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Boil-off gas (BOG) reliquefaction plays an important role in the process of LNG transportation and storage. In this paper, an improved BOG reliquefaction system to fit the different refrigerant, consisting of two evaporative refrigeration cycle subsystems and one BOG subsystem, was investigated. Three cases with different refrigerant compositions and combinations were studied to explore the most suitable scheme for the proposed system. All cases were simulated using Aspen HYSYS and optimized using a multi-objective genetic algorithm (GA) with specific energy consumption (SEC) as the objective function, followed by exergy and energy analyses. The results showed that the performance of all three cases improved to different degrees after optimization, and that all optimized cases compared favorably to the reference system. In particular, the optimized Case 3, which used mixed refrigerants in both the high-temperature refrigeration subsystem (HTRS) and the low-temperature refrigeration subsystem (LTRS), showed the best performance, with a coefficient of performance (COP) of 0.322, an exergy efficiency (η) of 0.519, and an SEC of 0.506 kW·h/kgLNG In addition, a comparative evaluation was carried out between the composite curves and temperature differences in the main heat exchangers and the exergy analysis results, which shows different matching degrees according to different refrigerant types and is related to heat transfer performance, and can provide guidance for the selection of different refrigerants in different pressure and temperature ranges in follow-up research.
Shilin Li; Zhongchao Zhao; Zhengchao Chen; Weiqin Zeng; Huizhi Gong. Optimization and analysis of thermodynamic performance of boil-off gas reliquefaction system with multiple refrigerant combinations. Sustainable Energy Technologies and Assessments 2021, 47, 101408 .
AMA StyleShilin Li, Zhongchao Zhao, Zhengchao Chen, Weiqin Zeng, Huizhi Gong. Optimization and analysis of thermodynamic performance of boil-off gas reliquefaction system with multiple refrigerant combinations. Sustainable Energy Technologies and Assessments. 2021; 47 ():101408.
Chicago/Turabian StyleShilin Li; Zhongchao Zhao; Zhengchao Chen; Weiqin Zeng; Huizhi Gong. 2021. "Optimization and analysis of thermodynamic performance of boil-off gas reliquefaction system with multiple refrigerant combinations." Sustainable Energy Technologies and Assessments 47, no. : 101408.
The printed circuit heat exchanger (PCHE) with discontinuous fins is a novel type of compact and highly efficient plate heat exchanger, which has superior thermal hydraulic performance. The morphology and characteristics of the flow channel greatly affect the performance of the PCHE. The discontinuous airfoil fins are used in PCHE channel design because they can affect the flow and heat transfer by increasing the heat transfer area and the disturbance in the channel. In this paper, the effects of different staggered distance (Ls) and transverse distance (Lv) of airfoil fin arrangements on the heat transfer and flow of supercritical nitrogen in the PCHE are numerically simulated using ANSYS Fluent. Simulation results and subsequent analysis show that the appropriate decrease in Ls and reduction in Lv between the two rows of fins can improve the convective heat transfer of the PCHE. A fully staggered arrangement of fins (Ls = 1.2) and an appropriate increase in the Lv can mitigate pressure drop. The comprehensive performance of different channel geometries is compared by the performance evaluation criteria (PEC) in this study. It is shown that considering flow resistance and heat transfer, the comprehensive heat transfer performance can be enhanced by properly increasing the staggered distance and the vertical distance between fins. When Ls = 1.2 mm and Lv = 1.25 mm, the PEC value of the staggered channel is the highest, which is 11.6% higher than that of the parallel channel on average.
Shan Yang; Zhongchao Zhao; Yong Zhang; Zhengchao Chen; Min Yang. Effects of Fin Arrangements on Thermal Hydraulic Performance of Supercritical Nitrogen in Printed Circuit Heat Exchanger. Processes 2021, 9, 861 .
AMA StyleShan Yang, Zhongchao Zhao, Yong Zhang, Zhengchao Chen, Min Yang. Effects of Fin Arrangements on Thermal Hydraulic Performance of Supercritical Nitrogen in Printed Circuit Heat Exchanger. Processes. 2021; 9 (5):861.
Chicago/Turabian StyleShan Yang; Zhongchao Zhao; Yong Zhang; Zhengchao Chen; Min Yang. 2021. "Effects of Fin Arrangements on Thermal Hydraulic Performance of Supercritical Nitrogen in Printed Circuit Heat Exchanger." Processes 9, no. 5: 861.
A Printed Circuit Heat Exchanger (PCHE) is a type of highly complete and efficient heat exchanger that consists of numerous mini/micro-channels and has been successfully applied to the Liquefied Natural Gas (LNG) regasification project. During the research presented in this paper, the condensation flow and heat transfer performance of the R22 in PCHE hot side minichannels are analyzed via experiments and numerical simulations, respectively. A liquid nitrogen–R22 experimental loop is established to examine the pressure difference and heat transfer coefficient of R22 in the minichannels of the PCHE hot side. The inlet pressures of the R22 range from 0.5 MPa to 0.65 MPa, the mass flux values are changed from 10.52 kg m−2s−1 to 109.42 kg m−2s−1, and the inlet temperatures vary from 273 K to 289 K. The differences between experiments and simulations are analyzed by comparing the experimental values of the Nusselt number (Nu) and the friction pressure gradient with the numerical ones. Furthermore, the influences of pressure and mass flux on the Nu, as well as the friction pressure gradient, are analyzed in depth through condensation flow regimes to explore the underlying mechanism giving the results.
