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25 June 2018
Thermodynamic and thermoeconomic analysis and optimization of a novel dual-loop power/refrigeration cycle
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Hadi Rostamzadeh, Hadi Ghaebi, Shahram Vosoughi, Javad Jannatkhah Exploration of the ejector refrigeration cycle (ERC) in the combination with well-known power cycles to produce cooling output as well as power output is highlighted in recent decades. Since organic Rankine cycle (ORC) is practically usable than other power cycles, a combination of the ORC/ERC in a novel form is presented. Power and refrigeration sub-cycles are combined by a common condenser in separate loops to form dual-loop power/refrigeration cycle. The exhaust of the turbine is mixed with the outlet flow of the ejector, and then the mixed flow is fed into the condenser. Thermodynamic and thermoeconomic analysis of the proposed cycle are carried out with different working fluids (i.e., isobutane, isobutene, butene, cis-2-butene, n-butane, R236fa, and R245fa) showing that among all working fluids isobutane is the best one from thermodynamic, thermoeconomic, and environmental viewpoints. The results of exergy analysis showed that among all components generator accounts for the biggest exergy destruction rate followed by the heater for all selected working fluids. In addition, multi-objective optimization of the proposed cycle is carried out by considering of generator pressure, heater pressure, evaporator temperature, and condenser temperature as decision variables, using the genetic algorithm (GA). The results of the optimization demonstrated that the proposed cycle performs in an optimum state based on the selected objective functions when generator pressure, heater pressure, evaporator temperature, and condenser temperature work at 3
25 June 2018
Off-design performance comparative analysis between basic and parallel dual-pressure organic Rankine cycles using radial inflow turbines
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Yang Du, Yi Yang, Dongshuai Hu, Muting Hao, Jiangfeng Wang, Yiping Dai This paper compares off-design performances of the basic organic Rankine cycle (ORC) and the parallel dual-pressure organic Rankine cycle (PDORC) for low temperature hot water. Off-design models of the basic ORC and the PDORC are established based on specially designed plate heat exchangers and radial inflow turbines. The particle swarm optimization (PSO) algorithm is applied to obtain optimal operating parameters. The sliding pressure operation is adopted for different conditions in terms of corresponding hot water parameters and saturated condensing temperature. The results indicate that the efficiency of the low-pressure radial turbine is more strongly affected by the hot water mass flow rate ratio than that of the high-pressure radial turbine does in the PDORC. Radial inflow turbine efficiencies of the basic ORC and the PDORC are more strongly influenced by the saturated condensing temperature than the hot water inlet temperature. The ratio of the high-pressure subcycle net power to the low-pressure subcycle net power in the PDORC decreases obviously with the increase of the hot water mass flow rate ratio or the decrease of the saturated condensing temperature. The ratio of the PDORC net power to the basic ORC net power decreases to the minimum before increasing with the increase of the hot water mass flow rate ratio, while this net power ratio decreases with the increase of the hot water inlet temperature or the decrease of the saturated condensing temperature.
25 June 2018
Numerical study on the thermal performance of lightweight temporary building integrated with phase change materials
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Li Zhu, Yang Yang, Sarula Chen, Yong Sun The phase change materials (PCMs) integrated in building envelope structure can decrease the buildings’ energy consumption and improve indoor thermal comfort quality. This paper numerically studied the application effect of PCMs as a passive alternative in lightweight building with high shape coefficient for temporary accommodations under Tianjin climate, and the impacts of some key design parameters, such as the location, thickness and orientation, on building’s thermal behavior were explored when single orientation layout scheme was adopted. Besides, the multi-orientation layout schemes were put forward to achieve further optimization on indoor thermal comfort. The simulation results stated that the proper application of PCMs could obviously improve and promote indoor thermal comfort. In detail, the results indicated that PCM layer with a reasonable thickness, e.g. 5.0
25 June 2018
Experimental optimization of reactivity controlled compression ignition combustion in a light duty diesel engine
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): M. Murugesa Pandian, K. Anand Reactivity Controlled Compression Ignition (RCCI) is emerging as a most promising combustion strategy to achieve near zero oxides of nitrogen (NOx) and smoke emissions along with higher brake thermal efficiency. The present work attempts to implement RCCI strategy in a production, light duty diesel engine by replacing an existing mechanical fuel injection with a flexible common rail direct injection diesel system and a low pressure gasoline port fuel injection system. Further, the engine compression ratio is reduced through modifications in piston bowl. Using a suitable controller, the engine operating parameters in terms of direct injected diesel timings, injection pressure, port injected gasoline quantity and gasoline to diesel ratio at each load conditions are optimized to achieve maximum brake thermal efficiency. Before modifications, the engine is run under conventional combustion mode at rated speed, varying loads to establish baseline reference data. The obtained results show that the engine could be operated in RCCI mode over its entire load range with a maximum increase of 14.2% brake thermal efficiency, near zero NOx and smoke emissions compared to conventional combustion. Further, reducing compression ratio is found to increase brake thermal efficiency by 7.6% and reduce carbon monoxide by 16.8% in RCCI.
