Range Hood Research Articles

Oil-immersion stable superamphiphobic coatings for long-term super liquid-repellency

• The coatings consist of pre-modified SiO 2 nanoparticles with high-degree densification. • The coatings exhibit stable superamphiphobicity under prolonged immersion of mixed oils. • The performance is over 20 times more immersion-durable against pre-existing surfaces. • Coated impellers achieve up to 65% contamination-resistance under accelerated testing. Superamphiphobic coatings have attracted tremendous interest from both academia and industry owing to their potential for self-cleaning and anti-fouling. However, many state-of-the-art superamphiphobic coatings are unable to preserve their super-repellent properties after prolonged liquid immersion. Thus, practical applications have so far been drastically limited. Herein, we highlight the immersion-stable performance of a nanostructurally-densified superamphiphobic coating possessing super liquid repellency to water and various low-surface-tension liquids. They exhibit excellent superoleophobic properties and functional stability even after prolonged immersion in mixed synthetic and vegetable oils. This immersion-stable superamphiphobic coating was also tested on household kitchen appliances under real-world conditions. Particularly inaccessible components such as the impeller and grease traps of range hoods were coated. Impellers demonstrate an improvement of up to 65% contamination-resistance while grease traps remained largely dry after collected oils were disposed. These findings highlight the potential of using nanostructurally-densified superampiphobic coatings as anti-fouling surfaces in the kitchen environment, with potential applications in petroleum extraction and oil transportation.

Indoor air quality in new and renovated low-income apartments with mechanical ventilation and natural gas cooking in California.

This paper presents pollutant concentrations and performance data for code-required mechanical ventilation equipment in 23 low-income apartments at 4 properties constructed or renovated 2013-2017. All apartments had natural gas cooking burners. Occupants pledged to not use windows for ventilation during the study but several did. Measured airflows of range hoods and bathroom exhaust fans were lower than product specifications. Only eight apartments operationally met all ventilation code requirements. Pollutants measured over one week in each apartment included time-resolved fine particulate matter (PM2.5 ), nitrogen dioxide (NO2 ), formaldehyde and carbon dioxide (CO2 ) and time-integrated formaldehyde, NO2 and nitrogen oxides (NOX ). Compared to a recent study of California houses with code-compliant ventilation, apartments were smaller, had fewer occupants, higher densities, and higher mechanical ventilation rates. Mean PM2.5 , formaldehyde, NO2 , and CO2 were 7.7µg/m3 , 14.1, 18.8, and 741ppm in apartments; these are 4% lower, 25% lower, 165% higher, and 18% higher compared to houses with similar cooking frequency. Four apartments had weekly PM2.5 above the California annual outdoor standard of 12µg/m3 and also discrete days above the World Health Organization 24-hour guideline of 25µg/m3 . Two apartments had weekly NO2 above the California annual outdoor standard of 30ppb.

Polycyclic and nitro-polycyclic aromatic hydrocarbon pollution characteristics and carcinogenic risk assessment of indoor kitchen air during cooking periods in rural households in North China.

Medium-flow atmospheric samplers were used to collect particulate (PM2.5) and gaseous samples from the indoor kitchen of each of 35 randomly selected rural houses in North China while a meal was being cooked. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 9 nitro-PAHs (NPAHs) in the samples were quantified by high-performance liquid chromatography (HPLC). This study provided the real PAH and NPAH pollution characteristics and carcinogenic risk produced by cooking in rural indoor kitchens in North China. The mean PAH and NPAH concentrations in air in the indoor kitchens during cooking periods were 4049.1 and 1741.6 ng/m3, respectively. The PAH and NPAH concentrations were lower in the particulate phase than the gaseous phase. The mean PAH and NPAH concentrations were much higher for cooking using coal than for cooking using liquefied petroleum gas (LPG) or electricity. The PAH and NPAH benzo[a]pyrene toxic equivalent (TEQBaP) concentrations for cooking using coal were 1823.3 and 2760.9 ng/m3, respectively. Lower PAH and NPAH concentrations were found in kitchens with than without range hoods. Range hoods decreased the PAH and NPAH TEQBaP concentrations by 68.8% and 61.9%, respectively. Appropriate fuel and ventilation choice will improve air pollution in indoor kitchens during cooking. The results provide important evidence for changing cooking habits and developing policies for cooking in rural China.