Shilin Li; Zhongchao Zhao; Yanrui Zhang; Haijia Xu; Weiqin Zeng. Experimental and Numerical Analysis of Condensation Heat Transfer and Pressure Drop of Refrigerant R22 in Minichannels of a Printed Circuit Heat Exchanger. Energies 2020, 13, 6589 .
AMA StyleShilin Li, Zhongchao Zhao, Yanrui Zhang, Haijia Xu, Weiqin Zeng. Experimental and Numerical Analysis of Condensation Heat Transfer and Pressure Drop of Refrigerant R22 in Minichannels of a Printed Circuit Heat Exchanger. Energies. 2020; 13 (24):6589.
Chicago/Turabian StyleShilin Li; Zhongchao Zhao; Yanrui Zhang; Haijia Xu; Weiqin Zeng. 2020. "Experimental and Numerical Analysis of Condensation Heat Transfer and Pressure Drop of Refrigerant R22 in Minichannels of a Printed Circuit Heat Exchanger." Energies 13, no. 24: 6589.
This study experimentally investigated the cascaded start-up performance of thermosyphon with a flat evaporating surface combined with different sizes of micro-pillars. The thermosyphon was composed of a condenser section and an evaporator section. Different sizes of micro-pillar were processed on the surface of the evaporator bottom plate to enhance the heat transfer. A smooth flat surface was used as the standard reference for comparison with the micro-pillar surfaces. Deionized water was used as the working fluid to cool the condenser section of the thermosyphon. The operating pressure of thermosyphon was measured using a pressure sensor. Additionally, the evaporator section wall temperature and the temperature and flow rate of the cooling water were measured at nine different heat fluxes. The start-up performances of the thermosyphon with a smooth evaporator bottom plate (THSE) and thermosyphon with a micro-pillar in the evaporator bottom plate (THMPE) were compared. The THSE had a longer start-up time and a higher start-up temperature than the THMPE. When the heat flux was 68.6 W/cm2, the start-up time of the THMPE with a micro-pillar width of 0.2 mm and a height of 0.8 mm was reduced by 57.1% compared to THSE, and the start-up temperature was reduced by 28%. Thermosyphons with different micro-pillar widths showed various start-up performances for different heat fluxes. For a narrow micro-pillar width, THMPEs with larger micro-pillar heights had a lower start-up temperature and a shorter start-up time. As the micro-pillar width increased, the micro-pillar height had a different and more complex effect on the start-up performance of the thermosyphon. When the micro-pillar heights were 0.2 mm and 0.4 mm, the thermosyphon with wider micro-pillars had a longer start-up time with a lower heat flux but a shorter start-up time with a higher heat flux. When the micro-pillar heights were 0.6 mm and 0.8 mm, varying the micro-pillar width had a smaller influence on the start-up performance of the thermosyphon, but was dependent on the heat flux.
Zhongchao Zhao; Xiaolong Ma; Kai Zhao; Xudong Chen; Shilin Li; Shan Yang. Experimental investigation of the characteristics of thermosyphon with flat evaporator and micro-pillar arrays. International Journal of Thermal Sciences 2020, 158, 106541 .
AMA StyleZhongchao Zhao, Xiaolong Ma, Kai Zhao, Xudong Chen, Shilin Li, Shan Yang. Experimental investigation of the characteristics of thermosyphon with flat evaporator and micro-pillar arrays. International Journal of Thermal Sciences. 2020; 158 ():106541.
Chicago/Turabian StyleZhongchao Zhao; Xiaolong Ma; Kai Zhao; Xudong Chen; Shilin Li; Shan Yang. 2020. "Experimental investigation of the characteristics of thermosyphon with flat evaporator and micro-pillar arrays." International Journal of Thermal Sciences 158, no. : 106541.
Visualization-based nucleate pool boiling experiments are carried out on different sizes of square micropillar array surfaces (SMAS) and plain surface using deionized water as working fluid at atmospheric pressure. The quantitative measurements of the bubble dynamics, including the nucleation site density, the bubble departure diameter and the frequency, are obtained using a high-speed camera with microscope. The obtained results show that the SMAS, with square micropillar in the range of 0.2–0.8 mm height and width (the pitch between the micropillar is equal to the micropillar width), has a considerably lower wall superheat, which enhanced the heat transfer coefficient (HTC) by 32–203% compared to the plain surface. Generally, the boiling heat transfer intensifies with the increase in the square micropillar height keeping the width constant. But the tendency reverses at high heat flux levels. The high-speed visualization reveals that the higher square micropillar has faster bubble departure frequency at low heat flux, because higher micropillar is conducive to induce capillary flow and aids in separating the paths of departing bubble and replenishment liquid. However, the increase of bubble diameter at high heat flux restrains bubble departure with higher square micropillar. In addition, the increase of square micropillar width is conducive to enhancing the boiling heat transfer and the tendency is reversed at high heat flux levels when the square micropillar height is kept constant. The bubble dynamics are compared with the predictions using various correlations from the literature.