25 June 2018
New procedure for determination of availability and reliability of complex cogeneration systems by improving the approximated Markov method
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): M.H. Khoshgoftar Manesh, M. Pouyan Rad, M.A. Rosen There are two procedures to solve reliability problems: analytical techniques and stochastic simulation. Each has advantages and disadvantages. One of the important analytical techniques for repairable systems is the Markov method. This method uses state space to consider all states that may occur. To use this method for complex systems, the model of the system must be simplified. For this purpose, many states are removed from the space state. In this way, although the probabilities of the states are calculated, these probabilities are often not accurate. In the present work, a new approach is proposed that considers both the simplified system and the calculation of the probability of each state accurately. The new method can calculate the probabilities by taking into account minimum states. Site utility systems are used to illustrate the procedure for applying this method. Site utilities have several repairable components (e.g. steam turbine, gas turbine, HRSG, de-aerator, boiler). So, this system can generate a large and complex state space for which it is difficult to calculate the probability. The new procedure can reduce the number of states and aggregates of the exploded state space due to the high number of components. The results show that the new procedure can predict state probabilities with high accuracy.
25 June 2018
The fluid-thermal-solid coupling analysis of a scroll expander used in an ORC waste heat recovery system
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Zhen Liu, Mingshan Wei, Panpan Song, Simon Emhardt, Guohong Tian, Zhi Huang In this research, a one-way fluid-thermal-solid numerical coupling model of a scroll expander for a waste heat recovery system was developed and used to investigate the deformation of the scroll pair. The pressure and thermal loads were firstly calculated by a CFD model, and the surface pressure and body temperature distributions of the scroll members were used as boundary conditions in the FEM model to obtain the deformation distributions of the scroll parts. Three time instants that may have significant adverse impacts on the maximum forces were selected to determine the most critical time for the occurrence of the maximum deformation of the scroll wraps. The results showed that the deformations induced by inertial force only occurred at the orbiting scroll tail, whereas the deformations in other regions negligible. At the time instants of t/T equaled to 13/15 and 1, the deformations induced by pressure loads had the opposite direction compared to that of the thermal loads and thus the two deformations canceled each other out and the coupling deformations decreased. The deformations induced by pressure loads were less significant than the thermal loads, therefore the coupling deformation was dominated by the thermal loads. The results also confirmed that the critical time at t/T equaled to 7/20 for the occurrence of the largest deformation resulted from the maximum axial forces that were exerted on the fixed scroll.
25 June 2018
Rapid temperature prediction method for electronic equipment cabin
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Hongquan Qu, Shuo Fu, Liping Pang, Chen Ding, Helin Zhang An accurate model is very important for thermal prediction and thermal management of airborne electronic module. Thermal Network Model (TNM) is the commonly used to analyze transient thermal response. It cannot describe the nonlinear or time-varying temperature process very well. In order to realize a fast thermal modeling with a relatively high accuracy, this paper proposes a modeling method based on sliding time window Random Vector Functional Link Neural Network (RVFLNN). The input and output variables of RVFLNN are determined by analyzing the heat transfer relationship of studied system. This method can rapidly realize thermal modeling without a time-consuming iterative training process. In order to overcome the variability of studied system, the sliding time window technology is specially introduced to improve the model prediction accuracy. This method is applied to analyze thermal experimental data of electronic equipment cabin. The temperature prediction performance of presented method is compared with the traditional Artificial Neural Network Model (ANNM). Comparison results show that the proposed modeling method has the advantages of fast modeling and good prediction accuracy. This study can provide an effective way to describe a complex dynamic heat transfer process adaptively and accurately, which may help the thermal control scheme design.
25 June 2018
Aerodynamic design method of micro-scale radial turbines considering the effect of wall heat transfer
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Zhenpeng Li, Zhengping Zou, Lichao Yao, Chao Fu, Lei Bian, Weihao Zhang It is important to consider the effect of wall heat transfer in the one-dimensional design of a micro-scale radial turbine as wall heat transfer significantly affects the micro-turbine performance. A thermodynamic analytical model for a micro-turbine that considers the effect of wall heat transfer was developed based on theoretical analysis and empirical correlations, and was validated through numerical simulation. With this thermodynamic analytical model, the sensitivity and influence of the parameters on the micro-scale radial turbine aerodynamic performance were analyzed. The results show that, compared to other parameters, wall heat transfer is one of the most crucial factors affecting the aerodynamic performance of the micro-turbine, which cannot be neglected in the design process of the micro-scale radial turbine. On the basis of the analytical results above, a velocity triangle analytical model considering the effect of wall heat transfer was further proposed to benefit the improvement of a one-dimensional aerodynamic design method for micro-turbines. The numerical results show that the performance of the micro-turbine obtained by using this design method can completely meet the design requirements.
25 June 2018
A numerical study into effects of intermittent pump operation on thermal storage in unsaturated porous media
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Mohammad Hossein Jahangir, Mahyar Ghazvini, Fathollah Pourfayaz, Mohammad Hossein Ahmadi In this paper, the effects of varying soil properties and intermittent pump operation on the performance of the thermal storage system are examined using finite element numerical simulation. Furthermore, 10
25 June 2018
A multi-block lattice Boltzmann method for the thermal contact resistance at the interface of two solids
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Wen-Zhen Fang, Jian-Jun Gou, Li Chen, Wen-Quan Tao In the present paper, a patching type multi-block lattice Boltzmann method is adopted to predict the thermal contact resistance (TCR) at the interface of two solids. The rough surfaces of contact materials are reconstructed based on the fractal theory and the contact pressure is obtained based on the plastic deformation model. The accuracy of the patching type multi-block lattice Boltzmann method is validated by some benchmarks. After validations, effects of the contact pressure, roughness, thermal conductivity of contact material, thermal conductivity of interstitial medium, temperature and radiation on TCR are investigated. The results show that: the TCR decreases when the contact pressure increases, but increases with the root-mean-square roughness; the TCR of two contact aluminums decreases faster than that of stainless steels when contact pressure increases; a higher thermal conductivity of contact materials leads to a smaller TCR; when the thermal conductivity of interstitial medium is close to zero or the gap is in vacuum, the TCR is much larger than that filled with air, especially at low contact pressure; at the high temperature, the contribution of the radiation to the TCR becomes appreciable if the thermal conductivity of the interstitial medium is low. Especially when the gap is in vacuum, the contribution of radiation on the TCR cannot be neglected.