Simulation Study of Air Conditioning System Location in Commercial Kitchen

Working in a commercial kitchen in restaurants and hotels is physically challenging. In the Middle East, summer temperatures are very high and require proper ventilation and air conditioning for comfortable working. In the current study a typical kitchen with dimensions 5 m × 4 m × 3 m, with heat source and range hood is modelled using computational fluid dynamics software. A comparative analysis was conducted on the location of the air conditioning system in the kitchen space. The investigated locations of the air conditioning system were on the kitchen side wall and ceiling. The results of the simulation showed that placing the air conditioning system in the ceiling at the centre of the kitchen produced better air circulation. The air flow close to the hood had sufficient velocity to remove heat, contaminants and CO2 generated from the cooking process

CFD Simulation Analysis on Make-up Air Supply by Distance from Cookstove for Cooking-Generated Particle.

Indoor cooking is the main cause of particulate matter (PM) within residential houses along with smoking. Even with the range hood turned on, cooking-generated PM can spread quickly into the living room due to the heat generated by the cookstove. In order to improve the PM spread prevention performance of the range hood, a supply of make-up air is needed. Generally, make-up air is supplied through a linear diffuser between the kitchen and living room. In such cases, it is necessary to determine the appropriate location of the supply diffuser. This study evaluates the spread of PM according to different locations of the supply diffuser, which feeds in make-up air. For this purpose, indoor airflow and PM spread were analyzed through CFD (Computational Fluid Dynamics) simulation analysis. By changing the location of the supply diffuser from the contaminant source, PM concentration was analyzed in the kitchen and living room of an apartment house in Korea. Based on the results, the optimal installation location was determined. In this study, 1.5 m from the source was the most effective location of make-up air supply to prevent the spread of cooking-generated particles.

The effects of cook-top temperature on range hood capture efficiency

In this study a test procedure for determining capture efficiency (CE) of wall-mounted range hoods, namely ASTM-E3087.18, was used to investigate how the temperature of the simulated cook-top influences CE. ASTM-E3087.18 was initially released in 2017 and revised within one year to modify the temperature requirements of the cook-top from 200 °C to 160 °C; however, there is no evidence of a detailed study being performed to quantify the effects of this temperature change on CE. The study reported herein performed testing at 200 °C, 160 °C and 130 °C for five range hoods with three different design types. CE ranged from 60.3–92.9%CE with CE variations as high as 9.2%CE when varying temperature, and uncertainty (δ) always varying by less than 1.0%CE. The influence of cook-top temperature on CE repeatability, reproducibility and variability was also investigated, with each metric varying by a maximum of 1.2%CE, 1.5%CE and 1.1%, respectively, with varying temperatures. Range hoods with poor burner coverage (i.e. over-the-range microwaves) showed higher variability/uncertainty, indicating temperature effects are more dominant when range hoods have less burner coverage. It is possible that future HVI/ASHRAE certifications specify different acceptability/test requirements for CE, as well as the CE uncertainty/repeatability, of range hoods with poor burner coverage.

Evaluation of particulate matter concentrations according to cooking activity in a residential environment.

This study aimed to determine the ventilation conditions required for suitable indoor air quality management during cooking in a typical South Korean residential home. We measured the concentrations of particulate matter (PM10) and fine particulate matter (PM2.5) under different ventilation conditions during the cooking of different food materials in the kitchen of a multi-family house, which is the representative residential space in South Korea. Pork belly and mackerel, which are the staple meat and fish products of Korean people, were prepared (200g of each) and cooked via roasting. The PM10 and PM2.5 concentrations were measured three times for 1h at 1min intervals under twelve ventilation conditions. To investigate the PM10 and PM2.5 concentration distribution characteristics and the reduction effect according to ventilation condition, the ratio of the concentration during cooking to the initial concentration was calculated for each condition. Factors causing the emission of PM10 and PM2.5 for each food material and under each ventilation condition were analyzed using principal component analysis and verified using one-way analysis of variance and post hoc analysis. The PM10 and PM2.5 concentrations generated during the cooking of pork belly and mackerel reached their maximum values when no ventilation was used. Under this condition, PM10 concentrations were 246.27 and 1227.71μg/m3 while the PM2.5 concentrations were 161.93 and 760.82μg/m3 for pork belly and mackerel cooking, respectively. The PM10 and PM2.5 concentrations were also found to be high when a range hood and air cleaner were used, indicating that it is necessary to improve the performance of ventilation devices and to use appropriate ventilation methods. The use of natural ventilation exhibited a high PM10 and PM2.5 reduction effect compared with the ventilation conditions that used ventilation devices. Using natural ventilation together with ventilation devices was found to be the most effective method of reducing the PM10 and PM2.5 generated during cooking. In conclusion, PM10 and PM2.5 concentrations generated during the cooking of pork belly and mackerel varied depending on the ventilation condition, but they were high when inappropriate ventilation methods were used. Therefore, using appropriate ventilation conditions is effective in reducing PM10 and PM2.5 generated during cooking.

