• KIEAE Journal
• /
• v.16 no.6
• /
• pp.13-19
• /
• 2016

Purpose: In this study, we examined outdoor air fraction using historical data of actual Air Handling Unit (AHU) in the existing building during intermediate season and analyzed optimal outdoor air fraction by control types for economizer. Method: Control types for economizer which was used in analysis are No Economizer(NE), Differential Dry-bulb Temperature(DT), Diffrential Enthalpy(DE), Differential Dry-bulb Temperature+Differential Enthalpy(DTDE), and Differential Enthalpy+Differential Dry-bulb Temperature (DEDT). In addition, the system heating and cooling load were analyzed by calculating the outdoor air fraction through existing AHU operating method and control types for economizer. Result: Optimized outdoor air fraction through control types was the lowest in March and distribution over 50% was shown in May. In case of DE control type, outdoor air fraction was the highest of other control types and the value was average 63% in May. System heating load was shown the lowest value in NE, however, system cooling load was shown 1.7 times higher than DT control type and 5 times higher than DE control type. For system heating load, DT and DTDE is similar during intermediate season. However, system cooling load was shown 3 times higher than DE and DEDT. Accordingly, it was found as the method to save cooling energy most efficiently with DE control considering enthalpy of outdoor air and return air in intermediate season.

• Fire Science and Engineering
• /
• v.24 no.4
• /
• pp.27-32
• /
• 2010

Recently, increases of population density due to the industrialization in the metropolitan cities has caused the high-density and integration of life environment. Then various high-rise buildings are constructed for accommodation. However, high-rise building fires can cause high casualties due to increases of smoke spread velocity through the vertical shaft. In this study, the new program based on the enthalpy conservation for analysis of energy transfer for smoke control system, CAU_ESCAP, was developed. CAU_ESCAP was validated by comparing with the result of ASCOS. The characteristic of smoke control was analysed by using CAU_ESCAP for high-rise building fires.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.545-551
• /
• 1997

As the cooling energy requirement in an office building increases due to the increased internal heat gains, the effort to minimize the energy consumption through efficient operation of existing HVAC systems will be beneficial. In this study, one of the energy conserving efforts in an office building, operational strategies of Economizer Cycle Control have been investigated through DOE-2.1E computer simulation. The findings can be summarized : 1) Economizer Cycle Control saves energy throughout the year, 2) Econo-Limit-T must be applied seasonally based on the outside and return air conditions, 3) use of Enthalpy control is more energy efficient than that of Temperature control.

• Journal of the Korean Society of Safety
• /
• v.26 no.4
• /
• pp.102-110
• /
• 2011

For decreasing of the casualties and designing of the smoke control systems in the ultra high-rise building, the programs for analysis of smoke control were developed for prediction of smoke spread and distributions of pressure and temperature in building fire situation. In this study, coupling algorithm between mass and enthalpy conservations was modified for improving the applicability of the CAU_ESCAP which program can consider the energy transfer. The fire situation in ultra high-rise building was applied by using the modified CAU_ESCAP. Results of pressure difference predicted by modified CAU_ESCAP are higher than results of ASCOS as stack effect is generated due to the increasing of stairway temperature. Moreover, theoretically, the result of the neutral plane is more accurate than the result of ASCOS, in fire situation of ultra high-rise building.

• Journal of Korean Society for Atmospheric Environment
• /
• v.12 no.4
• /
• pp.479-485
• /
• 1996

Volatile organic compounds are air pollutants exhausting from industrial process, evaporation of solvent, and so on. Most of VOCs are the combustible gas of low calorific value as it is diluted by air. The systems burning such a hazardous gas need to increase enthalpy in order to increase flame stability. In this study an incinerator with reciprocating flow in the honeycomb ceramic has been used for the experiment of VOCs control. By the reciprocating flow system, the enthalpy of combustion gas is effectively regenerated into the enthalpy increases of the combustible gas through the honeycomb ceramic, which provides a heat storage. The position of the reaction zone is strongly dependent on the parameters of mixture velocity and time frequency. Flame front is changed to the point where burning velocity is coincided with burning velocity in the honeycomb ceramic. In this system it is important that flame front should be located symmetrically at the center of honeycomb ceramic for the purpose of increasing the reaction rate at one point. Peak temperature becomes higher with decreasing time frequency, at which the flow direction is regularly reversed.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.8
• /
• pp.1262-1269
• /
• 2003

In this study, enzymes were investigated as an antistaling agent for a Korean rice cake. Thermograms by a DSC demonstrated that the gelatinization-onset temperature of the Korean rice cake was at its lowest temperature of 71.1$^{\circ}C$ with the GP (glucoamylase+pullulanase) treatment, followed by $\beta$-amylase and $\alpha$-amylase. The gelatinization peak temperature of the Korean rice cake with enzyme treatment was relatively lower compared to the control. Furthermore, the Korean rice cake with GP treatment showed the lowest peak temperature. Melting enthalpy of the Korean rice cake increased with the enzyme treatment, with $\beta$-amylase, followed by $\alpha$-amylase and GP. Melting enthalpy of the Korean rice cake with GP treatment was significantly lower compared to the $\beta$- and $\alpha$-amylase treatment. Recrystallinity in the case of GP treatment was also significantly lower than control. The range of Avrami exponent (n) was 0.90 ∼ 1.20 and the time constant of retrogradation (1/k) of the Korean rice cake crystalline decreased in the following order: GP, $\beta$-, $\alpha$ -amylase and control. Textural characteristics of the Korean rice cake with enzyme treatment differed greatly from that of control. The L＊ values of all the Korean rice cakes made without $\beta$-amylase decreased and the a＊ values were significantly different at p<0.05. The GP treatment altered the b＊ value toward blue color, whereas $\beta$-and $\alpha$-amylase changed to the direction to yellow color. In sensory evaluation, the Korean rice cake with enzyme treatment showed higher evaluation compared to control.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.7 no.1
• /
• pp.51-58
• /
• 2011

