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    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
    Abstract
    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... 

    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
    Abstract
    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... 

    Can Thermodynamic behavior of Alice’s particle affect bob’s particle?

    , Article Scientific Reports ; Volume 10, Issue 1 , 2020 Soltanmanesh, A ; Naeij, H. R ; Shafiee, A ; Sharif University of Technology
    Nature Research  2020
    Abstract
    We propose an experiment to investigate the possibility of long-distance thermodynamic relationships between two entangled particles. We consider a pair of spin-12 particles prepared in an entangled singlet state in which one particle is sent to Alice and the other to her distant mate Bob, who are spatially separated. Our proposed experiment consists of three different setups: First, both particles are coupled to two heat baths with various temperatures. In the second setup, only Alice’s particle is coupled to a heat bath and finally, in the last setup, only Bob’s particle is coupled to a heat bath. We study the evolution of an open quantum system using the first law of thermodynamics based... 

    An analytical solution for thermally fully developed combined pressure - electroosmotically driven flow in microchannels

    , Article International Journal of Heat and Mass Transfer ; Volume 50, Issue 5-6 , 2007 , Pages 1087-1096 ; 00179310 (ISSN) Qazi Zade, A ; Taghizadeh Manzari, M ; Hannani, S. K ; Sharif University of Technology
    2007
    Abstract
    An analytical solution is presented to study the heat transfer characteristics of the combined pressure - electroosmotically driven flow in planar microchannels. The physical model includes the Joule heating effect to predict the convective heat transfer coefficient in two dimensional microchannels. The velocity field, which is a function of external electrical field, electroosmotic mobility, fluid viscosity and the pressure gradient, is obtained by solving the hydrodynamically fully-developed laminar Navier-Stokes equations considering the electrokinetic body force for low wall zeta potentials. Then, assuming a thermally fully-developed flow, the temperature distribution and the Nusselt... 

    A review on application of nanofluid in various types of heat pipes

    , Article Journal of Central South University ; Volume 26, Issue 5 , 2019 , Pages 1021-1041 ; 20952899 (ISSN) Nazari, M. A ; Ahmadi, M. H ; Sadeghzadeh, M ; Shafii, M. B ; Goodarzi, M ; Sharif University of Technology
    Central South University of Technology  2019
    Abstract
    Nanotechnology is widely used in heat transfer devices to improve thermal performance. Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability. In the present article, a comprehensive literature review is performed on the nanofluids’ applications in heat pipes. Based on reviewed studies, nanofluids have a high capacity to boost the thermal behavior of various types of heat pipes such as conventional heat pipes, pulsating heat pipes, and thermosyphons. Besides, it is observed that there must be a selected amount of concentration for the high-performance utilization of nanoparticles; high concentration of nanoparticles causes a... 

    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
    Abstract
    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.... 

    An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels

    , Article Journal of Thermal Analysis and Calorimetry ; 2017 , Pages 1-10 ; 13886150 (ISSN) Pourfayaz, F ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
    Springer Netherlands  2017
    Abstract
    In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different... 

    Smooth modeling of solidification based on the latent heat evolution approach

    , Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 9-12 , 2017 , Pages 3041-3052 ; 02683768 (ISSN) Tavakoli, R ; Sharif University of Technology
    Springer London  2017
    Abstract
    The regularity problem of heat conduction equation corresponding to modeling of solidification based on the latent heat evolution approach is considered in the present study. It is shown that the corresponding PDE is actually semi-smooth, an issue that has not been taken into account explicitly in the related literature. A general smoothing (regularization) strategy is introduced to solve this problem. More specifically, the smoothed version of the effective heat capacity method is presented in this work. The presented approach is applied to model the quasi steady-state heat transfer problem in the continuous casting process. Numerical experiments demonstrate the success of the presented... 

    Experimental investigation of graphene oxide nanofluid on heat transfer enhancement of pulsating heat pipe

    , Article International Communications in Heat and Mass Transfer ; Volume 91 , February , 2018 , Pages 90-94 ; 07351933 (ISSN) Nazari, M. A ; Ghasempour, R ; Ahmadi, M. H ; Heydarian, G ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Pulsating heat pipes (PHPs) are heat transfer devices which are widely utilized in electronic devices and energy systems. Improvement in thermal performance of PHPs will lead to higher heat transfer capacity and enhancement in the efficiency of systems which PHPs are applied. In this study, an experimental investigation was performed on the thermal performance of a pulsating heat pipe by applying graphene oxide nanofluid as working fluid. Four concentrations of graphene oxide (0.25, 0.5, 1, and 1.5 g/lit) in water as base fluid were used in the PHP. Results indicate that adding graphene oxide sheets increased thermal conductivity and viscidity of the base fluid. Moreover, utilizing graphene... 

