scholarly journals Numerical Analysis of the Influence of Basic Operating Parameters on the Performance Characteristics of Solar-Driven Ejector Cooling

2020 ◽  
Author(s):  
Branislav Petrović ◽  
◽  
Milan Gojak ◽  
Đorđe Kozić
Keyword(s):  
Renewable Energy Sources ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Adsorption Refrigeration ◽  
Entrainment Ratio ◽  
Cooling Systems ◽  
Basic Operating ◽  
Influence Of Temperature On ◽  
Temperature Ranges ◽  
Low Efficiency

Researchers are becoming growingly interested in the development of solar-driven ejector cooling systems, primarily due to their potential to be used as renewable energy sources. Absorption and adsorption refrigeration systems not only involve considerable investment but are also much less reliable than the ejector refrigeration sys-tems, which do not contain any movable parts. In adition, ejector refrigeration has the advantage of low capital cost, simple design, reliable operation, long lifespan and almost no maintance. The only weakness of this system is the low efficiency and its intolerance to deviations from design operation condition.The paper develops a mathematical mod-el with an algorithm which is based on the laws of thermodynamics and the principles of mass and momentum conser-vation. Based on the obtained model, the influence of temperature on the basic system parameters for two working fluids, R134a and R290, is presented. The working fluid temperature ranges are 80-100°C in the generator, 5-15°C in the evaporator and 33-40°C in the condenser. The important performace indicators are the characteristic ejector area ratio Ar (as a geometrical ejector parameter), ejector entrainment ratio, ejector efficiency and the COP. The results indicate that ejector geometry and working fluid type have a major impact on the ejector cooling system’s performance.

scholarly journals Process Heat Generation Potential from Solar Concentration Technologies in Latin America: The Case of Argentina

2017 ◽  
Author(s):  
Isidoro Lillo ◽  
Elena Pérez ◽  
Sara Moreno ◽  
Manuel Silva
Keyword(s):  
Latin America ◽  
Ghg Emissions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Cost Of Energy ◽  
Temperature Ranges ◽  
The One ◽  
Solar Resource ◽  
Parabolic Collector ◽  
Thermal Level

This paper evaluates the potential of solar concentration technologies—compound parabolic collector (CPC), linear Fresnel collector (LFC) and parabolic trough collector (PTC)—as an alternative to conventional sources of energy for industrial processes in Latin America, where high levels of solar radiation and isolated areas without energy supply exist. The analysis is addressed from energy, economic and environmental perspective. A specific application for Argentina in which fourteen locations are analyzed is considered. Results show that solar concentration technologies can be an economically and environmentally viable alternative. Levelized cost of energy (LCOE) ranges between 2.5 and 16.9 c€/kWh/m2 and greenhouse gas (GHG) emissions avoided range between 33 and 348 kgCO2/(m2·year). CPC technology stands out as the most recommendable technology when the working fluid temperature ranges from 373K to 423K. As the working fluid temperature increases the differences between the LCOE values of the CPC and LFC technologies decrease. When 523K is reached LFC technology is the one which presents the lowest LCOE values for all analyzed sites, while the LCOE values of PTC technology are close to CPC technology values. Results show that solar concentration technologies have reached economic and environmental competitiveness levels under certain scenarios, mainly linked to solar resource available, thermal level requirements and solar technology cost.

scholarly journals Experimental Study on Activated Carbon-MIL-101(Cr) Composites for Ethanol Vapor Adsorption

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3811
Author(s):  
Zhongbao Liu ◽  
Jiayang Gao ◽  
Xin Qi ◽  
Zhi Zhao ◽  
Han Sun
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ethanol Vapor ◽  
Future Application ◽  
Working Fluid ◽  
Relative Pressure ◽  
Adsorption Refrigeration ◽  
Vapor Adsorption

In this study, the hydrothermal method was used to synthesize MIL-101(Cr), and activated carbon (AC) with different content was incorporated in to MIL-101(Cr), thereby obtaining AC-MIL-101(Cr) composite material with a huge specific surface area. The physical properties of MIL-101(Cr) and AC-MIL-101(Cr) were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), nitrogen adsorption and desorption and specific surface area testing, and ethanol vapor adsorption performance testing. The results show that with the increase of activated carbon content, the thermal stability of AC-MIL-101(Cr) is improved. Compared with the pure sample, the BET specific surface area and pore volume of AC-MIL-101(Cr) have increased; In the relative pressure range of 0–0.4, the saturated adsorption capacity of AC-MIL-101(Cr) to ethanol vapor decreases slightly. It is lower than MIL-101(Cr), but its adsorption rate is improved. Therefore, AC-MIL-101(Cr)/ethanol vapor has a good application prospect in adsorption refrigeration systems. The exploration of AC-MIL-101(Cr) composite materials in this paper provides a reference for the future application of carbon-based/MOFS composite adsorbent/ethanol vapor working fluid in adsorption refrigeration.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

Development of an Innovative Code for the Design of Different Parabolic Trough Solar Fields

