Ines-Noelly Tano, E. Rasouli, Tracey Ziev, Junwon Seo, Nicholas Lamprinakos, Parth Vaishnav, A. Rollett, Ziheng Wu, V. Narayanan
Design of an additively manufactured molten salt (MS) to supercritical carbon dioxide (sCO2) primary heat exchanger (PHE) for solar thermal power generation is presented. The PHE is designed to handle temperatures up to 720 °C on the MS side and an internal pressure of 200 bar on the sCO2 side. In the core, MS flows through a three-dimensional periodic lattice network, while sCO2 flows within pin arrays. The design includes integrated sCO2 headers located within the MS flow, allowing for a counter flow design of the PHE. The sCO2 headers are configured to enable uniform flow distribution into each sCO2 plate while withstanding an internal pressure of 200 bar and minimizing obstruction to the flow of MS around it. The structural integrity of the design is verified on AM 316 stainless steel printed sub-scale specimens. An experimentally-validated, correlation-based sectional PHE core thermofluidic model is developed to study the impact of flow and geometrical parameters on the PHE performance, with varied parameters including the mass flow rate, surface roughness, and PHE dimensions. A process-based cost model is used to determine the impact of parameter variation on build cost. The model results show that a heat exchanger with a power density of 18.6 MW/m3 (including sCO2 header volume) and effectiveness of 0.88 can be achieved at a heat capacity rate ratio of 0.8. The impact of design and AM machine parameters on the cost of the PHE are assessed.
{"title":"A Scalable Compact Additively Manufactured Molten Salt to Supercritical Carbon Dioxide Heat Exchanger for Solar Thermal Application","authors":"Ines-Noelly Tano, E. Rasouli, Tracey Ziev, Junwon Seo, Nicholas Lamprinakos, Parth Vaishnav, A. Rollett, Ziheng Wu, V. Narayanan","doi":"10.1115/1.4063081","DOIUrl":"https://doi.org/10.1115/1.4063081","url":null,"abstract":"\u0000 Design of an additively manufactured molten salt (MS) to supercritical carbon dioxide (sCO2) primary heat exchanger (PHE) for solar thermal power generation is presented. The PHE is designed to handle temperatures up to 720 °C on the MS side and an internal pressure of 200 bar on the sCO2 side. In the core, MS flows through a three-dimensional periodic lattice network, while sCO2 flows within pin arrays. The design includes integrated sCO2 headers located within the MS flow, allowing for a counter flow design of the PHE. The sCO2 headers are configured to enable uniform flow distribution into each sCO2 plate while withstanding an internal pressure of 200 bar and minimizing obstruction to the flow of MS around it. The structural integrity of the design is verified on AM 316 stainless steel printed sub-scale specimens. An experimentally-validated, correlation-based sectional PHE core thermofluidic model is developed to study the impact of flow and geometrical parameters on the PHE performance, with varied parameters including the mass flow rate, surface roughness, and PHE dimensions. A process-based cost model is used to determine the impact of parameter variation on build cost. The model results show that a heat exchanger with a power density of 18.6 MW/m3 (including sCO2 header volume) and effectiveness of 0.88 can be achieved at a heat capacity rate ratio of 0.8. The impact of design and AM machine parameters on the cost of the PHE are assessed.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44766953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tucker Farrell, Yue Cao, F. Burkholder, Daniel Celvi, Christa Schreiber, G. Zhu
The National Renewable Energy Laboratory (NREL) has been conducting exposure experiments on solar reflectors for over four decades. Thousands of mirror samples from over one hundred suppliers have been exposed to and monitored in a range of relevant environments. These test conditions include outdoor test settings and several controlled laboratory environments. These samples have been rigorously individually characterized using a series of reflectance measurements, visual inspections, and in some cases, in-depth composition analysis to identify degradation modes, reflectance losses, and other mirror properties integral to understanding the solar reflector's life cycle. This paper compiles the decades of measurement data into a concise statistical analysis. It includes exposure and degradation data for numerous reflector types, including secondary-surface reflector permutations of polymer and glass superstrates with silver and aluminum reflectors as well as front-surface reflectors. The results herein are intended to analyze environmental stressors and degradation trends among various historical and state-of-the-art solar reflectors. It may be used to support solar reflector design, effective testing methodology, and inform manufacturing decisions moving forward. Presented are the results of the compiled database and an initial analysis for degradation rate modeling using full-spectrum and wavelength-dependent approaches. The database is a growing resource hosted on a live, publicly accessible website. In conjunction with the analysis presented here, it provides a valuable resource to the solar reflector manufacturing and testing industry.
