Film cooling is a common technique for protecting gas turbine components from the hot combustor exhaust. Highly resolved film cooling effectiveness distributions are often obtained by measuring the mass transfer of a foreign gas coolant in mainstream air using pressure sensitive paint (PSP). However, PSP is not able to measure the heat transfer coefficient, which is necessary to fully quantify the impact of film cooling. Instead, binary pressure sensitive paint (BPSP) has an additional luminophore that is sensitive to temperature and can be used to measure the heat transfer coefficient. In this experiment, the film cooling effectiveness and heat transfer coefficient were measured using BPSP on the leading edge of a cylinder. The cylinder had a 7.62-cm diameter with two rows of cooling holes at ±15°C from the leading edge. Each row contained 10 holes with a 0.475-cm diameter, spaced 4 diameters apart in the spanwise direction and angled 30°C from the cylinder axis. The mainstream Reynolds number was 100,000 based on cylinder diameter with a turbulence intensity of 7.1%. The coolant-to-mainstream density ratio was 1.0, and the blowing ratio was 0.8. The heat transfer coefficient was measured in a transient heat transfer experiment using the reference signal from the BPSP. Despite the high uncertainty of the measurement, ranging from 24.0% to 71.1%, the results demonstrate the feasibility of the method and identify the best test methodology to minimize conduction errors.
{"title":"ASSESSMENT OF BINARY PRESSURE SENSITIVE PAINT FOR TEMPERATURE AND HEAT TRANSFER COEFFICIENT MEASUREMENT OF LEADING EDGE FILM COOLING","authors":"Timothy A. Burdett, M. Yeh, L. Wright","doi":"10.1115/1.4063165","DOIUrl":"https://doi.org/10.1115/1.4063165","url":null,"abstract":"\u0000 Film cooling is a common technique for protecting gas turbine components from the hot combustor exhaust. Highly resolved film cooling effectiveness distributions are often obtained by measuring the mass transfer of a foreign gas coolant in mainstream air using pressure sensitive paint (PSP). However, PSP is not able to measure the heat transfer coefficient, which is necessary to fully quantify the impact of film cooling. Instead, binary pressure sensitive paint (BPSP) has an additional luminophore that is sensitive to temperature and can be used to measure the heat transfer coefficient. In this experiment, the film cooling effectiveness and heat transfer coefficient were measured using BPSP on the leading edge of a cylinder. The cylinder had a 7.62-cm diameter with two rows of cooling holes at ±15°C from the leading edge. Each row contained 10 holes with a 0.475-cm diameter, spaced 4 diameters apart in the spanwise direction and angled 30°C from the cylinder axis. The mainstream Reynolds number was 100,000 based on cylinder diameter with a turbulence intensity of 7.1%. The coolant-to-mainstream density ratio was 1.0, and the blowing ratio was 0.8. The heat transfer coefficient was measured in a transient heat transfer experiment using the reference signal from the BPSP. Despite the high uncertainty of the measurement, ranging from 24.0% to 71.1%, the results demonstrate the feasibility of the method and identify the best test methodology to minimize conduction errors.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"244 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74891933","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}
Mebratu Adamu Assegie, Ojing Siram, N. Sahoo, P. Kalita
The article presents the preparation and testing of packed bed (PB) material to be used as a thermal energy storage (TES) device. The proposed TES device will be used to store the high thermal energy attained during air compression in a compressed air energy storage (CAES) system. The article examines the utilization of mortar-based admixture by incorporating waste glass powder (WGP), graphite powder (GP), and waste glass sand (WGS). The selection of these constituents as a primary ingredient for the PB material has been made based on their availability, cost, and sustainability. The thermo-physical assessment of samples with different proportions of aggregates outlined two categories of PB- the first category of PB with low volumetric heat capacity (CP) for short/quick TES and the second category of PB with high CP for large/longer TES. The study also showcases the importance of GP in enhancing the CP of mortar-based TES devices as a result of high porosity.
