Thermal Performance Of Heat Exchanger Research Articles

Second law of thermodynamics, heat transfer, and pumping power analyses of water and ionic liquid mixture based MXene nanofluids in a shell and helical coil heat exchanger

Heat exchangers are extensively employed across diverse sectors for efficient thermal (heat)transfer between two fluids, specifically from a hot fluid to a cold fluid. Nanofluids are promising heat transfer fluids that exhibit exceptional thermal performance in heat exchangers. The present study examines the thermodynamic second law efficiency analysis of a shell and helical coil heat exchanger utilizing MXene/80:20% water+[MMIM][DMP] (mass percentage) based ionanofluids. An analytical investigation was conducted on the heat transfer coefficient, entropy generation rate, and exergy efficiency of a shell and helical coil heat exchanger, considering particle weight loadings from 0.2% to 1.0%, Reynolds numbers from 500 to 4300, and flow rates from 0.5 to 3.5 L/min. In the base fluid, at 1.0 wt.% and at a Reynolds number of 3598, the increase in heat transfer, Nusselt number, friction factor, pressure drop, effectiveness, and frictional entropy generation are 45.59%, 28.27%, 15.19%, 12.56%, 17.20%, and 16.21%, respectively. Concurrently, thermal entropy generation, and total exergy destruction were reduced by 46.23% and 20.08%, respectively. The second law (exergy) efficiency and thermal performance factor are improved by 34.04% and 1.384-times, respectively, at 1.0 wt.% and at a Reynolds number of 3598, compared to the base fluid. The data from the current study is corroborated by existing literature. New correlations were developed from the computed data points to estimate the Nusselt number and friction factor.

Thermal Performance of a Laminar Flow Double Pipe Heat Exchanger with Spiral Airfoil Inserts

Objective: This study evaluates the thermal performance of a double-pipe heat exchanger using a spiral airfoil insert in the inner pipe. Methods: The enhancement technique is classified as a passive method, as it does not require the direct application of external power to improve the heat transfer coefficient. Spiral pitch ratios of P/D=7, 5, and 3 were used, with the Reynolds number (Re) varying within the laminar flow regime (Re ≤ 2,100). Cold water flows inside the inner pipe, while hot water flows counter to it in the annulus. Results: The experimental results show that the Nusselt number increased by 159%, 161%, and 171%, respectively, compared to a smooth pipe alone, for flow rates of 2L/min, 2.5L/min, and 3L/min. Additionally, the highest friction factor reached 142%. Conclusion: The results indicate that the best performance evaluation criterion (PEC) was achieved within the flow range of 2L/min to 3L/min, with a pitch insertion of 3, yielding a PEC of 158% to 152%, respectively.

Comparative Study of Heat Transfer and Flow Friction in Plate Heat Exchangers with CarboxyMethyl Cellulose and Sodium Alginate

Abstract: Study of Plate heat exchanger (PHE) with power law fluid is a very interesting topic now a days as there is improvement of thermal performance of heat exchanger. Power law fluids show complex flow behavior due to its rheological properties. The parameters which differ these power law fluids from Newtonian fluids are rheological properties like flow behavior index and power law index. Hence flow behavior index and power law index are the two parameters which affect the heat transfer rate. Now to enhance rate of heat transfer we should know how Nusselt number changes with change in flow behavior index and power law index. Hence the aim of present study was to observe how Nusselt number and friction factor changes with change in flow behavior index and power law index. For this purpose thermal performance of PHE have been studied with CorboxyMethyl Cellulose (CMC) and sodium alginate as a cold fluids. Comparison of Nusselt number and friction factor of CMC and sodium alginate have been done. It was observed that Nusselt number for CMC solution was more compared to sodium alginate solution with less friction factor than sodium alginate.

Enhancing thermal performance of heat exchanger by using different 4-lobed swirl tube arrangements

