In this paper, the effect of solar resource variability has been assessed on the start-up time and different heat transfer phenomena associated with a high temperature particle receiver. The receiver analyzed in this study has a cylindrical cavity made of three different layers in order to have good absorption, higher durability and lower thermal heat losses. A detailed transient mathematical model is developed, considering the input solar energy to the receiver aperture and all heat losses from the receiver cavity. The developed transient model is employed to study the time required to achieve a receiver start-up temperature from room temperature to 1000°C, under steady-state and transient operation, for the climatic conditions of Pinjarra, Australia. Furthermore, the total energy gain by the receiver and associated heat losses including re-radiation, convection, and conduction have been accounted for, with and without considering the solar resource variability. The results revealed that an uncertainty of about 40% exists in the prediction of the receiver start-up time and associated heat losses during the start-up period under steady state operation, with a constant input heat flux. This uncertainty in the prediction of the receiver start-up time and losses will directly affect the overall performance and design of the receiver, which will result in unscheduled disruption of the industrial process. This indicates a need to analyse the performance of high temperature particle receivers under transient conditions, considering the solar resource variability for practical implementation of this technology to different processes. This will help to investigate better control strategies for the inflow of particles, based on the real-time climatic conditions, to achieve better thermal performance.
{"title":"Uncertainty in Predicting the Start-Up Time and Losses for a High Temperature Particle Receiver due to Solar Resource Variability","authors":"M. Rafique, G. Nathan, W. Saw","doi":"10.1115/es2020-1649","DOIUrl":"https://doi.org/10.1115/es2020-1649","url":null,"abstract":"\u0000 In this paper, the effect of solar resource variability has been assessed on the start-up time and different heat transfer phenomena associated with a high temperature particle receiver. The receiver analyzed in this study has a cylindrical cavity made of three different layers in order to have good absorption, higher durability and lower thermal heat losses. A detailed transient mathematical model is developed, considering the input solar energy to the receiver aperture and all heat losses from the receiver cavity. The developed transient model is employed to study the time required to achieve a receiver start-up temperature from room temperature to 1000°C, under steady-state and transient operation, for the climatic conditions of Pinjarra, Australia. Furthermore, the total energy gain by the receiver and associated heat losses including re-radiation, convection, and conduction have been accounted for, with and without considering the solar resource variability. The results revealed that an uncertainty of about 40% exists in the prediction of the receiver start-up time and associated heat losses during the start-up period under steady state operation, with a constant input heat flux. This uncertainty in the prediction of the receiver start-up time and losses will directly affect the overall performance and design of the receiver, which will result in unscheduled disruption of the industrial process. This indicates a need to analyse the performance of high temperature particle receivers under transient conditions, considering the solar resource variability for practical implementation of this technology to different processes. This will help to investigate better control strategies for the inflow of particles, based on the real-time climatic conditions, to achieve better thermal performance.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89622979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
On the anode side of a direct methanol fuel cell, carbon dioxide bubbles are generated as a result of the methanol oxidation reaction. The accumulation of such bubbles prevents methanol from reaching the gas diffusion layer. Hence, a significant reduction in the reaction rate occurs, which limits the maximum current density of the cell. To keep carbon dioxide bubbles away from the gas diffusion layer interface, a new design of the anode flow channel besides wall surface treatment is developed. Such a design can introduce the Concus-Finn phenomena, which forces the carbon dioxide bubbles to move away from the gas diffusion layer due to capillary forces. This can be achieved by using a trapezoidal shape of the flow channel, as well as the combined effect of hydrophobic and hydrophilic surface treatments on the gas-diffusion layer and channel walls. To identify the optimal design of the anode flow channel, a three-dimensional, two-phase flow model is developed. The model is numerically simulated and results are validated with available measurements. Results indicated that treating the gas-diffusion layer with a hydrophilic layer increases the area in direct contact with liquid methanol. Besides, the hydrophobic top channel surfaces make it easier for the carbon dioxide bubbles to attach and spread out on the channel top surface. The current findings create a promising opportunity to improve the performance of direct methanol fuel cells.
