Pub Date : 2024-04-01DOI: 10.1615/heattransres.2024049821
Digvijay Ronge, Prashant Pawar
Micro Heat Sinks (MHS) are becoming integral part of microelectronics nowadays because of their ability to cool the tiny components which generate high heat flux. In this study, an electronic chip with a high heat flux of 100 W/cm² is cooled with the help of a MHS device which has repetitive patterns of obstacles of various shapes in the flow of cooling medium. Numerical modelling of all MHSs were performed using a Computational Fluid Dynamics (CFD) solver and the pattern, which gives better thermo-hydraulic performance, was selected for optimization. A parametric study was performed with various obstacle sizes, distance between obstacles and flow rate of cooling medium for maximum temperature of chip and pressure drop. Regression analysis was carried out with Response Surface Method (RSM) between these three design variables and two objective functions, viz. thermal resistance (Rth) and pumping power (Pp). A multi-objective optimization of the MHS was performed using genetic algorithm (GA) and pareto-optimal solutions were obtained. An optimal design was fabricated and the cooling experiment was carried out under optimal flow conditions. The repetitive pattern of obstacles increases the conjugate heat transfer area and helps in improving thermal performance.
{"title":"Optimization of Micro Heat Sink with Repetitive pattern of Obstacles for Electronic Cooling Applications","authors":"Digvijay Ronge, Prashant Pawar","doi":"10.1615/heattransres.2024049821","DOIUrl":"https://doi.org/10.1615/heattransres.2024049821","url":null,"abstract":"Micro Heat Sinks (MHS) are becoming integral part of microelectronics nowadays because of their ability to cool the tiny components which generate high heat flux. In this study, an electronic chip with a high heat flux of 100 W/cm² is cooled with the help of a MHS device which has repetitive patterns of obstacles of various shapes in the flow of cooling medium. Numerical modelling of all MHSs were performed using a Computational Fluid Dynamics (CFD) solver and the pattern, which gives better thermo-hydraulic performance, was selected for optimization. A parametric study was performed with various obstacle sizes, distance between obstacles and flow rate of cooling medium for maximum temperature of chip and pressure drop. Regression analysis was carried out with Response Surface Method (RSM) between these three design variables and two objective functions, viz. thermal resistance (Rth) and pumping power (Pp). A multi-objective optimization of the MHS was performed using genetic algorithm (GA) and pareto-optimal solutions were obtained. An optimal design was fabricated and the cooling experiment was carried out under optimal flow conditions. The repetitive pattern of obstacles increases the conjugate heat transfer area and helps in improving thermal performance.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"68 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140588076","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024051704
Ranjeet Rai, Vikash Kumar, Rashmi Rekha Sahoo
Passive inserts, notably twisted turbulator inserts (TTI) and perforated twisted turbulator inserts (PTTI) loaded with water-based ternary hybrid nanofluid (THNF), are employed in plain tube heat exchangers to enhance thermal performance. The investigation focuses on how THNF replacement inserts will impact energy utilization, exergy consumption, and the environment in the decades to come. Nanoparticles of copper oxide (CuO), aluminum oxide (Al2O3), and titanium oxide (TiO2) are dissolved in water, which functions as the working fluid, and the resulting THNF is injected at three distinct concentrations (0.06%, 0.09%, and 0.12%). Certain aspects of the flow of a control fluid are investigated in terms of energy, exergy, and emissions. The experimental findings demonstrate that utilizing TTI and PTTI in conjunction with THNF substantially enhances the compact air heat exchanger's thermal and hydraulic efficiency. Heat transfer, friction factor, exergy change, and reversibility are greatly improved when turbulator inserts with PTTI and TTI are employed in plain tubes containing 0.12% (v/v) THNF. The CO2 discharge rises by 2.6 to 2.1 when PTTI or TTI turbulator inserts are inserted in the tube's core. Using PTTI with a concentration of 0.12% (v/v) THNF as the working fluid and a tube insert will provide PEC values in the range of 1.075 to 1.04. The thorough examination of heat transfer enhancement, friction factor, exergy efficiency, and environmental effect suggests that PTTI is a better passive device insert for heat transfer efficiency, particularly when combined with 0.12% (v/v) THNF.
