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Simulation of the optimal heat rejection pressure for transcritical CO

Junlan YANG, Yitai MA, Minxia LI, Hua TIAN

《能源前沿（英文）》 2010年 第4卷 第4期   页码 522-526 doi: 10.1007/s11708-010-0027-8

摘要： In order to optimize and control transcritical CO refrigeration cycle, a mathematical model was developed to simulate the system performance. The simulation results show that a maximum COP exists at the optimal heat rejection pressure not only for throttle valve cycle but also for expander cycle. Also, the optimal heat rejection pressures of the throttle valve cycle are greater than those of the expander cycle under the same condition. In order to further obtain correlation of the optimal heat rejection pressure for transcritical CO expander cycle, it is necessary to analyze the impact degree of compressor efficiency, expander efficiency, gas cooler outlet temperature and evaporation temperature. Based on the simulation results, the values of the optimal heat rejection pressure for the expander cycle were regressed in terms of gas cooler outlet temperature and evaporation temperature at given compressor efficiency and expander efficiency. Finally, two types of polynomial correlations were obtained. One is cubic form, with an average deviation of less than 0.5% and the other is simplified form, with an average deviation of less than 1%. It is, therefore, convenient to use either correlation to simulate the performance of transcritical CO expander cycle.

关键词： transcritical CO2 cycle     optimal heat rejection pressure     simulation     expander    

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Numerical investigation and optimal design of fiber Bragg grating based wind pressure sensor

Xiangjie WANG, Danhui DAN, Rong XIAO, Xingfei YAN

《结构与土木工程前沿（英文）》 2017年 第11卷 第3期   页码 286-292 doi: 10.1007/s11709-017-0415-9

摘要： A wind pressure sensor based on fiber Bragg grating (FBG) for engineering structure was investigated in this paper. We established a transaction model of wind pressure to strain and proposed a method of temperature compensation. By finite element analysis, the basic parameters of the sensor were optimized with the aim of maximum strain under the basic wind pressure proposed in relative design code in China taking geometrical non-linearity into consideration. The result shows that the wind pressure sensor we proposed is well performed and have good sensing properties, which means it is a technically feasible solution.

关键词： wind pressure measurement     wind pressure sensor     fiber Bragg grating     optimal design    

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An investigation into the heat transfer characteristics of spiral wall with internal rib in a supercriticalsliding-pressure operation once-through boiler

TANG Renhu, YIN Fei, WANG Haijun, CHEN Tingkuan

《能源前沿（英文）》 2007年 第1卷 第3期   页码 300-304 doi: 10.1007/s11708-007-0043-5

摘要： Within the pressure range of 9–28 MPa, mass velocity range of 600–1 200 kg/(m · s), and heat flux range of 200–500 kW/m, experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees, a maximum outer diameter of 38.1 mm, and a thickness of 7.5 mm. Based on the experiments, it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical pressure. However, the heat transfer enhancement decreased near the critical pressure. At supercritical pressure, the temperature difference between the wall and the fluid increased near the pseudo-critical temperature, but the increase of wall temperature was less than that of departure from nucleate boiling at sub-critical pressure. When pressure is closer to the critical pressure, the temperature difference between the wall and the fluid increased greatly near the pseudo-critical temperature. Heat transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat flux. Because the rotational flow of the internal groove reduced the effect of natural convection, the internal wall temperature of internally ribbed tube uniformly distributed along the circumference. The maximum internal wall temperature difference of the tube along the circumference was only 10 degrees when the fluid enthalpy exceeded 2 000 J/g. Considering the effect of acute variety of the fluid property on heat transfer, the correlation of heat transfer coefficient on the top of the internally ribbed tube was provided.

关键词： m ·     diameter     critical pressure     sub-critical pressure     maximum    

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Interfacial heat transfer coefficient between metal and die during high pressure die casting process

GUO Zhipeng, XIONG Shoumei, CHO SangHyun, CHOI JeongKil

《机械工程前沿（英文）》 2007年 第2卷 第3期   页码 283-287 doi: 10.1007/s11465-007-0049-z

摘要： The present work focused on the determination of the interfacial heat transfer coefficient (IHTC) between metal and die during the high pressure die casting (HPDC) process. Experiments were carried out on an aluminum alloy, ADC12Z, using step shape casting so-called because of its shape. The IHTC was successfully determined by solving one of the inverse heat problems using the nonlinear estimation method first used by Beck. The calculation results indicated that the IHTC immediately increased after liquid metal was brought into the cavity by the plunger and decreased as the solidification process of the liquid metal proceeded. The liquid metal eventually solidified completely, a condition when the IHTC tended to be stable. Casting thickness played an important role in affecting the IHTC between the metal and die not only in terms of its value but also in terms of its change tendency. Also, under the test conditions, different change tendencies of the metal solid fraction were found between castings with different thicknesses and the die.

