Ventilation performance of a novel multi-mode fume hood with supply air on contaminant with different densities

Air curtains is promising in reducing the short-range infection risk in hospitals. To quantitatively evaluate its performance, this paper explores air curtains equipped on normal consulting desk to avoid doctor’s direct exposure to the patient exhaled pollutants. A numerical investigation is conducted to evaluate the effects of supply air velocity and angle on cutting off performance. Simulation results show that the average mass fraction of exhaled pollutants decreases significantly (70%–90%) in the consulting ward, indicating satisfying performance of air curtains. Increasing supply air velocity is demonstrated to be conducive in forming full air curtains, whereas an excessively high supply air velocity may be of adverse effects by entraining exhaled flow. Besides, the supply air angle is also critical due to its coupling with supply air velocity. It is found that larger angle (0°–40°) is better where velocity is less than 3 m/s, otherwise a small angle (20°) is preferable where velocity is larger than 3 m/s. Exhaled flow could be well suppressed at the supply air angle 20° but moves over air curtains at 40°. This study can provide effective and intuitive guidance in applying air curtains in consulting wards.Electronic Supplementary Material (ESM)Supplementary material is available in the online version of this article at 10.1007/s12273-020-0649-7. The ESM files include the animation of patient exhaled droplets from the droplet birth at 0 s to 5 s under the supply air angle 0°, 20°, 40°, at supply air velocity 3 m/s.

Experimental Study on the effects of layered air supply angle and air supply temperature on indoor environment

Range hood is a common ventilation appliance applied in a kitchen for maintaining healthy environment. This paper numerically studied the effect of air curtain on capture performance of a range hood, which was equipped in a residential kitchen chamber of 3.5 m * 2.7 m * 2.4 m. Two key parameters of air curtain, air-supply velocity and angle were investigated for improving the capture performance with CFD methods. Only when both the air-supply velocity and angle were well defined simultaneously, could the range hood have a good capture performance. When air-supply angle is 4°, air-supply velocity is recommended at 2.0–2.5 m/s. When air-supply velocity is 4.5 m/s, air-supply angle is recommended at 10°–14°. In the above situation, the range hood has better capture performance. The findings showed that the air curtain with reasonable air-supply velocity and angle could effectively improve the capture performance of range hood and protect the cook.

To increase the efficiency of local exhaust hoods for removing harmful substances emitted during technological processes, air is supplied by jets to create an air curtain (air-jet covers). The air curtain prevents the spread of harmful substances, does not interfere with the technological process, and leaves the equipment open for control and monitoring. The device of local supply and exhaust ventilation of the open doorway of the UKM Classic M 2005 chamber made by Mauting is considered. The chamber is designed for heat treatment of meat products in the food industry. Geometric models have been developed, including a heat treatment chamber, a room from which the chamber is loaded, a supply and exhaust hood above the door from the chamber to the room, and a supply air duct with air distribution devices. For comparison, an option of using an exhaust hood without supply air was also studied. The STAR-CCM+ software package was used as a calculation program. The results of computational experiments on modeling the operation of the local ventilation system of the heat treatment chamber are presented. The analysis of the calculation results and comparison of the efficiency of local ventilation devices are carried out. The studied design of the supply and exhaust hood ensures that heat and gases coming out of the heat treatment chamber are captured at a 17% lower supply and exhaust air flow rate compared to the exhaust hood.

Field experiment and simulation of hot air curtain for cold protection in subway aisle in severe cold regions

Decision-making analysis of air supply strategies for high rack cold stores

Airpak was applied to numerically simulate the air distribution under the same air supply temperature ,different air supply velocity (3.6m/s、2.7m/s and 1.8m/s ) and air supply angle (+15°、-45° and-75°) , and evaluate thermal comfort by Comparative analysis velocity fields, temperature fields, PMV—PPD. The results show that different air supply velocity and air supply angle have a significant impact on indoor air distribution under the same air supply temperature. Air supply angle Plays a vital role in pattern and distribution of indoor flow field,air supply velocity mainly effect the magnitude of indoor velocity and temperature. Synthetically comparied, the model’s best supply parameters are supply velocity 2.7m/s and supply angle75°,which mean value of indoor PMV is-0.09, PPD is 8.5%.

Research on a new optimization method for airflow organization in breeding air conditioning with perforated ceiling ventilation

A wall hanging air-conditioning office was simulated on three different air supply angle and three different air supply velocity by the AIRPAK .Based on the velocity fields, temperature fields, PMV-PPD obtained, analysis indoor thermal comfort. The result shows obvious difference of air distribution and great effect of indoor thermal under different air supply angle and different air supply velocity. By comprehensive comparison, the best air supply condition is the one of 75° downward, 3.0m/s.

Numerical Simulation of Energy Utilization Coefficient Influenced by Desktop Personalized Ventilation Modes

The purpose of this study is to evaluate the effect of air curtains on indoor environment and dehumidification energy consumption for different air supply angle and velocity. The numerical investigation was conducted in a low-humidity plant located in the atmospheric boundary layer. The standard k-epsilon turbulence model was used in simulation study. The optimum air supply angle and velocity were evaluated based on temperature and humidity distribution. The simulation cases range in air supply angle from 0° to 20° and velocity from 6m/s to 14m/s, which were studied by means of orthogonal experiments. Simulation results show that air curtain can reduce the average indoor temperature of the plant by up to 3.9°C and reduce the average moisture content by up to 86.6% compared to the cases without air curtains. The energy saving assessment of the dehumidification rotor system shows a parabolic variation in energy consumption with increasing air velocity at a certain air supply angle. The optimum energy consumption occurs at the range of 9-11m/s for air supply velocity. When air supply velocity is over 11m/s, the airflow exchange is enhanced by air curtain at the plant opening, resulting the higher energy consumption from air leakage for dehumidification.

The purpose of this study is to evaluate the effect of air curtains on indoor environment and dehumidification energy consumption for different air supply angle and velocity. The numerical investigation is conducted in a low-humidity plant located in the atmospheric boundary layer. The standard k-epsilon turbulence model is used in the simulation study. The optimum air supply angle and velocity are evaluated based on temperature and humidity distribution. The simulation cases range in air supply angle from 0° to 20° and velocity from 6 m/s to 14 m/s, which is studied by means of orthogonal experiments. Simulation results show that air curtain can reduce the average indoor temperature of the plant by up to 3.9°C and reduce the average moisture content by up to 86.6%. The energy saving assessment of the dehumidification rotor system shows a parabolic variation in energy consumption with increasing air velocity at a certain air supply angle. The optimum energy consumption occurs in the range of 9–11 m/s for air supply velocity. When air supply velocity is over 11 m/s, the airflow exchange is enhanced by air curtain at the plant opening, resulting in higher energy consumption from air leakage for dehumidification.

Numerical Simulation of Indoor Thermal Environment Effected by Air Supply Temperature and Grille Angle on Stratum Ventilation in a Typical Office

Different indoor thermal environment was affected by the different supply air parameters. In this paper, the indoor temperature field and PMV value in the conditions of different supply air angles were studied to explore the influence of indoor thermal environment and human thermal comfort affected by the varied supply air angles. The experimental results showed that the average temperature of indoor air and the temperature gradient of personnel main activity area increased with increasing the supply air angel. In contrast, a relatively comfortable indoor thermal environment could be formed with the supply air angel between 0°to 15°.

Critical velocity of active air jet required to enhance free opening rectangular exhaust hood