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Z.G. Qu
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Journal article
Published: 09 August 2021 in Energy
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Counter-flow wet cooling towers are equipment for removing heat from water to environment. The traditional model for their thermal performance mainly focuses on the heat exchange in packing. The coupling among spray zone, rain zone, and packing are not considered. In this study, a coupling model consisting of mathematical descriptions of the spray zone, rain zone, and packing is proposed. The thermal performance is investigated based on the interaction of three zones. An actual cooling tower test report is used to validate the coupling model. Subsequently, the efficiency and exit water temperature of the cooling tower is analyzed under various conditions. The results indicate that the relative error is 5.68% when the coupling relation is neglected. The relative error is reduced to 3.25% when the spray zone and rain zone are coupled with packing. The cooling tower efficiency and exit water temperature increase with increasing air humidity, while the smaller droplets diameter and higher air-to-water mass flow rate ratio cause lower exit water temperature and higher cooling tower efficiency. Besides, the droplets velocity has little influence on these. The results of this study provide theoretical foundations for accurate performance prediction and guide the direction for cooling towers optimization.

ACS Style

J.H. Yu; Z.G. Qu; J.F. Zhang; S.J. Hu; J. Guan. Comprehensive coupling model of counter-flow wet cooling tower and its thermal performance analysis. Energy 2021, 121726 .

AMA Style

J.H. Yu, Z.G. Qu, J.F. Zhang, S.J. Hu, J. Guan. Comprehensive coupling model of counter-flow wet cooling tower and its thermal performance analysis. Energy. 2021; ():121726.

Chicago/Turabian Style

J.H. Yu; Z.G. Qu; J.F. Zhang; S.J. Hu; J. Guan. 2021. "Comprehensive coupling model of counter-flow wet cooling tower and its thermal performance analysis." Energy , no. : 121726.

Review
Published: 06 August 2021 in Electrochemical Energy Reviews
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Interest in large-scale energy storage technologies has risen in recent decades with the rapid development of renewable energy. The redox flow battery satisfies the energy storage demands well owing to its advantages of scalability, flexibility, high round-trip efficiency, and long durability. As a critical component of the redox flow battery, the bipolar plates provide mechanical support for the electrodes and act as a physical separator between adjacent cells, as well as constructing the internal circuit and guiding the electrolyte flow. The present work offers a comprehensive review of the development of bipolar plates in redox flow batteries, covering materials, structures, and manufacturing methods. In terms of materials, the effects of material types and composition on the compactness, mechanical strength, and electrical conductivity are summarized in detail. Furthermore, the corrosion mechanisms of bipolar plates and the corresponding detection and mitigation methods are discussed. In addition, the structures of the bipolar plates refer to the flow field designs on the surface. The advantages and disadvantages of these existing flow fields are described, and the tendencies for further optimization are also discussed. The manufacturing of composite bipolar plates in terms of material cost and preparation methods is also outlined. Based on the summary of previous research, this work provides suggestions for the future development of high-performance bipolar plates.

ACS Style

Zhining Duan; Zhiguo Qu; Qinlong Ren; Jianfei Zhang. Review of Bipolar Plate in Redox Flow Batteries: Materials, Structures, and Manufacturing. Electrochemical Energy Reviews 2021, 1 -39.

AMA Style

Zhining Duan, Zhiguo Qu, Qinlong Ren, Jianfei Zhang. Review of Bipolar Plate in Redox Flow Batteries: Materials, Structures, and Manufacturing. Electrochemical Energy Reviews. 2021; ():1-39.

Chicago/Turabian Style

Zhining Duan; Zhiguo Qu; Qinlong Ren; Jianfei Zhang. 2021. "Review of Bipolar Plate in Redox Flow Batteries: Materials, Structures, and Manufacturing." Electrochemical Energy Reviews , no. : 1-39.

Journal article
Published: 25 June 2021 in Energy Conversion and Management
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A solar pond is a simple and reliable system that collects and stores solar energy for applications with low-grade heat supply. The main obstacle to the long-term stable operation of a solar pond is interface erosion induced by double-diffusive convection. In this study, an active method of using an external magnetic field is proposed to repress the intense convection region and improve its corresponding operating stability. A two-dimensional transient model is developed and solved using the lattice Boltzmann method with multiple-relaxation-time collisions. The double-diffusive convection, variation of solar energy absorption to depth, and changes in solution electrical conductivity are considered in the model. The fluid flow, heat, and mass transfer characteristics were investigated under continuous high illumination with or without an external magnetic field. When magnetic control is exerted on a solar pond, the decrease in the nonconvective zone thickness caused by interface erosion changes from 14.75% to 0. The state of the solar pond is transformed from a thermally unstable state to a theoretically stable state after 35 h of continuous high illumination. Further, the external magnetic field can delay concentration homogenization and improve the heat storage performance of a lower convective zone. A Hartmann number above 56.67 is recommended to enhance the stability of the solar pond. This research sheds new light on methods to improve the long-term stability of solar ponds.

ACS Style

D. Tian; Z.G. Qu; J.F. Zhang; Q.L. Ren. Enhancement of solar pond stability performance using an external magnetic field. Energy Conversion and Management 2021, 243, 114427 .

