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| 1 | Equivalent thermal resistance minimization for a circular disc heat sink with reverting microchannels based on constructal theory and entransy theory显示文摘Thermal designs for microchannel heat sinks with laminar flow are conducted numerically by combining constructal theory and entransy theory. Three types of 3-D circular disc heat sink models, i.e. without collection microchannels, with center collection microchannels, and with edge collection microchannels, are established respectively. Compared with the entransy equivalent thermal resistances of circular disc heat sink without collection microchannels and circular disc heat sink with edge collection microchannels, that of circular disc heat sink with center collection microchannels is the minimum, so the overall heat transfer performance of circular disc heat sink with center collection microchannels has obvious advantages. Furthermore, the effects of microchannel branch number on maximum thermal resistance and entransy equivalent thermal resistance of circular disc heat sink with center collection microchannels are investigated under different mass flow rates and heat fluxes. With the mass flow rate increasing, both the maximum thermal resistances and the entransy equivalent thermal resistances of heat sinks with respective fixed microchannel branch number all gradually decrease. With the heat flux increasing, the maximum thermal resistances and the entransy equivalent thermal resistances of heat sinks with respective fixed microchannel branch number remain almost unchanged. With the same mass flow rate and heat flux, the larger the microchannel branch number, the smaller the maximum thermal resistance. While the optimal microchannel branch number corresponding to minimum entransy equivalent thermal resistance is 6. | WANG Liang XIE ZhiHui CHEN LinGen WANG Rong FENG HuiJun | 2021 | Science China(Technological Sciences)2021，64，1： | 11 |
| 2 | Entransy analyses of the thermodynamic cycle in a turbojet engine显示文摘The analysis and the design of turbojet engines are of great importance to the improvement of the system performance.Many researchers focus on these topics,and many important and interesting results have been obtained.In this paper,the thermodynamic cycle in a turbojet engine is analyzed with the entransy theory and the T-Q diagram.The ideal thermodynamic cycle in which there is no inner irreversibility is analyzed,as well as the influences from some inner irreversible factors,such as the heat transfer process,the change of the component of the working fluid and the viscosity of the working fluid.For the discussed cases,it is shown that larger entransy loss rate always results in larger output power,while smaller entropy generation rate does not always.The corresponding T-Q diagrams are also presented,with which the change tendencies of the entransy loss rate and the output power can be shown very intuitively.It is shown that the entransy theory is applicable for analyzing the inner irreversible thermodynamic cycles discussed in this paper.Compared with the concept of entropy generation,the concept of entransy loss and the corresponding T-Q diagram are more suitable for describing the change of the output power of the analyzed turbojet engine no matter if the inner irreversible factors are considered. | CHENG XueTao LIANG XinGang | 2017 | Science China(Technological Sciences)2017，60，8： | 7 |