关键词： so-called     calculation     inverse     interfacial     aluminum    

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CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

《化学科学与工程前沿（英文）》 2015年 第9卷 第2期   页码 183-193 doi: 10.1007/s11705-015-1510-x

摘要： Shell-and-tube heat exchanger with helical baffles is superior to that with segmental baffles in reducing pressure drop, eliminating dead zone and lowering the risks of vibration of tube bundle. This paper focused on the small-angle helical baffles that have been merely reported in open literature. These baffles are noncontinuous helical baffles with a helix angle of 10° to 30°, and their shapes are 1/4 ellipse, 1/4 sector and 1/3 sector. To assess the integrative performance, /? is employed, and the calculated results show that among the three baffle shapes the heat exchangers with a 1/4 sector helical baffle have the lowest pressure drop. At = 10° and 20°, 1/4 sector helical baffle heat exchangers show the best integrative performance; at = 30°, 1/4 ellipse and 1/4 sector helical baffle heat exchangers perform almost the same. For the study of helix angles, we found that 30° has the best integrative performance at low mass flow rate, almost the same as 20° at high mass flow rate.

关键词： heat transfer     pressure drop     helical baffle     CFD    

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Flow and heat transfer in compact offset strip fin surfaces

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

《能源前沿（英文）》 2008年 第2卷 第3期   页码 291-297 doi: 10.1007/s11708-008-0061-y

摘要： Experimental studies of air-side heat transfer and pressure drop characteristics of offset strip fins and flat tube heat exchangers were performed. A series of tests were conducted for 9 heat exchangers with different fin space, fi

关键词： different     air-side     transfer     pressure     offset    

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Transient analysis of thermoelastic contact problem of disk brakes

Ali BELHOCINE, Mostefa BOUCHETARA

《机械工程前沿（英文）》 2013年 第8卷 第2期   页码 150-159 doi: 10.1007/s11465-013-0266-6

摘要：

The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disk and pads during the braking phase. The simulation strategy is based on computer code ANSYS11. The modeling of transient temperature in the disk is actually used to identify the factor of geometric design of the disk to install the ventilation system in vehicles. The thermal-structural analysis is then used with coupling to determine the deformation established and the Von Mises stresses in the disk, the contact pressure distribution in pads. The results are satisfactory compared to those found in the literature.

关键词： brake disks     heat flux     heat-transfer coefficient     Von Mises stress     contact pressure    

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变频驱动并联水泵变压变流量运行优化调度

李洪斌,张承慧,宋军

《中国工程科学》 2001年 第3卷 第9期   页码 52-57

摘要：

分析了变频驱动并联水泵变压变流量运行优化调度问题的常用建模方法，并比较了各种方法的优劣。 常用的方法是以水泵轴功率作为目标函数，以供水指标和高效区为约束条件。另一种方法是以满足扬程指标时 的实际流量与所需流量之差的二次方作为目标函数，以水泵的高效区作为约束条件。提出了一种新的建模方法， 模型物理意义与实际工况严格相符，具有较高的精度，满足了工程中对水泵切换频率尽量小的要求。仿真结果 表明该方法是有效的。

关键词： 优化调度     有约束非线性规划     水泵调速    

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Optimal design analysis of a tubular heat exchanger network with extended surfaces using multi-objective

Hassan HAJABDOLLAHI, Mohammad SHAFIEY DEHAJ, Babak MASOUMPOUR, Mohammad ATAEIZADEH

《能源前沿（英文）》 2022年 第16卷 第5期   页码 862-875 doi: 10.1007/s11708-022-0839-3

摘要： The present work aims to investigate the influence of extended surfaces (fins) on the multi-objective optimization of a tubular heat exchanger network (THEN). An increase in the heat transfer area using various extended surfaces (fins) to enhance the performance of the heat exchanger was used while considering the effectiveness and total heat transfer area as two objective functions. In addition to the simulation of simple fins, a new set of fins, called constructal fins, was designed based on the constructal theory. Tubular heat exchanger network design parameters were chosen as optimization variables, and optimization results were achieved in such a way as to enhance the effectiveness and decrease the total heat transfer area. The results show the importance of constructal fins in improving the objective functions of heat exchangers. For instance, the simple fins case enhances the effectiveness by up to 5.3% compared to that without fins (usual heat exchanger) while using constructal fins, in addition to the 7% increment of effectiveness, reduces the total heat transfer area by 9.47%. In order to optimize the heat exchanger, the heat transfer rate and cold fluid temperature must increase, and at the same time, the hot exiting fluid temperature should decrease at the same constant total heat transfer area, which is higher in the constructal fins case. Finally, optimized design variables were studied for different cases, and the effects of various fins were reported.