공동주택의 주방공용배기시스템 성능개선에 관한 연구

As a result of developing and evaluation the performance of the kitchen ventilation system, a new kitchen ventilation system, which can improve the exhaust performance of the kitchen ventilation system installed in the existing apartment house and improve the noise problem from the range hood, was conducted as follows. The same conclusion was reached. First, the development system is a kitchen exhaust system, and consists of a roof fan with a power fan, an exhaust standing duct, and a range hood that can selectively incorporate a power fan. It was possible to improve the exhaust performance through the control of the roof fan with a built-in PCB, and the noise level in the kitchen could be reduced below the standard valueby removing the power fan in the range hood. Second, the noise level generated by the range hood could be reduced to below the standard value by removing the power fan. The noise level of the range hood measured under various assumed conditions met the standards of the Korean Standard for Equipment Association. As a result of verifying the performance of the kitchen exhaust performance, noise in the range hood, dew condensation, and backflow into the household, which have been pointed out as problems in the existing kitchen ventilation system. It shows that natural ventilation performance, convenience of use, maintenance and energy cost are reduced through the electric air damper.

Control of temperature and fume generation by cooking in a residential kitchen by ceiling radiative cooling and fume hood extraction

The heat radiation in a residential kitchen was simulated by CFD (Computational-fluid-dynamics) to evaluate the cooling by a radiant cooling ceiling panel and pollution dispersion by the range hood and the air extraction system. The kitchen has a 2-hobs stove and a fume hood for removing waste heat and fumes. The simulation was validated by measurements in a domestic kitchen in a home in Changsha, China, where summer temperature is generally about 33 °C and often over 35–42°C. The simulation results show that the pollutant concentration in the kitchen during cooking was much lower than the Chinese standard criteria of GB/T18883-2002. A standard turbulence model was used, which indicated satisfactory distribution of temperature and airflow in the kitchen. The indoor airflow velocity was low. The airflow temperature when both hobs were used was slightly higher by 3–4°C than when a single hob was used. The temperature in the kitchen during cooking was about 28 °C, which was a degree lower than the living-room temperature, thus maintaining a comfortable thermal and healthy environment. The radiant cooling in the ceiling was shown to be a significant contributing factor. The ring suction type range hood has a sufficient capacity to remove the kitchen fume contaminants.

CFD modeling of the [formula omitted] capture by range hood in a full-scale kitchen

Air quality criteria in residential houses are increasing continuously. Multiple studies tend to use commercial CFD software in order to predict and optimize the flow conditions in range hoods. Most of them modeled the range hood without considering the rotating fan. In the present work, a new open-source solver was developed using the OpenFoam libraries. It is based on a buoyancy Boussinesq solver and a turbulent passive scalar transport equation accounting for the heated CO2 extraction by the rotating fan, fully modeled using the Multiple reference frame (MRF) approach. The new solver is carefully validated against experimental results for three benchmark cases: a CO2 plume, a differential heated cavity and the performance curve of a rotating fan. The model has been confidently used to model the CO2 extraction in a realistic residential kitchen considering one to four burners on. An improvement of 30% in the capture efficiency is reached by increasing the extraction flowrate of the fan from 100 to 300 cfm. An extraction efficiency of 100% is observed for flowrates above 330 cfm.

Analysis of winter formaldehyde and volatile organic compound pollution characteristics of residential kitchens in severe cold regions of northeast China

The formaldehyde (HCHO) and volatile organic compound (VOCs) pollution characteristics of the residential kitchen in severe cold regions of northeast China were investigated by on-site measurement, questionnaire and correlation analysis. A total of 33 residential kitchens in three cities were selected as samples. Gas chromatography–mass spectrometry, phenol reagent spectrophotometer and 2,4-dinitrophenylhydrazine were applied. The change of VOC concentration during cooking was tracked by parts per billion ppb RAE detector. Moreover, the CO2 tracer gas method was used to measure air changes when the range hood was open under different window-opening angles. The results demonstrate that though the excess rate of HCHO in the kitchen was only 5.3% before cooking, the average VOC concentration (1.269 mg/m3) exceeded far beyond the standard and was obviously higher than other climate zones. During cooking, the VOC concentration was in a state of seriously exceeding standard. The average concentration of aldehyde and ketone pollutants during cooking was 0.431 mg/m3. Frying produced more VOCs than stewing. The influence factors of HCHO and VOC pollution characteristics were explored. Increasing make-up air and optimizing cooking habits are significant in alleviating kitchen pollution in northeast China.

