Lithium-ion batteries (LiBs) are widely used in electric vehicles due to their high energy and power density. The operating temperature has a significant impact on the thermal performance and longevity of LiBs. The thermal performance of an air-cooled battery module containing sixteen (4S4P) high-energy density LiBs has been investigated through a series of experiments and numerical simulations. At varying transverse and longitudinal cell spacing, airflow rates, ambient temperatures, and discharge C-rates, the thermal performance of a battery module with aligned battery cells was analysed. For the thermal performance evaluation, the average temperature rise, temperature non-uniformity, and maximum temperature of the module's battery cells are utilised. During discharge cycles, the rate of temperature increase is linear but becomes nonlinear at the end of the discharge cycle. In this design of the battery module, a minimum cell separation of 4 mm is necessary to limit maximum temperature and temperature non-uniformity to safe battery thermal management temperatures. The thermal performance was significantly affected by the airflow rate. Increasing airflow rate decreases temperature but increases pressure drop substantially. The maximum cell temperature is greatly affected by the inlet air temperature, increasing from 62.8 °C to 76.6 °C when the inlet air temperature is increased from 30 °C to 45 °C. At high ambient temperatures (over 40 °C), LiB temperatures exceed permissible limits, and air cooling becomes inadequate. This study examines the thermal performance of an air-cooled battery module working at high temperatures.
{"title":"Experimental and numerical investigation of thermal performance of an air-cooled battery module under high ambient temperature conditions","authors":"D. K. Sharma, A. Prabhakar","doi":"10.1115/1.4062589","DOIUrl":"https://doi.org/10.1115/1.4062589","url":null,"abstract":"\u0000 Lithium-ion batteries (LiBs) are widely used in electric vehicles due to their high energy and power density. The operating temperature has a significant impact on the thermal performance and longevity of LiBs. The thermal performance of an air-cooled battery module containing sixteen (4S4P) high-energy density LiBs has been investigated through a series of experiments and numerical simulations. At varying transverse and longitudinal cell spacing, airflow rates, ambient temperatures, and discharge C-rates, the thermal performance of a battery module with aligned battery cells was analysed. For the thermal performance evaluation, the average temperature rise, temperature non-uniformity, and maximum temperature of the module's battery cells are utilised. During discharge cycles, the rate of temperature increase is linear but becomes nonlinear at the end of the discharge cycle. In this design of the battery module, a minimum cell separation of 4 mm is necessary to limit maximum temperature and temperature non-uniformity to safe battery thermal management temperatures. The thermal performance was significantly affected by the airflow rate. Increasing airflow rate decreases temperature but increases pressure drop substantially. The maximum cell temperature is greatly affected by the inlet air temperature, increasing from 62.8 °C to 76.6 °C when the inlet air temperature is increased from 30 °C to 45 °C. At high ambient temperatures (over 40 °C), LiB temperatures exceed permissible limits, and air cooling becomes inadequate. This study examines the thermal performance of an air-cooled battery module working at high temperatures.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"19 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87312854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Cooled Cooling Air (CCA) technology is an effective approach in an advanced gas turbine engine to reduce the temperature of the highly compressed air and recover its cooling capacity, using the onboard fuel as coolant. Numerical studies have been conducted in this paper to analyze heat exchange between the supercritical-pressure aviation kerosene and the compressed high-temperature air in a double-pipe counter flow configuration, intended for the CCA applications. The thermal oxidative reactions and surface coking of kerosene are taken into consideration using a multi-step reaction mechanism. Results indicate that the air tube diameter should be determined to obtain not only the improved overall thermal performance on the air side, in terms of both heat transfer and pressure loss, but also the properly limited maximum temperature on the fuel side to avoid the strong pyrolytic chemical reactions of kerosene and the resulting fast surface coking process. Although the ribbed and dimpled surface structures are both able to improve the overall thermal performance in the fuel tube and increase the bulk air temperature reduction, they also lead to the increased surface coking rate from the thermal oxidative reactions of kerosene. The thermal oxidative coking process would gradually increase heat transfer barrier and cause an adverse effect on the long-term operation of a heat exchanger. The numerical results obtained in this paper should have fundamental and practical importance in the CCA applications.
