Different Types Of Heat Exchangers Research Articles

Review[sbnd]Recent developments on applying acoustic waves for efficiency improvements of different thermofluids systems

This review classified recent works using proper acoustic waves to develop more efficient thermofluids systems for different industrial equipment such as swirl combustor, jet in crossflow, gas flare, different types of heat exchangers, cooling mechanism, aircraft wings, and turbine blades. For the swirl combustor, the range of proper excitation Strouhal number and jet pulsation intensity depends on the type of fuel, geometry of burner, swirl number, and central and annular Reynolds numbers. The combined effects of early jet break up, and centrifugal force induced by proper acoustic waves can lead to higher jet spread rate that can induce higher levels of mixing of the fuel and air in swirl combustor, improving combustion efficiency. For the transverse jet, the range of proper excitation Strouhal number and jet pulsation intensity depends on the type of fuel, geometry, and angle and direction of the burner, and jet and cross flow Reynolds numbers. Proper acoustic excitation can force the transverse jet flow to synchronized shear layer vortices. This phenomenon can cause the new vortices to appear in the upwind shear layer region of the deflected jet; then the spread, penetration, entrainment, and dispersion of the jet significantly increases, improving combustion efficiency. For the aircraft wing, vertical acoustic excitation significantly improves the lift force when the sound frequency is equal to the period of flow fluctuation in the separated boundary layer. For the heat exchanger, the ultrasonic transducer can be installed on the walls of a heat exchanger with direct contact to the fluid, improving the heat transfer coefficient. The physics of fluids behind the efficiency improvements of all mentioned cases were also clarified. Moreover, the acoustically excited impinging jets with higher cooling efficiency applied in different areas are discussed. Proper acoustic forcing can decrease the rate of unstable frequencies of disturbances related to impinging jets over a short distance. This phenomenon can significantly enhance heat transfer and improve cooling efficiency. This review paper provides insight into how acoustic waves could improve the efficiency of thermofluids systems in a variety of applications. Acoustic excitation could have the potential capability to improve the efficiency of new applications such as wind, gas or steam turbines, some types of industrial chemical mixers with parallel plane jets, aircraft wings or those of unmanned aerial vehicles, more efficient combustion chambers, and less polluting gas flares. However, the feasibility of this concept requires further investigation by the community in the future.

Multi-Criteria Study on Ground Source Heat Pump with Different Types of Heat Exchangers

Heat pumps are currently one of the most frequently applied heat sources in residential buildings. Ground source heat pumps are more reliable than air source heat pumps in terms of energy efficiency, especially in colder climates. However, they are more expensive and involve increased material inputs; therefore, multi-criteria analyses taking into account environmental and economic aspects seem necessary for the green design of these systems. The aim of this work was to analyze the environmental and economic impacts of the ground source heat pump providing heating for a family house located in eastern Poland, cooperating with three types of ground heat exchangers (each in two sizing options): helix, vertical and horizontal. The multi-criteria analysis was based on the life cycle assessment methodology using IMPACT 2002+ and life cycle costs methods. The lowest environmental impact was reported for the variants with vertical ground heat exchangers, mainly due to their high efficiency in the operation stage. On the other hand, the lowest economic impact was observed for the horizontal heat exchangers, which are not demanding in terms of material and construction costs. Final recommendations based on multi-criteria analysis propose the vertical probes as a sustainable solution, with a weighted sum indicator in the range 0.085–0.297 on 0–1 scale.

Entropy generation minimization for different types of heat exchangers using nanofluids

ABSTRACT In view of the current global energy situation, increasing the efficiency of heat exchangers can contribute significantly to reducing energy consumption and greenhouse gas emissions. In this study, the effects of nanofluids (SiO2/Water) prepared at different fluid flow rates and different volumetric concentrations (vol.%0.1-0.2-0.3) on three heat exchangers (Shell and Tube, Double Pipe, Plate) with the same capacity were investigated experimentally and statistically. It was concluded that there was an increase of 47% in effectiveness and 87.3% in NTU value with the increase in the volumetric concentrations of nanofluids and fluid flow rate. With the use of nanofluids, it was observed that entropy production decreased by up to 56.08%. The results obtained were analyzed using Response Surface Methodology (RSM) and mathematical models were created and the prediction capabilities of the models were 98% and above. Entropy minimization was performed using statistical methods and it was statistically determined that plate heat exchangers give better results among heat exchangers with the same capacity. It is concluded that the entropy production is minimum when the fluid flow rate is 2 lpm, the volumetric concentration is 0.3% and a plate heat exchanger is used. This study has provided a different and comprehensive perspective on heat exchangers, and it is thought that it will give many ideas to researchers working in this field.