This study numerically and experimentally investigated the thermal performance of a 4-lobed swirl tube. A double-pipe heat exchanger was built using 3D-printed steel tubes with PD ratios ranging from 4, 6 to 8. In addition, a 3D-printed circular pipe was also manufactured to investigate the influence of the 3D-printing method. In the experimental results, the PD4 decaying swirl tube had the highest performance for all PD ratios. The effects of different pitch-to-diameter (PD) ratios and tube arrangements on the swirl pipe were also investigated during simulations. The results reveal that the tube with a smaller PD ratio and crossover arrangement has a larger thermal enhancement and pressure drop. However, in comparison, the decaying arrangement has a relatively higher overall performance since it has a lower pressure drop. The PD6 decaying tube arrangement is the highest, especially at higher Reynolds numbers. Moreover, by showing the streamline within the swirl tube, small-scale vortices are found within the swirl tube, especially in the crossover arrangement. These vortices are formed due to the swirl motion and can enhance mixing and the heat transfer rate. Based on these simulation results, a regular-spaced swirl tube arrangement is proposed and its thermal performance is evaluated. In the experimental results, the PD4 decaying swirl tube gave the highest overall performance from 1.12 to 1.09 across all configurations. In the numerical results, the regularly-spaced swirl tube can further improve the overall performance with moderate pressure drop. Type 2 PD4 has the highest performance value at 1.06.

Enhancing plate-fin heat exchanger hydraulic thermal performance through air-side fin optimization based on pseudo-3D topology optimization

With the expansion of the New Energy Vehicles (NEVs) market, the demand for efficient thermal management systems is increasingly pressing. Topology optimization (TO) methodology is an important way to improve the performance of heat exchangers (HE) in many use scenarios. This study focuses on enhancing the design of air-side fins within plate-fin HE, which are vital components in NEVs thermal management systems. By employing the TO methodology, our research aims to enhance the hydraulic thermal performance of these HE. A pseudo-three-dimensional (3D) flow heat transfer model is used to improve the hydraulic thermal performance of HE by variable density method. An optimization function considering thermal resistance and dissipated power is proposed in this study. The investigation rigorously assesses the effects of different controlling parameters on the results of TO. Following the optimization, a 3D model of the optimized fin configuration is elaborated to analyze the localized fluid dynamics and thermal characteristics. Furthermore, the study evaluates the hydraulic thermal performance of the TO fins under diverse inlet velocities, revealing significant alterations in vortex patterns with velocity increments, which substantially impact heat transfer in the cooling channel. Under varying inlet velocities, the TO fin design exhibits the optimal hydraulic thermal characteristics, demonstrating an enhancement of 9.53% to 22.82% in the comprehensive performance factor (JF) compared to the conventional serrated fin. This research contributes innovative strategies for radiator optimization in thermal management systems of NEVs, fostering advancements in heat exchange efficiency and radiator lightweight.

Thermal performance of tubular heat exchangers with the discontinuous swirl-inducing conical baffle with opposite-oriented flow deflectors

An experiment was conducted to analyze a tubular heat exchanger's turbulent heat transfer characteristics. The heat ex-changer was equipped with a newly designed perforated (rectangular) conical baffle plate consisting of two rectangular opposite-oriented flow deflectors with adjustable tilt angles. The baffle plate was installed at the entrance of the heat ex-changer, resulting in a counter-swirling flow pattern downstream. Three baffle plates were installed along the flow direction with different pitch ratios (spacing between baffle plates divided by the diameter of the heat exchanger). The experiment examined the effects of pitch ratio (ranging from 0.6 to 1.2), deflector tilt angle (ranging from 30° to 50°) and Reynolds numbers (ranging from 16 500 to 30 000) on the heat transfer performance. The results showed that the pitch ratio and tilt angle significantly affected the performance of the heat exchanger. In particular, a configuration with a tilt angle of 30° and a pitch ratio of 1 resulted in an average improvement of 26.9% in the heat exchanger's performance compared to a heat exchanger without a conical baffle plate under similar operating conditions.

Thermal performance of a chaotic heat exchanger: an experimental study

Improving the efficiency of heat exchangers requires innovative approaches that reconcile performance and sustainability. This study examines the potential of a curved geometry employing chaotic advection as a passive technique for improving internal heat transfer. The Chaotic Heat Exchanger (CHE) studied was constructed using 18 bends at 90 degree angles, and by simply turning each bend at a 90-degree angle to the previous one. The aim is to investigate the chaotic heat exchanger by focusing on heat transfer efficiency. A comparative analysis is carried out between the chaotic heat exchanger and a conventional Helical Heat Exchanger (HHE), using an experimental approach with water as the internal hot fluid. The Reynolds number examined ranges from 250 to 3500. It is found that the CHE outperforms the HHE both in terms of heating capacity and of inner Nusselt number, particularly in the intermediate Reynolds number range.

