scholarly journals Assessment of the annual performance of solar collectors by means of the utilizability method

2020 ◽  
Vol 207 ◽  
pp. 02007
Author(s):  
Merima Zlateva
Keyword(s):  
Heat Transfer ◽  
Critical Value ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Solar Collectors ◽  
Different Temperatures ◽  
Evacuated Tube ◽  
Inclined Surface

This report presents some results from a comparative analysis of the long-term efficiency of flat-plate and evacuated tube solar collectors under different operating conditions. The analysis involves calculation of the daily utilizibility factor, which is defined as the fraction of total monthly solar radiation over an inclined surface that exceeds the critical value. The monthly values of the critical radiation and the daily utilizability factor for the solar collectors are determined under different climatic conditions and different temperatures of the heat transfer fluid. The obtained results are used to compare the annual performance of the solar collectors.

scholarly journals MEASUREMENT OF THE EFFICIENCY OF EVACUATED TUBE SOLAR COLLECTORS UNDER VARIOUS OPERATING CONDITIONS

2012 ◽  
Vol 7 (3) ◽  
pp. 114-130 ◽  
Author(s):  
S. E. Zubriski ◽  
K. J. Dick
Keyword(s):  
Environmental Conditions ◽  
Operating Conditions ◽  
Hot Water ◽  
Heat Transfer Fluid ◽  
Operating Efficiency ◽  
Space Heating ◽  
Solar Collectors ◽  
Auxiliary Equipment ◽  
Evacuated Tubes ◽  
Evacuated Tube

The operating efficiency of evacuated tubes themselves under varying environmental conditions and installation scenarios, independent of water and space heating auxiliary equipment, are not readily available values. Further, Manitoba specific data has not been established. The purpose of this research program was to measure the efficiency of evacuated tube solar collectors under various operating conditions including: the angle of inclination towards the incident solar radiation, heat transfer fluid flow rate, glazing installation, and number of evacuated tubes. The operating conditions and configurations were chosen to represent realistic or probable installation scenarios and environmental conditions. Furthermore, the research aimed to identify the suitability of evacuated tube solar collectors to each of the scenarios. These design values are of use for appropriate sizing of water or space heating systems, system configuration and optimization, and calculation of return on investment. The scope of the research project was limited to the efficiency of various configurations of a 32-tube panel, not the entire solar domestic hot water or space heating system. Thus, factors such as heat loss in the tubing, solar storage tank, and heat exchanger efficiency were not investigated. The findings indicated that efficiency varied by approximately 5% between the different collector configurations, as observed from the overlay graph of results. When the efficiency of a collector is considered within a system it is proposed that effectiveness may be a better measure of overall performance.

scholarly journals Nanofluids in Solar Thermal Collectors: Review and Limitations

2020 ◽  
Vol 41 (11) ◽  
Author(s):  
Ifeoluwa Wole-osho ◽  
Eric C. Okonkwo ◽  
Serkan Abbasoglu ◽  
Doga Kavaz
Keyword(s):  
Heat Transfer ◽  
Material Science ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Full Potential ◽  
Solar Collectors ◽  
Solar Thermal Collectors ◽  
Overall Efficiency ◽  
The Impact

Abstract Solar thermal collectors are systems that allow for the use of solar energy in thermal applications. These collectors utilize a heat transfer fluid to transport absorbed solar radiation to applications where they are needed. Scientists in a bid to improve the conversion efficiency of solar collectors have suggested different collector designs and improved collector materials. Over the last 25 years, the study of nanofluids and their applications have revolutionized material science, and nanotechnology has found applications in improving solar collector materials. This article reviews the impact of different nanomaterials on the efficiency of solar collectors. The study also outlines the limitations of applying nanofluids and discusses the long-term challenges of their application to solar collectors. Nanofluids have the potential to improve the overall efficiency of most solar collectors, however, the full potential of nanofluids in heat transfer applications cannot be completely achieved until some of the questions regarding hysteresis, stability, and the overall predictability of nanofluids are answered.

scholarly journals Modification of a Solar Thermal Collector to Promote Heat Transfer inside an Evacuated Tube Solar Thermal Absorber

2021 ◽  
Vol 11 (9) ◽  
pp. 4100
Author(s):  
Rasa Supankanok ◽  
Sukanpirom Sriwong ◽  
Phisan Ponpo ◽  
Wei Wu ◽  
Walairat Chandra-ambhorn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Medium Temperature ◽  
Change Behavior ◽  
Set Up ◽  
Evacuated Tube ◽  
Heating Medium

Evacuated-tube solar collector (ETSC) is developed to achieve high heating medium temperature. Heat transfer fluid contained inside a copper heat pipe directly affects the heating medium temperature. A 10 mol% of ethylene-glycol in water is the heat transfer fluid in this system. The purpose of this study is to modify inner structure of the evacuated tube for promoting heat transfer through aluminum fin to the copper heat pipe by inserting stainless-steel scrubbers in the evacuated tube to increase heat conduction surface area. The experiment is set up to measure the temperature of heat transfer fluid at a heat pipe tip which is a heat exchange area between heat transfer fluid and heating medium. The vapor/ liquid equilibrium (VLE) theory is applied to investigate phase change behavior of the heat transfer fluid. Mathematical model validated with 6 experimental results is set up to investigate the performance of ETSC system and evaluate the feasibility of applying the modified ETSC in small-scale industries. The results indicate that the average temperature of heat transfer fluid in a modified tube increased to 160.32 °C which is higher than a standard tube by approximately 22 °C leading to the increase in its efficiency by 34.96%.

