Thermal Performance Of Heat Exchanger Research Articles

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.

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.

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

Numerical investigation and artificial brain structure-based modeling to predict the heat transfer of hybrid Ag/Au nanofluid in a helical tube heat exchanger

In recent years, due to the low thermal coefficients of common fluids and the increase in size and cost of heat exchangers, technologies for improving heat transfer and reducing dimensions have been developed and widely used in industries such as refrigeration, cooling of processing cells, chemical industries, and more. Previously, increasing heat exchange capacity in heat exchangers was achieved by altering parameters such as boundary conditions, flow geometry, heat exchanger geometry, or changing the type of fluid. Additionally, apart from the use of nanofluids, various other operational methods can be employed to improve the thermal performance of heat exchangers. Accordingly, considering the combination of the aforementioned innovative techniques, this study presents the modeling of flow and heat transfer inside helically coiled tube heat exchangers under the flow of nanofluids containing nickel, gold, silver, and gold/silver hybrid nanoparticles using numerical and artificial intelligence methods. In this study, the effect of variations in the inner diameter of the coiled tube and the volume fraction of nanoparticles was examined. The results showed that increasing the inner diameter and volume fraction of nanoparticles leads to an increase in heat transfer coefficient and Nusselt number, while the friction factor decreases with an increase in Reynolds number and increases with an increase in diameter and volume fraction. Finally, the accuracy and validity of the model were evaluated using statistical parameters and experimental results, which showed a 99.9% level of agreement between the predicted and experimental outcomes.

Comparative Analysis of Longitudinal Vortex Generators and Louvered Fins in Enhancing Thermal Performance in Compact Heat Exchangers

Comparative Analysis of Longitudinal Vortex Generators and Louvered Fins in Enhancing Thermal Performance in Compact Heat Exchangers

Thermal performance of a plate-type latent heat thermal energy storage heat exchanger - An experimental investigation and simulation study

Heat storage is key to reducing the mismatch between energy supply and demand. The performance of thermal energy storage heat exchangers is determined by the exchanger structure and the heat transfer fluid (HTF) parameters. In this paper, the heat exchanger structure and HTF parameters of a plate-type latent heat thermal energy storage (LHTES) heat exchanger were investigated through experiments and simulations. From the experimental tests, it was observed that thermocouples accelerated the melting process of paraffin by 6 % on average for a single LHTES plate. The LHTES plate with aspect ratio of 3:1 was the optimal structure with the shortest melting time. To figure out the optimal thermal performance of the LHTES heat exchanger, a mathematical model was developed by FLUENT and verified against the experimental data. The influence of LHTES plate thickness as well as the HTF temperature and velocity was numerically studied. A performance factor was proposed to evaluate the thermal performance for the melting process of plate-type LHTES heat exchangers. Simulation analysis shows that the highest performance factor is realized when the LHTES plate thickness is 15 mm, independent to the HTF temperature and velocity. When the HTF velocity is small, it is critical to focus on the design of plate thickness of the heat exchangers rather than increasing the HTF temperature.

Thermal performance of helical ground air heat exchanger under Saharan climate conditions: an experimental study

Thermal performance of helical ground air heat exchanger under Saharan climate conditions: an experimental study

Thermal performance analysis of a counter-flow double-pipe heat exchanger using titanium oxide and zinc oxide nanofluids

In a nanofluid, metals, oxides, or carbides with a diameter of less than 20 nm are combined as one with a base liquid, like water or an oil. Many examinations have recently been completed to inspect the effect of nanofluid on the speed increase of heat transfer rates in various heat exchangers. Heat transfer improvement using nanofluid is dependent on a variety of factors, among them the kind of nanoparticles, their size, shape, and concentration in the base fluid. The proposed article is aimed to study experimentally how a twin-pipe heat exchanger with counter-flow arrangements and two kinds of nanofluid cooling fluid performed. Zinc oxide (ZnO) and titanium oxide (TiO2) are used as base fluids with ethylene glycol (EG) and alkaline water. This study looked at the heat transfer capabilities of a two-pipe heat exchanger with a counter-flow configuration when various quantities of TiO2 and ZnO nanoparticles were combined with EG alkaline water. Alkaline water and nanofluid nanoparticle volume concentrations were 0.5, 0.75, and 1.25. The constant intake temperatures of 60 °C for water and 30 °C for nanofluid in a heat exchanger result in two fluids running at a constant inflow velocity. It was found that nanofluid had higher heat absorption at low flow rates than EG alkaline water and hence improved heat exchanger thermal performance. It was also noticed that when the concentration of nanoparticles increases, the heat transmission rate increases.

Experimental Investigation of the Effect of Integrated Fins on Heat Transfer Rate of Double Pipe Heat Exchanger

In this paper, the effects of integrated fins on the thermal performance of the concentric tube heat exchanger with a variable flow rate of hot and cold water are discussed. The inner pipe is made of copper pipe of length = 800 mm, OD=30 mm, ID=26 mm, t=2 mm. the integrated fines of the geometry 1.25 mm and 1.5 mm pitch length, 1 mm of the depth of cut are considered in the study. The thermal performance of the heat exchanger with a flow rate of hot and cold fluids ranges from 0.014 kg s- 1 to 0.07 kg s-1 and the effects of parallel and counter flow direction are also discussed in detail. The experimental result confirms that the thermal performance of the concentric tube heat exchanger is more in the case of the tube with integrated fins and counter flow direction with the highest flow rate of water in the pipe and annulus of the heat exchanger.

Effects of Key Parameters on Nanofluid Thermal Performance in Heat Exchangers

AbstractNanofluids are utilized in cooling equipment such as heat exchangers and renewable energies such as solar cells as heat transfer fluid. The techniques for nanofluid stability enhancement and stability evaluations, such as zeta potential, electron microscopy, and photographic techniques for sedimentation, are reviewed as well as some recent achievements in nanofluid stabilization and research on the parameters affecting the thermal properties of nanofluids. Finally, the applications of nanofluids in cooling devices are described. Increased heat transfer, reduced heat transfer time and size of heat exchangers, and finally higher energy and heat efficiency could be the most significant achievements. The parameters affecting the thermal conductivity of nanofluids include concentration, temperature, particle fluid, type of base fluid, and nanoparticles.