Assessment of cooking-generated particle removal efficiency of range hood with auxiliary air supply system

Assessment of cooking-generated particle removal efficiency of range hood with auxiliary air supply system

Factors influencing the airflow rate of kitchens in cooking exhaust shaft system of high-rise residential buildings

Insufficient shaft cross-sectional area of cooking exhaust shaft system in high-rise buildings influences the ventilation capacity of range hoods in kitchens, which cause damage to human health or increase the energy consumption of the building. There are numerous factors that affect ventilation capacity of the exhaust system, such as exhaust shaft cross section, range hood performance, operating rates and distribution of range hoods. The purpose of this research is to conduct a quantitative study on the effects of these parameters on the airflow rate of kitchens. A theoretical model of the cooking exhaust shaft system was established according to the Fluid Network Theory, it was further validated by a full-scale model experiment and used to calculate the airflow rate of kitchens for a 33-storey residential building. The results show that when the exhaust shaft cross section is designed to be 500 mm × 400 mm according to standard, regardless of the performance of the range hood, the airflow rate of kitchens of some users will be either insufficient or excessive, and cannot meet 300~500 m3/h required by Chinese standards. But when the shaft cross section is 750 mm × 600 mm and the standard range hoods are used, the airflow rate of kitchens can reach 300~500 m3/h at any operating rate. The established model can be applied in other countries to study the ventilation effect of the similar cooking exhaust shaft system in residential or other buildings. The research results can be useful for improving the design of the cooking exhaust shaft system in residential buildings.

Experimental study on particle splash pollution from cooking with fluorescent droplets

Particles generated by cooking are an important source of indoor pollutants. Most studies have focused on only airborne particles rather than including a wide range of particle sources, such as the large oil droplets generated by splashing during cooking, which constitute most of the mass concentration of indoor pollutants. In this study, the fluorescent characteristics of edible oil were enhanced by adding a fluorescent agent (excitation wavelength: 365 nm, emission wavelength: 445 nm) so that the particulate matter information could be well extracted from the samples. Sampling points were set on the kitchen countertop, the wall, and the dummy surface, and the ventilation removal of large particles by the range hood was compared under different airflow rates. The results showed that the overhead range hood had little effect on removing splashed oil droplets, but the airflow structure strongly affected the motion track of “medium” oil droplets (>10 μm). Proper airflow structure can reduce the range of splashing oil droplets. The horizontal and vertical splash radii of the oil droplets were 0.72 m and 0.63 m, respectively. The splash radii were more suitable indices for evaluating range hood performance than capture efficiency. At the same position with different sample angles, the horizontal sampling concentration of the wall was 2.49 times that of the vertical sampling concentration.

Indoor air quality in California homes with code-required mechanical ventilation.

Data were collected in 70 detached houses built in 2011-2017 in compliance with the mechanical ventilation requirements of California's building energy efficiency standards. Each home was monitored for a 1-week period with windows closed and the central mechanical ventilation system operating. Pollutant measurements included time-resolved fine particulate matter (PM2.5 ) indoors and outdoors and formaldehyde and carbon dioxide (CO2 ) indoors. Time-integrated measurements were made for formaldehyde, NO2 , and nitrogen oxides (NOX ) indoors and outdoors. Operation of the cooktop, range hood, and other exhaust fans was continuously recorded during the monitoring period. Onetime diagnostic measurements included mechanical airflows and envelope and duct system air leakage. All homes met or were very close to meeting the ventilation requirements. On average, the dwelling unit ventilation fan moved 50% more airflow than the minimum requirement. Pollutant concentrations were similar to or lower than those reported in a 2006-2007 study of California new homes built in 2002-2005. Mean and median indoor concentrations were lower by 44% and 38% for formaldehyde and 44% and 54% for PM2.5 . Ventilation fans were operating in only 26% of homes when first visited, and the control switches in many homes did not have informative labels as required by building standards.