{"title":"Compilation of a Solar Mirror Materials Database and an Analysis of Natural and Accelerated Mirror Exposure and Degradation","authors":"Tucker Farrell, Yue Cao, F. Burkholder, Daniel Celvi, Christa Schreiber, G. Zhu","doi":"10.1115/1.4063079","DOIUrl":"https://doi.org/10.1115/1.4063079","url":null,"abstract":"\u0000 The National Renewable Energy Laboratory (NREL) has been conducting exposure experiments on solar reflectors for over four decades. Thousands of mirror samples from over one hundred suppliers have been exposed to and monitored in a range of relevant environments. These test conditions include outdoor test settings and several controlled laboratory environments. These samples have been rigorously individually characterized using a series of reflectance measurements, visual inspections, and in some cases, in-depth composition analysis to identify degradation modes, reflectance losses, and other mirror properties integral to understanding the solar reflector's life cycle. This paper compiles the decades of measurement data into a concise statistical analysis. It includes exposure and degradation data for numerous reflector types, including secondary-surface reflector permutations of polymer and glass superstrates with silver and aluminum reflectors as well as front-surface reflectors. The results herein are intended to analyze environmental stressors and degradation trends among various historical and state-of-the-art solar reflectors. It may be used to support solar reflector design, effective testing methodology, and inform manufacturing decisions moving forward. Presented are the results of the compiled database and an initial analysis for degradation rate modeling using full-spectrum and wavelength-dependent approaches. The database is a growing resource hosted on a live, publicly accessible website. In conjunction with the analysis presented here, it provides a valuable resource to the solar reflector manufacturing and testing industry.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45381876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. V, Rutvik S. Solank, V. K. Chalamalla, S. Sinha
The current strong global consensus on reducing carbon emissions is a motivation to develop more efficient means of harnessing sustainable sources of energy. Accordingly, research efforts toward the development of more efficient wind turbine designs are desirable. With this motivation, we present a set of numerical studies on flows past vertical axis wind turbines (VAWT). We perform large eddy simulations (LES) of flows past several VAWT configurations. The influence of turbine blades on the flow field is modelled using the actuator line method (ALM). Our focus is on a twin-rotor configuration wherein the rotors are placed close enough, so that the separation between the centres of the two rotors is less than the diameter of the two individual turbines (the overlapping configuration). We demonstrate that such a configuration indeed results in (a) enhanced power coefficient (ratio of power extracted by the turbine configuration to the power available in the free stream) and (b) better power density (power extracted by a turbine configuration per unit ground area occupied by the VAWT) compared to a single rotor VAWT configuration. Based on our findings, we conclude that the overlapping twin-rotor arrangement can prove to be the preferred configuration for large-scale VAWT-based wind farms.
