2.5 with high values of flow rate. It is concluded that DS-HST is able to attain enhancement in the efficiency of heat exchanger, causing a reduction in size for thermal applications. [ABSTRACT FROM AUTHOR]

Fouling of oils on heat exchanger surfaces and pipelines is a common problem in a variety of industrial applications. This is because the oil deposits on the heat transfer surface causes an increase in pressure drop and a decrease in heat exchanger efficiency. In the current work, oil fouling in double pipe heat exchanger was investigated and mitigated using a surface‐active agent for the flow of a dispersion fluid containing different dispersed oil fractions in water. The effect of the dispersed oil fraction (5%vol and 10% vol) and temperature (35°C‐55°C) on the oil fouling rate was studied and discussed under turbulent flow conditions for both hot and cold fluids. Different amounts of alkylbenzene sulfonate as a surfactant were added to reduce the fouling rate under turbulent flow. It was found that the fouling thermal resistance (Rf) increases when the fluid temperature decreases. The higher the dispersed oil fraction, the higher the Rf for all temperatures due to higher oil deposition. Addition of 0.2%vol to 0.5%vol of alkylbenzene sulfonate caused an appreciable reduction in Rf depending on oil fraction and Reynolds number. The mitigation percent was higher for a lower Reynolds number, reaching up to 96%. [ABSTRACT FROM AUTHOR]

The influence of the thermal parameters of a Plain-Fin Compact Heat Exchanger on its performance is examined in this paper. The objective of this work is to analyse the effect of the different flow and geometric parameters on the output performance of a plain fin compact heat exchanger (PFCHE) designed to be used on a small-scale gas turbine and how these parameters can be used for the optimisation of PFCHEs. In this work, we examined the effects of the variation of input parameters of a plain-fin compact heat exchanger (fin length, fin height, fin thickness, mass flow rate of air and turbine exhaust gas) on the output performance of the heat exchanger (Overall heat exchanger efficiency, fin heat transfer efficiency and the outlet temperatures). The analytical expressions for the outlet temperatures and heat exchanger efficiencies were derived and analysed. Then the derived model was designed and simulated using CFD codes. Also, from the derived expressions, the performance model of the heat exchanger was programmed for analysis. From the results, it shows that the effectiveness (e-value), fin length, fin height and mass flow rates of the gases influence performance of a plain-fin compact heat exchanger. A 50% reduction in fin height can cause as much as an 18% increase in the fin efficiency of the heat exchanger. While a 50% increase in the effectiveness value can cause as much as a 40% increase in the outlet temperature. [ABSTRACT FROM AUTHOR]

Energy efficiency projects deployment for Ukraine is one of the challenging task today. Ukrainian industry faces very complex environment for project development as well as its deployment within organization nowadays. UA Policy struggle to keep place on the European market to have possibility not only be a part of global policy but to go forward and to bring benefits for macro and micro economy. Fresh breath by integration energy systems within project management into business model of organization let to move closer to hold under control energy efficiency projects realization and avoid financial risks. Environmental policy and energy policy play crucial role for Ukrainian transformation into European player. Presented proactive plan provides possibilities to deliver the intended economic and environmental benefits of the Ukrainian energy labelling and ecological design directives. These directives are in use or are under development process by increasing the rates of compliance with their energy efficiency requirements. To start from the energy efficiency development process investigation in order to have possibilities to make corrections on the stage of modeling and design can bring benefits and reduce costs for end users. To evaluate the efficiency of heat exchangers, there are over 40 different private integral energy efficiency criteria. Such a number makes the estimation of heat exchangers not always objective and sufficiently definite, which does not allow to algorithmize the task of determining the efficiency of heat exchangers. On the foundation of the system element representation for the heat exchange network, the concepts of energy potential and energy efficiency of energy exchange are proposed. The obtained equations allow us to determine the efficiency of energy exchange not only for an element of the heat exchange network, but also for a complex system as a whole with a minimum of information about the system. [ABSTRACT FROM AUTHOR]