Energy saving when using equipment for the disposal of low-potential waste heat

The article discusses the problem of energy saving in the context of comparing different types of heat exchangers for the utilization of high-potential waste heat. The advantages and disadvantages of various regenerative ventilation schemes are analyzed and the most efficient heat exchangers are proposed for use in various fields. These include various types of regenerative heat exchangers. The factors influencing reliability and creation of optimal operating modes with high energy savings are considered. Recommendations for the use of enthalpy heat exchangers with the required technical characteristics are given. Various types of nozzles are shown to ensure better efficiency. The advantages and disadvantages of regenerative heat exchangers with an intermediate carrier and techniques for reducing the cost of manufacturing such structures are considered. The areas of application of small-sized plate heat exchangers are given. The principle of operation of heat exchangers on heat pipes (HHP) and their technical characteristics are considered. A compactness criterion has been introduced, which allows comparing different types of heat exchangers. The instantaneous boiling apparatus for the utilization of low-potential internal (by-product) energy resources (IER) and possible applications are considered in detail. In all cases of using the considered schemes, the prospects for their development in industry are noted.

Maximization of the Heat Transfer Irreversibility

Abstract The function of a heat exchanger is to transfer heat. In this paper, a second law-based hypothesis is advanced that in heat exchangers, the entropy generated as a result of heat transfer alone, termed productive entropy, is the desired irreversibility and should be maximized while the entropy generated (irreversibilities) by other factors like friction and mixing that do not contribute to this function should be minimized or eliminated to reduce the needed heat transfer area. The hypothesis is proven mathematically for heat transfer between two fluids in a single heat exchanger and also between one hot and two cold fluids in a network of up to four heat exchangers. There currently are two approaches for minimizing the total area (minimum initial cost) of a heat exchanger network (HEN). One uses some empirically based best practices that are generally rooted in the second law, and the other uses optimization algorithms. This paper provides a third approach for HEN optimization, outlining a systematic approach to minimize the area, based on the maximization of productive entropy. The approach identifies the global minimum area for networks with any number of hot and cold streams. It constitutes another method for HEN optimization and an improvement over the existing methods that provide approximate solutions. The methodology is applied to two test cases, and it is shown that this approach improves on the results obtained using the traditional approaches. The approach can be applied to networks using any type of heat exchanger or a combination of different types of heat exchangers.

A comprehensive review of heat transfer enhancement of heat exchanger, heat pipe and electronic components using graphene

The industrial growth of any country depends on energy source availability and utilization of energy for various applications. The heat exchanger is a heat transfer device which is most widely used in various applications for effective heat transfer between cold and hot fluids. Any improvement in heat transfer results in enhancement in overall performance of the device. Hence various techniques are used to improve the heat transfer. The solid particles which have higher thermal conductivity and can be used to improve the heat transfer between hot and cold fluids. The thermal conductivity of graphene-based nanoparticle is high, and it has low erosion, corrosion, higher stability, etc. Hence graphene-based nanoparticle is chosen in various heat transfer applications. The use of graphene-based nanoparticles increases the heat transfer and hence it can reduce the size of the heat transfer equipment. This paper critically reviews various applications of graphene in different types of heat exchangers, electronic devices challenges and opportunities, by highlighting the advantages of using graphene.

