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Wei Liu
School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

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Journal article
Published: 30 July 2021 in Processes
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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.

ACS Style

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 Style

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 (8):1332.

Chicago/Turabian Style

Bing 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.

Journal article
Published: 26 July 2021 in Applied Thermal Engineering
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Flat evaporator loop heat pipes with good thermal performance and compact volume have been widely used in electronic device applications. A flat-disk evaporator loop heat pipe made of aluminum alloy was designed for terrestrial application in this paper. R1233zd(E) was selected as the working fluid for its ultra-low toxicity and environmentally friendly. The pumping force of the system, driving the working fluid circulation, was generated by the sintered capillary wick made from nickel powder. Considering the requirements for electronics and the capillary limit of the wick together, the target temperature was below 75 °C and the effective heat transfer length was set as 790 mm. With a heat sink temperature of -10 °C, it could dissipate the heat of 190 W (11.43 W/cm2). The performance investigation under bad external conditions was also carried out. A relatively broad operating range between the heat load of 10 W (0.60 W/cm2) and 130 W (7.82 W/cm2) was observed with a 30 °C heat sink temperature. However, slight temperature overshoot occurred during the start-up test but the system was able to self-regulate and stabilize quickly. Moreover, the variable heat load test, imitating the heat-dissipating demand for actual electronic devices, demonstrated that this system responded fast and operation failure did not happen. The minimum thermal resistance of the evaporator and the total LHP was 0.134 °C/W and 0.197 °C/W, respectively.

ACS Style

Runze Zhao; Zikang Zhang; Shuaicheng Zhao; Haichuan Cui; Zhichun Liu; Wei Liu. Experimental study of flat-disk loop heat pipe with R1233zd(E) for cooling terrestrial electronics. Applied Thermal Engineering 2021, 197, 117385 .

AMA Style

Runze Zhao, Zikang Zhang, Shuaicheng Zhao, Haichuan Cui, Zhichun Liu, Wei Liu. Experimental study of flat-disk loop heat pipe with R1233zd(E) for cooling terrestrial electronics. Applied Thermal Engineering. 2021; 197 ():117385.

Chicago/Turabian Style

Runze Zhao; Zikang Zhang; Shuaicheng Zhao; Haichuan Cui; Zhichun Liu; Wei Liu. 2021. "Experimental study of flat-disk loop heat pipe with R1233zd(E) for cooling terrestrial electronics." Applied Thermal Engineering 197, no. : 117385.

Journal article
Published: 22 May 2021 in International Journal of Thermal Sciences
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

Feng 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.

Journal article
Published: 01 May 2021 in SCIENTIA SINICA Technologica
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对流传热具有守恒、协同和耗散三大特性,揭示其内在联系与基本规律对发展对流传热强化理论意义重大。本文基于能量和动量传输的本构和守恒关系,全面审视对流传热的多场协同与不可逆耗散机制,分析流体传热、耗功及惯性协同角之间的相互关系,提出反映对流传热不可逆耗散的热效率和㶲效率,探索基于增强协同与减少耗散的对流传热强化理论。基于此,提出一种V型复合肋槽强化传热管并进行湍流换热计算模拟。研究发现:与光滑圆管相比,在管壁形成V型复合肋槽可减小强化管的传热和惯性平均协同角,热效率和㶲效率分别超过92%和34%,性能和效能评价系数分别为1.22~1.69和0.53~1.07。

ACS Style

Wei Liu; Hui Xiao. 基于增强协同与减少耗散的对流传热强化理论研究. SCIENTIA SINICA Technologica 2021, 1 .

AMA Style

Wei Liu, Hui Xiao. 基于增强协同与减少耗散的对流传热强化理论研究. SCIENTIA SINICA Technologica. 2021; ():1.

Chicago/Turabian Style

Wei Liu; Hui Xiao. 2021. "基于增强协同与减少耗散的对流传热强化理论研究." SCIENTIA SINICA Technologica , no. : 1.

Journal article
Published: 13 March 2021 in Renewable Energy
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Flat-Plate solar air heater (SAH) is utilized widely to relieve the fossil energy crisis nowadays. With the aim to improve the efficiency of the devices, heat transfer and flow characteristic in a solar air heater with novel inclined groove ripple surfaces were investigated in this work. The effect of three different parameters, such as groove amplitude, attack angle, and array number, on the overall performance of air heater was analyzed in the range of Reynolds number from 12000 to 24000. The inclined grooves on the ripple surface have a significant impact on the working fluid for generating longitudinal swirl flow in the duct of air heater, which mixes the air to enhance heat transfer, Nu/Nu0 = 1.21–3.38, and leads to a moderate increase of pressure drop in the same time, f/f0 = 1.54–6.96. The solar air heater composed with ripple surface is of excellent overall thermo-hydraulic performance, Nusselt numbers are 1.04–1.94 times higher than the smooth duct at same blowing energy consumption.

