Search for: heat-exchangers
0.009 seconds
Total 216 records

    Heat transfer enhancement in shell-and-tube heat exchangers using porous media

    , Article Heat Transfer Engineering ; Volume 36, Issue 3 , 2015 , Pages 262-277 ; 01457632 (ISSN) Esmaeili Rad, S ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    A numerical simulation has been carried out to investigate the heat transfer enhancement in a shell-and-tube heat exchanger using a porous medium inside its shell and tubes, separately. A three-dimensional geometry with k-ε turbulent model is used to predict the heat transfer and pressure drop characteristics of the flow. The effects of porosity and dimensions of these media on the heat exchanger's thermal performance and pressure drop are analyzed. Inside the shell, the entire tube bundle is wrapped by the porous medium, whereas inside the tubes the porous media are located in two different ways: (1) at the center of the tubes, and (2) attached to the inner wall of the tubes. The results... 

    Experimental optimization of geometrical parameters on heat transfer and pressure drop inside sinusoidal wavy channels

    , Article Thermal Science and Engineering Progress ; Volume 9 , 2019 , Pages 121-131 ; 24519049 (ISSN) Erfanian Nakhchi, M ; Sharif University of Technology
    Elsevier Ltd  2019
    The response surface methodology (RSM) is firstly employed to investigate the geometric and flow parameters on heat transfer, pressure drop and thermal performance of sinusoidal wavy channels with different phase shifts. The investigated flow and geometric parameters are axial Reynolds number 1106

    Application of heat pipe heat exchangers in heating, ventilation and air conditioning (HVAC) systems

    , Article Scientific Research and Essays ; Volume 6, Issue 9 , May , 2011 , Pages 1900-1908 ; 19922248 (ISSN) Firouzfar, E ; Soltanieh, M ; Hossien Noie, S ; Hassan Saidi, M ; Sharif University of Technology
    A literature review on the studies and applications of heat pipe heat exchanger in air conditioning systems in recent years is conducted. The related papers were grouped into two main categories and a summary of experimental and theoretical studies is presented. Based on this investigation, the application of a heat pipe heat exchanger or a thermosyphon heat exchanger in the conventional air conditioning systems is recommended as an efficient means for energy savings and dehumidification enhancement to maintain acceptable room conditions. This review shows that the literature on the application of heat pipe heat exchangers in air conditioning systems is very limited. Therefore, much more... 

    Entropy generation minimisation analysis of cross-flow heat exchangers used in indirect evaporative air conditioners

    , Article International Journal of Exergy ; Volume 6, Issue 1 , 2009 , Pages 61-79 ; 17428297 (ISSN) Eslamian, M ; Heydari, A ; Ghezelbash, P ; Sharif University of Technology
    In this paper, entropy generation in heat exchangers used in Indirect Evaporative Coolers (IDECs) is studied. First, expressions for the rate of entropy generation in tube-type and plate-type cross-flow heat exchangers used as IDECs are obtained. Then, by introducing appropriate geometric constraints and employing thermohydraulic design equations, the variation of the rate of entropy generation within the heat exchangers is investigated. The maximum EER, outlet temperatures and the optimum sizes are obtained for several cases. The results of several experiments conducted on an optimum tube-type experimental prototype are presented and compared with the numerical data. Copyright © 2009... 

    Numerical investigation of the inlet baffle, header geometry, and triangular fins effects on plate-fin heat exchangers performance

    , Article Heat Transfer Engineering ; Volume 36, Issue 16 , 2015 , Pages 1397-1408 ; 01457632 (ISSN) Salehi, S ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    In this study, the optimal location of baffle in the header of air-to-air plate heat exchangers and the geometry of the header and the effects of triangular fins arrays on the effectiveness were numerically investigated for different flow rates and Reynolds numbers on different models. The main purpose of inlet baffle and geometry changes is to improve the pattern of flow distribution and assist flow uniformity. The investigations show that the optimal location of the inlet baffle with high Reynolds numbers has an insignificant effect on effectiveness, while with Reynolds numbers 250-3000, the effectiveness is affected significantly by baffle location. On the other hand, the reduction in... 

