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A pouring silicate wick was manufactured to explore the influence of process and physical properties on the production and performance of loop heat pipes (LHP). This paper theoretically analyzed the advantages of pouring porous wick and introduced the technology of pouring silicate directly on evaporator. Based on this, the heat transfer performance of copper-methanol LHP system with pouring porous wick was tested under different positions. The results showed that with the input of multiple heat sources, the LHP could start up and maintain a stable temperature from 40 W to 160 W. When the vapor grooves were located above the compensation chamber, it was difficult to start up positively. By adding gravity assistance, the system could obtain more stable liquid supply and vapor flow, so as to realize start up. In the variable heat load test, the LHP showed good adaptability to the change of heat load. The thermal resistance of the system decreased with the increase of heat load. The thermal resistance of the evaporator almost unchanged and was always lower than 0.05 °C/W, which indicated that the pouring porous wick in the evaporator had good heat load matching.
Bing Cai; Weizhong Deng; Tong Wu; Tingting Wang; Zhengyuan Ma; Wei Liu; Lei Ma; Zhichun Liu. Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics. Processes 2021, 9, 1332 .
AMA StyleBing Cai, Weizhong Deng, Tong Wu, Tingting Wang, Zhengyuan Ma, Wei Liu, Lei Ma, Zhichun Liu. Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics. Processes. 2021; 9 (8):1332.
Chicago/Turabian StyleBing Cai; Weizhong Deng; Tong Wu; Tingting Wang; Zhengyuan Ma; Wei Liu; Lei Ma; Zhichun Liu. 2021. "Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics." Processes 9, no. 8: 1332.
Improving the heat transfer of cooler is favourable to reduce the cold end temperature and dead volume of Stirling engine. In this study, the effect of the implementation of a helical wire to a cooling tube of the reciprocating flow in Stirling engine was investigated numerically. The performance of helical wire with different geometric parameters and under different operating conditions were studied. The results show that the streamlines were helical and the fluid temperature homogeneity was improved. With the same size, the temperature drop of enhanced tube was 1.08–1.54 times as much as that of smooth tube. When obtaining the same outlet temperature, the diameter of smooth tube was 52% of that of enhanced tube with same tube length (for p = 12.5 mm, h = 1.2 mm, d0 = 1.6 mm, l = 180 mm, Remax = 13,816, Reω = 207). Thus, the amount of smooth tube needed to increase to 3.7 times as much as that of enhanced tube. In another case (for p = 12.5 mm, h = 1.2 mm, d0 = 1.6 mm, d = 5 mm, Remax = 13,816, Reω = 207), the length of smooth tube should be increased to above 2 times as much as that of enhanced tube with same tube diameter. Therefore, the tube with a helical wire could significantly enhance the heat transfer or decrease the size of cooler. Compared to smooth tube, the extra pressure drop by enhanced tube was accounts for no more than 0.6% of minimum pressure in Stirling engine (for Remax = 13,816, Reω = 207). It only accounted for 9.6–13.1% of the pressure drop of a regenerator. Therefore, the enhanced cooling tube with remarkable heat dissipation capacity and relatively low loss of pressure drop will present great application potential in Stirling engine.
Feng Xin; Minjie Yu; Wei Liu; Zhichun Liu. Heat transfer characteristics of enhanced cooling tube with a helical wire under oscillatory flow in Stirling engine. International Journal of Thermal Sciences 2021, 168, 107063 .
AMA StyleFeng Xin, Minjie Yu, Wei Liu, Zhichun Liu. Heat transfer characteristics of enhanced cooling tube with a helical wire under oscillatory flow in Stirling engine. International Journal of Thermal Sciences. 2021; 168 ():107063.
Chicago/Turabian StyleFeng Xin; Minjie Yu; Wei Liu; Zhichun Liu. 2021. "Heat transfer characteristics of enhanced cooling tube with a helical wire under oscillatory flow in Stirling engine." International Journal of Thermal Sciences 168, no. : 107063.
Thermo-osmotic energy conversion (TOEC) technology, developed from membrane distillation, is an emerging method that has the potential of obtaining electricity efficiently from a low-grade heat source but faces the difficult problem of pump power loss. In this study, we build a novel TOEC system with a multistage architecture that can work without pump assistance. The experiment system, made of cheap commercial materials, can obtain a power density of 1.39 ± 0.25 W/m2, with a heating temperature of 80 °C, and its efficiency increased linearly with the total stage number. A theory calculation shows that a 30-stage system with a specific membrane and a working pressure of 5.0 MPa can obtain an efficiency of 2.72% with a power density of 14.0 W/m2. By a molecular dynamics simulation, it is shown that a high-performance membrane has the potential to work at 40 MPa. This study proves that TOEC technology is a practical and competitive approach to covert low-grade thermal energy into power efficiently.
