Abstract Enhancing the performance of passive solar chimneys constitutes a key point for successful applications in bioclimatic architecture. Present work assesses applications of several kinds of flow disturbers in a rooftop solar chimney, under isoflux heating and windless conditions, and including surface radiative effects. Systematic numerical calculations are conducted aiming a comprehensive analysis, by means of a low-Reynolds turbulence model, being the range of Rayleigh number considered 2.170 × 1012 − 2.170 × 1013. Effect of different geometrical parameters is analyzed, although main attention is posed on the influence of disturbers elements on the thermohydraulic behavior of the established airflow, for obtaining best performance conditions. Some obstacles cause a clear decrease in the efficiency of the system, but given disturbers appropriately located produce valuable enhancements in the thermal or dynamic efficiency. Insertion of intermediate plates proves to be the best option, achieving maximum increases of even approximately 50% in the ventilation capacity.
{"title":"Enhancing the performance of a rooftop solar chimney through flow disturbers","authors":"Blas Zamora","doi":"10.1115/1.4063458","DOIUrl":"https://doi.org/10.1115/1.4063458","url":null,"abstract":"Abstract Enhancing the performance of passive solar chimneys constitutes a key point for successful applications in bioclimatic architecture. Present work assesses applications of several kinds of flow disturbers in a rooftop solar chimney, under isoflux heating and windless conditions, and including surface radiative effects. Systematic numerical calculations are conducted aiming a comprehensive analysis, by means of a low-Reynolds turbulence model, being the range of Rayleigh number considered 2.170 × 1012 − 2.170 × 1013. Effect of different geometrical parameters is analyzed, although main attention is posed on the influence of disturbers elements on the thermohydraulic behavior of the established airflow, for obtaining best performance conditions. Some obstacles cause a clear decrease in the efficiency of the system, but given disturbers appropriately located produce valuable enhancements in the thermal or dynamic efficiency. Insertion of intermediate plates proves to be the best option, achieving maximum increases of even approximately 50% in the ventilation capacity.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"20 3-4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135513524","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}
Abstract The labyrinth seal is effective in reducing leakage losses at the rotor blade top in the turbine. This study investigates the variation in labyrinth seal performance at different rotational speeds, different Reynolds numbers, and different tooth front angles. Three Reynolds numbers (Re = 6000, 10,000, 15,000), five rotational speeds (Ta/Re = 0, 0.01, 0.04, 0.08, and 0.1), and three tooth front angles(75 deg, 90 deg, and 102.4 deg) have been introduced. The variation of leakage losses and heat transfer under different conditions is compared and a detailed analysis of the flow field and energy losses is performed. The discharge coefficient is increased slightly with increased rotational speed for the same Reynolds number. This is caused by the high rotational speed reducing the throttling loss and vortex loss. The high rotational speed enhances the heat transfer at the tip wall of the passage, and also weakens the heat transfer at the tooth cavity bottom. Additionally, the sealing capacity of the labyrinth is better at large tooth front angles, which is caused by the reduction of frictional losses on the stator and eddy current losses in the tooth cavity. The change in local pressure loss also affects the velocity distribution along the channel, which is the reason for the change in the local Nusselt number.