The environment inside laying hen houses has an important effect on hen productivity, health, and well-being. Heat exchangers (HE s) can recover waste heat in ventilation exhaust to reduce supplemental heating needs while maintaining a greater fresh air exchange rate. For laying hen houses, there is limited information on the effect of heat recovery ventilation (HRV). Thus, the objective was to evaluate an air-to-air HE for manure belt drying ventilation in aviary laying hen housing. Temperature (T), relative humidity, ammonia, and manure dry matter (DM) content were characterized during a 4-wk period in October 2018. In weeks 2 and 4, the HRV was shut down and compared to weeks 1 and 3 when the HRV was operational. Average (±SD) ambient T was 10.6°C ± 4.0°C, similar for the 4-wk period. Heat exchanger efficiency was 75.07% ± 9.4% with the average supply temperature increased by 10.0°C ± 3.4°C and an average of 93.94 ± 31 kW heat recovered. Average indoor T (23.1°C ± 0.5°C) was warmer as a function ambient T and daily average T range was lower with HRV (1.8°C ± 0.7°C) compared to without HRV (22.2°C ± 1.2°C; 3.1°C ± 1.1°C). Seven days after manure removal, final average manure DM was 40.6% ± 3.1% (without HRV) and 60.0% ± 3.3% (with HRV). Implementation of HRV positively influenced indoor thermal environment by maintaining less dynamic diurnal fluctuations and greater temporal T uniformity. [ABSTRACT FROM AUTHOR]

• Pure fine silver powder sinter heat exchanger materials were studied. • Bond strength between particles in a sinter was assessed using thermal diffusivity. • A 0.13 μm sinter had surface area 1.4 m2/g and pore volume 5.99 × 10−3 cm3/g. • A 0.13 μm sinter showed bond strength equal to that of a common 0.07 μm material. • The 0.13 μm sinter is suitable for use in ultra-low-temperature cooling. This work investigated sinters made of pure fine silver powders having nominal particle sizes of 0.07, 0.13 and 10.6 μm, using nitrogen gas adsorption, laser flash analysis and field emission-scanning electron microscopy. The goal was to improve the efficiency of heat exchangers used in ultra-low-temperature cooling. This study also examined the bond strength between particles in the sinters, which is associated with the thermal conductivity of the materials, based on thermal diffusivity data. The 0.13 μm sinter had a specific surface area greater than 1.4 m2/g, while the 0.07 μm material, which is most widely used for ultra-low-temperature cooling, had a value of approximately 0.4 m2/g. The latter surface area was less than 25% of previously reported values. The 0.13 μm sinter with a 55% packing fraction exhibited a large total pore volume of 5.99 × 10−3 cm3/g, a high specific surface area of 1.6 m2/g, and the largest room temperature intrinsic thermal diffusivity of 9.12 × 10−5 m2/s in air. Therefore, the 0.13 μm material represents the optimal heat exchange sinter for ultra-low-temperature applications. [ABSTRACT FROM AUTHOR]

Optimizing the performance of solar collectors and photovoltaic thermal systems that are used for heating/cooling of building as well as electricity generation will efficiently help to approach zero-energy buildings. For this purpose, improving the efficiency of heat exchangers as the main part of solar collectors and photovoltaic thermal systems is necessary. In this paper, two passive methods are employed to ameliorate the efficiency of heat exchangers. To do this, the effect of using Al2O3/water nanofluid in a heat exchanger tube with a swirling flow turbulator was studied. A numerical simulation was carried out to obtain thermal–hydraulic performance in the tube with eccentric helical screw-tape turbulators. The influences of different parameters including nanoparticles volume fraction and eccentricity of tube insert on the performance of heat exchanger are investigated. The results reveal that the coefficient of heat transfer enhances approximately 4.5 times by using nanofluid at nanoparticles volume fraction of 4% with helical turbulator compared to the plain tube at nanoparticles volume fraction of 0%. It was also found that the value of Performance Evaluation Criterion ameliorates as the nanoparticle loading increases. The maximum value of Performance Evaluation Criterion reached 2.2 at nanoparticles volume fraction of 4%, Reynolds number of 4000 and eccentricity of 3. The results of this study reveal the potential of the suggested technique to enhance various thermal systems including solar collectors. [ABSTRACT FROM AUTHOR]

Abstract In this study, technical and economical evaluation of a multi effect distillation (MED) system is presented which utilizes the vapor produced from waste heat of exhaust flue gases. In order to recover the waste heat of flue gases, a shell and tube heat exchanger was designed with the Polytetrafluoroethylene (PTFE) material in order to resist corrosion as a result of sulfuric acid formation. Recoverable energy, which is obtained from experimental data, serves as the source of energy required to produce water vapor. Due to high fluctuations in the amount of vapor produced, an auxiliary boiler is employed for its compensation. The vapor which has been produced by the heat exchanger and/or auxiliary boiler, is used as the motive steam in the MED distillation. Economic analysis of MED distillation system driven by low-temperature waste heat is carried out and system payback period based on natural gas saving is obtained. Finally, waste-heat-driven MED distillation system is compared to a conventional MED on the basis of the levelized cost of water (LCOW) at different electrical and natural gas tariffs as well as the real interest rates. Economic evaluation shows that the LCOW is about 1.13–2.9 $/m3. Highlights • Techno-economic evaluation of a waste heat driven MED system is performed. • The PTFE heat exchanger and auxiliary boiler are employed to produce vapor for MED. • Comparison is made between the proposed system and conventional MED based on LCOW. • Effect of electrical and natural gas costs and interest rate on LCOW are investigated. • Economic evaluation shows that the LCOW is about 1.13–2.9 $/m3. [ABSTRACT FROM AUTHOR]