Occupant exposure and ventilation conditions in Chinese residential kitchens: Site survey and measurement for an old residential community in Shanghai

Chinese residents often use range hoods to exhaust cooking oil fumes (COF) and at the same time open inner/outer doors and windows for natural air supplement. Factors such as the layout of kitchens, the exhaust efficiency of range hoods, and the effect of natural air supplement, directly determine transmission characteristics of COF, which in turn affect the capture efficiency of range hoods and the COF exposure of residents. This study carried out a survey on the ventilation conditions in residential kitchens and conducted measurement of residents’ COF exposure. In an old residential community of Shanghai, we measured the three-dimensional size of kitchens, the areas and positions of doors and windows and the exhaust rate of range hoods of 30 residential kitchens. 7 households were randomly selected to monitor 24-h PM2.5 concentration around stoves in kitchens. Meanwhile, one volunteer from each of the 30 households participated in personal PM2.5 monitoring using wearable sensors. To quantify the occupant exposure during cooking, two indexes including the exposure contribution rate and additional exposure concentration were introduced. The results showed that the ventilation conditions in these kitchens were generally poor and considerably different from each other. Meanwhile, the concentration dynamics of PM2.5 during cooking showed short-term (about 10–20 min) and high-dose (the peak concentration reached 800–1000 μg/m3) characteristics compared with that in other periods.

Effects of chef operation on oil fume particle collection of household range hood.

Kitchen range hood is used to remove cooking oil fume in most of family. The oil fume collection efficiency of range hood is demand to be improved for reaching healthy indoor air quality in residential kitchen. The effects of chef disturbance intensity on the fume particle collection of range hood are quantified by computational fluid dynamics (CFD) model. The chef operation is considered by introducing a moving momentum source where the collection efficiency of fume particle is defined by the particle residence time. The collection efficiency of fume particle is proposed to be classified as the primary collection efficiency and the secondary collection efficiency of fume particle. The results indicate that the primary collection efficiency of fume particle is decreased by 26.4% in vertical disturbance (VD) mode of chef stirring with the rotation velocity from 0 to 1.5rps. Meanwhile, the primary collection efficiency is decreased by 8.5% in horizontal disturbance (HD) mode for the same range of the rotation velocity of chef stirring. It is further found that the secondary collection efficiency of fume particle can be used as an indicator of the fume particle concentration of kitchen.

Effects of the Guiding Tank on Flow Characteristics inside the Double-Suction Squirrel-Cage Fan for Range Hood

Effects of the Guiding Tank on Flow Characteristics inside the Double-Suction Squirrel-Cage Fan for Range Hood

Structure design of low-frequency broadband sound-absorbing volute for a multi-blade centrifugal fan

A novel low-frequency broadband sound-absorbing structure is proposed for the noise reduction of an existing multi-blade centrifugal fan in range hoods. Incorporating the advantages of both sound absorption materials and micro-perforated panel absorbers in series and in parallel with unequal cavity depths, the compound absorber is designed to suppress and absorb the radiated noise mainly in the wide- and low-frequency range below 2 kHz. Parametric studies for influences of structural parameters on sound absorption coefficient and absorption bandwidth are performed with numerical method, respectively for sound absorption materials and micro-perforated panel absorbers in series and parallel arrangements. Due to the non-uniform directivity of far-field sound radiation, the optimal installation position of the compound sound-absorbing structure at the volute, the helical surface or the two lateral side planes, is investigated as well. Taking the actual structures of the centrifugal fan, special working environment of the range hood, processing cost and difficulty into consideration, a practical low-frequency broadband compound absorber with an elaborate selection of structural parameters is designed and applied to the appropriate positions. Results of the acoustic test in the anechoic chamber according to the Chinese national standard indicate that the A-weighted sound power level on the monitoring spherical surface meets the acoustic target of lower than 64.0 dB(A) under restrictive conditions of large flow rate, high pressure and small size.

Influence of nanofiber window screens on indoor PM2.5 of outdoor origin and ventilation rate: An experimental and modeling study

When the outdoor PM2.5 pollution is severe, if the windows are open, the occupants tend to be exposed to higher indoor PM2.5 of outdoor origin. However, if the windows are closed, the ventilation rate tends to be insufficient for removing air pollutants generated indoors. Opening windows with the use of nanofiber window screens can be an alternative strategy that can balance between indoor PM2.5 of outdoor origin and ventilation rate. This study fabricated a number of nanofiber window screens and conducted a series of experiments in a laboratory setup to measure the PM2.5 removal efficiency and pressure drop with different window opening angles. A simple model was then developed for predicting the pressure drop, and the measured data was used to validate the model. Finally, the measured data and the validated model were used for two application cases. In the natural ventilation case, the use of nanofiber window screens can effectively reduce indoor PM2.5 of outdoor origin, and the ventilation rate can be improved when compared with infiltration in the house. However, the nanofiber window screens could not reduce the PM2.5 level in the kitchen with a range hood when the cooking PM2.5 emission rate was high.