25 June 2018
Investigation of convection heat transfer coefficient of circular cross-section short pipes in hot stamping dies
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Liang Ying, Tianhan Gao, Minghua Dai, Ping Hu, Luming Shen Since the cooling system design in hot stamping dies is an important issue in hot stamping technology, the heat transfer characteristics between water flow and the inner wall of pipes becomes particularly important for its remarkable effect on hot stamping process. In order to investigate the heat transfer characteristics between H13 tool steel and the water flow in hot stamping dies, a self-developed Convection Heat Transfer Coefficient (CHTC) measuring equipment was established based on a circular cross-section short pipe model. To calculate the CHTC, an analytical calculating method named Fourier equation method based on experimental data and a numerical simulation method were introduced. To further investigate the influence of different factors including inlet fluid mass flow rate, inlet fluid temperature, inlet fluid turbulence intensity, pipe diameter, surface roughness and the furnace temperature on the CHTC, more numerical simulations were implemented, together with the ANOVA analysis. And results showed that the obtained simulation temperature field was in good agreement with the experiment, and the calculated CHTC values distilled from the simulation results were matched well with that of experiment, too. Moreover, all the investigated factors were found to have significant influence on the CHTC value, and the top three factors are inlet fluid mass flow rate, inlet fluid temperature and inner pipe surface roughness. Finally, a novel threaded pipe applied in hot stamping die was introduced derived from the ideal of improving inner pipe surface roughness, which was found to have much higher CHTC, the turbulence intensity along the cooling pipe could be promoted, which could help increase the heat transfer intensity as well.
25 June 2018
Numerical study of turbulent annular impinging jet flow and heat transfer from a flat surface
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Farhana Afroz, Muhammad A.R. Sharif This paper presents the results of a numerical investigation of fluid flow and heat transfer due to a turbulent annular jet impingement on an isothermally heated flat surface. Annular impinging jets enhance the heat transfer and spread it more uniformly over the impingement surface compared to the round impinging jet, and have one noteworthy characteristic of forming a reverse stagnation flow. A parametric numerical study for turbulent annular jet impingement is conducted for various blockage ratios (0.4–0.8) and non-dimensional jet exit-to-target plate separation distances (0.5–4.0) at a wide range of jet exit Reynolds number (5000–25,000). The numerical computation on a highly refined mesh is performed using the ANSYS Fluent commercial code and the computational process is validated against other published experimental data on similar flow and geometric configuration. In order to choose an appropriate turbulence model for the computations, the performance of few different turbulence models is evaluated based on the comparison against experimental Nusselt number distribution on the flat surface. The Realizable k-
25 June 2018
Simulation investigation on inlet velocity profile and configuration parameters of louver fin
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Zuoqin Qian, Qiang Wang, Junlin Cheng, Jun Deng This work aimed to investigate the effect of louver fin configurations on the thermal performance at different Reynolds numbers. The discussed ranges of these geometry parameters were 7.5–12.5
25 June 2018
A thermal-stress field calculation method based on the equivalent heat source for the dielectric fitting under discharging
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Fan Yang, Kai Liu, Shaohua Wang, Bing Gao, Shaogui Ai, Xinlong Zheng, Yanjie Le, Irfan Uilah The discharging in the dielectric fitting can generate thermal shock and thermal stress, which will break the insulation and containment of the dielectric fitting. The discharging process in the dielectric fitting causes the multiple physical field coupling problem, which makes it difficult to calculate the thermal-stress field distribution of the dielectric fitting under discharging directly. This paper proposes a thermal-stress field calculation method of the dielectric fitting under discharging based on the equivalent heat source. In the first stage, this paper considers the discharging in the dielectric fitting as the discharging between a tip and plane electrodes, and builds the magnetohydrodynamic (MHD) model for the arc. In the second stage, an equivalent heat source is proposed to be equivalent to the heat effect of the arc. In the third stage, its accuracy is verified by comparing with the simulation results in MHD model. The results show that the error between the equivalent model and the MHD model is less than 0.3%, which proves that the equivalent heat source can be equivalent to the heat effect of the arc. Furthermore, the equivalent heat source is used to calculate the thermal and stress distributions of the dielectric fitting under discharging. Finally, the experiments verify the feasibility and accuracy of the proposed method.
25 June 2018
Experimental investigation on heat transfer of n-pentane spray impingement on piston surface
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Zhi-Fu Zhou, Safwan Hanis Mohd Murad, Jia-Meng Tian, Joseph Camm, Richard Stone Fuel spray impingement on piston surfaces is a concern because it can cause particulate exhaust emissions from gasoline direct injection (GDI) engine. Transient heat transfer plays an important role that directly influences liquid film evaporation and its lifetime. In this paper, the effects of injection temperature, injection pressure, piston temperature and impact distance on n-pentane spray impingement heat transfer were fully examined. Results showed that increasing the piston temperature could increase the rate of heat transfer with a larger surface temperature reduction and a higher heat flux, which led to a shorter liquid film lifetime on the piston surface. Increasing the fuel injection temperature helped to improve atomization of the fuel spray, reduce the penetration distance and mitigate impact, which in turn led to reduced surface cooling and less liquid film on the piston surface. A decrease in impact distance and an increase in injection pressure both caused an increase in surface temperature reduction and heat flux but a decrease in the liquid film residence time. The dimensionless heat flux in terms of Biot and Fourier numbers presented a high similarity during the rapid cooling stage. A dimensionless correlation was formed to quantify this fast time-varying heat transfer behaviour.