{"title":"Effect of Anode Flow Channel Design on the Carbon Dioxide Bubble Removal in Direct Methanol Fuel Cells","authors":"Sameer Osman, S. Ookawara, Mahmoud A. Ahmed","doi":"10.1115/es2020-1659","DOIUrl":"https://doi.org/10.1115/es2020-1659","url":null,"abstract":"\u0000 On the anode side of a direct methanol fuel cell, carbon dioxide bubbles are generated as a result of the methanol oxidation reaction. The accumulation of such bubbles prevents methanol from reaching the gas diffusion layer. Hence, a significant reduction in the reaction rate occurs, which limits the maximum current density of the cell. To keep carbon dioxide bubbles away from the gas diffusion layer interface, a new design of the anode flow channel besides wall surface treatment is developed. Such a design can introduce the Concus-Finn phenomena, which forces the carbon dioxide bubbles to move away from the gas diffusion layer due to capillary forces. This can be achieved by using a trapezoidal shape of the flow channel, as well as the combined effect of hydrophobic and hydrophilic surface treatments on the gas-diffusion layer and channel walls. To identify the optimal design of the anode flow channel, a three-dimensional, two-phase flow model is developed. The model is numerically simulated and results are validated with available measurements. Results indicated that treating the gas-diffusion layer with a hydrophilic layer increases the area in direct contact with liquid methanol. Besides, the hydrophobic top channel surfaces make it easier for the carbon dioxide bubbles to attach and spread out on the channel top surface. The current findings create a promising opportunity to improve the performance of direct methanol fuel cells.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87427970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Globally there are several viable sources of renewable, low-temperature heat (below 130°C) particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and promising system to generate electrical power from renewable sources based on its beneficial use of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference for/an inclination towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled by better matches of the temperature profiles of the WF and the heat source/sink. This paper demonstrates both the technical feasibility and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines the thermodynamic performance of ORC systems using zeotropic WF mixtures to generate electricity driven by low-temperature solar heat source for building applications. A thermodynamic model is developed with an ORC system both with and excluding a regenerator. Five zeotropic mixtures with varying compositions of R245fa/propane, R245fa/hexane, R245fa/heptane, pentane/hexane and isopentane/hexane are evaluated and compared to identify the best combinations of WF mixtures that can yield high efficiency in their system cycles. The study also investigates the effects of the volumetric flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane is selected for parametric study to examine the effects of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results showed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a significant increase in cycle efficiency can be achieved with a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also showed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar organic Rankine cycles.
{"title":"Performance Investigation of Solar Organic Rankine Cycle Systems With and Without Regeneration and With Zeotropic Working Fluid Mixtures for Use in Micro-Cogeneration","authors":"W. Yaïci, E. Entchev, P. Sardari","doi":"10.1115/es2020-1616","DOIUrl":"https://doi.org/10.1115/es2020-1616","url":null,"abstract":"\u0000 Globally there are several viable sources of renewable, low-temperature heat (below 130°C) particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and promising system to generate electrical power from renewable sources based on its beneficial use of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference for/an inclination towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled by better matches of the temperature profiles of the WF and the heat source/sink.\u0000 This paper demonstrates both the technical feasibility and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines the thermodynamic performance of ORC systems using zeotropic WF mixtures to generate electricity driven by low-temperature solar heat source for building applications. A thermodynamic model is developed with an ORC system both with and excluding a regenerator. Five zeotropic mixtures with varying compositions of R245fa/propane, R245fa/hexane, R245fa/heptane, pentane/hexane and isopentane/hexane are evaluated and compared to identify the best combinations of WF mixtures that can yield high efficiency in their system cycles.\u0000 The study also investigates the effects of the volumetric flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane is selected for parametric study to examine the effects of operating parameters on the system’s efficiency and sustainability index.\u0000 For zeotropic mixtures, results showed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a significant increase in cycle efficiency can be achieved with a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also showed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar organic Rankine cycles.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88085699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Sment, Mario J. Martinez, Kevin Albrecht, C. Ho
The National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories is conducting research on a Generation 3 Particle Pilot Plant (G3P3) that uses falling sandlike particles as the heat transfer medium. The system will include a thermal energy storage (TES) bin with a capacity of 6 MWht¬ requiring ∼120,000 kg of flowing particles. Testing and modeling were conducted to develop a validated modeling tool to understand temporal and spatial temperature distributions within the storage bin as it charges and discharges. Flow and energy transport in funnel-flow was modeled using volume averaged conservation equations coupled with level set interface tracking equations that prescribe the dynamic geometry of particle flow within the storage bin. A thin layer of particles on top of the particle bed was allowed to flow toward the center and into the flow channel above the outlet. Model results were validated using particle discharge temperatures taken from thermocouples mounted throughout a small steel bin. The model was then used to predict heat loss during charging, storing, and discharging operational modes at the G3P3 scale. Comparative results from the modeling and testing of the small bin indicate that the model captures many of the salient features of the transient particle outlet temperature over time.