Investigation of Thermal Performance of Heat Exchangers of Inclined-Elliptic-Tube Bundle

Passive performance improvement of heat exchangers is cost-effective and crucial for energy efficiency as well as sustainability of thermal systems. In this paper, an investigation is presented on a compact configuration of heat exchanger composed of a bundle of inclined elliptical tubes. The effect of geometrical parameters on the thermal performance of the heat exchanger is investigated for two tube arrangements i.e. inline and staggered configurations. These parameters include longitudinal (SL/a = 3 to 6) and transversal (ST/a = 2.5 to 5.5) pitch ratios. A CFD commercial code is used for simulation of heat transfer and fluid flow. Computations are performed for the Reynolds number range Re = 300-1500. The outcomes indicate higher performance of the staggered arrangement when compared with the inline inclined tubes. The best thermal performance is observed for a staggered configuration with SL/a = 6, ST/a = 5.5 at Re = 1500. Furthermore, correlations are provided for Nusselt number for heat exchangers of inclined elliptic tubes.

CFD approach to analyze entropy generation, heat transfer of perforated conical ring turbulators embedded in heat exchanger with biological ternary hybrid nanofluid

Perforated conical rings greatly enhance heat transfer by causing flow disruption and increasing fluid mixing. With minimal impact on friction loss, it improves heat transfer by breaking the thermal boundary layer. In this work, entropy generation, overall performance of cylindrical pipe heat exchanger equipped with perforated conical rings are numerically calculated. Shape of the holes is oval and the number of hole are 4. Ternary hybrid nanofluid is the working fluid (coolant). The combination of graphene, Cu and Al2O3 nanomaterials are considered with water as a base fluid. A particular range of Reynolds number is taken into account (5000 − 9000). 50% increase in Nusselt number is noted for using higher volume fraction (0.5%) of ternary hybrid nanofluid. Thermal performance of heat exchanger is increased more than 50%. Entropy generation is higher by using the perforated conical rings. Thermal- hydraulic performance evaluation criteria (THPEC), i.e. ration between Nusselt number and friction factor decreases with increasing Reynolds number which is a promising result. The differences in THPEC of cylindrical tube with and without perforated conical ring (PCR) are highlighted.

Correlation study of thermal charging, discharging, and efficiency of graphene oxide-reinforced paraffin wax for thermal energy storage system

Nanocomposites, produced through mechanical blending, serve to enhance thermal performance of heat exchangers, solar collectors, and photovoltaic-thermal systems. This work employs an experimental methodology to assess the thermal charging (TC) and thermal discharging (TDC) of a composite generated by mixing graphene oxide (GO) and paraffin wax. TC and TDC of the GO-reinforced paraffin wax-based phase change material (PCM) have been examined across different flow rates (0.375, 0.75, and 1.5 L/min) and concentrations of GO (ranging from 0.25 to 1.00 vol%). The results exhibit a direct correlation between TC, TDC and efficiency, and reaction parameters (flow rate and volume concentration of GO). The experimental and predicted values of TCs, TDCs, and efficiencies fell ±15% (for TC and TDC), and ±9% for thermal efficiency, demonstrating a satisfactory level of agreement. This holds a practical application and valuable predictive tool for estimating TC, TDC, and thermal efficiency on known flow rates and concentrations of GO in wax-based PCMs.

Thermal performance of polymer gyroid heat exchangers combined with phase change materials as a latent heat thermal energy storage system: An experimental investigation

Latent heat thermal energy storage (LHTES) systems utilizing phase-change materials (PCMs) in conjunction with heat exchangers (HXs) have been widely investigated for efficient thermal energy utilization. This study experimentally evaluated the heat transfer performance and pressure loss of a PCM-based gyroid HX fabricated using a polymer 3D printer. Initially, the study compared the phase change time, heat storage and release characteristics, and pressure drop of the gyroid HX with those of a conventional shell-and-tube HX (S&T HX). The results demonstrate that the gyroid HX achieved up to 20 % shorter thermal charge and discharge times than the S&T HX, which is attributed to a higher heat transfer rate. Additionally, the measured pressure drop of the gyroid HX was up to 44 % lower than that of the S&T HX. Consequently, considering both the heat transfer rate and pressure drop, the gyroid HX showed an average improvement of 57 % and 31 % in the overall enhancement factor during charging and discharging, respectively, compared to the S&T HX. Further, metal gyroid HXs fabricated from steel and aluminum using metal 3D printing were experimentally compared with the polymer gyroid HX. Despite the polymer thermal conductivity being only 1/90 and 1/790 that of steel and aluminum, respectively, the heat transfer rate per unit mass of the polymer gyroid HX was 1.7 times that of the steel gyroid HX and approximately half that of the aluminum gyroid HX. This finding suggests that the polymer gyroid HX is suitable for LHTES applications where lightweight characteristics are crucial.