25 June 2018
Industrial waste heat: Estimation of the technically available resource in the EU per industrial sector, temperature level and country
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Michael Papapetrou, George Kosmadakis, Andrea Cipollina, Umberto La Commare, Giorgio Micale Industrial waste heat is examined in EU countries, focusing on the amount that can be recovered and exploited, referred to as technical potential of waste heat. An alternative methodology is proposed here, which is based on waste heat fractions derived from a detailed study of the UK industry from the period 2000–2003. These fractions express the part of heat consumption that is wasted and is possible to be recovered. The waste heat fractions have been calculated in this work for each main industrial sector and temperature level. The methodology initially includes the adjustment of waste heat fractions from each industrial sector from the UK industry to the conditions of the different EU countries in the period 2000–2003, in order to account for the different levels of energy efficiency. The second step is to adjust the fractions for the year 2015, using data about the evolution of energy intensity values from 2000 to 2003 to 2015 for each country and sector, resulting to a new set of fractions per country, temperature level and sector. This methodology has enabled the authors to study in detail the waste heat potential per sector and temperature level, using the most recent data. The main outcome is the estimation of waste heat potential for each main industrial sector in the EU, broken down to the amount of waste heat for each temperature range. A similar analysis is conducted for each EU country as well, in order to identify the magnitude of heat recovery opportunities that could exist for every industrial sector at country level. The main result of this analysis is the estimation of the total waste heat potential in EU, which is about 300
25 June 2018
CFD-based optimization of a transient heating process in a natural gas fired furnace using neural networks and genetic algorithms
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Rene Prieler, Markus Mayrhofer, Christian Gaber, Hannes Gerhardter, Christoph Schluckner, Martin Landfahrer, Markus Eichhorn-Gruber, G
25 June 2018
Power generation from fluegas waste heat in a 500 MWe subcritical coal-fired thermal power plant using solar assisted Kalina Cycle System 11
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Goutam Khankari, Sujit Karmakar This paper proposes a solar assisted Kalina Cycle System 11 (KCS 11) driven by fluegas waste heat of 500
25 June 2018
Experimental study of the fins arrangement pattern of refrigerated display cabinet evaporator towards thermal performance improvement
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Gustavo G. Heidinger, Samuel M. Nascimento, Pedro D. Gaspar, Pedro D. Silva This paper reports the results of experimental tests performed according to ISO 23953 in an open multideck display cabinet with dual air curtain to evaluate the impact of the evaporator fins arrangement pattern on the overall thermal performance. Experimental laboratory tests were performed on climate class no. 3 (25
25 June 2018
Design and evaluation of an additively manufactured aircraft heat exchanger
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): David Saltzman, Michael Bichnevicius, Stephen Lynch, Timothy W. Simpson, Edward W. Reutzel, Corey Dickman, Richard Martukanitz Additive manufacturing (AM) technology has significant potential to improve heat exchanger (HX) performance through incorporation of novel geometries and materials, but there is limited understanding of AM HX functionality relative to conventionally manufactured components. This study compares the performance of conventionally-built plate-fin air–liquid crossflow heat exchangers (i.e., aircraft oil coolers) to additively manufactured heat exchangers of similar geometry. To replicate internal features, three dimensional X-ray computed tomography scans were performed on the conventionally-built heat exchanger. A baseline AM model of the conventional design was designed, as well as an AM model with additional enhancement features on the air side. The two AM heat exchanger geometries were constructed using a laser-based powder bed fusion process with AlSi10Mg aluminum-alloy powder. Visual inspection of the as-built AM HX indicated significant surface roughness and some cracks in the fin-tube joint, but only at the edges of the heat exchanger. Overall heat transfer was increased by about 10 percent for the baseline AM and by 14 percent for the enhanced AM heat exchanger when compared to the conventionally built baseline heat exchanger. Measured air-side pressure drop for the AM heat exchangers was double that of the conventionally built baseline heat exchanger. Overall, this study indicates potential for improved heat transfer and demonstrated functionality of AM HX in realistic applications.