{"title":"Evaluation of the performance of twin-rotor vertical axis wind turbines employing large-eddy simulations","authors":"S. V, Rutvik S. Solank, V. K. Chalamalla, S. Sinha","doi":"10.1115/1.4063080","DOIUrl":"https://doi.org/10.1115/1.4063080","url":null,"abstract":"\u0000 The current strong global consensus on reducing carbon emissions is a motivation to develop more efficient means of harnessing sustainable sources of energy. Accordingly, research efforts toward the development of more efficient wind turbine designs are desirable. With this motivation, we present a set of numerical studies on flows past vertical axis wind turbines (VAWT). We perform large eddy simulations (LES) of flows past several VAWT configurations. The influence of turbine blades on the flow field is modelled using the actuator line method (ALM). Our focus is on a twin-rotor configuration wherein the rotors are placed close enough, so that the separation between the centres of the two rotors is less than the diameter of the two individual turbines (the overlapping configuration). We demonstrate that such a configuration indeed results in (a) enhanced power coefficient (ratio of power extracted by the turbine configuration to the power available in the free stream) and (b) better power density (power extracted by a turbine configuration per unit ground area occupied by the VAWT) compared to a single rotor VAWT configuration. Based on our findings, we conclude that the overlapping twin-rotor arrangement can prove to be the preferred configuration for large-scale VAWT-based wind farms.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44796516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There has been an increasing interest in solar-driven combined energy supply systems for low-temperate applications, particularly those based on the Organic Rankine Cycle (ORC), Kalina Cycle (KC), or Trilateral Cycle (TLC). However, systems based on these thermodynamic cycles usually employ large area collectors that stand alone or are placed on the roof, without considering integration with the building facade. This research presents a solution to large-scale photothermal utilization integrated with facades for co-generated systems. The current study is the first to conduct performance and economic assessment for four novel solar cooling and power (SCP) co-generated systems driven by evacuated tube solar collectors (ETCs) or semi-transparent photovoltaic (STPV) integrated into the building facades. The suggested systems were simulated using TRNSYS to forecast their performance metrics when used in four Chinese cities with various climate zones. As indicators, a solar fraction (SF) and unit energy cost (UEC) was used to evaluate the technical and financial aspects of each system. The STPV-vapor compression cycle (VCC) system had the highest SF (100%, except Haikou), as well as the lowest UEC (0.211/kWh on average) among the four cities, according to the results. Among the three solar − thermal co − generation systems, ETC − ORC − VCC had the best performance (SF:37.9%, UEC:0.597/kWh on average).
{"title":"Technical and economic performance of four solar cooling and power (SCP) co-generated systems integrated with façades in Chinese climate zones","authors":"Fei Lai, Dan Wu, Jinzhi Zhou, Yanping Yuan","doi":"10.1115/1.4063023","DOIUrl":"https://doi.org/10.1115/1.4063023","url":null,"abstract":"\u0000 There has been an increasing interest in solar-driven combined energy supply systems for low-temperate applications, particularly those based on the Organic Rankine Cycle (ORC), Kalina Cycle (KC), or Trilateral Cycle (TLC). However, systems based on these thermodynamic cycles usually employ large area collectors that stand alone or are placed on the roof, without considering integration with the building facade. This research presents a solution to large-scale photothermal utilization integrated with facades for co-generated systems. The current study is the first to conduct performance and economic assessment for four novel solar cooling and power (SCP) co-generated systems driven by evacuated tube solar collectors (ETCs) or semi-transparent photovoltaic (STPV) integrated into the building facades. The suggested systems were simulated using TRNSYS to forecast their performance metrics when used in four Chinese cities with various climate zones. As indicators, a solar fraction (SF) and unit energy cost (UEC) was used to evaluate the technical and financial aspects of each system. The STPV-vapor compression cycle (VCC) system had the highest SF (100%, except Haikou), as well as the lowest UEC (0.211/kWh on average) among the four cities, according to the results. Among the three solar − thermal co − generation systems, ETC − ORC − VCC had the best performance (SF:37.9%, UEC:0.597/kWh on average).","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45730037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The cogeneration system described here is constructed based on a solar-assisted double-effect absorption cogeneration cycle with an adjustable cooling-to-power ratio. To benefit from the ability to adjust the cooling-to-power ratio, this system is integrated with a cold thermal energy storage (TES) system. The procedure described here is applied to a combined cooling and power system with a TES capability for a large medical center in Jeddah, KSA. Through an exergoeconomic analysis of the integrated system on a typical summer day in Jeddah, we found that the system could fulfill the cooling and power demands of the medical center with an exergetic efficiency of 53.97%. From an economics perspective, the integrated system was found to deliver cooling and power with average unit costs of 222.89$/GJ and 17.06$/GJ, respectively. These costs are lower than the unit costs of the respective cooling and power costs delivered to the medical center if they were obtained from an electrically-driven vapor compression system (VCS) and the electric grid, respectively. For the case study investigated, it was found that using the integrated system is a desirable approach. It was also found that although cogeneration systems constructed based on the double-effect combined cooling and power (DECCP) cycle have higher exergy destruction and capital investment rates, they have a lower unit cost for the produced exergy in comparison with those of cogeneration systems constructed based on a single-effect combined cooling and power (SECCP) cycle.