{"title":"Testing and Simulations of Spatial and Temporal Temperature Variations in a Particle-Based Thermal Energy Storage Bin","authors":"J. Sment, Mario J. Martinez, Kevin Albrecht, C. Ho","doi":"10.1115/es2020-1660","DOIUrl":"https://doi.org/10.1115/es2020-1660","url":null,"abstract":"\u0000 The National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories is conducting research on a Generation 3 Particle Pilot Plant (G3P3) that uses falling sandlike particles as the heat transfer medium. The system will include a thermal energy storage (TES) bin with a capacity of 6 MWht¬ requiring ∼120,000 kg of flowing particles. Testing and modeling were conducted to develop a validated modeling tool to understand temporal and spatial temperature distributions within the storage bin as it charges and discharges.\u0000 Flow and energy transport in funnel-flow was modeled using volume averaged conservation equations coupled with level set interface tracking equations that prescribe the dynamic geometry of particle flow within the storage bin. A thin layer of particles on top of the particle bed was allowed to flow toward the center and into the flow channel above the outlet.\u0000 Model results were validated using particle discharge temperatures taken from thermocouples mounted throughout a small steel bin. The model was then used to predict heat loss during charging, storing, and discharging operational modes at the G3P3 scale. Comparative results from the modeling and testing of the small bin indicate that the model captures many of the salient features of the transient particle outlet temperature over time.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79586877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates the performance of an optimal indoor environment in a campus classroom. The control system is able to regulate and balance the needs for illuminance, thermal comfort, air quality, and energy saving. By incorporating with Machine Learning and illumination algorithm associated with Internet of Things, wireless communication and adapted control, optimal energy saving and environment control can be achieved. Additionally, by using Video Image Detection to analyze the number of occupants and distribution in the classroom offers better energy optimization. In this study, the split-type air conditioning system has been used which is different from that in most literatures. About 30 tests are conducted and the occupant numbers range from 1 to 2 hours and each hour is 50 minutes. The class types include normal lecture and examination which shows completely different characteristics. The proposed AI agent contains the benefits not only for small or medium indoor space, but also for residences. In order to adjust the indoor illuminance, wireless and adjustable illuminance level LED were installed. Under the control of the illumination algorithm, the illuminance of each area of the classroom can be optimized according to the occupant distribution. The test results indicate that, by maintaining thermal comfort and air quality, when comparing with fixed setting point control 25 degrees, the average energy saving is 19%, and the average CO2 concentration is decreased by 21.3%. When comparing with setting point temperature of 26 degrees, the average energy saving is 15% the average CO2 is decreased by 12.9%.
