• Title/Summary/Keyword: Parametric error

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Energy Regression Analysis for Economic Evaluation of Cooling Plants (냉방열원의 경제성 평가를 위한 건물에너지 회귀식 산출)

  • 김영섭;김강수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.5
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    • pp.377-384
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    • 2002
  • For economic evaluation of cooling plant equipments, it is necessary to simplify energy Prediction method, which should includes efficiency corrected by part-load ratio. This study proposed simplified method with regression equations of time-average partial loads and refrigerator capacity. DOE-2 Program was used to carry out a parametric study of twelve design variables. Five input variables were considered to be significant and were used in the regression equations. To test accuracy of simplified method, calculated results were compared with DOE-2 simulated results. Test result showes a good agreement with the simulation result with an error of 5.9∼7.6%. It is expected that this method can be used as an easy prediction tool for comparing energy use of different cooling plants during the early design stage.

Development of Critical Heat Flux Correction Factor for Water under Flow Oscillation Conditions

  • Kim, Yun-Il;Baek, Won-Pil;Chang, Soon-Heung
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.11a
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    • pp.242-247
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    • 1996
  • Flow oscillations in boiling channels induces a drastic reduction of the (critical heat flux) CHF or premature burnout. However, most of CHF works and correlations have been focused on stable flow conditions without considering flow oscillation. Therefore to improve the understanding on flow oscillation CHF, in this paper a new CHF correction factor to predict the CHF values under flow oscillation conditions has been developed from 126 experimental data. Also to investigate the dominant factor on flow oscillation CHF parametric trends are analyzed by using the developed correction factor. The overall mean accuracy ratio of the developed correction factor is 1.033 with a standard deviation of 0.195. The RMS errors 0.198. Its assessment shows that the predictions agree well with the experimental data within 25% error bounds.

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Simplified Design and Optimization of Slotless Brushless DC Machine for Micro-Satellites Electro-Mechanical Batteries

  • Abdi, Babak;Bahrami, Hamid;Mirtalaei, S.M.M.
    • Journal of Electrical Engineering and Technology
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    • v.8 no.1
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    • pp.124-129
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    • 2013
  • Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slotless, external rotor, brushless DC machines are proposed and used in these systems as Motor/Generator. A simplified analytic design method is given for this type of machines and, the optimization of machine in order to have maximum efficiency and minimum volume and weight are given in this paper. Particle swarm optimization (PSO) is used as the optimization algorithm and the finite element-based simulations are used to confirm the design and optimization process and show less than 6% error in parametric design.

VALIDATION OF GRID AND BOUNDARY CONDITIONS FOR OPTIMAL DESIGN OF HEAT RECOVERY SYSTEM (열 회수 시스템의 최적 설계를 위한 격자 및 경계 조건 검증에 관한 연구)

  • Lee, D.G.;Shin, S.W.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.608-609
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    • 2011
  • In this study, we tried to validate FLUENT solver model and domain setting for the problem of convective heat transfer in multiple tube bank under transitional zone. We have paid special attention to verify proper boundary conditions and the grid convergence. Through validation work, it is found that unsteady solution method with two-dimensional simulation domain can produce reasonable accurate results compared with existing experimental data. Simulation results with steady solution generates relatively large error. We found that both steady and unsteady method for three-dimensional domain shows acceptable accuracy. Further parametric study for deriving correlation from transverse and longitudinal pitch is currently underway.

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Quasi-linearization of non-linear systems under random vibration by probablistic method (확률론 방법에 의한 불규칙 진동 비선형 계의 준선형화)

  • Lee, Sin-Young;Cai, G.Q.
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.785-790
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    • 2008
  • Vibration of a non-linear system under random parametric excitations was evaluated by probablistic methods. The non-linear characteristic terms of a system were quasi-linearized and excitation terms were remained as they were given. An analytical method where the square mean of error was minimized was ysed. An alternative method was an energy method where the damping energy and rstoring energy of the linearized system were equalized to those of the original non-linear system. The numerical results were compared with those obtained by Monte Carlo simulation. The comparison showed the results obtained by Monte Carlo simulation located between those by the analytical method and those by the energy method.