Design and Optimization of Organic Rankine Cycle Based on Heat Transfer Enhancement and Novel Heat Exchanger: A Review

The effective exploitation of renewable energy and the recovery of waste heat are two crucial strategies in achieving carbon neutrality. As an efficient and reliable heat–to–power conversion technology, the organic Rankine cycle (ORC) has been recognized and accepted by academia and industry for use in solar energy, geothermal energy, biomass energy, and waste heat applications. However, there remain unsolved technical challenges related to the design and operation of the components and system. As the exergy destruction and investment cost of heat exchangers exert significant influence on the performance of ORC, investigations on the performance improvement of heat exchangers are of great significance. The aim of this paper was to provide a review on the performance improvement of ORC in relation to heat transfer enhancement, heat exchanger design optimization, and cycle construction based on a novel heat exchanger. The performance of ORC using different types of heat exchangers was discussed and the importance of revealing the influence of heat exchanger structural parameters on ORC performance was assessed. The heat transfer enhancement, novel heat exchanger investigation, and the ORC configuration development based on a novel heat exchanger were emphasized. Finally, developments and current challenges were summarized and future research trends were also identified.

COMPARING THE PERFORMANCE OF USING NANOFLUIDS IN TWO DIFFERENT TYPES OF HEAT EXCHANGERS WITH THE SAME HEAT TRANSFER AREA

Using multi-wall carbon nanotubes (MWCNTs) based on distilled water with varied volume concentrations, experimental research was conducted. The performance of two distinct heat exchangers with the same heat transfer area was assessed. A tubular heat exchanger (THE) and a shell-and-tube heat exchanger (STHE) with a heat transfer area of 20,000 mm<sup>2</sup> were employed. A tubular heat exchanger (HT31) and a shell-and-tube heat exchanger (HT33) are available from Armfield for use with the heat exchange service unit (HT30X). Three volume concentrations of nanomaterials are used to create nanofluids (0.5%, 1%, 2%). While the rate of flow was the same in the heat exchangers, the Reynolds number of the flow inside the tube ranged from 1600 to 7800 for THE and from 2500 to 12,500 for STHE due to different inside diameters. The measured variables determine the coefficient of heat transfer, friction factor, Nusselt number, and effectiveness. The heat transfer coefficient in both heat exchangers was boosted with increasing MWCNT content, according to the experimental data. Because of the nanoparticle concentration, the heat transfer coefficient of STHE is 7-43% greater than that of THE. With the increase of nanofluid concentration, the Nusselt numbers were enhanced for the two heat exchangers. The increase in the Nu number for THE is higher than in its value for STHE within a range of 28.5-40%. Correlations between the Reynolds number and MWCNT volume concentration are proposed for each heat exchanger to compute the Nusselt number and friction factor. The results of the current study have been compared with previous studies and acceptable agreement can be found.

Ultrasonic Vibration Technology to Improve the Thermal Performance of CPU Water-Cooling Systems: Experimental Investigation

The rapid growth of the electronics industry and the increase in processor power levels requires new techniques to improve the heat transfer rate in their cooling systems. In this study, ultrasonic vibration technology was introduced as an active method to enhance the thermal performance of water-cooling systems. The effects of ultrasonic vibrations at power levels of 30, 60, and 120 watts for different cooling airflow rates were investigated experimentally. The results were validated with available empirical correlations to ensure the accuracy of the measurement systems. The findings indicated that the ultrasonic vibrations enhanced the heat transfer in the liquid-cooling heat exchangers. In addition, the thermal performance of the ultrasonic vibrations was improved by reducing the airflow rate and increasing the ultrasonic power. In addition to the feature of heat transfer improvement, ultrasonic waves are widely used for the cleaning of different types of heat exchangers. Regarding the anti-fouling and anti-accumulation effects of the ultrasonic vibrations, the introduced technology could provide a practical way for developing high-performance nanofluids-based computer cooling systems.

Multiresponse optimization of exhaust thermoelectric generator using Taguchi‐based gray relation analysis

AbstractThe best operating condition of the exhaust thermoelectric generator (ETEG) provides more power output and low‐pressure drop (low‐PD). So it is required to optimize the operating condition of the ETEG. In the present work, Taguchi's L18(61 33) orthogonal array was chosen to find the optimal parameters. Analysis of variance was used to determine the percent contribution of the control factors such as engine loads (ELs), different types of heat exchangers (HEs) with and without inserts, water flow rate (WFR), and external load resistance (ELR) on the thermoelectric power output and PD in the HE. The confirmation test was carried out at optimum levels for the regression equations and Taguchi method. Gray relational analysis was performed to find the optimum value of the power output and PD. It is observed that the optimal operating condition is EL6 HE1 WFR3 ELR2 (EL6 = 10 kg, HE1 = G‐type test section, WFR3 = 0.08 kg/s, and ELR2 = 40 Ω).