{"title":"Effects of Reynolds number and tooth front angle on leakage loss and heat transfer characteristics in a rotating labyrinth seal","authors":"Shaoyun Yang, Wei Du, Lei Luo, Songtao Wang","doi":"10.1115/1.4063680","DOIUrl":"https://doi.org/10.1115/1.4063680","url":null,"abstract":"Abstract The labyrinth seal is effective in reducing leakage losses at the rotor blade top in the turbine. This study investigates the variation in labyrinth seal performance at different rotational speeds, different Reynolds numbers, and different tooth front angles. Three Reynolds numbers (Re = 6000, 10,000, 15,000), five rotational speeds (Ta/Re = 0, 0.01, 0.04, 0.08, and 0.1), and three tooth front angles(75 deg, 90 deg, and 102.4 deg) have been introduced. The variation of leakage losses and heat transfer under different conditions is compared and a detailed analysis of the flow field and energy losses is performed. The discharge coefficient is increased slightly with increased rotational speed for the same Reynolds number. This is caused by the high rotational speed reducing the throttling loss and vortex loss. The high rotational speed enhances the heat transfer at the tip wall of the passage, and also weakens the heat transfer at the tooth cavity bottom. Additionally, the sealing capacity of the labyrinth is better at large tooth front angles, which is caused by the reduction of frictional losses on the stator and eddy current losses in the tooth cavity. The change in local pressure loss also affects the velocity distribution along the channel, which is the reason for the change in the local Nusselt number.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"81 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135514307","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}
Abstract In this paper, the flow condensation heat transfer characteristics of the environmentally friendly nearly-azeotropic refrigerant R1234ze(E)/R152a (mass ratio of 40:60) in smooth tubes with varying structures were numerically investigated. Under the operating conditions of mass flux of 400 kg/m2/s, heat flux of 12 kW/m2, and saturation temperature of 308.15 K, this study investigated the influence of circular tube inner diameter, elliptical tube aspect ratio, and installation orientation on condensation heat transfer, while the influence on pressure drop has not been taken into account in the present study. The results indicate that the condensation heat transfer coefficient in the tube increases as the inner diameter of the circular tube decreases. The condensation heat transfer coefficient increases by 1.086 times when the circular tube inner diameter is reduced from 10.7 mm to 5 mm. Under identical operating conditions, the condensation heat transfer coefficient of the mixed refrigerant in elliptical tubes increases with an increase in the aspect ratio. The average condensation heat transfer coefficient increases by 18.21% as the aspect ratio of the elliptical tube increases from 1 to 2. Compared to a vertical elliptical tube, a horizontal elliptical tube is more favorable for condensation heat transfer within the tube.
{"title":"The effect of heat exchanger tube structure on the condensation heat transfer of R1234ze(E)/R152a inside smooth tubes","authors":"Yuande Dai, Qingqing Tang, Chaoping Xu","doi":"10.1115/1.4063571","DOIUrl":"https://doi.org/10.1115/1.4063571","url":null,"abstract":"Abstract In this paper, the flow condensation heat transfer characteristics of the environmentally friendly nearly-azeotropic refrigerant R1234ze(E)/R152a (mass ratio of 40:60) in smooth tubes with varying structures were numerically investigated. Under the operating conditions of mass flux of 400 kg/m2/s, heat flux of 12 kW/m2, and saturation temperature of 308.15 K, this study investigated the influence of circular tube inner diameter, elliptical tube aspect ratio, and installation orientation on condensation heat transfer, while the influence on pressure drop has not been taken into account in the present study. The results indicate that the condensation heat transfer coefficient in the tube increases as the inner diameter of the circular tube decreases. The condensation heat transfer coefficient increases by 1.086 times when the circular tube inner diameter is reduced from 10.7 mm to 5 mm. Under identical operating conditions, the condensation heat transfer coefficient of the mixed refrigerant in elliptical tubes increases with an increase in the aspect ratio. The average condensation heat transfer coefficient increases by 18.21% as the aspect ratio of the elliptical tube increases from 1 to 2. Compared to a vertical elliptical tube, a horizontal elliptical tube is more favorable for condensation heat transfer within the tube.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"18 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135514412","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}
Abstract Ranque-Hilsch vortex tubes have the extraordinary ability to split an incoming stream of fluid into two streams—one with a lower total temperature than the incoming flow and the other with greater total temperature. The physical mechanism involves inducing an intense swirl of the flow down the length of the tube. The warmer flow exits around the periphery at the end of the tube, while the cooler central flow changes direction within the core and exits the opposite end. While much research has focused on the physical mechanisms of the energy separation, relatively little attention has been paid to the heat transfer behavior should a heat flux be applied to the walls. In the present work, experiments were performed using a vortex tube with varying levels of heat addition, up to approximately 15 kW/m2. Companion computational experiments were performed that allowed determination of spatially resolved Nusselt number distributions, the first of their kind for vortex tube flows. A notable finding is that the vast majority of heat added to the vortex tube flow remains within the hot stream; that is, the cold stream experiences relatively little temperature rise due to the heat addition. For example, even when only 30% of the flow exits the hot side of the tube, it retains more than 80% of the heat added to the flow. Additionally, a modified swirl number was also defined that was found to scale the Nusselt number augmentation across the two different total flow rates examined presently.