{"title":"Computational study of heat exchange and thermal oxidative coking of supercritical-pressure kerosene with compressed air in counter flows","authors":"Ting Tan, Yuan Yuan, Xing Sun, H. Meng","doi":"10.1115/1.4062558","DOIUrl":"https://doi.org/10.1115/1.4062558","url":null,"abstract":"\u0000 The Cooled Cooling Air (CCA) technology is an effective approach in an advanced gas turbine engine to reduce the temperature of the highly compressed air and recover its cooling capacity, using the onboard fuel as coolant. Numerical studies have been conducted in this paper to analyze heat exchange between the supercritical-pressure aviation kerosene and the compressed high-temperature air in a double-pipe counter flow configuration, intended for the CCA applications. The thermal oxidative reactions and surface coking of kerosene are taken into consideration using a multi-step reaction mechanism. Results indicate that the air tube diameter should be determined to obtain not only the improved overall thermal performance on the air side, in terms of both heat transfer and pressure loss, but also the properly limited maximum temperature on the fuel side to avoid the strong pyrolytic chemical reactions of kerosene and the resulting fast surface coking process. Although the ribbed and dimpled surface structures are both able to improve the overall thermal performance in the fuel tube and increase the bulk air temperature reduction, they also lead to the increased surface coking rate from the thermal oxidative reactions of kerosene. The thermal oxidative coking process would gradually increase heat transfer barrier and cause an adverse effect on the long-term operation of a heat exchanger. The numerical results obtained in this paper should have fundamental and practical importance in the CCA applications.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"130 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80250697","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}
Qiuyang Tao, Minghui Wei, Hongjun Chen, Aihua Deng, Yilin He
As the depth of oil and gas exploration increases, downhole electronics face the threat of high temperature failure. At present, passive cooling technology has the problem of short working time, while active cooling technology has low energy utilization. This paper presents a thermal management system of vapor compression with a combination of active and passive cooling. The system uses insulation materials to isolate the high-temperature environment, thermally conductive silicone grease to strengthen the heat exchange in the evaporator, and vapor compression refrigeration cycles to absorb internal heat.The coefficient of performance (COP), exergy destruction and exergy efficiency of octane, nonane and cyclohexane as refrigerants were examined, and the effects of different insulation materials on refrigeration performance were studied from both theoretical and numerical perspectives. The results showed that cyclohexane exhibited the best cooling capacity with a COP of 1.296 and a exergy efficiency of 49.21%. The thermal management system cooling performance is optimal when the insulation material is a vacuum flask, with an effective cooling capacity of 121.7W.
{"title":"Thermal management system of vapor compression for downhole instrument","authors":"Qiuyang Tao, Minghui Wei, Hongjun Chen, Aihua Deng, Yilin He","doi":"10.1115/1.4062555","DOIUrl":"https://doi.org/10.1115/1.4062555","url":null,"abstract":"\u0000 As the depth of oil and gas exploration increases, downhole electronics face the threat of high temperature failure. At present, passive cooling technology has the problem of short working time, while active cooling technology has low energy utilization. This paper presents a thermal management system of vapor compression with a combination of active and passive cooling. The system uses insulation materials to isolate the high-temperature environment, thermally conductive silicone grease to strengthen the heat exchange in the evaporator, and vapor compression refrigeration cycles to absorb internal heat.The coefficient of performance (COP), exergy destruction and exergy efficiency of octane, nonane and cyclohexane as refrigerants were examined, and the effects of different insulation materials on refrigeration performance were studied from both theoretical and numerical perspectives. The results showed that cyclohexane exhibited the best cooling capacity with a COP of 1.296 and a exergy efficiency of 49.21%. The thermal management system cooling performance is optimal when the insulation material is a vacuum flask, with an effective cooling capacity of 121.7W.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"34 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91296208","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}
C. Wüstenhagen, C. Domnick, K. John, M. Bruschewski, S. Grundmann
The optimal Reynolds-Averaged-Navier Stokes (RANS) turbulence model to be used in a Computational Fluid Dynamics (CFD) simulation varies depending on the application. Conventionally, the model is selected from benchmark tests and experience, but its performance is difficult to predict. For this reason, this study presents a cost-effective CFD validation routine, which uses three-dimensional experimental velocity data obtained in replicas of the specific flow system. Magnetic Resonance Velocimetry (MRV) is used as the measurement technique. Since the objective is only the validation of the turbulence model, the experiment and the simulation are performed with simplified flow conditions, hence, stationary iso-thermal iso-volumetric flow without inertial forces. The routine applies a data matching routine to align the two three-dimensional data sets before they are interpolated on a common grid. Various error metrics are presented, which provide the degree of the CFD modelling error and indicate its source. For demonstration, the validation routine is used to evaluate RANS-CFD results of a three-pass internal cooling system of a high-pressure turbine airfoil used in a small industrial gas turbine. The simulations are performed with the eddy-viscosity based turbulence model k-w SST and the Reynolds-Stress SSG, and BSL-EARSM turbulence models. The results indicate strong local errors in the examined turbulence models. None of the models performed well enough, underlining that every RANS-CFD application needs to be validated.