{"title":"Exergoeconomics of a Solar-Assisted Double-Effect Absorption Cogeneration System Integrated with a Cold Thermal Energy Storage System","authors":"Abdulmajeed Alghamdi, S. Sherif","doi":"10.1115/1.4062965","DOIUrl":"https://doi.org/10.1115/1.4062965","url":null,"abstract":"\u0000 The cogeneration system described here is constructed based on a solar-assisted double-effect absorption cogeneration cycle with an adjustable cooling-to-power ratio. To benefit from the ability to adjust the cooling-to-power ratio, this system is integrated with a cold thermal energy storage (TES) system. The procedure described here is applied to a combined cooling and power system with a TES capability for a large medical center in Jeddah, KSA. Through an exergoeconomic analysis of the integrated system on a typical summer day in Jeddah, we found that the system could fulfill the cooling and power demands of the medical center with an exergetic efficiency of 53.97%. From an economics perspective, the integrated system was found to deliver cooling and power with average unit costs of 222.89$/GJ and 17.06$/GJ, respectively. These costs are lower than the unit costs of the respective cooling and power costs delivered to the medical center if they were obtained from an electrically-driven vapor compression system (VCS) and the electric grid, respectively. For the case study investigated, it was found that using the integrated system is a desirable approach. It was also found that although cogeneration systems constructed based on the double-effect combined cooling and power (DECCP) cycle have higher exergy destruction and capital investment rates, they have a lower unit cost for the produced exergy in comparison with those of cogeneration systems constructed based on a single-effect combined cooling and power (SECCP) cycle.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44026154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper proposes an innovative approach to improve the performance of solar cooling systems by utilizing a cascaded absorption cooling (CAC) system. The paper also examines the viability of coupling an NH3-H2O absorption system with an H2O-LiBr absorption system to simultaneously satisfy both a refrigeration load and an air-conditioning load. Results of this analysis shows that the CAC system uses 7.1% less thermal energy than the sum of the energies used by the ammonia absorption system and the LiBr absorption system if they were to operate separately to meet the same cooling load. In addition, the paper investigates the impact of a performance-enhanced parabolic trough collector (PEPTC) on the thermal and exergetic efficiencies of the solar cooling system. By employing a PEPTC, the area required for the solar field in a given solar cooling system will be reduced by 14% compared to the area required by a conventional PTC. Combining the CAC system with the PEPTC results in a 22% increase in the overall efficiency of a cooling plant compared to a conventional PTC coupled with an ammonia system and a LiBr system in the same plant. In summary, it is suggested that the simultaneous utilization of the proposed CAC system and the PEPTC can considerably improve the efficiency of solar cooling systems. Doing so, will lead to sustainable cooling alternatives.
