• Journal of the Korean Solar Energy Society
• /
• v.27 no.3
• /
• pp.127-133
• /
• 2007

Underfloor air distribution system is generally known to be more energy-saving and provide more comfort as compared with overhead air distribution system. In practice, however, some buildings to which underfloor air distribution system is applied have less effectiveness in saving energy and are getting dissatisfaction with cold draft caused by wind velocity of air distribution in terms of comfort. It is judged that such problems are due to failure to consider properties of underfloor air distribution system in applying it and identical design with the design standards for the existing overhead air distribution system. This study aims at introducing an air conditioning type of the occupied zone for underfloor all distribution system to see its effectiveness in saving energy for air conditioning of the occupied zone through a comparative simulation with the existing air conditioning type.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.340-345
• /
• 2007

The underfloor air distribution system has been attracting to architects and building owners as one of valuable system for the renovated and newly office building. In this paper, we discussed the thermal stratification profile of pressurized plenum underfloor air distribution(UFAD) according to indoor setting temperature, diffuser number, diffuser type. For this, the space of office building(H corp.) is selected for measuring the air volume of underfloor diffuser and vertical temperature profile. As a result, the thermal stratification profile is influenced by the number and type of the underfloor diffuser and thermal storage character of the underfloor. Whereas indoor setting temperature have a lower significant impact on thermal stratification.

• Journal of the Korean Society of Industry Convergence
• /
• v.16 no.2
• /
• pp.29-33
• /
• 2013

This study has been conducted to propose an optimal design guidance of underfloor air distribution system by examining air pattern and proper exhaust status of floor plenum using CFD (Computational Fluid Dynamics). Simulation shows deficient air pattern and exhaust status at BPG (Bypass Grille) of the current design. As a means to find an alternative design, four cases have been developed and tested. Case 1, 2 and 3 show similar results in comparison to the current design. However, case 4 shows improved air pattern and exhaust status at BPG(Bypass Grille), and has been chosen as the optimal alternative.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.12 no.4
• /
• pp.40-46
• /
• 2016

In order to improve air quality of indoor environment, studies of the underfloor air distribution (UFAD) system for application in buildings are actively in progress based on temperature and air flow distribution. However, although the age of air is the major evaluation parameter, there has been very little study on this parameter for the UFAD system. In this study, we investigated the age of air to reach the air diffuser, which is installed at the bottom of the interior by the UFAD system. Computational fluid dynamics simulations showed no regular pattern to the maximum value of the age of air in accordance with air flow rate and the velocity at air diffuser. These factors can be deduced from air movement by considering that air emitted from air conditioners was rotated according to the bottom shape of the floor, and then, the age of air in the rotation center was increased. The average age of air of internal interior was reduced considerably as the flow velocity at the underfloor air diffuser was increased from 0.5 m/s to 1.0 m/s However, the age of air was not substantially affected with change in the air volume. Moreover, when the flow velocity at the underfloor air diffuser was higher than 1.0 m/s, the age of air showed no significant difference with change in air volume or height of measurement. These results imply that indoor air quality is more substantially influenced by flow velocity than air volume, and the appropriate flow velocity is 1 m/s or more.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.5
• /
• pp.640-648
• /
• 1998

A numerical study has been conducted to investigate the effect of inflow supply air temperature and velocity on ventilation effectiveness in an underfloor air conditioning space. A low Reynolds number k-$\varepsilon$ model is implemented to calculate steady state turbulent velocity distributions. A step-down injection method is used to calculate local and room mean ages from transient concentrations based on the concept of the age of air. Results show that there is a significant effect of Archimedes number on ventilation effectiveness especially for cooling conditions. Reynolds number shows relatively minor effect on velocity distribution and ventilation effectiveness especially for isothermal and heating conditions. It can be concluded that underfloor air conditioning system provides good ventilation characteristics for cooling conditions because of temperature stratification in the space.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.10
• /
• pp.718-723
• /
• 2012

The purpose of this study is to propose modeling method of Underfloor Air Distribution System with reliability and validity by comparing characteristics of modeling methods. For this, the modeling methods of UFAD were selected by investigating various modeling methods of previous researches. Then, simulations were conducted by using EnergyPlus which is dynamic analysis program of building energy. Annual energy consumption for each method was compared with a wide range of indoor thermal loads. As a result, the methodology of reducing internal gains can cause under sizing of the system. It suggests modeling methods to reflect occupied zone air-conditioning, temperature stratification and supply plenum which are the main characteristics of UFAD.

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

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.826-831
• /
• 2006

In this paper, we discussed the energy performance of underfloor air distribution(UFAD) and overhead air distribution system according to outdoor air intake rates in a office building. For this, the laboratory(S lab.) is selected for measuring the thermal environments of UFAD system and overhead system. Based on the measured data, the TRNSYS simulation is used to evaluate the energy performance of UFAD system and the overhead system according to outdoor air intake rates. By increasing outdoor air intake rates from required outdoor air intake rates(100CMH) to maximum air intake rates, the energy savings of UFAD system comparing with overhead system are varied $15%{\sim}25.6%$ in summer, $12.8%{\sim}19%$ in fall/spring and not varied in winter(8%). As results of simulations on stratification height and cooling set temperature, the lower the stratification height and the higher cooling set temperature, the larger cooling energy savings of UFAD comparing with overhead system according to outdoor air intake rates.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2001.11a
• /
• pp.216-221
• /
• 2001

바닥급기 공조시스템은 재실자에게 신선외기를 효과적으로 공급하고 온열환경을 효과적으로 제공하기 위한 새로운 수단으로 시도되고 있다. 그러나 급기구가 인체에 너무 가까이 위치할 경우, 부분적인 열구배에 의한 불쾌감을 유발할 수 있다. 따라서 본 연구에서는 바닥급기 공조시스템이 설치된 공간내의 온도 및 기류분포 등의 온열환경을 측정하였고 적외선 카메라를 이용하여 급기구에 의한 인체 표면 온도를 측정하여 열적 쾌적성에 미치는 영향에 관하여 고찰하였다.

• Proceedings of the SAREK Conference
• /
• 2004.11a
• /
• pp.69-69
• /
• 2004