AMA Style

D. Tian, Z.G. Qu, J.F. Zhang, Q.L. Ren. Enhancement of solar pond stability performance using an external magnetic field. Energy Conversion and Management. 2021; 243 ():114427.

Chicago/Turabian Style

D. Tian; Z.G. Qu; J.F. Zhang; Q.L. Ren. 2021. "Enhancement of solar pond stability performance using an external magnetic field." Energy Conversion and Management 243, no. : 114427.

Research article
Published: 23 June 2021 in International Journal of Green Energy
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Self-humidification is becoming a popular strategy for water management in proton exchange membrane fuel cells (PEMFCs), owing to the advantages of decreased volume, cost, and parasitic power of the hydrogen fuel cell engine. Membrane dehydration is one of the key issues that seriously affect the performance and lifespan of PEMFCs under low humidity conditions. In this work, an electrospinning approach was employed to fabricate gas diffusion layers (e-GDLs) composed of nanosized carbon fibers with a nanoscale pore structure. Further, a vapor deposition of Dow Corning Sylgard 184 was utilized to apply a hydrophobic coating to enhance the hydrophobicity of the e-GDL. The fabricated e-GDL can help alleviate the dehydration of the catalyst-coated membrane by increasing the breakthrough pressure. The breakthrough pressure of the e-GDL is five folds higher than that of the current commercial GDL, owing to the combined effects of the nanostructure and enhanced hydrophobicity. This superior characteristic is expected to effectively alleviate membrane dehydration under low humidity conditions. In addition, the e-GDL has excellent elastic deformability, which can effectively alleviate the irreversible damage caused by the pre-tightening force in the stack assembly process, thus enhancing the durability and lifetime of PEMFCs.

ACS Style

Guofu Ren; Zhiguo Qu; Xueliang Wang; Jianfei Zhang. Liquid water transport and mechanical performance of electrospun gas diffusion layers. International Journal of Green Energy 2021, 1 -9.

AMA Style

Guofu Ren, Zhiguo Qu, Xueliang Wang, Jianfei Zhang. Liquid water transport and mechanical performance of electrospun gas diffusion layers. International Journal of Green Energy. 2021; ():1-9.

Chicago/Turabian Style

Guofu Ren; Zhiguo Qu; Xueliang Wang; Jianfei Zhang. 2021. "Liquid water transport and mechanical performance of electrospun gas diffusion layers." International Journal of Green Energy , no. : 1-9.

Journal article
Published: 09 June 2021 in International Journal of Hydrogen Energy
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High water contact angle in carbon fiber can facilitate water removal ability of gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs). Water contact angle is intensively dependent on the surface hydrophobicity of carbon fiber in GDL. In this study, the hydrophobicity of commercial GDL is enhanced through the immersion and hydrothermal methods. The porosity decreases slightly while the surface roughness and surface topology diversity increase significantly in hydrothermal GDL compared with commercial reference and immersion GDL samples. The molecular dynamics simulations show that the water contact angle increases significantly with the increasing surface roughness but varies slightly with different surface topology, indicating that the water contact angle is dominated by the surface roughness. This study's findings are expected to offer an approach that can effectively enhance the water removal capacity by tailoring the surface roughness of carbon fibers in GDL materials.

ACS Style

X.L. Wang; W.K. Wang; Z.G. Qu; G.F. Ren; H.C. Wang. Surface roughness dominated wettability of carbon fiber in gas diffusion layer materials revealed by molecular dynamics simulations. International Journal of Hydrogen Energy 2021, 46, 26489 -26498.

AMA Style

X.L. Wang, W.K. Wang, Z.G. Qu, G.F. Ren, H.C. Wang. Surface roughness dominated wettability of carbon fiber in gas diffusion layer materials revealed by molecular dynamics simulations. International Journal of Hydrogen Energy. 2021; 46 (52):26489-26498.

Chicago/Turabian Style

X.L. Wang; W.K. Wang; Z.G. Qu; G.F. Ren; H.C. Wang. 2021. "Surface roughness dominated wettability of carbon fiber in gas diffusion layer materials revealed by molecular dynamics simulations." International Journal of Hydrogen Energy 46, no. 52: 26489-26498.

Journal article
Published: 05 June 2021 in Electrochimica Acta
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Understanding current distribution in operating Vanadium redox flow batteries (VRFBs) is vital for improving battery design and performance as the non-uniform current density distribution is known as a major cause of the corrosion and side reactions in VRFBs. However, the existing method for current density measurement in the VRFB with flow field is complex and the rib conductive structure of graphite plate is changed which reduces the measurement accuracy and reliability. In this study, we propose a novel pluggable current collector for in-operando current distribution measurements which greatly simplifies the current density distribution measurement process in VRFBs with flow field. The new method relies on eight pluggable graphite units in a flow plate frame to replicate the actual serpentine flow field structure, thereby providing higher measurement reliability compared to the existing methods which are mostly invasive. Using the new method, current density distributions at different electrode compression ratios (CR) and inflow electrolyte rates are investigated. It is found that insufficient supplemental reactant in electrode border region is the main reason for the uneven current density distribution and the current density non-uniformity is intensified in the initial and final stages of cycling process. Increasing CR can improve the current density in the electrode core region. The overall current density uniformity in a VRFB with serpentine flow field can be enhanced by increasing the inflow electrolyte rate. The developed method is believed to facilitate the understanding of the coupled local reactions and transport processes and guide on the future design of VRFBs.