| 3 | Water dissipation mechanism of residential and office buildings in urban areas显示文摘Indoor humidity directly impacts the health of indoor populations. In arid and semi-arid cities, the buildings indoor humidity is typically higher than outdoors, and the presence of water vapor results from water dissipation inside the buildings. Few studies have explored indoor humidity features and vapor distribution or evaluated water dissipation inside buildings. This study examined temperature and relative humidity(RH) changes in typical residential and office buildings. The results indicate a relatively stable temperature with vary range of ±1°C and a fluctuation RH trend which is similarly to that of water use. We proposed the concept of building water dissipation to describe the transformation of liquid water into gaseous water during water consumption and to develop a building water dissipation model that involves two main parameters: indoor population and total floor area. The simulated values were verified by measuring water consumption and water drainage, and the resulting simulation errors were lower for residential than for office buildings. The results indicate that bathroom vapor accounts for 70% of water dissipation in residential buildings. We conclude that indoor humidity was largely a result of water dissipation indoors, and building water dissipation should be considered in urban hydrological cycles. | ZHOU JinJun LIU JiaHong WANG Hao WANG ZhongJing MEI Chao | 2018 | Science China(Technological Sciences)2018，61，7： | 3 |
| 4 | 基于广义传热定律的斯特林循环熵产分析和■分析显示文摘基于广义传热定律,本文将■理论和熵产最小化理论应用于有限热容热源下的斯特林循环的优化分析,以系统输出功和热效率为分析对象,讨论了■损失率、功引起的■变化率、■耗散率、■损失系数、熵产率、熵产数和改进熵产数等参数在优化分析中的适用性.本文主要讨论了3种不同的工况.研究表明,在这3种不同的工况下,■损失率和功引起的■变化率始终随着输出功率的增加而增加,■损失系数也一直随热效率增大而增大;然而,■耗散率的增大或熵产率的减小并不总是使得输出功率增大,同时,熵产数和改进熵产数也并不总随热效率的增大而减小.可见,对本文讨论的3种工况而言,■损失率、功引起的■变化率以及■损失系数这3个概念是适用的,其他参数则并不总是适用.基于上述分析结果,本文还对关于■理论的争议进行了简要的讨论,分析了某些负面评论存在的主要问题,如篡改原文、逻辑不一致、简单重复学术观点、重新命名关键概念甚至人身攻击等.这些■理论的负面评论并不属于真正的学术讨论,需要加以注意;本文的研究结果在一定程度上也可作为对部分负面评论的回应. | 吴艳秋 蔡黎 伍习丽 | 2019 | 中国科学:技术科学2019，49，6： | 3 |
| 5 | Role of viscous heating in entransy analyses of convective heat transfer显示文摘The entransy theory is widely used and found to be effective in thermal analyses and optimizations.Some researchers considered the entransy variation due to viscous heating as part of entransy dissipation and analyzed convective heat transfer based on the differential relationship between entropy and entransy.However,it has been pointed out that the derivation of the differential relationship between entropy and entransy is incorrect.In this paper,the convective heat transfer processes with viscous heating is reconsidered and analyzed from the viewpoint of the energy conservation and the entransy balance equation.It is shown that the influence of the viscous heating is equivalent to that of an inner heat source.Therefore,the contribution of viscous heating to system entransy should not be treated as part of entransy dissipation,but entransy flow into the system.Two-stream parallel and counter flow heat exchangers with viscous heating and a thermal insulation transportation problem of heavy oil are taken as examples to verify the theoretical analyses intuitively.In the examples,the numerical results show that the entransy dissipation rates could be negative when the influence of the viscous heating on the system entransy is treated as part of the entransy dissipation.This is obviously unreasonable.Meanwhile,when the entransy contribution from the viscous heating to the system entransy is treated as entransy flow into the system,it is shown that the entransy dissipation rate is always positive,and the heat transfer processes can be well explained with the entransy theory. | CHENG XueTao WANG XiangYu LIANG XinGang | 2020 | Science China(Technological Sciences)2020，63，10： | 2 |
| 6 | 换热器优化中均分原则的适用性分析显示文摘在许多物理过程的优化设计中,其优化结果反映为某些物理量或者函数的均匀分布,即相应的均分原则.针对两股流和三股流换热器的优化分析,讨论了热力学力场均匀性原则、ΔT/T场均匀性原则和温差场均匀性原则三项均分原则的适用性.研究表明,当换热量给定时,前两项原则既不能给出最小的换热器熵产率,又不能给出最高的换热器效能;而当换热器实现最佳传热性能时,前两项原则得不到满足.对于温差场均匀性原则,不论冷热流体间的传热系数是否为常数,均可基于理论对其进行数学证明.当冷热流体温差场完全均匀时,换热器的耗散热阻达到最小值.可见,温差场均匀性原则可以给出换热器的最佳传热性能.进一步,本文给出了简单的案例,直观地验证了上述结论.理论与案例分析的结果进一步表明,热力学力场均匀性原则和ΔT/T场均匀性原则都是基于熵产的概念得到的,而熵产从做功能力损失的角度衡量不可逆性,导致这两项原则与传热优化的目的不一致,而且其推导过程中所采用的传热定律也不符合实际的传热过程;而用于证明温差场均匀性原则的(火积)耗散则从传热能力损失的角度衡量传热过程的不可逆性,其优化目标与传热优化目标则是一致的.这就是前两项原则不适用于换热器优化分析而温差场均匀性原则适用的根本原因. | 程雪涛 张龙飞 梁新刚 | 2021 | 中国科学:技术科学2021，51，10： | 0 |
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