Zhongchao Zhao; Xiaolong Ma; Shilin Li; Shan Yang; Liangqin Huang. Visualization-based nucleate pool boiling heat transfer enhancement on different sizes of square micropillar array surfaces. Experimental Thermal and Fluid Science 2020, 119, 110212 .
AMA StyleZhongchao Zhao, Xiaolong Ma, Shilin Li, Shan Yang, Liangqin Huang. Visualization-based nucleate pool boiling heat transfer enhancement on different sizes of square micropillar array surfaces. Experimental Thermal and Fluid Science. 2020; 119 ():110212.
Chicago/Turabian StyleZhongchao Zhao; Xiaolong Ma; Shilin Li; Shan Yang; Liangqin Huang. 2020. "Visualization-based nucleate pool boiling heat transfer enhancement on different sizes of square micropillar array surfaces." Experimental Thermal and Fluid Science 119, no. : 110212.
Printed circuit heat exchanger (PCHE) is an alternative competitor to be employed in the Liquid Natural Gas (LNG) regasification as vaporizers to meet the increasing demand for the clean energy in the economic development. Different models have been proposed so far for the PCHE, where the majority of them are simplified to a single channel to reduce the computational cost and time. Conventional methods have remarkable challenges, including high computational expense and limitations in engineering applications. In order to resolve these shortcomings, an innovative analysis and design method is proposed in the present study. In the present study, an innovative analysis and design method is proposed, which is based on the thermal network method. The proposed method benefits from both numerical and analytical approaches. It obtains the overall thermal-hydraulic performance of both cold and hot sides and captures the sharp variations of the thermodynamic properties of the supercritical nitrogen. The cross-flow PCHE is divided into a set of typical layers. Moreover, the typical layer is assumed to consist of a set of units, which include cold and hot channels and walls. These units are managed by a code that couples the thermal-hydraulic performance by both hot and cold fluid beginning from the given inlet conditions. Considering the flammable and explosive properties of Natural Gas (NG), liquid nitrogen is selected as the cold fluid. Furthermore, the thermal-hydraulic performance of the cross-flow PCHE is analyzed with different inlet conditions. Heat transfer and flow performance of the supercritical nitrogen is significantly affected by its thermal properties. It is observed that the heat transfer effectiveness increases as the inlet pressure of the cold fluid increases, which is due to the improvement of the overall nonuniformity and coordination angle of heat transfer coefficients. According to the performance evaluation criteria, the evaluation of the thermal-hydraulic performance of cross-flow PCHE is determined by inlet conditions of both cold and hot sides.
Zhongchao Zhao; Xudong Chen; Shilin Li; Shan Yang; Liangqin Huang. Methodology of design and analysis on the thermal hydraulic performance of the cross-flow printed circuit heat exchanger. International Journal of Heat and Mass Transfer 2020, 156, 119756 .
AMA StyleZhongchao Zhao, Xudong Chen, Shilin Li, Shan Yang, Liangqin Huang. Methodology of design and analysis on the thermal hydraulic performance of the cross-flow printed circuit heat exchanger. International Journal of Heat and Mass Transfer. 2020; 156 ():119756.
Chicago/Turabian StyleZhongchao Zhao; Xudong Chen; Shilin Li; Shan Yang; Liangqin Huang. 2020. "Methodology of design and analysis on the thermal hydraulic performance of the cross-flow printed circuit heat exchanger." International Journal of Heat and Mass Transfer 156, no. : 119756.
In this paper, the influence of wettability properties on the start-up characteristics of two-phase closed thermosyphons (TPCTs) is investigated. Chemical coating and etching techniques are performed to prepare the surfaces with different wettabilities that is quantified in the form of the contact angle (CA). The 12 TPCTs are processed including the same CA and a different CA combination on the inner surfaces inside both the evaporator and the condenser sections. For TPCTs with the same wettability properties, the introduction of hydrophilic properties inside the evaporator section not only significantly reduces the start-up time but also decreases the start-up temperature. For example, the start-up time of a TPCT with CA = 28° at 40 W, 60 W and 80 W is 46%, 50% and 55% shorter than that of a TPCT with a smooth surface and the wall superheat degrees is 55%, 39% and 28% lower, respectively. For TPCTs with combined hydrophilic and hydrophobic properties, the start-up time spent on the evaporator section with hydrophilic properties is shorter than that of the hydrophobic evaporator section and the smaller CA on the condenser section shows better results. The start-up time of a TPCT with CA = 28° on the evaporator section and CA = 105° on the condenser section has the best start-up process at 40 W, 60 W and 80 W which is 14%, 22% and 26% shorter than that of a TPCT with smooth surface. Thus, the hydrophilic and hydrophobic modifications play a significant role in promoting the start-up process of a TPCT.
Xiaolong Ma; Zhongchao Zhao; Pengpeng Jiang; Shan Yang; Shilin Li; Xudong Chen. Investigation of Start-Up Characteristics of Thermosyphons Modified with Different Hydrophilic and Hydrophobic Inner Surfaces. Energies 2020, 13, 765 .
AMA StyleXiaolong Ma, Zhongchao Zhao, Pengpeng Jiang, Shan Yang, Shilin Li, Xudong Chen. Investigation of Start-Up Characteristics of Thermosyphons Modified with Different Hydrophilic and Hydrophobic Inner Surfaces. Energies. 2020; 13 (3):765.
