Thermal energy can be better harvested and stored by integrating thermal diodes with thermal energy storage systems. Among different types of thermal diodes, jumping-droplet thermal diodes exploiting superhydrophilic and superhydrophobic surfaces yield greater thermal rectification performance (i.e. diodicity) due to high latent heat. However, the condensation heat transfer and coalescing-jumping droplets are restricted by the ability of water to nucleate on the superhydrophobic surface, leading to a limited maximum jumping height, finally resulting in degradation of diodicity of the thermal diode. To solve this problem, we propose coating hydrophilic bumps on the superhydrophobic surface which can provide preferable nucleation sites, forming a new type of nanostructured surface, called biphilic surface. This work aims to investigate coalescence-induced jumping droplets on biphilic surfaces to enhance diodicity of phase change thermal diodes. Our experimental results show that the jumping height and jumping volumetric flux of the coalescence-induced jumping droplets on a biphilic surface are enhanced by 42% and 254% compared to those on a superhydrophobic surface, respectively. Based on the jumping droplet results, a mathematical model for diodicity is built. 244% improvement can be achieved in the thermal diode with an optimized biphilic surface as compared to that with a superhydrophobic surface, which provides an effective strategy to improve the diodicity of a phase change thermal diode and an alternative approach to enhance the energy harvesting and storage capability in thermal energy storage systems.
{"title":"Study of Coalescence-Induced Jumping Droplets on Biphilic Nanostructured Surfaces for Thermal Diodes in Thermal Energy Storage Systems","authors":"Y. Zhu, C. Tso, T. C. Ho, C. Chao","doi":"10.1115/es2020-1703","DOIUrl":"https://doi.org/10.1115/es2020-1703","url":null,"abstract":"\u0000 Thermal energy can be better harvested and stored by integrating thermal diodes with thermal energy storage systems. Among different types of thermal diodes, jumping-droplet thermal diodes exploiting superhydrophilic and superhydrophobic surfaces yield greater thermal rectification performance (i.e. diodicity) due to high latent heat. However, the condensation heat transfer and coalescing-jumping droplets are restricted by the ability of water to nucleate on the superhydrophobic surface, leading to a limited maximum jumping height, finally resulting in degradation of diodicity of the thermal diode. To solve this problem, we propose coating hydrophilic bumps on the superhydrophobic surface which can provide preferable nucleation sites, forming a new type of nanostructured surface, called biphilic surface. This work aims to investigate coalescence-induced jumping droplets on biphilic surfaces to enhance diodicity of phase change thermal diodes. Our experimental results show that the jumping height and jumping volumetric flux of the coalescence-induced jumping droplets on a biphilic surface are enhanced by 42% and 254% compared to those on a superhydrophobic surface, respectively. Based on the jumping droplet results, a mathematical model for diodicity is built. 244% improvement can be achieved in the thermal diode with an optimized biphilic surface as compared to that with a superhydrophobic surface, which provides an effective strategy to improve the diodicity of a phase change thermal diode and an alternative approach to enhance the energy harvesting and storage capability in thermal energy storage systems.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81742554","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 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":"49 1","pages":""},"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}
Ray-tracing and heat-transfer simulations of discrete particles in a representative elementary volume were performed to determine the effective particle-cloud absorptance and temperature profiles as a function of intrinsic particle absorptance values (0 – 1) for dilute solids volume fractions (1 – 3%) representative of falling particle receivers used in concentrating solar power applications. Results showed that the average particle-cloud absorptance is increased above intrinsic particle absorptance values as a result of reflections and subsequent reabsorption (light trapping). The relative increase in effective particle-cloud absorptance was greater for lower values of intrinsic particle absorptance and could be as high as a factor of two. Higher values of intrinsic particle absorptance led to higher simulated steady-state particle temperatures. Significant temperature gradients within the particle cloud and within the particles themselves were also observed in the simulations. Findings indicate that dilute particle-cloud configurations within falling particle receivers can significantly enhance the apparent effective absorptance of the particle curtain, and materials with higher values of intrinsic particle absorptance will yield greater radiative absorptance and temperatures.
{"title":"Evaluating the Effective Solar Absorptance of Dilute Particle Configurations","authors":"C. Ho, Luis F. González-Portillo, Kevin Albrecht","doi":"10.1115/es2020-1676","DOIUrl":"https://doi.org/10.1115/es2020-1676","url":null,"abstract":"\u0000 Ray-tracing and heat-transfer simulations of discrete particles in a representative elementary volume were performed to determine the effective particle-cloud absorptance and temperature profiles as a function of intrinsic particle absorptance values (0 – 1) for dilute solids volume fractions (1 – 3%) representative of falling particle receivers used in concentrating solar power applications. Results showed that the average particle-cloud absorptance is increased above intrinsic particle absorptance values as a result of reflections and subsequent reabsorption (light trapping). The relative increase in effective particle-cloud absorptance was greater for lower values of intrinsic particle absorptance and could be as high as a factor of two. Higher values of intrinsic particle absorptance led to higher simulated steady-state particle temperatures. Significant temperature gradients within the particle cloud and within the particles themselves were also observed in the simulations. Findings indicate that dilute particle-cloud configurations within falling particle receivers can significantly enhance the apparent effective absorptance of the particle curtain, and materials with higher values of intrinsic particle absorptance will yield greater radiative absorptance and temperatures.","PeriodicalId":8602,"journal":{"name":"ASME 2020 14th International Conference on Energy Sustainability","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72708934","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":"152 1","pages":""},"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":"1 1","pages":""},"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":"44 1","pages":""},"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":"1 1","pages":""},"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":"95 1","pages":""},"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":"22 1","pages":""},"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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