Thermal Performance of Earth Air Heat Exchanger for Geothermal Energy Application in Hot Climate using CFD Simulation

The Ground Air Heat Exchanger (GAHE) is a sustainable, environment friendly, and efficient device that can be used for both heating and cooling applications. Careful design of GAHE enables efficient exploit of the earth interior energy. The design of a GAHE relies on the constant temperature of the earth interior which allows consistent and reliable source of geothermal energy. By harnessing this renewable energy, a sustainable solution for heating and cooling needs is attained while minimizing the impact on environment. In this study, the performance of GAHE was examined using ANSYS Fluent 19 R1 and SOLID WORK 16.0 software. The efficiency and Coefficient of Performance (COP) of the ETHE have been investigated. The effect of air flow rate and operation conditions on the outlet air temperature have been studied. GAHE is made of Polyvinyl Chloride (PVC) pipe of 0.1 m diameter, 0.005 m thickness and 18 m horizontal length. Computer simulations were carried out for five different air velocities (1, 2, 3, 4, and 5 m/s) at various operation conditions. Results show that the 18 m pipe length is adequate to attain useful air outlet temperature giving COP values between 0.5 and 1.3. The length of the horizontal part of GAHE can be further increased for air velocities between 3 and 5 m/s. Comparison between the results obtained by the CFD model and experimental work demonstrated that the CFD model is capable of producing results with acceptable accuracy. This suggests that the CFD software can accurately model the performance of the GAHE under different operation conditions. Increasing the length of the horizontal part of the GAHE can improve its COP when higher air velocities are used.

Maximizing Thermal Performance of Heat Pipe Heat Exchangers for Industrial Applications Using Silver Nanofluids

Maximizing Thermal Performance of Heat Pipe Heat Exchangers for Industrial Applications Using Silver Nanofluids

An Experimental Investigation of the Effects of Using Hexagonal BN–Water Nanofluids on the Thermal Performance and Pressure Drop of a Concentric Tube Heat Exchanger

The thermal conductivity of recently produced hexagonal boron nitride (hBN)-containing nanofluids is comparatively higher than their viscosity, indicating that these materials belong to a relatively novel class. In this study, hBN–water nanofluids in stable and dispersed concentrations were used in parallel and counterflow experiments at volumes of 0.01%, 0.1%, and 1%, as well as at various flow rates and Reynolds numbers. When employing hBN–water nanofluid in a counter-flow heat exchanger instead of distilled water, the results showed a 16.7% increase in the overall heat transfer coefficient. The findings also showed that, in comparison to a counter-flow heat exchanger, employing hBN nanofluid as the cold fluid in a parallel-flow heat exchanger produced superior results in terms of an increase in heat transfer. The effects of nanofluid concentration on pressure drops were investigated through experiments conducted in both parallel- and counter-flow conditions.

Temporal and Spatial Thermal Performance of A Ground Heat Exchanger in Response to Bridge Solar Recharging and Deicing Operations: A Pilot Full-Scale Study

A full-scale mock-up geothermal bridge was built in Texas, USA, to evaluate the field performance of a novel external geothermal bridge de-icing system. The geothermal bridge system comprises a single U-loop ground heat exchanger (GHE) 131 m deep, a geothermal heat pump, four circulation pumps, and hydronic heating loops attached to the bridge deck. A comprehensive monitoring system was implemented to monitor the spatial ground temperature response. The geothermal bridge system was operated and monitored for solar collector and bridge de-icing operations totaling 99 days between August 2019 and April 2020. An average heat injection of 5.7 W/m was observed during the solar collector operation. Based on the defined control volume, approximately 48.9–380.8 kWh of energy, corresponding to 3.7-28.5% of the total injected energy, was available at the end of the solar-collector operation. Moreover, test results showed that 31.7-39.4% of stored thermal energy was preserved for utilization in the first winter de-icing test. The radius of the influence zone of the GHE operation was found to be 3.45 m. The outcome of the field experimental studies and further data collection performed over a year of operations showed that the heat injection into the soil by bridge solar collector was 54% more effective than heat extraction from the ground during the several de-icing tests performed from 2019 to 2020. 

