scholarly journals The effect of the intermediate fluid flow rate on the system performance in the closed circuit applications of the solar collector

2019 ◽  
pp. 472-472 ◽  
Author(s):  
Hasan Yildizhan ◽  
Taqi Cheema ◽  
Mecit Sivrioğlu
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Closed Loop ◽  
Closed Circuit ◽  
Working Fluid ◽  
Solar Collectors ◽  
Flow Rates ◽  
Energy And Exergy

Solar collector water heating system use solar thermal energy to provide hot water for domestic and industrial use. These systems are operated either as open-loop or closed-loop flow circuit. The former loop systems are not recommended for the cold climates having water freezing problem. Although previous studies on solar collectors have used closed-loop operation with water as the working fluid; however, it must have high boiling and low freezing points for the colder regions and thus arises the need for antifreeze mixtures of water. Another solution to the same problem is the use of heat transfer oil as intermediate working fluids. In the present study, the energy and exergy analysis of a boiler supported vacuum tube solar collector system working with closed-loop in different working fluid flow rates have been performed and evaluated. Heat transfer oil has been used as an intermediate working fluid in the closed loop system at different flow rates of 0.277 kg/s, 0.383 kg/s, 0.494 kg/s. The results show that the collector temperature difference as well as the outlet temperature decrease; however, the collector inlet temperature increases by increasing the flow rate. Moreover, with the increase in flow rate, it was ascertained that the energy and exergy efficiency of the system and the collectors increase. The main finding of the present study is that the intermediate fluid used in the closed-circuit operation of the solar collectors has a direct effect on the energy and exergy efficiency of the system.

scholarly journals Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

2012 ◽  
Vol 16 (suppl. 2) ◽  
pp. 471-482 ◽  
Author(s):  
Velimir Stefanovic ◽  
Sasa Pavlovic ◽  
Marko Ilic ◽  
Nenad Apostolovic ◽  
Dragan Kustrimovic
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Solar Radiation ◽  
Solar Energy ◽  
Radiation Intensity ◽  
Solar Collector ◽  
Numerical Procedure ◽  
Working Fluid ◽  
Flow Rates ◽  
Solar Radiation Intensity

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

First and second thermodynamic law analyses applied to a solar dish collector

2014 ◽  
Vol 39 (4) ◽  
Author(s):  
Vahid Madadi ◽  
Touraj Tavakoli ◽  
Amir Rahimi
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Flow Rates ◽  
Energy And Exergy ◽  
Mass Flow Rates

AbstractThe energy and exergy performance of a parabolic dish collector is investigated experimentally and theoretically. The effect of receiver type, inlet temperature and mass flow rate of heat transfer fluid (HTF), receiver temperature, receiver aspect ratio and solar radiation are investigated. To evaluate the effect of the receiver aperture area on the system performance, three aperture diameters are considered. It is deduced that the fully opened receivers have the greatest exergy and thermal efficiency. The cylindrical receiver has greater energy and exergy efficiency than the conical one due to less exergy destruction. It is found that the highest exergy destruction is due to heat transfer between the sun and the receivers and counts for 35 % to 60 % of the total wasted exergy. For three selected receiver aperture diameters, the exergy efficiency is minimum for a specified HTF mass flow rate. High solar radiation allows the system to work at higher HTF inlet temperatures. To use this system in applications that need high temperatures, in cylindrical and conical receivers, the HTF mass flow rates lower than 0.05 and 0.09 kg/s are suggested, respectively. For applications that need higher amounts of energy content, higher HTF mass flow rates than the above mentioned values are recommended.

scholarly journals Using Graphene Nanoplatelets Nanofluid in a Closed-Loop Evacuated Tube Solar Collector—Energy and Exergy Analysis

2021 ◽  
Vol 5 (10) ◽  
pp. 277
Author(s):  
Soudeh Iranmanesh ◽  
Mahyar Silakhori ◽  
Mohammad S. Naghavi ◽  
Bee C. Ang ◽  
Hwai C. Ong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Flow Rate ◽  
Closed Loop ◽  
Heat Transfer Fluid ◽  
Second Law ◽  
Bejan Number ◽  
Pumping Power ◽  
Energy And Exergy ◽  
Second Law Analysis