Numerical Investigation of Heat Transfer, Fluid Flow and Formation of Emissions in Diesel Engines

2013 ◽  
Author(s):  
Müjdat Firat
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Combustion Engine ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Nox Emissions ◽  
Combustion Pressure ◽  
Crank Angle ◽  
The Relationship ◽  
Hole Number

The present study has been performed on heat transfer, fluid flow and formation of emissions in a diesel engine by different engine parameters. The analysis aims at an investigation of flow field, heat transfer, combustion pressure and formation of emission by means of numerical simulation which is using as parameter; hole number of injector and crank angle. Numerical simulations are performed using the AVL-FIRE commercial software depending on the crank angle. This software is successfully used in internal combustion engine applications, and its validity has been accepted. In this paper, k-zeta-f is preferred as turbulence model and SIMPLE/PISO used as algorithms. Thus, results are presented with pressure traces, temperature curves and NOx and soot levels for engine operating conditions. In addition, the relationship between the spray behaviors and combustion characteristics including NOx emissions, soot emissions, combustion pressure and temperature were illustrated through this analysis.

Geothermal Power Cycle Analysis for Commercial Applicability Using Sequestered Supercritical CO2 as a Heat Transfer or Working Fluid

2011 ◽  
Author(s):  
Brian Janke ◽  
Thomas Kuehn
Keyword(s):  
Heat Transfer ◽  
Binary System ◽  
Power Plants ◽  
Power Production ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Direct System ◽  
Geothermal Power ◽  
The Impact

Thermodynamic analysis has been conducted for geothermal power cycles using a portion of deep ground sequestered CO2 as the working fluid. This allows energy production from much shallower depths and in geologic areas with much lower temperature gradients than those of current geothermal systems. Two different system designs were analyzed for power production with varying reservoir parameters, including reservoir depth, temperature, and CO2 mass flow rate. The first design is a direct single-loop system with the CO2 run directly through the turbine. This system was found to provide higher system efficiency and power production, however design complications such as the need for high pressure turbines, two-phase flow through the turbine and the potential for water-CO2 brine mixtures, could require the use of numerous custom components, driving up the cost. The second design is a binary system using CO2 as the heat transfer fluid to supply thermal energy to an Organic Rankine Cycle (ORC). While this system was found to have slightly less power production and efficiency than the direct system, it significantly reduces the impact of design complications associated with the direct system. This in turn reduces the necessity for certain custom components, thereby reducing system cost. While performance of these two systems is largely dependent on location and operating conditions, the binary system is likely applicable to a larger number of sites and will be more cost effective when used in combination with current off-the-shelf ORC power plants.

Volume Element Model for Modeling, Simulation, and Optimization of Parabolic Trough Solar Collectors

2017 ◽  
Author(s):  
Tugba S. Sensoy ◽  
Sam Yang ◽  
Juan C. Ordonez
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Mathematical Formulation ◽  
Element Model ◽  
Volume Element ◽  
Heat Transfer Fluid ◽  
Solar Collectors ◽  
Parabolic Trough ◽  
Simulation And Optimization ◽  
Proposed Model

In this paper we present a dynamic three-dimensional volume element model (VEM) of a parabolic trough solar collector (PTC) comprising an outer glass cover, annular space, absorber tube, and heat transfer fluid. The spatial domain in the VEM is discretized with lumped control volumes (i.e., volume elements) in cylindrical coordinates according to the predefined collector geometry; therefore, the spatial dependency of the model is taken into account without the need to solve partial differential equations. The proposed model combines principles of thermodynamics and heat transfer, along with empirical heat transfer correlations, to simplify the modeling and expedite the computations. The resulting system of ordinary differential equations is integrated in time, yielding temperature fields which can be visualized and assessed with scientific visualization tools. In addition to the mathematical formulation, we present the model validation using the experimental data provided in the literature, and conduct two simple case studies to investigate the collector performance as a function of annulus pressure for different gases as well as its dynamic behavior throughout a sunny day. The proposed model also exhibits computational advantages over conventional PTC models-the model has been written in Fortran with parallel computing capabilities. In summary, we elaborate the unique features of the proposed model coupled with enhanced computational characteristics, and demonstrate its suitability for future simulation and optimization of parabolic trough solar collectors.

Heat Transfer Augmentation in Solar Collectors Using Nanofluids: A Review

2020 ◽  
Vol 6 (2) ◽  
pp. 72-81 ◽  
Author(s):  
Morteza Anbarsooz ◽  
Maryam Amiri ◽  
Iman Rashidi ◽  
Mohammad Javadi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Process ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Optical Parameters ◽  
Solar Collectors ◽  
Direct Absorption ◽  
Heat Transfer Augmentation

Background: Enhancing the heat transfer rate in solar collectors is an essential factor for reducing the size of the system. Yet, various methods have been presented in the literature to increase the heat transfer rate from an absorber to the heat transfer fluid. The most important methods are: the use of evacuated receivers, addition of swirl generators/turbulators and use of various nanofluids as the heat transfer fluid. Objective: The current study reviews the achievements in the enhancement of solar collectors’ heat transfer process using various types of nanofluids. The review revealed that the most widely employed nanoparticles are Al2O3 and Carbon nanotubes (CNTs) and the most popular base fluid is water. Most of the investigations are performed on indirect solar collectors, while recently, the researchers focused on direct absorption methods. In the indirect absorption collectors, the thermal conductivity of the working fluid is essential, while in a direct absorption collector, the optical properties are also crucial. Optimization of the optical parameters along with the thermophysical properties of the nanofluid is suggested for the applications of solar collector.

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