ACS Style

Zhimin Dong; Peng Liu; Hui Xiao; Zhichun Liu; Wei Liu. A study on heat transfer enhancement for solar air heaters with ripple surface. Renewable Energy 2021, 172, 477 -487.

AMA Style

Zhimin Dong, Peng Liu, Hui Xiao, Zhichun Liu, Wei Liu. A study on heat transfer enhancement for solar air heaters with ripple surface. Renewable Energy. 2021; 172 ():477-487.

Chicago/Turabian Style

Zhimin Dong; Peng Liu; Hui Xiao; Zhichun Liu; Wei Liu. 2021. "A study on heat transfer enhancement for solar air heaters with ripple surface." Renewable Energy 172, no. : 477-487.

Journal article
Published: 09 March 2021 in Energies
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Pressure is a physical quantity that is indispensable in the study of transport phenomena. Previous studies put forward a pressure constitutive law and constructed a partial differential equation on pressure to study the convection with or without heat and mass transfer. In this paper, a numerical algorithm was proposed to solve this pressure equation by coupling with the Navier-Stokes equation. To match the pressure equation, a method of dealing with pressure boundary condition was presented by combining the tangential and normal direction pressure relations, which should be updated dynamically in the iteration process. Then, a solution to this pressure equation was obtained to bridge the gap between the mathematical model and a practical numerical algorithm. Through numerical verification in a circular tube, it is found that the proposed boundary conditions are applicable. The results demonstrate that the present pressure equation well describes the transport characteristics of the fluid.

ACS Style

Hui Xiao; Wei Liu. A Solution to Pressure Equation with Its Boundary Condition of Combining Tangential and Normal Pressure Relations. Energies 2021, 14, 1507 .

AMA Style

Hui Xiao, Wei Liu. A Solution to Pressure Equation with Its Boundary Condition of Combining Tangential and Normal Pressure Relations. Energies. 2021; 14 (5):1507.

Chicago/Turabian Style

Hui Xiao; Wei Liu. 2021. "A Solution to Pressure Equation with Its Boundary Condition of Combining Tangential and Normal Pressure Relations." Energies 14, no. 5: 1507.

Journal article
Published: 02 February 2021 in Renewable Energy
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

Peng 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.

Journal article
Published: 29 December 2020 in International Journal of Heat and Mass Transfer
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

H.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.

Journal article
Published: 11 December 2020 in Energy
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The utilization of solar energy is of great significance to alleviate energy shortage and environmental problems. In view of the different thermal grade requirements of electricity production and water desalination in remote arid areas as well as to improve the performance of the parabolic trough receiver (PTR), a novel solar cascade heat collection system based on a PTR with double tube and two heat transfer fluids (HTF) is proposed in this paper. A three-dimensional model is developed to simulate and investigate the temperature distribution, heat transfer and flow characteristics and heat collecting performance of the novel system. Moreover, the effects of the operating parameters on the performance are studied in details. The temperatures of the absorber tube are significantly reduced over the plain PTR, and the heat transfer coefficient on the absorber inner surface is enhanced about 50% with 2.5–6.8 times increment in total pumping work. In addition, the heat loss reduced up to 43.1%, thus, the maximum improvement of the total thermal efficiency reaches up to 1.5%. Within the parameters considered in this study, the proportions of the high and low temperature heat gains are ranged in 39.01–62.92% and 28.37–8.86% of the incident solar energy, respectively.

ACS Style

Peng Liu; Zhimin Dong; Hui Xiao; Zhichun Liu; Wei Liu. Thermal-hydraulic performance analysis of a novel parabolic trough receiver with double tube for solar cascade heat collection. Energy 2020, 219, 119566 .

AMA Style

Peng Liu, Zhimin Dong, Hui Xiao, Zhichun Liu, Wei Liu. Thermal-hydraulic performance analysis of a novel parabolic trough receiver with double tube for solar cascade heat collection. Energy. 2020; 219 ():119566.