Ji Li; Zikang Zhang; Runze Zhao; Bo Zhang; Yunmin Liang; Rui Long; Wei Liu; Zhichun Liu. Stack Thermo-Osmotic System for Low-Grade Thermal Energy Conversion. ACS Applied Materials & Interfaces 2021, 13, 21371 -21378.
AMA StyleJi Li, Zikang Zhang, Runze Zhao, Bo Zhang, Yunmin Liang, Rui Long, Wei Liu, Zhichun Liu. Stack Thermo-Osmotic System for Low-Grade Thermal Energy Conversion. ACS Applied Materials & Interfaces. 2021; 13 (18):21371-21378.
Chicago/Turabian StyleJi Li; Zikang Zhang; Runze Zhao; Bo Zhang; Yunmin Liang; Rui Long; Wei Liu; Zhichun Liu. 2021. "Stack Thermo-Osmotic System for Low-Grade Thermal Energy Conversion." ACS Applied Materials & Interfaces 13, no. 18: 21371-21378.
For salinity gradient energy harvesting, membrane ion selectivity plays an important role, which is often qualitatively analysed via the electric double layer (EDL) overlapping degree in conventional studies. However, the degree of EDL overlapping is hard to be quantitatively evaluated. Here, we systematically analyze the synergy relations between physical vectors that determining the energy conversion process to quantitatively illustrate the EDL overlapping degree and ion selectivity. Three synergy angles are proposed to describe the synergy relations between the ion diffusion and the electrostatic migration driven forces. A synergy degree parameter is further defined, which could offer a quantitative way to analyze the cation transference number under different concentration ratios, channel length, and asymmetric channel geometries. In addition, an alternative way to use large size nanochannels to efficiently harvest the salinity gradient energy is developed by employing nanowire blockers. The inserted nanowire blocker can significantly enlarge the synergy degree parameter, thus to enhance the ion selectivity, upgrade the membrane potential, and bring a significant augment on the electric power and energy conversion efficiency. This study offers a novel insight into quantitatively analyzing the ion selectivity and paves an alternative way for efficiently salinity gradient energy harvesting via large size nanochannels.
Rui Long; Mingliang Li; Xi Chen; Zhichun Liu; Wei Liu. Synergy analysis for ion selectivity in nanofluidic salinity gradient energy harvesting. International Journal of Heat and Mass Transfer 2021, 171, 121126 .
AMA StyleRui Long, Mingliang Li, Xi Chen, Zhichun Liu, Wei Liu. Synergy analysis for ion selectivity in nanofluidic salinity gradient energy harvesting. International Journal of Heat and Mass Transfer. 2021; 171 ():121126.
Chicago/Turabian StyleRui Long; Mingliang Li; Xi Chen; Zhichun Liu; Wei Liu. 2021. "Synergy analysis for ion selectivity in nanofluidic salinity gradient energy harvesting." International Journal of Heat and Mass Transfer 171, no. : 121126.
Predicting the thermal conductivity of polymeric composites filled with BN sheets is helpful for fabricating thermal management material. In this study, a co-training style semi-supervised artificial neural network model (Co-ANN) was proposed to take advantage of unlabeled data to refine the prediction. The thermal conductivity of polymer matrix, the diameter, aspect ratio, and volume fraction of the BN sheets are considered as the input variables of the thermal conduction model. Two artificial neural network (ANN) learners with different architecture will label the unlabeled examples. Through estimating the labeling confidence from the mathematical influence and thermal conductive behavior, the most confidently labeled example will be used to augment the training dataset. The lower limit of the labeling confidence is introduced to reduce the data noise. After learning the augmented training information, a combination of two ANN regressors will construct the final Co-ANN thermal conduction model. Compared to other models, the newly developed Co-ANN thermal conduction model remarkably improves the thermal conductivity prediction and exhibits the best accuracy and generalization performance. The proposed method shows a vast potential in thermal conductive material design.
Yunmin Liang; Zhichun Liu; Wei Liu. A co-training style semi-supervised artificial neural network modeling and its application in thermal conductivity prediction of polymeric composites filled with BN sheets. Energy and AI 2021, 4, 100052 .
AMA StyleYunmin Liang, Zhichun Liu, Wei Liu. A co-training style semi-supervised artificial neural network modeling and its application in thermal conductivity prediction of polymeric composites filled with BN sheets. Energy and AI. 2021; 4 ():100052.
Chicago/Turabian StyleYunmin Liang; Zhichun Liu; Wei Liu. 2021. "A co-training style semi-supervised artificial neural network modeling and its application in thermal conductivity prediction of polymeric composites filled with BN sheets." Energy and AI 4, no. : 100052.