Recently, nanofluid application as a heat transfer fluid for a closed-loop solar heat collector is receiving great attention among the scientific community due to better performance. The performance of solar systems can be assessed effectively with the exergy method. The present study deals with the thermodynamic performance of the second law analysis using graphene nanoplatelets nanofluids. Second law analysis is the main tool for explaining the exergy output of thermodynamic and energy systems. The performance of the closed-loop system in terms of energy and exergy was determined by analyzing the outcome of field tests in tropical weather conditions. Moreover, three parameters of entropy generation, pumping power and Bejan number were also determined. The flowrates of 0.5, 1 and 1.5 L/min and GNP mass percentage of 0.025, 0.5, 0.075 and 0.1 wt% were used for these tests. The results showed that in a flow rate of 1.5 L/min and a concentration of 0.1 wt%, exergy and thermal efficiencies were increased to about 85.5 and 90.7%, respectively. It also found that entropy generation reduced when increasing the nanofluid concentration. The Bejan number surges up when increasing the concentration, while this number decreases with the enhancement of the volumetric flow rate. The pumping power of the nanofluid-operated system for a 0.1 wt% particle concentration at 0.5 L/min indicated 5.8% more than when pure water was used as the heat transfer fluid. Finally, this investigation reveals the perfect conditions that operate closest to the reversible limit and helps the system make the best improvement.

Dimensioning of Spiral Heat Exchangers to Give Minimum Costs

1984 ◽  
Vol 106 (3) ◽  
pp. 633-637 ◽  
Author(s):  
A. B. Jarze˛bski
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Input Data ◽  
Heating Surface ◽  
Working Fluid ◽  
Spiral Flow ◽  
Flow Rates ◽  
Process Fluid ◽  
Minimum Costs

Simple expressions are presented for calculating approximate dimensions of spiral heat exchangers to give minimum annual cost of heating surface plus energy required to pump the fluids. The case of spiral–spiral flow is considered. Equations are derived for exchangers with and without distance holders between plate strips and for two sets of input data: (i) both volumetric fluid flow rates V1, V2 and all inlet and appropriate outlet temperatures are given; (ii) the flow rate of the process fluid V1 and the effectiveness e1 are imposed, while the flow rate of the working fluid V2 is an additional variable subject to optimization. For the latter case, appropriate optimum values of V2 can readily be found from the graphs provided.

Performance Analysis of a Solar Collector Using Nanofluids

2013 ◽  
Vol 832 ◽  
pp. 107-112 ◽  
Author(s):  
Mohammad Abdul Alim ◽  
Rahman Saidur ◽  
Mohammad Alam Khairul ◽  
Nasrudin A. Rahim ◽  
Zainul Abdin
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Solar Collectors ◽  
Thermal Systems ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Energy And Exergy ◽  
Qualitative Performance

The Efficiency of Energy and Exergy is Generally Used as the Mostimportant Parameter in Order to Introduce and Compare the Thermal Systems Offlat Plate Solar Collectors. the First Law of Thermodynamics is Not Solelycapable of Demonstrating Quantitative and Qualitative Performance of Suchsystems, so the Second Law is Required to Illustrate the Performances. in Thispaper, an Analysis was Done for Heat Transfer Performance and Exergy Efficiencyof Flat Plate Solar Collectors Using Four Types of Nanofluids, e.g. Zno/water,CeO2/water, Nio and Coo/water. these Nanofluids were Used Withdifferent Nanoparticle Volume Fractions in the Range of 1% to 4%. Besides this,the Present Work also Focuses on the Performance of Solar Collector Withdifferent Volume Flow Rates. Investigation Consequences are also Compared Withthe Presently Available Literature for Conventional Solar Collectors. Thehighest Heat Transfer Performance and Exergy Efficiency were Obtained for CeO2/waternanofluid among all Nanofluids. Nio/water and Coo/water Nanofluids Representalmost same Performance but Higher than Water. the Results Reveal that, CeO2/waternanofluid Indicates Maximum Heat Transfer with Maximum Exergy.

scholarly journals Numerical modeling of a flat air solar collector fitted with obstacles