Chicago/Turabian Style

Peng Liu; Zhimin Dong; Hui Xiao; Zhichun Liu; Wei Liu. 2020. "Thermal-hydraulic performance analysis of a novel parabolic trough receiver with double tube for solar cascade heat collection." Energy 219, no. : 119566.

Journal article
Published: 03 December 2020 in Applied Thermal Engineering
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High flow resistance in conventional porous regenerators has been an important factor for limiting the overall performance of Stirling engines. Herein, a novel constructal bifurcation regenerator based on constructal concept was developed to reduce the flow resistance in the Stirling regenerator. First, the pressure drop and transient conjugate heat transfer characteristics of oscillating flows through the constructal bifurcation regenerator with various geometrical parameters were investigated by the CFD approach. The results showed that the fluid flow and heat transfer between the acceleration and deceleration phases, as well as the discharge and suction phases, were varied significantly. These differences should be resulted from the local acceleration effect, the formation of eddies in the acceleration phase, and different windward surfaces generated by the regenerator matrix to the fluid in the discharge and suction phases. Additionally, the flow characteristics between the oscillating and steady flows were compared and the local acceleration effect was proven to be the main cause of the difference between them. Then the three-parameters correlation equations of friction factor and Nusselt number for each structure and four master correlation equations with geometrical parameter dependence were built to predict the regenerator performance. Thereafter, the constructal bifurcation regenerators were converted to equivalent porous media, and thus the main porous parameters were obtained for the full Stirling engine simulation in the next studies. Finally, the friction factor and Nusselt number of the constructal bifurcation regenerator were compared with those of other commonly used regenerators. It showed that the constructal bifurcation regenerator had a low flow resistance and moderate heat transfer, thus obtaining a high comprehensive performance. The superior comprehensive performance of the regenerator makes it possible to improve the performance of Stirling engines.

ACS Style

Minjie Yu; Feng Xin; Xiaotian Lai; Hui Xiao; Zhichun Liu; Wei Liu. Study of oscillating flows through a novel constructal bifurcation Stirling regenerator. Applied Thermal Engineering 2020, 184, 116413 .

AMA Style

Minjie Yu, Feng Xin, Xiaotian Lai, Hui Xiao, Zhichun Liu, Wei Liu. Study of oscillating flows through a novel constructal bifurcation Stirling regenerator. Applied Thermal Engineering. 2020; 184 ():116413.

Chicago/Turabian Style

Minjie Yu; Feng Xin; Xiaotian Lai; Hui Xiao; Zhichun Liu; Wei Liu. 2020. "Study of oscillating flows through a novel constructal bifurcation Stirling regenerator." Applied Thermal Engineering 184, no. : 116413.

Journal article
Published: 20 November 2020 in Energy Conversion and Management
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

Xiaotian 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.

Journal article
Published: 17 November 2020 in Renewable Energy
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

Hui 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.

Journal article
Published: 04 November 2020 in Applied Thermal Engineering
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Loop heat pipe, acting as one of the applications of porous media, has been extensively researched for its reliability and robustness. In order to enhance the heat transfer capacity of the loop heat pipe and adapt it to long-distance thermal control system, high-performance capillary wick is urgently required. In this paper, a comprehensive study about the biporous wick fabrication and operating mechanism is introduced. Contrasting to the conventional monoporous wick, the coaction of large and small pores could reduce the flow resistance and sustain sufficient capillary force. The driving force for loop circulation was comprised of capillary force, phase-change driving force, and gravity force. Furthermore, a flat-plate loop heat pipe with long heat transfer distance was constructed to test the performance limit of the biporous wick. Test results under horizontal condition indicated that the loop transferred the maximum heat load of 110 W (heat flux of 6.6 W/cm2) and the minimum thermal resistance was 0.382 °C/W. Besides, the intermittent formation of vapor phase inside compensation chamber would cause the temperature pulsation during low heat load range. While increasing the heat load, the subcooled liquid became sufficient and the pulsation was restrained. By introducing gravity effect at a tilt angle of 4.6 °, the working performance was improved for the wick could be quickly infiltrated by the subcooled fluid even under long heat transfer distance. The maximum heat load was 330 W (heat flux of 19.9 W/cm2) and the minimum thermal resistance was 0.161 °C/W at a heat load of 240 W.

ACS Style

Zikang Zhang; Runze Zhao; Zhichun Liu; Wei Liu. Application of biporous wick in flat-plate loop heat pipe with long heat transfer distance. Applied Thermal Engineering 2020, 184, 116283 .