    Analytical modeling of convective condensation in smooth vertical tubes

    , Article Scientia Iranica ; Volume 8, Issue 2 , 2001 , Pages 123-129 ; 10263098 (ISSN) Nouri Borujerdi, A ; Sharif University of Technology
    Sharif University of Technology  2001
    In this paper, an analytical model is presented for forced convective film condensation inside smooth vertical tubes, in which Prandtl mixing length theory, Van Driest hypothesis and Reynolds analogy are used. Comparison of this model with the available experimental data and three other correlations reported in the literature demonstrates that the results are in satisfactory and close agreement  

    Parametric Study and Numerical Simulation of Spiral Wound Heat Exchanger Performance at Cryogenic Temperatures

    , M.Sc. Thesis Sharif University of Technology Hosseinian Khorasgani, Mohsen (Author) ; Afshin, Hossein (Supervisor)
    Cryogenic is the study of physical phenomena at temperatures below 123 Kelvin. One of the applications of cryogenic science is the liquefaction of gases. In the liquefaction cycles of gases, such as helium liquefaction, fluidization occurs in the pressure reducing valve but temperature of the gas should be greatly reduced before it enters the pressure reducing valve. For this purpose, high-performance heat exchangers should be used. Spiral Wound is one of the heat exchangers that has ability to achieve over 90% efficiency due to its structure. Researchs in the field of design and simulation of spiral heat exchangers are limited and are done with a lot of simple assumptions such as constant... 

    A general multi-scale modeling framework for two-phase simulation of multi-stream plate-fin heat exchangers

    , Article International Journal of Heat and Mass Transfer ; Volume 156 , 2020 Niroomand, R ; Saidi, M. H ; Hannani, S. K ; Sharif University of Technology
    Elsevier Ltd  2020
    Compact heat exchangers are among the vital components used in various industries. In this study, a general framework has been developed with a multi-scale point of view for three-dimensional simulation of multi-stream plate-fin heat exchangers. The most important features in the MSPFHEs simulation, such as phase change phenomena, multi-component mixtures, multiple streams, transversal, lateral and longitudinal conduction, non-uniformity of inlet flow, variable fluid properties, and heat leakage are simultaneously considered in this model. The modular form of the model structure has facilitated layer-by-layer simulation of cross flow heat exchangers as well as parallel flow ones. Our model... 

    Optimal Design of Cryogenic Heat Exchanger for Gas Liquefication Cycle

    , M.Sc. Thesis Sharif University of Technology Ebrahimi Ghalinghieh, Hamed (Author) ; Afshin, Hossein (Supervisor)
    Gas liquefication in low temperatures is one of the most challenging fields in engineering due to complexity of its thermodynamic analisys and fabrication of equipments. Heat Exchangers are one of the most important equipments in these prosseces. High prices of Heat Exchangers in these facilities makes their Optimal and cost effective design, of crucial importance. In this thesis three dimensional model of a Plate Fin Heat Exchanger is thoroughly investigated. Fistly, by means of Aspen Heat Exchanger design Software a counter flow Heat Exchanger is designed. This HX is to be placed in Collins cycle, so, working fluid in both hot and cold streams is Helium Gas. The HX then by means of ANSYS... 

    An experimental study on the proper criterion to judge the thermal performance of the nanofluids

    , Article International Communications in Heat and Mass Transfer ; Volume 82 , 2017 , Pages 20-28 ; 07351933 (ISSN) Sajedi, R ; Jafari, M ; Nasirivatan, S ; Osanloo, B ; Sharif University of Technology
    Elsevier Ltd  2017
    This work is dedicated to finding a suitable measure to judge thermal performance of nanofluids. The importance of this issue arises from misleading claim of excess heat transfer of nanofluids compared to the base fluid, neglecting the hydraulic effects such as increase in pressure drop. To clarify the issue, the experimental setup with capability to create constant Reynolds number and constant pumping power is constructed. Thermal behavior of nanofluids of silicon oxide/water and aluminum oxide/water and distilled water in developing region of laminar flow regime is investigated. In this regard, the convective heat transfer coefficient within the finned tube heat exchanger is evaluated.... 

