• 설비공학논문집
• /
• 제26권4호
• /
• pp.145-150
• /
• 2014

Many studies are being conducted with the aim of reducing the energy consumption in data centers, which are one of the highest consumers of energy. The use of an air-side economizer system that uses external air during intermediate and winter seasons is being considered for reducing the energy consumption of air conditioners. In this study, using the energy simulation, we evaluated the energy performance of a central chilled water cooling system and air-side economizer system in domestic data centers. Further, the cost-effectiveness of the air-side economizer was analyzed through Life-Cycle Cost Analysis. The results showed that with the use of air-side economizer systems, the energy costs increased as the applied filter grade increased; however, unlike existing central chilled water systems, it would break even within 2 years.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제17권1호
• /
• pp.15-24
• /
• 2009

The energy usage and the economical feasibility of the typical two story office building in the three urban locations of South Korea are evaluated as the eight orientations. The smallest energy consume is shown at the true south. The ranges of the low energy consume are $-3l5^{\circ}{\sim}0^{\circ}\;and\;-135^{\circ}{\sim}-180^{\circ}$. There are obvious advantages of passive solar designs such as using a fully glazed facade at the true south in the building. The General Low voltage plan is the effective way for the office building when does not required the high voltage electricity. The energy cost of KEPCO is compared to that of XCEL ENERGY. The portion of the customer charge of XCEL ENERGY is about 10% but it is about 50% of the total tariff of KEPCO. The effective way to save the energy cost is by reducing the operating energy of XCEL ENERGY plane but the most effective way is reduce the contracting energy of KEPCO plane.

• 설비공학논문집
• /
• 제23권8호
• /
• pp.571-579
• /
• 2011

Heat pump systems for commercial building with variable refrigerant flow(VRF) are expanding a market due to high energy efficiency, lower maintenance cost and easy installation comparing with the conventional heat pump with the constant refrigerant flow. In general, heat pump systems degrade the energy efficiency in the extremely low temperature regions. In this study, VRF heat pump system with refrigerant heating is experimentally investigated to overcome the low heating performance in the extremely low temperature regions. VRF heat pump system with refrigerant heating is found out the sufficient heating performance in the -25 degree temperature condition comparing with the conventional heat pump system and is obtained more than 2,500 kPa high pressure in the evaporator at low temperature.

• 설비공학논문집
• /
• 제24권2호
• /
• pp.121-128
• /
• 2012

Improvement in the energy efficiency has been studied of the desiccant cooling system by applying a vapor compression type heat pump to modify the system into a hybrid system. The cycle simulation was performed and the results were compared between a reference desiccant cooling system composed of a desiccant rotor, a sensible rotor and a regenerative evaporative cooler, and a hybrid desiccant cooling system with the sensible rotor being replaced by a heat pump. Though the electric consumption increases as much as the compressor power consumption, the total cooling capacity increases and the thermal energy input decreases by the addition of the heat pump. Therefore, the total energy efficiency can be improved if the increase in the electric consumption can be compensated with the increase in the cooling capacity and the decrease in the thermal energy input. The results showed that the total energy efficiency is optimized at a certain heat pump capacity. When the heat from the CHP plant is used for the thermal energy input, the energy consumption of the hybrid system is reduced by 20~30% compared with the reference system when the heat pump shares 30~40% of the total cooling capacity.

• 설비공학논문집
• /
• 제21권11호
• /
• pp.591-598
• /
• 2009

The service quality with the various building equipments tends to depend on the individual superintendent's capability and efforts generally and this often lead to poor maintenances and managements of them. N-BMS(Networked Building Management System), proposed in this study, is a new type of building management method, which links principal equipments within many buildings into a communication network and carries out several significant missions such as fault detection, deterioration diagnosis and control the equipments and so on, as well as monitoring which is the main and unique purpose of the conventional BMS. How to construct the N-BMS was considered to keep performance of equipments high and thus to save energy and resource. LCC(Life Cycle Cost) based analysis was also performed in order to verify the effects of some maintenance and management works for the building HVAC systems.