{"title":"Energy, Exergy-Emission Performance Investigation of Heat Exchanger with Turbulators Inserts and Ternary Hybrid Nanofluid","authors":"Ranjeet Rai, Vikash Kumar, Rashmi Rekha Sahoo","doi":"10.1615/heattransres.2024051704","DOIUrl":"https://doi.org/10.1615/heattransres.2024051704","url":null,"abstract":"Passive inserts, notably twisted turbulator inserts (TTI) and perforated twisted turbulator inserts (PTTI) loaded with water-based ternary hybrid nanofluid (THNF), are employed in plain tube heat exchangers to enhance thermal performance. The investigation focuses on how THNF replacement inserts will impact energy utilization, exergy consumption, and the environment in the decades to come. Nanoparticles of copper oxide (CuO), aluminum oxide (Al2O3), and titanium oxide (TiO2) are dissolved in water, which functions as the working fluid, and the resulting THNF is injected at three distinct concentrations (0.06%, 0.09%, and 0.12%). Certain aspects of the flow of a control fluid are investigated in terms of energy, exergy, and emissions.\u0000The experimental findings demonstrate that utilizing TTI and PTTI in conjunction with THNF substantially enhances the compact air heat exchanger's thermal and hydraulic efficiency. Heat transfer, friction factor, exergy change, and reversibility are greatly improved when turbulator inserts with PTTI and TTI are employed in plain tubes containing 0.12% (v/v) THNF. The CO2 discharge rises by 2.6 to 2.1 when PTTI or TTI turbulator inserts are inserted in the tube's core. Using PTTI with a concentration of 0.12% (v/v) THNF as the working fluid and a tube insert will provide PEC values in the range of 1.075 to 1.04. The thorough examination of heat transfer enhancement, friction factor, exergy efficiency, and environmental effect suggests that PTTI is a better passive device insert for heat transfer efficiency, particularly when combined with 0.12% (v/v) THNF.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"30 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140300262","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 superheater in the boiler is the key of equipment connecting high-temperature steam to the turbine for power generation. At present, the problems of large variable fluctuations, strong timing coupling and multi-power plant data utilization prevent the temperature, flow and pressure prediction of the boiler superheater. In this paper, a method for predicting the parameters of boiler superheater based on a transfer learning model is proposed, which realizes the joint utilization of data from multiple power plants. The method first collects data from a waste incineration boiler power plant for pre-training the long short-term memory (LSTM)-transformer model, and then completes the transfer learning training on the new power plant. The proposed method has the advantages of high prediction accuracy, good robustness, and more reliable location prediction with drastic changes. The predictions on the test set are within ±5% of the experimental value. Compared with the model not trained by the transfer learning, the proposed method achieves the lowest relative errors for all prediction intervals in the 3 min-15 min range. Compared to the linear regression (LR), support vector regression (SVR) and random forest (RF), the proposed method improve the average absolute percentage error (MAPE) by 30%, 13% and 20%, respectively. Flatter loss sharpness value and better robust performance obtained from the transfer learning method is verified by an experimental verification. Finally, a digital system design for power plants with real-time data visualization monitoring, parameter prediction and fault warning functions are implemented.