ACS Style

Qiong Wang; Zhiguo Qu; Zhiyuan Jiang; Jin Xuan; Huizhi Wang. A pluggable current collector for in-operando current measurements in all-vanadium redox flow batteries with flow field. Electrochimica Acta 2021, 389, 138725 .

AMA Style

Qiong Wang, Zhiguo Qu, Zhiyuan Jiang, Jin Xuan, Huizhi Wang. A pluggable current collector for in-operando current measurements in all-vanadium redox flow batteries with flow field. Electrochimica Acta. 2021; 389 ():138725.

Chicago/Turabian Style

Qiong Wang; Zhiguo Qu; Zhiyuan Jiang; Jin Xuan; Huizhi Wang. 2021. "A pluggable current collector for in-operando current measurements in all-vanadium redox flow batteries with flow field." Electrochimica Acta 389, no. : 138725.

Journal article
Published: 01 June 2021 in AIP Advances
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With the development of applications for microelectromechanical system (MEMS) components and micromachining technology, planar microelectrodes have attracted considerable interest. To study the discharge characteristics of these structures, planar microelectrodes with a variety of plate-shaped and needle-shaped microelectrode structures fabricated from indium tin oxide (ITO) and copper (Cu) with microelectrode gaps ranging from 5 to 35 µm were manufactured using MEMS technology in this study. Experiments carried out in atmospheric air show that the microelectrode configuration has a crucial impact on the discharge current, breakdown voltage, and current response to varying electrode gaps. The electrode surface area plays a significant role in the discharge characteristics of planar microelectrodes, which is a factor dominating the discharge current and breakdown voltage. The commonly used formulas in macroscale corona discharge cannot be directly applied to planar microelectrodes. Planar microelectrodes fabricated with Cu on Si substrates have larger discharge currents, higher breakdown voltages, and better resistance to breakdown strength than ITO ones on quartz substrates under nA-scale current, while ITO damaged microelectrodes because of breakdown can still discharge when accompanied by different discharge characteristics.

ACS Style

J. F. Zhang; D. W. Zhang; X. W. Wu; Q. L. Ren; Z. G. Qu. Current–voltage characteristics and breakdown of different structural planar microelectrodes in atmospheric air. AIP Advances 2021, 11, 065301 .

AMA Style

J. F. Zhang, D. W. Zhang, X. W. Wu, Q. L. Ren, Z. G. Qu. Current–voltage characteristics and breakdown of different structural planar microelectrodes in atmospheric air. AIP Advances. 2021; 11 (6):065301.

Chicago/Turabian Style

J. F. Zhang; D. W. Zhang; X. W. Wu; Q. L. Ren; Z. G. Qu. 2021. "Current–voltage characteristics and breakdown of different structural planar microelectrodes in atmospheric air." AIP Advances 11, no. 6: 065301.

Journal article
Published: 24 May 2021 in Electrochimica Acta
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Alternative refrigeration systems have been explored due to the limitations of vapor compression refrigeration system on theoretical efficiency and environmental friendliness. In this study, an electrochemical refrigeration system based on the endothermic effect of electrochemical reactions was proposed to realize continuous refrigeration. This electrochemical refrigeration system mainly comprised endothermic and exothermic cell stacks, regenerator, heat exchangers, and pumps. Fe2+/Fe3+ and VO2+/VO2+ redox couples were employed to establish a refrigeration cycle due to their large entropy change and no phase change during reaction processes. A thermodynamic model with polarization loss analysis was established for system performance evaluation. Through quantitative analysis of polarization losses, optimal operating conditions of the system and key factors affecting the system performance were determined. The results indicated that the coefficient of performance (COP) of the system under ideal conditions was close to that of the reverse Carnot cycle. In actual situations, polarization losses led to system performance degradation. The electrochemical refrigeration system achieved comparable or better COP than the vapor compression refrigeration system when the current density was within 60 A m−2. The impact analysis of state of charge (SOC) showed that the actual refrigerating capacity and COP reached the peak values when the SOC was about 0.43 and 0.5, respectively. Increasing the flow rate and operating temperature improved the system performance by decreasing concentration and activation polarization losses, respectively. Furthermore, the activation polarization loss accounted for the largest proportion of system losses. Thus, improving electrode catalysis is critical to enhance the system performance.

ACS Style

Z.N. Duan; Z.G. Qu; J.F. Zhang. Thermodynamic and electrochemical performance analysis for an electrochemical refrigeration system based on iron/vanadium redox couples. Electrochimica Acta 2021, 389, 138675 .

AMA Style

Z.N. Duan, Z.G. Qu, J.F. Zhang. Thermodynamic and electrochemical performance analysis for an electrochemical refrigeration system based on iron/vanadium redox couples. Electrochimica Acta. 2021; 389 ():138675.