25 June 2018
Theoretical investigation on performance improvement of a low-temperature transcritical carbon dioxide compression refrigeration system by means of an absorption chiller after-cooler
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): S.M. Hojjat Mohammadi A Transcritical Carbon dioxide Compression (TCC) refrigeration system is a suitable tool to provide low-temperature refrigeration, but with a low COP. To improve the performance of a TCC, different combinations of Liquid Suction Heat Exchanger (LSHE), after-cooler and two-stage compression are embedded into the system configuration. The cooling load of the after-cooler is provided by an Absorption Chiller (ABSC) and the required heating energy to run the ABSC is recovered from the hot refrigerant leaving the compressors of the TCC. Eleven modified configurations are proposed and modeled in detail by EES software and energy and exergy analyzes are performed for each configuration. The results showed that the two-stage compression is a suitable method to upgrade the TCC system performance from both first and second laws of thermodynamics view point. The COP of a typical two-stage TCC is calculated to be 207% higher than its single-stage counterpart, in an evaporator temperature of
25 June 2018
Numerical investigation on thermal insulation layer of a tunnel in seasonally frozen regions
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Qinguo Ma, Xiaoxiao Luo, Yuanming Lai, Fujun Niu, Jianqiang Gao As an effective engineering measure, thermal insulation layer is used to prevent tunnel from frost heave damage in seasonally frozen regions. Two different methods are generally adopted to lay insulation layer. One is to lay the insulation layer between the preliminary lining and the secondary lining. The other is to lay the insulation layer on the surface of the secondary lining. But, there is no evidence to show which method is more useful. Meantime, the relationship between the insulation effect and thermal conductivity as well as thickness of insulation layer should be identified. To solve these problems, a numerical heat-moisture coupled model for the tunnel in a seasonally frozen region is established, which involves heat conduction, water migration and phase transition. And then, a representative tunnel in the Northwest of China is taken as an example to explore the heat-moisture state of the tunnel. Afterwards, the thermal insulation effect and the effect of location of thermal insulation layer on thermal state are analyzed. Subsequently, the methods on thermal conductivity and thickness of thermal insulation layer are constructed and the relationship among the insulation effect, thermal conductivity and thickness is obtained for heat insulation effect.
25 June 2018
Numerical study of the effect of the cavity depth on the leakage control in a cooled honeycomb-tip turbine cascade
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Yabo Wang, Yanping Song, Jianyang Yu, Fu Chen The effect of the cavity depth on the leakage flow and tip cooling has been numerically investigated in a honeycomb-tip turbine cascade with cooling injection. Coolant is ejected through the center holes on the honeycomb cavity bottoms. Three dimensional flow fields were simulated using the Reynolds-averaged Navier-Stokes (RANS) method and the k-
25 June 2018
The dual-port fuel injection system for fuel economy improvement in an automotive spark-ignition gasoline engine
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Yonggyu Lee, Seungmook Oh, Changup Kim, Junsun Lee, Kanghun Lee, Junghwan Kim The purpose of the present study was to investigate the performance of the dual-port injection (DPI) system in an automotive spark-ignition engine. The DPI system utilizes two port fuel injection (PFI) injectors per cylinder, i.e., one injector at each intake port. An original 4-cylinder PFI engine head was modified to accommodate total 8 PFI injectors. In the present study, three spray angles and two install configurations were investigated in the intake port visualization, steady-state part-load experiments, and cold-start experiment. The intake port spray visualization experiment showed that the wider fuel spray provided better fuel distribution, but also more wall wetting. The steady-state engine experiment at the several critical part-load conditions showed that the DPI system in combination with the open-valve-injection strategy achieved the most brake specific fuel consumption (BSFC) reduction of 4.6%. The average BSFC reduction of the 9-point experiment was 2.8%. The cold-start experiment also showed a fuel economy gain by the DPI system. In the cold-start experiment the wider spray angle exhibited higher total hydrocarbon emission likely due to the greater wall wetting observed in the intake port spray images.
25 June 2018
Analysis on integrated low grade condensation heat powered desiccant coated vapor compression system
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): T.S. Ge, Y.J. Dai, R.Z. Wang Hybrid solid desiccant and vapor compression system is developed to realize independent control of temperature and humidity. However the large volume has always hindered further development and heat pump system based on desiccant coated heat exchanger (DCHE) is proposed to solve the problem. It’s DCHE instead of conventional sensible heat exchanger is adopted as evaporator/condenser in this system, which also serves as a bridge to link conventional solid desiccant system and vapor compression system together. Simulation model is established in this paper to analyze system performance operating as separate air conditioner. It is found that under new operation condition with higher evaporation temperature and taking COP, pressure and flammability into account, R134a is recommended as refrigerant. Switch time is identified as crucial parameter to avoid condensation. In full fresh air mode, 20–300
25 June 2018
Recovery of thermal energy released in the composting process and their conversion into electricity utilizing thermoelectric generators
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): C
25 June 2018
Parametric analysis on the thermal comfort of a cooling tower based thermally activated building system in tropical climate – An experimental study
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): D.G. Leo Samuel, S.M. Shiva Nagendra, M. Prakash Maiya Thermally Activated Building System (TABS) provides not only better thermal comfort but also good indoor air quality. It can be coupled with passive cooling systems as it can operate at a relatively higher water temperature. Even though TABS is a promising energy-efficient and eco-friendly system, the influences of various design and operating parameters on the indoor thermal comfort of a building with TABS are not well understood. Hence, the influences of cooling surfaces (area), shading, natural ventilation and ceiling fan on the performance of cooling tower based TABS were investigated in an experimental room of dimensions 3.5
25 June 2018
Modeling of the co-pyrolysis of rubber residual and HDPE waste using the distributed activation energy model (DAEM)
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Qi Hui Ng, Bridgid Lai Fui Chin, Suzana Yusup, Adrian Chun Minh Loy, Kelly Yi Ying Chong The kinetic analysis for rubber residual i.e. rubber seed shell, high density polyethylene (HDPE) waste and its mixture are investigated using distributed activation energy model (DAEM) reaction model. Furthermore, the pyrolysis characteristics from these materials are investigated by non-isothermal thermogravimetric analysis from temperature 323
25 June 2018
Electrically-induced ionic wind flow distribution and its application for LED cooling
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Jing Wang, Yi-xi Cai, Xiao-hua Li, Yun-fei Shi, Ya-chao Bao Enhanced heat transfer based on electrohydrodynamic (EHD) is considered as energy efficient non-thermal technology appropriate for thermal management of microelectronic products. A ‘multiple-needles-to-mesh’ electrostatic fluid accelerator (EFA) was proposed and experiments were carried out to clarify the ionic wind distribution characteristic and to evaluate the energy efficiency of the device. A developed prototype of EFA was then manufactured and applied for cooling high power LEDs. The results revealed significant effects of discharge gap, radius of needle tip curvature, distance between adjacent needles, power polarity and corona power on ionic wind flow distribution. The electric current density is highly uneven which lead to inhomogeneous ionic wind distribution. The maximum ionic wind velocity was obtained close to the emitting electrode and the maximum cone angle of the designed EFA is 61.6°. The experimental study indicated that the designed EFA was effective for heat dissipation of high power LEDs in application. The attenuation rate of luminous flux and the rise rate of junction temperature were much lower than traditional cooling devices.