Due to enhanced sealing and insulation of buildings, extensive use of glasses for building envelopes and increased use of heat generating office equipments, energy consumption of modem buildings for cooling is steadily increasing. With outdoor air cooling(ODAC) system, cooling load can be reduced by exchanging indoor air with the cold outdoor air during spring and fall seasons. If ODAC is operated based only on temperature, total cooling load may virtually increase if the outdoor humidity is high. To overcome this problem, ODAC should be controlled based on enthalpy. In this work energy saving characteristics of enthalpy controlled ODAC is studied using dynamic simulation. The result shows that cooling load can be reduced by 27% by adopting ODAC.

• International Journal of High-Rise Buildings
• /
• v.6 no.1
• /
• pp.101-111
• /
• 2017

The objective of this study is to determine the effectiveness of a modified air-side economizer in improving indoor air quality (IAQ). An air-side economizer, which uses all outdoor air for cooling, affects the building's IAQ depending on the outside air quality and can significantly affect the occupants' health, leading to respiratory and heart disease. The Air Quality Index (AQI), developed by the US Environmental Protection Agency (US EPA), measures air contaminants that adversely affect human beings: PM10, PM2.5, SO2, NO2, O3, and CO. In this study, AQI is applied as a control for the operation of an air-side economizer. The simulation is analyzed, comparing the results between the differential enthalpy economizer and AQI-modified economizer. The results confirm that an AQI-modified economizer has a positive effect on IAQ. Compared to the operating differential enthalpy economizer, energy increase in an operating AQI-modified economizer is 0.65% in Shanghai and 0.8% in Seoul.

• Elastomers and Composites
• /
• v.19 no.1
• /
• pp.13-31
• /
• 1984

The purposes of this dissertation are to demonstrate that DSC theromoanaytical methods of vulcanization can provide useful informations on the vulcanization characteristics of industrial formulations and also provides the potential basis for a rapid and complete method of sulfur and vulcanizing accelerator analysis for quality control. The influences of those factors such as heating rate, scan temperature, vucanizing accelerator's type and concentration upon vulcanization exotherm in NR and NBR compounds in the presence of vulcanizing accelerators such as TMTD,MBTS,DPG,TMTM,CBS, and MBT were evaluated by means of DSC. In order to examine the credibility in the DSC method, the same samples which were used for DSC method were studied to compare the DSC results with the ODR (Oscillating Disk Rheometer) data. The results obtained were as follows 1. In the DSC dynamic experiments, the observed enthalpy results from vulcanization depends upon the heating rate; In the range of 2 to $20^{\circ}C/min$ of heating rate, as the heating rate was increased the enthalpy change was also increased. However, over the heating rate of $30^{\circ}C/min$ it was observed that the enthalpy change was decreased as the heating rate was further increased. Without regard to the change of enthalpy, tremendous instantaneous heat evolving was observed in the range of high heating rates. 2. For the samples which are added with various vulcanizing accelerators, the activation energies of vulcanization were as follows; 3. Regarding to the influences of vulcanizining accelerator's types upon the characteristics of vulcanization exotherm, NR and NBR compounds in the presence of thiuramsulphide compounds type accelerators such as TMTD, TMTM, were exhibited sharper and higher vulclanization exotherm than others. From the resuts of DSC thermograms which was distributed in even shape in the broad temperature range, it was clearly shown that the guanidine compounds type accelerator such as DPG acts as a delayed acting accelerator. 4. In the comparison of DSC and ODR results, the dependency of temperature in the cure rate and the observed conversions show good agreements between two results. 5. In the same curatives, by the comparison of glass transition temperatures, it was possible to predict relative values of maximum torques. Consequently, from the present studies, it is shown that the DSC thermoanalytical method can provide an alternate new method for rapid and complete quality control analysis of rubber industry.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.6
• /
• pp.250-254
• /
• 2011

NiO-AZO films were deposited on glass substrate by DC and RF magnetron co-sputtering system in pure $O_2$ gas without substrate heating during deposition. In order to control the chemical composition of the film, NiO target was supplied with constant RF power of 150 W and AZO target (doped with 2.98 at% aluminum) with DC power varied between 40 W to 80 W. Deposited NiO-AZO films were evaluated by structural and chemical analysis. With introducing AZO, XRD and XPS data reveal that NiO were supplied with more oxygen. these results could be strongly affected by the higher bond enthalpy of NiO compared to ZnO, which makes it possible for NiO to obtain excessive oxygen from ZnO.