    Numerical investigation of different geometrical parameters of perforated conical rings on flow structure and heat transfer in heat exchangers

    , Article Applied Thermal Engineering ; Volume 156 , 2019 , Pages 494-505 ; 13594311 (ISSN) Erfanian Nakhchi, M ; Esfahani, J. A ; Sharif University of Technology
    Elsevier Ltd  2019
    A numerical study has been performed to investigate the flow and heat transfer characteristics of fluid flow through heat exchanger tubes fitted with perforated conical rings. The holes are circular, and the number of holes N is ranged from 0 to 10. The influences of perforated conical ring diameter ratios D2/D1=0.4,0.5and0.6 and the hole diameter ratios d/D=0.06,0.1and0.14 on average Nusselt number, friction factor and thermal performance factor are reported. This analysis is performed in the turbulent flow regime 4000⩽Re⩽14,000 and the governing equations are solved by using (RNG) k-∊ model. Due to strong turbulent intensity, perforated conical rings lead to more flow perturbation and... 

    A new multiscale modeling framework for investigating thermally-induced flow maldistribution in multi-stream plate-fin heat exchangers

    , Article International Journal of Heat and Mass Transfer ; Volume 180 , 2021 ; 00179310 (ISSN) Niroomand, R ; Saidi, M. H ; Hannani, S. K ; Sharif University of Technology
    Elsevier Ltd  2021
    Multi-stream Plate-fin heat exchangers (MSPFHEs) are among the most efficient heat exchangers in energy-based industries. They should be carefully designed to have maximum effectiveness and to avoid wasting energy. Flow maldistribution could significantly degrade the performance of heat exchangers. This study presents a novel modeling framework to capture the thermally-induced maldistribution in two-phase MSPFHEs. The developed model is used to show how thermally-induced flow maldistribution affects the performance of the heat exchanger, and some possible modifications are investigated to reduce its consequences. Our case study results show that thermally-induced maldistribution decreases... 

    Numerical Modeling of Flow and Heat Transfer Inside Helical Tubes for Cryogenic Temperature Ranges

    , M.Sc. Thesis Sharif University of Technology Mondegari, Mohsen (Author) ; Afshin, Hossein (Supervisor)
    Spiral-wound heat exchangers have special applications in industry due to their high efficiency, especially in low temperature ranges (cryogenic) such as gas liquefaction cycles; However, due to drastic changes in properties, the mechanism of flow and heat transfer in this type of exchangers has not been fully studied yet. Therefore, accurate modeling of fluid flow on both sides of tubes and shells as well as heat transfer between them can be very important in analyzing and designing this type of exchangers and optimizing them to increase the efficiency of the exchanger and the cycle. In this study, the focus is on the flow and heat transfer of supercritical fluid inside helical tubes of... 

    Fluctuation relation for heat exchange in Markovian open quantum systems

    , Article Physical Review E ; Volume 97, Issue 4 , April , 2018 ; 24700045 (ISSN) Ramezani, M ; Golshani, M ; Tayefeh Rezakhani, A ; Sharif University of Technology
    American Physical Society  2018
    A fluctuation relation for the heat exchange of an open quantum system under a thermalizing Markovian dynamics is derived. We show that the probability that the system absorbs an amount of heat from its bath, at a given time interval, divided by the probability of the reverse process (releasing the same amount of heat to the bath) is given by an exponential factor which depends on the amount of heat and the difference between the temperatures of the system and the bath. Interestingly, this relation is akin to the standard form of the fluctuation relation (for forward-backward dynamics). We also argue that the probability of the violation of the second law of thermodynamics in the form of the... 

    Assessment and comparison of different arrangements of horizontal ground heat exchangers for high energy required applications

    , Article Applied Thermal Engineering ; Volume 167 , 2020 Asgari, B ; Habibi, M ; Hakkaki Fard, A ; Sharif University of Technology
    Elsevier Ltd  2020
    Horizontal ground heat exchangers (GHEs) have a lower initial installation cost in comparison to vertical ones; however, they require more land area. In order to reduce the required land area of horizontal GHEs, their heat exchange rate per unit land area needs to be enhanced. A remedy to this problem is installing horizontal GHEs in an arrangement with maximum heat exchange rate per unit land area. However, such arrangements have not been introduced for different types of horizontal GHEs thus far. To this end, in this study, the thermal performance of various GHE pipe arrangements for three different types (linear, spiral, and slinky) of horizontal GHEs is evaluated. Comparing the obtained... 

