Analysis of Influence Characteristics of Flow Field in New Range Hood

• Main Authors: LIAN, CHANG-YUAN, 連承淵
• Other Authors: LU, CHI-WUN
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/kwh2ze

碩士 === 國立勤益科技大學 === 冷凍空調與能源系 === 107 === A range hood should be used to maintain the air quality when cooking in kitchen. But nowadays, the exhaust effect of range hood in market is generally unsatisfactory. Considering health of the cooks in all families, whether the performance of a range hood can completely remove fume should be explored in depth. Previously, our laboratory has published a paper on using numerical simulation to design a new type of range hood. In this paper, the hood type of the new range hood was used to explore the factors affecting fume removal efficiency by CFD numerical method. In this paper, the effect of three factors, including initial rising velocity of fume, kitchen space and front baffle leakage improvement, were explored on temperature, pressure, diffusion area. Furthermore, based on the accumulated experience of our laboratory in designing in-line tube fan, a new fan was designed, so that its performance could be matched the requirement that the range hood could overcome the system resistance and remove the exhaust fume completely. In a kitchen model 4.2 m long, 1.8 m wide and 2.4 m high, the simulated results show that the exhaust volume flow rate shall be larger than 14 CMM, 16 CMM and 20 CMM respectively when the initial rising velocity of fume is 0.1 m/s, 0.5 m/s and 1.0 m/s. The kitchen space models were set as 4.2 m long and 1.8 m high, with the height of 1.0 m, 2.0 m, 3.0 m and 4.0 m respectively. The simulation results of the 4 kitchen space models show that, in case of the air volume flow rate of 12 CMM, the one is 2 m long has the best efficiency in fume exhaust, but when the air volume flow rate is increased to 14 CMM, the one is 3 m long has the best efficiency in fume exhaust. In general, the kitchen space has little effect on fume exhaust but has great effect on temperature. From the leakage improvement simulation, when baffles are used, the fume escape is significantly improved and the effects are better with the height is increased. However, when the fume cannot be removed immediately and is remained inside the hood, it still escapes over the baffle toward the face of the cook. No such phenomenon occurs when the baffle height increases to 150 mm. When the hood is equipped with a higher baffle and the range hood air volume flow rate is insufficient to remove the exhaust fume completely, the fume will gradually accumulate in the region enclosed by the baffle. After the stack thickness of the fume exceeds the baffle height, a higher concentration of fume will escape. Finally, CFD was used to modify the in-line tube fan designed by our laboratory, so that its performance is as following: the maximum efficiency is 70%, and at this point, the air volume flow rate is 21 CMM and the static pressure is 399.6 Pa. At the operation point, fan performance curve intersects with the resistance curve of the exhaust pipe system connected with the range hood, the air volume is 23 CMM and the efficiency is about 63%, indicating that the fan performance meets the removal of fume completely requirements.