Search for: cooling-systems
Total 120 records
Optimization and design of cooling systems using a hybrid neural network and genetic algorithm methodology, Article Eighth International Conference on Advanced Computational Methods in Heat Transfer, HEAT TRANSFER VIII, Lisbon, 24 March 2004 through 25 March 2004 ; Volume 5 , 2004 , Pages 333-343 ; 14626063 (ISSN) ; Fardadi, M ; Bahoush, R ; Sharif University of Technology
In this paper a novel method for the design and optimization of cooling systems is presented. The numerical solution of free convection from a heated horizontal cylinder confined between adiabatic walls obtained from a finite element solver is used to propose a non-linear heat transfer model of GMDH type approach. In the context of GMDH model, three different methods depending on the structure of neural network are implemented. The system of orthogonal equations is solved using a SVD scheme. The coefficients of second order polynomials are computed and their behavior is discussed. In addition, to demonstrate the performance of the predicted model, the numerical data are divided into trained...
Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 97-103 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Mozafari, A. A ; Sharifian, L ; Sharif University of Technology
American Society of Mechanical Engineers 2004
Cell temperature in fuel cells is an important parameter which highly affects fuel cell stack efficiency. A suitable cooling system should satisfy an acceptable temperature range. In this research a relevant cooling system for a specified PEM fuel cell stack has been proposed complying with the criteria and cooling requirements of the fuel cell. The effect of various parameters on the entropy generation and temperature distribution in the cooling plates are surveyed. The number of cooling plates, the number of channels in each cooling plate and the channel width is determined. Two flow regimes namely laminar and turbulent flows of the cooling fluid in channels are analyzed and a design...
Article ASHRAE Journal ; Volume 49, Issue 1 , 2007 , Pages 44-49 ; 00012491 (ISSN) ; Vazirifard, S ; Sharif University of Technology
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 2007
HVAC systems that use heat-regenerated desiccant wheels to remove moisture can be energy-efficient alternatives to traditional systems. Site-specific conditions and differing application requirements must be understood and quantified before desiccant-assisted hybrid systems can be justified on economic grounds. Although a detailed analysis is generally required, a few key variables drive costs and benefits. When two or more of these key variables favor a hybrid system over a conventional system, then a detailed analysis of the benefits vs. costs of a hybrid desiccant system is appropriate
Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 45 , 2005 , Pages 507-515 ; 10716947 (ISSN) ; Zomorodian, R ; Ghofrani, M. B ; Sharif University of Technology
Gas turbine performances are directly related to site conditions. The use of gas turbines in combined gas-steam power plants, also applied to cogeneration, increases such dependence. In recent years, inlet air cooling systems have been introduced to control air temperature at compressor inlet, resulting in an increase in plant power and efficiency. In this paper, the dependence of outside conditions for a simple gas turbine and a combined cycle plant is studied, using absorption chiller as inlet air cooling system. We used, as case study, a simple plant equipped with one frame E gas turbine and a combined cycle with a two pressure level heat recovery steam generator (HRSG). It was found that...
Article 23rd International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems, 14 June 2010 through 17 June 2010 ; Volume 4 , 2010 , Pages 203-210 ; 9781456303181 (ISBN) ; Karimi, M ; Ahmadi, P ; Ecole Polytechnique Federale de Lausanne; Schweizerische Eidgenossenschaft ; Sharif University of Technology
Aabo Akademi University
The gas turbine (GT) is known to feature low capital cost to power ratio, high flexibility, high reliability without complexity, short delivery time, early commissioning and commercial operation and fast starting-accelerating. Hence, researchers all over the world are working to increase the output power and efficiency of gas turbine cycle. One of the important techniques to increase the output power of such cycles is the compressor inlet air cooling method. The objective of this paper is to analysis the gas turbine cycle from both energy and exergy point of view. Thus, two important methods for increasing the output power, i.e. fog and media inlet air cooling systems are discussed....
Article Energies ; Volume 10, Issue 7 , 2017 ; 19961073 (ISSN) ; Bahadori, M. N ; Dehghani Sanij, A ; Nourbakhsh, A ; Sharif University of Technology
MDPI AG 2017
Wind towers or wind catchers, as passive cooling systems, can provide natural ventilation in buildings located in hot, arid regions. These natural cooling systems can provide thermal comfort for the building inhabitants throughout the warm months. In this paper, a modular design of a wind tower is introduced. The design, called a modular wind tower with wetted surfaces, was investigated experimentally and analytically. To determine the performance of the wind tower, air temperature, relative humidity (RH) and air velocity were measured at different points. Measurements were carried out when the wind speed was zero. The experimental results were compared with the analytical ones. The results...
