• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.51-59
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• 2007

The waste bunker usually consists of waste entrance zone and waste pit. In this paper, the distributions of air flow, $NH_3$ concentration and $H_2S$ concentration in a waste bunker were investigated to prevent an odor generated in a waste pit from dispersing to the waste entrance zone by numerical method. Four cases were considered such that 1) the waste incinerators is operated, 2) the waste incinerators is stopped, 3) the waste incinerator is operated and the direction of a supply diffuser is $45^{\circ}$ upward, 4) the waste incinerator is stopped and the direction of a supply diffuser is $45^{\circ}$ upward. In case of 1), the fresh air from the waste entrance zone is exhausted smoothly to the main exhaust grill of the waste pit. It means that an odor dispersion to the waste entrance zone will not occur. However in case of 2), the induction of fresh air is so small and the supply air with an odor in waste pit can flow to the waste entrance zone. Therefore, an odor will be dispersed to the waste entrance zone. This paper shows the solution that the supply diffuser with the direction of $45^{\circ}$ upward is chosen. As a result in case of 3) and 4), an odor dispersion to the waste entrance zone does not occurred and on odor is exhausted smoothly to the auxiliary exhaust grill.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.484-492
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• 2008

Air Discharge pattern and even temperature distribution is critical for a successful lower temperature air distribution system, which would supply lower temperature air than normal HAVC system. Selection of appropriate diffuser is the most critical element in completing lower temperature system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.2
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• pp.57-62
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• 2015

The objective of the present study is to identify the ventilation problems and to suggest the optimal ventilation system to save energy and to improve IAQ in the computer rooms, which annually performs the cooling operation by the server with the highly thermal load. Numerical results on the temperature and local mean age are presented along with some of the discharge velocities. Results show many interesting aspects of airflow patterns affecting the ventilation performances, according to the discharge velocity of the supply diffuser installed in the bottom surfaces between the servers. As the results, 2.5 m/s of the optimal discharge velocity is needed in order to improve the ventilation performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.7
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• pp.322-328
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• 2014

Return piping is used in a solar combi-system for heating and hot water supply. When the temperature of the lower side of a storage tank is low due to hot water usage, the returned hot water after heating is mixed with the lower side cold water of the tank, and the useful energy is reduced. We studied the degree of thermal stratification in the tank, using either a diffuser or a manifold to prevent mixing. Using the diffuser, mixing starts from the bottom of the storage tank. On the other hand, the manifold has the marked effect of preventing mixing. As a result of experiments with changing the diameter and number of holes in the manifold, the optimum condition is 8.5 mm diameter and 96 holes, under the condition of 0.3 lpm.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1715-1719
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• 2004

An in-house supersonic ejector was designed to ensure low pressure and high speed scavenging of resonating cavity of chemical lasers. For given primary flow condition, 100g/s secondary mass flow rate was observed at the design pressure. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of diffuser at the secondary inlet further reduced diffuser upstream pressure to 1/4-1/5 relieving the local to the primary supply unit. In order to increase the secondary flow, we put two ejectors capable of removing 50g/s each of secondary flows together to deal with higher mass flow. Test of the parallel unit demonstrated the secondary flow rate was proportional to the numbers of individual units that were brought together. Additionally, flow calculations with a commercial code were carried out in every case of experiment and compared with results.

• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.5-10
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• 2010

This study is concerned with effects of impeller blade thickness on performance of a turbo blower. This turbo blower is developed as an air supply system in 250 kW MCFC system. The turbo blower consists of an impeller, two vaneless diffusers, a vaned diffuser and a volute. The three dimensional, steady state numerical analysis is simultaneously conducted for the impeller, diffuser and volute to investigate the performance of total system. To consider the non-uniform condition in volute inlet due to volute tongue, full diffuser passages are included in the calculation. The results of numerical analysis are validated with experimental results of thin blade thickness. Total pressure ratio, efficiency, slip factor and blade loading are compared in two cases. The slip factor is different in two cases and the comparison of two cases shows a good performance in thin blade thickness in all aspects.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.232-238
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• 2001

We fabricated micro-pump using stereolithography technology. The pump was fabricated using PZT for its drive and used non-movable valve of diffuser/nozzle concept. Size of the pump chamber is, $14mm{\psi}$, narrow hole of diffuser/nozzle is $0.5mm{\psi}$ and wide hole $1mm{\psi}$ and chamber depth is 1.2mm, respectively. We confirmed its operation at frequency 100Hz, supply voltage $90{\sim}250Vp-p$. As the result of the pump working measurement, when ethanol is used, the pressure head difference between inlet and outlet of the pump is about 53mm in the frequency of 100Hz, 200V of Vp-p.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.476-485
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• 2000

This study numerically investigates thermal comfort in a space cooled by the floor-supply air conditioning system, in which three different supply-return locations, one floor supply-ceiling return and two floor supply-floor returns, are treated. A complementary experiment is peformed to validate the present numerical analysis, and the prediction agrees favorably with the measured data. In the numerical procedure, a simplified model mimicking the inlet flow through the diffuser is developed for efficient simulations. The calculated results show that the ceiling return type is far better in thermal comfort than the floor return ones within the extent of this study, which seems to be caused by effective vertical penetration of the supply air against natural convection. It is also revealed that the arrangement of port locations in the floor supply-floor return system has insignificant effect on the cooling performance. For selecting a proper system, other characteristics including the heating performance should be accounted for simultaneously with the present estimation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.6
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• pp.232-241
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• 2016

Installing a ventilator for an apartment house composed of over 100 dwelling units was mandated in 2006 to improve indoor air quality. In the case of mechanical ventilators, the air change rate is kept stable, however 68% of dwellers do not operate their ventilator because of an increased electrical bill and noise. In the case of natural ventilators, the former problems are settled, but there are concerns about cold draught and an increase of heating/cooling cost. Authors are developing a heat recovery type natural ventilator which is a natural ventilator equipped with total heat recovery element, and it is expected that those problems of mechanical ventilator and natural ventilator are resolved by this. The combined type diffuser of this study is an under developed fit to the heat recovery type natural ventilator above. There are no standards to evaluate the performance for this type of diffuser. Due to this issue this study investigated the performance of the ventilation and maintained a thermal environment for the combined type diffuser by comparing it with existing diffusers. The results revealed that the performances of the combined type of diffusers showed different features from the existing ones, and was estimated to be high enough in the performances above.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.105-110
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• 2017

Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings. UFAD systems use the underfloor plenum beneath a raised access floor to provide conditioned air through floor diffusers that create a vertical thermal stratification during cooling operations. Thermal stratification has significant effects on energy, indoor air quality, and thermal comfort performance. The purpose of this study was to characterize the influence of a linear bar grille diffuser on thermal stratification in both interior and perimeter zones by developing Gamma-Phi based prediction models. Forty-eight simulations were carried out using a Computational Fluid Dynamics (CFD) technique. The number of diffusers, the air flow supply, internal heat gains, and solar radiations varied among the different cases. Models to predict temperature stratification for the tested linear bar grille diffuser have been developed, which can be directly implemented into dynamic whole-building simulation software such as EnergyPlus.