25 June 2018
Numerical investigation on heat transfer of supercritical carbon dioxide in a vertical tube under circumferentially non-uniform heating
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Y.H. Fan, G.H. Tang Heat transfer characteristics of supercritical carbon dioxide in circumferentially non-uniform heated vertical upward flow near critical point are reported. Stainless steel tube with internal diameter of 38
25 June 2018
Part-load performance modelling of a reheated humid air turbine power cycle
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Giovanni D. Brighenti, Pavlos K. Zachos, Pau Lluis Orts-Gonzalez Humid air turbines have previously demonstrated the potential to deliver high efficiency and power output combined with low emissions. This paper investigates the part-load performance of a 40
25 June 2018
Ammonia lithium nitrate and ammonia sodium thiocyanate double effect absorption refrigeration systems: Thermodynamic analysis
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): L. Garousi Farshi, S. Asadi This paper presents a comparison of the performance for three configurations of double effect absorption refrigeration systems with single effect one using ammonia lithium nitrate (NH3/LiNO3) and ammonia sodium thiocyanate (NH3/NaSCN) as working solutions. The effect of operating parameters on COP and exergetic efficiency of the cycles is investigated. In order to avoid error in estimation of solutions enthalpy and entropy at high temperatures, linear equations for specific heat of solutions are obtained from correlating the experimental data. Furthermore, the effects of operating parameters on crystallization possibility are studied. The COP of double effect systems are maximum 60% more, but exergetic efficiency is maximum 16% less than those for single effect cycles. The NH3/LiNO3 systems compared to the NH3/NaSCN systems can perform at lower generator temperatures with higher COP and exergetic efficiency. Operating range of NH3/LiNO3 system is wider, since it is limited for NH3/NaSCN cycle because of crystallization occurrence.
25 June 2018
Experimental study on performance change with time of solar adsorption refrigeration system
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Q.F. Chen, S.W. Du, Z.X. Yuan, T.B. Sun, Y.X. Li Under the solar heating condition, the performance of the adsorption refrigeration system using SAPO-34 zeolite and water as the working pair was tested practically. The experiment provided insights into the dynamic change of the temperature and pressure in the adsorption bed, as well as the effect of the cycle time on the system performance. By analyzing the relationship between the solar energy input and the cooling output, the optimal cycle time of the system was identified. It was revealed that both the performance coefficient COP and the specific cooling power SCP presented a maximum value with respect to the adsorption time as the system was evaluated by the whole cycle time. However, the COP and the SCP did not share the same adsorption time for their maximum values. The characteristic for the bed to decrease the adsorption rate with the time is considered to be responsible to interpret the optimal cycle time of the system. The overlong time of adsorption did not help to improve the cooling performance of the system.
25 June 2018
Determination of optimum operation conditions in an ultrasound assisted fibrous porous media drying process
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Panpan Li, Zhenqian Chen, Lisha Sheng Ultrasound technology has a great potential in fibrous porous media dehydration process, and the effectiveness is affected by ambient condition and material parameters. For quantitative evaluation the effect of ambient temperature, relative humidity, air velocity, moisture ratio and material thickness on ultrasonic enhancement, this paper has made an investigation on eight different drying models, i.e., the Newton, the Page, the Modified Page, the Henderson and Pabis, the Logarithmic, the Two term, the Two term exponential and the Midilli model. The result shows that, the Modified Page model is much more accurate than the others in describing the fibrous porous media dehydration process assisted by the power ultrasound. The role of ultrasound in dehydration appears to be more important under lower ambient temperature, proper air velocity and higher relative humidity. Beyond that, the effectiveness of ultrasound application increases with the rising of the initial moisture ratio and material thickness.
