| OCR Text |
Show zirconia coating. The exhaust stack is an extension of the exhaust plenum, through which the exhaust gases are discharged to the atmosphere. Three rows of 1/2-inch-diameter cooling tubes could be installed for extended study on the effect of the number of rows of tubes. Each row is independent as to the working fluids inlet and outlet. However, only one row of tubes of 1 /2-inch-diameter were installed and tested for concept proof. The porous matrix is filled to about 1/4 inch above the upper surface of the cooling tubes with 1/4-inch-diameter alumina spheres. The total depth of the bed is about 1-3/8 inches. Data Collection In the preliminary study, the combustion rate, excess air ratio, heat-transfer flux, combustion emissions (NOx and CO), and pressure drop across the unit were measured to evaluate the performance of the surface combustor-heater. The flow rate of natural gas was measured using a rotameter and a positivedisplacement natural gas meter, whereas the combustion air flow, drawn from the test room at ambient temperature, was monitored with a rotameter. The static pressure of the natural gas/combustion air mixture was measured by a pressure gauge located in the mixture plenum. This pressure represents a pressure drop across the water-cooled distribution grate and the porous matrix made of 1/4-inch-diameter alumina spheres. For the initial series of tests, only seven water-cooled tubes had been installed in the first row to prove the concept. The inlet water temperature was measured with a mercury thermometer. On the outlet side, water temperatures and flow rates from the cooling tubes and the distribution grate were measured independently. Water outlet temperatures were measured by a mercury thermometer and flows were determined by the time required to fill up a 1-quart container. A water-cooled probe was used to sample combustion products. The probe at the cold end was equipped with a section of externally heated stainless steel tubing to maintain a sample temperature of about 1900F so that moisture would not condense. The warm sample was passed through a millipore filter to remove any solid particles and a Permapure dryer to remove moisture. The dried sample was supplied to oxygen (02)' carbon monoxide (CO), and nitric oxide (NO and NOx) analyzers through Teflon tubing. 11 INSTITUTE o F GAS TEe H N 0 LOG Y |