关键词： constructal theory     extended surface     effectiveness     total heat transfer area     multi-objective optimization    

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Entropy flow, entropy generation, exergy flux, and optimal absorbing temperature in radiative transfer

Zeshao CHEN, Songping MO, Peng HU, Shouli JIANG, Gang WANG, Xiaofang CHENG,

《能源前沿（英文）》 2010年 第4卷 第3期   页码 301-305 doi: 10.1007/s11708-010-0006-0

摘要： Taking nonequilibrium radiative heat transfer between two surfaces as an example, the nonequilibrium thermodynamics of radiation is studied and discussed. The formulas of entropy flow, entropy generation, exergy flux, and optimal temperature of absorbing surface for maximum exergy output are derived. The result is a contribution to the thermodynamic analysis and optimization of solar energy utilization and can be applied in more complex radiative heat transfer cases.

关键词： radiative heat transfer     entropy generation     exergy     thermodynamics    

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Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

《能源前沿（英文）》 2010年 第4卷 第4期   页码 546-552 doi: 10.1007/s11708-010-0116-8

摘要： Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10 mm, coil diameter of 300 mm, and pitch of 50 mm. The experiments were conducted over a wide Reynolds number range of 40000 to 500000. Both constant-property flows at normal pressure and variable-property flows at supercritical pressure were investigated. The contribution of secondary flow in the helical coil to heat transfer was gradually suppressed with increasing Reynolds number. Hence, heat transfer coefficients of the helical tube were close to those of the straight tube under the same flow conditions when the Reynolds number is large enough. Based on the experimental data, heat transfer correlations for both incompressible flows and supercritical fluid flows through helical coils were proposed.

关键词： convective heat transfer     helical coils     high Reynolds number     supercritical pressure     variable property    

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Separation of

Wei Hou, Qingjun Zhang, Aiwu Zeng

《化学科学与工程前沿（英文）》 2021年 第15卷 第5期   页码 1169-1184 doi: 10.1007/s11705-020-2018-6

摘要： In this study, vapor recompression and heat integration assisted distillation arrangements with either the low or high pressure in the reflux drum are proposed to reduce and/or eliminate the application of the costly refrigerant for the separation of -heptane and isobutanol mixture. The high-pressure arrangement with vapor recompression and heat integration is the most attractive among these four intensified configurations since it can reduce total annual cost by 18.10%, CO emissions by 75.01% based on natural gas (78.78% based on heavy oil fuel), and second-law efficiency by 61.20% compared to a conventional refrigerated distillation system. Furthermore, exergy destruction in each component is calculated for the heat integration configurations and is shown in pie diagrams. The results demonstrate that the high-pressure configuration presents unique advantages in terms of thermodynamic efficiency compared to the low-pressure case. In addition, dynamic control investigation is performed for the economically efficient arrangement and good product compositions are well controlled through a dual-point temperature control strategy with almost negligible product offsets and quick process responses when addressing 20% step changes in production rate and feed composition. Note that there are no composition measurement loops in our developed control schemes.

关键词： n-heptane/isobutanol     vapor recompression     heat integration     low and/or high-pressure options    

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Optimal ratio of bend channel in centrifugal compressor

WEN Suping, HU Xiaowen, LI Tingbin, ZHANG Yong, WANG Jun

《能源前沿（英文）》 2008年 第2卷 第4期   页码 381-385 doi: 10.1007/s11708-008-0084-4

摘要： A numerical investigation on the flow in a bend channel by coupling the impeller with the vaneless diffuser in a centrifugal compressor with different ratios (bend radius to bend channel width ) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in ratio significantly affects the flow angle of the bend channel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.

