Sharif Digital Repository

Bi-evaporator electricity/cooling cogeneration systems can be a favorable addition to the integrated power plants since the generated cooling load should be addressed for different demands. More consequentially, taking advantage of such an integral set-up operated with highly reliable heat source such as biogas can be appreciable for nowadays industries. Regarding this demand, an innovative bi-evaporator electricity/cooling cogeneration system is introduced at first. Next, the suggested system is integrated with a gas turbine cycle fueled by biogas. In the subsequent part, the plausibility of the introduced integrated power plant is examined from first and second laws of thermodynamics (as... 

An innovative bi-evaporator electricity/cooling cogeneration system fueled by biogas is introduced. The plausibility of the introduced integrated power plant is examined from thermodynamic and economic vantage points. Later, single- and multi-objective optimization of the reckoned system are achieved by selecting appropriate parameters as decision variables and thermal and exergy efficiencies and total unit product cost (TUPC) of the system as objective functions. Four optimum modes of thermal efficiency optimum design (TEOD), exergy efficiency optimum design (EEOD), cost optimum design (COD), and multi-objective optimum design (MOOD) are selected for optimization and the attained results... 

Desiccant-based evaporative cooling systems are considered as an energy efficient alternative to conventional vapor compression systems in humid climates. A novel hybrid desiccant-based ejector cooling (hybrid DEC) system is here presented to utilize low grade heat. In order to evaluate the system performance under subtropical humid climates, a dynamic hourly simulation of the system is performed for a typical building in Sydney. The results indicate that the hybrid DEC system is able to provide comfort conditions in subtropical and humid climates. Hybrid DEC system has a significant higher coefficient of performance compared to the conventional vapor compression system resulting to 84%... 

A high-efficient method has been considered for simultaneously improving the hydrothermal and exergetic performance of heat exchangers. Two-phase Eulerian model is employed in a 3-D numerical study to precisely study the hydrothermal and entropic behaviors of Fe3O4/water ferrofluid, under the effect of a magnetic field inducer. The findings reveal that employing the magnetic field can improve the energetic and exergetic performance by generating a swirling flow in the heat exchanger. The pressure drop and entropy generation minimization are also achieved by the induced flow in comparison with other passive techniques due to the lack of any additional obstacle in the flow path. Results show... 

Compact heat exchangers as modern industrial devices are designed to improve heat recovery and saving energy processes in restricted spaces. In the current study, effect of a uniform external magnetic field with Fe3O4/water nanofluid for heat transfer enhancement of a fin-and-tube compact heat exchanger is numerically investigated. The obtained results are verified by the available experimental data to demonstrate accuracy of the present simulation. The results indicated that the local and average heat transfer coefficients increase around the tubes in the presence of an external magnetic field due to the vortex formation behind the tubes as well as the flow pattern alteration in the heat... 

A considerable amount of energy is lost in the parabolic trough solar collectors due to the poor capability of working fluid in full absorption of the concentrated solar irradiation across the receiver tube. A new hybrid method is recommended here to cover up such deficiency by simultaneously using a rotary absorber tube and magnetic field inducer with nanofluid. Results showed that the combination effects of the receiver rotation and the magnetic field improve the convection mechanism in the absorber and increase both energetic and exergetic performance of the collector. The study reveals that there is an optimal rotational speed in the each magnetic field intensity for different... 

Among different types of geothermal processing used in the energy conversion systems, flash-binary geothermal can be the best scenario for high-temperature geothermal sources. Reviewing the available literature it can be found that the flash-binary geothermal power plants have a great potential to be extended to trigeneration systems, nonetheless they have received less attention. In this regard, a new trigeneration system for freshwater, power, and cooling production is devised using a flash-binary geothermal heat source at 170°C. In this devised trigeneration system, a humidification-dehumidification (HDH) unit is used as a binary cycle. Another merit of the devised trigeneration system is... 

Despite the fact that humidification-dehumidification (HDH) desalination systems can be driven by various renewable or waste heat energies, many of the available renewable technologies are expensive in some parts of the globe. Hence, proposing and developing high-efficient mechanical-based HDH units can be an encouraging alternative which is more highlighted in recent investigations. In pursuance of this objective, three innovative mechanical-driven HDH units are simulated and the results are compared with each other. The simulated hybrid desalination system consists of a HDH unit and an ethane ejector expander transcritical refrigeration cycle (ethane-EETRC). The simulated hybrid systems... 

Anaerobic fermentation of crop straw/animal dug can be the most appropriate solution for biomass conversion into applicable renewable energy-based fuels. However, due to the imperfection matching between the biogas combustion process and energy conversion system, a painstakingly design procedure is required to devise high-efficient energy system for capturing biogas efficiently. For this aim, a new trigeneration system driven by biogas is devised for electricity, refrigeration, and potable freshwater generation. The devised system encompasses a gas turbine (GT) cycle, a new cooling/electricity cogeneration system based on organic Rankine cycle (ORC) and ejector cooling cycle (ECC), and a... 