{"title":"AN EXPERIMENTAL AND COMPUTATIONAL INVESTIGATION OF RANQUE-HILSCH VORTEX TUBE HEAT TRANSFER CHARACTERISTICS","authors":"Matthew Fuqua, James L. Rutledge","doi":"10.1115/1.4063826","DOIUrl":"https://doi.org/10.1115/1.4063826","url":null,"abstract":"Abstract Ranque-Hilsch vortex tubes have the extraordinary ability to split an incoming stream of fluid into two streams—one with a lower total temperature than the incoming flow and the other with greater total temperature. The physical mechanism involves inducing an intense swirl of the flow down the length of the tube. The warmer flow exits around the periphery at the end of the tube, while the cooler central flow changes direction within the core and exits the opposite end. While much research has focused on the physical mechanisms of the energy separation, relatively little attention has been paid to the heat transfer behavior should a heat flux be applied to the walls. In the present work, experiments were performed using a vortex tube with varying levels of heat addition, up to approximately 15 kW/m2. Companion computational experiments were performed that allowed determination of spatially resolved Nusselt number distributions, the first of their kind for vortex tube flows. A notable finding is that the vast majority of heat added to the vortex tube flow remains within the hot stream; that is, the cold stream experiences relatively little temperature rise due to the heat addition. For example, even when only 30% of the flow exits the hot side of the tube, it retains more than 80% of the heat added to the flow. Additionally, a modified swirl number was also defined that was found to scale the Nusselt number augmentation across the two different total flow rates examined presently.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135823929","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}
Xiangfeng Meng, Qiuyang Yuan, Yaning Li, Xiaochen Lin, Na Liu
Abstract As a novel, compact, and efficient plate-fin heat exchanger, the Printed Circuit Heat Exchanger (PCHE) is a prospective candidate for liquefied natural gas (LNG) vaporization at low-temperature and high pressure. Generally, the airfoil fin PCHE has better thermal-hydraulic performance than the zigzag channel PCHE. In this study, the thermal-hydraulic performance of supercritical LNG in PCHEs with different airfoil fin types and arrangements is investigated by numerical simulations. First, the effects of six different airfoil fin types, NACA0010, NACA0020, NACA0025, NACA0030, NACA 0040, and NACA 0050, on the thermal-hydraulic performances were studied. The results show that NACA0025 has the best comprehensive heat transfer performance. Then, the effects of staggered, vertical, and horizontal pitch of the airfoil fin arrangement on thermal-hydraulic performance were investigated. The results show that the optimal values of the dimensionless number for staggered and vertical arrangements are 1 and 4, respectively. The comprehensive performance does not change much when the dimensionless horizontal pitch number exceeds 3.0. Finally, the thermal-hydraulic performance of uniformly distributed, three front sparse and rear dense, and three front dense and rear sparse distributed airfoil fins was investigated. The results show that the front dense and rear sparse airfoil fins enhance and the front sparse and rear dense airfoil fins reduce the comprehensive performance compared to the uniform arrangement. The results show that a denser arrangement of airfoil fins near the quasi-critical point can improve the comprehensive performance while keeping the number of airfoil fins constant.