2009 ◽  
Author(s):  
Ennio Macchi ◽  
Giampaolo Manzolini ◽  
Paolo Silva
Keyword(s):  
Solar Energy ◽  
Energy Demand ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Parabolic Trough ◽  
High Solar Radiation ◽  
Power Block ◽  
The Usa ◽  
Solar Field ◽  
Steam Cycle

The role of renewable energies and in particular solar energy could be fundamental in future scenarios of worldwide increase of energy demand: thermodynamic solar energy can play an important role in country with high solar radiation. This paper discusses the development and testing of an innovative code for the prediction of thermodynamic performances at nominal conditions and the estimation of costs of the whole plant, for different parabolic trough solar fields. The code allows a preliminary design of the solar field lay-out, the sizing of the main components of the plant and the optimization of the steam cycle. The code, named PATTO (PArabolic Trough Thermodynamic Optimization), allows to separately calculate the thermal efficiency of (i) parabolic trough systems in commerce as well as (ii) combination of components of various commercial systems, in order to exploit different technology solutions: combination of mirrors, receivers and supports. Using the selected parabolic troughs, the plant configuration is then completed by connecting pipes, heat exchangers, the steam cycle, and storage tanks. The code is also flexible in terms of working fluid, temperature and pressure range. Regarding the power block, a conventional steam cycle with super-heater and re-heater sections and up to seven regenerative bleedings is adopted. It is possible to use also simpler configuration as without re-heater or with less regenerative bleedings. Moreover, thanks to simple or sophisticated economic correlations depending on available data, the code calculates the overall investment cost for the considered solar field and the power block. The code performs steady state analysis at nominal conditions, while future developments are planned regarding part load analysis and transient simulations. The model is tested towards real applications and reference values found in literature; in particular, focusing on SEGS VI plant in the USA. Detailed results showing code potentiality, are presented in terms of solar field and power block energy balances, plant auxiliaries, piping and economic analysis.

scholarly journals Experimental and Theoretical Analysis of a Linear Focus CPV/T System for Cogeneration Purposes

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2960 ◽  
Author(s):  
Carlo Renno
Keyword(s):  
Focal Length ◽  
Concentration Field ◽  
Operating Conditions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Environment Temperature ◽  
Temperature Levels ◽  
T System

The knowledge of the actual energy performances of a concentrating photovoltaic and thermal (CPV/T) system with a linear focus optics, allows to evaluate the possibility of adopting this type of system for cogeneration purposes. Hence, the main aim of this paper is the design, realization, setting and modeling of a linear focus CPV/T system in the high concentration field. An experimental linear focus CPV/T plant was created in order to determine its electrical and thermal performance under different working conditions in terms of environment temperature, sunny and cloudy conditions, focal length, etc. Moreover, a theoretical model of the linear focus CPV/T system was also studied. This model evaluates the temperatures of the working fluid that flows in the cooling circuit of the CPV/T system under several operating conditions. The temperatures of the triple junction (TJ) cells, experimentally evaluated referring to different solar radiation and atmospheric conditions, were considered as the input data for the model. The values of the fluid temperature, theoretically and experimentally determined, were thus compared with good agreement. The electrical production of the CPV/T system depends generally on the TJ cell characteristics and the concentration factor, while the thermal production is above all linked to the system configuration and the direct normal irradiance (DNI) values. Hence, in this paper the electric power obtained by the linear-focus CPV/T system was evaluated referring to the cogeneration applications, and it was verified if the TJ cell and the cooling fluid reach adequate temperature levels in this type of system, in order to match the electrical and the thermal loads of a user.

A 3-D Model Simulation of High Temperature Solar Cavity Receiver

2017 ◽  
Author(s):  
Huayi Feng ◽  
Yanping Zhang ◽  
Chongzhe Zou
Keyword(s):  
Heat Transfer ◽  
Radiation Intensity ◽  
Large Scale ◽  
Model Simulation ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Fluid Temperature ◽  
Heat Transfer Efficiency ◽  
Direct Normal Irradiance

In this paper, a 3-D numerical model is proposed to investigate the capability of generating high operating temperature for a modified solar cavity receiver in large-scale dish Stirling system. The proposed model aims to evaluate the influence of radiation intensity on the cavity receiver performance. The properties of the heat transfer fluid in the pipe and heat transfer losses of the receiver are investigated by varying the direct normal irradiance from 400W/m2 to 1000W/m2. The temperature of heat transfer fluid, as well as the effect of radiation intensity on the heat transfer losses have been critically presented and discussed. The simulation results reveal that the heat transfer fluid temperature and thermal efficiency of the receiver are significantly influenced by different radiation flux. With the increase of radiation intensity, the efficiency of the receiver will firstly increase, then drops after reaching the highest point. The outlet working fluid temperature of the pipe will be increased consistently. The results of the simulations show that the designed cylindrical receiver used in dish Stirling system is capable to achieve the targeted outlet temperature and heat transfer efficiency, with an acceptable pressure drop.

scholarly journals A Novel Method for Designing Fifth-Generation District Heating and Cooling Systems

