Optimal Outside Airflow Control of an Integrated Air-Handling Unit System for Large Office Buildings

2004 ◽  
Vol 126 (1) ◽  
pp. 614-619 ◽  
Author(s):  
L. Song ◽  
M. Liu
Keyword(s):  
Air Temperature ◽  
Linear Optimization ◽  
Optimization Method ◽  
Geometric Optimization ◽  
Variable Air Volume ◽  
Unit System ◽  
Analytical Functions ◽  
Air Handling Unit ◽  
Conventional Systems ◽  
Air Control

This paper presents optimal outside air control schedules for an integrated air-handling unit system for large commercial buildings (OAHU). The schedules are developed using the geometric linear optimization method and expressed as analytical functions of the outside air temperature and enthalpy, the interior zone airflow ratio, and the exterior zone supply air temperature. The optimal outside air control schedules can be applied to both constant and variable air volume systems. When the schedules are implemented, the OAHU system can significantly improve indoor air quality (IAQ) and use significantly less thermal energy than conventional systems. The geometric optimization method can also be used in other linear HVAC optimizations with non-liner constraint conditions.

Optimal Outside Airflow Control of Integrated Air Handling Unit System for Large Office Buildings

Solar Energy ◽  
2003 ◽  
Author(s):  
L. Song ◽  
M. Liu
Keyword(s):  
Air Temperature ◽  
Linear Optimization ◽  
Optimization Method ◽  
Geometric Optimization ◽  
Variable Air Volume ◽  
Unit System ◽  
Analytical Functions ◽  
Air Handling Unit ◽  
Conventional Systems ◽  
Air Control

This paper presents the optimal outside air control in the integrated air handling unit system for large commercial buildings (OAHU). The optimal outside air control schedules are developed using the geometric linear optimization method, and expressed as analytical functions of the outside air temperature and enthalpy, the interior zone airflow ratio, and the exterior zone supply air temperature. The optimal outside air control schedules can be applied to both constant and variable air volume systems. When the optimal outside air control schedules are implemented, the OAHU system can significantly improve indoor air quality (IAQ) and use significantly less thermal energy than conventional systems. The geometric optimization method can also be used in other linear HVAC optimizations with non-liner constraint conditions.

scholarly journals Optimal Airflow Control of Laboratory Air Handling Unit (LAHU) Systems

2004 ◽  
Vol 126 (2) ◽  
pp. 750-758 ◽  
Author(s):  
Yujie Cui ◽  
Mingsheng Liu ◽  
Kirk Conger
Keyword(s):  
Linear Optimization ◽  
Weather Conditions ◽  
Optimization Method ◽  
Energy Characteristics ◽  
Laboratory Section ◽  
Air Handling Unit ◽  
Air Temperatures ◽  
Laboratory Supply ◽  
Air Intake ◽  
Air Control

The Laboratory Air Handling Unit (LAHU) system conditions both the office section and the laboratory section. It improves indoor air quality by maximizing outside air intake to the office section and minimizes thermal energy consumption by re-circulating the office section air to the laboratory section. This paper presents a theoretical linear optimization method and results of optimal outside air control in LAHUs. The optimal outside airflows are expressed as functions of the weather conditions (outside air temperature and enthalpy), office and laboratory airflow rates, office and laboratory supply air temperatures, and four dimensionless parameters that describe the building system and energy characteristics. The optimization method used in this paper can be used to identify the optimal control schedules in other HVAC systems.

Optimal Minimum Airflow for Air Circulation of Single-Duct VAV Terminal Boxes

2008 ◽  
Author(s):  
Young-Hum Cho ◽  
Mingsheng Liu
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Discomfort ◽  
Variable Air Volume ◽  
Air Handling Unit ◽  
Optimal Value ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Air Circulation ◽  
The Impact

Thermal comfort in an area is directly controlled by terminal boxes in variable air volume (VAV) air-handling unit (AHU) systems. The terminal box either modulates airflow or adjusts the discharge air temperature. Reduced air circulation will cause thermal discomfort in a conditioned space if the airflow and discharge air temperature are not suitable. The objective of this study is to identify an optimal value for airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature is analyzed, and the impact of room airflow and discharge air temperature on thermal stratification is verified through CFD (Computational Fluid Dynamics) simulations.

Effect of Minimum Airflow Setting of VAV Unit on Building Energy Consumption under Korean Climatic Condition

2012 ◽  
Vol 450-451 ◽  
pp. 1435-1439
Author(s):  
Kwang Ho Lee ◽  
Kyung Il Chin ◽  
Jong Ho Yoon
Keyword(s):  
Energy Consumption ◽  
Air Temperature ◽  
Variable Air Volume ◽  
Unit System ◽  
Energy Impact ◽  
Heating And Cooling ◽  
Significant Difference ◽  
Gas Consumption ◽  
Forced Air ◽  
The Impact

Variable Air Volume (VAV) unit system is one of the commonly used forced-air heating and cooling systems in office buildings. It controls the airflow with the discharge air temperature fixed for cooling, while the discharge air temperature is adjusted with the airflow fixed at the minimum for heating. This study presents the simulation of conventional VAV unit system performance applied in the typical office building prototype. Each VAV unit has the minimum airflow setting for the ventilation purpose and its impact on the energy consumption is significant. The aim of this study is to evaluate the energy impact of the minimum airflow setting of VAV box using EnergyPlus ver. 6.0 software platform. The energy result breakdown of three model cases is discussed: minimum airflow fraction setting of 10%, 20% and 30%. As a result, the minimum airflow setting has significant impact on the reheat energy and thus the annual boiler gas consumption shows significant difference among each simulation case. Monthly heating energy profile is also discussed for the better understanding of the impact of different minimum fractions on the heating energy.

