Computational Analysis of Nanofluids in Heat Exchanger

In this paper, the shell and tube heat exchanger is analyzed with ANSYS Fluid Flow (Fluent), where the shell contains of tubes inside it. The hot water flows through the tubes and cold water flows through the shell side. The heat transfer, velocity, temperature, pressure, and streamline flow of the fluid are analyzed in this study. The analysis is undertaken for (a) single shell and tube heat exchanger (b) single shell and tube heat exchanger using a corrugated tube. The experimental study shows that the temperature drop (\(\Delta T\)) and pressure drop (\(\Delta P\)) of the heat exchanger in the tube side for counterflow is more than parallel flow configuration in both plain and corrugated pipes. Moreover, the corrugated pipe has approximately 6 K more temperature drop in the tube side than the plain pipe heat exchanger model. Consequently, the pressure drop in corrugated heat exchanger is 37.5 times more than that of the plain pipe heat exchanger. The results suggest that with increase of mass flow rates, the temperature difference between the inlet and the outlet of the pipe decreases. The variation of temperature in the shell and tube sides of the heat exchanger is found to be higher in case of few baffles are used as compared to no baffle conditions.KeywordsANSYSPressure dropSimulationPlainCorrugation

Numerical simulations of a high temperature shell and tube heat exchanger and chemical decomposer (thereafter — heat exchanger) with straight tube configuration have been performed using Fluent 6.2.16 code to examine flow distribution on the tube side. The heat exchanger can be a part of sulfur iodine thermochemical water splitting cycle which is one of the most studied cycles for hydrogen production. Uniformity of the flow distribution in the heat exchanger is very critical because the flow maldistribution among the tube or shell sides can result in decreasing of chemical decomposition and increasing of pumping power. In the current study the flow rate uniformity in the heat exchanger tubes has been investigated. Simulations of the straight tube configuration, tube configuration with baffle plate arrangement and with pebble bed region inside the tubes were performed to examine flow distribution on the tube side. It was found the flow maldistribution along the tube direction is very serious with the simple tube configuration. An improvement of the header configuration has been done by introducing a baffle plate in to the header section. With the introduction of the baffle plate, there was a noticeable decrease in the flow maldistribution in the tubes. Uniformity of flow was also investigated with catalytic bed inside the tubes. A significant decrease in flow maldistribution was observed with this arrangement. But if the catalytic bed zone is created on the shell side, then the improved header configuration with a baffle plate is best suitable to avoid flow maldistribution.

An updated review on application of nanofluids in heat exchangers for saving energy

Heat transfer and pressure drop performance of twisted oval tube heat exchanger

Kerosene−alumina nanofluid flow and heat transfer in the presence of magnetic field are studied. The basic partial differential equations are reduced to ordinary differential equations which are solved semi analytically using differential transformation method. Velocity and temperature profiles as well as the skin friction coefficient and the Nusselt number are determined analytically. The influence of pertinent parameters such as magnetic parameter, nanofluid volume fraction, viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed. Results indicate that skin friction coefficient decreases with increase of magnetic parameter, nanofluid volume fraction and viscosity parameter. Nusselt number increases with increase of magnetic parameter and nanofluid volume fraction while it decreases with increase of Eckert number and viscosity parameter.

Pressure drop considerations with heat transfer enhancement in heat exchanger network retrofit

Innovations in the field of nanotechnology have potential to improve industrial productivity and performance. One promising applications of this emerging technology is using nanofluids with enhanced thermal properties. Nanofluids, engineered colloidal suspensions consisting of nano-sized particles (less than 100nm) dispersed in a basefluid, have shown potential as industrial cooling fluids due to the enhanced heat transfer characteristics. Experiments are conducted to compare the overall heat transfer coefficient and pressure drop of water vs. nanofluids in a laboratory scale industrial type shell and tube heat exchanger. Three mass particle concentrations, 2%, 4% and 6%, of SiO2-water nanofluids are formulated by dispersing 20 nm diameter nano particles in desalinated water. Nanofluid and tap water are then circulated in the cold and hot loops, respectively, of the heat exchanger to avoid direct particle deposition on heater surfaces. Interestingly, experimental result show both augmentation and deterioration of heat transfer coefficient for nanofluids depending on the flow rate through the heat exchangers. This trend is consistent with an earlier reported observation for heat transfer in micro channels. This trend may be explained by the counter effect of the changes in thermo-physical properties of fluids together with the fouling on the heat exchanger surfaces. The measured pressure drop in the nanofluids flow shows an increase when compared to that of basefluid that could limit the use of nanofluids in heat exchangers for industrial application.