Chicago/Turabian Style

Z.N. Duan; Z.G. Qu; J.F. Zhang. 2021. "Thermodynamic and electrochemical performance analysis for an electrochemical refrigeration system based on iron/vanadium redox couples." Electrochimica Acta 389, no. : 138675.

Journal article
Published: 19 May 2021 in Applied Thermal Engineering
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As high-quality food preservation has become an important aspect of daily life, a need has developed for domestic household refrigerators with a wide refrigeration temperature range. The temperature range of domestic household refrigerators is generally above −20 °C. In this study, a hybrid refrigeration system that combined vapor compression refrigeration (VCR) and a thermoelectric refrigerator (TER) is investigated for the freezer compartment of a domestic refrigerator with a volume of 0.018 m3. Although an additional 99.5 W of electrical power is consumed, a lower temperature of −38.1 °C is experimentally achieved in the deep freezer compartment of a compact VCR–TER system, with no noise or mechanical parts. In contrast, a temperature of only −8.8 °C is obtained in a typical VCR system. A three-dimensional numerical model is applied to study the performance of the finned heat sink of the TER using FLUENT. The effects of the fin height and fin pitch on the thermal resistance and pressure drop are investigated. The results show that the thermal resistance decreases with an increase in the fin height and increases with an increase in the fin pitch. An optimized finned heat sink with a fin height of 50 mm is obtained, which has a thermal resistance of 0.05 °C/W. It has a higher cooling capacity of 53.6 W than the heat sink with the original fin height of 30 mm. The VCR–TER system has potential application to low-temperature domestic refrigeration systems with a small size and small cooling capacity.

ACS Style

R.P. Fu; Z.G. Qu; W.Q. Tao; X.B. Zhu; J.R. Liu. Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems. Applied Thermal Engineering 2021, 194, 117107 .

AMA Style

R.P. Fu, Z.G. Qu, W.Q. Tao, X.B. Zhu, J.R. Liu. Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems. Applied Thermal Engineering. 2021; 194 ():117107.

Chicago/Turabian Style

R.P. Fu; Z.G. Qu; W.Q. Tao; X.B. Zhu; J.R. Liu. 2021. "Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems." Applied Thermal Engineering 194, no. : 117107.

Accepted manuscript
Published: 13 May 2021 in Journal of Physics D: Applied Physics
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Efficient separation of oil droplet from oily wastewater is an inevitable task for handling world water crisis and environmental pollution. However, the existing passive oil/water separation technologies suffer from drawbacks of relatively low separation efficiency or strict material requirement. We present an active dielectrophoretic oil/water separation technique without inducing further environmental contamination. Based on the non-uniform electric field generated through insulated nanopore under direct current (DC) voltage, oil droplet confronts negative dielectrophoresis (nDEP) force because of its relatively weaker dielectric property compared with wastewater. Meanwhile, electroosmotic flow also occurs in oil/water separation device due to the ion motion inside electric double layer (EDL) of nanopore solid surface. Through developing a multi-physical model for immiscible oil/water flow under hybrid electrokinetic effects, the oil/water separation is investigated at different parametric conditions. Electrokinetic filtration of oil droplet through nanopore is successfully achieved when nDEP force is dominant rather than electroosmotic electrohydrodynamic (EHD) force for oil droplet movement. To enhance oil/water separation rate, the relative strength between nDEP force to EHD force on oil droplet is consolidated via increasing DC voltage, decreasing surface charge density, and optimizing nanopore configuration. The designed active oil/water separation using DC-DEP offers significant potential for future oily wastewater treatment.

ACS Style

Qinlong Ren; Zexiao Wang; Ning Liu; Jian-Fei Zhang; Zhiguo Qu. Nanopore-based active oil droplet filtration under negative DC dielectrophoresis for oily wastewater treatment. Journal of Physics D: Applied Physics 2021, 54, 345302 .

AMA Style

Qinlong Ren, Zexiao Wang, Ning Liu, Jian-Fei Zhang, Zhiguo Qu. Nanopore-based active oil droplet filtration under negative DC dielectrophoresis for oily wastewater treatment. Journal of Physics D: Applied Physics. 2021; 54 (34):345302.

Chicago/Turabian Style

Qinlong Ren; Zexiao Wang; Ning Liu; Jian-Fei Zhang; Zhiguo Qu. 2021. "Nanopore-based active oil droplet filtration under negative DC dielectrophoresis for oily wastewater treatment." Journal of Physics D: Applied Physics 54, no. 34: 345302.

