• Title/Summary/Keyword: Ventilation rates

Search Result 222, Processing Time 0.02 seconds

An Experimental Study on Air Leakage and Heat Transfer Characteristics of a Rotary-type Heat Recovery Ventilator (회전식 폐열회수 환기유닛의 공기누설 및 전열특성에 관한 실험적 연구)

  • Han Hwataik;Kim Min-Kyu
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.16 no.12
    • /
    • pp.1197-1203
    • /
    • 2004
  • This study investigates the air leakage and heat transfer characteristics of a rotary-type air-to-air heat exchanger with a fiber polyester matrix. The leakage airflow rate is measured using a tracer gas method for various ventilation rates and rotational speeds of the matrix wheel. A correlation equation for air leakage is obtained by combining the pressure leakage and the carryover leakage. The pressure leakage is observed to be a function of ventilation airflow rate only, and the carryover leakage is found to be a linear function of rotational speed. The real efficiency of the heat exchanger can be obtained from its apparent efficiencies by taking into account the air leakage ratio. As the ventilation rate increases, the heat recovery efficiency decreases. As the rotational speed of the matrix increases, the efficiency increases initially but reaches a constant value for the rotational speeds over 10 rpm.

Numerical Study on Improvement of Storage Environment of Igloo-Shaped Magazine Using Forced Ventilation (강제환기를 적용한 이글루형 탄약고 저장환경 개선에 관한 수치적 연구)

  • Yoon, Hae-Deun;Kim, Seong Hoon
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.24 no.1
    • /
    • pp.99-106
    • /
    • 2021
  • This study explores the improvement of storage environment of igloo-shaped magazine using forced ventilation. Conjugate heat transfer analysis of forced convection and conduction are performed to calculate the flow, temperature, and relative humidity field in igloo-shaped magazine. Through the conjugate heat transfer analysis, the effects of inlet vent, volume flow rates of jet, and jet angles on the condensation and relative humidity are numerically investigated. The area of condensation in igloo-shaped magazine and relative humidity at the surface of ammunitions are then calculated.

The Analysis on the Variation of the Ventilation Rates by Wind Pressure and Temperature Difference between Indoor and Outdoor in the Multi-Story Type Double Skin Facade applied to the Office Building (오피스 건물에 적용된 다층형 이중외피의 풍압과 실내·외 온도차에 의한 환기량 변화 분석)

  • Song, Chi-Ho;Kim, Teayeon;Leigh, Seung-Bok
    • KIEAE Journal
    • /
    • v.15 no.2
    • /
    • pp.123-131
    • /
    • 2015
  • Purpose : Improvement of indoor thermal comfort and reduction of the energy consumption in building can be obtained by applying a double skin facade system. In order to achieve effectively this purpose, design team would have to perform easy and appropriate performance analysis for making better design decision during the design process. Method : This paper focus on the natural ventilation performance of a multi-story type double skin facade with main causes which are pressure difference according to the wind and temperature difference between indoor and outdoor (Buoyancy Effect). Using this main causes, the natural ventilation ratio of wind effect-to-buoyancy effect in cavity of multi-story type double skin facade were analyzed through the performance analysis results of CFD (Computational Fluid Dynamics) simulation. Result : When the wind velocity was 2m/s, the ventilation rate in the cavity was highest. If wind velocity was slower than 2m/s wind velocity, buoyancy effect has more influence on the ventilation rate in the cavity, and if wind velocity was faster than 2m/s wind velocity, wind effect has more influence on the ventilation rate in the cavity.

A computational study on the removal of the non-isothermal concentrated fume from the semi-enclosed space

  • Chang, Hyuksang;Seo, Moonhyeok;Lee, Chanhyun
    • Environmental Engineering Research
    • /
    • v.22 no.2
    • /
    • pp.216-223
    • /
    • 2017
  • For the prediction of the ventilation rate for removing the non-isothermal concentrated fume from the semi-enclosed space, the computational fluid dynamics (CFD) analysis was done. Securing the proper ventilation conditions in emergency state such as in fire is crucial factor for the protection of the resident in the space. In the analysis for the determining the proper ventilation rate, the experimental study had the limitation for simulating the versatile conditions of fume development. The theoretical and computational method had been chosen as the alternate tool for the experimental analysis. In this study, the CFD analysis was done on the defined model which already had been done the experimental analysis by the previous workers. By comparing the prediction on the plume heights and the ventilation rates by the CFD analysis at, and in the parametric model of $1m^3$ with those of the previous experimental works, the feasibility of the computational analysis was evaluated. For the required ventilation rate analyzed by the CFD analysis was over predicted in 7.1% difference with that of the experimental results depending on the different plume height. With the comparison with the analytical Zukoski model at, the CFD analysis on the ventilation was under predicted in 8.3%. By the verification of the feasibility of the CFD analysis, the extended analysis was done for getting the extra information such as the water vapor distribution and $CO^2$ distribution in the semi-enclosed spaces.