{"title":"Thermo-Physical Characterization of Waste Glass Induced Packed Bed Material as Thermal Energy Storage Device for Compressed Air Energy Storage System","authors":"Mebratu Adamu Assegie, Ojing Siram, N. Sahoo, P. Kalita","doi":"10.1115/1.4063098","DOIUrl":"https://doi.org/10.1115/1.4063098","url":null,"abstract":"\u0000 The article presents the preparation and testing of packed bed (PB) material to be used as a thermal energy storage (TES) device. The proposed TES device will be used to store the high thermal energy attained during air compression in a compressed air energy storage (CAES) system. The article examines the utilization of mortar-based admixture by incorporating waste glass powder (WGP), graphite powder (GP), and waste glass sand (WGS). The selection of these constituents as a primary ingredient for the PB material has been made based on their availability, cost, and sustainability. The thermo-physical assessment of samples with different proportions of aggregates outlined two categories of PB- the first category of PB with low volumetric heat capacity (CP) for short/quick TES and the second category of PB with high CP for large/longer TES. The study also showcases the importance of GP in enhancing the CP of mortar-based TES devices as a result of high porosity.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"13 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91288474","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}
Pool boiling is extensively used in high and low-temperature heat exchangers as it results in a high heat transfer coefficient compared to natural and single-phase forced convection. Pool boiling experimental conducted over a plain cylindrical surface (PS) and four external micro-finned cylindrical surfaces (MFCSs), with R123 and R141b at different pressures in the heat flux range 20-100 kW/m2, have been presented in this paper. The objective of the present study is to explore the effect of pressure, surface characteristics and fluid properties on pool boiling heat transfer over plain and micro-finned cylindrical surfaces. The boiling heat transfer coefficient across micro-finned cylindrical surfaces was higher than it was for plain cylindrical surfaces due to lower surface wettability. In comparison to a plain cylindrical surface, the boiling heat transfer coefficient with pressure increases on average by 69% to 84% for the MFCS-1, MFCS-2, MFCS-3, and MFCS-4 with R123. At all tested pressures, pool boiling over a plain cylindrical surface with R123 yields a higher boiling heat transfer coefficient than previous experiments with R141b, whereas pool boiling over micro-finned cylindrical surfaces differs based on the combined effect of the micro-finned surface geometry, surface wettability, heat flux, pressure, and fluid properties.
{"title":"Evaluation of pressure, surface characteristics and fluid properties effect on pool boiling heat transfer over plain and external micro-finned cylindrical surfaces","authors":"Balkrushna A. Shah, P. Patel, V. Lakhera","doi":"10.1115/1.4063097","DOIUrl":"https://doi.org/10.1115/1.4063097","url":null,"abstract":"\u0000 Pool boiling is extensively used in high and low-temperature heat exchangers as it results in a high heat transfer coefficient compared to natural and single-phase forced convection. Pool boiling experimental conducted over a plain cylindrical surface (PS) and four external micro-finned cylindrical surfaces (MFCSs), with R123 and R141b at different pressures in the heat flux range 20-100 kW/m2, have been presented in this paper. The objective of the present study is to explore the effect of pressure, surface characteristics and fluid properties on pool boiling heat transfer over plain and micro-finned cylindrical surfaces. The boiling heat transfer coefficient across micro-finned cylindrical surfaces was higher than it was for plain cylindrical surfaces due to lower surface wettability. In comparison to a plain cylindrical surface, the boiling heat transfer coefficient with pressure increases on average by 69% to 84% for the MFCS-1, MFCS-2, MFCS-3, and MFCS-4 with R123. At all tested pressures, pool boiling over a plain cylindrical surface with R123 yields a higher boiling heat transfer coefficient than previous experiments with R141b, whereas pool boiling over micro-finned cylindrical surfaces differs based on the combined effect of the micro-finned surface geometry, surface wettability, heat flux, pressure, and fluid properties.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"27 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83320115","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}
Jiyu Zheng, Zheng Liang, Liang Zhang, Y. Qiu, JiaWei Zhou, Zhongchao Yan