{"title":"Numerical Analysis of the Thermal-hydraulic Performance of Supercritical LNG in Airfoil Fin PCHEs","authors":"Xiangfeng Meng, Qiuyang Yuan, Yaning Li, Xiaochen Lin, Na Liu","doi":"10.1115/1.4063751","DOIUrl":"https://doi.org/10.1115/1.4063751","url":null,"abstract":"Abstract As a novel, compact, and efficient plate-fin heat exchanger, the Printed Circuit Heat Exchanger (PCHE) is a prospective candidate for liquefied natural gas (LNG) vaporization at low-temperature and high pressure. Generally, the airfoil fin PCHE has better thermal-hydraulic performance than the zigzag channel PCHE. In this study, the thermal-hydraulic performance of supercritical LNG in PCHEs with different airfoil fin types and arrangements is investigated by numerical simulations. First, the effects of six different airfoil fin types, NACA0010, NACA0020, NACA0025, NACA0030, NACA 0040, and NACA 0050, on the thermal-hydraulic performances were studied. The results show that NACA0025 has the best comprehensive heat transfer performance. Then, the effects of staggered, vertical, and horizontal pitch of the airfoil fin arrangement on thermal-hydraulic performance were investigated. The results show that the optimal values of the dimensionless number for staggered and vertical arrangements are 1 and 4, respectively. The comprehensive performance does not change much when the dimensionless horizontal pitch number exceeds 3.0. Finally, the thermal-hydraulic performance of uniformly distributed, three front sparse and rear dense, and three front dense and rear sparse distributed airfoil fins was investigated. The results show that the front dense and rear sparse airfoil fins enhance and the front sparse and rear dense airfoil fins reduce the comprehensive performance compared to the uniform arrangement. The results show that a denser arrangement of airfoil fins near the quasi-critical point can improve the comprehensive performance while keeping the number of airfoil fins constant.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135970129","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}
Abstract The thermal characteristics of a variable temperature, flowing vapor cryostat are theoretically modeled, taking into account specific geometrical and material constraints, temperature-varying heat transfer coefficients, and thermal conductivities for conductive, convective, and radiative heat transfer. The temperature within the cryostat is controlled by an internal heater and is monitored at both the heater and the sample stage. The modeled system consists of multiple coaxial, cylindrical layers of stainless steel containing various fluids (light vacuum, helium gas, nitrogen gas; the liquid cryogen is nitrogen or helium). The calculated Prandtl and Grashof numbers for the fluid layers suggest that the Churchill-Chu form of the Nusselt equation be used for heat transfer analysis of this system. Developing a model that predicts heat flows throughout the cryostat allows for appropriate articulation of the heater so that the sample quickly reaches the desired temperature without overshooting. Transient and steady-state models are investigated for predictive ability and consistency with the system's experimentally collected heating and cooling behavior.
{"title":"Modeling Heat Transfer through Concentric Cylindrical Layers for Controlled Thermal Regulation of a Commercial Research Cryostat","authors":"Bradley M. Moran, Peter Geissinger, Jorg Woehl","doi":"10.1115/1.4063750","DOIUrl":"https://doi.org/10.1115/1.4063750","url":null,"abstract":"Abstract The thermal characteristics of a variable temperature, flowing vapor cryostat are theoretically modeled, taking into account specific geometrical and material constraints, temperature-varying heat transfer coefficients, and thermal conductivities for conductive, convective, and radiative heat transfer. The temperature within the cryostat is controlled by an internal heater and is monitored at both the heater and the sample stage. The modeled system consists of multiple coaxial, cylindrical layers of stainless steel containing various fluids (light vacuum, helium gas, nitrogen gas; the liquid cryogen is nitrogen or helium). The calculated Prandtl and Grashof numbers for the fluid layers suggest that the Churchill-Chu form of the Nusselt equation be used for heat transfer analysis of this system. Developing a model that predicts heat flows throughout the cryostat allows for appropriate articulation of the heater so that the sample quickly reaches the desired temperature without overshooting. Transient and steady-state models are investigated for predictive ability and consistency with the system's experimentally collected heating and cooling behavior.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135969757","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}
Abstract This paper proposes a new ORC-VCC(Organic Rankine Cycle+Vapor compression cycle) system(with mechanical overheating refrigeration cycle), and this system can not only reduce the heat absorption of the ORC evaporator, but also increase the refrigeration capacity of the system. Simulations were conducted to analyze the thermal efficiency and performance of the new system, and compare it with the system of ORC-VCC(with regenerator). The results show that the ηth, ηsys and COPsys(coefficient of performance) of new system are higher than the system of ORC-VCC(with regenerator), ηth, ηsys and COPsys of new system increased by up to 31.6%, 6.48%, 10.63% respectively. And the influence of superheat on both systems is stronger than other factors, the influence of superheat on the new system is obviously stronger than those of the system of ORC-VCC(with regenerator), and the influence of superheat on R245fa and Butane is stronger than those of other working fluids. In addition, ηth, ηsys, COPsys and ηex of system increase with the increase of Te-mech and decrease with the increase of Tg-mech. Finally, the correlation of δTmax with the change of ηexp and Te-orc is fitted, the results will provide some reference for the development of the ORC-VCC system in the future.