{"title":"AI Based Energy Optimization in Association With Class Environment","authors":"K. Yu, Emanuel Jaimes, Chi-Chuan Wang","doi":"10.1115/es2020-1696","DOIUrl":"https://doi.org/10.1115/es2020-1696","url":null,"abstract":"\u0000 This study investigates the performance of an optimal indoor environment in a campus classroom. The control system is able to regulate and balance the needs for illuminance, thermal comfort, air quality, and energy saving. By incorporating with Machine Learning and illumination algorithm associated with Internet of Things, wireless communication and adapted control, optimal energy saving and environment control can be achieved. Additionally, by using Video Image Detection to analyze the number of occupants and distribution in the classroom offers better energy optimization. In this study, the split-type air conditioning system has been used which is different from that in most literatures. About 30 tests are conducted and the occupant numbers range from 1 to 2 hours and each hour is 50 minutes. The class types include normal lecture and examination which shows completely different characteristics. The proposed AI agent contains the benefits not only for small or medium indoor space, but also for residences. In order to adjust the indoor illuminance, wireless and adjustable illuminance level LED were installed. Under the control of the illumination algorithm, the illuminance of each area of the classroom can be optimized according to the occupant distribution. The test results indicate that, by maintaining thermal comfort and air quality, when comparing with fixed setting point control 25 degrees, the average energy saving is 19%, and the average CO2 concentration is decreased by 21.3%. When comparing with setting point temperature of 26 degrees, the average energy saving is 15% the average CO2 is decreased by 12.9%.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81925025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ganesh Doiphode, H. Najafi, Mariana Migliori Favaretto
Buildings are one of the largest energy consumers in the United States. K-12 schools are responsible for nearly 8% of energy consumption by commercial buildings which is equivalent to 1.44% of total annual energy consumption in the country. Understanding the baseline energy consumption of the schools as well as identifying effective energy efficiency measures (EEMs) that result in significant energy savings without compromising occupant’s comfort in a given climate condition are essential factors in moving towards a sustainable future. In a collaboration between Florida Institute of Technology and Brevard Public Schools, three schools are identified for a test study in Melbourne, FL, representing the humid subtropical climate. Energy audit is conducted for these schools and monthly utility bill data as well as background information, end-user’s data and their associated operating schedules are obtained. A detailed analysis is performed on the utility bill data and energy consumption by each end-user is estimated. Several EEMs are considered and evaluated to achieve an improved energy efficiency for the schools. The implementation cost of each EEM and the associated simple payback period is also determined. A study is also conducted to explore possibility of using solar power to cover 50% of energy requirements of each school and the cost and payback period of the project are evaluated. The results of this paper provide insights regarding prioritizing energy efficiency projects in K-12 schools in humid subtropical climates and particularly the state of Florida and help with decision making regarding investment in on-site power generation using solar energy.
{"title":"Energy Efficiency in K-12 Schools: A Case Study in Florida","authors":"Ganesh Doiphode, H. Najafi, Mariana Migliori Favaretto","doi":"10.1115/es2020-1632","DOIUrl":"https://doi.org/10.1115/es2020-1632","url":null,"abstract":"\u0000 Buildings are one of the largest energy consumers in the United States. K-12 schools are responsible for nearly 8% of energy consumption by commercial buildings which is equivalent to 1.44% of total annual energy consumption in the country. Understanding the baseline energy consumption of the schools as well as identifying effective energy efficiency measures (EEMs) that result in significant energy savings without compromising occupant’s comfort in a given climate condition are essential factors in moving towards a sustainable future. In a collaboration between Florida Institute of Technology and Brevard Public Schools, three schools are identified for a test study in Melbourne, FL, representing the humid subtropical climate. Energy audit is conducted for these schools and monthly utility bill data as well as background information, end-user’s data and their associated operating schedules are obtained. A detailed analysis is performed on the utility bill data and energy consumption by each end-user is estimated. Several EEMs are considered and evaluated to achieve an improved energy efficiency for the schools. The implementation cost of each EEM and the associated simple payback period is also determined. A study is also conducted to explore possibility of using solar power to cover 50% of energy requirements of each school and the cost and payback period of the project are evaluated. The results of this paper provide insights regarding prioritizing energy efficiency projects in K-12 schools in humid subtropical climates and particularly the state of Florida and help with decision making regarding investment in on-site power generation using solar energy.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90175730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present work, a ray tracing model based on Snell’s law of refraction is developed using MATLAB for the design of Fresnel lens with spherical facets of equal height. In practice, the facet curvature is approximated by straight line, which causes an increase in spherical aberrations and reduction in concentration ratio. The proposed model takes facet curvature into consideration, which will result in effective utilization of incident solar radiations. Fresnel lenses are available with facets having constant width and facets with constant height. A comparison of spherical aberrations in the two cases has also been presented using different f - numbers (ratio of focal length to aperture diameter). Effect of different parameters like number of facets and refractive index of lens material on concentration ratio is also presented in present study. The proposed ray tracing model is validated with the model developed in SolTrace, an open access software. The predictions from the proposed model are in good agreement with the results of SolTrace model with an average deviations of 6.8% for concentration ratio and 2.2% for focal length.