Thermal performance of medium-deep U-type borehole heat exchanger based on a novel numerical model considering groundwater seepage

The medium and deep U-type borehole heat exchanger (MDUBHE) system is a novel technology to extract deep geothermal energy for building heating. The thermal performance of MDUBHE is influenced by multiple factors, where groundwater seepage is one of the most significant factors. To our best knowledge, the effects of groundwater seepage on MDUBHE are still unclear. In this paper, a novel numerical heat transfer model for MDUBHE considering groundwater seepage is proposed, and validated by CFD simulation and experimental data, with root mean square errors of 0.5 °C and 1.8 °C, respectively. Based on the novel numerical model, the effects of groundwater seepage on thermal performance of MDUBHE and thermal recovery characteristics of rock-soil are investigated. The results show that the computational efficiency of the novel numerical model is improved by two orders of magnitude compared with CFD software in the same case. The heat extraction rate of MDUBHE gradually increases with increase of seepage velocity. The heat extraction rate is improved by 13.63 % when the seepage velocity is 5.0 × 10−7 m/s. Furthermore, groundwater seepage can improve the thermal recovery rate of rock-soil. Compared with no groundwater seepage, the thermal recovery rate is improved by 7.60 % when the seepage velocity is 1.0 × 10−7 m/s. This study is significant for revealing the effect of groundwater seepage on the MDUBHE system.

Modeling of pressure losses in a cylindrical duct with rectangular ribs

AbstractIn order to improve the thermal performance of heat exchangers and air collectors, we insert various forms of artificial roughness, known as ribs, into the useful duct. These ribs promote the creation of turbulent flows and enhance heat transfer by conduction, convection and radiation.However, the introduction of these ribs leads to an increase in pressure drop, requiring higher mechanical power to pump the heat transfer fluid. This experimental study focuses on estimating, using empirical approaches, the pressure losses induced by rectangular ribs with an inclined top. The ribs are made from 0.4 mm galvanized sheet steel.An experimental set-up was designed to measure the head losses generated by the ribs, from the point of entry to the point of exit from the useful duct. Using the dimensional analysis method, correlations were established to evaluate head losses as a function of flow regime and rib geometry and configuration (including different geometries for rib arrangement over the configuration area).

Numerical investigation on heat transfer performance of the segmented cementing coaxial heat exchanger

The segmented cementing coaxial heat exchanger is proposed in this paper, where different thermal conductivity cementing layers are used. Based on field tests, its numerical model is established, and results show that it consistently demonstrates better heat transfer performance compared to conventional coaxial heat exchanger and high thermal conductivity cementing coaxial heat exchanger, regardless of whether higher or lower inlet temperature and flow rate. Additionally, the influencing factors such as the thermal conductivity of the cementing layer, segmented point, flow rate, and inlet fluid temperature on the thermal performance of the segmented cementing coaxial heat exchanger is analyzed, which indicates that the thermal performance of heat exchanger reaches its maximum only when the segmented point of the cementing layer coincides with the thermal equilibrium point. And it is recommended that the thermal conductivity of the enhanced heat transfer cementing layer should not be less than 1.5 W/(m·K). Finally, the influencing factors of the thermal equilibrium point position are investigated to find that it is significantly affected by the inlet fluid temperature and flow rate, while its response to the operating time is not pronounced.

Investigation of heat transfer performance of double-walled pipes of heat exchanger for power plant applications

Heat transfer between contacting surfaces, is a key factor affecting the thermal performance of heat exchangers in power plants and other applications. Double-walled pipes, used in the heat exchangers, can significantly improve the safety factor of the system. In this research work, the thermal contact conductions (TCC) at the interfaces of double-walled stainless steel 316 L pipes under various contact pressures were investigated. These pipes were manufactured with the shrink-fitting method using servo-hydraulic universal testing machine. A numerical model, verified by X-ray diffraction analysis, was developed to investigate the contact pressure variation at the interfaces according to loading conditions. The contact pressure between the inner and outer walls was controlled in the range of 22.78 MPa to 25.70 MPa, by varying the tensile loading conditions. A phase-sensitive transient thermal method was developed to measure the thermal conductivity (TC) and TCC of double-walled pipes. TC was observed to be in the range of 15.13 W/mK to 15.84W/mK while TCC at the interface was observed to increase sharply with the contact pressure, reaching 17 × 103W/m2K under 25.70 MPa contact pressure.

Enhanced Thermal Performance of Shell and Tube Heat Exchangers Using TiO2/Water Nanofluids: An SST Turbulence Model Analysis

Enhanced Thermal Performance of Shell and Tube Heat Exchangers Using TiO2/Water Nanofluids: An SST Turbulence Model Analysis