2021 ◽  
Vol 246 ◽  
pp. 09001
Author(s):  
Marwan Abugabbara ◽  
Jonas Lindhe
Keyword(s):  
Analytical Solution ◽  
District Heating ◽  
Innovative Technology ◽  
Complete Agreement ◽  
Fluid Temperature ◽  
Existing Buildings ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Fifth Generation ◽  
Novel Method

District heating and cooling systems have been undergoing continuous development and have now reached the fifth-generation. In this innovative technology, connected buildings share local excess energy that otherwise would be wasted, which consequently reduces primary energy demands and carbon emissions. To date, the issue of implementing fifth-generation district systems on existing buildings has received scant attention, and our research addresses this challenging gap by proposing a novel method for designing these systems. We first explain the possible thermal interactions between connected buildings, and then present an analytical solution for the network energy balance, pipe design, and the prediction of fluid temperature under a fixed temperature difference control strategy. The analytical solution was validated against numerical simulations performed on 11 existing buildings located in Lund, Sweden using Modelica models. A diversity index metric between heating and cooling demands was also included in these models to assess the efficiency of the district system in the building cluster. The results from the analytical and numerical solutions were in complete agreement since Modelica is an equation-based modelling language. The developed models pave the way towards future investigations of different temperature control strategies and new business models that arise from the shift to the fifth-generation.

Thermodynamic Analysis of a Novel Ammonia-Water Cogeneration System for Maritime Diesel Engines

2020 ◽  
Author(s):  
Ziyang Cheng ◽  
Yaxiong Wang ◽  
Qingxuan Sun ◽  
Jiangfeng Wang ◽  
Pan Zhao ◽  
...  
Keyword(s):  
Power Output ◽  
Thermal Efficiency ◽  
System Performance ◽  
Mass Fraction ◽  
Ammonia Concentration ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Kalina Cycle ◽  
Ammonia Water ◽  
Cogeneration System

Abstract This paper proposes a novel cogeneration system based on Kalina cycle and absorption refrigeration system to meet the design requirements of China State Shipbuilding Corporation, which is efficiently satisfy the power and cooling demands of a maritime ship at the same time. Unlike most of the combined systems, this cogeneration system is highly coupled and realizes cogeneration without increasing the system complexity too much. The basic ammonia mass fraction of this novel system is increased, so that the ammonia concentration of ammonia-water steam from the separator can be higher, which contributes to lower refrigerating temperature and thus less heat loss in the distillation process. In addition, higher ammonia concentration solution makes overheating easier, which improves the thermal efficiency. Moreover, the system has two recuperators to make further improvement of the thermal efficiency. Thermodynamic models are developed to investigate the system performance and parametric analysis is conducted to figure out the effects of including working fluid temperature at the outlet of the evaporator, working fluid temperature at superheater outlet, mass fraction of ammonia in basic solution, turbine inlet pressure, temperature of cooling water at the inlet of condensers and the refrigeration evaporation temperature on the system performance. Furthermore, the cogeneration system is optimized with genetic algorithm to obtain the best performance, which achieves 333.00kW of net power output, 28.83 kW of cooling capacity and 21.81% of thermal efficiency. Finally, the performance of the proposed system is compared with an optimized recuperative organic Rankine cycle (ORC) system and an optimized Kalina cycle system 34 (KCS34) using the same heat source. The results show that the thermal efficiency and power output of the novel cogeneration system is 3.89% and 1.05% higher than that of the recuperative ORC system and KCS34 system respectively.

Embedded Metamaterial Subframe Patch for Increased Power Output of Piezoelectric Energy Harvesters

2021 ◽  
pp. 1-9
Author(s):  
Saman Farhangdoust ◽  
Gary Georgeson ◽  
Jeong-Beom Ihn ◽  
Armin Mehrabi
Keyword(s):  
Energy Harvesting ◽  
Cantilever Beam ◽  
Renewable Energy Sources ◽  
Piezoelectric Element ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Harvesting Systems ◽  
Host Structure ◽  
Self Powered ◽  
Low Efficiency

Abstract These days, piezoelectric energy harvesting (PEH) is introduced as one of the clean and renewable energy sources for powering the self-powered sensors utilized for wireless condition monitoring of structures. However, low efficiency is the biggest drawback of the PEHs. This paper introduces an innovative embedded metamaterial subframe (MetaSub) patch as a practical solution to address the low throughput limitation of conventional PEHs whose host structure has already been constructed or installed. To evaluate the performance of the embedded MetaSub patch (EMSP), a cantilever beam is considered as the host structure in this study. The EMSP transfers the auxetic behavior to the piezoelectric element (PZT) wherever substituting a regular beam with an auxetic beam is either impracticable or suboptimal. The concept of the EMSP is numerically validated, and the COMSOL Multiphysics software was employed to investigate its performance when a cantilever beam is subjected to different amplitude and frequency. The FEM results demonstrate that the harvesting power in cases that use the EMSP can be amplified up to 5.5 times compared to a piezoelectric cantilever energy harvester without patch. This paper opens up a great potential of using EMSP for different types of energy harvesting systems in biomedical, acoustics, civil, electrical, aerospace, and mechanical engineering applications.

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