{"title":"MRV Measurements of Internal Blade Cooling Flow and CFD Validation by Data Matching with the Experimental Data","authors":"C. Wüstenhagen, C. Domnick, K. John, M. Bruschewski, S. Grundmann","doi":"10.1115/1.4062556","DOIUrl":"https://doi.org/10.1115/1.4062556","url":null,"abstract":"\u0000 The optimal Reynolds-Averaged-Navier Stokes (RANS) turbulence model to be used in a Computational Fluid Dynamics (CFD) simulation varies depending on the application. Conventionally, the model is selected from benchmark tests and experience, but its performance is difficult to predict. For this reason, this study presents a cost-effective CFD validation routine, which uses three-dimensional experimental velocity data obtained in replicas of the specific flow system. Magnetic Resonance Velocimetry (MRV) is used as the measurement technique. Since the objective is only the validation of the turbulence model, the experiment and the simulation are performed with simplified flow conditions, hence, stationary iso-thermal iso-volumetric flow without inertial forces. The routine applies a data matching routine to align the two three-dimensional data sets before they are interpolated on a common grid. Various error metrics are presented, which provide the degree of the CFD modelling error and indicate its source. For demonstration, the validation routine is used to evaluate RANS-CFD results of a three-pass internal cooling system of a high-pressure turbine airfoil used in a small industrial gas turbine. The simulations are performed with the eddy-viscosity based turbulence model k-w SST and the Reynolds-Stress SSG, and BSL-EARSM turbulence models. The results indicate strong local errors in the examined turbulence models. None of the models performed well enough, underlining that every RANS-CFD application needs to be validated.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"19 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88012342","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}
A major current focus of refrigeration and air conditioning research is energy usage and environmental impact. The ejector-based refrigeration system is a technology that, it is hoped, can save power while using environment-friendly refrigerants to reduce any adverse effects on nature. The reduction of compressor dependency is the first and essential aim of this study; the second is to demonstrate the replacement of R134a with the new refrigerant R1234yf in motor vehicle air conditioning systems, establishing the benefits of employing R1234yf in conjunction with a Hybrid Air Conditioning System. In such a system the engine's exhaust gases are used to operate the ejector. A numerical model has been developed which estimates the ejector entrainment ratio at a specified spindle and primary nozzle exit position. A theoretical model using energy and exergy analysis illustrates the impact of hybrid systems on performance under different operating conditions (i.e., engine exhaust, ambient air, and evaporator temperatures). At a specified exhaust temperature, a detailed comparison has been conducted between a current air-conditioning system with R134a and the hybrid system with R1234yf. It was found that the R1234yf hybrid system reduced compressor energy consumption by 44.43% and operating exhaust heat levels by 12.79%. The COP was increased by 41.42%, while the exergetic efficiency was reduced from 37.14% to 13.85%. Cooling capacity dropped by 12.73%. The hybrid air-conditioning system based on R1234yf demonstrated tremendous potential for improving vehicle air-conditioning system efficiency.