AMA Style

Zikang Zhang, Runze Zhao, Zhichun Liu, Wei Liu. Application of biporous wick in flat-plate loop heat pipe with long heat transfer distance. Applied Thermal Engineering. 2020; 184 ():116283.

Chicago/Turabian Style

Zikang Zhang; Runze Zhao; Zhichun Liu; Wei Liu. 2020. "Application of biporous wick in flat-plate loop heat pipe with long heat transfer distance." Applied Thermal Engineering 184, no. : 116283.

Journal article
Published: 14 October 2020 in Applied Thermal Engineering
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Porous media are applied extensively in energy systems. However, the large flow resistance caused by porous media restricts the energy utilization and conversion efficiency. To reduce flow resistance, a constructal bifurcation filler was proposed as an alternative to the porous media filler based on constructal concept and fluid disturbance intensification idea. The two fillers were fitted in the circular tubes to investigate and compare their thermo-hydraulic characteristics. The fluid flow and heat transfer mechanisms of the two types of tubes were analyzed. The fluid disturbance intensification is the dominant mechanism of the heat transfer enhancement in the tube with the constructal bifurcation filler. Moreover, the flow resistance of the tube with the constructal bifurcation filler is decreased significantly, by 78.51–93.33%, compared to the tube with the porous media filler. Meanwhile, in contrast to the traditional fluid disturbance intensification elements, an excellent temperature uniformity similar to that of porous media is obtained for the constructal bifurcation filler. Furthermore, the efficiency evaluation criteria value is 3.66–8.77. Thus, the constructal bifurcation filler was demonstrated to exhibit superior comprehensive performance and is an effective solution for diminishing the flow resistance and improving the energy utilization efficiency. Finally, the effects of structure parameters, such as the wire mesh pitch s and inclined angle α, on the thermo-hydraulic performance of the tube with the constructal bifurcation filler were investigated.

ACS Style

Minjie Yu; Xiaotian Lai; Hui Xiao; Zhichun Liu; Wei Liu. A study on flow and heat transfer characteristics of a constructal bifurcation filler in the circular tube. Applied Thermal Engineering 2020, 183, 116205 .

AMA Style

Minjie Yu, Xiaotian Lai, Hui Xiao, Zhichun Liu, Wei Liu. A study on flow and heat transfer characteristics of a constructal bifurcation filler in the circular tube. Applied Thermal Engineering. 2020; 183 ():116205.

Chicago/Turabian Style

Minjie Yu; Xiaotian Lai; Hui Xiao; Zhichun Liu; Wei Liu. 2020. "A study on flow and heat transfer characteristics of a constructal bifurcation filler in the circular tube." Applied Thermal Engineering 183, no. : 116205.

Journal article
Published: 02 October 2020 in Applied Thermal Engineering
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Mini-channel heat sinks are popular in cooling high heat flux devices due to the high convective heat transfer performance associated with moderate pressure drop penalty. It is of great significance to further improve the thermal hydraulic performance in the mini-channel heat sink so as to adapt it to higher heat flux conditions. In this paper, a new method of realizing the optimized flow field to enhance the thermal hydraulic performance was carried out successfully in the mini-channel heat sink. The chosen mini-channel heat sink was 30 mm× 30 mm in substrate size with Reynolds number ranging from 100 to 1100. Through conjugate heat transfer optimization based on exergy destruction minimization principle, the optimized flow pattern was characterized by three pairs of longitudinal swirls flow. Subsequently, the inclined parallelepiped ribs were proposed to realize the optimized flow pattern in the mini-channel heat sink. The heat transfer enhancement mechanism was investigated by analyzing velocity distributions, temperature distributions, and heat convection intensity. Besides, the total thermal resistance was decreased and the exergy destruction minimization principle was verified. As a result, the variation ranges of Nu/Nu0, f/f0, efficiency evaluation criterion (EEC), and overall performance criterion (R3) were 1.35-5.92, 1.27-8.75, 0.68-1.12, and 1.31-4.22, respectively. The maximum average heat flux could achieve 3.2×106 W/m2 within a temperature difference of 60K between substrate and fluid. The configured parameters pitch ratio (PR) and width ratio (WR) were recommended as 1 and 0.2, respectively. This work is conducive to the structural design of mini-channel heat sinks.

ACS Style

Hui Xiao; Zhichun Liu; Wei Liu. Conjugate heat transfer enhancement in the mini-channel heat sink by realizing the optimized flow pattern. Applied Thermal Engineering 2020, 182, 116131 .