{"title":"PREDICTION OF PARAMETERS OF BOILER SUPERHEATER BASED ON TRANSFER LEARNING METHOD","authors":"Shuiguang Tong, Qi Yang, Zheming Tong, Haidan Wang, Xin Chen","doi":"10.1615/heattransres.2024049142","DOIUrl":"https://doi.org/10.1615/heattransres.2024049142","url":null,"abstract":"The superheater in the boiler is the key of equipment connecting high-temperature steam to the turbine for power generation. At present, the problems of large variable fluctuations, strong timing coupling and multi-power plant data utilization prevent the temperature, flow and pressure prediction of the boiler superheater. In this paper, a method for predicting the parameters of boiler superheater based on a transfer learning model is proposed, which realizes the joint utilization of data from multiple power plants. The method first collects data from a waste incineration boiler power plant for pre-training the long short-term memory (LSTM)-transformer model, and then completes the transfer learning training on the new power plant. The proposed method has the advantages of high prediction accuracy, good robustness, and more reliable location prediction with drastic changes. The predictions on the test set are within ±5% of the experimental value. Compared with the model not trained by the transfer learning, the proposed method achieves the lowest relative errors for all prediction intervals in the 3 min-15 min range. Compared to the linear regression (LR), support vector regression (SVR) and random forest (RF), the proposed method improve the average absolute percentage error (MAPE) by 30%, 13% and 20%, respectively. Flatter loss sharpness value and better robust performance obtained from the transfer learning method is verified by an experimental verification. Finally, a digital system design for power plants with real-time data visualization monitoring, parameter prediction and fault warning functions are implemented.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"43 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140108291","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024050089
Irfan UÇKAN, Ahmet Yakın, Rasim Behçet
This study aimed to investigate the exergy variations of five different fuels developed for internal combustion engines. Two of these fuels were newly developed boron-added fuels. In many previous studies, only one dead state temperature was considered for exergy calculations. However, it is important to note that the dead state temperature can vary. Therefore, the impact of changing the dead state temperature on the exergy of the internal combustion engine becomes crucial. In this particular study, the exergy variations of the newly developed boron-additive fuels ES12.5 and MS12.5, as well as gasoline blended with ethanol (E12.5), gasoline blended with methane (M12.5), and pure gasoline (B100) were examined. These variations were analyzed at different dead state temperatures ranging from 273K to 298K. This study focused on examining the detailed changes in the exergy of exhaust gases emitted from the combustion process, specifically at the exhaust outlet, with respect to variations in the dead state temperature. Furthermore, the impact of the dead state temperature on various parameters commonly used in thermodynamic analyses, including Improvement potential, productivity lack, and fuel depletion ratio were investigated.. Through analysis, the study revealed significant variations in the exergy of internal combustion engines when the dead state temperature was altered. These findings emphasized the importance of considering the dead state temperature as a critical factor in understanding and optimizing the exergy performance of internal combustion engines.
{"title":"Investigation of the Effect of Dead State Temperature on the Performance of Boron Added Fuels and Different Fuels Used in an Internal Combustion Engine.","authors":"Irfan UÇKAN, Ahmet Yakın, Rasim Behçet","doi":"10.1615/heattransres.2024050089","DOIUrl":"https://doi.org/10.1615/heattransres.2024050089","url":null,"abstract":"This study aimed to investigate the exergy variations of five different fuels developed for internal combustion engines. Two of these fuels were newly developed boron-added fuels. In many previous studies, only one dead state temperature was considered for exergy calculations. However, it is important to note that the dead state temperature can vary. Therefore, the impact of changing the dead state temperature on the exergy of the internal combustion engine becomes crucial. In this particular study, the exergy variations of the newly developed boron-additive fuels ES12.5 and MS12.5, as well as gasoline blended with ethanol (E12.5), gasoline blended with methane (M12.5), and pure gasoline (B100) were examined. These variations were analyzed at different dead state temperatures ranging from 273K to 298K.\u0000This study focused on examining the detailed changes in the exergy of exhaust gases emitted from the combustion process, specifically at the exhaust outlet, with respect to variations in the dead state temperature. Furthermore, the impact of the dead state temperature on various parameters commonly used in thermodynamic analyses, including Improvement potential, productivity lack, and fuel depletion ratio were investigated.. Through analysis, the study revealed significant variations in the exergy of internal combustion engines when the dead state temperature was altered. These findings emphasized the importance of considering the dead state temperature as a critical factor in understanding and optimizing the exergy performance of internal combustion engines.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"36 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140125200","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024052009
Avinash Jacob Balihar, Arnab Karmakar, Avinash Kumar, Smriti Minj, P L John Sangso
Thermal performance was analyzed based on flow visualization and an image processing technique in a two-phase thermosyphon loop (TPTL) with boiling water as the working fluid at low pressure. The bubble geometries, bubble frequency, and dynamic void fraction were measured using direct image analysis combined with the power spectrum and statistical analysis. At a heating rate of 400 W and a filling ratio of 0.88, the thermal performance of the TPTL was enhanced with a thermal efficiency of 91% and effective thermal conductivity of 43858.84 W m‒1 oC‒1. The enhancement was due to the higher frequency cap bubble flow of 11.2 Hz obtained by the direct flow visualization. The bigger Taylor bubbles with slug flow were examined to contribute to the negative effect on the heat transfer rate due to their film boiling regimes. The detailed analysis reveals the mechanism of bubble flow interacting with thermal performance.
