Improving Aerodynamic Performance of a Commercial Kitchen Hood

• Main Authors: Zong-Lian Li, 李宗聯
• Other Authors: RF Huang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/27t4cq

碩士 === 國立臺灣科技大學 === 機械工程系 === 102 === A box-type quad-vortex commercial kitchen hood was developed and experimentally studied. The laser-light-sheet-assisted smoke flow visualization technique was used to investigate the characteristic flow motions near the hood inlet, around the boundaries, and inside the hood at high temperatures and various suction velocities. The quad-vortex commercial kitchen hood consisted of three important elements at the hood roof: (1) an elongate suction slot, (2) a down-blowing planar jet, and (3) a vortex generator. Two deflection plates were installed upright at the side walls. Boundary-layer separation controllers were arranged at the peripheral of the hood inlet. The smoke flow visualization results showed some findings. The most risky areas favoring for high-temperature containment leakage were the inlet of the hood roof due to the high-temperature and high-heat-release rate induced buoyancy and gas expansion effect. The elongate slot suction worked with the down-blowing planar jet to form a recirculation bubble which isolated the outward-expanding hot gas or oil fumes. The vortex generator induced another recirculation bubble for isolation of the hot gas and oil fumes for the extremely high-temperature and high-heat-release operations. The deflection plates stopped the reverse flows going along the side walls and assisted to for two corner vortices. These two corner vortices subsequently induced two large vortices around the hood central area. The vortices carried the hot gas and fumes, rose up spirally, inclined rearward (due to the Coanda effect and rearward-offset of suction slot), and exhausted through the suction slot. The boundary-layer separation controllers installed at the inlet of the side walls and roof reduced the size of the separation-induced recirculation bubbles, and therefore decreased the risk of hot gas and oil fume leakages. The detailed physical mechanisms of flow and leakages were discussed and supported by flow visualization pictures. The hood presented no observable spillages of oil fumes when the suction velocity and the down-blowing jet velocity were 16 m/s and 2.5 m/s, respective, under the operation conditions of pot temperature 550 ℃ and heat-release rate 30 kW.