Effect of Waste Heat Utilization on the Efficiency of Marine Main Boilers

As a result of technological advancements in the 21st century, steam-driven ships, with an efficiency of between 36 and 38%, have been replaced by diesel-driven ships, with an efficiency of up to 55%. Accordingly, the manufacturers of the main boilers and steam turbines in ships have fought for their products to remain on the market by modernizing their construction in order to increase their competitiveness in relation to diesel drives. Based on a review of data in the literature, this article presents an analysis of the increased efficiency of ship boilers with the use of waste heat from boiler exhaust gas. This paper considers the utility of using this heat to heat up the water that supplies the boilers as well as the use of the heated air in the combustion process. The analysis takes into account the different types of heat exchangers used for these purposes and the different efficiencies of boilers made by the leading boiler manufacturers. The formulae and calculation methodologies used are applied in the following analysis of the impact of using waste heat to increase boiler efficiency.

Thermal and Economic Analysis of Heat Exchangers as Part of a Geothermal District Heating Scheme in the Cheshire Basin, UK

Heat exchangers are vital to any geothermal system looking to use direct heat supplied via a district heat network. Attention on geothermal schemes in the UK has been growing, with minimal attention on the performance of heat exchangers. In this study, different types of heat exchangers are analysed for the Cheshire Basin as a case study, specifically the Crewe area, to establish their effectiveness and optimal heat transfer area. The results indicate that counter-current flow heat exchangers have a higher effectiveness than co-current heat exchangers. Optimisation of the heat exchange area can produce total savings of £43.06 million and £71.5 million, over a 25-year lifetime, in comparison with a fossil-fuelled district heat network using geothermal fluid input temperatures of 67 °C and 86 °C, respectively.

Numerical and Experimental Performance Analysis for Different Types of Heat Exchangers

Heat exchangers are devices whose primary responsibility is to transfer heat, typically from one fluid to another. In such applications, the heat exchangers can be parallel flow, crossflow, or counter flow. An essential part of any heat exchanger analysis is the determination of the effectiveness of the heat exchanger. In the present work, three different types of heat exchangers are investigated. Numerical and experimental performance analyses are applied. The main objective of the present work is to compare the effectiveness of each heat exchanger at different conditions. Six experimental investigations for Plate, shell & tube, and fluidized bed heat exchangers are executed. All experimental tests are reached to steady-state conditions. The results show that the counter flow plate heat exchanger has an effectiveness of 90% compared with the parallel flow of 60% effectiveness for working experimental conditions. Also, the fouling effect in decreasing heat transfer is cleared. In the present work, fouling decreases effectiveness from about 18% to about 4%. In addition, the effectiveness of the fluidized bed heat exchanger depends on the material used for the bed. Finally, the overall heat transfer coefficient is obtained and compared for all experimental tests, and it is directly proportional to the effectiveness of the heat exchanger. The FEHT program is used to get the temperature distribution in all types of present work heat exchangers.

Retrofit Synthesis of Industrial Heat Exchanger Networks with Different Types of Heat Exchangers

Heat Exchanger Network (HEN) synthesis is a powerful tool for the development of more efficient processes with high utilization of mass and energy resources. The implementation of compact heat exchangers with enhanced heat transfer into the industrial flowsheets can provide more efficient and economically feasible solutions. Plate Heat Exchanger (PHE) is one of established types of enhanced HEs. To estimate possible benefits of that kind of heat transfer enhancement, a mathematical model of PHE, which accounts for different plate types and corresponding corrugations geometry, is used. The integration of this model with the P-graph-based HEN synthesis approach allowed to create the method, which considers different types of heat exchangers. This approach enables to integrate not only conventional shell-and-tube heat exchangers, but also PHEs, which overall heat transfer coefficient is in average 2-3 times higher, during the optimization process of a new or existing HEN. The capabilities of the proposed method are presented via a case study for oil preheat train, where an existing network is retrofitted; first with shell-and-tube heat exchangers only, then with the consideration of both shell-and-tube and plate heat exchangers.