Chicago/Turabian StyleXiaolong Ma; Zhongchao Zhao; Pengpeng Jiang; Shan Yang; Shilin Li; Xudong Chen. 2020. "Investigation of Start-Up Characteristics of Thermosyphons Modified with Different Hydrophilic and Hydrophobic Inner Surfaces." Energies 13, no. 3: 765.
Printed circuit heat exchangers (PCHE) are a new kind of high efficiency and compact plate heat exchangers, which can be used in extreme conditions, such as high pressure, high heat flux and volumetric limitation. Supercritical fluids have various favorable characteristics when used as working fluids in heat exchangers. In this paper, the thermal-hydraulic performance of supercritical nitrogen was studied both experimentally and numerically in an airfoil fin PCHE. The mass flow rate varied from 203 kg·m−2·s−1 to 228 kg·m−2·s−1 while the operating pressure ranged from 5 MPa to 8 MPa. The cold-side outlet temperature and pressure drop in the PCHE were investigated experimentally. The outlet temperature increased as pressure increased and the average outlet temperature at 8MPa was 7.81 K higher than that at 5 MPa for the same mass flow rate. The gradient of pressure drop increased as the mass flow rate increased. Moreover, a numerical analysis of nitrogen in the channel of airfoil fins PCHE was conducted. Nusselt number and Fanning friction factor correlations were developed for Reynolds number values from 10000 to 14500. The accuracy of the proposed correlations was validated using the experimental and numerical data obtained, and results showed that they have a good accuracy for predicting the thermal hydraulic performance of supercritical nitrogen in the channel of airfoil fin PCHE.
Zhongchao Zhao; Yong Zhang; Xudong Chen; Xiaolong Ma; Shan Yang; Shilin Li. Experimental and numerical investigation of thermal-hydraulic performance of supercritical nitrogen in airfoil fin printed circuit heat exchanger. Applied Thermal Engineering 2019, 168, 114829 .
AMA StyleZhongchao Zhao, Yong Zhang, Xudong Chen, Xiaolong Ma, Shan Yang, Shilin Li. Experimental and numerical investigation of thermal-hydraulic performance of supercritical nitrogen in airfoil fin printed circuit heat exchanger. Applied Thermal Engineering. 2019; 168 ():114829.
Chicago/Turabian StyleZhongchao Zhao; Yong Zhang; Xudong Chen; Xiaolong Ma; Shan Yang; Shilin Li. 2019. "Experimental and numerical investigation of thermal-hydraulic performance of supercritical nitrogen in airfoil fin printed circuit heat exchanger." Applied Thermal Engineering 168, no. : 114829.
In this paper, the thermal performance of thermosyphon with a flat evaporating surface combined with different sizes of micro pillars was investigated by experimental method. Micro pillars with different sizes were fabricated on the surface of the evaporator bottom plate to enhance heat exchange. An experimental platform was designed and constructed to test the heat transfer performance of the thermosyphon. Deionized water was chosen as the working fluid and the condenser section of the thermosyphon was cooled using water cooling. The operating pressure of the thermosyphon was measured by a pressure sensor to obtain the corresponding saturated temperature. The wall temperature of the evaporator section, the operating pressure of the thermosyphon, as well as the temperature and flow rate of the cooling water were detected for different heat flux. The evaporator section wall temperature (ESWT) and evaporator section wall superheat (ESWS) of the thermosyphon with a smooth evaporator bottom plate (THSE) or micro pillars on the evaporator bottom plate(THMPE)were comparatively studied. ESWT and ESWS of the thermosyphon with micro pillars were much lower than those of THSE. Generally, when the micro-pillar width was constant, heat transfer was intensified with increasing micro-pillar height. When the micro-pillar width was 200 μm, ESWT of the thermosyphon with a micro-pillar height of 200 μm was 12.1 °C higher than that of thermosyphon with a micro-pillar height of 800 μm at a heat flux of 68.6 W/cm2. When the micro-pillar heights were 200 μm and 400 μm, the variations of micro-pillar width evidently reduced ESWT. However, when the micro-pillar height was 600 μm and 800 μm, the variations of micro-pillar width barely affected ESWT due to the capillarity and disturbance of bubbles motion caused by micro-pillar changes. At a smaller micro-pillar width, the thermosyphon with higher micro pillars had lower ESWS. When the heights of micro pillars were 200 μm and 400 μm, the increase of micro-pillar width was conducive to reducing ESWS. When the heights of micro pillars were 600 μm and 800 μm, a smaller micro-pillar width better reduced ESWS of the thermosyphon.
Zhongchao Zhao; Kai Zhao; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. Thermal performance of thermosyphon with flat evaporating surface combined with different sizes of micro pillars. Powder Technology 2019, 361, 633 -641.
AMA StyleZhongchao Zhao, Kai Zhao, Xiaolong Ma, Xudong Chen, Shilin Li, Shan Yang. Thermal performance of thermosyphon with flat evaporating surface combined with different sizes of micro pillars. Powder Technology. 2019; 361 ():633-641.
Chicago/Turabian StyleZhongchao Zhao; Kai Zhao; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. 2019. "Thermal performance of thermosyphon with flat evaporating surface combined with different sizes of micro pillars." Powder Technology 361, no. : 633-641.
