• Architectural research
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• v.19 no.3
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• pp.71-77
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• 2017

Dynamic pricing refers to a system in which a tariff varies, according to a level of charging and applied time depending on time change. The power billing system used in the Korean Electric Power Corporation (KEPCO) is based on time of use (TOU) pricing, which is one of the dynamic pricing systems. This paper aimed to determine the operational results of a variable refrigerant flow system, to which a new control algorithm was applied, in order to respond to dynamic pricing, in summer and the utility of the new control. To do this, real measured data was acquired from a VRF system installed in a building for educational purposes, where dynamic pricing was applied for about 100 days during summer time. At the maximum load operation time period in TOU, the new control minimized operation within the indoor comfort range, an increase in refrigerant evaporation temperature in the indoor unit and the number of revolutions in a compressor in the outdoor unit was limited. As a result, power usage was decreased by 11%, and the operational cost by 14.6%. Furthermore, measurement results using the Predicted Mean Vote (PMV) model, that represented satisfaction of thermal environment, showed that 82.8% to 90.4% of the occupants of the building were satisfied during operation when the new control was applied.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.4
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• pp.385-395
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• 2015

This study evaluated indoor environmental characteristics in an office room equipped both with ventilation window system and central cooling system. Fresh air is supplied only by the central cooling system whereas indoor air is discharged outside through both ceiling diffuser and a ventilation window system. Numerical study is conducted by changing the volumetric flow rates of exhaust ports of each system. For estimating the performance of this coupled system, $CO_2$ concentration and Predicted Mean Vote (PMV) were calculated using Computational Fluid Dynamics (CFD) simulation. The more the ceiling diffuser exhausts indoor air, the more the $CO_2$ concentration decreases. However, when the ventilation window system exhausts more indoor air, thermal comfort level gets improved in the office room with cooling system. Therefore, when the ventilation window system is operated, the coupled operation with central cooling system should be considered for enhancing indoor air quality and thermal comfort, together.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.430-440
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• 2011

The purpose of this study was to investigate the interactions between the thermal factors in existing thermal control methods and to find out the control logic that can create more comfortable thermal conditions. For it, four thermal control logics were developed：conventional temperature-based control; temperature-based and humidity-based control; PMV-based control; and TS-based control. Their performance was comparatively tested in the U.S. typical 5-story office building in two climate zones (Detroit, Michigan and Miami, Florida) for two seasons (winter and summer) incorporating IBPT (International Building Physics Toolbox) and Matlab/Simulink. Analysis on the thermal conditions and energy efficiency revealed that each control logic created comfortable conditions for their respective target, i.e., temperature, humidity, PMV or TS, but uncomfortable for others (e.g., temperature-based control logic maintained PMV or TS uncomfortably or vise versa). In addition, energy efficiency was significantly different by logics. In conclusion, it can be said that the overall thermal comfort can be improved by the adoption of the PMV and TS as a target variable and their economical benefits are expected in the hotter climate zones with the reduced cooling and dehumidifying energy consumptions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.57-66
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• 2006

The experimental and the numerical study was performed on the comparison of thermal comfort(TC) and indoor air quality(IAQ) in the lecture room for cooling loads when the operating conditions are changed. PMV value and $CO_2$ concentration of the lecture room were measured and compared with the numerical results. The numerical results showed a good agreement with the experimental one and then the numerical tool was used to analyze thermal comfort and IAQ for a couple of operating conditions. As a result it was found that the increment of the discharge angle of system air-conditioner makes TC uniformity worse, but rarely affects IAQ. Also TC and IAQ were hardly affected by the variation of the discharge airflow. Finally it turned out that TC is merely affected by the increment of the ventilation airflow, but the average $CO_2$ concentration can be satisfied with Japanese IAQ standards of classrooms when the ventilation airflow is more than $800m^3/h$ in this study.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.318-328
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• 2003

Numerical simulation using computational fluid dynamics (CFD) is performed to calculate the velocities and temperature profiles of air in adjacent to a worker within the individual local air conditioning system. The calculation domain is the space of ㄴ between walls and a worker in the climate room. The fresh air is supplied from the three different inlets located on the right, left and center wall in the climate room. In this study, the calculated data of velocities and temperature profiles of air in the nearest the skin of a worker are used to calculate the PMV (Predicted Mean Vote) for evaluation of thermal comfort of a worker in the local air conditioning system. Because the data of veto-cities temperature profiles of air in adjacent to a worker and the PMV of a worker are the design parameters of the local air conditioning system. The results of calculation show that the fresh air velocity and injection position are closely related to the PMV value. In individual air condition system of ㄴ, the appropriate PMV are obtained when the fresh air velocity and position are 1.0 m/s, throat of a worker and are 1.5 m/s, head of a worker, respectively. The method of numerical calculation is effective to obtain the optimum velocity and position of the fresh air for optimum the PMV and energy saving in individual local air conditioning system.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.590-595
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• 2009