An Experimental Study Improving Ventilation of Container Ship Hold Using Horizontal Upward Jet Duct (수평 상향 분사 덕트를 이용한 컨테이너선 화물창 환기 개선에 대한 실험적 연구)

  • Park, Il-Seouk;Park, Sang-Min;Ha, Ji-Soo
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.43 no.2 s.146
    • /
    • pp.236-245
    • /
    • 2006
  • The ventilation performance for the various venting duct arrays has been experimentally compared in the scaled model of the container hold. Most container ships have the ventilation duct system to remove effectively the condensing heat released from container refrigerator. The existing duct system is vertically installed and basically has the number of duct as many as the columns of reefer container stack. In this study, to make up for the weak points having stagnantly hot legions in the centered area of container hold for the present system, the horizontal upward jotting duct system was proposed and proved by temperature rising tests on the scaled model. In this paper, the expected flow regimes and the thermal and hydrodynamic analogies as well as the measured temperature distributions in a hold for various duct types and heat released rates are deeply discussed.

Analysis of the efficiency of natural ventilation in a multi-span greenhouse using CFD simulation (CFD 시뮬레이션을 이용한 연동형 온실 내 자연환기의 효율성 분석)

  • Short, Ted H.
    • Journal of Bio-Environment Control
    • /
    • v.8 no.1
    • /
    • pp.9-18
    • /
    • 1999
  • Natural ventilation in a four and one-half span, double polyethylene commercial greenhouse was investigated with actual data collected at Quailcrest Farm near Wooster, Ohio. Moreover, a computational fluid dynamics (CFD) numerical technique, FLUENT V4.3, was used to predict natural ventilation rates, thermal conditions, and airflow distributions in the greenhouse. The collected climate data showed that the multi-span greenhouse was well ventilated by the natural ventilation system during the typical summer weather conditions. The maximum recorded air temperature difference between inside and outside the greenhouse was 3.5$^{\circ}C$ during the hottest (34.7$^{\circ}C$) recorded sunny day; the air temperatures in the greenhouse were very uniform with the maximum temperature difference between six widely dispersed locations being only 1.7$^{\circ}C$. The CFD models predicted that air exchange rates were as high as 0.9 volume per minute (A.C. .min$^{-1}$ ) with 2.5m.s$^{-1}$ winds from the west as designed.

  • PDF

Predicting Mortality in Patients with Tuberculous Destroyed Lung Receiving Mechanical Ventilation

  • Kim, Won-Young;Kim, Mi-Hyun;Jo, Eun-Jung;Eom, Jung Seop;Mok, Jeongha;Kim, Ki Uk;Park, Hye-Kyung;Lee, Min Ki;Lee, Kwangha
    • Tuberculosis and Respiratory Diseases
    • /
    • v.81 no.3
    • /
    • pp.247-255
    • /
    • 2018
  • Background: Patients with acute respiratory failure secondary to tuberculous destroyed lung (TDL) have a poor prognosis. The aim of the present retrospective study was to develop a mortality prediction model for TDL patients who require mechanical ventilation. Methods: Data from consecutive TDL patients who had received mechanical ventilation at a single university-affiliated tertiary care hospital in Korea were reviewed. Binary logistic regression was used to identify factors predicting intensive care unit (ICU) mortality. A TDL on mechanical Ventilation (TDL-Vent) score was calculated by assigning points to variables according to ${\beta}$ coefficient values. Results: Data from 125 patients were reviewed. A total of 36 patients (29%) died during ICU admission. On the basis of multivariate analysis, the following factors were included in the TDL-Vent score: age ${\geq}65$ years, vasopressor use, and arterial partial pressure of oxygen/fraction of inspired oxygen ratio <180. In a second regression model, a modified score was then calculated by adding brain natriuretic peptide. For TDL-Vent scores 0 to 3, the 60-day mortality rates were 11%, 27%, 30%, and 77%, respectively (p<0.001). For modified TDL-Vent scores 0 to ${\geq}3$, the 60-day mortality rates were 0%, 21%, 33%, and 57%, respectively (p=0.001). For both the TDL-Vent score and the modified TDL-Vent score, the areas under the receiver operating characteristic curve were larger than that of other illness severity scores. Conclusion: The TDL-Vent model identifies TDL patients on mechanical ventilation with a high risk of mortality. Prospective validation studies in larger cohorts are now warranted.