2021 ◽  
Vol 321 ◽  
pp. 04016
Author(s):  
Mohammed Amine Amraoui ◽  
Fayssal Benosman
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Fluid Flow ◽  
Heat Exchange ◽  
Solar Collector ◽  
Air Flow ◽  
Flow Path ◽  
Solar Collectors ◽  
Air Stream ◽  
Ansys Cfx

The weakness of the solution of flat-air solar collectors in the absence of a turbulence promoter has led researchers to seek other means to improve the performance of the collector. to improve the heat exchange in the air stream from the flat solar collector to the air is the creation of baffles or obstacles to give the longest possible flow path and create a large possible turbulence network. In this article, we studied an air flow around an obstacle field in a flat air solar collector, using the Ansys CFX calculator software, we make a digital 3 D similarity and we give results on the heat exchange in the flat air solar collector and the aim of this study is to show the effect of the obstacles for the fluid flow and the heat transfer in the fluid flow of the flat air solar collector.

scholarly journals Modelling an unconventional closed-loop deep borehole heat exchanger (DBHE): sensitivity analysis on the Newberry volcanic setting

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Hannah R. Doran ◽  
Theo Renaud ◽  
Gioia Falcone ◽  
Lehua Pan ◽  
Patrick G. Verdin
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Flow ◽  
Closed Loop ◽  
Working Fluid ◽  
Valuable Insight ◽  
Deep Borehole

AbstractAlternative (unconventional) deep geothermal designs are needed to provide a secure and efficient geothermal energy supply. An in-depth sensitivity analysis was investigated considering a deep borehole closed-loop heat exchanger (DBHE) to overcome the current limitations of deep EGS. A T2Well/EOS1 model previously calibrated on an experimental DBHE in Hawaii was adapted to the current NWG 55-29 well at the Newberry volcano site in Central Oregon. A sensitivity analysis was carried out, including parameters such as the working fluid mass flow rate, the casing and cement thermal properties, and the wellbore radii dimensions. The results conclude the highest energy flow rate to be 1.5 MW, after an annulus radii increase and an imposed mass flow rate of 5 kg/s. At 3 kg/s, the DBHE yielded an energy flow rate a factor of 3.5 lower than the NWG 55-29 conventional design. Despite this loss, the sensitivity analysis allows an assessment of the key thermodynamics within the wellbore and provides a valuable insight into how heat is lost/gained throughout the system. This analysis was performed under the assumption of subcritical conditions, and could aid the development of unconventional designs within future EGS work like the Newberry Deep Drilling Project (NDDP). Requirements for further software development are briefly discussed, which would facilitate the modelling of unconventional geothermal wells in supercritical systems to support EGS projects that could extend to deeper depths.

scholarly journals Energy and Exergy Efficiency Analysis of Fluid Flow and Heat Transfer in Sinter Vertical Cooler

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4522
Author(s):  
Zude Cheng ◽  
Haitao Wang ◽  
Junsheng Feng ◽  
Yongfang Xia ◽  
Hui Dong
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Fluid Flow ◽  
Waste Heat ◽  
Exergy Efficiency ◽  
Inlet Temperature ◽  
Operational Parameters ◽  
Flow And Heat Transfer ◽  
Maximum Value ◽  
Energy And Exergy

In order to fully understand the energy and exergy transfer processes in sinter vertical coolers, a simulation model of the fluid flow and heat transfer in a vertical cooler was established, and energy and exergy efficiency analyses of the gas–solid heat transfer in a vertical cooler were conducted in detail. Based on the calculation method of the whole working condition, the suitable operational parameters of the vertical cooler were obtained by setting the net exergy efficiency in the vertical cooler as the indicator function. The results show that both the quantity of sinter waste heat recovery (SWHR) and energy efficiency increased as the air flow rate (AFR) increased, and they decreased as the air inlet temperature (AIT) increased. The increase in the sinter inlet temperature (SIT) resulted in an increase in the quantity of SWHR and a decrease in energy efficiency. The air net exergy had the maximum value as the AFR increased, and it only increased monotonically as the SIT and AIT increased. The net exergy efficiency reached the maximum value as the AFR and AIT increased, and the increase in the SIT only resulted in a decrease in the net exergy efficiency. When the sinter annual production of a 360 m2 sintering machine was taken as the processing capacity of the vertical cooler, the suitable operational parameters of the vertical cooler were 190 kg/s for the AFR, and 353 K for the AIT.

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