| OCR Text |
Show Figure 4 shows the two limits for the enclosed WSB with f = 7 cm. Also shown are the polynomial fits for the open f = 7 cm burner results (as in Figure 3). It is clear that the lower limit for the enclosed burner is almost identical to the open case. For the upper limit (flashback) the enclosed burner has a slightly lower swirl number compared to the open case. These data show that the swirl requirement of the WSB is fairly independent of power level and enclosure. The first set of results obtained from the water heater test station is shown in Figure 5. Thermal efficiencies for ~ ~ 0.7 at three power levels with various water flow rates are compared. As can be seen, there is no systematic change in thermal efficiency with water flow rate. For the 15 and 18 kW runs, the thermal efficiency averages about 80%, comparable to the 82% achieved by the current model Telstar heaters. There is, however, a decrease in efficiency when the WSB power input is decreased to 12 k W (40,000 Btu/h). At this low power, the system may be below the optimal performance point for the Telstar heat exchanger, nominally designed for 15 kW. 1 0.9 0.8 Q - 0 · 0 • 0 e ~ 0.7 x tEfficiency x x x x x 0.6 - x x 0.5 0.4 x 12 kW, ~ = 0.71 0.3 - 15 kW, ~ = 0.74 0.2 o 18 kW, ~ = 0.72 0.1 0 I I -, T 8 12 16 20 24 28 32 36 Water Flow Rate (liters/min) Figure 5: Efficiency versus water flow rate with constant power and ~ 10 |