Journal article
Published: 05 May 2021 in Energies
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Frost deposits on the outdoor heat exchanger of an air source heat pump (ASHP) air conditioner and reduces its capacity during winter operation. However, the prevailing reverse-cycle defrosting (RCD) turns the indoor heat exchanger into an evaporator and ceases heat supply to the living space. Consequently, the thermal comfort for indoor occupants is deteriorated. This article proposes a heater-assisted ASHP to tackle this problem. With an 800 W electromagnetic heater equipped upstream of the outdoor heat exchanger to provide refrigerant with additional heat, the ASHP retarded frost under original throttling control and compressor speed during the heating cycle (frostless mode), and even removed frost with uninterrupted heat supply to indoor space under little throttling and reduced compressor speed (anti-frost mode). Compared with the original operation of the ASHP when the heater was off (baseline mode), frostless and anti-frost modes extended heating duration by 17.9% and 99.7%, respectively, with comparative time-averaged supply-air temperature. Moreover, COP for baseline and anti-frost modes was similar by average, about 3% higher than for the frostless mode. Further optimizations will be done on the co-adjustment of throttling control and compressor speed to better fulfill the potential of the heater-assisted ASHP.

ACS Style

Fei Wang; Rijing Zhao; Wenming Xu; Dong Huang; Zhiguo Qu. A Heater-Assisted Air Source Heat Pump Air Conditioner to Improve Thermal Comfort with Frost-Retarded Heating and Heat-Uninterrupted Defrosting. Energies 2021, 14, 2646 .

AMA Style

Fei Wang, Rijing Zhao, Wenming Xu, Dong Huang, Zhiguo Qu. A Heater-Assisted Air Source Heat Pump Air Conditioner to Improve Thermal Comfort with Frost-Retarded Heating and Heat-Uninterrupted Defrosting. Energies. 2021; 14 (9):2646.

Chicago/Turabian Style

Fei Wang; Rijing Zhao; Wenming Xu; Dong Huang; Zhiguo Qu. 2021. "A Heater-Assisted Air Source Heat Pump Air Conditioner to Improve Thermal Comfort with Frost-Retarded Heating and Heat-Uninterrupted Defrosting." Energies 14, no. 9: 2646.

Journal article
Published: 04 April 2021 in International Journal of Heat and Mass Transfer
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Multilayered insulation composites are characterized by their light weight, low thermal conductivity (TC), and good wave permeability and are widely used as heat-insulating materials in aerospace engineering. The existing direct measurement standards and equipment are not applicable in high-temperature, high-radiation, and low-pressure environments for materials whose thermal conductivities are similar to that of air. Moreover, the thermal responses of a multilayered insulation composite to the same boundary conditions resulting from different operation environments are different as a result of its wave permeability and spectral selectivity. The effective TCs are different in different operation environments. There is inevitably a non-negligible thermal contact conductance (TCC) between the individual layers. Thus, it is important to measure the effective TC of a multilayered insulation composite under normal working conditions in different operating environments for the thermal design of the insulation layer. In this study, an indirect measurement strategy based on inverse problem analysis was proposed to simultaneously estimate the TC and TCC of a multilayered insulation composite. The conjugate gradient method was used for the parameter and function estimations of the TC and TCC. The accuracy and robustness of the proposed method were verified numerically and experimentally. The results of a heat-shielding experiment showed no more than a 2.4% deviation for the estimated TC and 11.5% deviation between the measured and estimated temperatures. This method may offer a strategy to measure the thermophysical properties of multilayered insulation composites in an operational environment for aerospace engineering. It can improve the TC measurement accuracy and provide the basis of the physical properties for the thermal insulation design of multilayered insulation composites for use in various operation environments.

ACS Style

J. Guo; X.N. Chen; Z.G. Qu; Q.L. Ren. Reverse identification method for simultaneous estimation of thermal conductivity and thermal contact conductance of multilayered composites. International Journal of Heat and Mass Transfer 2021, 173, 121244 .

AMA Style

J. Guo, X.N. Chen, Z.G. Qu, Q.L. Ren. Reverse identification method for simultaneous estimation of thermal conductivity and thermal contact conductance of multilayered composites. International Journal of Heat and Mass Transfer. 2021; 173 ():121244.

Chicago/Turabian Style

J. Guo; X.N. Chen; Z.G. Qu; Q.L. Ren. 2021. "Reverse identification method for simultaneous estimation of thermal conductivity and thermal contact conductance of multilayered composites." International Journal of Heat and Mass Transfer 173, no. : 121244.

Journal article
Published: 20 February 2021 in Membranes
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Minimizing platinum (Pt) loading while reserving high reaction efficiency in the catalyst layer (CL) has been confirmed as one of the key issues in improving the performance and application of proton exchange membrane fuel cells (PEMFCs). To enhance the reaction efficiency of Pt catalyst in CL, the interfacial interactions in the three-phase interface, i.e., carbon, Pt, and ionomer should be first clarified. In this study, a molecular model containing carbon, Pt, and ionomer compositions is built and the radial distribution functions (RDFs), diffusion coefficient, water cluster morphology, and thermal conductivity are investigated after the equilibrium molecular dynamics (MD) and nonequilibrium MD simulations. The results indicate that increasing water content improves water aggregation and cluster interconnection, both of which benefit the transport of oxygen and proton in the CL. The growing amount of ionomer promotes proton transport but generates additional resistance to oxygen. Both the increase of water and ionomer improve the thermal conductivity of the C. The above-mentioned findings are expected to help design catalyst layers with optimized Pt content and enhanced reaction efficiency, and further improve the performance of PEMFCs.