{"title":"Performance analysis of a new ORC-VCC system with mechanical overheating and correlation fitting of most important system parameter","authors":"Dahan Sun, Zhongyan Liu, Hao Zhang, Jiang Qin","doi":"10.1115/1.4063733","DOIUrl":"https://doi.org/10.1115/1.4063733","url":null,"abstract":"Abstract This paper proposes a new ORC-VCC(Organic Rankine Cycle+Vapor compression cycle) system(with mechanical overheating refrigeration cycle), and this system can not only reduce the heat absorption of the ORC evaporator, but also increase the refrigeration capacity of the system. Simulations were conducted to analyze the thermal efficiency and performance of the new system, and compare it with the system of ORC-VCC(with regenerator). The results show that the ηth, ηsys and COPsys(coefficient of performance) of new system are higher than the system of ORC-VCC(with regenerator), ηth, ηsys and COPsys of new system increased by up to 31.6%, 6.48%, 10.63% respectively. And the influence of superheat on both systems is stronger than other factors, the influence of superheat on the new system is obviously stronger than those of the system of ORC-VCC(with regenerator), and the influence of superheat on R245fa and Butane is stronger than those of other working fluids. In addition, ηth, ηsys, COPsys and ηex of system increase with the increase of Te-mech and decrease with the increase of Tg-mech. Finally, the correlation of δTmax with the change of ηexp and Te-orc is fitted, the results will provide some reference for the development of the ORC-VCC system in the future.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136209945","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}
Yanjun Chen, Chenhao Du, Zhoumiao Wang, Deqiang He
Abstract Transformer-oil with low thermal conductivity and large viscosity has poor heat dissipation capability, which leads to the thermal drive failure caused by transient overload. To improve its cooling capability, this paper has proposed firstly the method combined the periodically direction-switching electric field and graphene nanofluid to enhance the mixed convective heat transfer properties of transformer-oil, and analyzed the effects of switching periods, nanofluid concentration, electric field strength, heat flux and Reynolds number on mixed convection heat transfer experimentally. The results show that the heat transfer characteristic of transformer-oil is improved up to 52% by the periodically direction-switching electric field and graphene nanofluid. As the switching period decreases, the thermal performance of the suspension is enhanced more significantly. Moreover, by analyzing the heat transfer mechanism, the periodically direction-switching electric field causes the nanoparticles to move reciprocally, repeatedly impacting and breaking the boundary layer of the heat exchange surface to enhance the perturbation, thus enhancing the heat transfer effect. Meanwhile, the predicted correlation has been proposed on the basis of influence factors, which are in good agreement with the experimental data.
{"title":"Mixed convective heat transfer characteristics of graphene nanofluid strengthened by periodically direction-switching electric field","authors":"Yanjun Chen, Chenhao Du, Zhoumiao Wang, Deqiang He","doi":"10.1115/1.4063683","DOIUrl":"https://doi.org/10.1115/1.4063683","url":null,"abstract":"Abstract Transformer-oil with low thermal conductivity and large viscosity has poor heat dissipation capability, which leads to the thermal drive failure caused by transient overload. To improve its cooling capability, this paper has proposed firstly the method combined the periodically direction-switching electric field and graphene nanofluid to enhance the mixed convective heat transfer properties of transformer-oil, and analyzed the effects of switching periods, nanofluid concentration, electric field strength, heat flux and Reynolds number on mixed convection heat transfer experimentally. The results show that the heat transfer characteristic of transformer-oil is improved up to 52% by the periodically direction-switching electric field and graphene nanofluid. As the switching period decreases, the thermal performance of the suspension is enhanced more significantly. Moreover, by analyzing the heat transfer mechanism, the periodically direction-switching electric field causes the nanoparticles to move reciprocally, repeatedly impacting and breaking the boundary layer of the heat exchange surface to enhance the perturbation, thus enhancing the heat transfer effect. Meanwhile, the predicted correlation has been proposed on the basis of influence factors, which are in good agreement with the experimental data.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134975110","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}
Abstract In order to increase biogas production during winter months/cold climatic conditions, a self-sustained N-photo-voltaic thermal and flat plate collectors (PVT-FPC) hybrid active heating biogas plant has been analyzed in terms of thermal energy and electrical energy. A general analytical expression for thermal and electrical energy of biogas plant has been derived as a function of climatic and design parameters from one order coupled differential equations. Various photo-voltaic thermal and flat plate collectors (N-PVT-FPC) configurations have been considered for optimizing maximum electrical and thermal energy gain for a given total number of N-PVT-FPC collectors. Based on mathematical computation for Indian cold climatic conditions, it has been found that the photo-voltaic thermal and flat plate collectors (N-PVT-FPC) combination is always better than the flat plate collectors-photo-voltaic thermal (N-FPC-PVT) collector for maximum electrical and thermal energy. Overall exergy analysis of hybrid active heating of biogas plant has also been carried out.