Abstract In this work, we experimentally demonstrate a commercial ceramic membrane heat exchanger (CMHE) with an average pore size of 4 nm for novel heat recovery in post-combustion carbon capture. The CMHE shows superior performance over a conventional stainless steel heat exchanger (SSHE) with the same dimensions in recovering heat from the stripped gas mixture (H 2 O(g)/CO 2) on top of the stripper in a monoethanolamine-based rich-split carbon capture process. Due to the coupled mass and heat transfers of water vapor through the membrane, the CMHE has higher heat flux, heat recovery and overall heat transfer coefficient than the SSHE. Liquid water transfer dominates the mass transfer mechanism in the CMHE. Thermal conduction contributes to more than 80% of the total heat transfer, dominating the heat transfer through the membrane heat exchanger. Our study demonstrates that membrane heat exchangers can be excellent candidates for heat recovery in post-combustion carbon capture. In further research, more types of membranes with higher thermal conductivities (e.g., porous metal membranes with lower porosity and smaller thickness) should be fabricated and tested for further performance enhancement. Graphical abstract fx1 Highlights • We experimentally test a membrane heat exchanger for heat recovery in carbon capture. • Membrane heat exchanger shows superior heat recovery than conventional heat exchanger. • Liquid water transfer dominates mass transfer in the membrane heat exchanger. • Thermal conduction dominates heat transfer in the membrane heat exchanger. • More types of membranes with higher thermal conductivities should be explored. [ABSTRACT FROM AUTHOR]

Complex structures for heat exchangers in high-temperature applications are developed in the research project instaf. The driving force behind these developments is the new design freedom given by the additive manufacturing (AM) of ceramics. With this technology, the complexity of form is no longer an obstacle for profitable solutions. The application of fractals in this context is very promising, since it takes advantage of the new freedom while on the other hand the algorithms for the generation of such forms are relatively easy to handle. This paper presents some proposals for heat exchangers or mixing structures, which are inspired by natural formations. The underlying assumption is: the efficiency of a heat exchanger increases with the surface area of the wall between the fluids. The surfaces here are derived from a series of fractal curves within a given outer shape. The algorithms for the curves use the Lindemayer system (Lsystem), which allows for steering a large variety of curves systematically. [ABSTRACT FROM AUTHOR]

Work on increasing the efficiency of heat exchangers used in car air conditioning systems may lead to a partial change in the construction of refrigeration systems. One of such changes is the use of smaller gas coolers, which directly translates into a reduction in the production costs of the entire system. The article presents the use of computational fluid dynamics methods to simulate the impact of changing the shape of an internal heat exchanger on the cooling efficiency with R744 as the refrigerant. Internal heat exchangers with different geometry of the outer channels were subjected to numerical analysis. The obtained results of calculations show temperature changes in inner and outer channels on the length of the heat exchanger. [ABSTRACT FROM AUTHOR]

The present study investigates the thermal performance and fluid characteristics of counter flow heat exchangers (CFHEs) computationally. Increasing heat transfer rate in heat exchangers depends on various parameters such as channel geometry, the geometry of obstacles in the channel, frequency and amplitude of corrugated plate, and other factors. In this simulation, the influence of parameters contains the effects of the geometry of the obstacles, the corrugated plate between the channels, the elastic plate between the channels, the frequency and wavelength of the corrugated plate, and its effect on increasing the heat exchanger efficiency have been studied in detail. The numerical method is the finite element method, and a complete set of Navier-Stokes equations are solved unilaterally using the Petrof-Galerkin method. It has been concluded that all methods will improve the performance of the CFHEs. Among the obstacles placed in the channels, the rectangular and edge obstacles show better results. In the case of a corrugated mid-plate, with increasing the wave in mid-plate between channels, heat transfer rate (HTR) increases to a certain amount. It was observed that the elasticity of the mid-plate between two channels and the sinusoidal pulse flow would improve HTR in CFHEs. [ABSTRACT FROM AUTHOR]