{"title":"Energy and Exergy Analysis of an Automobile Hybrid Ejector Refrigeration System Utilizing its Exhaust Waste Heat","authors":"Karim Abbady, N. Al-Mutawa, A. Almutairi","doi":"10.1115/1.4062557","DOIUrl":"https://doi.org/10.1115/1.4062557","url":null,"abstract":"\u0000 A major current focus of refrigeration and air conditioning research is energy usage and environmental impact. The ejector-based refrigeration system is a technology that, it is hoped, can save power while using environment-friendly refrigerants to reduce any adverse effects on nature. The reduction of compressor dependency is the first and essential aim of this study; the second is to demonstrate the replacement of R134a with the new refrigerant R1234yf in motor vehicle air conditioning systems, establishing the benefits of employing R1234yf in conjunction with a Hybrid Air Conditioning System. In such a system the engine's exhaust gases are used to operate the ejector. A numerical model has been developed which estimates the ejector entrainment ratio at a specified spindle and primary nozzle exit position. A theoretical model using energy and exergy analysis illustrates the impact of hybrid systems on performance under different operating conditions (i.e., engine exhaust, ambient air, and evaporator temperatures). At a specified exhaust temperature, a detailed comparison has been conducted between a current air-conditioning system with R134a and the hybrid system with R1234yf. It was found that the R1234yf hybrid system reduced compressor energy consumption by 44.43% and operating exhaust heat levels by 12.79%. The COP was increased by 41.42%, while the exergetic efficiency was reduced from 37.14% to 13.85%. Cooling capacity dropped by 12.73%. The hybrid air-conditioning system based on R1234yf demonstrated tremendous potential for improving vehicle air-conditioning system efficiency.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"33 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84433187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the findings of numerical and experimental investigations into the forced convection heat transfer from horizontal surfaces with straight rectangular fins at Reynolds numbers ranging from 23600 to 150000. A test set-up was constructed to measure the heat transfer rate from a horizontal surface with a constant number of fins, fin width and fin length under different flow conditions. Two-dimensional numerical analyses were performed to observe the heat transfer and flow behaviour using a computer program developed based on the OpenFOAM platform. The code developed was verified by comparing the numerical results with the experimental results. The effect of geometrical parameters on heat transfer coefficient and Nusselt number were investigated for different fin height and width ratios. Numerical results show that one way to increase heat transfer by modifying the fin structure geometrical parameters. With the help of the obtained results, a correlation for Nusselt number was developed and presented for steady-state, turbulent flows over rectangular fin arrays for Reynolds number ranging from 23600 to 150000, Prandtl number ranging from 0.705 to 5.41, for fin height ratios h/H ranging from 0.166 to 0.333, and fin thickness to fin height ratios (t/h) between of 0.066 and 0.20. The correlation developed predicts the Nusselt number with a relative RMS error of 0.36%.
{"title":"PERFORMANCE OPTIMIZATION OF FINNED SURFACES BASED ON THE EXPERIMENTAL AND NUMERICAL STUDY","authors":"Eyup Kocak, H. Turkoglu, Ulku Ece Aylı","doi":"10.1115/1.4062554","DOIUrl":"https://doi.org/10.1115/1.4062554","url":null,"abstract":"\u0000 This paper presents the findings of numerical and experimental investigations into the forced convection heat transfer from horizontal surfaces with straight rectangular fins at Reynolds numbers ranging from 23600 to 150000. A test set-up was constructed to measure the heat transfer rate from a horizontal surface with a constant number of fins, fin width and fin length under different flow conditions. Two-dimensional numerical analyses were performed to observe the heat transfer and flow behaviour using a computer program developed based on the OpenFOAM platform. The code developed was verified by comparing the numerical results with the experimental results. The effect of geometrical parameters on heat transfer coefficient and Nusselt number were investigated for different fin height and width ratios. Numerical results show that one way to increase heat transfer by modifying the fin structure geometrical parameters. With the help of the obtained results, a correlation for Nusselt number was developed and presented for steady-state, turbulent flows over rectangular fin arrays for Reynolds number ranging from 23600 to 150000, Prandtl number ranging from 0.705 to 5.41, for fin height ratios h/H ranging from 0.166 to 0.333, and fin thickness to fin height ratios (t/h) between of 0.066 and 0.20. The correlation developed predicts the Nusselt number with a relative RMS error of 0.36%.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"241 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85150341","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}
In this paper the experimental investigation of a Boeing 737 aircraft Environmental Control System (ECS) passenger air conditioner (PACK) has been reported. The PACK is the heart of the ECS that conditions bleed air prior to supplying it to the cabin and avionics bay. Its capability to mask fault occurrences has resulted in increased unscheduled maintenance of the system. As such it has been a key research topic to understand PACK performance characteristics in order to support an accurate diagnostic solution. This paper is a continuation of the authors' work on the development of a systematically derived PACK simulation model and reports the overall development and qualification of a novel in-situ ground test facility (GTF) for the experimental investigation of a B737-400 aircraft PACK under various operating modes, including the effect of trim air system. The developed GTF enables the acquisition of the temperature, pressure and mass flow data throughout the PACK. The overall process of instrumentation selection, installation, sensor uncertainty, and testing in terms of data repeatability and consistency has been reported. The acquired data is then employed to conduct a V&V of the SESAC simulation framework. The reported research work therefore enables the advancement in the level of scientific understanding corresponding to the ECS PACK operation under real operating conditions, and therefore supports the development of a robust simulation framework.