{"title":"Thermal and electrical analysis of N-PVT-FPC hybrid active heating of biogas plant","authors":"GN Tiwari, Rohit Kumar Singh, A S K Sinha","doi":"10.1115/1.4063678","DOIUrl":"https://doi.org/10.1115/1.4063678","url":null,"abstract":"Abstract In order to increase biogas production during winter months/cold climatic conditions, a self-sustained N-photo-voltaic thermal and flat plate collectors (PVT-FPC) hybrid active heating biogas plant has been analyzed in terms of thermal energy and electrical energy. A general analytical expression for thermal and electrical energy of biogas plant has been derived as a function of climatic and design parameters from one order coupled differential equations. Various photo-voltaic thermal and flat plate collectors (N-PVT-FPC) configurations have been considered for optimizing maximum electrical and thermal energy gain for a given total number of N-PVT-FPC collectors. Based on mathematical computation for Indian cold climatic conditions, it has been found that the photo-voltaic thermal and flat plate collectors (N-PVT-FPC) combination is always better than the flat plate collectors-photo-voltaic thermal (N-FPC-PVT) collector for maximum electrical and thermal energy. Overall exergy analysis of hybrid active heating of biogas plant has also been carried out.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134975892","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}
Atalay Yildirim, Özden Agra, Mustafa Kemal Sevindir
Abstract We experimentally investigated the evaporation characteristics of a sessile water droplet on a glass substrate with different surface roughness levels. The influence of five parameters that each have tree levels are evaluated for the evaporation process: substrate temperature, surface roughness, droplet volume, water droplets initial temperature, and inclination angle of the glass substrate. A Taguchi orthogonal array design of L27 is used to determine minimum candidate trial points of the experimental works, and more experiments have been carried out to determine the effects precisely. Then Analysis of Variance has been used to evaluate the evaporation times for the sessile droplets. The results show that evaporation times decreases with increasing substrate temperatures, increasing inclination angle of the substrate, and increasing initial water droplets temperatures while evaporation times increases with increasing surface roughness and increasing droplet volumes.A linear regression fit derived via ANOVA analysis for the evaporation time and the best mean deviation found to be 10% from the experiments. The experimental results compared to the literature and derived correlations. And the proposed correlation has given good results considering experimental and literature data.
{"title":"Experimental Investigation Of The Water Droplets Evaporation On An Inclined Surfaces By Taguchi And ANOVA Optimization Analysis","authors":"Atalay Yildirim, Özden Agra, Mustafa Kemal Sevindir","doi":"10.1115/1.4063681","DOIUrl":"https://doi.org/10.1115/1.4063681","url":null,"abstract":"Abstract We experimentally investigated the evaporation characteristics of a sessile water droplet on a glass substrate with different surface roughness levels. The influence of five parameters that each have tree levels are evaluated for the evaporation process: substrate temperature, surface roughness, droplet volume, water droplets initial temperature, and inclination angle of the glass substrate. A Taguchi orthogonal array design of L27 is used to determine minimum candidate trial points of the experimental works, and more experiments have been carried out to determine the effects precisely. Then Analysis of Variance has been used to evaluate the evaporation times for the sessile droplets. The results show that evaporation times decreases with increasing substrate temperatures, increasing inclination angle of the substrate, and increasing initial water droplets temperatures while evaporation times increases with increasing surface roughness and increasing droplet volumes.A linear regression fit derived via ANOVA analysis for the evaporation time and the best mean deviation found to be 10% from the experiments. The experimental results compared to the literature and derived correlations. And the proposed correlation has given good results considering experimental and literature data.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134975263","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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