    Experimental study of thermal performance and pressure drop in compact heat exchanger installed in automotive

    , Article 2006 Spring Technical Conference of the ASME Internal Combustion Engine Division, Aachen, 7 May 2006 through 10 May 2006 ; 2006 , Pages 551-557 ; 15296598 (ISSN) ; 0791842061 (ISBN); 9780791842065 (ISBN) Saidi, M. H ; Esmaeili Sany, A. R ; Mozafari, A. A ; Neyestani, J ; Sharif University of Technology
    In this Study, radiator performance for passenger car has been studied experimentally in wide range of operating conditions. Experimental prediction of Nusselt number and heat transfer coefficient for coolant in radiator tubes are also performed with ε-NTU method. The total effectiveness coefficient of radiator and heat transfer coefficient in air side is calculated via try and error method considering experimental data. The Colburn factor and pressure drop are also estimated for this heat exchanger. Examples of application demonstrate the practical usefulness of this method to provide empirical data which can be used during the design stage. Copyright © 2006 by ASME  

    Numerical investigations of heat transfer and pressure drop of condensation in streamwise-periodic herringbone-type plate channels

    , Article International Journal of Heat Exchangers ; Volume 7, Issue 1 , 2006 , Pages 163-180 ; 15245608 (ISSN) Akbari, M ; Farhanieh, B ; Sharif University of Technology
    Turbulent fully developed periodic condensation heat transfer and pressure drop in herringbone-type plate heat exchangers for R134a and steam were numerically investigated. A mixture model was introduced and the equations governing the two phase flow were simplified. Thus a single phase periodic flow with mixture properties was solved for R134a. For Steam a separate empirical model was used. The governing equations were solved numerically by a finite-volume method for elliptic flows in complex geometries using collocated variable arrangement. The influence of mass flux and vapor quality on frictional pressure drop for refrigerant was investigated. The heat transfer was studied using a... 

    Design of Heat Exchanger in Thermoacoustic Systems

    , M.Sc. Thesis Sharif University of Technology Hasibi, Iman (Author) ; Ghorbanian, Kaveh (Supervisor)
    In this research, the principles of design of Heat Exchangers in thermoacoustic systems are developed. The Heat Exchangers as a essential part of thermoacoustic systems, complete the thermodynamic cycle in these systems. In this thesis, principles and algorithms of design for Shell&Tube, Plate and Screen Heat Exchangers are described and these principles are validated for each kind of Heat Exchangers. Then the balance of exergy is studied in thermoacoustic systems and at the end, for every Heat Exchangers amount of exergy destruction is evaluated for oscillating and non-oscillating fluids. Based on fitness functions of exergy destruction, heat transfer area and acoustic pressure drop, Heat... 

    Multi-Stream Multiphase Flow Plate Fin Heat Exchanger Design Optimization to Reduce Pressure Drop and Improve Efficiency

    , M.Sc. Thesis Sharif University of Technology Afrasiabi, Mohammad Hassan (Author) ; Afshin, Hossein (Supervisor)
    Optimization of Plate-Fin Heat Exchnagers, which have various applications in different cryogenic processes nowadays, can have a significant role in improving process efficiency as well as decreasing their capital and operationl costs. In this study, is introduced a procedure to optimize the performance of multi-stream multi-phase Plate-Fin Heat Exchangers, implementing Genetic Algorithm optimization method. In this study, the simulation of the multi-stream multi-phase Plate-Fin Heat Exchanger is carried out by Aspen EDR, a leading software in simulation and design of different types of heat exchangers. The software is then integrated to external software to automate the simulation... 

    Twisted bundle heat exchangers performance evaluation by CFD (CJ12/5054)

    , Article International Communications in Heat and Mass Transfer ; Volume 39, Issue 10 , 2012 , Pages 1654-1660 ; 07351933 (ISSN) Jahanmir, Gh. S ; Farhadi, F ; Sharif University of Technology
    Shell and tube heat exchanger with single twisted tube bundle in five different twist angles, are studied using computational fluid dynamics (CFD) and compared to the conventional shell and tube heat exchanger with single segmental baffles. Effect of shell-side nozzles configurations on heat exchanger performance is studied as well. Heat transfer rate and pressure drop are the main issues investigated in the paper. The results show that, for the same shell-side flow rate, the heat transfer coefficient of heat exchanger with twisted tube bundle is lower than that of the heat exchanger with segmental baffles while shell-side pressure drop of the former is even much lower than that of the...