This paper proposes partially filling a gas tube with metal foam to further enhance the gas heat transfer capability with smaller pressure loss. A wind-tunnel-type gas heat transfer test system was built to investigate the features and effects of this heat transfer enhancement method. The effects of pore density and filling thickness of the metal foam on the gas heat transfer in the tube were studied experimentally and analyzed by determining the performance evaluation criteria (PEC), a comprehensive evaluation index. The results show that for the same porosity and filling rate, a high heat transfer coefficient can be obtained at high pore density; however, the comprehensive evaluation index of metal foam with a lower porosity is higher. Thus, lower porosity metal foam inserted at a higher filling rate, together with a low Reynolds number, leads to more efficient heat transfer. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation of the thermodynamics performance (efficiency) of a closed-loop vertical and horizontal earth-to-air heat exchanger (underground air tunnel) in the heating mode. The experimental system was commissioned in June 2009 and the data have been collected since then. The data, consisting of hourly measurement records for heating periods between 2009 and 2016, were measured at the Solar Energy Institute of the Bornova Campus at Ege University. At the present time, the database contains more than 80,000 records of measurements. First and second law efficiency values of the system and its components have been analyzed. Monthly and yearly average energetic and exergetic efficiencies of the system and its components at various reference states are also determined. [ABSTRACT FROM AUTHOR]

With energy consumption increasing sharply and copper resource decreasing rapidly, the demand for a high-performance and efficient heat exchanger becomes more and more pressing. Therefore, it is very important to develop new technology, new materials, and low-cost and high-performance fin tubes, which is the main component of heat exchanger. In this paper, a new type of aluminum noncontact thermal resistance finned tube (ANCRF) is studied experimentally on the standard wind tunnel test bench. The performance curves of heat transfer and resistance and the experimental correlations were obtained in the experiment range of Reynolds number, which indicates that ANCRF has excellent heat transfer and flow resistance performance. Compared with a louvered fin tube and plate fin tube, the air-side convective heat transfer coefficient of ANCRF was approximately 63.06 and 176.33% higher on average; the friction factor was approximately -71.28 and 51.3% higher on average; and the heat transfer factor was approximately 135.3 and 105.9% higher on average. In addition, a simulation model was established. The positive correlation between the simulated results and the experimental data demonstrated the effectiveness of the model. With this model, the heat transfer process of ANCRF was simulated, with results indicating that the structure sizes of fin thickness, fin height, fin spacing, and fin angle all have great influence on the heat transfer and flow performance of ANCRF, and the rules of influence are different. This research has a guiding significance for the optimization design and application extending for this new type of fin tube. [ABSTRACT FROM AUTHOR]

This study compared the effectiveness of passive and free cooling application methods of Phase change materials (PCMs) when used as energy efficient retrofitting in a residential building. A modern duplex residential building in Melbourne, Australia was considered for the case study. In passive application, PCM was installed in the ceilings of the house. In free cooling application, outdoor air was supplied to the indoor after passing it through a PCM storage unit. The study was carried out using building simulation software EnergyPlus V8.4 and computational fluid dynamics (CFD) software ANSYS V15.1. The developed simulation models of passive and free cooling applications were validated using relevant experimental data. The validated simulation models were then used to investigate the effectiveness of these PCM application methods in the selected building. The results showed that, for the studied house, free cooling application of PCM is more effective than the passive application in reducing the internal zone temperature. Under typical summer climatic conditions of Melbourne, free cooling application resulted in up to 1.8 °C reduction in zone air temperature, compared to only 0.5 °C when PCM was applied as passive heat storage system. The outcome of this study would be helpful in selecting the effective PCM application method for these types of residential buildings in similar climates. [ABSTRACT FROM AUTHOR]

In this article, the thermal performance of a solar air heating system is experimentally investigated. In this system, an evacuated tube solar water heater is connected to a heat exchanger with connecting pipes. The evacuated tubes are used to produce hot water. This hot water flows to the heat exchanger through connecting pipes, the flow of hot water occurs due to thermosyphon phenomenon. Hot air is generated by passing ambient air through the heat exchanger. Three different types of heat exchanger viz. type-I, type-II and type-III have been used. The height of the heat exchangers has been varied from 1050 mm to 1800 mm to evaluate the effect of height variation on the natural circulation flow rate of hot water. The maximum measured temperature difference between the hot air and the ambient air achieved was 10.7°C which was obtained with the heat exchanger type-II at the height of heat exchanger from ground level of 1550 mm. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 232-247, 2017 [ABSTRACT FROM AUTHOR]