The thermal‐hydraulic performance of printed circuit heat exchanger (PCHE) through an experimental vaporization process of supercritical nitrogen was investigated. The inlet temperature of supercritical nitrogen was controlled between 113 K and 129 K, while its pressure was controlled between 4.5 MPa and 6 MPa. The mass of supercritical nitrogen corresponds to the turbulent state on the cold side of PCHE, which was maintained at 299.94 kg/h. A numerical processing of the same supercritical nitrogen flow through a single channel of PCHE cold side was presented. The numerical results were validated by comparison with the experimental data. Both experimental and numerical results showed that the increased inlet supercritical nitrogen pressure improved the heat transfer performance and pressure drop decreased with increasing the pressure at the PCHE cold side. Furthermore, the Fanning friction coefficient (f) and the Nusselt number (Nu) of supercritical nitrogen flow obtained by numerical simulation and empirical correlation were compared.
Zhongchao Zhao; Xudong Chen; Xiao Zhang; Xiaolong Ma; Shan Yang. Experimental and numerical study on thermal‐hydraulic performance of printed circuit heat exchanger for liquefied gas vaporization. Energy Science & Engineering 2019, 8, 426 -440.
AMA StyleZhongchao Zhao, Xudong Chen, Xiao Zhang, Xiaolong Ma, Shan Yang. Experimental and numerical study on thermal‐hydraulic performance of printed circuit heat exchanger for liquefied gas vaporization. Energy Science & Engineering. 2019; 8 (2):426-440.
Chicago/Turabian StyleZhongchao Zhao; Xudong Chen; Xiao Zhang; Xiaolong Ma; Shan Yang. 2019. "Experimental and numerical study on thermal‐hydraulic performance of printed circuit heat exchanger for liquefied gas vaporization." Energy Science & Engineering 8, no. 2: 426-440.
The channels of a printed circuit heat exchanger (PCHE) can have different shapes, and the zigzag channel shape is one of the most widely used because of the relatively simple manufacturing process and low cost. However, the heat transfer enhancement of a zigzag channel is at the expense of increasing the pressure drop. In this paper, new channel shapes of a PCHE, i.e., a zigzag with an inserted straight channel and a zigzag channel with radian, were numerically investigated, with the aim of improving the heat transfer and reducing the pressure drop of supercritical LNG using the SST κ-ω model. The local and total pressure drop and heat transfer performance of supercritical LNG in a zigzag channel, zigzags with 1–5 mm inserted straight channels, and a zigzag channel with radian were analyzed by varying the mass flow rate from 1.83 × 10−4 to 5.49 × 10−4 kg/s. Performance evaluation criteria (PEC) were applied to compare the overall heat transfer performance of the zigzags with 1–5 mm inserted straight channels and a zigzag channel with radian to the zigzag channel of a PCHE. The maximum pressure drop for the zigzag channel was twice the minimum pressure drop for the zigzag channel with radian, while the convective heat transfer coefficient of the zigzag with a 4 mm inserted straight channel was higher, which was 1.2 times that of the zigzag channel with radian with the smallest convective heat transfer coefficient. The maximum value of the PEC with 1.099 occurred at a mass flow rate of 1.83 × 10−4 kg/s for the zigzag with a 4 mm inserted straight channel, while the minimum value of the PEC with 1.021 occurred at a mass flow rate of 5.49 × 10−4 kg/s for the zigzag with a 1 mm inserted straight channel. The zigzag with a 4 mm inserted straight channel had the best performance, as it had a higher PEC value at lower mass flow rates.
Zhongchao Zhao; Yimeng Zhou; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. Effect of Different Zigzag Channel Shapes of PCHEs on Heat Transfer Performance of Supercritical LNG. Energies 2019, 12, 2085 .
AMA StyleZhongchao Zhao, Yimeng Zhou, Xiaolong Ma, Xudong Chen, Shilin Li, Shan Yang. Effect of Different Zigzag Channel Shapes of PCHEs on Heat Transfer Performance of Supercritical LNG. Energies. 2019; 12 (11):2085.
Chicago/Turabian StyleZhongchao Zhao; Yimeng Zhou; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. 2019. "Effect of Different Zigzag Channel Shapes of PCHEs on Heat Transfer Performance of Supercritical LNG." Energies 12, no. 11: 2085.
Printed circuit heat exchanger (PCHE), with the core comprising many mini/microchannels, have been extensively studied, but few works involved two-phase flow. A simplified channel model of PCHE hot side was herein established to numerically explore the heat transfer and condensation flow performance of R22 in minichannels under different conditions. The model was a semicircular minichannel with 0.91 mm hydraulic diameter and 50 mm full length. The heat flux was kept at -77195 Wm−2, the inlet pressure was 0.63 MPa and the mass fluxes ranged from 58 to 93 kgm−2s−1. The condensation flow characteristics along the channel were analyzed. Four flow patterns, i.e. smooth-annular, wavy-annular, slug and bubbly, were noticed at different refrigerant mass fluxes and plotted as a flow pattern map. The effects of import vapor quality from 0.5 to 1 on pressure drop and heat transfer performance were evaluated. The heat transfer performance was optimal at the import vapor quality of 0.7. The impacts of refrigerant mass flux on pressure drop and local condensation heat transfer coefficient were assessed. Intermittent flow enhanced heat transfer. In addition, the correlations for local Nusselt number and Fanning friction factor were presented and compared with numerical data.