A numerical investigation was performed to study the thermo-hydraulic performance in an enhanced tube with crossed helical dimples. The simulations were carried out in the Reynolds number range of 5000-30000 in crossed helical dimple tube of a period length with a constant wall temperature of 350K. The thermal enhancement, friction factor and performance evaluation criteria were the primary focus of the present work. Moreover, geometric parameters such as spiral pitch, transverse length and dimple depth were investigated for their effects on thermo-hydraulic performance. The results revealed that the shape of crossed helical dimple exerts positive effects on the heat transfer enhancement. This unique shape generated intensive transverse flow and induced a higher transverse velocity, leading to heat transfer enhancement. Therefore, the synthesized heat transfer performance was increased by 150% - 225% over that of the smooth tube. Furthermore, the heat transfer enhancement and friction factors increased with increasing dimple depth and declining spiral pitch and transverse length. Within the scope of this study, the maximum PEC = 2.25 was observed for Re = 30000, P = 30 mm, L = 11.064 mm, and H = 3 mm.
采用数值模拟方法研究了带交叉螺旋凹窝的强化管的热工性能。在雷诺数为5000 ~ 30000的周期长度、壁温为350K的交叉螺旋凹窝管中进行了模拟。热增强、摩擦系数和性能评价标准是本文研究的重点。此外，还研究了螺旋距、横向长度和凹窝深度等几何参数对热工性能的影响。结果表明，交叉螺旋凹窝的形状对强化传热有积极的影响。这种独特的形状产生了密集的横向流动，并诱导了更高的横向速度，从而增强了传热。因此，综合传热性能比光滑管提高了150% ~ 225%。换热强化系数和摩擦因数随韧窝深度的增加、螺旋节距和横向长度的减小而增大。在本研究范围内，当Re = 30000, P = 30 mm, L = 11.064 mm, H = 3 mm时，最大PEC = 2.25。
{"title":"Numerical study on thermo-hydraulic performance of enhanced tube with crossed helical dimples","authors":"Jiyu Zheng, Zheng Liang, Liang Zhang, Y. Qiu, JiaWei Zhou, Zhongchao Yan","doi":"10.1115/1.4063044","DOIUrl":"https://doi.org/10.1115/1.4063044","url":null,"abstract":"\u0000 A numerical investigation was performed to study the thermo-hydraulic performance in an enhanced tube with crossed helical dimples. The simulations were carried out in the Reynolds number range of 5000-30000 in crossed helical dimple tube of a period length with a constant wall temperature of 350K. The thermal enhancement, friction factor and performance evaluation criteria were the primary focus of the present work. Moreover, geometric parameters such as spiral pitch, transverse length and dimple depth were investigated for their effects on thermo-hydraulic performance. The results revealed that the shape of crossed helical dimple exerts positive effects on the heat transfer enhancement. This unique shape generated intensive transverse flow and induced a higher transverse velocity, leading to heat transfer enhancement. Therefore, the synthesized heat transfer performance was increased by 150% - 225% over that of the smooth tube. Furthermore, the heat transfer enhancement and friction factors increased with increasing dimple depth and declining spiral pitch and transverse length. Within the scope of this study, the maximum PEC = 2.25 was observed for Re = 30000, P = 30 mm, L = 11.064 mm, and H = 3 mm.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"21 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80837933","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}
Latent thermal energy storage systems (LTESS) have received widespread attention due to their high energy density to store a significant amount of thermal energy in a form of latent heat into phase change materials (PCM) at a nearly constant melting temperature. The thermal efficiency of LTESS is usually limited by poor heat conduction in PCM but enhanced by the natural convection of molten PCM. The natural convection increases the uniformity of temperature by mixing in a PCM enclosure, and therefore increases the heat transfer rates and accelerates the melting. While there is negligible natural convection, periodic reciprocation of heat transfer fluid (HTF) through the PCM enclosure has been demonstrated to increase the heat transfer rates to PCM by increasing the melt interface area and reducing temperature gradients across PCM compared to fixed-directional flow arrangements. The current study examines the effect of HTF flow direction on the strength and duration of natural convection in Gallium as the PCM in a vertical cylindrical shell-and-tube container. The irregular melting front in the PCM is caused by both natural convection in molten PCM and thermal boundary conditions for different HTF flow arrangements. The temperature and melting front profiles of PCM with the reciprocating flow arrangement are compared to unidirectional flows in upward and downward directions. The influence of HTF operating parameters such as temperature, velocity, and reciprocation period on PCM melting are studied. Scale analysis is also applied to characterize the different melting regimes of PCM under different flow arrangements.