Optimization procedure of a new type counter–flow heat exchanger

Plenty of studies exist in books and archival journals dealing with different types of heat exchangers. In the paper an analytical approach to evaluate the overall heat transfer coefficient of a new type heat exchanger is presented. Derived equations are applied to multi-objective optimization of a very large economizer of a recovery boiler, when the exchanger mass and size should be small but simultaneously heat transfer rate high.

Numerical Simulation of Cross Flow in In-Line Square Tube Array to Estimate the Convective Heat Transfer Coefficient

Flow cross tube banks is an important application of different types of heat exchangers, such as compact heat exchangers, and baffled shell and tube heat exchangers. Baffles are used in shell and tube heat exchangers to allow the flow to become cross the tubes. This ensures the mix and increases the convective heat transfer coefficient. Design models of baffled shell and tube heat exchanger, which ensures the cross flow, relay on convective heat transfer coefficient. Which obtained from empirical correlation available in the literature. This work is a numerical approach to simulate flow cross a single tube and an in-line square tube array to estimate the convective heat transfer coefficient. This approach is an alternative to the experimental approach. In order to calculate the heat transfer coefficient and it’s relation to the Reynolds number for a single tube and for an in-line square tube array, a Computation Fluid Dynamic [CFD] software (ANSYS FLUENT), Which utilizes Reynolds Average Navier Stokes [RANS] method to solve the momentum equation in 3-D, was utilized to conduct the numerical simulations. Each model was simulated at 4 different entry velocities of (10, 15, 20, 25 m/s) for a Reynold’s number ranging between 6000-35000. The turbtulence model used was K-ω sst. The results obtained via the CFD simulations were validated with an empirical correlation for the two models. These results have deviations from the empirical results ranging between 5 to 22%. The numerical simulation and the empirical correlation results have identical trends for the case of a single tube and for the case of in-line square tube array. For further improvement in results validations, further studies should be made.

Experimental and theoretical analysis of heat transfer in a solar collector storage

The current research includes a practical study of the thermal performance of solar collector integral storage system (ISCS) in which different types of heat exchangers are immersed in its enclosure for comparison. The first type is a straight tube heat exchanger (ST) and the other is a heat exchanger in the form of a coiled tube (CT). The effect of single and double glass layers and fluid flow rates inside the heat exchanger on the natural convection heat transfer of ISCS system is experimentally evaluated by determining the temperature difference of inlet and outlet water through the heat exchanger immersed into the ISCS enclosure, the temperature distribution inside the enclosure, the ISCS efficiency, and the amount of thermal storage during evening times. Three sets of experiments are performed for a different water flow rates (1.0, 1.5, 2.0, and 2.5 Lpm) inside the heat exchanger that is immersed in the thermally insulated enclosure and different glassing layers. The first set represents the presence of a heat exchanger in the form of a straight tube with a single glass was layer on the top face of the enclosure that is called (STSG). The second set uses a coiled tube heat exchanger with a single glass on the upper side of the enclosure and it’s named as (CTSG). The last set of experiments is represented by a heat exchanger in the form of a coiled tube with a double glass on the upper face of the enclosure and it’s abbreviated as (CTDG). At water flow rate of 1 Lpm, the CTDG exhibited higher temperature difference (28 °C and 19.9 °C than (19.4 and 11.4 °C) for CTSG and (12 and 7.3°C) for STSG during day and night times, respectively. The results reveal that the thermal efficiency (84.5 - 77.8 %) of the (CTDG) case at water flow rate of 2.5 Lpm was higher than the efficiency (68.8 - 56.6%) of (CTSG) case and that (41.7 - 39.7%) of STSG) case during day and night times, respectively. It was also observed that the internal energy exceeds the amount of solar radiation during the day and provides a thermal storage at night due to the complete isolation of the collector. The temperature measurements near the tube allow the calculation of the Rayleigh number during the heat transfer process, and empirical relationships haves been deduced for each set of experiments between the Nusselt number and the Rayleigh number.

