• Title, Summary, Keyword: Set temperatures

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Optimal Control for Central Cooling Systems (중앙냉방시스템의 최적제어에 관한 연구)

  • 안병천
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.4
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    • pp.354-362
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    • 2000
  • Optimal supervisory control strategy for the set points of controlled variables in the central cooling system has been studied by computer simulation. A quadratic linear regression equation for predicting the total cooling system power in terms of the controlled and uncontrolled variables was developed using simulated data collected under different values of controlled and uncontrolled variables. The optimal set temperatures such as supply air temperature, chilled water temperature, and condenser water temperature, are determined such that energy consumption is minimized as uncontrolled variables, load, ambient wet bulb temperature, and sensible heat ratio, are changed. The chilled water loop pump and cooling tower fan speeds are controlled by the PID controller such that the supply air and condenser water set temperatures reach the set points designated by the optimal supervisory controller. The influences of the controlled variables on the total system and component power consumption was determined. It is possible to minimize total energy consumption by selecting the optimal set temperatures through the trade-off among the component powers. The total system power is minimized at lower supply, higher chilled water, and lower condenser water set temperature conditions.

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An Experimental Study on the Cooling Operation Characteristics for Different Entering Water Temperatures In Geothermal Heat Pump System (지열히트펌프 시스템의 EWT의 변화에 따른 냉방운전 특성에 관한 실험적 연구)

  • Ahn, Byung-Chun;Kim, Jae-Wan
    • Transactions of the Korea Society of Geothermal Energy Engineers
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    • v.6 no.1
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    • pp.1-7
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    • 2010
  • In this paper, an experimental study on the cooling operation characteristics for different entering water temperatures in geothermal heat pump system are carried out by using Lab VIEW system program Set-point temperature controls for cooling water and supply air temperatures is applied to analyze the energy consumption and control performances. As a result, the system responses show that different entering water temperatures(EWT) effect greatly on the energy consumption and system COP.

Accelerated Life Prediction of CPB(cold-pad-batch) Padder Roll Rubber to Chemical Degradation (CPB(Cold-Pad-Batch) 염색 패더롤 고무에서 화학적 노화로 인한 가속 수명예측)

  • Lim, Jee Young;Nam, Chang Woo;Lee, Woosung
    • Textile Coloration and Finishing
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    • v.29 no.3
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    • pp.155-161
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    • 2017
  • In CPB(Cold-Pad-Batch) dyeing, the rubber of the padder roll is influenced by the heat, chemical and mechanical influences and thus aging of the padder roll rubber occurs. This study presents an accelerated thermal aging test of the CPB padder roll rubber with strong alkali conditions. Using Arrhenius formula of the various property values for the various aging temperatures($80^{\circ}C$, $90^{\circ}C$, $100^{\circ}C$) of the padder roll, the accelerated life predictions could be calculated. The threshold value of the property was set at different values. The hardness was set at the point where 5% degradation occurs based on the actual use conditions, and the tensile strength was set at the point where 50% degradation occurs based on the general life prediction standards. From the results of the different physical properties at differing temperatures, the Arrhenius plot could be obtained. Through the usage of the Arrhenius Equation, significant duration expectation could be predicted, and the chemical aging behavior of the CPB padder roll could be found at the arbitrary and actual temperatures.

Thermal and light impacts on the early growth stages of the kelp Saccharina angustissima (Laminariales, Phaeophyceae)

  • Augyte, Simona;Yarish, Charles;Neefus, Christopher D.
    • ALGAE
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    • v.34 no.2
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    • pp.153-162
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    • 2019
  • Anthropogenic disturbances, including coastal habitat modification and climate change are threatening the stability of kelp beds, one of the most diverse and productive marine ecosystems. To test the effect of temperature and irradiance on the microscopic gametophyte and juvenile sporophyte stages of the rare kelp, Saccharina angustissima, from Casco Bay, Maine, USA, we carried out two sets of experiments using a temperature gradient table. The first set of experiments combined temperatures between $7-18^{\circ}C$ with irradiance at 20, 40, and $80{\mu}mol\;photons\;m^{-2}\;s^{-1}$. The second set combined temperatures of $3-13^{\circ}C$ with irradiance of 10, 100, and $200{\mu}mol\;photons\;m^{-2}\;s^{-1}$. Over two separate 4-week trials, in 2014 and again in 2015, we monitored gametogenesis, the early growth stages of the gametophytes, and early sporophyte development of this kelp. Gametophytes grew best at temperatures of $8-13^{\circ}C$ at the lowest irradiance of $10-{\mu}mol\;photons\;m^{-2}\;s^{-1}$. Light had a significant effect on both male and female gametophyte growth only at the higher temperatures. Temperatures of $8-15^{\circ}C$ and irradiance levels of $10-100{\mu}mol\;photons\;m^{-2}\;s^{-1}$ were conditions for the highest sporophyte growth. Sporophyte and male gametophyte growth was reduced at both temperature extremes-the hottest and coldest temperatures tested. S. angustissima is a unique kelp species known only from a very narrow geographic region along the coast of Maine, USA. The coupling of global warming with high light intensity effects might pose stress on the early life-history stages of this kelp, although, as an intertidal species, it could also be better adapted to temperature and light extremes than its subtidal counterpart, Saccharina latissima.