{"title":"Natural convection in the melting of PCM in a cylindrical thermal energy storage system: effects of flow arrangements of heat transfer fluid and associated thermal boundary conditions","authors":"Meftah Uddin, A. S. Virk, Chanwoo Park","doi":"10.1115/1.4063045","DOIUrl":"https://doi.org/10.1115/1.4063045","url":null,"abstract":"\u0000 Latent thermal energy storage systems (LTESS) have received widespread attention due to their high energy density to store a significant amount of thermal energy in a form of latent heat into phase change materials (PCM) at a nearly constant melting temperature. The thermal efficiency of LTESS is usually limited by poor heat conduction in PCM but enhanced by the natural convection of molten PCM. The natural convection increases the uniformity of temperature by mixing in a PCM enclosure, and therefore increases the heat transfer rates and accelerates the melting. While there is negligible natural convection, periodic reciprocation of heat transfer fluid (HTF) through the PCM enclosure has been demonstrated to increase the heat transfer rates to PCM by increasing the melt interface area and reducing temperature gradients across PCM compared to fixed-directional flow arrangements. The current study examines the effect of HTF flow direction on the strength and duration of natural convection in Gallium as the PCM in a vertical cylindrical shell-and-tube container. The irregular melting front in the PCM is caused by both natural convection in molten PCM and thermal boundary conditions for different HTF flow arrangements. The temperature and melting front profiles of PCM with the reciprocating flow arrangement are compared to unidirectional flows in upward and downward directions. The influence of HTF operating parameters such as temperature, velocity, and reciprocation period on PCM melting are studied. Scale analysis is also applied to characterize the different melting regimes of PCM under different flow arrangements.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"108 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87629189","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}
Enhancing gas-side thermal conductance is essential for the compact sizing of finned-tube heat exchangers, and this study attempts it by integrating vortex generators. The orientation of the vortex generators, which is defined by its attack angle, has a strong bearing on the degree of augmentation. As energy-efficiency keeps varying with the attack angle, the thrust of this investigation is to identify best attack angle(s) for the stipulated task. Since spatial positioning of the generators too has a strong bearing on the energy-efficiency, therefore, its effect is duly accounted for a comprehensive investigation. For the selection of optimal designs, regression-based phenomenological models are used as they apply thermo-hydraulic trade-off. After determining the best angle(s), a study is carried out to evaluate their robustness under varying operating conditions. Although phenomenological models are adequate for design optimization, they do not describe the physics of thermo-hydraulic enhancement. Therefore, a study explaining the bearing of design modifications on the local characteristics too is carried out. Additionally, a study discussing the effect of generators' attack angle on heat transfer over the wake affected surfaces, which has a predominant existence in baseline flows, is reported. It has been found that the thermal augmentation over the said surfaces is the key to compact sizing of the system. For a selected wake-region deployment, the highest relative Colburn j-factor corresponding to wake-affected fin equals 3.07 at a specified Reynolds number..