{"title":"Analysis of Thermal Performance in a Two-phase Thermosyphon loop based on Flow Visualization and an Image Processing Technique","authors":"Avinash Jacob Balihar, Arnab Karmakar, Avinash Kumar, Smriti Minj, P L John Sangso","doi":"10.1615/heattransres.2024052009","DOIUrl":"https://doi.org/10.1615/heattransres.2024052009","url":null,"abstract":"Thermal performance was analyzed based on flow visualization and an image processing technique in a two-phase thermosyphon loop (TPTL) with boiling water as the working fluid at low pressure. The bubble geometries, bubble frequency, and dynamic void fraction were measured using direct image analysis combined with the power spectrum and statistical analysis. At a heating rate of 400 W and a filling ratio of 0.88, the thermal performance of the TPTL was enhanced with a thermal efficiency of 91% and effective thermal conductivity of 43858.84 W m‒1 oC‒1. The enhancement was due to the higher frequency cap bubble flow of 11.2 Hz obtained by the direct flow visualization. The bigger Taylor bubbles with slug flow were examined to contribute to the negative effect on the heat transfer rate due to their film boiling regimes. The detailed analysis reveals the mechanism of bubble flow interacting with thermal performance.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"16 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140148958","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 large amount of low- and medium-frequency noise can be found in the engine room of a ship. However, during the development of a fire, vibrations of the air in the engine room at different frequencies can be caused by noise disturbances, and the flow field distribution in the flame zone will be changed, which will affect the combustion characteristics of the pool fire. In this paper, a n-heptane pool with a diameter of 6 cm in a confined space of 1500 mm×1500 mm×1000 mm is used. The effects of noise of 75 dB, 90 dB, 105 dB, and 112 dB at 250 Hz, 700 Hz, and 1000 Hz and the noise of the engine room on the combustion behaviour of the pool fire are studied experimentally. By analysing the variation in fuel mass, flame height, and flame tilt, the results show that the multi-frequency noise significantly affects the combustion characteristics of the pool fire in a confined space. Under the perturbation of noise waves, the mass loss rate of the pool is larger than that of the pool fire when it burns freely, and the mass loss rate is exponentially nonlinearly related to the noise pressure. In general, the flame height gradually decreases with an increasing noise pressure in the engine room. Additionally, a new coupling relationship between the flame height and the noise pressure is established based on the noise motion equation, and it is found that there is a negative exponential between the noise pressure and the flame height. In addition, the flame can tilt under the action of the air particle displacement caused by the noise of the engine room. The noise pressure field formed in the confined space has a restraining effect on the pool fire, and the flame tilt angle gradual
船舶机舱内存在大量中低频噪声。然而，在火灾发展过程中，机舱内的空气会因噪声干扰而产生不同频率的振动，火焰区的流场分布也会发生变化，从而影响池火的燃烧特性。本文在 1500 mm×1500 mm×1000 mm 的密闭空间中使用了直径为 6 cm 的正庚烷池。实验研究了频率分别为 250 Hz、700 Hz 和 1000 Hz 的 75 dB、90 dB、105 dB 和 112 dB 的噪声以及机房噪声对池火燃烧行为的影响。通过分析燃料质量、火焰高度和火焰倾斜度的变化，结果表明多频噪声对密闭空间中池塘火的燃烧特性有显著影响。在噪声波的扰动下，池火的质量损失率大于自由燃烧时的质量损失率，且质量损失率与噪声压力呈指数非线性关系。一般来说，机房内的火焰高度会随着噪声压力的增加而逐渐降低。此外，还根据噪声运动方程建立了火焰高度与噪声压力之间的新耦合关系，发现噪声压力与火焰高度之间存在负指数关系。此外，在机房噪声引起的空气粒子位移作用下，火焰会发生倾斜。密闭空间内形成的噪声压力场对池火有抑制作用，火焰倾斜角逐渐减小。
{"title":"Study on the Influence of Multi-Frequency Noise on the Combustion Characteristics of Pool Fires in Ship Engine Rooms","authors":"Zhilin Yuan, Liang Wang, Jiasheng Cao, Yunfeng Yan, Jiaqi Dong, Bingxia Liu, Shuaijun Wang","doi":"10.1615/heattransres.2024051639","DOIUrl":"https://doi.org/10.1615/heattransres.2024051639","url":null,"abstract":"A large amount of low- and medium-frequency noise can be found in the engine room of a ship. However, during the development of a fire, vibrations of the air in the engine room at different frequencies can be caused by noise disturbances, and the flow field distribution in the flame zone will be changed, which will affect the combustion characteristics of the pool fire. In this paper, a n-heptane pool with a diameter of 6 cm in a confined space of 1500 mm×1500 mm×1000 mm is used. The effects of noise of 75 dB, 90 dB, 105 dB, and 112 dB at 250 Hz, 700 Hz, and 1000 Hz and the noise of the engine room on the combustion behaviour of the pool fire are studied experimentally. By analysing the variation in fuel mass, flame height, and flame tilt, the results show that the multi-frequency noise significantly affects the combustion characteristics of the pool fire in a confined space. Under the perturbation of noise waves, the mass loss rate of the pool is larger than that of the pool fire when it burns freely, and the mass loss rate is exponentially nonlinearly related to the noise pressure. In general, the flame height gradually decreases with an increasing noise pressure in the engine room. Additionally, a new coupling relationship between the flame height and the noise pressure is established based on the noise motion equation, and it is found that there is a negative exponential between the noise pressure and the flame height. In addition, the flame can tilt under the action of the air particle displacement caused by the noise of the engine room. The noise pressure field formed in the confined space has a restraining effect on the pool fire, and the flame tilt angle gradual","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"228 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140032466","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024051558
