GB667167A - Improvements in heat exchangers - Google Patents

Abstract

667,167. Regenerators heating air for combustion.- SOC. ANON. DE COMMENTRY-FOURCHAMBAULT ET DECAZEVILLE. July 7, 1948 [Feb. 5, 1948], No. 18305/48. Class 64(i) In apparatus for the exchange of heat between gaseous fluids, e.g. metal airheaters or cowpers for blast furnaces heated by gases obtained by combustion of the furnace gas, hot gas is introduced intermediately of an inlet 11 and outlet 13 for the heated gas, situated at the respective ends of a wall through which heat exchange takes place, so that the temperature of the wall between the hot gas inlet part and the heated gas outlet end is kept uniform. In a heatexchanger, Fig. 4, a gas entering at 11 and passing out at 13 is heated by gases, from a combustion chamber 6 and burner 7 for fuel such as pulverized coal, injected at successive points 1, 2, 3 &c.. between baffles 14 by means of distributers D1 D2, D3 etc. which are thermostatically controlled to maintain the heat-exchange walls in the vicinity of the injection points at a uniform temperature as near as possible to the maximum temperature which the material, e.g. metal, of the wall can withstand. The temperature of the gases injected at the point 1 is controlled by the addition of a cold gas, e.g. air, smoke or inert gases from a pump 19 adjusted by a valve 18 controlled by a thermal element on the heat-exchange surface near the point 1. On heavy loads, the later distributers, e.g. Dp-1, may not be used, but on light load the uniform temperature zone is extended since a servo-motor controlled by the last distributer Dp-1, or a thermostat at p' then causes-a decrease in the quantity of combustion gas supplied to the first point 1 and a corresponding increase in supply to the later distributers. In order to avoid the addition of cold gases to the heating fluid, the latter may be pre-cooled in a small heat-exchanger. Each distributer, Fig. 6 (not shown), consists of a slide valve controlling communication between an inlet, e.g. from a previous distributer, and two outlets, i.e. a port connected to the injection point and a port to the next distributer. The slide is actuated by an oil pressure operated piston, the oil supply to which is controlled by a thermostat subject to the temperature of the heatexchange wall at the injection point. As shown in Fig. 7 the uniform temperature is obtained by the heating gases entering at 26 and flowing first of all generally in the same direction as the heated fluid, then re-entering at 29 to flow generally in counter-flow to the fluid to be heated, which enters at 32 and leaves at 36. In a modification of this arrangement, Fig. 9 (not shown), it is the heated fluid which flows in two different directions in separate parts of the apparatus. Compression of either gas flowing through the heatexchanger may be obtained from a gas turbine actuated by the heating fluid issuing from the exchanger.