Architectural Engineering -- Dissertations and Student Research

Evaluation of Statistical Energy Analysis for Prediction of Breakout Noise from Air Duct

Himanshu S. Malushte — Wed, 24 Apr 2013 13:35:29 PDT

The breakout noise from an air-conditioning duct is of immense concern in order to maintain a sound environment at home, office spaces, hospitals, etc. The challenge lies in correctly estimating the breakout noise by knowing the breakout sound transmission loss from the air duct. The ASHRAE Handbook: HVAC Applications (ASHRAE, 2011) currently lists some of theoretical transmission loss values for limited duct dimensions and gages (duct-wall thickness) at the octave band frequencies. Statistical Energy Analysis (SEA) is promising to predict the sound transmission loss for breakout noise for any given air duct configuration, particularly at high frequency. Though there are deterministic approaches such as finite element method (FEM) and boundary element method (BEM), they are unable to yield results efficiently for high frequency, while they also demand long computational time and memory. SEA on the contrary saves the computational effort and thus computational time. In this study, theoretical transmission loss of random duct configuration is selected from ASHRAE Handbook: HVAC Applications (ASHRAE, 2011) to evaluate the SEA method for correctly predicting the breakout sound transmission noise. All the applicable parameters for implementing SEA on a duct are discussed and the method is then simulated. The predicted results are then compared with the theoretical results (ASHRAE, 2011). Initially, there are some discrepancies between the predicted results by SEA and the theoretical results in transmission loss observed at higher frequencies. Further investigation leads to a formulation of a factor that is applied to the conventional SEA approach. The predicted results from the new formulation show a close agreement with the existing theoretical results and are mostly within 3 dB difference. The SEA predictions are also compared with the experimental data (Cummings 1983) to establish SEA’s validity. The SEA predicted results are also found to be close with the experimental results for the all the duct configurations and maintain agreement mostly within 3 dB.

Advisor: Siu-Kit Lau

PUMP CONTROLLER DESIGN FOR VARIABLE PRIMARY FLOW CONFIGURATION SYSTEMS

Yifan Shi — Fri, 15 Mar 2013 07:26:07 PDT

Pump systems are utilized widely in Heating, Ventilation and Air-Conditioning (HVAC) systems. There are mainly three configuration types: (1) the constant primary-only flow configuration, (2) the constant primary/variable secondary flow configuration, and (3) the variable primary-only flow configuration. This thesis focuses on finding the optimal control strategy for it and programming a controller for easy in-field usage.

In this thesis, the pump brake horse power (BHP) of the three pump configurations is simulated and compared using varying control methods. The best pump efficiency staging and DP reset control methods are implemented into the pump controller. A one month field experiment is performed in a chiller/boiler plant at the Western Nebraska Community College (WNCC) for the pump controller. The proposed control strategy is found to achieve an energy savings of 64.5% in comparison to the constant flow configuration.

Advisor: Josephine Lau

ELECTRICAL SIGNAL BASED FAULT DETECTION AND DIAGNOSIS FOR ROOFTOP UNITS

Yunhua Li — Fri, 07 Dec 2012 09:10:32 PST

Fault detection and diagnosis (FDD) technology, as an effective approach, could identify the occurrence of common faults on rooftop units (RTUs) at the initial stage and prevent them from becoming severe. Although great progress have been made on the approaches, algorithms, control integration and commercialization, the issues of reliability and cost‐effectiveness have not been completely solved yet. In this study, an electrical signal based fault detection and diagnosis method is proposed, which can be applied to the new and retrofitted RTUs with a variable frequency drive (VFD) installed for both indoor fan and compressor. This method could be implemented in the existing or add‐on controller without intruding into the refrigeration system and interrupting the system functioning. There are four steps to implement this method. The first thing is developing a performance baseline by trending the VFD speed, power, supply air temperature, outside air temperature and space temperature. The second one is real‐time monitoring the system operations. The occurrence of faults can be detected by comparing the actual performance data with the baseline. The next step is identifying one or multiple faults using their unique signatures. The last step is evaluating the system performance and giving a response based on the fault level: tolerate or give an alarm for repair. In this study, a literature review was presented firstly. The principles were introduced to provide theoretical foundation. Then, a series of experiments were conducted to investigate the relationships between the VFD power and common faults and other driving conditions. The signatures of individual fault were summarized. In order to build the system performance baseline, a series of models were developed including motor efficiency, belt efficiency, normal state fan power, compressor power, total power, and supply air temperature. Next, the FDD method was developed using the proposed models. Finally, a group of field tests were carried out to demonstrate the feasibility and validity of the proposed method.

Adviser: Josephine Lau, Mingsheng Liu

INTEGRATED DEMAND CONTROL VENTILATION FOR SINGLE DUCT VAV SYSTEM WITH TERMINAL REHEAT

Bei Zhang — Fri, 07 Dec 2012 09:10:30 PST

Demand control ventilation (DCV) is one of the most energy efficient ways to achieve the optimum indoor air quality. It is capable of delivering the amount of outdoor air into the space as needed. ASHRAE 62.1 standard recommends the ventilation rate required for a space to protect public health. Thus, the study of DCV has to comply with ASHRAE standard or other similar standards.