    An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 131, Issue 2 , 2018 , Pages 1577-1586 ; 13886150 (ISSN) Pourfayaz, F ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
    Springer Netherlands  2018
    Abstract
    In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different... 

    Exergy analysis of a flat plate solar collector in combination with heat pipe

    , Article International Journal of Environmental Research ; Vol. 8, Issue. 1 , 2014 , Pages 39-48 ; ISSN: 17356865 Kargarsharifabad, H ; Shafii, M. B ; Rahni, M. T ; Abbaspour, M ; Sharif University of Technology
    Abstract
    The use of solar collectors in combination with heat pipes is rapidly growing in recent years. Heat pipes, as heat transfer components, have undeniable advantages in comparison with other alternatives. The most important advantage is their high rate of heat transfer at minor temperature differences. Although there have been numerous studies on the heat analysis or first thermodynamic analysis of flat plate solar collectors in combination with heat pipes, the exergy analysis of these collectors is needed to be investigated. In this work, energy and exergy analysis of a flat plate solar collector with a heat pipe is conducted theoretically. Next, the exergy efficiency of pulsating heat pipe... 

    An integral type characterization of constant functions on metric-measure spaces

    , Article Journal of Mathematical Analysis and Applications ; Volume 385, Issue 1 , January , 2012 , Pages 194-201 ; 0022247X (ISSN) Ranjbar Motlagh, A ; Sharif University of Technology
    2012
    Abstract
    The main purpose of this article is to generalize a characterization of constant functions to the context of metric-measure spaces. In fact, we approximate a measurable function, in terms of a certain integrability condition, by Lipschitz functions. Then, similar to Brezis (2002) [2], we establish a necessary and sufficient condition in order that any measurable function which satisfies an integrability condition to be constant a.e. Also, we provide a different proof for the main result of Pietruska-Pałuba (2004) [7] in the setting of Dirichlet forms  

    Heat trap detection in the stator bar of large turbogenerators during the fault of cooling water channels blockage

    , Article IECON Proceedings (Industrial Electronics Conference), 24 October 2016 through 27 October 2016 ; 2016 , Pages 1501-1506 ; 9781509034741 (ISBN) Kaboli, S ; Oraee, H ; Sharif University of Technology
    IEEE Computer Society  2016
    Abstract
    Cooling water is used to remove the heat from stator bar of large turbogenerators and prevent additional temperature rise. Blockage of these channels leads to heat traps along the stator bar and its temperature failure. In addition, transposition of strands in a bar causes accumulation of heat in some parts of stator bar because of non-uniform arrangement of cooling channels especially when some of channels are blocked. In this paper, effect of cooling water channels blockage is studied using a precise thermal model. It is shown that such heat traps cause additional temperature rise in stator bars and this phenomenon can not be detected by thermal sensors of turbogenerator. Laboratory and... 

    Correlations in quantum thermodynamics: Heat, work, and entropy production

    , Article Scientific Reports ; Volume 6 , 2016 ; 20452322 (ISSN) Alipour, S ; Benatti, F ; Bakhshinezhad, F ; Marcantoni, S ; Rezakhani, A. T ; Sharif University of Technology
    Nature Publishing Group  2016
    Abstract
    We provide a characterization of energy in the form of exchanged heat and work between two interacting constituents of a closed, bipartite, correlated quantum system. By defining a binding energy we derive a consistent quantum formulation of the first law of thermodynamics, in which the role of correlations becomes evident, and this formulation reduces to the standard classical picture in relevant systems. We next discuss the emergence of the second law of thermodynamics under certain-but fairly general-conditions such as the Markovian assumption. We illustrate the role of correlations and interactions in thermodynamics through two examples  

    Experimental investigation of a solar still equipped with an external heat storage system using phase change materials and heat pipes

    , Article Desalination ; Volume 409 , 2017 , Pages 128-135 ; 00119164 (ISSN) Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    In this study, a novel idea of storing the latent heat of condensing vapor in solar stills by means of phase change materials (PCMs) as a thermal storage is experimentally investigated. During the daytime, the generated water vapor by the solar energy, is conducted to an external condenser filled with PCM to be condensed. The wasted latent heat is absorbed by PCM and thereby stored. It is worth noting that there is no direct contact between the saline water and the PCM, therefore, the solar energy is not directly stored in the PCM. In the evening, the energy stored in the PCM is transferred as heat to the saline water by heat pipes and enables the desalination process to continue. Several... 

