• 한국태양에너지학회 논문집
• /
• 제30권3호
• /
• pp.10-15
• /
• 2010

The aim of this study was to analysis the Heating/cooling performance of Solar Window System built in apartments. The solar window is the idea to integrate daylight as a third form of solar energy into a PV/Solar Collector system and allows more control due to the possibility to close the reflectors. However, there can be a conflict between the desire for on one hand daylight and view and on the other hand optimal energy conversion for the PV/Solar Collector system. The process of this study is as follows: 1) The Solar Window system is designed through the investigation of previous paper and work. 2)The simulation program(ESP-r, Therm5.0, Window6.0) was used in energy performance analysis. The reference model of simulation was made up to analysis energy performance on Solar Window system. 3)Selected reference model(Floors:15, Area of Unit:$148.5m^2$) for heating/cooling energy analysis, Energy performance simulation with various variants, such as U-value of Solar Window system according to its position and angle. Consequently, When Solar Window system is equipped with balcony window of Apartment, Annual heating and cooling energy of reference model was cut down about 5%~11%.

• 한국태양에너지학회 논문집
• /
• 제28권4호
• /
• pp.43-49
• /
• 2008

The purpose of this study is to present the simulation results and an overview of the performance assessment of a solar heating & cooling system by means of the $200m^2$ evacuated tube solar collector. The simulation was carried out using the thermal simulation code TRNSYS with new model of a single-effect LiBr/$H_{2}O$ absorption chiller developed by this study. The calculation was performed for yearly long-term thermal performance and for two design factors: the solar hot water storage tank and the cold water storage tank. As a result, it was anticipated that the yearly mean system efficiency is 46.7% and the solar fraction for the heating, cooling and hot water supply are about 84.4 %, 41.7% and 72.4%, respectively.

• Nuclear Engineering and Technology
• /
• 제52권2호
• /
• pp.271-278
• /
• 2020

The investigation into a full-scale 27 m high, by 6 m wide, thermosyphon loop. The simulation model is based on a one-dimensional axially-symmetrical control volume approach, where the loop is divided into a series of discreet control volumes. The three conservation equations, namely, mass, momentum and energy, were applied to these control volumes and solved with an explicit numerical method. The flow is assumed to be quasi-static, implying that the mass-flow rate changes over time. However, at any instant in time the mass-flow rate is constant around the loop. The boussinesq approximation was invoked, and a reasonable correlation between the experimental and theoretical results was obtained. Experimental results are presented and the flow regimes of the working fluid inside the loop identified. The results indicate that a series of such thermosyphon loops can be used as a cavity cooling system and that the one-dimensional theoretical model can predict the internal temperature and mass-flow rate of the thermosyphon loop.

• 한국자동차공학회논문집
• /
• 제11권4호
• /
• pp.58-67
• /
• 2003

An automotive engine cooling system is closely related with overall engine performances, such as reduction of fuel consumption, decrease of air pollution, and increase of engine life. Because of complex reaction between each component, the direct experiment, using a vehicle, takes high cost, long time, and slow response to the system change. Therefore, a computer simulation would provide the designer with an inexpensive and effective tool for design, development, and optimization of the engine cooling system over a wide range of operating conditions. In this work, it has been predicted the thermal performance of the engine cooling system in cases of stationary mode, constant speed mode, and city-drive mode by mathematical modelling of each component and numerical analysis. The components are engine, radiator, heater, thermostat, water pump, and cooling fans. Since the engine model is the most important, that is divided into eight sub-sections. The volume mean temperature of eight sub-sections are simultaneously calculated at a time. For detail calculation, the radiator and heater are also divided into many sub-sections like control volumes in finite difference method. Each sub-section is assumed to consist of three parts, coolant, tube with fin, and air. Hence it has been developed the simulation program that can be used in case of design and system configuration changes. The overall performance results obtained by the program were desirable and the time-traced tendencies of the results agreed fairly well with those of actual situations.

• 설비공학논문집
• /
• 제28권8호
• /
• pp.316-324
• /
• 2016

This study investigated a compact regenerative evaporative cooler (REC). To achieve practical applications of an REC, it is very important to consider the compactness as well as the cooling performance. Therefore, a prototype of the REC was designed and fabricated to improve the compactness by reducing the length through the insertion of fins in both the dry and wet channels. The REC prototype was tested in terms of performance evaluation under various operating conditions. An analytical model was also developed to analyze the effects of the axial conduction through the solid body of the REC, the wetness of the surface in the wet channel, and the thermal capacity of the evaporation water flow. The model was validated by comparing the results of a simulation with experimental data. The numerical simulation was based on the model to analyze the performance of the REC and to suggest methods to improve the cooling performance of the REC. Finally, the performance of the present REC was compared to that obtained in previous experimental studies. The results showed that the REC prototype in the present study is the most compact and achieves the highest cooling performance.

