• 설비공학논문집
• /
• 제12권5호
• /
• pp.476-485
• /
• 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.

• 설비공학논문집
• /
• 제11권5호
• /
• pp.669-683
• /
• 1999

Heat dissipation in the domestic switching room has been gradually increased. Therefore, numerical study on the cooling characteristics of the telecommunication system in a switching room for three kinds of the air supply and return flow system was investigated to develop effective flow system. As a result, the cooling performance of the under floor air supply and overhead return flow system was the best.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제9권4호
• /
• pp.37-46
• /
• 2001

This study numerically investigates thermal comfort of a space cooled by a floor-supply air-conditioning system, in which three different combinations of supply and return locations, one floor-supply/ceiling-return and two floor-supply/floor-return, are treated. A complementary experiment is performed 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 a diffuser is developed for efficient simulations. The calculated results show that the ceiling-return type is far better in terms of 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 considerations.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 동계학술발표대회 논문집
• /
• pp.434-439
• /
• 2008

Dome stadiums give thermal unpleasant feeling to occupants because of the radiant heat and the indoor and outdoor haet exchange from roogs or lightweight building envelopes of sidewalls. This study analyzed the indoor temperature and velocity distribution according to various air supply and return sustems in dome stadiums in summer.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.866-871
• /
• 2006

Recently according to the fashion of well-being, the case study of under floor heating system type for residential space is increasing. Specially double slab floor system can make several roles as reducing the acoustic noises and also supplying fresh air through the gap. So in present study floor heating performance was examined with various location of the space in the case of floor supply air and ceiling supply air. In both cases return air went out through ceiling opening. As one of the result is that when using the heat pipe type floor heating system the temperature difference between supply and return water was $15.2^{\circ}C$, but in case of commercial type floor heating system the temperature difference was $5.3^{\circ}C$ when the supply water temperature was $50^{\circ}C$.

• 대한설비공학회지:설비저널
• /
• 제10권4호
• /
• pp.304-315
• /
• 1981

This paper presents, the result of the study for the fluctuant temperature of the out-side air adopting the heat pump system in seoul, Taejean, Taegu, Busan and Jejeu among principle cities in korea for the purpose of checking the heating capacity, Heat pump capacity (outlet capacity), Coefficient of performance and running cost in comparison with the supporting the energy for the boiler's operation. According to the supply temperature changes of the out door coil by the out side air-return air mixing ratio, the Coefficient of performance is increased from 3. 1 to 5.0. Particularly, in Taegu, it is necessary to adopt the heat pump system against the supplement heat supply on the full outside air intake in January of the heating period, and it was recognized that the running cost is cheaper than that of the Boiler use. At the same time, if it is able to get $25\%$ of return air of the inside in the Seoul, it could be saved its costs when we use the supplementary boiler. And I think it is necessary to the development.

• 설비공학논문집
• /
• 제18권12호
• /
• pp.999-1006
• /
• 2006

A study of temperature profiles in mixing zone of AHU (air handling unit) can contribute greatly to enhance performance of AHU system, so the study on the temperature distribution between RA (return air) and OA (outdoor air) is important to analyze the mixing characteristics in a mixing zone of AHU. Accordingly, the temperature profiles during RA (return air) and OA (outdoor air) supply process into mixing zone of AHU with an air mixer are studied experimentally. The effect of air mixer, OA temperature and RA/OA flow rate are studied in detail. In this study, the results show that the mixing efficiency is all high for installed the air mixer. The more OA temperature increase and OA flow rate decrease, the more mixing efficiency is high.

• 설비공학논문집
• /
• 제29권4호
• /
• pp.202-211
• /
• 2017

In this study, the exergy that can be reflected in the energetic and economic values was used to assess the heat tariff of a district heating (DH) system instead of the enthalpy. It is difficult to directly apply the exergy to the current heat-charge system because of the complicated calculation; therefore, the difference between the supply and return temperatures was converted to the exergy-temperature difference for the ease of the heat-amount calculation. As a result of the exergy analysis for a DH substation, the exergy-temperature difference did not affect the surrounding temperature and pressure loss. The supply temperature and the maximum difference between the supply temperature and the return temperature exerted the main effect on the exergy-temperature difference. The new heat charge of a DH user was slightly reduced in winter compared with the previous charge, but the heat charges in the other seasons are almost the same. It is concluded from the assessment of the heat tariff for which the exergy is used that this tariff is more feasible for both DH suppliers and consumers compared with enthalpy.

• 동력기계공학회지
• /
• 제9권4호
• /
• pp.11-17
• /
• 2005

This paper reports an experimental study on the performance evaluation of air-to-air heat exchanger with rotary type newly developed in this study. Air flow rate is varied from 10 to 120 m3/h. The range of RPM of the porous rotating discs mounted inside the heat exchanger unit is 0 to 50. The temperature of the return air side is set by adjusting heat supply at heater. The material of the porous rotating discs is cooper and its thickness is 1.0 mm. The heat transfer rate increased with the increase in air flow rate. It was found that the heat transfer rate, as the temperature of the return air side was increased, was improved due to higher temperature difference. The heat exchange performance increased with the increase in the temperature of the return air side at the conditions of the same RPM. The sensible heat exchange efficiency was maximum 68 to 76 percent, and enthalpy exchange efficiency 64 to 74 percent.

• 설비공학논문집
• /
• 제5권3호
• /
• pp.157-168
• /
• 1993

Pipe network of hot water heat supply system in an apartment house was analyzed. Flowrate and supply heat capacity of each household in which constant flowrate balancing valve is installed in a single zone system were calculated and the results were investigated. In the existing piping system, the non-uniformity of heat supply with floors due to the static pressure and temperature difference between supply main and return main can not be avoided and this tendency get intense with the increase of the height of building. The non-uniformity of heat supply can be prevented by the installation of balancing valve at each household, however if the performance of supply pump is not sufficient to overcome the energy loss due to the installation of balancing valve for constant flow rate or if the selection of the valve capacity is not adequate, the valves will may lose their controllability.