Flat plate solar collectors lose a massive part of heat accumulated near the contact region because of the poor thermal characteristics of the working fluid. A new cost-effective design is numerically studied to cover up such deficiency by equipping the flat plate collector with revolutionary tubes and magnetic field inducer to affect Fe3O4/water working nanofluid in the collector tubes. Results substantiate that each of the applied rotary tubes and magnetic field inducer improves the convection mechanism in the tubes by circulating the flow inside the tubes and saves more of available solar energy. Results reveal that 27.8% and 10.44% of lost energy are restored in the solar collector... 

Flat plate solar collectors waste a massive part of the heat accumulated near the contact region, mainly due to poor thermal characteristics of working fluid. The demanding power for pumping the flow through the pipes seems a permanent concern in solar collectors. Also, active methods seem not to be applicable in such systems due to the external energy requirement and cost associated with it. An innovative and simple technique is considered here to eliminate such deficiencies all at once by equipping the flat plate collector with rotary absorber pipes and Fe3O4/water nanofluid. Results indicate that the applied method improves the convection mechanism in each pipe by mixing the accumulated... 

A considerable amount of energy is lost in the parabolic trough solar collectors due to the poor capability of working fluid in full absorption of the concentrated solar irradiation across the receiver tube. A new hybrid method is recommended here to cover up such deficiency by simultaneously using a rotary absorber tube and magnetic field inducer with nanofluid. Results showed that the combination effects of the receiver rotation and the magnetic field improve the convection mechanism in the absorber and increase both energetic and exergetic performance of the collector. The study reveals that there is an optimal rotational speed in the each magnetic field intensity for different... 

Various methods are devised to capture renewable energy or waste heat from different sectors, where among all, waste heat capturing from the generator of a wind turbine through the cooling process for freshwater and cooling production is paid less attention in Iran, in spite of the fact that many wind farms in Iran are in hot and humid regions and the residents nearby the farms desperately need freshwater and cooling load. To surmount this problem, waste heat extraction from a wind turbine (Enercon 70 Model) for freshwater and cooling production is proposed in this study. Instead of dissipating this thermal energy of the wind turbine into the environment, it can be used for freshwater and... 

Purpose: The purpose of this paper is to derive a closed-form expression for the steady-state availability of a cold standby repairable k-out-of-n system. This makes the availability calculation much easier and accurate. Design/methodology/approach: Assuming exponential distributions for system failure and repair, the Markov method is employed to derive the formula. Findings: The proposed formula establishes an easier and faster venue and provides accurate steady-state availability. Research limitations/implications: The formula is valid for the case when the probability density function of the component failure and the repair is exponential. Originality/value: The Markov method has never... 

This article works with performance improvement of the conventional combined cooling/power (CCP) cycles to augment energy and exergy efficiencies of the previous systems. For this target, a conceptual configuration of cascade ejector refrigeration system (CERS) is proposed and is joined with organic Rankine cycle (ORC) to generate power and cooling outputs. The introduced CCP system can generate cooling load at two various temperatures for freezing and air-conditioning usages. For power sub-cycle, basic ORC and recuperative ORC with turbine bleeding are selected as topping cycles. Thermodynamic and exergoeconomic assessments of the cycles are done, leading to provision of the working... 

A precise heat transfer simulation of a three-dimensional impinging jet porous heat sink is presented and is analyzed from thermodynamics vantage point under local thermal non-equilibrium condition. To increase the computational efficiency of the analysis, pore-scale modeling based on lattice Boltzmann method (LBM) is used inside the porous media (at a meso-scale), whilst finite volume method (FVM) is employed around it (at a macro-scale). The effects of the Reynolds number, porous layer thickness, solid/fluid thermal conductivity ratio, and porosity on the critical heat transfer and entropy generation parameters are investigated. Additionally, the relations between viscous entropy... 

In the present study, the effects of rotary tubes and magnetic-induced nanofluid on heat transfer characteristics of a compact heat exchanger are individually investigated. Two-phase Eulerian model is employed to predict the hydrothermal and entropic characteristics of Fe3O4/water ferrofluid in the heat exchanger. Results indicate that utilizing each rotary tubes and magnetic field method can improve the energy and exergy efficiencies of the compact heat exchanger under specific circumstances by forming different types of secondary flow. It is found that employing each method individually can increase the maximum heat transfer rate by more than 60%. In comparison with methods like passive... 

Multigeneration systems (MGSs) driven by renewable sources are proved as cutting-edge technologies for multiple productions purposes to curb greenhouse gas emissions. With this regard, a novel geothermal-based MGS is proposed to produce multiple commodities of cooling, heating, power, and hydrogen, simultaneously, using liquefied natural gas (LNG) as cold energy recovery. The system is composed of an organic Rankine cycle (ORC), an ejector refrigeration cycle (ERC), an LNG power generation system, and a proton exchange membrane (PEM) electrolyzer system. To demonstrate the feasibility of the proposed MGS, energy, exergy, and exergoeconomic analysis are employed as the most effective tools... 

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...