    An experimental investigation and optimization of screen mesh heat pipes for low-mid temperature applications

    , Article Experimental Thermal and Fluid Science ; Volume 84 , 2017 , Pages 120-133 ; 08941777 (ISSN) Jafari, D ; Shamsi, H ; Filippeschi, S ; Di Marco, P ; Franco, A ; Sharif University of Technology
    Abstract
    The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model couples heat conduction in the wall with both liquid flow in the wick and vapor flow in the core. Experimental analysis is developed to evaluate the influence of operating parameters (the orientation and the cooling temperature) as well as the evaporator section length on the performance of the HP. Furthermore, a modeling approach to optimize the HP performance from a thermal point of view is... 

    Experimental investigation of the thermal characteristics of single-turn pulsating heat pipes with an extra branch

    , Article International Journal of Thermal Sciences ; Volume 134 , 2018 , Pages 258-268 ; 12900729 (ISSN) Sedighi, E ; Amarloo, A ; Shafii, M. B ; Sharif University of Technology
    Elsevier Masson SAS  2018
    Abstract
    In addition to some approaches such as changing the working fluid or number of turns in a pulsating heat pipe (PHP), geometrical changes are also appealing for enhancing the thermal performance of this type of heat pipes. The main idea of this investigation is to increase heat transfer rate by increasing flow circulation of working fluid. By placing an additional branch in the evaporator section, a secondary bubble pump was created which improved the circulation of fluid inside PHP. In order to investigate the impact of this additional branch, two similar one-turn copper heat pipes were fabricated. One of them was the conventional PHP and the other had an additional branch and is named... 

    A review on pulsating heat pipes: from solar to cryogenic applications

    , Article Applied Energy ; Volume 222 , 15 July , 2018 , Pages 475-484 ; 03062619 (ISSN) Alhuyi Nazari, M ; Ahmadi, M. H ; Ghasempour, R ; Behshad Shafii, M ; Mahian, O ; Kalogirou, S ; Wongwises, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Pulsating heat pipes (PHPs) are compact cooling equipment used for various applications. This type of heat pipes can be used in renewable energy systems, cooling electronic devices, heat recovery systems and many other applications. Since PHPs have superior thermal performance, by applying them in energy systems enhance their efficiency. In addition, PHPs are a reliable medium for cooling various devices which have high heat flux. In this study, various works conducted on the applications of PHPs are reviewed and analyzed. It is concluded that PHPs are efficient and reliable devices for utilization in various energy systems. Moreover, at very low temperatures, such as cryogenic applications,... 

    Experimental studies of heat transfer of air in a double-pipe helical heat exchanger

    , Article Applied Thermal Engineering ; Volume 133 , 2018 , Pages 276-282 ; 13594311 (ISSN) Majidi, D ; Alighardashi, H ; Farhadi, F ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    The overall heat transfer coefficient (OHTC) of air in a double-pipe helical heat exchanger is studied and experimentally investigated. In order to increase the rate of heat transfer in the annulus section, a copper-wire fin is soldered on the outside area of the internal tube. The literature correlations’ results are presented against the experimental data by changing mass flow rate and temperature, and consequently changing the Reynolds number. Further, a new method is suggested to obtain the heat transfer coefficients of double-pipe helical heat exchangers for the internal tube and the annulus section by combining two of the previously proposed approaches and making subsequent... 

    A review of quantum thermodynamics

    , Article Iranian Journal of Physics Research ; Volume 19, Issue 3 , 2019 , Pages 489-521 ; 16826957 (ISSN) Shahidani, S ; Rezakhani, A ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    In this article, we present a brief and elementary review of quantum thermodynamics and its achievements and challenges. This review includes an introduction to some fundamental concepts such as internal energy, heat, work, entropy, entropy production, thermal equilibrium, second law of quantum thermodynamics, relation between thermodynamics and information theory, as well as a discussion of how quantum effects such as entanglement and correlations affect performance of quantum heat engines. © 2019 by the authors. Licensee MDPI, Basel, Switzerland