In this work, a novel parabolic trough receiver (NPTR) with an inner tube and wing-like fringe was proposed to improve heat-collecting efficiency as well as provide different grades of thermal energy. Thermal oil and water, which flow respectively in absorber and the inner tube, are selected as high and low temperature heat transfer fluids. A three-dimensional computational fluid dynamics model was developed to investigate the performance of the NPTR. Effects of geometrical parameter and thermal conductivity of inner tube on the performance of NPTR were studied in details. Based on the results, the NPTR with β = 180° is recommended as the suggested design. Moreover, performance of the suggested design under different direct normal irradiances (300–1000 W/m2) and inlet temperature of oil (400–650 K) were evaluated. Compared to the conventional parabolic trough receiver, the heat loss of NPTR is effectively reduced by 33.1–50.1%, and the overall efficiency can be improved by 0.61%–7.67%. Moreover, the proportions of oil and water heat gains in the total input solar energy are ranged in −18.8–63.5% and 8.39–77.6%, and the temperature gains of oil and water are ranged in −1.4–19.5 K and 5.4–18.8 K, respectively.
Peng Liu; Zhimin Dong; Hui Xiao; Zhichun Liu; Wei Liu. A novel parabolic trough receiver by inserting an inner tube with a wing-like fringe for solar cascade heat collection. Renewable Energy 2021, 170, 327 -340.
AMA StylePeng Liu, Zhimin Dong, Hui Xiao, Zhichun Liu, Wei Liu. A novel parabolic trough receiver by inserting an inner tube with a wing-like fringe for solar cascade heat collection. Renewable Energy. 2021; 170 ():327-340.
Chicago/Turabian StylePeng Liu; Zhimin Dong; Hui Xiao; Zhichun Liu; Wei Liu. 2021. "A novel parabolic trough receiver by inserting an inner tube with a wing-like fringe for solar cascade heat collection." Renewable Energy 170, no. : 327-340.
Based on the excellent performance of porous media and the popularity of additive manufacturing technology, gradient porous media with unique properties are gradually applied in the increasing fields. In this paper, the flow and heat transfer characteristics for fully developed flow in a tube partially filled with gradient porous media are investigated by numerical simulation, where the pore-size (dp) and porosity (ε) vary linearly along the radius. Keeping average pore-size dpa = 0.007 m and average porosity εa = 0.875, the comparison of four configurations, classified by the pore-size and porosity distributions in the radial direction, is performed to investigate the difference in flow and heat transfer performance. Subsequently, the parametric analysis under the different filling ratios is conducted to learn the combined effect of the gradients of porosity and pore-size. The results show that the configurations with pore-size decreasing in radial direction have a better heat transfer performance where the effect of porosity arrangement on the flow and heat transfer can be neglected. As the filling ratio increasing, the performance is more sensitive to the variation of the gradients. Furthermore, a multi-objective genetic optimization coupled Kriging surrogate model is conducted with the consideration of maximum Nusselt number Nu and minimum friction factor f as objectives. The distribution of design variables corresponding to the optimal configurations is obtained by weighing two optimization objectives. The optimal results show that the flow resistance can be reduced by up to 19.573%, and the heat transfer efficiency can be increased by up to 7.088% compared with the homogeneous porous media under the filling ratio rd = 0.7.
Chunyu Shi; Miaozhi Wang; Jun Yang; Wei Liu; Zhichun Liu. Performance analysis and multi-objective optimization for tubes partially filled with gradient porous media. Applied Thermal Engineering 2021, 188, 116530 .
AMA StyleChunyu Shi, Miaozhi Wang, Jun Yang, Wei Liu, Zhichun Liu. Performance analysis and multi-objective optimization for tubes partially filled with gradient porous media. Applied Thermal Engineering. 2021; 188 ():116530.
Chicago/Turabian StyleChunyu Shi; Miaozhi Wang; Jun Yang; Wei Liu; Zhichun Liu. 2021. "Performance analysis and multi-objective optimization for tubes partially filled with gradient porous media." Applied Thermal Engineering 188, no. : 116530.
Previous studies on the electrokinetic energy conversion (EKEC) are limited to the isothermal condition at the environmental temperature. Here effects of temperature and membrane thermal conductivity are systematically investigated. Under isothermal conditions, elevated temperature can improve the electric power while the energy efficiency stays unchanged. Under non-isothermal conditions, at small membrane thermal conductivities, a negative temperature difference contributes to the electric power for dramatically enhanced streaming current as enhanced ion mobility along the streaming direction induces an internal ion concentration polarization (IICP) that generates a co-flow concentration gradient in the nanopore interior. At large membrane thermal conductivities, the positive temperature difference reverses the external ion concentration polarization (EICP) in the solution reservoirs due to the Soret effect, resulting in more obvious electric power improvement. Furthermore, a criterion to enhance the EKEC performance via employing asymmetric temperatures is proposed, and an alternative way to construct the tunable ionic current source is presented. Present study provides guidance for enhancing the EKEC performance by employing waste heat, and fabricating nanofluidic functional devices.