• Architectural research
• /
• 제14권1호
• /
• pp.11-18
• /
• 2012

College of Architecture, Georgia Institute of Technology, Atlanta, GA, US Abstract The intermittent heating and cooling energy need calculation of the ISO 13790 monthly method was examined. The current ISO 13790 method applies a reduction factor to the continuous heating and cooling need calculation result to derive the intermittent heating and cooling for each month. This paper proposes a method for the intermittent energy need calculation based on the internal mean temperature calculation. The internal temperature calculation procedure was introduced considering the heat-balance taking into account of heat gain, heat loss, and thermal inertia for reduced heating and cooling period. Then, the calculated internal mean temperature was used for the intermittent heating and cooling energy need calculation. The calculation results from the proposed method were compared to the current ISO 13790 method and validated with a dynamic simulation using EnergyPlus. The study indicates that the intermittent heating and cooling energy need calculation method using the proposed model improves transparency of the current ISO 13790 method and draws more rational outcomes in the monthly heating and cooling energy need calculation.

• Journal of Power Electronics
• /
• 제16권4호
• /
• pp.1598-1611
• /
• 2016

In some special occasions with strict size requirements, such as mine hoists, improving the design accuracy of the forced-air cooling systems of NPC three-level inverters is a key technology for improving the power density and decreasing the volume. First, a fast power-loss calculation method was brought. Its calculation principle introduced in detail, and the computation formulas were deduced. Secondly, the average and dynamic power losses of a 1MW mine hoist acting as the research target were analyzed, and a forced-air cooling system model based on a series of theoretical analyses was designed with the average power loss as a heat source. The simulation analyses proves the accuracy and effectiveness of this cooling system during the unit lifting period. Finally, according to an analysis of the periodic working condition, the maximum power-loss range of a NPC three-level inverter under multi cycle operation was obtained and its dynamic power loss was taken into the optimized cooling system model as a heat source to solve the power device damage caused by instantaneous heat accumulation. The effectiveness and feasibility of the optimization design based on the dynamic power loss calculation of the maximum power-loss range was proved by simulation and experimental results.

• 설비공학논문집
• /
• 제15권6호
• /
• pp.543-550
• /
• 2003

In order to saving the energy for HVAC system of buildings, utilization of wind-induced cross ventilation is thought to be promising. However, utilization of natural ventilation alone is not sufficient for maintaining the human thermal-comfort such as in hot and humid regions. A hybrid air conditioning system with a controlled natural ventilation system, or combination of natural ventilation with mechanical air conditioning is thought to overcome the deficiency of wind-driven cross ventilation and to have significant effects on energy reduction. This paper describes a concept of hybrid system and propose a new type of hybrid system using radiational cooling with wind-induced cross ventilation. Moreover, a radiational cooling system is compared with an all-air cooling system. The characteristics of the indoor environment will be examined through CFD (Computational Fluid Dynamics) simulation, which is coupled with a radiation heat transfer simulation and with HVAC control in which the PMV value for the human model in the center of the room is controlled to attain the target value.

• 한국수소및신에너지학회논문집
• /
• 제18권3호
• /
• pp.292-300
• /
• 2007

A dynamic system model of a proton exchange membrane fuel cell(PEMFC) has been developed. The PEMFC of this study has large active area with water cooling in order to simulate the performance of the commercially viable PEMFC system for the transportation. A PEMFC stack model is a transient thermal model which is respond to the dynamic change of the coolant temperature and the flow rate. The dynamic cooling system model has been developed to determine the coolant flow rate and the coolant temperature. Prior to the system level study, thermal management criteria have been set up and brought to the control command of the cooling system. Since the system model is designed to evaluate the effect of thermal management on the system performance, it is attempted to determine the proper control algorithm of the cooling system so that the PEMFC system is working on the thermal management criteria. As a result of simulation, feedback controlled cooling system consumes less power and produce more power comparing with that of conventionally controlled cooling system.

• 한국태양에너지학회 논문집
• /
• 제28권5호
• /
• pp.28-35
• /
• 2008

The aim of this study was to analysis the Heating/cooling performance of movable insulation system built in apartments. The process of this study is as follows: 1) Test-cells of movable insulation are designed through the investigation of previous paper and work. The type of the movable insulation used in test-cell is low emissivity(5%) insulation, measured for heating season and the thermal effects are analyzed. 2) The simulation program(Design Builder) was used in energy performance analysis. the reference model of simulation was made up to analysis energy performance on movable insulation system. 3) Selected reference model(Floors:15, Area of Unit:115.5$m^2$) for heating/cooling energy analysis, Energy performance simulation with various variants, such as slate angle of movable insulation(5$^{\circ}$, 30$^{\circ}$, 50$^{\circ}$) and position of movable insulation. Consequently, When movable insulation system is equipped with balcony window of Apartment, Annual heating energy of reference model was cut down at the average of 5.4kWh/$m^2$ or 4.6% of heating/cooling energy.