• 설비공학논문집
• /
• 제22권12호
• /
• pp.873-880
• /
• 2010

The present study developed a computer simulation program to determine the optimum strategy and capacity of a micro combined heat and power(CHP) system. This simulation program considered a part-load electrical/thermal efficiency and transient response characteristics of CHP unit. The result obtained from the simulation was compared with the actual operation of 30 kW gas engine driven micro CHP system. It was found that the simulation could reproduce the daily operation behavior, such as operating hours and mean load factor, closely to the actual behavior of the system and could predict the amount of electrical/thermal output and fuel consumption with the error of less than 12%.

• 설비공학논문집
• /
• 제6권3호
• /
• pp.193-205
• /
• 1994

A simulation program of the plate finned-tubes condenser widely used in the air conditioning system was developed. The program took into account the variations of the flow properties and fluid friction factor of refrigerant, and the heat transfer coefficients of refrigerant and air sides. The program was applied to a copper tube condenser which has outside diameter of 10.05mm, inside diameter of 9.35mm, length of 5.20m and three rows arraied staggered. Simulation results were such that refrigerant was super-heated state from the entrance to the 0.14m point, two-phase flow from the 0.14m point to the 4.10m point, sub-cooled state from the 4.10m point to the outlet. The degree of sub-cooled was $6.1^{\circ}C$. The variations of refrigerant quality, temperature, pressure, velocity, specific enthalpy, specific volume and air temperature, tube temperature were showed.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2005년도 동계학술발표대회 논문집
• /
• pp.211-216
• /
• 2005

The authors carried out experiment, Computer Fluid Dynamics(CFD) and energy simulation of simulator. As a results of experiment and CFD, diffuser velocity is very important design factor for occupied zone air conditioning in Under Floor Air Distribution(UFAD) system. Then, in contrast to energy consumption of the Overhead system, the UFAD system could reduce 6.4% of the total energy because of occupied tone air conditioning. It concluded that tile UFAD system is more effective in energy Performance than the Overhead system.

• 설비공학논문집
• /
• 제13권11호
• /
• pp.1079-1088
• /
• 2001

A dynamic simulation model was developed to analyse the transient characteristics of a multi-inverter heat pump. The programs included a basic air conditioning system such as a evaporator, condenser, compressor, linear electronic expansion valve (LEV) and by-pass circuit. The theoretical model was derived from mass conservation and energy conservation equations to predict the performance of the multi-inverter heat pump at various operating conditions. Calculated results were compared with the values obtained from the experiments at different operation frequencies of compressor, area of the LEV and configuration of indoor units operation. The results of the simulation model showed a good agreement with the experimental ones, so that the model could be used as an efficient tool for thermodynamic design and control factor design of air-conditioners.

• 대한설비공학회지:설비저널
• /
• 제27권6호
• /
• pp.513-522
• /
• 1998

우리나라의 여름 기후는 고온 다습한 특징을 갖고 있다. 고온 다습한 지역에서는 습도가 쾌적성을 결정하는데 중요한 요소가 되기 때문에, 습도가 높으면 온도가 그다지 높지 않더라도 쉽게 무더위를 느낀다. 이러한 계절적 특성을 없애 쾌적한 생활을 영위하기 위하여 생활의 질적 향상과 더불어 공조장치의 수요가 매년 두드러지게 증가하고 있다. 특히, 실내의 경우에는 공조장치 중 대표적인 에어컨(air conditioner)으로 냉방을 행함으로써 고온 다습한 여름철의 거주공간을 개선하고 있다. 그러나 고온 다습한 환경하에서의 과다한 에어컨 사용은 인체의 온열 환경적 측면에서 오히려 불리하다. 왜냐 하면, 에어컨에서는 여름철에 잠열(latent heat)을 고려해야 함에도 불구하고 단지 현열비(sensible heat factor)로 취출온도를 결정하고 있기 때문이다. 그 결과, 실내가 과다하게 냉각되어 재실자에게 불쾌감은 물론, 심지어 냉방병도 초래할 수가 있다.

