Improvement of high temperature heat exchanger efficiency by inserted porous material, (II) Preheating, single tube type shell and tube heat exchanger.

Abstract

In the 1st paper, a possibility of advancing the high temperature heat exchanger efficiency by inserting a porous metal (wire net layers) in the heat exchanger to augment the radiative heat transfer characteristics is shown. It is also shown that the effectiveness of the wire net layers insertion is not affected even when the shell wall of the heat exchanger is cooled to keep out of becoming high temperature, which is favorable for the structural designing of the shell. Thus, in this paper, an advanced type heat exchanger in which shell wall is cooled by the secondary gas, which is pre-heated, is proposed and its performance is experimentally investigated. In the experiment a heat exchanging apparatus is used in which wire net layers are inserted around a single primary-gas-flowing tube, and the shell wall is cooled by the secondary gas flowing outside of it. It is found that the effect of the wire net layers insertion is prominent when the primary gas temperature is high; the heat exchanger efficiency is improved by 18% at T1,in= 1,200K, G1=0.0083kg/s even though the heat transfer area of the tube is as small as 1/2.5 of that of the pre-heating section.