• Smart Structures and Systems
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• v.29 no.5
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• pp.677-691
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• 2022

Water cycle algorithm (WCA) has been a very effective optimization technique for complex engineering problems. This study employs the WCA for simultaneous prediction of heating load (L_H) and cooling load (L_C) in residential buildings. This algorithm is responsible for optimally tuning a neural network (NN). Utilizing 614 records, the behavior of the L_H and L_C is explored and the captured knowledge is then used to predict for 154 unanalyzed building conditions. Since the WCA is a population-based algorithm, different numbers of the searching agents were tested to find the most optimum configuration. It was observed that the best solution is discovered by 500 agents. A comparison with five newly-developed benchmark optimizers, namely equilibrium optimizer (EO), multi-tracker optimization algorithm (MTOA), slime mould algorithm (SMA), multi-verse optimizer (MVO), and electromagnetic field optimization (EFO) revealed that the WCANN predicts the desired parameters with considerably larger accuracy. Obtained root mean square errors (1.4866, 2.1296, 2.8279, 2.5727, 2.5337, and 2.3029 for the L_H and 2.1767, 2.6459, 3.1821, 2.9732, 2.9616, and 2.6890 for the L_C) indicated that the most reliable prediction was presented by the proposed model. The EFONN, however, provided a more time-effective solution. Lastly, an explicit predictive formula was elicited from the WCANN.

• Solar Energy
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• v.18 no.3
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• pp.107-112
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• 1998

Basic design of a solar driven absorption cooling machine(SDACM) with a cooling capacity of 5 USRT was carried out. The SDACM is a single effect cycle driven by low temperature hot water from solar collectors. The SDACM design data were calculated by the steady state simulation program which was developed in this study The variation of COP and cooling capacity of the SDACM were investigated at different off-design conditions. Both the cooling capacity and the system COP were improved with decreasing cooling water temperature. If hot water temperature was increased, the cooling capacity was improved but the system COP was found to be decreased. The decrease of the system COP were basically caused by increased thermal loads in the system components.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.581-585
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• 2010

This study introduced a Bayesian based frequency analysis in which the statistical trend seasonal analysis for hydrologic extreme series is incorporated. The proposed model employed Gumbel and GEV extreme distribution to characterize extreme events and a fully coupled bayesian frequency model was finally utilized to estimate design rainfalls in Seoul. Posterior distributions of the model parameters in both trend and seasonal analysis were updated through Markov Chain Monte Carlo Simulation mainly utilizing Gibbs sampler. This study proposed a way to make use of nonstationary frequency model for dynamic risk analysis, and showed an increase of hydrologic risk with time varying probability density functions. In addition, full annual cycle of the design rainfall through seasonal model could be applied to annual control such as dam operation, flood control, irrigation water management, and so on. The proposed study showed advantage in assessing statistical significance of parameters associated with trend analysis through statistical inference utilizing derived posterior distributions.

• Current Research on Agriculture and Life Sciences
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• v.30 no.2
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• pp.97-104
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• 2012

Over the last century, drainage systems have become an integral component of agriculture. Climate observations and experiments using General circulation models suggest an intensification of the hydrologic cycle due to climate change. This study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage in Daegu, Republic of Korea. Historical and Long Ashton Research Station weather generator perturbed future climate data from 15 general circulation models for a field in Daegu were ran into a water management simulation model, DRAINMOD. The trends and variability in rainfall and Soil Excess Water ($SEW_{30}$) were assessed from 1960 to 2100. Rainfall amount and intensity were predicted to increase in the future. The predicted annual subsurface drainage flow varied from -35 to 40 % of the baseline value while the $SEW_{30}$ varied from -50 to 100%. The expected increases in subsurface drainage outflow require that more attention be given to soil and water conservation practices.

• Journal of Korea Water Resources Association
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• v.38 no.8 s.157
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• pp.645-653
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• 2005

Water cycle analysis in the Cheonggyecheon watershed(river length: 13.75 km, area: $50.96\;km^2$) was performed using WEP model, a physically based distributed rainfall-runoff model. As the application results of the model, the hydrological characteristics of the Cheonggyecheon watershed are significantly consistent with those of a typical urbanized watershed. The direct runoff from the watershed was larger and the evapotranspiration. was lower, and the response of runoff to rainfall was occurred very fast, as compared to forest watersheds. The river channel routing simulation results are similar to the change pattern and scale of the field data. The possible supply period of instream flow from Cheonggyecheoon watershed itself was estimated using WEP. According to the WEP simulation results for the annual water balance of the Cheonggyecheon watershed in 2002, the amount of direct runoff, infiltration and evapotranspiration were 830 mm, 388 mm and 397 mm respectively for an annual precipitation of 1,388 mm. The runoff to rivers was 1,288 mm. And the proportion of direct runoff, intermediate runoff and groundwater runoff were $67.6\%,\;12.7\%$ and $19.7\%$ respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.4
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• pp.173-179
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• 2013

