Earticle

The purpose of this study is to develop a computerized shading simulation program considering solar radiation and to verify its numerical and graphical effectiveness in fenestration system design. Even though the thermal effect of the transmitted solar radiation through fenestration is understood as one of critical factors in building design, it is hardly considered in early design stage because of difficulty in its concept and calculation process. To be widely used by architectural designers in their architectural projects, the program should provide user-friendly graphical interface which can clearly represent the thermal effect of their design as well as proper guideline that can provide accurate simulation results without big burden of user input. The Shaded Fenestration Design(SFD) program has been developed as an energy-effective shading device and window system design program considering effects of shaded solar radiation. For the validation of the program, a physical test box was specially designed and tested to show the accuracy of the program. The comparative tests with widely used computer simulation program(DOE-2) showed that the SFD program with the HDKR model provided more reliable results than DOE-2 program.

Recently, developing and applying of the double skin, which can utilize the natural energy with more aggressive characteristic, is now in study. The studies of the double skin are been constantly in progress in advanced countries as well as in domestic. And the double skin has lately been put to practical use. This study has selected the building with the box-typed double skin system and performed the thermal performance prediction of double skin system using TRNSYS. The U-value of the double skin system has been calculated. And this one has compared the measured U-value with the simulated U-value of double skin system. The results of comparison between experiment and the simulation were similar. So a prediction method on thermal performance of the box-typed double skin using TRNSYS simulation has secured a feasibility.

Optical phased arrays (OPAs) enable solid-state beam steering for light detection and ranging (LiDAR) applications; however, they are limited by inefficiency in the nonlinear optical performance and slow thermal phase modulation. In this study, we present a novel graphene-integrated silicon nitride (SiN) waveguide designed for solid-state LiDAR, which helps in simultaneously enhancing the nonlinear optical performance and thermal phase modulation efficiency within a single device to improve the OPA functionality. By leveraging the high third-order nonlinear susceptibility and superior thermal conductivity of graphene, the waveguide enhances the Kerr nonlinearity and accelerates the phase modulation for precise OPA-based beam steering. These properties are optimized by integrating graphene with SiN waveguides, and simulations are conducted using Lumerical finite-difference time-domain and HEAT Solver tools to validate the design. The simulations demonstrate an improvement of 8.2% in the Kerr nonlinearity and third-harmonic generation at 516.6 nm, along with a faster thermal response and reduced power consumption when compared with titanium nitride (TiN) heaters. This complementary metal-oxide-semiconductor-compatible, scalable platform overcomes the limitations of the conventional silicon-based OPAs and contributes to the development of high-resolution, low-power LiDAR systems. This study paves the way for compact, energy-efficient, and high-performance solid-state LiDAR solutions, with potential applications in telecommunications, sensing, and other photonic systems that require precise OPA-based beam steering and enhanced nonlinear functionalities.

UTC(Unglazed Transpired Collector) system has recently emerged as a new solar air heating technology. It is relatively inexpensive because it has not a glazed material. And it demonstrates efficient particularly for the applications in which larger wall area facilities with a high outdoor air requirement. Mathematical algorithm for UTC thermal modeling has been understood for further improvement of the system. EES and TRNSYS model of actual solar wall panel could be developed for computer simulations under other conditions. Computer models could be validated with the measured data from fixed outdoor test cell in KIER(Korea Institute of Energy Research). Major design parameters could be identified such as panel configuration and absorptivity and emissivity values for UTC design.

Thermal performance of test cell of model hot water Ondol house was simulated by equivalence heat resistence and heat capacity method. In this method wall was replaced by two equivalence and one heat capacity. This method enables to simulate the variation of temperature of each element of model house. The effect of pipe diameter, pitch of pipe and with or without consideration of inter-radiation between wall surfaces on the energy consumption rate were investgated. Results show that radiations between the ground surface of room and wall surfaces contribute to the heating of room air by reducing the convection heat loss through the wall surfaces.

Solar air heaters (SAHs) are simple in design and widely used for solar energy collection devices, and a packed bed is one of typical solar energy storage systems of thermal energy captured by SAHs. This paper presents mathematical modeling and simulation on the thermal performance of various packed bed energy storage systems. A MATLAB program is used to estimate the thermal efficiency of packed bed SAH. Among the various packed bed energy storage systems considered, the wire mesh screen packed bed SAH shows the best thermal efficiency over the entire range of design conditions. The maximum of thermal efficiency of packed bed SAH with wire mesh screen matrices has been found to be 0.794 for Re=2000 - 20000 and ${\Delta}T/I=0.002-0.02$.

A new method is presented for developing a simulation program which can analyze the heat transfer characteristics of fin-tube heat exchanger. This method is able to describe several types of refrigerant circuit arrangement. The delivery path of air and refrigerant properties is simplified by transforming three-dimensional array into one-dimensional array. By comparing simulated results with experiment results, the deviation was 8.2%. Several fin-tube heat exchangers of different design factors and operating conditions were simulated using this program. It was shown that this program could be used for designing practical fin-tube heat exchangers.

This study aims to evaluate thermal performance of large-scaled curtain wall specimen using Korean Standard test methods and computer heat transfer analysis based on ISO 15099, ISO 10211, ISO 10077-2. The reference model of specimen is aluminum stick curtain wall system consisting of low-e double glazing with warm edge spacer and argon gas. The thermal transmittance and temperature difference ratio (TDR) were chosen as thermal performance factors. The results were as follows. First, the results of thermal transmittance for large-scaled specimen through test method and computer simulation showed 1.919 W/㎡·K and 1.843 W/㎡·K respectively. The error rate between test and simulation indicated 3.96%. Secondly, the results of the highest temperature difference ratio between test and computer simulation showed 0.32 and 0.29 respectively at both the edge of glazing. The TDR at center and edge of glazing were not up to the region 1 of design criteria for prevention of condensation in apartment housing.

Boiler design should be desinged to maximize thermal efficiency of the system under imposed load requirement and a boiler should be validated for transient operation. If a proper prediction is possible on the transient behavior and transient characteristics of a boiler, one may asses the performance of boiler component, control logics and operation procedures. In this work, dynamic modeling method of boiler is presented and dynamic simulation of load runback scenario was carried out on suprecritical oil-firing boiler.