JPS57175886A - Heat exchanger - Google Patents

Abstract

PURPOSE:To make a heat exchanger smaller in size and to improve thermal efficiency by providing a heat recovery tube which is encompassed by a gas-permeable solid provided in the exhaust gas passage of a heating furnace. The heat recovery tube through which fluid to be heated flows is located on the gas-entering side of the gas-permeable solid and is filled with grains of ceramics or the like. CONSTITUTION:Exhaust gas flows toward the direction indicated by the arrows inside a passage 1 and fluid to be heated flows into and out of the heat recovery tube 3 as indicated by the arrow 5, 7. During such process, the exhaust gas, as it passes through the gas-permeable solid 2, causes temperature on the gas-entering side of the gas-permeable solid 2 to rise very high so that radiation heat energy is emitted out of the gas-permeable solid 2 toward the heat recovery tube 3. Heat energy emitted into the heat recovery tube 3 can be transferred directly or through grains 4 to fluid to be heated which flows through the heat recovery tube. The fluid is caused to flow turbulently or meanderingly by the grains 4 so that thermal efficiency can further be promoted. By such features, improvements can be made in simplification of structure, making the unit smaller and in high thermal efficiency.