Rui Long; Fan Wu; Xiyu Chen; Zhichun Liu; Wei Liu. Temperature-depended ion concentration polarization in electrokinetic energy conversion. International Journal of Heat and Mass Transfer 2021, 168, 120842 .
AMA StyleRui Long, Fan Wu, Xiyu Chen, Zhichun Liu, Wei Liu. Temperature-depended ion concentration polarization in electrokinetic energy conversion. International Journal of Heat and Mass Transfer. 2021; 168 ():120842.
Chicago/Turabian StyleRui Long; Fan Wu; Xiyu Chen; Zhichun Liu; Wei Liu. 2021. "Temperature-depended ion concentration polarization in electrokinetic energy conversion." International Journal of Heat and Mass Transfer 168, no. : 120842.
In this work, two submerged jet impingement/microchannel heat sink (JIMHS) models were proposed, i.e., straight-rib jet impingement/microchannel heat sink (SJIMHS) and oblique-rib jet impingement/microchannel heat sink (OJIMHS). The heat transfer and flow characteristics of the two models were investigated by overall numerical simulation and experiment. In the numerical simulation, the effects of heat flux, pressure drop and rib arrangement on the internal flow and heat transfer of the heat sink were studied. The results indicate that under the same heat flux and inlet condition, the heat transfer surface of OJIMHS achieves more uniform and lower temperature distribution compared with that of SJIMHS, and the average convective heat transfer coefficient of the OJIMHS is obviously higher than that of SJIMHS in all calculation cases, with an increase of about 20%. In addition, the performance of OJIMHS was tested experimentally. The comparison indicates that the maximum relative errors of average temperature and heat transfer coefficient between simulation and experiment were less than 9%. When the volume flow rate is 0.5 L/min and the heat flux is 100 W/cm², the average temperature of the heat transfer surface is still lower than 60°C. Besides, the averaged heat transfer coefficient of 2.8W/(cm2·K) was achieved under the inlet fluid temperature of 283K and volume flow rate of 2.5 L/min in the experiment.
H.C. Cui; X.T. Lai; J.F. Wu; M.Z. Wang; W. Liu; Z.C. Liu. Overall numerical simulation and experimental study of a hybrid oblique-rib and submerged jet impingement/microchannel heat sink. International Journal of Heat and Mass Transfer 2020, 167, 120839 .
AMA StyleH.C. Cui, X.T. Lai, J.F. Wu, M.Z. Wang, W. Liu, Z.C. Liu. Overall numerical simulation and experimental study of a hybrid oblique-rib and submerged jet impingement/microchannel heat sink. International Journal of Heat and Mass Transfer. 2020; 167 ():120839.
Chicago/Turabian StyleH.C. Cui; X.T. Lai; J.F. Wu; M.Z. Wang; W. Liu; Z.C. Liu. 2020. "Overall numerical simulation and experimental study of a hybrid oblique-rib and submerged jet impingement/microchannel heat sink." International Journal of Heat and Mass Transfer 167, no. : 120839.
Adsorption-driven osmotic heat engines offer an alternative way for harvesting low-grade waste heat below 80°C. In this study, we performed a high-throughput computational screening based on grand canonical Monte Carlo simulations to identify the high-performance metal-organic frameworks (MOFs) from 1322 computationally ready experimental MOF structures for adsorption-driven osmotic heat engines with LiCl-methanol as the working fluid. Structure-property relationship analysis reveals that MOFs exhibiting high energy efficiency possess large working capacity, pore size and surface area, and moderate adsorption enthalpy comparable to the evaporation enthalpy. Furthermore, machine learning is employed to accelerate the computational screening for satisfied MOFs via the structure properties. The optimal structure properties of the MOFs are further identified via the ensemble-based regression model by optimizing the energy efficiency via the genetic algorithm, which shed light on rationally designing and fabricating MOFs for desired heat-to-electricity conversion.
Rui Long; Xiaoxiao Xia; Yanan Zhao; Song Li; Zhichun Liu; Wei Liu. Screening metal-organic frameworks for adsorption-driven osmotic heat engines via grand canonical Monte Carlo simulations and machine learning. iScience 2020, 24, 101914 .
AMA StyleRui Long, Xiaoxiao Xia, Yanan Zhao, Song Li, Zhichun Liu, Wei Liu. Screening metal-organic frameworks for adsorption-driven osmotic heat engines via grand canonical Monte Carlo simulations and machine learning. iScience. 2020; 24 (1):101914.
Chicago/Turabian StyleRui Long; Xiaoxiao Xia; Yanan Zhao; Song Li; Zhichun Liu; Wei Liu. 2020. "Screening metal-organic frameworks for adsorption-driven osmotic heat engines via grand canonical Monte Carlo simulations and machine learning." iScience 24, no. 1: 101914.