Terminal Box Minimum Airflow Optimization of Single Duct Air Handling Units

2007 ◽  
Author(s):  
YoungHum Cho ◽  
Gang Wang ◽  
Mingsheng Liu
Keyword(s):  
Energy Consumption ◽  
Air Temperature ◽  
Thermal Environment ◽  
Variable Air Volume ◽  
Heating And Cooling ◽  
Air Handling Unit ◽  
Simultaneous Heating ◽  
Save Energy ◽  
Heating Loads ◽  
Simultaneous Heating And Cooling

Terminal boxes control space conditions in variable air volume (VAV) air-handling unit (AHU) systems. Terminal boxes either modulate airflow with a control damper or adjust discharge air temperature with a reheat coil. Terminal boxes will have a significant amount of simultaneous heating and cooling and AHUs will consume more fan power if the minimum airflow is higher than required. On the other hand, conditioned space will have indoor air quality (IAQ) problems with less air circulation if the minimum airflow is less than required. The objective of this study is to optimize the minimum airflow ratio to improve thermal environment and save energy consumption. In this study, the problem of current fixed minimum airflow ratio of terminal box is analyzed and variable minimum airflow ratio as an alternative is suggested. The results of this study show that variable minimum airflow ratio can stably maintain the set room air temperature and reduce energy consumption for varying heating loads compared to the conventional fixed minimum airflow ratio.

scholarly journals Fast Quadratic Shape From Shading With Unknown Light Direction

2021 ◽  
Author(s):  
Kuros Yalpani
Keyword(s):  
Linear Optimization ◽  
Quadratic Function ◽  
Optimization Method ◽  
Shape From Shading ◽  
Surface Patch ◽  
Algebraic Complexity ◽  
Surface Patches ◽  
Quadratic Surface ◽  
Least Squares Optimization ◽  
Light Source Direction

An algorithm is proposed that extracts 3D shape from shading information in a digital image. The algorithm assumes that there is only a single source of light producing the image, that the surface of the shape giving rise to the image is Lambertian (matte) and that its shape can be locally approximated by a quadratic function. Previous work shows that under these assumptions, robust shape from shading is possible, though slow for large images because a non-linear optimization method is applied in order to estimate local quadratic surface patches from image intensities. The work presented here shows that local quadratic surface patch estimates can be computed, without prior knowledge of the light source direction, via a linear least squares optimization, thus greatly improving the algebraic complexity and run-time of this existing algorithms.

scholarly journals CONSTRUCTAL DESIGN AND SIMULATED ANNEALING EMPLOYED FOR GEOMETRIC OPTIMIZATION OF A Y-SHAPED CAVITY INTRUDED INTO CONDUCTIVE WALL

2015 ◽  
Vol 14 (1) ◽  
pp. 79
Author(s):  
G. V. Gonzales ◽  
E. D. Dos Santos ◽  
L. R. Emmendorfer ◽  
L. A. Isoldi ◽  
E. S. D. Estrada ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Simulated Annealing ◽  
Solid Wall ◽  
Internal Heat ◽  
Optimization Methods ◽  
Optimization Method ◽  
Internal Heat Generation ◽  
Geometric Optimization ◽  
Constructal Design ◽  
Optimal Shapes

he problem study here is concerned with the geometrical evaluation of an isothermal Y-shaped cavity intruded into conducting solid wall with internal heat generation. The cavity acts as a sink of the heat generated into the solid. The main purpose here is to minimize the maximal excess of temperature (θmax) in the solid. Constructal Design, which is based on the objective and constraints principle, is employed to evaluate the geometries of Y-shaped cavity. Meanwhile, Simulated Annealing (SA) algorithm is employed as optimization method to seek for the best shapes. To validate the SA methodology, the results obtained with SA are compared with those achieved with Genetic Algorithm (GA) and Exaustive Search (ES) in recent studies of literature. The comparison between the optimization methods (SA, GA and ES) showed that Simulated Annealing is highly effective in the search for the optimal shapes of the studied case.

scholarly journals Diagnosis of Multiyear Predictability on Continental Scales

2011 ◽  
Vol 24 (19) ◽  
pp. 5108-5124 ◽  
Author(s):  
Liwei Jia ◽  
Timothy DelSole
Keyword(s):  
Time Scales ◽  
Air Temperature ◽  
Climate Models ◽  
Coupled Model ◽  
Surface Air Temperature ◽  
Optimization Method ◽  
First Year ◽  
Temperature And Precipitation ◽  
Regional Prediction ◽  
Intercomparison Project

A new statistical optimization method is used to identify components of surface air temperature and precipitation on six continents that are predictable in multiple climate models on multiyear time scales. The components are identified from unforced “control runs” of the Coupled Model Intercomparison Project phase 3 dataset. The leading predictable components can be calculated in independent control runs with statistically significant skill for 3–6 yr for surface air temperature and 1–3 yr for precipitation, depending on the continent, using a linear regression model with global sea surface temperature (SST) as a predictor. Typically, lag-correlation maps reveal that the leading predictable components of surface air temperature are related to two types of SST patterns: persistent patterns near the continent itself and an oscillatory ENSO-like pattern. The only exception is Europe, which has no significant ENSO relation. The leading predictable components of precipitation are significantly correlated with an ENSO-like SST pattern. No multiyear predictability of land precipitation could be verified in Europe. The squared multiple correlations of surface air temperature and precipitation for nonzero lags on each continent are less than 0.4 in the first year, implying that less than 40% of variations of the leading predictable component can be predicted from global SST. The predictable components describe the spatial structures that can be predicted on multiyear time scales in the absence of anthropogenic and natural forcing, and thus provide a scientific rationale for regional prediction on multiyear time scales.

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