{"title":"Performance Analysis of a Solar Cascaded Absorption Cooling System (SCAC) Using a Performance-Enhanced Parabolic Trough Collector","authors":"F. Altwijri, S. Sherif, Abdulmajeed Alghamdi","doi":"10.1115/1.4062964","DOIUrl":"https://doi.org/10.1115/1.4062964","url":null,"abstract":"\u0000 This paper proposes an innovative approach to improve the performance of solar cooling systems by utilizing a cascaded absorption cooling (CAC) system. The paper also examines the viability of coupling an NH3-H2O absorption system with an H2O-LiBr absorption system to simultaneously satisfy both a refrigeration load and an air-conditioning load. Results of this analysis shows that the CAC system uses 7.1% less thermal energy than the sum of the energies used by the ammonia absorption system and the LiBr absorption system if they were to operate separately to meet the same cooling load. In addition, the paper investigates the impact of a performance-enhanced parabolic trough collector (PEPTC) on the thermal and exergetic efficiencies of the solar cooling system. By employing a PEPTC, the area required for the solar field in a given solar cooling system will be reduced by 14% compared to the area required by a conventional PTC. Combining the CAC system with the PEPTC results in a 22% increase in the overall efficiency of a cooling plant compared to a conventional PTC coupled with an ammonia system and a LiBr system in the same plant. In summary, it is suggested that the simultaneous utilization of the proposed CAC system and the PEPTC can considerably improve the efficiency of solar cooling systems. Doing so, will lead to sustainable cooling alternatives.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43661534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin Alvarez Alor, Jesús Arce Landa, D. Colorado-Garrido
In this paper, a numerical heat transfer study of a solar air collector with two channels (SAC-2C) was carried out. Energy global balances in two dimensions (2D) and unsteady state were considered, as well as bio-climatic conditions of Toluca city in Mexico (sub-humid temperate climate). Six mass flow rates (0.01, 0.05, 0.1, 0.2, 0.4, 0.5 kg/s) were considered during the numerical simulation, for the coldest and the warmest day of each month during a complete year (2019). Among the results, it was found that thermal efficiency of the system increases up 35% when the mass flow rate change from 0.01 to 0.2 kg/s, meanwhile the maximum efficiency of 84% were obtained, for a mass flow rate of 0.5 kg/s. Finally, based on a cost-benefit analysis, it was determined that the SAC-2C has a recovery time of the initial investment ($ 250 USD) of 3 and a half years. So that, the SAC-2C has the capacity to produce 1,654,451 kWh/m2 of clean energy annually, which is equivalent to ceasing to produce 871,895 kg CO2 per square meter of installation.
{"title":"Transient Study (Annual) of the Heat Transfer of a Two-Channel Solar Air Collector","authors":"Benjamin Alvarez Alor, Jesús Arce Landa, D. Colorado-Garrido","doi":"10.1115/1.4062875","DOIUrl":"https://doi.org/10.1115/1.4062875","url":null,"abstract":"\u0000 In this paper, a numerical heat transfer study of a solar air collector with two channels (SAC-2C) was carried out. Energy global balances in two dimensions (2D) and unsteady state were considered, as well as bio-climatic conditions of Toluca city in Mexico (sub-humid temperate climate). Six mass flow rates (0.01, 0.05, 0.1, 0.2, 0.4, 0.5 kg/s) were considered during the numerical simulation, for the coldest and the warmest day of each month during a complete year (2019). Among the results, it was found that thermal efficiency of the system increases up 35% when the mass flow rate change from 0.01 to 0.2 kg/s, meanwhile the maximum efficiency of 84% were obtained, for a mass flow rate of 0.5 kg/s. Finally, based on a cost-benefit analysis, it was determined that the SAC-2C has a recovery time of the initial investment ($ 250 USD) of 3 and a half years. So that, the SAC-2C has the capacity to produce 1,654,451 kWh/m2 of clean energy annually, which is equivalent to ceasing to produce 871,895 kg CO2 per square meter of installation.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43526534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The entropy generation minimization principle is used as the criterion to optimize the flow and heat transfer of solar collectors and heat exchangers that use molten salts NaCl–KCl–MgCl2 and KCl–MgCl2. The Gnielinski correlation for the Nusselt number versus Reynolds number, as well as the Moody friction factor given by Petukhov, was used for the calculation of the convective heat transfer coefficient and pressure loss due to friction in smooth tubes. For twisted-tap-inserted tube, equations of Nu and friction factor provided by Manglik and Bergles were used. The objective function, the entropy generation rate of the heat transfer system, was expressed as the function of Reynolds number, Prandtl number, heating flux, tube diameter, etc. As a result of the analysis, the optimum Reynolds number was determined and thereby to determine the optimum Nusselt number, convective heat transfer coefficient, friction factor, and tube diameter, which also allows the calculation of optimum flow velocity. The analysis was conducted in the fluid temperature range of 500–700 °C, which covers the operation temperature for supercritical CO2 power cycles in concentrated solar power (CSP) system. Optimized results from the smooth tube and twisted-tap-inserted tube are compared, which is important to the design of solar receivers for CSP systems.