Zhongchao Zhao; Yanrui Zhang; Xudong Chen; Xiaolong Ma; Shan Yang; Shilin Li. A numerical study on condensation flow and heat transfer of refrigerant in minichannels of printed circuit heat exchanger. International Journal of Refrigeration 2019, 102, 96 -111.
AMA StyleZhongchao Zhao, Yanrui Zhang, Xudong Chen, Xiaolong Ma, Shan Yang, Shilin Li. A numerical study on condensation flow and heat transfer of refrigerant in minichannels of printed circuit heat exchanger. International Journal of Refrigeration. 2019; 102 ():96-111.
Chicago/Turabian StyleZhongchao Zhao; Yanrui Zhang; Xudong Chen; Xiaolong Ma; Shan Yang; Shilin Li. 2019. "A numerical study on condensation flow and heat transfer of refrigerant in minichannels of printed circuit heat exchanger." International Journal of Refrigeration 102, no. : 96-111.
The heat transfer characteristics of two-phase closed thermosyphons (TPCTs) modified with inner surfaces of various wettabilities were experimentally studied. The wettability, which was quantified as the contact angle inside the thermosyphons, was varied by chemical etching and coating. For TPCT1-TPCT3 and TPCT8-TPCT10, introducing hydrophilic properties inside the evaporator sections increased the heat transfer coefficients of both evaporator and condenser at the same power. The evaporator and condenser heat transfer coefficients of TPCT8 and TPCT9 with combined hydrophilic and hydrophobic properties were higher than those of TPCT7 with smooth surface. The thermal resistances of TPCT1-TPCT3 with hydrophilic properties were lower than those of TPCT4-TPCT6 with hydrophobic properties at 40 W, 60 W and 80 W respectively. At the same power, as the contact angles on the evaporator sections of TCPT1 to TCPT6 increased gradually, the overall thermal resistances were elevated. The thermal resistance of TPCT7 with smooth surface was lower than those of TPCT4-TPCT6 with hydrophobic properties but higher than those of TPCT8 and TPCT9 at the same power. The thermal resistances of TPCT8 and TPCT9 may be lower than that of TPCT1 if the input power was further increased. In addition, as the contact angles of TPCT1-PTCT6 increased, the effective thermal conductivities gradually declined at all heat input powers. The effective thermal conductivities of TPCT1-TPCT3 with hydrophilic properties exceeded those of TPCT4-TPCT6 with hydrophobic properties and TPCT7 with smooth surface at different input powers. At the same input power, the effective thermal conductivities of TPCT8-TPCT10 were higher than those of TPCT4-TPCT6 modified with the hydrophobic properties, TPCT7 with smooth surface, TPCT11 and TPCT12 but lower than that of TPCT1.
Zhongchao Zhao; Pengpeng Jiang; Yimeng Zhou; Yong Zhang; Yanrui Zhang. Heat transfer characteristics of two-phase closed thermosyphons modified with inner surfaces of various wettabilities. International Communications in Heat and Mass Transfer 2019, 103, 100 -109.
AMA StyleZhongchao Zhao, Pengpeng Jiang, Yimeng Zhou, Yong Zhang, Yanrui Zhang. Heat transfer characteristics of two-phase closed thermosyphons modified with inner surfaces of various wettabilities. International Communications in Heat and Mass Transfer. 2019; 103 ():100-109.
Chicago/Turabian StyleZhongchao Zhao; Pengpeng Jiang; Yimeng Zhou; Yong Zhang; Yanrui Zhang. 2019. "Heat transfer characteristics of two-phase closed thermosyphons modified with inner surfaces of various wettabilities." International Communications in Heat and Mass Transfer 103, no. : 100-109.
In this paper, we study a promising plate-type heat exchanger, the printed circuit heat exchanger (PCHE), which has high compactness and is suitable for high-pressure conditions as a vaporizer during vaporization. The thermal hydraulic performance of supercritical produce liquefied natural gas (LNG) in the zigzag channel of PCHE is numerically investigated using the SST κ-ω turbulence model. The thermo-physical properties of supercritical LNG from 6.5 MPa to 10MPa were calculated using piecewise-polynomial approximations of the temperature. The effect of the channel bend angle, mass flux and inlet pressure on local convection heat transfer coefficient, and pressure drop are discussed. The heat transfer and pressure loss performance are evaluated using the Nusselt and Euler numbers. Nu/Eu is proposed to evaluate the comprehensive heat transfer performance of PCHE by considering the heat transfer and pressure drop characteristics to find better bend angle and operating conditions. The supercritical LNG has a better heat transfer performance when bend angle is less than 15° with the mass flux ranging from 207.2 kg/(m2·s) to 621.6 kg/(m2·s), which improves at bend angle of 10° and lower compared to 15° at mass flux above 414.4 kg/(m2·s). The heat transfer performance is better at larger mass flux and lower operating pressures.
Zhongchao Zhao; Yimeng Zhou; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. Numerical Study on Thermal Hydraulic Performance of Supercritical LNG in Zigzag-Type Channel PCHEs. Energies 2019, 12, 548 .