Solar energy is clean and sustainable to power our continuously developing society, but the intermittency and unpredictability lays a barrier on its direct connection to the grid. Seawater desalination is an effective path to consume dynamic solar energy to produce fresh water and stable salinity gradient energy simultaneously. Thus, a self-diluted 2-stage reverse osmosis with high recovery ratio is proposed to consume the renewable power from a dish solar Stirling engine to achieve more water production and energy storage. Based on theoretical derivation, system performance is evaluated under ideal membrane property and enough membrane area condition. The influence of hydraulic pressure difference and diluted fraction ratio on water production and energy storage performance are investigated. A performance optimization is further conducted and the corresponding performance are evaluated. Results revealed that self-diluted 2-stage configuration can improve the maximal recovery ratio from 25%, 57% and 70% to 39%, 62% and 72% under the maximal bearable pressure difference of 4, 7 and 10 MPa. Maximal salinity gradient energy of 3.84 MJ can be stored with an overall energy efficiency of 8.42% while desalinating 1 cubic meter seawater of 0.6 M. Theoretical analysis indicates that novel configuration is potentially an effective method to improve the upper separation limitation, which further produces more water and stores more solar energy in the desalination process of finite amount of source seawater.
Xiaotian Lai; Rui Long; Zhichun Liu; Wei Liu. Solar energy powered high-recovery reverse osmosis for synchronous seawater desalination and energy storage. Energy Conversion and Management 2020, 228, 113665 .
AMA StyleXiaotian Lai, Rui Long, Zhichun Liu, Wei Liu. Solar energy powered high-recovery reverse osmosis for synchronous seawater desalination and energy storage. Energy Conversion and Management. 2020; 228 ():113665.
Chicago/Turabian StyleXiaotian Lai; Rui Long; Zhichun Liu; Wei Liu. 2020. "Solar energy powered high-recovery reverse osmosis for synchronous seawater desalination and energy storage." Energy Conversion and Management 228, no. : 113665.
The operation stability demands for low and uniform wall temperature in the parabolic trough collector which acts as an energy conversion component in concentrating thermal conversion technology. In order to reduce the local high temperature with moderate pump power consumption, this paper proposed longitudinal swirls impinging cooling method. Three types of novel inclined curved-twisted baffles (A1, A2, and A3) were devised to realize this method. With selecting the absorber tube as research model, this paper numerically compared the impinging cooling characteristics, wall temperature uniformity performance, and efficiency performance by inserting the three types of baffles. The A1 and A2 types each generated a pair of longitudinal swirls while the A3 type generated two pairs of longitudinal swirls. The impinging cooling always appeared near the front edge of inclined baffles. The A1 type was the best in wall temperature uniformity and efficiencies among three baffles. Furthermore, as the inlet temperature increased from 400 K to 600 K at a mass flow rate of 1.13 kg/s in the A1 type tube, the average wall temperature difference between bottom half tube and top half tube was decreased by 55.1%. Meanwhile, the average overall efficiency and exergy efficiency were increased by 0.52% and 0.22%, respectively.
Hui Xiao; Peng Liu; Zhichun Liu; Wei Liu. Performance analyses in parabolic trough collectors by inserting novel inclined curved-twisted baffles. Renewable Energy 2020, 165, 14 -27.
AMA StyleHui Xiao, Peng Liu, Zhichun Liu, Wei Liu. Performance analyses in parabolic trough collectors by inserting novel inclined curved-twisted baffles. Renewable Energy. 2020; 165 ():14-27.
Chicago/Turabian StyleHui Xiao; Peng Liu; Zhichun Liu; Wei Liu. 2020. "Performance analyses in parabolic trough collectors by inserting novel inclined curved-twisted baffles." Renewable Energy 165, no. : 14-27.
Electron–phonon interaction (EPI) plays an important role in the transport property of metals. Nevertheless, EPI in polymer nanocomposites containing metal fillers has not been fully investigated due to the complicated physical mechanisms. In this work, the copper–polyethylene (Cu–PE) nanocomposite is used as a model system, and nonequilibrium molecular dynamics (NEMD) simulation combined with the two-temperature model (TTM) is conducted to reveal the role of EPI in Cu–PE systems. The effects of filler length, filler property, and EPI strength on thermal conductivity are revealed. A dimensionless number (Θ) is defined to characterize the electron–phonon nonequilibrium (EPN) degree. The results show that the EPN degree has a significant impact on thermal conductivity. When the system is in a strong EPN state, the effects of EPI on thermal conductivity can be negligible. However, when the EPN degree gradually decreases, ignoring EPI can severely underestimate the thermal conductivity. Furthermore, the temperature profile of electrons and phonons is extracted and the equivalent thermal circuit is presented. The additional thermal resistances induced by the nonlocal and nonequilibrium effects are revealed. Phonon spectra analysis and heat current decomposition are performed to uncover the underlying mechanisms. In addition, the effects of atomic mass density and filler types on thermal conductivity are revealed. Stress–strain simulation is conducted to unravel the effects of strain rates on the mechanical property. The results are useful for designing polymer nanocomposites with controlled thermal conductivity.