This research discusses the literature on experimental investigations of heat transfer improvement with the help of nanofluids in heat exchangers. The research does show that the performance of the compound is better in terms of heat transfer than the base fluids in the horizontal shell and tube heat exchangers. Nevertheless, the viscosity increases with the nanoparticle concentration, and this influences the friction factor. This study reveals that the application of nanofluids increases the performance of heat exchangers in the cross-flow low integral finned tubes. The experimental studies reveal that there is an enhancement in thermal conductivity and heat transfer coefficients in Al₂O₃/distilled water nanofluid that makes them suitable for improving the heat exchanger efficiency. The experiments were performed at concentrations of γ-Al₂O₃ of 0.0%, 0.1%, and 0.5%, at the temperatures of 45 °C, 55 °C, and 65 °C, and at the γ-Al₂O₃/water flow rates of 2, 4, and 6 LPM. Experiments reveal that finned tubes increase the heat transfer coefficients, which is useful for understanding the performance of heat exchangers under various operating conditions. For instance, the addition of 0.5% Al₂O₃ resulted in an increase of heat transfer rate by 30% and heat transfer coefficient by 22% when the flow rate was 4 LPM and the temperature was 65°C. The Nusselt number also rose by 8% for Al₂O₃ nanofluid compared to distilled water under the same conditions. This research supports that under optimized concentrations of nanofluids, thermal management in heat exchangers is enhanced with the thermal efficiency increasing with the Re to a point of optimum at Re=7000. This work improves heat transfer in finned tube heat exchangers with nanomaterial-water mixtures and presents correlations, recommendations, and directions for further work.

The goal of this research is to model a three-dimensional steam-producing plant heat exchanger for industrial operations. With a certain tube bundle structure, inlet temperatures and the velocity of the tube and shell sides are used as input factors in the current investigation. The heat transfer study takes hot flue gas inside the tubes and steam on the shell side into account. The model was designed and simulated using ANSYS 2020 fluent for the analysis, which was authenticated by contrasting the output results to actual in-house operating data. According to the computational results, the proposed design allowed for a 9oC rise in shell-side fluid temperature. It has been discovered that installing more baffles in the steam flow channel increases the fluid pressure moving through the heat-exchanger. When compared to the WKX110 model, the velocity along the PMX110 length was more uniform. The velocity distribution indicates that the velocity is particularly high at the baffle turns. This is helpful because the high velocity encourages high convection transfer of heat in the region; therefore, the installation of this baffle improves heat exchange efficacy. The numerical PMX110 and WKX110 findings were validated with experimental data and found to be in good agreement.

Experimental and CFD investigation of helical coil heat exchanger with flower baffle

The cooling system in a steam power plant is a closed-process cooling system that uses a heat exchanger with a cheap heat receiver transfer medium such as seawater.The closed cooling system heat exchanger has problems, namely frequent tube leaks and decreased effectiveness.This condition is fascinating to re-analyze by studying and calculating essential variables in the heat exchanger.Heat Exchanger (HE), a demineralized water cooler in the C3W system, uses a shell and tube heat exchanger.This heat exchanger, on the shell side, is passed by demineralized water fluid with an input temperature of 37 C and an output temperature of 30 C, and on the tube side, is passed by seawater fluid with an input temperature of 28 C and an output temperature of 31 C. The design standard will refer to the dirt factor value.HE is critical in the process that occurs in the plant, so it needs good design.This design will be carried out by calculation and simulation methods.The design standard refers to a dirt factor value of 0.0015 and a pressure drop of 10 psi (TEMA standard).The design calculation produces a dirt factor value of 0.0015 with a pressure drop of 6.32 psi (shell side) and 3.17 psi (tube side).