Combined desiccant-ejector cooling system assisted by organic rankine cycle for zero-power cooling and dehumidification, Article International Conference on Climate Resilient Cities - Energy Efficiency and Renewables in the Digital Era 2019, CISBAT 2019, 4 September 2019 through 6 September 2019 ; Volume 1343, Issue 1 , 2019 ; 17426588 (ISSN) ; Rostamzadeh, H ; Khovalyg, D ; Scartezzini, J. L ; Smith, B ; Swiss Federal Office of Energy ; Sharif University of Technology
Institute of Physics Publishing 2019
This study presents a novel set-up for desiccant-based cooling and dehumidification systems. In this cycle, a solid desiccant and conventional combined cooling and power (CCP) systems, based on the ejector refrigeration cycle (ERC) and the organic Rankine cycle (ORC), are integrated to provide dehumidification and cooling, simultaneously. The ERC is integrated with the ORC for devising a self-powered design which has not been done until now. The proposed integrated system is useful for replacing the peak electricity demand with the heat demand, decreasing the pressure on the power grid in humid areas. Dynamic hourly simulation of the proposed system as well as a conventional system were...
Article Applied Thermal Engineering ; Volume 151 , 2019 , Pages 26-37 ; 13594311 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd 2019
Ejector refrigeration system has many advantages over traditional compressor-based systems, including: simplicity, low installation and operating costs and the ability to operate with low-grade thermal energy sources. However, its main drawbacks are low Coefficient of Performance (COP) and failure at high ambient temperatures. To overcome these problems, a novel methodology for designing a multi-ejector refrigeration system is proposed. This system utilizes a parallel array of ejectors instead of one ejector. Therefore, the system can continuously operate at its optimum efficiency. Each ejector works within a specific range of condensing pressures. The condenser pressure governs the...
Modification of TTL-1 Thermo hydraulic Test Loop for Study of SB-LOCA in Low Pressure and Temperature Conditions
Sharif University of Technology
In this thesis, TTL-1 thermo hydraulic test loop which was constructed in the Nuclear Science and Technology Research Institute (NSTRI) has been modified. These modifications include changing core section from one fuel rod to a fuel assembly with triangular arrangement, adding a pressurizer on the hot leg of loop, an accumulator, LOCA valve and installation of new sensors for upgrading of data acquisition system and modification of loop piping design. By these modifications, we will able to study different accidents such as LOHA, LOFA and LOCA and validate nuclear thermo hydraulic codes. Moreover, this new thermo hydraulic test loop (TTL-2) has been modeled by RELAP5/MOD3.2 in order to...
Article Energy ; Volume 193 , 15 February , 2020 ; Aligolzadeh, F ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd 2020
Ground-coupled ejector cooling (GCEC) systems have been introduced to solve the air-coupled ejector cooling (ACEC) systems problems. To date, no research study is dedicated to compare the GCEC and the ACEC systems and determine the relative payback period of the GCEC system vs. the ACEC system. Furthermore, almost all the previous studies simulated the GCEC systems by elementary models. Therefore, a comprehensive simulation is conducted to assess the techno-economic performance of a GCEC system. The model consists of the ejector and the borehole heat exchanger submodels. The first section of the results compares the ACEC system and the GCEC system during a cooling season. The seasonal...
Article Energy and Buildings ; Volume 38, Issue 10 , 2006 , Pages 1230-1239 ; 03787788 (ISSN) ; van Paassen, D ; Saidi, M. H ; Sharif University of Technology
This paper presents the modeling of a desiccant wheel used for dehumidifying the ventilation air of an air-conditioning system. The simulation of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out with MATLAB Simulink. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. The solutions of the simulation at different conditions used in air dehumidifier have been investigated according to the previous published studies. The model is validated through comparison the simulated results with...
Article 2005 ASME Fluids Engineering Division Summer Conference, Houston, TX, 19 June 2005 through 23 June 2005 ; Volume 1 PART B , 2005 , Pages 1049-1054 ; 0791841987 (ISBN); 9780791841983 (ISBN) ; Van Paassen, D ; Saidi, M. H ; Sharif University of Technology
In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. An approach to compare the solutions for different conditions used in air dehumidifier has been investigated according to the previous published studies. Comparing the simulated results with the published actual values of an experimental work substantiates the validity of model. The model accuracy with respect to the key...
Article 3rd International Conference on Fuel Cell Science, Engineering, and Technology, 2005, Ypsilanti, MI, 23 May 2005 through 25 May 2005 ; 2005 , Pages 441-448 ; 0791837645 (ISBN); 9780791837641 (ISBN) ; Saidi, M. H ; Sharif University of Technology
American Society of Mechanical Engineers 2005
Cooling system is essential for high power fuel cells to maintain cells temperature in an acceptable limit. In this paper a suitable cooling system for the PEM fuel cell has been designed and optimized. The design includes the number of the cooling plates, the proper circuit of the cooling channels in the plates, the channel dimensions, the flow rate of the cooling fluid and its temperature. The optimization technique is minimization of the entropy generation through the cooling plates. The design of the cooling channels and plates is such that the plate temperature doesn't exceed from a desired temperature and the temperature variation in the plate becomes minimized. In this design, the...