25 June 2018
Time-domain transient fluorescence spectroscopy for thermal characterization of polymers
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Hao Wu, Kai Cai, Hongtao Zeng, Wensheng Zhao, Danmei Xie, Yanan Yue, Yangheng Xiong, Xin Zhang In this work, a time-domain fluorescence spectroscopy technique is developed to characterize thermophysical properties of polymers. The method is based on fluorescence thermometry of materials under periodic pulse heating. In the characterization, a continuous laser (405
25 June 2018
Thermal stability of granite for high temperature thermal energy storage in concentrating solar power plants
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Baiyi Li, Feng Ju Natural rock has been considered the promising material for thermal energy storage in concentrating solar power plants at high temperatures. Rocks need to keep stable when serving as storage materials and exchanging heat with working fluid many times. To investigate the feasibility of granite in this application, this paper evaluated the thermal stability of granite, including physical and mechanical properties, subjected to different thermal cycles with temperature ranging from 20
25 June 2018
Performance improvement of gas turbine power plants by utilizing turbine inlet air-cooling (TIAC) technologies in Riyadh, Saudi Arabia
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Saleh S. Baakeem, Jamel Orfi, Hany Al-Ansary Gas turbine performance is very sensitive to the ambient air conditions, particularly in hot and arid climates. Various turbine inlet air cooling (TIAC) techniques including mechanical vapor compression and lithium bromide-water absorption refrigeration systems are used in several locations worldwide. This work concerns a comparative study using mass and energy balances and cost analysis of several cooling technologies coupled with a typical gas turbine under Riyadh weather conditions. The results are expressed in terms of yearly variations of power output, fuel consumption, and thermal efficiency of the gas turbine unit. They also include the total and operating costs and the payback period for each configuration of TIAC systems. The study proposes first systematic approaches to determine the air cooled temperature at the compressor inlet and the corresponding cooling capacity for the considered TIAC systems. The optimum values of such air cooled temperature and cooling capacity are found to be 8
25 June 2018
Truncation effects in an evacuated compound parabolic and involute concentrator with experimental and analytical investigations
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Abid Ustaoglu, Junnosuke Okajima, Xin-Rong Zhang, Shigenao Maruyama A two-stage line-axis solar concentrator composed of parabolic and involute reflectors with tubular absorber, have been designed and experimentally analyzed for thermal applications. The concentrator is covered by evacuated glass tube for low-heat loss configuration. Due to steep angle at the end of compound parabolic reflector, the concentrator tolerates to truncate a portion of the reflector with only slight reduction on the performance. Optimum truncation level is estimated by evaluating of ray acceptance, which is described as the ratio of aperture area of the concentrator to diameter of glass cover, concentration ratio, optical performance and thermal performance. The concentrator with truncation level of 50% shows preferable performance with only 1% reduction in thermal performance as well as significant reduction on material requirement. An experimental analysis was conducted for a 50% truncated concentrator to validate the ray tracing analysis and the thermal performance as a function of inlet temperature of water and the surface temperature of absorber. The experimental results show good agreement with the ray-tracing program written for theoretical evaluation. Consequently, the truncation of the concentrator provides requirement of less amount of optical component through significant reductions in size of reflector and glass cover with a small reduction in concentrator rate to achieve the economic viability and attraction for buildings.
25 June 2018
Experimental and numerical study on thermal performance of Li(NixCoyMnz)O2 spiral-wound lithium-ion batteries
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Xiaolong Yang, Pengfei Yang, Zeping Zhang, Yongkang Duan, Jihao Hu A clear understanding of thermal properties of lithium-ion batteries and their effects on battery performance is vital to design thermal management systems. The thermal characteristics of a commercial 18,650 Li(NixCoyMnz)O2 Lithium-ion battery is studied under constant current discharge rates of 1
25 June 2018
Design and fabrication of a hydroformed absorber for an evacuated flat plate solar collector
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): R.W. Moss, G.S.F. Shire, P. Henshall, P.C. Eames, F. Arya, T. Hyde The concept of an evacuated flat plate collector was proposed over 40
25 June 2018
Optimization of heat transfer enhancement and pumping power of a heat exchanger tube using nanofluid with gradient and multi-layered porous foams
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Majid Siavashi, Hamid Reza Talesh Bahrami, Ehsan Aminian Nanofluids and porous inserts are two traditional methods of enhancing heat transfer. Porous media improve heat transfer along with increasing the pressure drop. This study aims to use gradient and multi-layered porous media (GPM and MLPM) with optimized properties and arrangement to maximize the heat transfer and minimize the pressure drop. Fluid flow in a pipe filled with GPM or MLPM is numerically simulated using ANSYS-FLUENT; where the properties of each layer consisting the porosity and the particle size (or permeability) of the porous medium can be adopted independently. First, simple arrangements of porous layers including constant, linear or stepwise increasing or decreasing of particle size (Case I) or porosity (Case II) of layers with respect to the radius are investigated. Results show that the stepwise and linear profiles both in Case I and Case II have nearly the same performance evaluation criteria (PEC) values. Particle swarm optimization (PSO) algorithm is used to find the optimal arrangements of porous layers in the both cases to maximize PEC value. Results show that the optimal arrangement of Case I and Case II gives PEC of 0.845 and 0.789, respectively. In addition, simultaneous optimization of Case I and Case II gives a higher PEC (0.856). Finally, using alumina/water nanofluid (5%) in the simultaneous optimized conditions improves PEC about 3 times.
25 June 2018
Advanced heat transfer analysis of a U-shaped pulsating heat pipe considering evaporative liquid film trailing from its liquid slug
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Reza Nemati, Mohammad Behshad Shafii In order to study the heat transfer mechanism and predict the heat transfer capability of a pulsating heat pipe (PHP), a numerical model was used to simulate the oscillating behavior of liquid slug considering liquid film thickness in the evaporator and reduction of liquid film thickness due to evaporation. In this article, thermal performance of an open loop closed end PHP of copper with a diameter of 1
25 June 2018
High-grade energy compensation ratio in a conventional subcritical vapour-compression heat-pump cycle
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Dehu Qv, Jijin Wang, Runxin Shang, Long Ni, Yang Yao The concept of high-grade energy compensation (HGEC) has been developed and derived based on thermodynamic analysis for better understanding and assessing the high-grade energy-use efficiency in a conventional subcritical vapour-compression heat-pump (VCHP) cycle. The derivation proposes a lower limit of HGEC ratio in a conventional subcritical VCHP cycle, meaning that the COP and/or EER that we get used to employing for assessing energy efficiency tend to overestimate the high-grade energy-use efficiency.