AMA StyleZhongchao Zhao, Yimeng Zhou, Xiaolong Ma, Xudong Chen, Shilin Li, Shan Yang. Numerical Study on Thermal Hydraulic Performance of Supercritical LNG in Zigzag-Type Channel PCHEs. Energies. 2019; 12 (3):548.
Chicago/Turabian StyleZhongchao Zhao; Yimeng Zhou; Xiaolong Ma; Xudong Chen; Shilin Li; Shan Yang. 2019. "Numerical Study on Thermal Hydraulic Performance of Supercritical LNG in Zigzag-Type Channel PCHEs." Energies 12, no. 3: 548.
The transient thermal performance of phase change and heat and mass transfer in a two-phase closed thermosyphon are studied with computational fluid dynamics (CFD). A CFD model based on the volume of fluid technique is built. Deionized water is specified as the working fluid of this thermosyphon. The CFD model reproduces evaporation and condensation in the thermosyphon at different heating inputs. The average wall temperatures are also analyzed. Variations of average wall temperatures indicate that this thermosyphon reaches a steady state after 19 s, and starts to work in advance when the heating input increases. Moreover, thermal resistance is decreased until a minimum (0.552 K/W) by increasing the heating input, and the effective thermal conductivity is elevated to a maximum (2.07 × 106 W/m∙K).
Zhongchao Zhao; Yong Zhang; Yanrui Zhang; Yimeng Zhou; Hao Hu. Numerical Study on the Transient Thermal Performance of a Two-Phase Closed Thermosyphon. Energies 2018, 11, 1433 .
AMA StyleZhongchao Zhao, Yong Zhang, Yanrui Zhang, Yimeng Zhou, Hao Hu. Numerical Study on the Transient Thermal Performance of a Two-Phase Closed Thermosyphon. Energies. 2018; 11 (6):1433.
Chicago/Turabian StyleZhongchao Zhao; Yong Zhang; Yanrui Zhang; Yimeng Zhou; Hao Hu. 2018. "Numerical Study on the Transient Thermal Performance of a Two-Phase Closed Thermosyphon." Energies 11, no. 6: 1433.
As a renewable and high energy efficiency technology providing air conditioning and domestic hot water, the ground source heat pump system (GSHPS) has been extensively used worldwide in recent years. Compared with conventional systems, GSHPSs with heat recovery reject less heat into the soil and extract more heat from it, which can help reduce soil thermal imbalance in hot-summer and cold-winter regions. In this paper, conventional GSHPS, and GSHPS with different heat recovery ratios, in a typical city were compared based on thermal imbalance ratios, average soil temperatures and soil temperature increases. The transient system simulation software was used to simulate the operation performance of GSHPS. The thermal imbalance ratio and soil temperature decreased with increasing heat recovery ratio. After 20 years of operation, the soil thermal imbalance ratios of the GSHPS were 29.2%, 21.1%, 16%, and 5.2%, and the soil temperature rises were 8.78 °C, 5.25 °C, 3.44 °C, and 0.34 °C, while the heat recovery ratios were 0, 18%, 30% and 53%, respectively. Consequently, a GSHPS with heat recovery is a potentially efficient and economical approach for buildings in hot-summer and cold-winter regions.
Zhongchao Zhao; Rendong Shen; Weixian Feng; Yong Zhang; Yanrui Zhang. Soil Thermal Balance Analysis for a Ground Source Heat Pump System in a Hot-Summer and Cold-Winter Region. Energies 2018, 11, 1206 .
AMA StyleZhongchao Zhao, Rendong Shen, Weixian Feng, Yong Zhang, Yanrui Zhang. Soil Thermal Balance Analysis for a Ground Source Heat Pump System in a Hot-Summer and Cold-Winter Region. Energies. 2018; 11 (5):1206.
Chicago/Turabian StyleZhongchao Zhao; Rendong Shen; Weixian Feng; Yong Zhang; Yanrui Zhang. 2018. "Soil Thermal Balance Analysis for a Ground Source Heat Pump System in a Hot-Summer and Cold-Winter Region." Energies 11, no. 5: 1206.
The heat pump water heater (HPWH), as a portion of the eco-friendly technologies using renewable energy, has been applied for years in developed countries. Air-source heat pump water heaters and solar-assisted heat pump water heaters have been widely applied and have become more and more popular because of their comparatively higher energy efficiency and environmental protection. Besides use of the above resources, the heat pump water heater system can also adequately utilize an available water source. In order to study the thermal performance of the water-source heat pump water heater (WSHPWH) system, an experimental prototype using the cyclic heating mode was established. The heating performance of the water-source heat pump water heater system, which was affected by the difference between evaporator water fluxes, was investigated. The water temperature unfavorably exceeded 55 °C when the experimental prototype was used for heating; otherwise, the compressor discharge pressure was close to the maximum discharge temperature, which resulted in system instability. The evaporator water flux allowed this system to function satisfactorily. It is necessary to reduce the exergy loss of the condenser to improve the energy utilization of the system.
Zhongchao Zhao; Yanrui Zhang; Haojun Mi; Yimeng Zhou; Yong Zhang. Experimental Research of a Water-Source Heat Pump Water Heater System. Energies 2018, 11, 1205 .
AMA StyleZhongchao Zhao, Yanrui Zhang, Haojun Mi, Yimeng Zhou, Yong Zhang. Experimental Research of a Water-Source Heat Pump Water Heater System. Energies. 2018; 11 (5):1205.