Bo Zhang; Yunmin Liang; Wei Liu; Zhichun Liu. Effects of the Filler Property, Electron–Phonon Coupling on Thermal Conductivity, and Strain Rate on the Mechanical Property of Polyethylene Nanocomposites. The Journal of Physical Chemistry C 2020, 124, 26001 -26011.
AMA StyleBo Zhang, Yunmin Liang, Wei Liu, Zhichun Liu. Effects of the Filler Property, Electron–Phonon Coupling on Thermal Conductivity, and Strain Rate on the Mechanical Property of Polyethylene Nanocomposites. The Journal of Physical Chemistry C. 2020; 124 (47):26001-26011.
Chicago/Turabian StyleBo Zhang; Yunmin Liang; Wei Liu; Zhichun Liu. 2020. "Effects of the Filler Property, Electron–Phonon Coupling on Thermal Conductivity, and Strain Rate on the Mechanical Property of Polyethylene Nanocomposites." The Journal of Physical Chemistry C 124, no. 47: 26001-26011.
Heat pumps are widely used in domesticity, agriculture, and industry. Here, we report a novel heat pump based on reverse thermo-osmosis (RTO) effect in a nanoporous graphene (NPG) membrane. Through classical molecular dynamics (MD) simulation, we prove that the heat pump can transport mass and heat efficiently. The heat and mass fluxes are increased linearly with the hydraulic pressure provided. Ultra-high heat fluxes of 6.2±1.0 kW/cm2 and coefficient of performance (COP) of 20.2 are obtained with a temperature increment of 5 K and a working pressure of 80 MPa. It is interesting that water molecules on the NPG membrane can evaporate in a cluster state and the cluster evaporations reduce the vaporization enthalpy of the processes.
Ji Li; Rui Long; Bo Zhang; Ronggui Yang; Wei Liu; Zhichun Liu. Nano Heat Pump Based on Reverse Thermo-osmosis Effect. The Journal of Physical Chemistry Letters 2020, 11, 9856 -9861.
AMA StyleJi Li, Rui Long, Bo Zhang, Ronggui Yang, Wei Liu, Zhichun Liu. Nano Heat Pump Based on Reverse Thermo-osmosis Effect. The Journal of Physical Chemistry Letters. 2020; 11 (22):9856-9861.
Chicago/Turabian StyleJi Li; Rui Long; Bo Zhang; Ronggui Yang; Wei Liu; Zhichun Liu. 2020. "Nano Heat Pump Based on Reverse Thermo-osmosis Effect." The Journal of Physical Chemistry Letters 11, no. 22: 9856-9861.
In this study, an electricity and cooling power cogeneration system is investigated to harvest low-grade heat below 80 ℃, which consists of a two-bed adsorption-based desalination (AD) system for thermally separating the salt solution into diluted and concentrated solutions while offering cooling power and a reverse electrodialysis (RED) system for converting the Gibbs free energy of mixing of the generated solutions into electricity. The dynamic response of the cogeneration system is presented first, and the asymmetric operation period is analyzed. Then the effects of adsorption/desorption time, switching time, working concentration, working fluid mass, and adsorbents on the electric efficiency, coefficient of performance (COP) and exergy efficiency of the cogeneration system are systematically evaluated. Results reveal that longer adsorption/desorption time leads to degraded electrical efficiency and exergy efficiency, and upgraded COP. Extended switching time contributes to COP and exergy efficiency, however, decreases the electric efficiency. Larger salt concentration improves the electric efficiency, however degrades the exergy efficiency and COP. Increasing working solution mass can augment the electrical efficiency, exergy efficiency and COP. Furthermore, refrigeration performance conflicts with power generation performance for different adsorbents. With CAU-10 as the adsorbent, an exergy efficiency of 30.04% is achieved, meanwhile the electric efficiency and COP is 0.39% and 0.84, respectively at adsorption/desorption time of 900 s, switching time of 10 s and working concentration of 8 mol/kg.
Yanan Zhao; Mingliang Li; Rui Long; Zhichun Liu; Wei Liu. Dynamic modelling and analysis of an adsorption-based power and cooling cogeneration system. Energy Conversion and Management 2020, 222, 113229 .
AMA StyleYanan Zhao, Mingliang Li, Rui Long, Zhichun Liu, Wei Liu. Dynamic modelling and analysis of an adsorption-based power and cooling cogeneration system. Energy Conversion and Management. 2020; 222 ():113229.
Chicago/Turabian StyleYanan Zhao; Mingliang Li; Rui Long; Zhichun Liu; Wei Liu. 2020. "Dynamic modelling and analysis of an adsorption-based power and cooling cogeneration system." Energy Conversion and Management 222, no. : 113229.