Yanfen Xu, kaihua zhang, Kun Yu, Yufang Liu
Accurate temperature monitoring of heat transfer tube is crucial for safe and efficient operation of nuclear power plant, and radiation thermometer is a common method used for this purpose. This paper thoroughly introduces the measurement principle of the radiation thermometer with an operation wavelength range of 8 - 14 μm. The spectral emissivity of Ni-based alloy DD6 under argon condition is measured using an emissivity measurement setup equipped with a Fourier-transform infrared (FTIR) spectrometer. By integrating the spectral emissivity in the working wavelength range, the spectral band emissivity can be calculated to enhance the accuracy of calculative results obtained by radiation thermometer. And curve of the spectral band emissivity with temperature can be accurately described by nonlinear model. The radiation and corrected temperatures are compared with the temperatures obtained by a K-type thermocouple to verify the availability of the spectral band emissivity obtained by fitting the nonlinear model. The temperature comparison results demonstrate that the corrected temperatures are closer to the true temperature than the radiation temperature, with a maximum temperature deviation of only 4.38 ℃. The combined uncertainty of true temperature measurement by radiation thermometer is less than 3.6 %.
{"title":"Temperature correction method of radiation thermometer based on the nonlinear model fitted from spectral emissivity measurements of Ni-based alloy","authors":"Yanfen Xu, kaihua zhang, Kun Yu, Yufang Liu","doi":"10.1615/heattransres.2024051558","DOIUrl":"https://doi.org/10.1615/heattransres.2024051558","url":null,"abstract":"Accurate temperature monitoring of heat transfer tube is crucial for safe and efficient operation of nuclear power plant, and radiation thermometer is a common method used for this purpose. This paper thoroughly introduces the measurement principle of the radiation thermometer with an operation wavelength range of 8 - 14 μm. The spectral emissivity of Ni-based alloy DD6 under argon condition is measured using an emissivity measurement setup equipped with a Fourier-transform infrared (FTIR) spectrometer. By integrating the spectral emissivity in the working wavelength range, the spectral band emissivity can be calculated to enhance the accuracy of calculative results obtained by radiation thermometer. And curve of the spectral band emissivity with temperature can be accurately described by nonlinear model. The radiation and corrected temperatures are compared with the temperatures obtained by a K-type thermocouple to verify the availability of the spectral band emissivity obtained by fitting the nonlinear model. The temperature comparison results demonstrate that the corrected temperatures are closer to the true temperature than the radiation temperature, with a maximum temperature deviation of only 4.38 ℃. The combined uncertainty of true temperature measurement by radiation thermometer is less than 3.6 %.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"85 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140170545","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024051577
Hengyu Qu, Binfan Jiang, Xiangjun Liu, Dehong Xia
Flue gas from periodic furnaces with large temperature fluctuation is difficult to be recovered by regular heat exchangers. To recover that unstable waste heat, a Temperature Pre-Rectifier (TPR) with honeycombed structure is developed to smooth down the temperature fluctuation by continuous heat-storing and releasing. A three-dimensional model with unsteady flow and heat transfer is constructed to analyze the heat transfer process. Temperature rectification rate η is defined to quantify the smoothing-down effect of temperature fluctuation. The η exhibit the most efficient performance when relative scale (s/δ) is 1.0. The optimized honeycomb size sopt increases exponentially with the inlet temperature fluctuation intensity ξinlet. The η is increased with dimensionless length l*. TPR with segmented structure (s and δ decreased in each segment) can enhance the η with relatively shorter length. Three-segmented structure with a proportion of 0.18:0.33:0.49 can achieve η higher than 0.947, which is recommended for application. Industrial experiments verified that the temperature fluctuation is rectified from 568~1709 K to 1089~1174 K (η = 0.926). A new perspective on waste heat recovery of periodic flue gas based on TPR is provided, and enhancing the efficiency of TPR may be a future challenge.