关键词： specific compressor     different     centrifugal compressor     pressure     impeller    

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Heat transfer and fluid flow analysis of an artificially roughened solar air heater: a CFD based investigation

Anil Singh YADAV,J. L. BHAGORIA

《能源前沿（英文）》 2014年 第8卷 第2期   页码 201-211 doi: 10.1007/s11708-014-0297-7

摘要： In this paper, the effect of rib (circular sectioned) spacing on average Nusselt number and friction factor in an artificially roughened solar air heater (duct aspect ratio, AR= 5:1) is studied by adopting the computational fluid dynamics (CFD) approach. Numerical solutions are obtained using commercial software ANSYS FLUENT v12.1. The computations based on the finite volume method with the semi-implicit method for pressure-linked equations (SIMPLE) algorithm have been conducted. Circular sectioned transverse ribs are applied at the underside of the top of the duct, i.e., on the absorber plate. The rib-height-to-hydraulic diameter ratio ( ) is 0.042. The rib-pitch-to-rib-height ( ) ratios studied are 7.14, 10.71, 14.29 and 17.86. For each rib spacing simulations are executed at six different relevant Reynolds numbers from 3800 to 18000. The thermo-hydraulic performance parameter for = 10.71 is found to be the best for the investigated range of parameters at a Reynolds number of 15000.

关键词： heat transfer     pressure drop     thermo-hydraulic performance parameter    

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Performance evaluation of an improved biomass-fired cogeneration system simultaneously using extraction steam, cooling water, and feedwater for heating

《能源前沿（英文）》 2022年 第16卷 第2期   页码 321-335 doi: 10.1007/s11708-021-0741-4

摘要： An advanced cogeneration system based on biomass direct combustion was developed and its feasibility was demonstrated. In place of the traditional single heat source (extraction steam), the extraction steam from the turbine, the cooling water from the plant condenser, and the low-pressure feedwater from the feedwater preheating system were collectively used for producing district heat in the new scheme. Hence, a remarkable energy-saving effect could be achieved, improving the overall efficiency of the cogeneration system. The thermodynamic and economic performance of the novel system was examined when taking a 35 MW biomass-fired cogeneration unit for case study. Once the biomass feed rate and net thermal production remain constant, an increment of 1.36 MW can be expected in the net electric production, because of the recommended upgrading. Consequently, the total system efficiency and effective electrical efficiency augmented by 1.23 and 1.50 percentage points. The inherent mechanism of performance enhancement was investigated from the energy and exergy aspects. The economic study indicates that the dynamic payback period of the retrofitting project is merely 1.20 years, with a net present value of 5796.0 k$. In conclusion, the proposed concept is validated to be advantageous and profitable.

关键词： biomass-fired cogeneration     district heat production system     absorption heat pump     extraction steam     cooling water     low-pressure feedwater    

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标题 作者 时间 类型 操作

Simulation of the optimal heat rejection pressure for transcritical CO

Junlan YANG, Yitai MA, Minxia LI, Hua TIAN

期刊论文

Numerical investigation and optimal design of fiber Bragg grating based wind pressure sensor

Xiangjie WANG, Danhui DAN, Rong XIAO, Xingfei YAN

期刊论文

An investigation into the heat transfer characteristics of spiral wall with internal rib in a supercriticalsliding-pressure operation once-through boiler

TANG Renhu, YIN Fei, WANG Haijun, CHEN Tingkuan

期刊论文

Interfacial heat transfer coefficient between metal and die during high pressure die casting process

GUO Zhipeng, XIONG Shoumei, CHO SangHyun, CHOI JeongKil

期刊论文

CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

期刊论文

Flow and heat transfer in compact offset strip fin surfaces

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

期刊论文

Transient analysis of thermoelastic contact problem of disk brakes

Ali BELHOCINE, Mostefa BOUCHETARA

期刊论文

变频驱动并联水泵变压变流量运行优化调度

李洪斌,张承慧,宋军

期刊论文

Optimal design analysis of a tubular heat exchanger network with extended surfaces using multi-objective

Hassan HAJABDOLLAHI, Mohammad SHAFIEY DEHAJ, Babak MASOUMPOUR, Mohammad ATAEIZADEH

期刊论文

Entropy flow, entropy generation, exergy flux, and optimal absorbing temperature in radiative transfer

Zeshao CHEN, Songping MO, Peng HU, Shouli JIANG, Gang WANG, Xiaofang CHENG,

期刊论文

Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

期刊论文

Separation of

Wei Hou, Qingjun Zhang, Aiwu Zeng

期刊论文

Optimal ratio of bend channel in centrifugal compressor

WEN Suping, HU Xiaowen, LI Tingbin, ZHANG Yong, WANG Jun

期刊论文

Heat transfer and fluid flow analysis of an artificially roughened solar air heater: a CFD based investigation

Anil Singh YADAV,J. L. BHAGORIA

期刊论文

Performance evaluation of an improved biomass-fired cogeneration system simultaneously using extraction steam, cooling water, and feedwater for heating

期刊论文