An Approximate Transfer Function Model for a Double-Pipe Counter-Flow Heat Exchanger

The transfer functions G(s) for different types of heat exchangers obtained from their partial differential equations usually contain some irrational components which reflect quite well their spatio-temporal dynamic properties. However, such a relatively complex mathematical representation is often not suitable for various practical applications, and some kind of approximation of the original model would be more preferable. In this paper we discuss approximate rational transfer functions G^(s) for a typical thick-walled double-pipe heat exchanger operating in the counter-flow mode. Using the semi-analytical method of lines, we transform the original partial differential equations into a set of ordinary differential equations representing N spatial sections of the exchanger, where each nth section can be described by a simple rational transfer function matrix Gn(s), n=1,2,…,N. Their proper interconnection results in the overall approximation model expressed by a rational transfer function matrix G^(s) of high order. As compared to the previously analyzed approximation model for the double-pipe parallel-flow heat exchanger which took the form of a simple, cascade interconnection of the sections, here we obtain a different connection structure which requires the use of the so-called linear fractional transformation with the Redheffer star product. Based on the resulting rational transfer function matrix G^(s), the frequency and the steady-state responses of the approximate model are compared here with those obtained from the original irrational transfer function model G(s). The presented results show: (a) the advantage of the counter-flow regime over the parallel-flow one; (b) better approximation quality for the transfer function channels with dominating heat conduction effects, as compared to the channels characterized by the transport delay associated with the heat convection.

Design and Simulation of Counter Flow Heat Exchanger with Fins and Internal Ribs

A Heat Exchanger is a device to transfer heat from fluid at higher temperature to fluid at lower temperature with highest efficiency. Designed for various applications such as preheating the water before sending it into boiler for generation of steam. This work is carried out with the primary objective of increasing the thermal efficiency of the procedure heat transfer process. There are different types of heat exchangers from which shell and tube heat exchanger is considered for this present work. High temperature water passes through the copper tubes and low temperature water flows outside the copper tubes. To enhance the rate of heat, transfer the modified design is implemented. The design consists of fins outside the copper tubes to increase the surface area in contact with outside fluid. Also, ribs are provided inside the copper tubes for increasing the turbulence along with more area of contact. This paper mainly deals with design, modelling and CFD analysis of the heat exchanger. Overall heat transfer coefficient of the fins and internal ribs of heat exchanger is based on the results of effectiveness-NTU approach and LMTD approach. Modelling of various components are presented with the help of standard modelling software, solid works. Simulation of the process is done using ANSYS. The simulated results obtained in the software are compared with the published experimental results which are very close to our modified design heat exchanger and it is found that the results are very close to experimental results.

Heat Transfer Enhancement of Single-Phase Internal Flows using Shape Optimization and Additively Manufactured Flow Structures

• We optimize the shape of internal fins using generative design. • The optimized fins are additively manufactured from alsi10 mg. • Rigorous measurements and simulations characterize heat transfer performance. • The optimized fins have 65–77% lower thermal resistance than conventional designs. This paper reports heat transfer enhancement of forced internal single-phase flow enabled by additively manufactured internally finned channels. We consider internal liquid coolant flow through a tube with constant heat flux applied to the exterior surface. A genetic algorithm was developed and used to optimize the fin geometry in order to minimize total thermal resistance for laminar flow or convection thermal resistance for turbulent flow. The genetic algorithm sampled more than 500 fin geometries, evaluated thermal resistance, and selected the optimum fin geometry. We selected three designs for experimental testing: a complex fin structure suggested by the genetic algorithm; a straight fin design; and a smooth circular channel as a reference. The devices were made from aluminum silica (AlSi10Mg) using direct metal laser sintering additive manufacturing. The devices were tested using a water ethylene glycol mixture (80:20) over the hydraulic diameter based Reynolds number range of 400 – 18,000, covering both laminar and turbulent flow regimes. Finite element simulations of heat transfer and pressure drop helped to understand and interpret the measurements. Compared to the smooth pipe reference design, the total thermal resistance of the genetically optimized fin design was 77% lower for laminar flow at Re h = 2,000 and 65% lower for turbulent flow at Re h = 10,000. Compared to the straight fin design that is commonly used for enhancing convection heat transfer in internal flows, the total thermal resistance of the genetically optimized fin design was 55% lower for laminar flow at Re h = 2,000 and 29% lower for turbulent flow at Re h = 10,000. We explore the potential design space for different types of heat exchangers by investigating how total heat transfer varies with exterior heat transfer coefficient and channel wall thermal conductivity. This research shows how shape optimization and additive manufacturing can result in devices with improved internal convection heat transfer.