Research and Development of High Temperature and High Performance Plate-fin Compact Heat Exchanger with the Purpose of Reducing

One of the most serious problems in the development of plate-fin compact heat exchangers at temperatures above 600°C for advanced fuel cell or gas turbine plants，is mainly that brazed parts or the part of cover-plate connected to pipings is not strong enough due to thermal stress for practical use.In order to solve this problem，this study aims to make such a specific proposal as to install twisted tapes in the heat exchanger channels appropriate to decrease thermal stresses by giving uniform heated gas outlet temperature.In1984，a study of flow and heat transfer performances in s square heated channel installed with various kinds of twisted tape as experimentally made below 300°C a plate-fquare heated channel installed with various kinds of twisted tape as experimentally made below 300°C and a plate-fquare heated channel installed with various kinds of twisted tape as experimentally made below problemIn1985，first，by use of two kinds of channels of square and rectangular section of aspect ratio2，flow and heat transfer performances up to 500°C were experimentally obtained with the tapes with various width-pitch ratio and coated by black paint.Secondly，numerical calculations were made to obtain the optimum pitch ratio distribution of tapes installed in the channels of heat exchanger.By use of the twist-pitch distribution of tapes well approximating to the optomum one，experiments on temperature fields were made by use of an heat exchanger.A fairly good agreement was obtained between the experimental and predicted values。Thirdly，the other heat exchanger of brazed construction was made and tested.The numerical analyses of thermal stress were also made to make a comparison with the experimental results.It was shown by the experiment and the prediction that the maximum stress was found near the piping connecting part of the coverplate.Thus important and essential information for elevating the available temperature limit of the plate-fin compact heat exchanger was obtained

One of the most serious problems in the development of plate-fin compact heat exchangers at temperatures above 600゜C for advanced fuel cell or gas turbine plants, is mainly that brazed parts or the part of cover-plate connected to pipings is not strong enough due to thermal stress for practical use. In order to solve this problem, this study aims to make such a specific proposal as to install twisted tapes in the heat exchanger channels appropriate to decrease thermal stresses by giving uniform heated gas outlet temperature.In 1984, a study of flow and heat transfer performances in s square heated channel installed with various kinds of twisted tape was experimentally made below 300゜C and a plate-fin compact heat exchanger and its system was designed and the performance was tested. In 1985, first, by use of two kinds of channels of square and rectangular section of aspect ratio 2, flow and heat transfer performances up to 500゜C were experimentally obtained with the tapes with various width-pitch ratio and coated by black paint. Secondly, numerical calculations were made to obtain the optimum pitch ratio distribution of tapes installed in the channels of heat exchanger. By use of the twist-pitch distribution of tapes well approximating to the optomum one,experiments on temperature fields were made by use of an heat exchanger. A fairly good agreement was obtained between the experimental and predicted values. Thirdly, the other heat exchanger of brazed construction was made and tested. The numerical analyses of thermal stress were also made to make a comparison with the experimental results. It was shown by the experiment and the prediction that the maximum stress was found near the piping connecting part of the coverplate. Thus important and essential information for elevating the available temperature limit of the plate-fin compact heat exchanger was obtained