{"title":"Optimization of Dimensions of Smooth and Twisted-Tape-Inserted Tubes for Heat Transfer with NaCl/KCl/MgCl2 Molten Salts by Principle of Entropy Generation Minimization","authors":"F. Haddad, Peiwen Li","doi":"10.1115/1.4062719","DOIUrl":"https://doi.org/10.1115/1.4062719","url":null,"abstract":"\u0000 The entropy generation minimization principle is used as the criterion to optimize the flow and heat transfer of solar collectors and heat exchangers that use molten salts NaCl–KCl–MgCl2 and KCl–MgCl2. The Gnielinski correlation for the Nusselt number versus Reynolds number, as well as the Moody friction factor given by Petukhov, was used for the calculation of the convective heat transfer coefficient and pressure loss due to friction in smooth tubes. For twisted-tap-inserted tube, equations of Nu and friction factor provided by Manglik and Bergles were used. The objective function, the entropy generation rate of the heat transfer system, was expressed as the function of Reynolds number, Prandtl number, heating flux, tube diameter, etc. As a result of the analysis, the optimum Reynolds number was determined and thereby to determine the optimum Nusselt number, convective heat transfer coefficient, friction factor, and tube diameter, which also allows the calculation of optimum flow velocity. The analysis was conducted in the fluid temperature range of 500–700 °C, which covers the operation temperature for supercritical CO2 power cycles in concentrated solar power (CSP) system. Optimized results from the smooth tube and twisted-tap-inserted tube are compared, which is important to the design of solar receivers for CSP systems.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43639127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates a solar air heater's thermohydraulic and thermogeometric performances with an artificially roughened absorber plate with Joukowski airfoil ribs. The rib height and shape have a bearing on the overall performance of the air heater. Joukowski airfoil ribs of different sizes are generated from a circular rib of a radius of 1mm using conformal mapping. Simulations are performed for the turbulent flow of air through the roughened duct in the Reynolds number (Re) range of 4000 = Re = 15000 using ANSYS Fluent version 2020. The renormalization group kinetic energy-turbulence dissipation rate (RNG κ-ε) model with enhanced wall treatment (EWT) has been employed to model the turbulent flow. The grid refinement study is performed to optimize the mesh size and estimate the numerical solution error. The proposed rib design is tested for both headwind and tailwind flow arrangements. The tailwind performance is better for smaller-size Joukowski ribs. However, the medium and large-size Joukowski ribs perform better in headwind configurations. At low Re, heat transfer is more dominant than friction leading to higher thermohydraulic performance, whereas, at high Re, the reverse trend is observed.
