This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type....This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.展开更多
The Hypersonic Precooled Combined Cycle Engine(HPCCE), which introduces precooler into traditional hypersonic engine, is regarded as the most promising propulsion system for realizing a single-stage-to-orbit vehicle. ...The Hypersonic Precooled Combined Cycle Engine(HPCCE), which introduces precooler into traditional hypersonic engine, is regarded as the most promising propulsion system for realizing a single-stage-to-orbit vehicle. The unique demands lead to the application of the compact heat exchangers, which can realize high thrust-to-weight ratio, sufficient specific impulse and high compression ratio. However, it is challenging to accurately manufacture the compact heat exchanger due to its extremely high heat dissipation capacity, remarkable compactness, superior adaptability and harsh operating condition. This review summarizes the precooling schemes of combined cycle propulsions and describes the demands and key issues in the fabrication of a compact heat exchanger for HPCCE. The investigation focuses on the application of various micromanufacturing methods of heat exchangers constructed from tubes of less than 1 mm in diameter and microchannels of less than 200 micrometers. Various micromanufacturing processes, which include microforming, micromachining, stereolithography, chemical etching, 3 D printing, joining and other advanced microfabricating processes, were reviewed. In addition, the technologies are compared in terms of dimensional tolerance, material compatibility, and process applicability. Furthermore, the boundaries of the micromanufacturing constraints are specified as references for the design of compact heat exchangers. Ultimately, the technological difficulties and development trends are discussed for the fabrication of compact heat exchangers for HPCCE.展开更多
为优化紧凑高效换热器的结构,对不同截面形状的流道和不同流道布置形式的换热器进行强度和可靠性分析。针对半圆形横截面之字形通道、半圆形横截面直通道、矩形横截面之字形通道和矩形横截面直通道等4种横截面形状流道及其布置形式,开...为优化紧凑高效换热器的结构,对不同截面形状的流道和不同流道布置形式的换热器进行强度和可靠性分析。针对半圆形横截面之字形通道、半圆形横截面直通道、矩形横截面之字形通道和矩形横截面直通道等4种横截面形状流道及其布置形式,开展换热器芯体静强度和可靠性分析,并对比这4种模型的可靠性。研究结果表明:4种形式的换热器芯体的静强度均满足美国机械工程师协会(American Society of Mechanical Engineers, ASME)评定要求;半圆形横截面直通道换热器的可靠度最高。研究成果可供换热器冷热流道布置和换热器结构优化参考。展开更多
文摘This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.
基金the funding support to this research from the National Natural Science Foundation of China (Nos. 51635005, 51975031 and 51605018)Defense Industrial Technology Development Program of China (No.JCKY2018601C207)。
文摘The Hypersonic Precooled Combined Cycle Engine(HPCCE), which introduces precooler into traditional hypersonic engine, is regarded as the most promising propulsion system for realizing a single-stage-to-orbit vehicle. The unique demands lead to the application of the compact heat exchangers, which can realize high thrust-to-weight ratio, sufficient specific impulse and high compression ratio. However, it is challenging to accurately manufacture the compact heat exchanger due to its extremely high heat dissipation capacity, remarkable compactness, superior adaptability and harsh operating condition. This review summarizes the precooling schemes of combined cycle propulsions and describes the demands and key issues in the fabrication of a compact heat exchanger for HPCCE. The investigation focuses on the application of various micromanufacturing methods of heat exchangers constructed from tubes of less than 1 mm in diameter and microchannels of less than 200 micrometers. Various micromanufacturing processes, which include microforming, micromachining, stereolithography, chemical etching, 3 D printing, joining and other advanced microfabricating processes, were reviewed. In addition, the technologies are compared in terms of dimensional tolerance, material compatibility, and process applicability. Furthermore, the boundaries of the micromanufacturing constraints are specified as references for the design of compact heat exchangers. Ultimately, the technological difficulties and development trends are discussed for the fabrication of compact heat exchangers for HPCCE.
文摘为优化紧凑高效换热器的结构,对不同截面形状的流道和不同流道布置形式的换热器进行强度和可靠性分析。针对半圆形横截面之字形通道、半圆形横截面直通道、矩形横截面之字形通道和矩形横截面直通道等4种横截面形状流道及其布置形式,开展换热器芯体静强度和可靠性分析,并对比这4种模型的可靠性。研究结果表明:4种形式的换热器芯体的静强度均满足美国机械工程师协会(American Society of Mechanical Engineers, ASME)评定要求;半圆形横截面直通道换热器的可靠度最高。研究成果可供换热器冷热流道布置和换热器结构优化参考。