A new approach to exergy analyses of a hybrid desiccant cooling system compares to a vapor compression system, Article Applied Mechanics and Materials, 29 July 2011 through 31 July 2011 ; Volume 110-116 , July , 2012 , Pages 2163-2169 ; 16609336 (ISSN) ; 9783037852620 (ISBN) ; Yau, Y. H ; Mahlia, T. M. I ; Saidi, M. H ; Sharif University of Technology
In the recent researches HVAC with a based desiccant dehumidifier with a low ambient impact is more efficient in comparison to the traditional systems. Hybrid desiccant cooling systems can be used to control indoor air quality in buildings. This paper presents an integrated energy, entropy and exergy analysis of a hybrid desiccant cooling system compare to a compression system based on first and second laws of thermodynamic. The main objective is the use of a method called exergy costing applied to a conventional compression system that has been chosen to provide the proper conditioned air for a building in hot and humid condition. By applying the same method for the equivalent hybrid...
M.Sc. Thesis Sharif University of Technology ; Saboohi, Yadollah ; ShafiiShafii, Mohammad Behshad
The Engine of a vehicle is an energy conversion system, where specific chemical energy is converted in to heat in a combustion chamber. In order to reduce thermal tension in the cylandr, part of heat is removed with the help of circulating water and it is dissipated in the radiator. As a result, part of input energy is wasted in to the atmosphere through cooling system in each cycle of engine. Heat recovery in the cooling system and preheating combustion air of fuel could enhance energy efficiency and it may contribute to fuel economy. Heat recovery may be realized with the help of heat pipes. Heat pipes may be utilized for heat recovery and preheating fuel or air whichare inlet to the...
M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan ; Hakaki Fard, Ali
Nowadays, according to environmental issues and fuel economy in internal combustion engines, the tendency to use of electrical and hybrid-electrical propulsions has become more than the past. On the other hand, still there are some problems like distance and charge time in electrical propulsions. Among them there are Hybrid-electric propulsions that have the benefits of two other propulsions. These propulsions are classified into three categories: series, parallel and series-parallel.Propulsion hybridization will change the cooling system. Internal combustion engine, electric motors, inverter and batteries operate at different temperature levels. So more than one cooling circuit with its own...
Employing coupled cavities to increase the cooling rate of a levitated nanosphere in the resolved sideband regime, Article Journal of the Optical Society of America B: Optical Physics ; Volume 35, Issue 7 , 2018 , Pages 1563-1569 ; 07403224 (ISSN) ; Mehrany, K ; Sharif University of Technology
OSA - The Optical Society 2018
In this paper, we investigate cooling of a levitated nanosphere in a system of coupled cavities in the resolved sideband regime. Thanks to the presence of an extra resonance in the coupled cavity cooling system, the coupling strength can be maximized at the optimum detuning. In this fashion, the intracavity photon number is increased, and thereby the cooling rate is enhanced and the strong coupling regime is achieved without resorting to increased driving laser power. The underlying physics of the increased cooling efficiency in the system of coupled cavities in the resolved sideband regime proposed here and that of the already reported system of coupled cavities in the unresolved sideband...
Article Heat Transfer Engineering ; Volume 39, Issue 2 , 2018 , Pages 180-193 ; 01457632 (ISSN) ; Sharif University of Technology
Taylor and Francis Ltd 2018
An optimal performance film cooling implies a high cooling effectiveness along with a wide surface cooling coverage. During the past decades, film cooling effectiveness has been well defined with a specific formula to evaluate the quality of a cooling system. However, despite numerous research on film cooling, there is still no explicit parameter to quantify how well a coolant film is spread over a hot surface. This work introduces a new coefficient namely cooling uniformity coefficient (CUC) to evaluate how well a coolant film is spread over a surface that is being cooled. Four different cases at two blowing ratios of 0.5 and 1.5 are studied. Three cases are ordinary single jets with...
Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 355-362 ; 0791847608 (ISBN); 9780791847602 (ISBN) ; Saidi, M. H ; Zageneh Kazemi, P ; Sharif University of Technology
American Society of Mechanical Engineers 2006
Present investigation analyzes the issue of entropy generation in a uniformly heated microchannel heat sink (MCHS). Analytical approach used to solve forced convection problem across MCHS, is porous medium model based on modified Darcy equation for fluid flow and two-equation model for heat transfer between solid and fluid phases. Furthermore, closed form solution of velocity distribution is employed to capture z-direction velocity gradient of flow, which plays a salient role on entropy generation through fluid flow. Analytical expressions for total and thermal entropy generation number (stems from heat transfer), and Bejan number are derived and cast into dimensionless form using velocity...
Article Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science ; Volume 37, Issue 6 , 2006 , Pages 997-1005 ; 10735615 (ISSN) ; Halali, M ; Nusheh, M ; Sharif University of Technology
In this report the important factors affecting the levitation melting of nickel are discussed. The relationship between the temperature of a levitated sample to factors such as coil design, gas flow rate, power input, and sample weight are studied. Different coil designs were investigated and compared. It was found that for satisfactory sustained levitation melting, the sample weight, depending on the material, must be within a particular range. Furthermore, increasing the power input would result in a decrease in the droplet temperature; and increasing the weight of the sample results in an increase in the temperature. The flow rate of a cooling gas has a reverse relationship to the...