AMA Style

Hui Xiao, Zhichun Liu, Wei Liu. Conjugate heat transfer enhancement in the mini-channel heat sink by realizing the optimized flow pattern. Applied Thermal Engineering. 2020; 182 ():116131.

Chicago/Turabian Style

Hui Xiao; Zhichun Liu; Wei Liu. 2020. "Conjugate heat transfer enhancement in the mini-channel heat sink by realizing the optimized flow pattern." Applied Thermal Engineering 182, no. : 116131.

Journal article
Published: 07 September 2020 in International Journal of Heat and Mass Transfer
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Turbulent heat transfer attracts continuous attention from researchers due to the high convective heat transfer performance. In the mini-channel heat sink, turbulent heat transfer enhancement measures may improve the heat transfer coefficient further and reduce the mass flow rate. However, there is lack of turbulent heat transfer enhancement researches in the mini-channel heat sink due to the difficulty caused by entrance effect. In this paper, a novel heat transfer enhancement concept of enhancing the original flow pattern was successfully applied to enhance the turbulent heat transfer in the mini-channel heat sink. The investigation was carried out in a mini-channel heat sink whose substrate size was 50mm × 50mm with Reynolds number ranging from 3600 to 6800. The original flow pattern in the conventional heat sink was revealed firstly. Subsequently, the v-ribs roughness was applied to generate multi-longitudinal swirls flow so as to enhance the original flow pattern. The numerical results indicated that the variation ranges of Nu/Nu0, f/f0, EEC, and R3 were 1.71–3.55, 2.76–7.99, 0.32–0.89, and 1.12–2.06, respectively, in the mini-channel. Besides, the maximum average heat flux of the substrate could achieve 5.79 W/mm2 within a temperature difference of 60 K. In addition, this paper also investigated the thermal resistance and irreversibility in the mini-channel heat sink. This work may promote the development of heat transfer enhancement.

ACS Style

Hui Xiao; Zhichun Liu; Wei Liu. Turbulent heat transfer enhancement in the mini-channel by enhancing the original flow pattern with v-ribs. International Journal of Heat and Mass Transfer 2020, 163, 120378 .

AMA Style

Hui Xiao, Zhichun Liu, Wei Liu. Turbulent heat transfer enhancement in the mini-channel by enhancing the original flow pattern with v-ribs. International Journal of Heat and Mass Transfer. 2020; 163 ():120378.

Chicago/Turabian Style

Hui Xiao; Zhichun Liu; Wei Liu. 2020. "Turbulent heat transfer enhancement in the mini-channel by enhancing the original flow pattern with v-ribs." International Journal of Heat and Mass Transfer 163, no. : 120378.

Journal article
Published: 30 May 2020 in Polymers
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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.

ACS Style

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 Style

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 (6):1255.

Chicago/Turabian Style

Bo 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.

Journal article
Published: 26 May 2020 in Applied Thermal Engineering
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Solar air heaters (SAHs) are widely used devices for solar energy utilization at low temperature. The low convective heat transfer performance limits the energy conversion efficiency. This paper was aimed at investigating the flow characteristics and heat transfer enhancement mechanism, thermal hydraulic performance, and energy conversion efficiency of the SAH fitted with novel inclined trapezoidal vortex generators (ITVGs). The heat transfer performance and flow characteristics of a simplified unit were obtained by numerical simulation. A pair of longitudinal swirls were found close to both sides of each ITVG and the shape of vortex was rectangular in the front view. In the range of this paper, the order of overall thermal hydraulic performance for four different arrangements was listed as: upwind aligned (A1) > mixed staggered (A4) > upwind staggered (A2) > downwind aligned (A3). Furthermore, the A1 arrangement was applied to study the thermal hydraulic performance by altering parameters b/pt, e/H, and pl/H with Reynolds number ranging from 6000 to 18,000. The range of Nu/Nu0, f/f0, EEC, and R3 were 1.24–3.71, 1.39–11.8, 0.26–0.98 and 1.11–1.89, respectively. On this basis, energy and exergy efficiency evaluations were carried out on the practical SAH integrated by sixteen basic units. The energy efficiency and exergy efficiency could be maximally enhanced by 24% and 31% compared with the smooth SAH, respectively.

ACS Style

Hui Xiao; Zhimin Dong; Zhichun Liu; Wei Liu. Heat transfer performance and flow characteristics of solar air heaters with inclined trapezoidal vortex generators. Applied Thermal Engineering 2020, 179, 115484 .