• 설비공학논문집
• /
• 제20권7호
• /
• pp.486-491
• /
• 2008

The performance of a microturbine CHP system equipped with an absorption chiller was analyzed by modeling it. The microturbine with recuperator was simulated with the Brayton cycle model. The mass flow rate and available heat energy of the exhaust gas from the microturbine were simulated. These results were utilized as input values for the generator of the absorption chiller. The absorption chiller is a single-effect air cooled type with a solution heat exchanger. The heat input into the generator was proportional to the heat transfer rate and the UA values of the heat exchangers of the absorption chiller. Furthermore, the COP of the absorption chiller increased with respect to an increase of the heat input into the generator, under the sufficient evaporator capacity condition. When the capacity of the CHP system increased from 30 to 60 kW, the mass flow rate of the LiBr for the absorption chiller doubled, and the UA values for evaporator and condenser increased by factors of x3.9 and x3.4, respectively, under the same COP condition.

• 설비공학논문집
• /
• 제18권7호
• /
• pp.535-540
• /
• 2006

This study was performed In evaluate sleep efficiencies and conditions for comfortable sleep based on the analysis of Physiological signals under variations in thermal conditions. Five female subjects who have similar life cycle and sleep patterns were participated for the sleep experiment. It was checked whether they had a good sleep before the night of experiment. EEGs were obtained from C3-A2 and C4-A1 electrode sites and EOGs were acquired from LOC (left outer canthus) and ROC (right outer canthus) for REM sleep detection. Sleep stages were classified, then TST (total sleep time), SWS (slow wave sleep) latency and SWS/TST were calculated for the evaluation of sleep efficiencies on thermal conditions. TST was defined as an amount of time from sleep stage 1 to wakeup. SWS latency was from light off time to sleep stage 3 and percentage of SWS over TST was calculated for the evaluation of sleep quality and comfort sleep under thermal conditions. As result, the condition which raise a room temperature provided comfortable sleep.

• 설비공학논문집
• /
• 제24권7호
• /
• pp.585-590
• /
• 2012

The objective of this study is to investigate the performance of a two-stage compression heat pump system for district heating. The experimental setup of heat pump consists of compressor, condenser, evaporator, expansion device, intercooler, flash tank, oil separator and accumulator. The experimental evaluations on the two-stage compression cycle were carried out under various operating conditions which were heat source temperature, the degree of compressor inlet superheat, and intermediate pressure. The temperature ranges of unutilized energy as the heat source were used in the test conditions. As the heat source temperature increased from $10^{\circ}C$ to $30^{\circ}C$, the COP and heating capacity of the heat pump system increased by 22.6% and 45.8%, respectively. The performance of the two-stage heat pump system increased by 5.2% with the variation of the intermediate pressure in the same heat source temperature conditions.

• 설비공학논문집
• /
• 제20권5호
• /
• pp.295-303
• /
• 2008

The objectives of this study are to predict actual system performance and effective operating range of the 2-stage compression heat pump system using river water. An electronic expansion valve was applied to the simulation to analyze the effects of operating conditions on the system performance. The developed program was verified by comparing the predictions with the measured data. The results from the present model showed a good agreement with the measured data. In addition, the heat pump simulation was conducted by increasing condenser reservoir inlet temperature to investigate the benefits of the 2-stage compression over the 1-stage compression in the heating mode. The performance of the 2-stage compression cycle was better than that of the 1-stage compression when the inlet temperature of the condenser reservoir was higher than $40^{\circ}C$.

• 설비공학논문집
• /
• 제17권12호
• /
• pp.1204-1209
• /
• 2005

In-situ measurement was made to evaluate chiller performance and thermal storage density of an ice thermal storage system. The system belonged to a big hotel and the measurement was conducted during late October. Owing to very small cooling load, the data logging was possible for a single thermal storage cycle. However, operation history of the chiller showed a relatively good spectrum of data for performance evaluation. COP and thermal storage density were calculated. The COP at full load was about 4.07, which was lower than $4.8\~6.4$ of new chillers. The measured storage density was about $10.9RT-h/m^3\;(=152MJ/m^3)$, which also was lower than a criterion of normal performance $(above\;13.0RT-h/m^3\;or\;181MJ/m^3)$. The study result provides technical basis for quantitative ESCO business scenario.