Chicago/Turabian StyleZhongchao Zhao; Yanrui Zhang; Haojun Mi; Yimeng Zhou; Yong Zhang. 2018. "Experimental Research of a Water-Source Heat Pump Water Heater System." Energies 11, no. 5: 1205.
As a new kind of highly compact and efficient micro-channel heat exchanger, the printed circuit heat exchanger (PCHE) is a promising candidate satisfying the heat exchange requirements of liquefied natural gas (LNG) vaporization at low and high pressure. The effects of airfoil fin arrangement on heat transfer and flow resistance were numerically investigated using supercritical liquefied natural gas (LNG) as working fluid. The thermal properties of supercritical LNG were tested by utilizing the REFPROF software database. Numerical simulations were performed using FLUENT. The inlet temperature of supercritical LNG was 121 K, and its pressure was 10.5 MPa. The reference mass flow rate of LNG was set as 1.22 g/s for the vertical pitch Lv = 1.67 mm and the staggered pitch Ls = 0 mm, with the Reynolds number of about 3750. The SST k-ω model was selected and verified by comparing with the experimental data using supercritical liquid nitrogen as cold fluid. The airfoil fin PCHE had better thermal-hydraulic performance than that of the straight channel PCHE. Moreover, the airfoil fins with staggered arrangement displayed better thermal performance than that of the fins with parallel arrangement. The thermal-hydraulic performance of airfoil fin PCHE was improved with increasing Ls and Lv. Moreover, Lv affected the Nusselt number and pressure drop of airfoil fin PCHE more obviously. In conclusion, a sparser staggered arrangement of fins showed a better thermal-hydraulic performance in airfoil fin PCHE.
Zhongchao Zhao; Kai Zhao; Dandan Jia; Pengpeng Jiang; Rendong Shen. Numerical Investigation on the Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger. Energies 2017, 10, 1828 .
AMA StyleZhongchao Zhao, Kai Zhao, Dandan Jia, Pengpeng Jiang, Rendong Shen. Numerical Investigation on the Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger. Energies. 2017; 10 (11):1828.
Chicago/Turabian StyleZhongchao Zhao; Kai Zhao; Dandan Jia; Pengpeng Jiang; Rendong Shen. 2017. "Numerical Investigation on the Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger." Energies 10, no. 11: 1828.
As a new kind of highly compact and efficient micro-channel heat exchanger, printed circuit heat exchanger (PCHE) is a promising candidate satisfying the heat exchange requirements of liquefied natural gas (LNG) vaporization at low and high pressure. The effects of airfoil fin arrangement on heat transfer an flow resistance were numerically investigated using supercritical liquefied natural gas (LNG) as a working fluid. The thermal properties of supercritical LNG were tested by utilizing a REFPROF software database. Numerical simulation was performed using FLUENT. The inlet temperature of supercritical LNG was 121 K,and its pressure was 10.5MPa. The reference mass flow rate of LNG was set 1.22 g/s for the vertical pitch Lv = 1.67 mm and the staggered pitch Ls = 0 mm, with the Reynolds number of about 3750. The SST k-ω model with enhanced wall treatment was selected by comparing with the experimental data. The airfoil fin PCHE had better thermal-hydraulic performance than that of the straight channel PCHE. Moreover, the airfoil fins with staggered arrangement displayed better thermal performance than that of the fins with parallel arrangement. The thermal-hydraulic performance of airfoil fin PCHE was improved with increasing Ls and Lv. Moreover, Lv affected on the Nusselt number and pressure drop of airfoil fin PCHE more obviously. In conclusion, a sparser staggered arrangement of fins showed a better thermal-hydraulic performance in airfoil fin PCHE.
Zhongchao Zhao; Kai Zhao; Dandan Jia; Pengpeng Jiang; Rendong Shen. Numerical Investigation on Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger. 2017, 1 .
AMA StyleZhongchao Zhao, Kai Zhao, Dandan Jia, Pengpeng Jiang, Rendong Shen. Numerical Investigation on Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger. . 2017; ():1.
Chicago/Turabian StyleZhongchao Zhao; Kai Zhao; Dandan Jia; Pengpeng Jiang; Rendong Shen. 2017. "Numerical Investigation on Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger." , no. : 1.
Zhongchao Zhao; Jiaojiao Zhang; Dandan Jia; Kai Zhao; Xiao Zhang; Pengpeng Jiang. Thermal performance analysis of pool boiling on an enhanced surface modified by the combination of microstructures and wetting properties. Applied Thermal Engineering 2017, 117, 417 -426.
AMA StyleZhongchao Zhao, Jiaojiao Zhang, Dandan Jia, Kai Zhao, Xiao Zhang, Pengpeng Jiang. Thermal performance analysis of pool boiling on an enhanced surface modified by the combination of microstructures and wetting properties. Applied Thermal Engineering. 2017; 117 ():417-426.
Chicago/Turabian StyleZhongchao Zhao; Jiaojiao Zhang; Dandan Jia; Kai Zhao; Xiao Zhang; Pengpeng Jiang. 2017. "Thermal performance analysis of pool boiling on an enhanced surface modified by the combination of microstructures and wetting properties." Applied Thermal Engineering 117, no. : 417-426.