• 설비공학논문집
• /
• 제28권1호
• /
• pp.29-34
• /
• 2016

The friction factor unit was studied to find a more economic alternative compared to the conventional 30 mmAq/m. The pipe and pump for cooling water piping used in a failing were selected, and the friction factor unit was changed to calculate the pipe diameter and the brake shaft power. Based on current electric charges, After the brake shaft power was converted into operational costs based on current electric charges, then an economic analysis was conducted considering that incorporated the initial installation costs and operational costs for the pump. We found that the friction factor unit when using 20 mmAq/m is more economical than that with 30 mmAq/m, if the piping is used for more than 4 years. The small friction factor unit is desirable when the piping is used for quite a long period of time, and the selection of a more economic friction factor unit should considering the period of usage will be important.

• 설비공학논문집
• /
• 제17권6호
• /
• pp.505-513
• /
• 2005

We measured the time-dependent concentration of VOCs emitted from Ondol floor, furniture, and the wall made of various building materials. After obtaining results from the previous measurement, we developed the estimation equations of the concentration decay, and obtained the estimated graphs for the concentration decay under different air change rates and loading factor conditions by using the estimated equations. We conducted our tests by applying our measurements to real residences for 110 days in the case of furniture and for 40 days in the case of the floor. We also conducted experiments in the cases of various wall materials for 7 days which totaled 10 times. We used the GC/FID for experiments for real residences accord-ing to the specified procedures of the NIOSH 1501, and carried out experiments for wall materials according to the specified procedures of the ASTM 5116-97. When conducting experiments for wall materials, we set the temperature and relative humidity at $23^{\circ}C$ and $50\%$, respectively. We also set the air change rate and loading factor at 0.7/h and $1.617 m^2/m^3$, respectively. Our results showed that it is possible to predict proplrly the time-dependent concentration decay of VOCs by using logarithmic functions in both cases of experiments for real residences and for wall materials. Furthermore, we found that the concentration decay rate of VOCs increased rapidly as the air exchange rate increased while the concentration decay rate decreased as the loading factor increased.

• Journal of Electrical Engineering and Technology
• /
• 제5권4호
• /
• pp.606-613
• /
• 2010

This paper proposes a novel current-based maximum power point tracking (CMPPT) method for a single-phase photovoltaic power conditioning system (PV PCS) by using a modified incremental conductance method. The CMPPT method simplifies the entire control structure of the power conditioning system and uses an inherent current source characteristic of solar cell arrays. Therefore, it exhibits robust and fast response under a rapidly changing environmental condition. Digital phase locked loop technique using an all-pass filter is also introduced to detect the phase of grid voltage, as well as the peak voltage. Controllers of dc/dc boost converter, dc-link voltage, and dc/ac inverter are designed for coordinated operation. Furthermore, a current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. A 3 kW prototype PV PCS is built, and its experimental results are given to verify the effectiveness of the proposed control schemes.

• 설비공학논문집
• /
• 제29권1호
• /
• pp.15-20
• /
• 2017

The summer climate is very hot and humid in Korea. The humidity is an important factor in determining thermal comfort. Recently, the research for dehumidification device development has been attempted to save energy that is required for the operation of the current dehumidifiers on the market. Existing dehumidification systems have disadvantages such as wasting energy to drive a compressor. Meanwhile, dehumidification systems with membranes can dehumidify humid air without increasing the dry bulb temperature so it doesn't have to consume cooling energy. In this paper, the cooling energy savings was studied when a dehumidification system was applied in a model building instead of a chiller. The sensible heat load was almost the same result, but the latent heat load was decreased by 38.9% and the total heat load was decreased by 8.5%. As a result, electric energy used to drive the compressor in a chiller was saved by applying a membrane air-conditioning system instead.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
• /
• pp.264-269
• /
• 2011

A precision of temperature control in the manufacturing process would be an important factor and become the main key to control production quality. Mostly manufacture machinery used oil as a coolant in their system so an accurate oil temperature control system become an absolute need in industrial field. This paper presents a experiment research to control the oil temperature constant at target point, in this experiment is $35^{\circ}C$ by using an inverter attached in compressor to varying the compressor speed. This control has been completed and tested through an experiment with different heat load of 4kW, 6kW, 7kW, 8kW and 10kW given under temperature constant room conditioned as $25^{\circ}C$. The results had shown the temperature deviation in the refrigerator has around $0.2^{\circ}C$ and the COP is 2.5 gained at 8kW and 10kW.