25 June 2018
CHF correlation of boiling in FC-72 with micro-pin-fins for electronics cooling
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Yonghai Zhang, Jie Zhou, Wenjing Zhou, Baojin Qi, Jinjia Wei An experimental study of pool boiling heat transfer was conducted for micro-pin-finned surfaces with different pitches (45, 60, and 75
25 June 2018
Thermal characterization of full-scale PCM products and numerical simulations, including hysteresis, to evaluate energy impacts in an envelope application
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Kaushik Biswas, Yash Shukla, Andre Desjarlais, Rajan Rawal This article presents combined measurements of fatty acid-based organic PCM products and numerical simulations to evaluate the energy benefits of adding a PCM layer to an exterior wall. The thermal storage characteristics of the PCM were measured using a heat flow meter apparatus (HFMA). The PCM characterization is based on a recent ASTM International standard test method, ASTM C1784. The PCM samples were subjected to step changes in temperature and allowed to stabilize at each temperature. By measuring the heat absorbed or released by the PCM, the temperature-dependent enthalpy functions for melting and freezing were determined. The simulations were done using a previously-validated two-dimensional (2D) wall model containing a PCM layer and incorporating the HFMA-measured enthalpy functions. The wall model was modified to include the hysteresis phenomenon observed in PCMs, which is reflected in different melting and freezing temperatures of the PCM. Simulations were done with a single enthalpy curve based on the PCM melting tests, both melting and freezing enthalpy curves, and with different degrees of hysteresis between the melting and freezing curves. Significant differences were observed between the thermal performances of the modeled wall with the PCM layer under the different scenarios.
25 June 2018
An adaptive flow path regenerator used in supercritical carbon dioxide Brayton cycle
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Miao Ding, Jian Liu, Wen-Long Cheng, Wen-Xu Huang, Qi-Nie Liu, Lei Yang, Shi-Yi Liu The supercritical CO2 recompression Brayton cycle is proposed to be used as a typical application in 4th generation reactors. In the cycle, the performance of the regenerator has a significant impact on the performance of the entire cycle. As the specific heat capacity and density of SCO2 change significantly with the temperature and pressure. Therefore, in this paper, a new adaptive flow path regenerator is proposed and designed in order to further improve the performance of the regenerator, in which the flow path sizes varied with the CO2 density when the CO2 flowing through the regenerator. Firstly, the heat transfer performance and hydraulic performance of the adaptive flow path regenerators are analyzed in detail by simulation, and it is verified in theory that the design of new adaptive regenerator is feasible. Then, a new adaptive flow path regenerator with S-shaped fins is manufactured by metal 3D printing technology and the performances of the new regenerator are tested by a SCO2 experimental platform. The experimental results are consistent with simulation results and show that the performances of the new regenerator are significantly improved: the pressure loss can be reduced up to 69%, the effectiveness can be increased by nearly 2%, and the compactness and heat transfer rate can be improved at the same time.
25 June 2018
Exploring optimal operating conditions for wet ethanol use in spark ignition engines
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): R.L. Sari, D. Golke, H.J. Enzweiler, N.P.G. Salau, F.M. Pereira, M.E.S. Martins Of all the biofuels available in the market, ethanol seems to be the most promising one for spark-ignited engines. However, its lower calorific value makes operation more expensive due to increased volumetric fuel consumption, when compared to gasoline. Measures that further increase efficiency and that reduce fuel costs are necessary for a more widespread use. Hence, the use of ethanol with increased hydration may be the answer for reducing fuel costs while contributing for increased efficiency should the properties of this blend are properly addressed. Previous studies reported an important increase in knock resistance for ethanol–water fuel blends with high water content, the so-called “wet ethanol”. This work explored this phenomenon by increasing the compression ratio of the engine. It was investigated the limiting conditions with respect to spark advance and compression ratio through ignition timing sweep. The direct impact on combustion and emissions parameters of using wet ethanol with higher compression ratios was also evaluated. Ethanol-water fuel blends containing 4%, 10%, 20% and 30% v/v of water in ethanol were tested and compared in engine tests. For each of the fuel blends it was assessed three different compression ratios (12.5, 13.5 and 14.5:1). The results showed that ethanol–water fuel blends with high water content allow working with optimum combustion phasing even for compression ratios of 14.5:1. It leads to an increase of 7% in the indicated efficiency values for E80W20 when compared to commercial ethanol with 4% hydration. Emissions results were similar to those of commercial ethanol. Thus, this work shows that E80W20 is an optimum blend for increased engine efficiency and similar emissions of those of E4W96 while reducing fuel production costs.
25 June 2018
Heat transfer and flow characteristics of impinging jet on a concave surface at small nozzle to surface distances
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Amirhosein Hadipour, Mehran Rajabi Zargarabadi Experimental and numerical investigations were carried out to analyze the flow and heat transfer characteristics of an impinging jet on a concave surface at small jet-to-surface distances. Constant heat flux of 2000
25 June 2018
Sequential application of microwave and conventional heating methods for preparation of activated carbon from biomass and its methylene blue adsorption
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): Orhan Baytar,

Flow boiling heat transfer to MgO-therminol 66 heat transfer fluid: Experimental assessment and correlation development
Publication date: 25 June 2018
Source:Applied Thermal Engineering, Volume 138 Author(s): M.M. Sarafraz, H. Arya, M. Saeedi, D. Ahmadi An experimental investigation was performed on the flow boiling heat transfer characteristics of MgO/therminol 66 nanofluid as a potential coolant on a copper-made disc. Nanofluids were prepared using two step method at wt.%
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