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A Study of Rewetting Temperature in Cooling of Hot Surfaces (高溫表面의 冷却時 再水着 溫度 에 관한 硏究)

  • 정문기;이영환;박종석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.4
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    • pp.463-470
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    • 1985
  • In this study a parametric analysis for the rewetting temperature was made with 572 data obtained from the single tube experiment. The rewetting temperature was also evaluated by measuring the vaporization time of a liquid drop on a hot surface at the elevated pressures. The results showed that the rewetting temperature increased with flooding rate, inlet subcooling pressure and initial wall temperature, and decreased with increasing axial elevation. Based on the results obtained, the rewetting temperature correlation was suggested. From the comparison of correlated rewetting temperatures with measured values, it showed that the correlated values fell within .+-.5% error from the measured values.

A Study on the Reproduction of Acoustic Characteristics of a Car's Exhaust Noise Using Digital Filtering Technique (디지탈 필터링 기법(技法)을 이용(利用)한 자동차(自動車) 배기소음(排氣騷音)의 음향특성(音響特性) 재현(再現)에 관(關)한 연구(硏究))

  • Cho, J.H.;Lee, J.M.;Hwang, Y.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.1 no.3
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    • pp.55-62
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    • 1993
  • Autoregressive moving average(ARMA) model which is a time domain parametric modeling method is implemented for modeling and reproducing characteristics of exhaust noise of an automobile in various RPM range. Experiments have been carried out using 9 set of exhaust noise signals measured at 1,000-3,000 RPM range. Characteristics of sampled signals were estimated using ARMA modeling and Akaike's FPE(final prediction error) criterion to define exact model structure and for model validation. The digital filter consisted of the esitmated ARMA(70,1) model parameters was programed to reproduce exhaust noise. The spectral analysis of reproduced noise is very close to original. The results show that our approaching technique for reproducing acoustic characteristics is valid and feasible to apply in the field of noise quality control.

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Analyzing Clustered and Interval-Censored Data based on the Semiparametric Frailty Model

  • Kim, Jin-Heum;Kim, Youn-Nam
    • The Korean Journal of Applied Statistics
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    • v.25 no.5
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    • pp.707-718
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    • 2012
  • We propose a semi-parametric model to analyze clustered and interval-censored data; in addition, we plugged-in a gamma frailty to the model to measure the association of members within the same cluster. We propose an estimation procedure based on EM algorithm. Simulation results showed that our estimation procedure may result in unbiased estimates. The standard error is smaller than expected and provides conservative results to estimate the coverage rate; however, this trend gradually disappeared as the number of members in the same cluster increased. In addition, our proposed method was illustrated with data taken from diabetic retinopathy studies to evaluate the effectiveness of laser photocoagulation in delaying or preventing the onset of blindness in individuals with diabetic retinopathy.

FREQUENCY HISTOGRAM MODEL FOR LINE TRANSECT DATA WITH AND WITHOUT THE SHOULDER CONDITION

  • EIDOUS OMAR
    • Journal of the Korean Statistical Society
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    • v.34 no.1
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    • pp.49-60
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    • 2005
  • In this paper we introduce a nonparametric method for estimating the probability density function of detection distances in line transect sampling. The estimator is obtained using a frequency histogram density estimation method. The asymptotic properties of the proposed estimator are derived and compared with those of the kernel estimator under the assumption that the data collected satisfy the shoulder condition. We found that the asymptotic mean square error (AMSE) of the two estimators have about the same convergence rate. The formula for the optimal histogram bin width is derived which minimizes AMSE. Moreover, the performances of the corresponding k-nearest-neighbor estimators are studied through simulation techniques. In the absence of our knowledge whether the shoulder condition is valid or not a new semi-parametric model is suggested to fit the line transect data. The performances of the proposed two estimators are studied and compared with some existing nonparametric and semiparametric estimators using simulation techniques. The results demonstrate the superiority of the new estimators in most cases considered.

A New Approach to Servo System Design in Hard Disk Drive Systems

  • Kim, Nam-Guk;Choi, Soo-Young;Chu, Sang-Hoon;Lee, Kang-Seok;Lee, Ho-Seong
    • Transactions of the Society of Information Storage Systems
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    • v.1 no.2
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    • pp.137-142
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    • 2005
  • In this paper, we propose a new servo system design strategy to reduce the position error signal(PES) and track mis-registration(TMR) in magnetic disk drive systems. The proposed method provides a systematic design procedure based on the plant model and an optimal solution via an optimization with a 'Robust Random Neighborhood Search(RRNS)' algorithm. In addition, it guarantees the minimum PES level as well as stability to parametric uncertainties. Furthermore, the proposed method can be used to estimate the performance at the design stage and thus can reduce the cost and time for the design of the next generation product. The reduction of PES as well as robust stability is demonstrated by simulation and experiments.

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