{"title":"Design of Fresnel Lens With Constant Height Spherical Facets","authors":"Kuldeep Awasthi, Desireddy Shashidhar Reddy, Mohd. Kaleem Khan","doi":"10.1115/es2020-1652","DOIUrl":"https://doi.org/10.1115/es2020-1652","url":null,"abstract":"In the present work, a ray tracing model based on Snell’s law of refraction is developed using MATLAB for the design of Fresnel lens with spherical facets of equal height. In practice, the facet curvature is approximated by straight line, which causes an increase in spherical aberrations and reduction in concentration ratio. The proposed model takes facet curvature into consideration, which will result in effective utilization of incident solar radiations. Fresnel lenses are available with facets having constant width and facets with constant height. A comparison of spherical aberrations in the two cases has also been presented using different f - numbers (ratio of focal length to aperture diameter). Effect of different parameters like number of facets and refractive index of lens material on concentration ratio is also presented in present study. The proposed ray tracing model is validated with the model developed in SolTrace, an open access software. The predictions from the proposed model are in good agreement with the results of SolTrace model with an average deviations of 6.8% for concentration ratio and 2.2% for focal length.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86480779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jesus D. Ortega, G. Anaya, P. Vorobieff, G. Mohan, C. Ho
The Falling Particle Receiver (FPR) at the National Solar Thermal Test Facility (NSTTF) is a testbed for promising receiver technologies offering solutions to the temperature and irradiance limitations exhibited by gas and molten salt receivers, since the particle curtain is directly irradiated without the need of containment. Until recently, the heat loss of the NSTTF 1 MWth FPR was not fully characterized. One of the challenges of the FPR characterization is the intricate flow conditions that the particle curtain experiences due to its cavity design with a single open aperture, to allow the direct irradiance. Recently, particle plumes expelled from the FPR during operation were observed. While this phenomenon affects the FPR heat loss and needs to be closely monitored, it is extremely difficult to operate any kind of sensors near the aperture of the FPR. This work describes the development of a methodology using a high-speed IR camera, located ≥ 5 meters away from the aperture, to estimate the opacity of a particle plume, which in turn can be used to extract the average particle temperature of a region of interest with a known background temperature. Experiments performed at the University of New Mexico using four different flow configurations and three different temperatures (200, 450, and 750°C) were conducted to determine the relationship between the plume opacity in the visible range and the “particle-pixel” opacity obtained from thermograms in the IR range. We present a “particle-pixel function” that describes the combined impact of an unknown number of particles at a specific temperature on a thermogram pixel value with an initial value equal to the background temperature. The novelty of this function is that it provides a reasonable estimate of the plume opacity using thermograms obtained from the IR camera; hence a bulk particle temperature can be obtained. Future development of this methodology will make it possible to compute the advective losses from the FPR and provide a first order approximation of the convective losses for the system.