Analysis on the installation criteria and ventilation effect for round roof windows in single-span plastic greenhouses (단동 플라스틱 온실의 천창 환기효과와 설치기준 분석)

  • Nam, Sang-Woon;Kim, Young-Shik;Ko, Gi-Hyuk;Sung, In-Mo
    • Korean Journal of Agricultural Science
    • /
    • v.39 no.2
    • /
    • pp.271-277
    • /
    • 2012
  • Dimensions, operation conditions and improvement items for round roof windows were investigated in arch shape single-span plastic greenhouse with roof vents, and natural ventilation performance was analyzed based on the ventilation theory. Diameter of round roof windows was mostly 60 cm, and chimney height projected on roof was average 30 cm. Installation space was mostly 5 to 6 m but farmhouse of 10 m and over was 16.7% also. A round roof window which has 60 cm diameter was installed to 6 m space generally and 80 cm diameter was installed to 10 m space, but correct standards did not exist. There were a lot of opinions that ventilation effect of round roof windows is fairly good and user satisfaction is generally excellent. It is problem that there is few effects in summer and that vinyl around each vent tears well and rainwater leaks, and improvement hope item required development of automatic control system. In the wind speed of 0.3 m/s, it was estimated that natural ventilation rates were 0.69, 0.55, 0.50 and 0.48 volumes per minute in case of 2, 4, 6 and 8 m installation space for round roof windows, respectively. It was analyzed that the ratio of ventilation due to buoyancy out of total ventilation were 65.2, 41.9, 29.9 and 22.8% in case of 2, 4, 6 and 8m installation space, respectively. By the round roof windows installed at space of 6 m, ventilation rate was estimated to 0.5 volumes per minute, and we can expect the increase in ventilation rate of 30%. In order to meet the recommended ventilation rate for summer season, we have to install the round roof windows at space of 1 to 2 m. However, it is difficult to apply those installation space because of falling productivity due to lower light transmittance as well as rising costs. It is estimated that the installation space of 6m is appropriate for spring or fall season. Therefore it is necessary to encourage installing the roof windows in single-span plastic greenhouses.

Evaluation of Natural Ventilation Performance for Multi-span Plastic Greenhouses (다연동 플라스틱 온실의 자연환기성능 평가)

  • Nam, Sang-Woon;Kim, Young-Shik;Seo, Dong-Uk
    • Journal of Bio-Environment Control
    • /
    • v.22 no.1
    • /
    • pp.7-12
    • /
    • 2013
  • Environmental measurements in the many different types of horticultural farms were carried out to evaluate the ventilation performance for multi-span plastic greenhouses according to the eaves height, the number of spans, the existence of side wall vents and the position of roof vents. Hydroponic tomatoes were being cultivated in all experimental greenhouses, and ventilation rates of the greenhouses were analyzed by the heat balance method. It showed that the ventilation rate in the greenhouse with 4 m eaves height increased about 22% compared to the greenhouse with 2 m eaves height. The ventilation rate in the greenhouse with 9 spans decreased about 17% compared to the greenhouse with 5 spans. In the greenhouse with 9 spans, if there were no side wall vents, the ventilation rate showed about a third of the case that side wall vents were open. Overall, as the eaves height was higher and the number of spans was smaller in multi-span greenhouses, the natural ventilation performance was better. And the ventilation performance was best in the greenhouse which the eaves height was high and the position of roof vents was ridge, not gutter. Therefore, in order to maximize the natural ventilation performance, multi-span plastic greenhouses need to improve their structures such as that make the eaves height higher, place the roof vents on the ridge, install the side wall vents as much as possible, and the number of spans is limited to about 10 spans.