{"title":"A temperature pre-rectifier with continuous heat storage and release for waste heat recovery from periodic flue gas","authors":"Hengyu Qu, Binfan Jiang, Xiangjun Liu, Dehong Xia","doi":"10.1615/heattransres.2024051577","DOIUrl":"https://doi.org/10.1615/heattransres.2024051577","url":null,"abstract":"Flue gas from periodic furnaces with large temperature fluctuation is difficult to be recovered by regular heat exchangers. To recover that unstable waste heat, a Temperature Pre-Rectifier (TPR) with honeycombed structure is developed to smooth down the temperature fluctuation by continuous heat-storing and releasing. A three-dimensional model with unsteady flow and heat transfer is constructed to analyze the heat transfer process. Temperature rectification rate η is defined to quantify the smoothing-down effect of temperature fluctuation. The η exhibit the most efficient performance when relative scale (s/δ) is 1.0. The optimized honeycomb size sopt increases exponentially with the inlet temperature fluctuation intensity ξinlet. The η is increased with dimensionless length l*. TPR with segmented structure (s and δ decreased in each segment) can enhance the η with relatively shorter length. Three-segmented structure with a proportion of 0.18:0.33:0.49 can achieve η higher than 0.947, which is recommended for application. Industrial experiments verified that the temperature fluctuation is rectified from 568~1709 K to 1089~1174 K (η = 0.926). A new perspective on waste heat recovery of periodic flue gas based on TPR is provided, and enhancing the efficiency of TPR may be a future challenge.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"10 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140047164","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}
Pub Date : 2024-03-01DOI: 10.1615/heattransres.2024052712
MAN AZAD
The solar air heater is a very simple and economical device, but its thermal performance is quite poor. The thermal performance of a solar air heater can be enhanced by increasing the heat transfer between absorber plates and blowing air. Applying artificial roughness to the absorber plate is a unique method for improving the thermal performance of solar air heaters compared to other methods. In this study, diagonally chamfered cuboids were used as roughness elements to investigate the enhancement in the performance of a solar air heater. This roughness is achieved by attaching diagonally chamfered cuboids to the surface of the absorber plate. A thorough experimental investigation was carried out to examine how this roughness affects the perfor-mance of solar air heaters. The study considered several parameters, such as relative roughness pitch (RRP) (ranging from 5 to 8), cuboid arm length (ALC) (varying between 4 and 10 mm), and relative roughness height (RRH) (ranging from 0.44 to 0.077). To ensure turbulent flow during the experiment, the Reynolds number was kept within the range of 4250 to 18000, which is considered ideal for solar air heaters operating with a constant heat flux of 1000 W/m² on the absorber plate. An overall performance assessment of the artificially roughened solar air heater was conducted, taking into account the analysis of the Nusselt number and friction coefficient for both roughened and smooth absorber surfaces operating under similar flow conditions. The analysis reveals 2.48 times improvement in performance of the roughened configuration.