ACS Style

Wenkai Wang; Zhiguo Qu; Xueliang Wang; Jianfei Zhang. A Molecular Model of PEMFC Catalyst Layer: Simulation on Reactant Transport and Thermal Conduction. Membranes 2021, 11, 148 .

AMA Style

Wenkai Wang, Zhiguo Qu, Xueliang Wang, Jianfei Zhang. A Molecular Model of PEMFC Catalyst Layer: Simulation on Reactant Transport and Thermal Conduction. Membranes. 2021; 11 (2):148.

Chicago/Turabian Style

Wenkai Wang; Zhiguo Qu; Xueliang Wang; Jianfei Zhang. 2021. "A Molecular Model of PEMFC Catalyst Layer: Simulation on Reactant Transport and Thermal Conduction." Membranes 11, no. 2: 148.

Journal article
Published: 23 January 2021 in Applied Thermal Engineering
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Latent heat thermal energy storage is an essential technology for addressing the intermittent nature of solar energy, owing to its large energy storage density. However, the low thermal conductivity of phase change material hinders the energy storage efficiency. In the current work, high thermal conductive woven metal fibers are inserted into phase change material to improve its heat transfer rate. The corresponding energy storage process in a latent heat storage unit is investigated, based on pore-scale three-dimensional lattice Boltzmann modeling via numerically reconstructing the fiber morphology. The results indicate that woven metal fibers with optimum porosity should be used to balance the heat transfer capability and energy storage capacity of the woven metal fiber-phase change material composite. In addition, curved woven metal fibers exhibit better thermal performance in a latent heat storage unit than straight woven metal fibers at a high porosity of 0.95. However, straight woven metal fibers are more effective than curved woven metal fibers for enhancing the heat transfer rate of phase change material at a relatively low porosity of 0.90. Importantly, the energy storage rate could be accelerated by 40% through consolidating the anisotropic degree of woven metal fibers with fully unidirectional configuration owing to their enhanced heat transfer in the desired direction. Besides, the heat conduction inside the woven metal fiber-phase change material composite contributes to at least 71.8% of total energy storage amount during conjugate heat transfer, demonstrating its dominant behavior rather than natural convection. Woven metal fibers with designable anisotropic characteristics exhibit evident advantages over isotropic porous media for improving the thermal performance of a latent heat storage unit.

ACS Style

Qinlong Ren; Zexiao Wang; Tao Lai; J.F. Zhang; Z.G. Qu. Conjugate heat transfer in anisotropic woven metal fiber-phase change material composite. Applied Thermal Engineering 2021, 189, 116618 .

AMA Style

Qinlong Ren, Zexiao Wang, Tao Lai, J.F. Zhang, Z.G. Qu. Conjugate heat transfer in anisotropic woven metal fiber-phase change material composite. Applied Thermal Engineering. 2021; 189 ():116618.

Chicago/Turabian Style

Qinlong Ren; Zexiao Wang; Tao Lai; J.F. Zhang; Z.G. Qu. 2021. "Conjugate heat transfer in anisotropic woven metal fiber-phase change material composite." Applied Thermal Engineering 189, no. : 116618.

Research article
Published: 13 January 2021 in Energy & Fuels
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Gas diffusion in nanoporous media is significantly different from its bulk counterpart owing to the nanoconfinement effect. In this study, a local effective diffusivity lattice Boltzmann model (LED-LBM) is proposed to explore the gas diffusion behavior under nanoconfinement. The nanoconfinement effect is incorporated into the local effective diffusivity via a spatial position-dependent mean free path. The proposed LED-LBM is validated against molecular dynamics simulation results for methane gas diffusion in a nanoscale channel. Using this model, the spatial variations in the local effective diffusivity and gas mass flux in 3D nanoporous media are visualized, and the predominant factors influencing their variation and gas diffusivity are disclosed. The results show that the spatial variation features of the local effective diffusivity and gas mass flux are strongly influenced by the pore shape and average Knudsen number. The gas diffusivity in nanoporous media is significantly lower than its bulk counterpart owing to the nanoconfinement effect, and their differences increase with the average Knudsen number. To quantify the magnitude of the nanoconfinement effect, a new concept, namely, the confinement scope, is further defined. Finally, a semiempirical formula is established to predict the gas diffusivity in nanoconfined porous media, which is expressed as a function of the bulk diffusivity, average Knudsen number, and porosity.

ACS Style

Ying Yin; Zhiguo Qu; Chuanyong Zhu; Jianfei Zhang. Visualizing Gas Diffusion Behaviors in Three-Dimensional Nanoporous Media. Energy & Fuels 2021, 35, 2075 -2086.

AMA Style

Ying Yin, Zhiguo Qu, Chuanyong Zhu, Jianfei Zhang. Visualizing Gas Diffusion Behaviors in Three-Dimensional Nanoporous Media. Energy & Fuels. 2021; 35 (3):2075-2086.

Chicago/Turabian Style

Ying Yin; Zhiguo Qu; Chuanyong Zhu; Jianfei Zhang. 2021. "Visualizing Gas Diffusion Behaviors in Three-Dimensional Nanoporous Media." Energy & Fuels 35, no. 3: 2075-2086.