AMA Style

Hui Xiao, Zhimin Dong, Zhichun Liu, Wei Liu. Heat transfer performance and flow characteristics of solar air heaters with inclined trapezoidal vortex generators. Applied Thermal Engineering. 2020; 179 ():115484.

Chicago/Turabian Style

Hui Xiao; Zhimin Dong; Zhichun Liu; Wei Liu. 2020. "Heat transfer performance and flow characteristics of solar air heaters with inclined trapezoidal vortex generators." Applied Thermal Engineering 179, no. : 115484.

Journal article
Published: 16 April 2020 in Applied Thermal Engineering
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This paper presents a loop heat pipe (LHP) with a pump to overcome the drawbacks of traditional loop heat pipes, such as limited heat transfer distance and temperature oscillation. The mechanical pump used in the loop is a centrifugal micropump which is light-weighted, small-sized and high-speed. In order to avoid the occurrence of cavitation and get a better character of the loop, ammonia is chosen as the working fluid. In consideration of the compatibility between working fluid and material, stainless steel is used to fabricate the whole loop. Meanwhile a biporous nickel wick is sintered to provide the capillary force. The effective heat transfer distance of the loop is 2320 mm. The experiment is conducted under different power of the pump and various temperature of the heat sink. Test results figure out that the system quickly responds to varible heat load and no temperature oscillation occurs. If the heated surface temperature is limited below 80 °C, the loop could handle a maximum heat dissipation of 370 W (heat flux = 36.35 W/cm2) when the power consumption of the pump is 4 W and the temperature of heat sink is −10 °C. Under this circumstance the thermal resistance of the evaporator is 0.176 K/W.

ACS Style

Hao Zhang; Chi Jiang; Zikang Zhang; Zhichun Liu; Xiaobing Luo; Wei Liu. A study on thermal performance of a pump-assisted loop heat pipe with ammonia as working fluid. Applied Thermal Engineering 2020, 175, 115342 .

AMA Style

Hao Zhang, Chi Jiang, Zikang Zhang, Zhichun Liu, Xiaobing Luo, Wei Liu. A study on thermal performance of a pump-assisted loop heat pipe with ammonia as working fluid. Applied Thermal Engineering. 2020; 175 ():115342.

Chicago/Turabian Style

Hao Zhang; Chi Jiang; Zikang Zhang; Zhichun Liu; Xiaobing Luo; Wei Liu. 2020. "A study on thermal performance of a pump-assisted loop heat pipe with ammonia as working fluid." Applied Thermal Engineering 175, no. : 115342.

Journal article
Published: 12 March 2020 in International Journal of Thermal Sciences
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A novel tube insert, fluid exchanger inserts, is proposed and numerically investigated for enhancing convective heat transfer of laminar oil flow in a circular tube. Effects of parameters including diameter ratio and number of inserts on convective heat transfer performance are also investigated. In the present work, servotherm medium oil is selected as the working fluid. It is found that the heat transfer performance is effectively enhanced as the thermal boundary layer is completely destroyed when the fluid passes through the fluid exchanger inserts. The Nusselt number and friction factor of the tube with fluid exchanger inserts are enhanced to 1.63–2.69 and 1.72–7.01 times that of the plain tube, respectively. Thus, the performance evaluation criterion ranges from 1.24 to l.62. Moreover, exergy analysis is conducted to appraise the thermodynamic performance of the tube with fluid exchanger inserts. It is found that the exergy efficiency of the enhanced tube is improved by 0.3%–1.9% compared to the plain tube.

ACS Style

Peng Liu; Zhimin Dong; Jinyi Lv; Feng Shan; Zhichun Liu; Wei Liu. Numerical study on thermal-hydraulic performance and exergy analysis of laminar oil flow in a circular tube with fluid exchanger inserts. International Journal of Thermal Sciences 2020, 153, 106365 .

AMA Style

Peng Liu, Zhimin Dong, Jinyi Lv, Feng Shan, Zhichun Liu, Wei Liu. Numerical study on thermal-hydraulic performance and exergy analysis of laminar oil flow in a circular tube with fluid exchanger inserts. International Journal of Thermal Sciences. 2020; 153 ():106365.

Chicago/Turabian Style

Peng Liu; Zhimin Dong; Jinyi Lv; Feng Shan; Zhichun Liu; Wei Liu. 2020. "Numerical study on thermal-hydraulic performance and exergy analysis of laminar oil flow in a circular tube with fluid exchanger inserts." International Journal of Thermal Sciences 153, no. : 106365.