Efficiency and Effectiveness Concepts Applied in Shell and Tube Heat Exchanger Using Ethylene Glycol-Water Based Fluid in the Shell with Nanoparticles of Copper Oxide (CuO)

This article consists of an analytical solution for obtaining the outlet temperatures of the hot and cold fluids in a shell and tube heat exchanger. The system analyzed through the concepts of efficiency, effectiveness (ε-NTU), and irreversibility consisted of a shell and tube heat exchanger, with cold nanofluid flowing in the shell and hot water flowing in the tube. The nanofluid consists of 50% of ethylene glycol and water as the base fluid and copper oxide (CuO) nanoparticles in suspension. The volume fractions of the nanoparticles range from 0.1 to 0.5. The flow rate in the nanofluid ranges from 0.0331 to 0.0568 Kg/s, while two mass flow rates, from 0.0568 and 0.5 Kg/s, for the hot fluid, are used as parameters for analysis. Results for the efficiency, effectiveness, irreversibility, heat transfer rate, and outlet temperatures for cold and hot fluids were obtained graphically. The flow laminarization effect was observed through the results obtained and had significant relevance in the results.

Optimal design of heat exchanger header for coal gasification in supercritical water through CFD simulations

Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.

Performance Assessment of Heat Exchangers for Process Heat Integration

Pinch Analysis is an attractive solution for reduction of thermal energy costs in thermo-chemical industries.In this approach,maximum internally recoverable heat is determined and a heat exchange network is designed to meet the recovery targets.The thermal performance of a heat exchanger over its lifetime is however a concern to industries.Thermal performance of a heat exchanger is affected by many factors which include the physical prop-erties of the shell and tube materials,and the chemical properties of the heat transferfluid.In this study,thermal performance of shell and tube heat exchangers designed to meet heat recovery targets in a Pinch Analysis study is simulated.The aim of this paper is to present predictions of thermal performances of shell and tube heat exchan-gers with different heat transferfluids and geometries as they undergo fouling degradation.Engineering approaches based on thermodynamic analysis,heat balance and Kern Design equations,as well as what-if simu-lation modeling are used in this work.Shell and tube heat exchangers were designed to meet internal heat recov-ery targets for three process plants,A,B and C.These targets were published in a separate paper.The effects of degradation of the tubes-due to incremental growth of fouling resistance-on thermal performance of the exchan-ger were simulated using Visual Basic Analysis(VBA).Overall,it was found that growth in fouling reduces ther-mal efficiency of shell and tube heat exchangers with an exponential relationship.An increase of 100%of fouling resistance leads to an average reduction of 0.37%heat transfer.Higher values of logarithmic mean temperature difference(LMTD)and higher ratios of external diameter to internal diameter of the exchanger tubes amplify the effect of fouling growth on thermal performance of the exchangers.The results of this work can be applied in pinch analysis,during design of heat exchangers to meet the internal heat recovery targets,especially in predicting how fouling growth can affect these targets.This can also be useful in helping operators of shell and tube heat exchangers to determine cleaning intervals of the exchangers to avoid heat transfer loss.

Enhancing Heat Transfer and Energy Storage Performance of Shell-and-Tube Latent Heat Thermal Energy Storage Unit with Unequal-Length Fins

Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy storage unit.In this study,the novel unequal-length fins are designed from the perspective of synergistic benefits of heat transfer and energy storage performance,and the effects of arrangement,number and total length of unequal-length fins are numerically investigated.Results show that utilization of fins with ascending length,when short and long fins are located in the inlet and outlet of heat transfer fluid respectively,can further promote the heat transfer and energy storage performance compared with equal length fins,and a maximum 6.17%and 0.43%increment of heat transfer performance and stored energy is achieved in full melting time,respectively.The number of unequal-length fins plays a major role in the energy storage,and 18.95%and 0.91%improvement of heat transfer performance and stored energy is realized when equipped with 2 unequal-length fins.A 21.17%improvement of the heat transfer performance is obtained when the total length of unequal-length fins is 18 mm.The present study is helpful to make further efforts to enhance heat transfer and energy storage of shell-and-tube latent heat thermal energy storage unit with unequal-length fins.

Solidification in a shell-and-tube thermal energy storage unit filled with longitude fins and metal foam:A numerical study

In this study,an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials(PCMs).A numerical model was built and verified based on the comparison among the present model prediction,experimental measurements,and numerical results in open lit-erature.To highlight the novel design method,four cases including fin-PCM,foam-PCM,fin-foam-PCM,and PCM unit were compared by means of solidification features.The temperature distribution,solidification front propa-gation,and buoyancy-induced convection in the liquid PCM were accounted for.Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change.The combination of foam and fin achieved the best performance,leading to a 90.5%reduction in complete energy release time in comparison with the PCM unit.The proposed design method provided reference potentials for advancing energy storage engineering.However,buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement.A maximal 11.5%prolonging time for the complete solidification was found.

EXPERIMENTAL AND NUMERICAL ANALYSIS OF LAMINAR AND LOW TURBULENT FLOW DISTRIBUTIONS IN INLET DIVIDING HEADER OF SHELL AND TUBE HEAT EXCHANGER

Flow distribution headers play a major role in heat exchangers.The selection of header diameter,branch pipe diameter,branch pipe spacing etc.is based on the designer＇s experience and general guide lines.The proper selection of the header dimensions will yield uniform flow distribution in heat exchangers,which in turn will enhance the heat exchanger efficiency.In this work,the flow distribution in branch pipes and the pressure variation across the branch pipes in laminar and low turbulence region is studied with two models of the inlet dividing headers.When the numerical analysis has been applied,its inability to predict the no flow condition through the branch pipes is revealed.The results are presented in the form of flow rate ratio through branch pipes and nondimensional coefficients across branch pipes which are useful to apply the existing mathematical models for the present experimental setup.

Velocity Profiles between Two Baffles in a Shell and Tube Heat Exchanger

Heat exchangers are extensively utilized for waste heat recovery,oil refining,chemical processing,and steam generation.In this study,velocity profiles are measured using a 3D particle image velocimetry(PIV)system between two baffles in a shell and tube heat exchanger for parallel and counter flows.The PIV and computational fluid dynamics results show the occurrence of some strong vectors near the bottom.These vectors are assumed due to the clearance between the inner tubes and the front baffle.Therefore,the major parts of the vectors are moved out through the bottom opening of the rear baffle,and other vectors produce a large circle between the two baffles.Numerical simulations are conducted to investigate the effects of the baffle on the heat exchanger using the Fluent software.The k-εturbulence model is employed to calculate the flows along the heat exchanger.