Flow Characteristics and Spillage Mechanisms of Wall-Mounted and Jet-Isolated Range Hoods Subject to Influence from Cross Draft

Abstract

The effects of draft on the flow and spillage characteristics of wall-mounted and jet-isolated range hoods were investigated. A specially designed draft generator that could supply low-swirl air current was used to provide "cross draft" from three directions, lateral (θ = 0(o)), oblique (θ = 45(o)), and front (θ = 90(o)), with respect to the center point of the range hoods. Flow characteristics of oil mist were inspected through visualization of smoke flows with light scattering (laser light sheet-assisted visualization of smoke flow). The leakage mechanisms, which were closely related to the flow features, were studied by examining both movies and still pictures showing smoke-flow evolution. The sulfur hexafluoride tracer gas concentration detection method was employed to measure the capture indices. The results showed that the lateral draft pushed the pollutants generated under the hood in the opposite direction and induced serious spillage. The oblique draft pushed the pollutants toward both the rear wall and opposite side and induced more serious spillage than did the lateral draft. The frontal draft forced the pollutants to bifurcate into streams moving toward the left and the right, and induced the most serious pollutant spillage among the three tested drafts. Pollutant spillage became critically significant as the cross draft velocity was increased to greater than 0.2 m/sec. Spillage of pollutants increased as the velocity of the cross draft was increased. Increasing the suction flow rate of the range hood may increase resistance to the draft, but the benefits were limited at draft velocities greater than 0.2 m/sec. Both range hoods had a similarly low capture index under the influence of the lateral draft. For the oblique and frontal drafts, the jet-isolated range hood demonstrated a higher capture index than did the wall-mounted range hood.

Flow characteristics of an inclined air-curtain range hood in a draft

“…To compare the results represented by Chen et al . 19 ) , the performances of the conventional and jet-isolated range hoods were obviously decreased when the draft velocity was higher than 0.3 m/s. The same result shown in Fig.…”

“…It was different from the effect of walk-by mentioned by Huang et al 18 , 21 ) . Chen et al 19 ) presented the containment of conventional range hoods operating under the effect of a cross draft. When the velocity of the cross draft was greater than 0.2 m/s, the pollutant spillage was increased with the increasing draft velocity.…”

Effects of Window Position and Exhaust Flow Rate on Residential Kitchen Hood Performance: A Validated Numerical Approach

“…When the rising thermal plume was disturbed by the makeup air, it would affect the capture area of the hood. Chen et al examined the hood performance under the effects of the cross draft from lateral, oblique, and front directions [34]. They found that cross draft could lead to the spillage of cooking emissions, and the effect worsened as the airflow velocity increased.…”

Measurement of particle removal performance for a novel design of range hood

“…Local exhaust ventilation (range hood) is an effective method to capture contaminants in residential buildings. To improve the efficiency for capturing contaminants and provide healthier indoor air quality, some innovative technologies had been studied: Aaberg hood [6][7][8][9][10][11][12], separation plate technology [13][14][15], air curtain technology [16][17][18][19][20][21][22][23], tornado-like suction airflow technology [24,25], and make-up air technology [26][27][28][29]. Some optimizations of the range hood have been proposed: Shaping the outlet [30], changing the structure of the fan [31,32], and adjusting some influential factors (airflow rate, dimension, and burner * Corresponding author: fl@byg.dtu.dk position of the range hood) [33][34][35][36].…”