OCR Text |
Show 4 Radiant burner. Two burner types are currently under evaluation: impingement (shown in Figure 1) and a high-intensity ported tile. The impingement burner incorporates a radiant ceramic surface against which premixed air-fuel jets are directed by a row of nozzles. The ported tile, developed by Columbia Gas System Service Corporation, also employs a ceramic radiant surface, but the gas flow path is through ports cut directly in the tile. These burner types were selected largely on the basis of surveys of radiant burner technology by Alzeta and Acurex Corporations (2, 3). Reflux boiler. Downstream of the burner is the primary heat exchanger, a finned reflux boiler. The boiler consists of a horizontal cupronickel pipe with square copper fins furnace-brazed to the exterior. This device transfers heat from the combustion products to the desorption apparatus within the heat pump. The boiler working fluid (water) moves by natural circulation, with vapor flow upward and condensate return by gravity. Recuperator. After passing around the boiler, the combustion products enter the crossflow recuperator, a 304-stainless-steel plate-fin heat exchanger manufactured by CSM Systems. Combustion products flow horizontally through finned rectangular channels, while premixed air and fuel flow vertically through identical adjacent channels. The overall dimensions and fin density in the recuperator were chosen on the basis of calculations performed with a software package entitled "Compact Heat Exchanger Design", authored by W. M. Kays (4). Design criteria. Table 1 summarizes the criteria which governed selection of major components. The nominal fi.ing rate per module of 20,300 Btu/hr (6 kw) corresponds to a rate of 40,600 Btu/hr (12 kw) for a residence. This rate is modest compared to that of typical home furnaces because the balance of the heat input is "pumped" from the outside air. |