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A Modified Entropy Generation Number for heat exchanger.

Journal of Thermal Science 1996年第4期5卷 257-263页

作者： Z. M. Xu S. R. Yang Z. Q. Chen Department of Power Engineering Northeast China Institute of Electric Power Engineering Jilin City China Energy and Power Machinery Engineering Institute Xi’an Jiaotong University Xi’an China

This paper demonstrates the difference between the entropy generation number method proposed by Bejan and the method of entropy generation per unit amount of heat transferred in analyzing the thermodynamic performance of heat exchanger., points out the reason for leading to the above difference.A modified entropy generation number for evaluating the irreversibility of heat exchanger. is proposed which is in consistent with the entropy generation per unit amount of heat transferred in entropy generation analysis. The entropy generated by friction is also investigated. Results show that when the entropy generated by friction in heat exchanger. is taken into account, there is a minimum total entropy generation number while the NTU and the ratio of heat capacity rates vary. The existence of this minimum is the prerequisite of heat exchanger.optindzation.

关键词： entropy generation heat exchanger.

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Process Study and Exergy Analysis of a Novel Air Separation Process Cooled by LNG Cold Energy

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Journal of Thermal Science 2014年第1期23卷 77-84页

作者： XU Wendong DUAN Jiao MAO Wenjun Key Laboratory of Enhanced heat Transfer & Energy Conservation of the Ministry of Education School of Chemistry and Chemical EngineeringSouth China University of Technology Zhongshan ling niao Gas Co.Ltd.

In order to resolve the problems of the current air separation process such as the complex process, cumbersome operation and high operating costs, a novel air separation process cooled by LNG cold energy is proposed in this paper, which is based on high-efficiency heat exchanger.network and chemical packing separation technology. The operating temperature range of LNG cold energy is widened from 133K-203K to l13K-283K by high- efficiency heat exchanger.network and air separation pressure is declined from 0.5MPa to about 0.35MPa due to packing separation technology, thereby greatly improve the energy efficiency. Both the traditional and novel air separation processes are simulated with air handling capacity of 20t＇h-1. Comparing with the traditional process, the LNG consumption is reduced by 44.2%, power consumption decrease is 211.5 kWh per hour, which means the annual benefit will be up to 1.218 million CNY. And the exergy efficiency is also improved by 42.5%.

关键词： LNGs air separation cold energy exergy analysis heat exchanger.

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Refrigerant Distribution Characteristics in Vertical Header of Flat-Tube heat exchanger.without Internal Protrusion

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Journal of Energy and Power Engineering 2017年第10期11卷 655-664页

作者： Kazuhiro Endoh Research & Development Group Hitachi Ltd. Hitachinaka lbaraki 312-0034. Japan

A heat exchanger.that arranges flat tubes horizontally has a vertical header that distributes the refrigerant to each tube. When the heat exchanger.works as an evaporator, differences in flow conditions at each branch, such as the ratio and distribution of vapor and liquid, due to the differences in densities and momentums of vapor and liquid in the two-phase flow make equal distribution difficult. This paper describes the distribution characteristics of a four-branch header that has a rectangular cross-section without the internal protrusion of flat tubes in the case of the inflow of the refrigerant R32 from the bottom of the header by using an equipment that can estimate the distribution ratio of the liquid and vapor phase to each branch. This paper also discusses the distribution characteristics on the basis of the flow visualization in the header. The flow visualization shows that a liquid level that contains vapor phase exists in the header and affects the distribution greatly.

关键词： Refrigerant distribution vapor-liquid two-phase flow header flat tube heat exchanger.

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