Improving thermo-mechanical characteristics of polymers can efficiently promote their applications in heat exchangers and thermal management. However, a feasible way to enhance the thermo-mechanical property of bulk polymers at low filler content still remains to be explored. Here, we propose mixing high length-diameter ratio filler such as carbon nanotube (CNT), boron nitride (BN) nanotube, and copper (Cu) nanowire, in the woven polymer matrix to meet the purpose. Through molecular dynamics (MD) simulation, the thermal properties of three woven polymers including woven polyethylene (PE), woven poly (p-phenylene) (PPP), and woven polyacetylene (PA) are investigated. Besides, using woven PE as a polymer matrix, three polymer nanocomposites, namely PE-CNT, PE-BN, and PE-Cu, are constructed by mixing CNT, BN nanotube, and Cu nanowire respectively, whose thermo-mechanical characteristics are compared via MD simulation. Morphology and phonons spectra analysis are conducted to reveal the underlying mechanisms. Furthermore, impacts of electron-phonon coupling and electrical field on the thermal conductivity of PE-Cu are uncovered via two temperature model MD simulation. Classical theoretical models are modified to predict the effects of filler and matrix on the thermal conductivity of polymer nanocomposites. This work can provide useful guidelines for designing thermally conductive bulk polymers and polymer nanocomposites.
Bo Zhang; Yunmin Liang; Biwei Liu; Wei Liu; Zhichun Liu. Enhancing the Thermo-Mechanical Property of Polymer by Weaving and Mixing High Length–Diameter Ratio Filler. Polymers 2020, 12, 1255 .
AMA StyleBo Zhang, Yunmin Liang, Biwei Liu, Wei Liu, Zhichun Liu. Enhancing the Thermo-Mechanical Property of Polymer by Weaving and Mixing High Length–Diameter Ratio Filler. Polymers. 2020; 12 (6):1255.
Chicago/Turabian StyleBo Zhang; Yunmin Liang; Biwei Liu; Wei Liu; Zhichun Liu. 2020. "Enhancing the Thermo-Mechanical Property of Polymer by Weaving and Mixing High Length–Diameter Ratio Filler." Polymers 12, no. 6: 1255.
Low grade heat below 80 °C could offer a considerable energy supply. The utilization for this energy is limited with existing heat-to-power technologies for rather small differences between the heat source and environment. To efficiently harvest such low-grade heat, an alternative kind of thermal regenerative osmotic heat engine (TROHE) is proposed, which employs power-driven separation processes that run at a lower temperature, and the salinity gradient power technologies for power extraction after heating. For a TROHE that employs the reverse osmosis in the solution separation process, and pressure retarded osmosis in the energy extraction process, a figure of merit for selecting appropriate solutions is proposed. Salt solutions with a smaller specific heat capacity and density, and higher solubility are preferred to achieve a larger heat-to-work conversion efficiency. When operating between 60 °C and 20 °C, a maximum energy efficiency of 1.4% was achieved at 7 M LiCl-Methanol solution with a regenerative efficiency 90%. With advances in high performance regenerators and membrane technologies, the proposed TROHE can offer an alternative way for efficiently utilizing the vast low-grade heat.
Rui Long; Yanan Zhao; Zuoqing Luo; Lei Li; Zhichun Liu; Wei Liu. Alternative thermal regenerative osmotic heat engines for low-grade heat harvesting. Energy 2020, 195, 117042 .
AMA StyleRui Long, Yanan Zhao, Zuoqing Luo, Lei Li, Zhichun Liu, Wei Liu. Alternative thermal regenerative osmotic heat engines for low-grade heat harvesting. Energy. 2020; 195 ():117042.
Chicago/Turabian StyleRui Long; Yanan Zhao; Zuoqing Luo; Lei Li; Zhichun Liu; Wei Liu. 2020. "Alternative thermal regenerative osmotic heat engines for low-grade heat harvesting." Energy 195, no. : 117042.
A loop heat pipe (LHP) is one of the most efficient two-phase heat transfer devices. During its operation, a portion of the heat load applied to the evaporator is transferred to its compensation chamber (CC) through the evaporator sidewall, which is known as a heat leak, decreasing the performance of the LHP startup to a certain degree. To reduce a heat leak through the evaporator sidewall, an LHP with a composite-material evaporator was proposed. The evaporator is composed of two types of material, namely, red copper (heating surface) and 316L stainless steel (upper part), and has a reinforced rib structure on the heating surface to improve the evaporator strength. Two sintered nickel wicks are incorporated inside the evaporator. The experimental results demonstrate that the LHP with a composite-material evaporator can operate successfully within a heat load range of 10–140 W while heating the surface to below 80 °C at a heat sink temperature of 25 °C and 35 °C. Compared with an LHP with the same evaporator structure (but with a different in material) [17], the temperature difference between the evaporator outlet and the CC left (right) is smaller under the same heat load, indicating that the heat leak through the evaporator sidewall is reduced.