Middle-sized $CO_2$ water heater having compressor power of 7.45 kW was designed, and its performances were experimentally tested. Besides, optimum design of the $CO_2$ water heater was conducted by cycle simulation. When ambient temperature of $7^{\circ}C$ and hot water outlet temperature of $80^{\circ}C$ the $CO_2$ water heater showed the COP of 3.2. As hot water temperature increased the COP is getting decreased due to significant increase of compressor power consumption compared to increasing rate of heating capacity. When ambient temperature increased from $-3^{\circ}C$ to $12^{\circ}C$ the COP increased by 30%. The optimum components design of a gas cooler, an internal heat exchanger, and an evaporator were conducted, and the experimental correlation between amount of EEV opening and ambient temperature, and hot water temperature was suggested.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.792-799
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• 1998

Further improvement of existing $H_{2}O/LiBr$ absorption refrigeration machine is absolutely neces-sary to promote the utilization of gas-cooling system Among various methods to improve the per-formance of the absorption refrigeration machine this research has focused on the use of a new working fluid that has better properties than the existing $H_{2}O/LiBr$ working fluid. In the series of the research, $H_{2}O/LiBr+HO{(CH_{2})}_{3}OH$ system was selected as the most promisable candidate. The absorption refrigeration machine is water-cooled double-effect, $H_{2}O/LiBr+HO{(CH_{2})}_{3}OH$ sys-tem with series flow type. In this study we found out the characteristic of new working solution through the cycle simulation and compared the result with that of LiBr solution to evaluate. Theoptimum designs and operating conditions were determined based on the operating constraints and the coefficient of performance. Results demonstrate that new working fluid subsrantially increases COP by as much as 10% and has a wider working range with 8% higher crystallization limits compared to the conventional $H_{2}O/LiBr$.

• Water for future
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• v.24 no.4
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• pp.41-48
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• 1991

This paper describes the characteristics of tidal currents in the Gamag Bay by using the two-dimensional nonlinear hydrodynamic euation. The basic equations are derived by Navier-Stokes momentum equation and continuity equation and its characteristics critically are reviewed, and they are analysed by the implicit finite difference method. The numerical model is constructed two-dimensional(depth-averaged) simple layer model. This paper investigates the stability of solution and convergence of solution in application of the method to Gamag Bay, and the reproducibility of the simulation is also discussed in comparison with the results of field survey. The following items are clarifide through the numerical investigation; i)the reproduc-ibility of tidal range and currents are quite acceptable, comparing with the results of model tests and field data, and ii) tidal cycle for convergent solution is four tidal cycle, also, iii) bottom friction is successfully represented as c=(1/n))$h^{1/6}$.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.44-60
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• 2021

In this paper, we validate the decay heat calculation capability via a two-step method to analyze spent nuclear fuel (SNF) discharged from pressurized water reactors (PWRs). The calculation method is implemented with a lattice code STREAM and a nodal diffusion code RAST-K. One of the features of this method is the direct consideration of three-dimensional (3D) core simulation conditions with the advantage of a short simulation time. Other features include the prediction of the isotope inventory by Lagrange non-linear interpolation and the use of power history correction factors. The validation is performed with 58 decay heat measurements of 48 fuel assemblies (FAs) discharged from five PWRs operated in Sweden and the United States. These realistic benchmarks cover the discharge burnup range up to 51 GWd/MTU, 23.2 years of cooling time, and spanning an initial uranium enrichment range of 2.100-4.005 wt percent. The SNF analysis capability of STREAM is also employed in the code-to-code comparison. Compared to the measurements, the validation results of the FA calculation with RAST-K are within ±4%, and the pin-wise results are within ±4.3%. This paper successfully demonstrates that the developed decay heat calculation method can perform SNF back-end cycle analyses.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.268-278
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• 2010

This study derived the effectiveness analysis results of construction of wastewater treatment plant under climate change scenarios. Canadian Global Coupled Model (CGCM3) was used and A1B and A2 of Special Report on Emission Scenario (SRES) were selected. Regional climate change data for this application were downscaled by using Statistical Downscaling Model (SDSM) and the flow and BOD concentration durations were obtained by using Hydrological Simulation Program - Fortran (HSPF). The criteria for low flow and water quality were chosen as $Q_{99}$, $Q_{95}$, $Q_{90}$ and $C_{30}$, $C_{10}$, $C_1$. The numbers of days to satisfy the instreamflow requirements and target BOD concentration were also added to the criteria for comparison. As a results, small wastewater treatment plant improved the water cycle due to the increase of low flow and the decrease of BOD concentration. But climate change affected the reduction of effectiveness significantly. Especially in case of construction of small waste water treatment plant in the upstream region, it is necessary to take climate change impact into consideration since it is usually related to the low flow and the water quality of the stream.