Preparation of $TiO_2$ Pure Nanoparticles by Vapor-Phase Hydrolysis (기상 가수분해에 의한 순수 $TiO_2$ 초미립자의 제조)

  • Lee, Soo-Keun
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.9 no.1
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    • pp.11-18
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    • 2003
  • The pure $TiO_2$ particles have been prepared in vapor-phase hydrolysis of titanium tetraisopropoxide(TTIP). The rate of TTIP hydrolysis was so fast that the overall rate of formation of $TiO_2$ was controlled by the rate of mixing of TTIP and $H_2O$. Thus, the primary $TiO_2$ particles were prepared in nano sizes to form chainlike aggregates due to rapid coagulation. The pure $TiO_2$ particles as prepared were amorphous at the reactor set temperatures below $400^{\circ}C$ and became anatase at the temperatures of $450^{\circ}C$ above while the weak rutile peaks were also observed above $800^{\circ}C$. The actual size of primary particles as prepared were reduced by increasing the reactor set temperature while their crystalline sizes as well as BET sizes increased by post-sintering.

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A Study on the Application of the Optimal Control System for Heat Source and HVAC System (열원 및 공조설비의 최적제어시스템 현장 적용성에 관한 연구)

  • Baek, Seung-Jae;Kim, Jin;Ahn, Byung-Cheon;Song, Jae-Yeob
    • Proceedings of the SAREK Conference
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    • pp.1014-1019
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    • 2009
  • The optimal control system for heat source and HVAC system has been developed for minimizing energy consumption while maintaining the comfort of indoor thermal environment in terms of the environmental variables such as time varying indoor load and outdoor temperatures. The optimal set-points of control parameters are supply air temperature and chilled or hot water temperatures. The optimal control study has been implemented for biosafety laboratory by using TRNSYS simulation program in order to investigate energy performance for heat source and HVAC system.

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Real Time Near Optimal Control Application Strategy for Heat Source and HVAC System (열원 및 공조설비 통합 최적제어기법 구현에 관한 연구)

  • Song, Jae-Yeob;Ahn, Byung-Cheon;Joo, Yong-Duk;Kim, Jin
    • Proceedings of the SAREK Conference
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    • pp.60-65
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    • 2008
  • The near-optimal control algorithm for central cooling and heating system has been developed for minimizing energy consumption while maintaining the comfort of indoor thermal environment in terms of the environmental variables such as time varying indoor load and outdoor temperatures. The optimal set-points of control parameters with near-optimal control are supply air and chilled or hot water temperatures. The near optimal control algorithm has been implemented by using LabVIEW program in order to analyze energy performance for central cooling and heating control system.

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Real Time Near Optimal Control Application Strategy of Central Cooling System (중앙냉방시스템의 실시간 준최적제어 적용에 따른 실험적 연구)

  • Ahn, Byung-Cheon;Song, Jae-Yeob;Joo, Yong-Duk;Kim, Jin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.7
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    • pp.470-477
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    • 2008
  • The near-optimal control algorithm for central cooling system has been developed for minimizing energy consumption while maintaining the comfort of indoor thermal environment in terms of the environmental variables such as time varying indoor cooling load and outdoor temperatures. The optimal set-points of control parameters with near-optimal control are supply air and chilled water temperatures. The near optimal control algorithm has been implemented by using LabVIEW program in order to analyze energy performance for central cooling control system.

Optimal Control Strategies for Energy Saving of Central Cooling System with Outdoor Air Temperature Changes (외기온도 변화특성을 고려한 중앙냉방시스템의 에너지 절감 최적제어에 관한 연구)

  • Park, Ki-Tae;Ahn, Byung-Cheon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.6
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    • pp.4260-4266
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    • 2015
  • In this study, the optimal control method for minimizing of energy consumption for central cooling system with proper occupant comfort level is researched by simulation. The optimal control method is that the optimal set temperatures such as the condenser water temperature, supply air temperature, and chilled water temperature with environment variable change such as outdoor air dry-bulb and wet-bulb temperatures are obtained by suggested optimal control algorithm with maximum and part building load. The TRNSYS program is used for system modeling and the control performances with the suggested optimal control method are compared with the existing control method of fixed set points. The suggested optimal control method shows better responses in energy consumption in comparison with existing control ones.

Development of a Drought Detection Indicator using MODIS Thermal Infrared Data

  • Park, Sun-Yurp
    • Korean Journal of Remote Sensing
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    • v.20 no.1
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    • pp.1-11
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    • 2004
  • Based on surface energy balance climatology, surface temperatures should respond to drying conditions well before plant response. To test this hypothesis, land surface temperatures (LST) derived from MODIS data were analyzed to determine how the data were correlated with climatic water balance variables and NDVI anomalies during a growing season in Western and Central Kansas. Daily MODIS data were integrated into weekly composites so that each composite data set included the maximum temperature recorded at each pixel during each composite period. Time-integrated, or cumulative values of the LST deviation standardized with mean air temperatures had significantly high correlation coefficients with SM, AE/PE, and MD/PE, ranging from 0.65 to 0.89. The Standardized Thermal Index (STI) is proposed in this study to accomplish the objective. The STI, based on surface temperatures standardized with observed mean air temperatures, had significant temporal relationships with the hydroclimatological factors. STI classes in all the composite periods also had a strong correlation with NDVI declines during a drought episode. Results showed that, based on LST, air temperature observations, and water budget analysis, NDVI declines below normal could be predicted as early as 8 weeks in advance in this study area.