{"title":"Development of a Novel Ground Test Facility for Aircraft Environmental Control System","authors":"S. H. Chowdhury, A. Fakhre, I. Jennions","doi":"10.1115/1.4062553","DOIUrl":"https://doi.org/10.1115/1.4062553","url":null,"abstract":"\u0000 In this paper the experimental investigation of a Boeing 737 aircraft Environmental Control System (ECS) passenger air conditioner (PACK) has been reported. The PACK is the heart of the ECS that conditions bleed air prior to supplying it to the cabin and avionics bay. Its capability to mask fault occurrences has resulted in increased unscheduled maintenance of the system. As such it has been a key research topic to understand PACK performance characteristics in order to support an accurate diagnostic solution. This paper is a continuation of the authors' work on the development of a systematically derived PACK simulation model and reports the overall development and qualification of a novel in-situ ground test facility (GTF) for the experimental investigation of a B737-400 aircraft PACK under various operating modes, including the effect of trim air system. The developed GTF enables the acquisition of the temperature, pressure and mass flow data throughout the PACK. The overall process of instrumentation selection, installation, sensor uncertainty, and testing in terms of data repeatability and consistency has been reported. The acquired data is then employed to conduct a V&V of the SESAC simulation framework. The reported research work therefore enables the advancement in the level of scientific understanding corresponding to the ECS PACK operation under real operating conditions, and therefore supports the development of a robust simulation framework.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"33 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86757130","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}
Energy efficient air cooling systems are always in demand. Direct evaporative coolers are used to reduce air temperature in summer, they are energy saving and has low cost, but in hot and humid areas, they produce almost uncomfortable environment. Alternatively, modified indirect evaporative coolers with different technical configuration can produce better thermal output to cool or pre-cool air for residential applications. This paper presents a simple thermodynamic approach developed to analyze, for comparison, the behavior of conventional and regenerative indirect evaporative coolers that comprising different process structure. The analysis is based on the energy balance of each component of the coolers to consider which is more applicable for further modification. Similar performance cross-flow heat exchangers with separate air washers are adopted for both units. The two coolers are subjected to the same general summer operating conditions in terms of primary air temperature, specific humidity and flow rate. The results showed that the conventional indirect evaporative cooler provided better cooling performance in terms of all thermal comparison parameters. Thus, it deserves priority attention for the purpose of further development and additional improvement of performance.
{"title":"An approach to analyzing and comparing the cooling performance of two indirect evaporative cooler designs","authors":"Braihan Abdulwadood","doi":"10.1115/1.4062501","DOIUrl":"https://doi.org/10.1115/1.4062501","url":null,"abstract":"\u0000 Energy efficient air cooling systems are always in demand. Direct evaporative coolers are used to reduce air temperature in summer, they are energy saving and has low cost, but in hot and humid areas, they produce almost uncomfortable environment. Alternatively, modified indirect evaporative coolers with different technical configuration can produce better thermal output to cool or pre-cool air for residential applications. This paper presents a simple thermodynamic approach developed to analyze, for comparison, the behavior of conventional and regenerative indirect evaporative coolers that comprising different process structure. The analysis is based on the energy balance of each component of the coolers to consider which is more applicable for further modification. Similar performance cross-flow heat exchangers with separate air washers are adopted for both units. The two coolers are subjected to the same general summer operating conditions in terms of primary air temperature, specific humidity and flow rate. The results showed that the conventional indirect evaporative cooler provided better cooling performance in terms of all thermal comparison parameters. Thus, it deserves priority attention for the purpose of further development and additional improvement of performance.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"40 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81391124","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}
In this study, an attempt has been made to carry out a numerical investigation using water based Al2O3 nanofluid, flowing through a circular tube under constant inlet temperature and constant heat flux condition in a laminar flow regime. The water-based Al2O3 nanofluid is used in a circular plane tube first and then this process is repeated for the same tube with a twisted tape inserted having twist ratio (H/w) of 1.85 at Reynolds number ranging from 680 to 2030. For the numerical analysis, ANSYS FLUENT is used to solve 3-dimensional conservation equations of mass, momentum and energy. The simulated results indicate that when twisted tape is used, heat transfer rates increase significantly with the use of nanofluid. In case of nanofluid with the plane tube, only 10-24% enhancement in heat transfer rate is noted. On the other hand, almost 27-45% increase in heat transfer is observed compared to that with only water when twisted tape is inserted into it. It is also noticed that the friction factor value increases with the increase in volume fraction. But the effect of heat transfer is more significant than the other factors. The best thermo-hydraulic performance factor achieved is 2.1 using nanofluids with 5% volume fraction at high Reynolds number when twisted tape is also inserted.