PMV and ADPI were numerically investigated in a large space of various ceiling height with air-conditioning systems of two type. The numerical results showed that it is small that the growth of cooling load according to ceiling height rise in a large space without windows. In case of system air-conditioner of duct type embedded in the ceiling, the air mixing effect in indoor is superior to a case installed 4way cassette type in it. For controling thermal comfort at indoor, a system air-conditioner of duct type embedded in the ceiling is little influenced according to ceiling height rise in a large space considered.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.399-409
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• 2006

This paper presents a novel method for satisfying the thermal comfort of indoor environment and reducing the summer peak demand power by minimizing the power consumption for an Air-conditioner within a space. Korea Electric Power Corporation (KEPCO) use the fixed duty cycle control method regardless of the indoor thermal environment. However, this method has disadvantages that energy saving depends on the set-point value of the Air-Conditioner and direct load control (DLC) has no net effects on Air-conditioners if the appliance has a lower operating cycle than the fixed duty cycle. In this paper, the variable duty cycle control method is proposed in order to compensate the weakness of conventional fixed duty cycle control method and improve the satisfaction of residents and the reduction of peak demand. The proposed method estimates the predict mean vote (PMV) at the next step with predicted temperature and humidity using the back propagation neural network model. It is possible to reduce the energy consumption by maintaining the Air-conditioner's OFF state when the PMV lies in the thermal comfort range. To verify the effectiveness of the proposed variable duty cycle control method, the case study is performed using the historical data on Sep. 7th, 2001 acquired at a classroom in Seoul and the obtained results are compared with the fixed duty cycle control method.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.135-140
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• 2005

Installation of ceiling type unit is achieved by one of efforts for agreeable classroom environment embodiment along with economic growth. But research about changing the position of ceiling type unit is lacking in present. Therefore, this thesis is to study the thermal environment of 5 different position cases of ceiling type, namely Case A, B, C, D, E. Here, Case C is the case that has the position of ceiling type center of the classroom and the other 4 alternatives are 0.7 m away from the Case C according to x and z axis. In this thesis temperature distributions, air current distribution, heat amenities such as PMV of occupants are analyzed as the environmental factors. Through these factors, Case C and Case D are the better position alternatives than the alternatives of Case A, Case B and Case E because the latter cases the air current reaches directly to indoor occupants so that occupants feel chilly. This thesis has a conclusion under the condition of only one inlet air temperature and seat arrangement. But afterwards more inlet air condition and seat arrangement must be considered.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1213-1219
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• 2008

This experimental study was to analyze thermal comfort and indoor air quality(IAQ) with ventilation and humidification in the classroom when system air conditioner was operated. The thermal comfort was estimated by the PMV index and the concentration of $CO_2$ and total suspended particle(TSP) were measured and compared with ventilation and humidification. As a result, the class room temperature distribution was $2{\sim}5^{\circ}C$ low during operating ventilation system and humidification. At 60% RH, PMV values of measuring points were ranged from +0.5 to -0.5 indicating optimal the range of thermal comfort. The average concentration of $CO_2$ gas and TSP were reduced 645 ppm, 0.17 mg/$m^3$ respectively, during operating the ventilation system. From the results, to maintain comfortable environment in the heated classroom, the ventilation and humidification were needed in winter season.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.870-878
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• 2003

The maintenance of thermal equilibrium between the human body and its environment is one of the primary requirements for health, wellbeing and comfort. For the effective control of indoor thermal environment, thermostat or humidistat is used. But, it is not sufficient to control the indoor thermal environment using only one or two parameters as human response for the indoor comfortable environment. So an environmental thermal index is required for the control of indoor thermal environment effectively. In this study, a PMV sensor has been developed which has integrated from various kinds of individual sensors for temperature, humidity, air velocity, radiant temperature. After applying the PMV and PPD equation, it is possible to monitor the indoor thermal environment with the sensor system, which is adopted to the circuit for optimization according to the human response with the metabolic rate and activities. The measurement was carried out to verify the performance of the integrated sensor system in comparison with existing measurement system, the PMV meter. As a result, the possibility of applying the PMV sensor to control the indoor thermal environment simultaneously was examined.