{"title":"Performance Investigation of a Solar Air Heater Artificially Roughened with Joukowski Airfoil Ribs","authors":"Bibhrat Roy, Desireddy Shashidhar Reddy, Mohd. Kaleem Khan","doi":"10.1115/1.4062818","DOIUrl":"https://doi.org/10.1115/1.4062818","url":null,"abstract":"\u0000 This paper investigates a solar air heater's thermohydraulic and thermogeometric performances with an artificially roughened absorber plate with Joukowski airfoil ribs. The rib height and shape have a bearing on the overall performance of the air heater. Joukowski airfoil ribs of different sizes are generated from a circular rib of a radius of 1mm using conformal mapping. Simulations are performed for the turbulent flow of air through the roughened duct in the Reynolds number (Re) range of 4000 = Re = 15000 using ANSYS Fluent version 2020. The renormalization group kinetic energy-turbulence dissipation rate (RNG κ-ε) model with enhanced wall treatment (EWT) has been employed to model the turbulent flow. The grid refinement study is performed to optimize the mesh size and estimate the numerical solution error. The proposed rib design is tested for both headwind and tailwind flow arrangements. The tailwind performance is better for smaller-size Joukowski ribs. However, the medium and large-size Joukowski ribs perform better in headwind configurations. At low Re, heat transfer is more dominant than friction leading to higher thermohydraulic performance, whereas, at high Re, the reverse trend is observed.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45703434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The demand for quality dried products necessitates cost effective and innovative drying techniques that will improve its market value. The slow drying rate, weather dependency, and moisture reabsorption have been identified as the major challenges of solar drying operation. To address these shortcomings, hybrid solar drying systems have been recommended for the drying of various agricultural materials and other porous products. Designing a better drying system to accommodate thermal storage materials requires detailed analysis, which could be achieved through numerical simulation. Therefore, the numerical simulation of heat and mass transfer in a forced convection solar drying system integrated with black coated firebrick sensible thermal storage materials (STSM) for the cocoa beans, locust beans, cereal grains, etc. was investigated under no load conditions. The equations governing the fluid flow for a three-dimensional (3D) solar drying system were solved using the Finite Volume Method (FVM) with the aid of ANSYS, the computational fluid dynamics (CFD) software to comprehend the dynamic and thermal behaviour of the airflow within the dryer. The experimental maximum temperature values of 96.9 and 77.3oC for the collector and drying chamber were in agreement with the simulated maximum collector and drying chamber temperatures (CT and DCT) of 116.9 and 80oC respectively. The designed solar drying system with the incorporated STSM showed the capacity of raising the temperature of the air within the drying chamber to 3-37oC above ambient temperature between 13:00 hr to 22:00 hr. The agreement of the simulated dryer model with the experimental one is an indication that the developed dryer is suitable for drying cocoa, locust beans, fish, cereal grains, and some other agricultural products within an acceptable period based on the previous studies and therefore, the drying system is recommended to avoid the shortcomings associated with traditional/open sun drying.
{"title":"Numerical simulation of the 3D simultaneous heat and mass transfer in a forced convection solar drying system integrated with thermal storage material","authors":"Clement Adekunle Komolafe","doi":"10.1115/1.4062484","DOIUrl":"https://doi.org/10.1115/1.4062484","url":null,"abstract":"\u0000 The demand for quality dried products necessitates cost effective and innovative drying techniques that will improve its market value. The slow drying rate, weather dependency, and moisture reabsorption have been identified as the major challenges of solar drying operation. To address these shortcomings, hybrid solar drying systems have been recommended for the drying of various agricultural materials and other porous products. Designing a better drying system to accommodate thermal storage materials requires detailed analysis, which could be achieved through numerical simulation. Therefore, the numerical simulation of heat and mass transfer in a forced convection solar drying system integrated with black coated firebrick sensible thermal storage materials (STSM) for the cocoa beans, locust beans, cereal grains, etc. was investigated under no load conditions. The equations governing the fluid flow for a three-dimensional (3D) solar drying system were solved using the Finite Volume Method (FVM) with the aid of ANSYS, the computational fluid dynamics (CFD) software to comprehend the dynamic and thermal behaviour of the airflow within the dryer. The experimental maximum temperature values of 96.9 and 77.3oC for the collector and drying chamber were in agreement with the simulated maximum collector and drying chamber temperatures (CT and DCT) of 116.9 and 80oC respectively. The designed solar drying system with the incorporated STSM showed the capacity of raising the temperature of the air within the drying chamber to 3-37oC above ambient temperature between 13:00 hr to 22:00 hr. The agreement of the simulated dryer model with the experimental one is an indication that the developed dryer is suitable for drying cocoa, locust beans, fish, cereal grains, and some other agricultural products within an acceptable period based on the previous studies and therefore, the drying system is recommended to avoid the shortcomings associated with traditional/open sun drying.","PeriodicalId":17124,"journal":{"name":"Journal of Solar Energy Engineering-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43058590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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