Paper
Published: 21 December 2020 in Soft Matter
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MD simulations explain the adsorption mechanism between patchy NPs and human serum albumin, and the interaction mechanism between NPs–HSA and membrane.

ACS Style

Xiaocong He; Lingxiao Li; Yuanyuan Yang; Zhaotong Dong; Lin Wang; Zhiguo Qu; Feng Xu. Tailoring patchy nanoparticle design to modulate serum albumin adsorption and membrane interaction. Soft Matter 2020, 17, 2071 -2080.

AMA Style

Xiaocong He, Lingxiao Li, Yuanyuan Yang, Zhaotong Dong, Lin Wang, Zhiguo Qu, Feng Xu. Tailoring patchy nanoparticle design to modulate serum albumin adsorption and membrane interaction. Soft Matter. 2020; 17 (8):2071-2080.

Chicago/Turabian Style

Xiaocong He; Lingxiao Li; Yuanyuan Yang; Zhaotong Dong; Lin Wang; Zhiguo Qu; Feng Xu. 2020. "Tailoring patchy nanoparticle design to modulate serum albumin adsorption and membrane interaction." Soft Matter 17, no. 8: 2071-2080.

Journal article
Published: 15 December 2020 in Energy Conversion and Management
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The photoelectric conversion efficiency generally decreases with increasing temperature of a photovoltaic (PV) panel; therefore, temperature control is the key issue in the photovoltaic/thermal (PV/T) system. We experimentally analyzed the energy conversion performance of a PV/T system combined with a latent heat solar collector under the real outdoor climate of Shanghai. The solar collector was filled with the phase change material (PCM) of fatty acid for cooling the PV panel. Five cases under different thermal regulation strategies for the PV/T-PCM system were comprehensively analyzed to optimize the system performance. The results indicated that the temperature stratification of PCM was still significant in the solar collector even when metal fins were employed. The temperature fluctuation of the PV panel can be well alleviated by PCM; however, the PCM was easily overheated under long-term operation of the PV/T-PCM system. Among the five cases, the overall energy efficiency of the PV/T-PCM system with full-time thermal regulation was 5.4% and 22.2% higher than the two systems without thermal regulation, respectively. The relatively low temperature setting of the thermal regulation strategy facilitated the heat transfer from the PCM. In comparison with the full-time thermal regulation strategy, the 45 °C intermittent thermal regulation strategy (Case 4) demonstrated the best performance. The total energy and exergy efficiencies of Case 4 were 86.3% and 15.5%. The exergy efficiency of thermal energy varied slightly in the range of 1.1%–1.4% for the five cases. It was concluded that the energy conversion performance of the PV/T-PCM system could be significantly improved by a suitable intermittent thermal regulation strategy.

ACS Style

Hongtao Xu; Ning Wang; Chenyu Zhang; Zhiguo Qu; Fariborz Karimi. Energy conversion performance of a PV/T-PCM system under different thermal regulation strategies. Energy Conversion and Management 2020, 229, 113660 .

AMA Style

Hongtao Xu, Ning Wang, Chenyu Zhang, Zhiguo Qu, Fariborz Karimi. Energy conversion performance of a PV/T-PCM system under different thermal regulation strategies. Energy Conversion and Management. 2020; 229 ():113660.

Chicago/Turabian Style

Hongtao Xu; Ning Wang; Chenyu Zhang; Zhiguo Qu; Fariborz Karimi. 2020. "Energy conversion performance of a PV/T-PCM system under different thermal regulation strategies." Energy Conversion and Management 229, no. : 113660.

Journal article
Published: 20 November 2020 in International Journal of Thermal Sciences
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Effective thermal management is essential for guaranteeing the working efficiency and safety of several industrial devices. Due to its excellent heat absorption characteristic, microencapsulated phase change material (MEPCM) is promising for thermal management system. However, the drawback of MEPCM's low thermal conductivity seriously hinders the heat dissipation rate from heat sink. Based on their high thermal conductivity and effective interconnected anisotropic heat transfer channels, metal fibers could be inserted into MEPCM to ameliorate its corresponding heat transfer capability. In the current work, novel stacked 2D metal fibers are designed and coupled with MEPCM in order to improve the thermal performance of heat sink. Based on the numerically reconstructed metal fibers, the thermal performance of heat sink assembly filled with MEPCM-metal fiber composite is investigated through pore-scale lattice Boltzmann modelling. When the latent heat of MEPCM is available, the heat sink assembly using anisotropic stacked 2D metal fibers has a less temperature rise compared with that using random metal fibers because of the consolidated heat transfer rate in a desired vertical direction. Furthermore, for an intermittent working heat sink, the MEPCM-stacked 2D metal fiber composite with high anisotropic degree exhibits more obvious advantage on its thermal management owing to the periodically recharged latent heat for further heat absorption.

ACS Style

Qinlong Ren; Zexiao Wang; Jianjun Zhu; Z.G. Qu. Pore-scale heat transfer of heat sink filled with stacked 2D metal fiber-PCM composite. International Journal of Thermal Sciences 2020, 161, 106739 .