{"title":"Attack angle parametrization for capacity augmentation and wake management by vortex generators in finned compact heat exchangers","authors":"A. Arora, P. Subbarao","doi":"10.1115/1.4063046","DOIUrl":"https://doi.org/10.1115/1.4063046","url":null,"abstract":"\u0000 Enhancing gas-side thermal conductance is essential for the compact sizing of finned-tube heat exchangers, and this study attempts it by integrating vortex generators. The orientation of the vortex generators, which is defined by its attack angle, has a strong bearing on the degree of augmentation. As energy-efficiency keeps varying with the attack angle, the thrust of this investigation is to identify best attack angle(s) for the stipulated task. Since spatial positioning of the generators too has a strong bearing on the energy-efficiency, therefore, its effect is duly accounted for a comprehensive investigation. For the selection of optimal designs, regression-based phenomenological models are used as they apply thermo-hydraulic trade-off. After determining the best angle(s), a study is carried out to evaluate their robustness under varying operating conditions. Although phenomenological models are adequate for design optimization, they do not describe the physics of thermo-hydraulic enhancement. Therefore, a study explaining the bearing of design modifications on the local characteristics too is carried out. Additionally, a study discussing the effect of generators' attack angle on heat transfer over the wake affected surfaces, which has a predominant existence in baseline flows, is reported. It has been found that the thermal augmentation over the said surfaces is the key to compact sizing of the system. For a selected wake-region deployment, the highest relative Colburn j-factor corresponding to wake-affected fin equals 3.07 at a specified Reynolds number..","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"126 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78561027","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}
Mohamed Tahar Baissi, S. Hassani, Hesseyn Karoua, Kamel Aoues, M. Noureddine
Experiments have been conducted to determine how several geometrical parameters of V-shaped porous baffles influence flow characteristics and heat transfer in a rectangular channel. Experiments were conducted on geometric parameters, namely, a relative baffle height (e/H) of 0.4–1, a relative baffle pitch (P/e) of 3–6, open area ratio values of 21%–34%, and a single attack angle (a) of 60°. Using Reynolds numbers ranging from 2500 to 12,000, V-shaped porous baffles have been examined. Based on a relative baffle pitch of 5, a relative baffle height of 1, and an open area ratio of 21%, the maximum increases in the Nusselt number (Nu) and friction factor (f) were 2.84 and 7 times, respectively. A maximum value of 1.69 is found at e/H = 0.40, P/e = 6, and b = 34% for the thermo-hydraulic performance parameter. Correlations for (Nu) and (f) are developed as functions of P/e, e/H, and Re.
{"title":"Experimental study of thermal hydraulic performance improvement in solar air heater channel with V-shaped porous baffles","authors":"Mohamed Tahar Baissi, S. Hassani, Hesseyn Karoua, Kamel Aoues, M. Noureddine","doi":"10.1115/1.4063043","DOIUrl":"https://doi.org/10.1115/1.4063043","url":null,"abstract":"\u0000 Experiments have been conducted to determine how several geometrical parameters of V-shaped porous baffles influence flow characteristics and heat transfer in a rectangular channel. Experiments were conducted on geometric parameters, namely, a relative baffle height (e/H) of 0.4–1, a relative baffle pitch (P/e) of 3–6, open area ratio values of 21%–34%, and a single attack angle (a) of 60°. Using Reynolds numbers ranging from 2500 to 12,000, V-shaped porous baffles have been examined. Based on a relative baffle pitch of 5, a relative baffle height of 1, and an open area ratio of 21%, the maximum increases in the Nusselt number (Nu) and friction factor (f) were 2.84 and 7 times, respectively. A maximum value of 1.69 is found at e/H = 0.40, P/e = 6, and b = 34% for the thermo-hydraulic performance parameter. Correlations for (Nu) and (f) are developed as functions of P/e, e/H, and Re.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"56 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85966729","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}
Multi-staging and variable cross-section significantly improve the performance of thermoelectric generators. Hence, the present theoretical study analyses a multistage variable-shaped thermoelectric generator (MVS TEG) for a combination of dissimilar materials. Effect on voltage, power, conversion efficiency, normalized constraints (voltage, energy, and conversion efficiency), and second law efficiency with a row number, exhaust inlet temperature, and the coolant flow rate have been investigated. Results reveal that the row number is the most critical input parameter, followed by exhaust inlet temperature and coolant flow rate. Also, the work gives optimum values of rows for voltage and power as Nx=19 for MVS TEG-1, MVS TEG-3, and MVS TEG-4 while Nx=18 for MVS TEG-2. The exhaust inlet temperature variation increases the voltage and power output by 54 to 59% and 53 to 58%, respectively. The coolant flow variation has a more significant impact on the conversion efficiency, and the average improvement in the efficiency is about 9.23% in the present study. The second law efficiency decreases with the increase in all the input parameters.