{"title":"Imaging Particle Temperatures and Curtain Opacities Using an IR Camera","authors":"Jesus D. Ortega, G. Anaya, P. Vorobieff, G. Mohan, C. Ho","doi":"10.1115/es2020-1688","DOIUrl":"https://doi.org/10.1115/es2020-1688","url":null,"abstract":"\u0000 The Falling Particle Receiver (FPR) at the National Solar Thermal Test Facility (NSTTF) is a testbed for promising receiver technologies offering solutions to the temperature and irradiance limitations exhibited by gas and molten salt receivers, since the particle curtain is directly irradiated without the need of containment. Until recently, the heat loss of the NSTTF 1 MWth FPR was not fully characterized. One of the challenges of the FPR characterization is the intricate flow conditions that the particle curtain experiences due to its cavity design with a single open aperture, to allow the direct irradiance. Recently, particle plumes expelled from the FPR during operation were observed. While this phenomenon affects the FPR heat loss and needs to be closely monitored, it is extremely difficult to operate any kind of sensors near the aperture of the FPR. This work describes the development of a methodology using a high-speed IR camera, located ≥ 5 meters away from the aperture, to estimate the opacity of a particle plume, which in turn can be used to extract the average particle temperature of a region of interest with a known background temperature. Experiments performed at the University of New Mexico using four different flow configurations and three different temperatures (200, 450, and 750°C) were conducted to determine the relationship between the plume opacity in the visible range and the “particle-pixel” opacity obtained from thermograms in the IR range. We present a “particle-pixel function” that describes the combined impact of an unknown number of particles at a specific temperature on a thermogram pixel value with an initial value equal to the background temperature. The novelty of this function is that it provides a reasonable estimate of the plume opacity using thermograms obtained from the IR camera; hence a bulk particle temperature can be obtained. Future development of this methodology will make it possible to compute the advective losses from the FPR and provide a first order approximation of the convective losses for the system.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85473711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An increasing trend in building energy simulations is to use simplified models to reduce simulation time, evaluate different model configurations, and analyze for energy consumption across different constructions and weather climates. Simplified models tend to share some common benefits such as ease of calibration and reduced setup and operation time. All of which allows for shorter time and simpler program to evaluate different situations or systems. Some of these simplified models ignore thermal capacitance within walls and roofs; removing thermal capacitance can decrease simulation time but may alter loading due to ignoring the delay between when exterior surfaces receive loading and when the load is transferred to the interior. While this simplification is sometimes useful, it often overlooks the delay that occurs between the external wall heating and that heat being transferred to the interior. This paper will explore alternative methods for evaluating conduction loads in opaque surfaces for use in building energy models. Specifically, a differential equation conduction method with numerical integration, closed form solution, and forward difference calculation. These methods will be evaluated for how different conduction simulation techniques can be used in different situations to provide a potential increase in accuracy for simplified models while simultaneously reducing computational loads. Understanding the physics of dynamic envelope loading can change how much energy a building uses and when room conditioning needs to occur.
{"title":"Comparison and Implementation of Thermally Massive Wall and Roof Models for Use in Simplified Building Energy Models","authors":"Christopher Fernandez, S. Jeter","doi":"10.1115/es2019-3909","DOIUrl":"https://doi.org/10.1115/es2019-3909","url":null,"abstract":"\u0000 An increasing trend in building energy simulations is to use simplified models to reduce simulation time, evaluate different model configurations, and analyze for energy consumption across different constructions and weather climates. Simplified models tend to share some common benefits such as ease of calibration and reduced setup and operation time. All of which allows for shorter time and simpler program to evaluate different situations or systems.\u0000 Some of these simplified models ignore thermal capacitance within walls and roofs; removing thermal capacitance can decrease simulation time but may alter loading due to ignoring the delay between when exterior surfaces receive loading and when the load is transferred to the interior. While this simplification is sometimes useful, it often overlooks the delay that occurs between the external wall heating and that heat being transferred to the interior. This paper will explore alternative methods for evaluating conduction loads in opaque surfaces for use in building energy models. Specifically, a differential equation conduction method with numerical integration, closed form solution, and forward difference calculation. These methods will be evaluated for how different conduction simulation techniques can be used in different situations to provide a potential increase in accuracy for simplified models while simultaneously reducing computational loads. Understanding the physics of dynamic envelope loading can change how much energy a building uses and when room conditioning needs to occur.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83075519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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