AMA Style

Qinlong Ren, Zexiao Wang, Jianjun Zhu, Z.G. Qu. Pore-scale heat transfer of heat sink filled with stacked 2D metal fiber-PCM composite. International Journal of Thermal Sciences. 2020; 161 ():106739.

Chicago/Turabian Style

Qinlong Ren; Zexiao Wang; Jianjun Zhu; Z.G. Qu. 2020. "Pore-scale heat transfer of heat sink filled with stacked 2D metal fiber-PCM composite." International Journal of Thermal Sciences 161, no. : 106739.

Journal article
Published: 19 November 2020 in Applied Thermal Engineering
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Ionic wind pumps have considerable potential for flow control, heat transfer, and drying applications due to their advantages of low energy consumption, compact structure, flexible design, and lack of moving parts. However, a high flow rate ionic wind pump with large cross-sectional for cooling high thermal power electronic devices requires further research. In this study, a two-stage ionic wind pump with needle-to-mesh electrodes was developed for cooling electronics. Experimental systems were established to test the flow and heat transfer characteristics. The effects of needle electrodes’ arrangement, mesh electrodes’ structure, needle tip-to-mesh gap, and stage distance on the output velocity and power consumption of ionic wind pumps were investigated. The influence of the arrangement of an ionic wind pump and heat sink on the cooling performance was also studied. Two groups of interactive mechanisms, interference between neighboring needles and needle density, the discharge effect and the resistance effect of mesh electrodes, affected the flow characteristics. A grid size with an optimal value of 4 mm was obtained by combining the discharge and resistance effects. As the needle tip-to-mesh gap increased, the velocity at the same applied voltage decreased but the velocity limit near the breakdown voltage increased. Counter discharge between the stages induced additional power consumption. As the stage distance increased, the breakdown shifted from between two stages to within each stage. The counter discharge disappeared as the stage distance increased to greater than 29 mm. At the ionic wind pump’s optimum parameters, the output velocity of 3.91 m/s was achieved. And the cooling experiment indicated that the optimized ionic wind pump can reduced the surface temperature of a 200 W power heat source by more than 30 °C. The present study provides guidance for heat dissipation designs for maintenance-free electronics in remote areas.

ACS Style

M.J. Zeng; J.F. Zhang; S. Wang; Z.G. Qu. Analysis of a two-stage ionic wind pump with multiple needle-to-mesh electrodes for cooling electronics. Applied Thermal Engineering 2020, 185, 116340 .

AMA Style

M.J. Zeng, J.F. Zhang, S. Wang, Z.G. Qu. Analysis of a two-stage ionic wind pump with multiple needle-to-mesh electrodes for cooling electronics. Applied Thermal Engineering. 2020; 185 ():116340.

Chicago/Turabian Style

M.J. Zeng; J.F. Zhang; S. Wang; Z.G. Qu. 2020. "Analysis of a two-stage ionic wind pump with multiple needle-to-mesh electrodes for cooling electronics." Applied Thermal Engineering 185, no. : 116340.

Journal article
Published: 08 November 2020 in Renewable Energy
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Base on the GaAs plasmonic solar cell, a three-dimensional numerical model is proposed for the photoelectrical and photothermal processes. In the model, the coupled processes of nanoparticle photothermal conversion and substrate photoelectrical conversion are accounted for with FDTD solver and DEVICE solver. The Finite-Difference-Time-Domain method is used in the FDTD solver to analyze the light absorption process. The light absorption efficiency, quantum efficiency ratio of plasmonic solar cells to bare solar cells, and temperature distributions of the nanoparticles and substrate surface are obtained. A dimensionless coefficient for the substrate temperature rise is proposed to characterize the photothermal performance of the investigated plasmonic solar cell. The nanoparticles create parasitic absorption, increase substrate light scattering, and improve light absorption. Spherical Ag nanoparticles hold a higher photoelectrical conversion efficiency than spherical Au nanoparticles with an acceptable temperature increase, while spherical Au nanoparticles have stronger thermal sensitivity than spherical Ag nanoparticles. The cylindrical nanoparticles (Au or Ag) contribute significantly to the photothermal performance but do not contribute to the enhancement of the overall integrated quantum efficiency ratio. The nanoparticle arrays have accumulated heating and interference effects that enhance the thermal response. Spherical Ag nanoparticles are recommended for photoelectrical devices, while cylindrical Ag and Au nanoparticles are suitable for the development of thermal sensors.

ACS Style

J.J. Zhang; Z.G. Qu; A. Maharjan. A three-dimensional numerical study of coupled photothermal and photoelectrical processes for plasmonic solar cells with nanoparticles. Renewable Energy 2020, 165, 278 -287.

AMA Style

J.J. Zhang, Z.G. Qu, A. Maharjan. A three-dimensional numerical study of coupled photothermal and photoelectrical processes for plasmonic solar cells with nanoparticles. Renewable Energy. 2020; 165 ():278-287.

Chicago/Turabian Style

J.J. Zhang; Z.G. Qu; A. Maharjan. 2020. "A three-dimensional numerical study of coupled photothermal and photoelectrical processes for plasmonic solar cells with nanoparticles." Renewable Energy 165, no. : 278-287.