{"title":"Effects of Performance and Normalized parameters on various materials based Multistage Thermoelectric Generator","authors":"Kartik Srivastava, R. Sahoo","doi":"10.1115/1.4062999","DOIUrl":"https://doi.org/10.1115/1.4062999","url":null,"abstract":"\u0000 Multi-staging and variable cross-section significantly improve the performance of thermoelectric generators. Hence, the present theoretical study analyses a multistage variable-shaped thermoelectric generator (MVS TEG) for a combination of dissimilar materials. Effect on voltage, power, conversion efficiency, normalized constraints (voltage, energy, and conversion efficiency), and second law efficiency with a row number, exhaust inlet temperature, and the coolant flow rate have been investigated. Results reveal that the row number is the most critical input parameter, followed by exhaust inlet temperature and coolant flow rate. Also, the work gives optimum values of rows for voltage and power as Nx=19 for MVS TEG-1, MVS TEG-3, and MVS TEG-4 while Nx=18 for MVS TEG-2. The exhaust inlet temperature variation increases the voltage and power output by 54 to 59% and 53 to 58%, respectively. The coolant flow variation has a more significant impact on the conversion efficiency, and the average improvement in the efficiency is about 9.23% in the present study. The second law efficiency decreases with the increase in all the input parameters.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"29 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76234769","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}
He Yang, Jinduo Li, Huimin Wei, Xiaoze Du, Hongwei Wu
Two new types of PCHE channels are proposed based on typical airfoil fin PCHE channel proposed in literatures (standard channel) to further improve the thermal-hydraulic performances of airfoil fin PCHE channel. The small shuttle fins and oval fins are employed between the adjacent two airfoil fins of two novel channels, respectively. Using supercritical CO2 as the working fluid, the thermal-hydraulic performances and enhancement mechanisms of the novel channels are numerically investigated. The results show that the channel with shuttle fins has the best comprehensive performance. The Nusselt number of the channel with shuttle fins is 6.7–26% larger, and the f factor is 8.3–18.6% larger than that of the standard channel under the selected conditions, which leads to a 3–19.1% increase in the PEC (comprehensive performance evaluation criteria). The Nusselt number of the channel with oval fins is 9–27.3% larger, and the f factor is 26.6–43.4% larger than that of the standard channel, which leads to a 1–15.3% increase in the PEC. The applications of small fins between the adjacent two fins can effectively reduce the low-velocity region area and enhance the local disturbance, thereby effectively improving the thermal-hydraulic performance. The enhancement mechanism of the novel fin PCHE channel structure can be well explained by the principle of field synergy. It can be found that the synergies of the temperature gradient field and the velocity field in two novel channels are significantly improved.