Shell and tube heat exchangers are the most important tools in heat transfer process. Optimization efficiency of these tools is always the goal of designers. Now a day there are a lot of efficient methods for selecting the best heat exchanger, such as analytic and numerical methods that everyone has advantages and defects. For example, confront of jamming in calculations by receiving to the local minimums and errors during interruption quantities. Today by entering of simulation and design softwares in industries, the simulation of process tools is so simple. the procedure of studies in this thesis is in these steps: first simulation of sulfur solidification heat exchangers in ASPEN B-JAC software same as operation conditions and then evaluation the effects of changing the design parameters in tube bundle section such as number of passes, arrangement of tubes, number of baffles,…. the sulfur solidification package’ heat exchanger that it’s active fluid is demine water for cooling of package will be optimized till the rate of exchanged heat increases to 15 percent and pressure drop will not affect the operation conditions. The most important note in the correction of tube bundle is that the heat exchanger should be out of service and stopping of production, on the other hand changing in shell of heat exchanger needs to change the piping system and redesign of supports that will spend a lot of time for shut down of plant, so it is out of order for this thesis and optimization of tube bundle will be done.

Low-finned tubes can be effective in baffled flow heat exchangers, if the heat transfer coefficients on either side of the heat exchanger differ greatly and therefore limit the thermal conductance of the heat exchanger. Low-finned tubes can increase thermal conductance by providing additional heat transfer area on the limiting side. The height and the spacing of the low-fins must be greater than the thickness of the thermal boundary layer on the low-finned side of the heat exchanger. Otherwise, the effectiveness of the additional area that the low-finned tubes provide will be reduced. The boundary layer thickness is dependent on the velocity and the thermophysical properties of the fluids. Therefore, in a standard shell-and-tube heat exchanger, the number of heat exchanger shell-side baffles needs to be properly considered to provide the correct shellside velocity without introducing too much pressure drop. Testing of a shell-and-tube heat exchanger containing low-finned tubes varied the flow rate and pressure of the supercritical CO2 on the shell side as water provided the cooling on the tube side. The testing maintained the temperature and pressure of the CO2 above the critical point in order to determine the changes in the effectiveness of the low-finned tubes and thus the heat transfer rate of the heat exchanger. The results show that the additional heat transfer area provided by the low-finned tubes will remain fully effective, even as the supercritical fluid nears its critical point or a pseudo-critical temperature. This result also supports (but is not sufficient to prove) the guidance to limit the estimated thickness of the thermal boundary layer to the fin height and twice the fin spacing to ensure the additional heat transfer area provided by the low-finned tubes remain effective.

In the present investigation, second‐law based thermodynamics analysis was applied to a new heat exchanger with helical baffles. The helical baffles are designed as quadrant ellipses and each baffle occupies one quadrant of the cross‐section of the shell side. Experimental tests were carried out with cold water in the tube side with a constant flow rate, and hot oil on the shell side with flow rate range from 4–24 m3/h. The temperatures and pressures for the inlet and outlet of both sides were measured. The heat transfer, pressure drop, entropy generation, and exergy loss of the new heat exchanger were investigated and compared with the results for a conventional shell‐and‐tube heat exchanger with segmental baffles. The computed results indicated that both the entropy generation number and exergy losses of the new heat exchanger design are lower than those of the heat exchanger with segmental baffles, which means that the novel heat exchanger has a higher efficiency than the heat exchanger with segmental baffles, from the second‐law based thermodynamics viewpoint.

PurposeA computational fluid dynamics based parametric analysis for shell and helical tube heat exchanger (SHTHE) using CuO/water and Al2O3/water nanofluids is the main purpose of the present work. The parameters having impact on the performance of a heat exchanger have been studied in depth. As the solid nanoparticle shows higher thermal conductivity compared to liquid particles, inclusion of this nanoparticle into the base fluid significantly enhances the thermal conductivity of the liquid. Incorporation of nanofluid in the heat exchanger can increase its performance.Design/methodology/approachThe simulation is performed in Solid-Works flow simulation, and the performance of SHTHE is observed by varying the pitch of helical tube from 0.013 to 0.018 m and coil diameter from 0.0813 to 0.116 m, keeping the other parameters constant. The tube side and shell side flow rate is kept as 2 LPM.FindingsThe results indicate that the effectiveness of the heat exchanger increases with the increase of pitch and coil diameter. The maximum effectiveness of 0.5022 for CuO/water and 0.4928 for Al2O3/water nanofluid is observed at a pitch of 0.018 m and the coil diameter of 0.116 m.Originality/valueIt is observed that CuO/water nanofluid shows better performance compared with Al2O3/water nanofluid. For a coil diameter of 0.116 m and pitch of 0.018 m, the SHTHE with CuO/water nanofluid shows 1.82% greater effectiveness compared to the effectiveness with Al2O3/water nanofluid.