Heat exchanger integrated stack

Costamagna P., Honegger K., 1998. Modeling of solid oxide heat exchanger integrated stacks and simulation at high fuel utilization. Journal of the Electrochemical Society 145,3995 4007. 

A self-supporting SOFC-based power plant system, HEXIS (Heat Exchanger Integrated Stack), using circular planar elements has been developed by the Sulzer company in Switzerland for natural gas as a fuel and a power of up to 7 kW [26]. Field tests have started in summer 1997 commercialization is planned for the year 2002. The development goal is the construction of small-size systems in the power range of 1 - 200 kW. 

A different type of SOFC design is under development by Hexis [9]. The HEXIS (heat exchanger integrated stack) stack concept can be used for small co-generation plants. The metallic intercoimect in this case serves as a heat exchanger as well as a bipolar plate. 

Costamagna P., Honneger K., Modeling of Solid Oxide Heat Exchanger Integrated Stacks and Simulation at High Fuel Utilization, Journal of Electrochemical Society, Vol. 145, No.l 1, pp. 3995-4007, 1998. 

Recently, the Swiss company Sulzer Hexis AG has developed the concept of an SOFC for small-scale domestic application to provide heating on demand and to cover peak power requirements. This so-called Hexis (Heat Exchanger Integrated Stack) cell consists of circular zirconia electrolyte disks of about 12 cm diameter that carry the anode and cathode (Figure 7.38). The individual cells are... 

Figure 7.38 Solid oxide fuel cell Hexis (Heat Exchanger Integrated Stack) (Schuler, 2007) Reprinted with permission from Schweizerischer Verein des Cas- und Wasserfachs.

A chip-type micro reactor array comprises parallel mixer units composed of inverse mixing tees, each followed by a micro channel that it is surrounded by heat exchange micro channels (so called channel-by-channel approach similar to the tube-in-tube concept). Such an integrated device was developed as a stack of microstructured plates made of a special glass, termed Foturan (Figure 4.26). The integrated device was attached to PTFE tubes of various lengths. 

Tonkovich and coworkers [42—47] used packed bed microreactors for the production of hydrogen. The authors constructed a reactor consisting of stacked stainless steel plates for the partial oxidation of methane [42]. The microchannels (which were 254 pm wide, 1500 pm deep, and 35 mm long) were filled with mesoporous silica that was impregnated with rhodium. The reactor plates were sandwiched between two integrated heat exchanger plates. 

Chem. Descrip. Methyl phenyl silicone resin in xylene Uses Silicone for use in heat-resist, coatings for appliances, engines, mufflers, furnaces, stacks, heat exchangers food-contact coatings Features Dries soft, flexible, and tack-free at R.T. gains solv. resist, at 260 C, maintains flexibility, film integrity beyond 650 C Regulatory FDA 21 CFR 175.300... 

The plane electrodes are separated by isolating spacers, which may lead to the formation of parallel flow channels. In any case, the electrodes are plane sheets which can be replaced and thus made out of any plain material, e.g. nickel, lead, glassy carbon or graphite. Recent technolo cal developments made at the Institute of Microtechniques, Mainz [6, 7], have led to the construction of versatile microchannel electrochemical reactors. Indeed, the pressure can be elevated to up to 35 bar and the electrodes can be stacked in order to increase the overall electrode area. Moreover, polymer electrolyte membranes can be inserted, separating anodic and cathodic compartments if necessary, and finally heat exchangers may be integrated. 

SOFC systems can be designed to include a heat recovery component such as an adsorption chiller heater for CHP applications [72-76]. An example is a small (1-lOkW) methane-fueled residential CHP SOFC system that integrates CGR, AGR, and internal reforming [73]. The system consists of a fuel-cell stack, steam prereformer, various fluid delivery devices (blowers, ejectors, compressor, and water pump), heat exchangers, and catalytic combustor and power conditioning device along with a heat recovery component. Based on certain system parameters (50active area, nominal cell temperature of 800 °G, current density of 0.57 A cm , power density of0.40-0.43 Wcm , S/G ratio of 2.0, SOFC... 

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