{"title":"Study on thermal-hydraulic characteristics of novel channels for printed circuit heat exchanger using supercritical CO2","authors":"He Yang, Jinduo Li, Huimin Wei, Xiaoze Du, Hongwei Wu","doi":"10.1115/1.4062998","DOIUrl":"https://doi.org/10.1115/1.4062998","url":null,"abstract":"\u0000 Two new types of PCHE channels are proposed based on typical airfoil fin PCHE channel proposed in literatures (standard channel) to further improve the thermal-hydraulic performances of airfoil fin PCHE channel. The small shuttle fins and oval fins are employed between the adjacent two airfoil fins of two novel channels, respectively. Using supercritical CO2 as the working fluid, the thermal-hydraulic performances and enhancement mechanisms of the novel channels are numerically investigated. The results show that the channel with shuttle fins has the best comprehensive performance. The Nusselt number of the channel with shuttle fins is 6.7–26% larger, and the f factor is 8.3–18.6% larger than that of the standard channel under the selected conditions, which leads to a 3–19.1% increase in the PEC (comprehensive performance evaluation criteria). The Nusselt number of the channel with oval fins is 9–27.3% larger, and the f factor is 26.6–43.4% larger than that of the standard channel, which leads to a 1–15.3% increase in the PEC. The applications of small fins between the adjacent two fins can effectively reduce the low-velocity region area and enhance the local disturbance, thereby effectively improving the thermal-hydraulic performance. The enhancement mechanism of the novel fin PCHE channel structure can be well explained by the principle of field synergy. It can be found that the synergies of the temperature gradient field and the velocity field in two novel channels are significantly improved.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"72 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84496436","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 aim of this study was to enhance the accuracy of predicting the temperature field of frozen soil and to reduce the workload of thermal parameter testing. To achieve this, we employed a three-phase model comprising soil, water, and ice. The unfrozen water content in frozen soil at varying temperatures was determined using nuclear magnetic resonance spectroscopy (NMR), while the thermal conductivity was measured by a thermal characteristic analyzer. A MATLAB software-based random model of the frozen soil was then established and imported into COMSOL simulation software. The repeatability and reproducibility of the established model were verified by varying the proportions of pore water and frozen ice to determine the degree of simulation accuracy.The results demonstrated that the unfrozen water content maintained a dynamic equilibrium relationship with temperature, which influenced the thermal conductivity of frozen soil. The simulation results were consistent with those obtained from instrument measurements of trends with respect to temperature. The average PBIAS value between the calculated and measured values was 0.0139, indicating theoretical feasibility. Comparison with experimental data confirmed the effectiveness of our approach, providing a novel concept and a simple method for predicting the temperature field of frozen soil engineering in areas that experience seasonal freezing.
{"title":"Experimental study and simulation of thermal conductivity of saturated frozen soil","authors":"Zhifeng Ren, Enliang Wang, Jiankun Liu","doi":"10.1115/1.4062975","DOIUrl":"https://doi.org/10.1115/1.4062975","url":null,"abstract":"\u0000 The aim of this study was to enhance the accuracy of predicting the temperature field of frozen soil and to reduce the workload of thermal parameter testing. To achieve this, we employed a three-phase model comprising soil, water, and ice. The unfrozen water content in frozen soil at varying temperatures was determined using nuclear magnetic resonance spectroscopy (NMR), while the thermal conductivity was measured by a thermal characteristic analyzer. A MATLAB software-based random model of the frozen soil was then established and imported into COMSOL simulation software. The repeatability and reproducibility of the established model were verified by varying the proportions of pore water and frozen ice to determine the degree of simulation accuracy.The results demonstrated that the unfrozen water content maintained a dynamic equilibrium relationship with temperature, which influenced the thermal conductivity of frozen soil. The simulation results were consistent with those obtained from instrument measurements of trends with respect to temperature. The average PBIAS value between the calculated and measured values was 0.0139, indicating theoretical feasibility. Comparison with experimental data confirmed the effectiveness of our approach, providing a novel concept and a simple method for predicting the temperature field of frozen soil engineering in areas that experience seasonal freezing.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"41 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85237321","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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