{"title":"Heat Transfer Enhancement in Laminar Pipe Flow Using Al2O3-Water Nanofluid and Twisted Tape Inserts","authors":"Santinath Bairagi, Ranendra Roy, B. Mandal","doi":"10.1115/1.4062433","DOIUrl":"https://doi.org/10.1115/1.4062433","url":null,"abstract":"\u0000 In this study, an attempt has been made to carry out a numerical investigation using water based Al2O3 nanofluid, flowing through a circular tube under constant inlet temperature and constant heat flux condition in a laminar flow regime. The water-based Al2O3 nanofluid is used in a circular plane tube first and then this process is repeated for the same tube with a twisted tape inserted having twist ratio (H/w) of 1.85 at Reynolds number ranging from 680 to 2030. For the numerical analysis, ANSYS FLUENT is used to solve 3-dimensional conservation equations of mass, momentum and energy. The simulated results indicate that when twisted tape is used, heat transfer rates increase significantly with the use of nanofluid. In case of nanofluid with the plane tube, only 10-24% enhancement in heat transfer rate is noted. On the other hand, almost 27-45% increase in heat transfer is observed compared to that with only water when twisted tape is inserted into it. It is also noticed that the friction factor value increases with the increase in volume fraction. But the effect of heat transfer is more significant than the other factors. The best thermo-hydraulic performance factor achieved is 2.1 using nanofluids with 5% volume fraction at high Reynolds number when twisted tape is also inserted.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"6 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81899025","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}
Shaohua Han, Runsheng Zhang, Jiangjiang Xing, Yu Song, Na An, Tianyi Huo, Leping Zhou, Li Li, H. Zhang, Xiaoze Du
Swirl cooling can provide effective protection for the turbine vane leading edge (LE). In this paper, a swirl cooling model for improving the turbine vane heat transfer is established. The model includes the high-temperature mainstream region, LE region, and swirl cooling region. The conjugate heat transfer (CHT) method is used to examine the influence of wall structures on swirl cooling. Then, the best surface structure in the studied range is selected to further analyze the impact of the coolant inlet mass flow. The results show that the circumferential micro-ribs structure has a more excellent performance in both fluid flow and cooling performance. The hindering effect of the micro-ribs can effectively avoid the development of axial cross-flow, thus enhancing the heat transfer with a small friction loss increment and providing a lower surface temperature and more uniform temperature distribution. When the inlet mass flow rate improves, the thermal performance factor increases and the LE temperature decreases gradually. Under the same pumping power condition, the circumferential micro-ribs structure has higher heat transfer efficiency. This investigation can provide a new design for further improving the thermal performance of swirl cooling for turbine vanes.
{"title":"Flow and conjugate heat transfer of swirl chamber with micro-ribs in turbine vane leading edge","authors":"Shaohua Han, Runsheng Zhang, Jiangjiang Xing, Yu Song, Na An, Tianyi Huo, Leping Zhou, Li Li, H. Zhang, Xiaoze Du","doi":"10.1115/1.4062434","DOIUrl":"https://doi.org/10.1115/1.4062434","url":null,"abstract":"\u0000 Swirl cooling can provide effective protection for the turbine vane leading edge (LE). In this paper, a swirl cooling model for improving the turbine vane heat transfer is established. The model includes the high-temperature mainstream region, LE region, and swirl cooling region. The conjugate heat transfer (CHT) method is used to examine the influence of wall structures on swirl cooling. Then, the best surface structure in the studied range is selected to further analyze the impact of the coolant inlet mass flow. The results show that the circumferential micro-ribs structure has a more excellent performance in both fluid flow and cooling performance. The hindering effect of the micro-ribs can effectively avoid the development of axial cross-flow, thus enhancing the heat transfer with a small friction loss increment and providing a lower surface temperature and more uniform temperature distribution. When the inlet mass flow rate improves, the thermal performance factor increases and the LE temperature decreases gradually. Under the same pumping power condition, the circumferential micro-ribs structure has higher heat transfer efficiency. This investigation can provide a new design for further improving the thermal performance of swirl cooling for turbine vanes.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"14 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81766057","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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