{"title":"Effective Efficiency Analysis of Artificially Roughed Solar Air Heater","authors":"MAN AZAD","doi":"10.1615/heattransres.2024052712","DOIUrl":"https://doi.org/10.1615/heattransres.2024052712","url":null,"abstract":"The solar air heater is a very simple and economical device, but its thermal performance is quite poor. The thermal performance of a solar air heater can be enhanced by increasing the heat transfer between absorber plates and blowing air. Applying artificial roughness to the absorber plate is a unique method for improving the thermal performance of solar air heaters compared to other methods. In this study, diagonally chamfered cuboids were used as roughness elements to investigate the enhancement in the performance of a solar air heater. This roughness is achieved by attaching diagonally chamfered cuboids to the surface of the absorber plate. A thorough experimental investigation was carried out to examine how this roughness affects the perfor-mance of solar air heaters. The study considered several parameters, such as relative roughness pitch (RRP) (ranging from 5 to 8), cuboid arm length (ALC) (varying between 4 and 10 mm), and relative roughness height (RRH) (ranging from 0.44 to 0.077). To ensure turbulent flow during the experiment, the Reynolds number was kept within the range of 4250 to 18000, which is considered ideal for solar air heaters operating with a constant heat flux of 1000 W/m² on the absorber plate. An overall performance assessment of the artificially roughened solar air heater was conducted, taking into account the analysis of the Nusselt number and friction coefficient for both roughened and smooth absorber surfaces operating under similar flow conditions. The analysis reveals 2.48 times improvement in performance of the roughened configuration.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"44 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315021","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}
An experimental study on oscillation behavior of vapor-liquid two-phase in aluminum ethanol miniaturized gravitational heat pipe with parallel rectangular channel is carried out. The nonlinear oscillation behavior and oscillation characteristics of two-phase in oscillation state are qualitatively analyzed. In addition, the nonlinear oscillation characteristic of the wall temperature is revealed. Furthermore, the influence of heat load on temperature oscillation characteristics is further analyzed. The research shows that the independent oscillation in single channel characterized by the random formation and oscillation of liquid plug in a single channel is the typical oscillation behavior of two-phase under medium heat load. In addition, the interaction on oscillation of liquid plugs between adjacent channels is small. For high heat load, the vapor pressure difference at both ends of the liquid plug has more important role in promoting the liquid plug, the superposition of the liquid plug oscillation in single channel and the oscillation between adjacent channels forms the interference oscillation in adjacent channels. For interference oscillation in adjacent channels, under coupling erosion of the liquid plug in single channel and the liquid plugs in adjacent channels, the wall temperature oscillates with large amplitude at high frequency and small amplitude at low frequency. With increase of heat load, the dominant frequency of oscillation for independent oscillation in single channel increases, and the larger driving force caused by heat load increase enhances the oscillation of liquid plug in single channel and weakens the oscillation of liquid plug in different chann
{"title":"Experimental study on two-phase nonlinear oscillation behavior of miniaturized gravitational heat pipe","authors":"Yu Fawen, Chaoyang Zhang, Tong Li, Yuhang Zhang, Wentao Zheng","doi":"10.1615/heattransres.2024052179","DOIUrl":"https://doi.org/10.1615/heattransres.2024052179","url":null,"abstract":"An experimental study on oscillation behavior of vapor-liquid two-phase in aluminum ethanol miniaturized gravitational heat pipe with parallel rectangular channel is carried out. The nonlinear oscillation behavior and oscillation characteristics of two-phase in oscillation state are qualitatively analyzed. In addition, the nonlinear oscillation characteristic of the wall temperature is revealed. Furthermore, the influence of heat load on temperature oscillation characteristics is further analyzed. The research shows that the independent oscillation in single channel characterized by the random formation and oscillation of liquid plug in a single channel is the typical oscillation behavior of two-phase under medium heat load. In addition, the interaction on oscillation of liquid plugs between adjacent channels is small. For high heat load, the vapor pressure difference at both ends of the liquid plug has more important role in promoting the liquid plug, the superposition of the liquid plug oscillation in single channel and the oscillation between adjacent channels forms the interference oscillation in adjacent channels. For interference oscillation in adjacent channels, under coupling erosion of the liquid plug in single channel and the liquid plugs in adjacent channels, the wall temperature oscillates with large amplitude at high frequency and small amplitude at low frequency. With increase of heat load, the dominant frequency of oscillation for independent oscillation in single channel increases, and the larger driving force caused by heat load increase enhances the oscillation of liquid plug in single channel and weakens the oscillation of liquid plug in different chann","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766150","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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