Song He; Ping Zhou; Wei Liu; Zhichun Liu. Experimental study on thermal performance of loop heat pipe with a composite-material evaporator for cooling of electronics. Applied Thermal Engineering 2020, 168, 114897 .
AMA StyleSong He, Ping Zhou, Wei Liu, Zhichun Liu. Experimental study on thermal performance of loop heat pipe with a composite-material evaporator for cooling of electronics. Applied Thermal Engineering. 2020; 168 ():114897.
Chicago/Turabian StyleSong He; Ping Zhou; Wei Liu; Zhichun Liu. 2020. "Experimental study on thermal performance of loop heat pipe with a composite-material evaporator for cooling of electronics." Applied Thermal Engineering 168, no. : 114897.
Originating from advances in nanofabrication, functional materials have been developed to construct bioinspired or mimic nanochannels for efficient nanofluidic energy conversion. In previous studies regarding nanofluidic energy conversion, the material thermal conductivity has been never taken into consideration, however, which shall be addressed with transmembrane temperature difference applied. Thermal conductivities of widely used bulk materials for fabricating nanopores vary from 0 to 120 W/(m·K). Heat transfer occurs both in the liquid solution and solid membrane, impacting trans-channel solution temperature distribution and ion transportation, and yielding counterintuitive phenomena. Under positive temperature differences, the electric power shifts from inhibition to promotion as the membrane thermal conductivity increases. Larger membrane thermal conductivity evens temperature distribution in the nanochannel, weakening ion aggregations or depletions, which result in degraded electric power improvement under a negative temperature difference and upgraded power enhancement under a positive one. At a temperature difference of 30 K, the electric power is enhanced by 56.22% for a thin PET membrane (length = 50 nm) under the negative temperature difference. If the membrane thermal conductivity can be well tuned to nearly thermal insulation, the electric power can be enhanced by 120.07%. To step further, we proposed a criterion for membrane selection based on thermal conductivities in the thermally nanofluidic energy conversion: For thick membranes, materials of large thermal conductivity with a positive temperature difference are preferred for obvious power and energy efficiency enhancement. For thin membranes, materials of small thermal conductivity with a negative temperature difference are appealing. These findings reveal the importance of a long-overlooked factor, membrane thermal conductivity, in nanofluidic energy harvesting and can serve as a guidance for selecting appropriate membrane materials and developing high-performance nanofluidic power devices.
Rui Long; Zuoqing Luo; Zhengfei Kuang; Zhichun Liu; Wei Liu. Effects of heat transfer and the membrane thermal conductivity on the thermally nanofluidic salinity gradient energy conversion. Nano Energy 2020, 67, 104284 .
AMA StyleRui Long, Zuoqing Luo, Zhengfei Kuang, Zhichun Liu, Wei Liu. Effects of heat transfer and the membrane thermal conductivity on the thermally nanofluidic salinity gradient energy conversion. Nano Energy. 2020; 67 ():104284.
Chicago/Turabian StyleRui Long; Zuoqing Luo; Zhengfei Kuang; Zhichun Liu; Wei Liu. 2020. "Effects of heat transfer and the membrane thermal conductivity on the thermally nanofluidic salinity gradient energy conversion." Nano Energy 67, no. : 104284.
Channel shape design has a significant effect on the performance of a proton exchange membrane fuel cell. Inspired by the fins of cuttlefish, a bio-inspired wave-like structure is designed and applied to the channel of fuel cells. The impact of this bio-inspired wave-like channel on fuel cell performance is investigated through a three-dimensional and non-isothermal model developed in COMSOL Multiphysics. The effects of channel center amplitude and number of wave cycles on the current density and pressure drop of fuel cells are studied. Compared with fuel cells with basic straight channel and conventional wave-like channel, the results show that fuel cell with this bio-inspired wave-like channel has high efficiency and low flow resistance, which can obtain better comprehensive performance. In addition, an optimization of the waveform for bio-inspired wave-like channel is performed by genetic algorithm in consideration of the output power and power consumption of flow. The optimal channel with a center amplitude of 0.305 mm and the number of wave cycles of 3.52 improves the output power density by 2.2%.
Genchun Cai; Yunmin Liang; Zhichun Liu; Wei Liu. Design and optimization of bio-inspired wave-like channel for a PEM fuel cell applying genetic algorithm. Energy 2019, 192, 116670 .
AMA StyleGenchun Cai, Yunmin Liang, Zhichun Liu, Wei Liu. Design and optimization of bio-inspired wave-like channel for a PEM fuel cell applying genetic algorithm. Energy. 2019; 192 ():116670.
Chicago/Turabian StyleGenchun Cai; Yunmin Liang; Zhichun Liu; Wei Liu. 2019. "Design and optimization of bio-inspired wave-like channel for a PEM fuel cell applying genetic algorithm." Energy 192, no. : 116670.