Considering that the standard is updated every few years, the DCV methods studied under the previous standards also need review. In ASHRAE Standard 62.1-2004, the ventilation rate was updated with a building area related component, which makes the DCV more challenging to implement.

Although many studies have been conducted, gaps are still discovered since most of the studies are based on the similar assumptions about the Terminal Box (TBX) minimum airflow setting and normally ignore that the minimum airflow setting greatly influences the zone ventilation rate and system energy consumption.

In this dissertation, an innovative IDCV method is proposed, which studied the annual system energy consumption and indoor air quality in terms of zone CO₂ through simulation. Field experiment was conducted as well to validate the proposed method. The result of the proposed method is compared to the other two control methods. One is the widely applied method of setting the outdoor air damper at a fixed position, while the other one is the MZE method introduced in the ASHRAE standard. The simulation results showed that with the proposed method, the system energy consumption was significantly reduced. For cities from 16 climate zones in the US, about 2% to 27% savings was created when compared to the method of using 20% of TBX minimum setting, and 3% to 40% of annual savings was achieved when compared to the method of using 30% of TBX minimum setting. The experiment results showed that the proposed method reduced the airflow of TBXs by 20% and the supply fan speed by 11%. Results from both simulation and experiment demonstrated that the zone CO₂ level was well controlled by the proposed method.

Advisers: Josephine Lau and Mingsheng Liu

Effects of Short Noise Bursts on Human Performance and Perception

Christopher Ainley — Thu, 29 Nov 2012 06:50:29 PST

The goal of this research project is to better quantify human reactions to short bursts of noise, to complement research at NASA Langley Research Center on evaluating human response inside buildings to low-level sonic booms. The project involved exposing participants over 30-minute sessions to a number of 250 ms broadband noise bursts of certain levels, presented in a controlled yet randomized fashion throughout the session, and gathering responses on human perception and performance on an arithmetic task dealing with short-term memory. While previous research has demonstrated effects of noise bursts of varying amplitudes on other types of tasks that study cognitive processing including attention and at louder levels on this arithmetic task (i.e. 100 dB peak), more information is needed to indicate at what level and to what degree such noise bursts may impact human performance and perception.

Twenty-seven test subjects were tested over multiple 30-minute test sessions, with four different levels of the noise bursts. The noise bursts ranged from peak A-weighted sound pressure levels (L_Apk) of 47 to 77 dBA presented over an ambient background noise level of 37 dB L_eq measured over 2 minutes, or RC-29 (H).

Few significant relationships were found in relation to task performance, although there are still some general trends including an increase in incorrect answers for impulse-presented test questions as the noise burst level increases. Results show significant relationships, pApkaround 67 dBA and higher may not be considered acceptable in an otherwise ambient background noise level condition, in this case RC-29(H).

Adviser: Lily M. Wang

An Innovative Solution Set Of Algorithm For Converting Architectural Drawings To Vector-based Computer Graphics

Yuye Peng — Mon, 30 Jul 2012 08:46:05 PDT

Appraisal Floor Plan Sketch (AFPS) as a simplified architectural floor plan shows the bird's eye view of a building’s spatial arrangement. An efficient automated vectorization system of AFPS not only fulfills AFPS’s preservation and dissemination purposes but also helps extract the building’s geometric information, which can be used to create 3D models of the building and improve building energy efficiency. The purpose of this study is to develop an automated system for converting scanned AFPS into vector based computer graphics.

Text/graphic separation and corner detection are two essential components in this vectorization system. Text/graphic separation ensures that only graphic data is processed. Corner detection locates the dominant points to help extract vectors from image data. Image processing and analysis techniques were applied and an innovative set of algorithms was developed to extract digitized information from AFPS. Two hundred AFPS images, sampled from a large local online database containing more than 150,000 houses, were converted with fast processing speed (25 seconds on average), high confidence and accuracy level (95%), and minimal fault warning (1%).

Adviser: Haorong Li

Damage Detection in Metamorphic Stone Blocks Utilizing Impact-echo Testing and Modal Analysis

Alexander C. Jording — Thu, 26 Apr 2012 06:58:56 PDT

Existing buildings decay with the passage of time, and as a result, continually require maintenance or rehabilitation. When considering existing structures, testing is often necessary to complete structural analysis in preparation for rehabilitation or repair. Non-destructive testing provides a structural assessment method applicable to a variety of materials and structures. The hypothesis of this research is that impact-echo testing, one of the many NDT techniques, can be adopted to develop a reliable and standardized method to assess the condition of rectangular metamorphic stones. After the baseline material parameters and general response to impact-echo testing were established, a novel method to perform real-time on-site block assessments was developed. The methodology is developed using an international research project at Antiochia ad Cragum, near present-day Gazipaşa, Turkey, as a case study for structural assessment conditions. Blocks from the 3^rd century Imperial Roman temple at Antiochia ad Cragum, serve as the primary reference for this study. Theoretical values based on eigenvalue analysis when compared with finite element analysis results provided a correlation to within 2.4%. Frequencies from impact-echo testing from a sample block cast out of a similar density material are compared with theoretical eigenvalue analysis values, resulting in errors of less than 6%. As a result of this research, existing impact-echo methods have been validated for applicability on metamorphic stones and mortar blocks. Furthermore, a real-time impact-echo analysis program has been developed to assess stones and characterize their structural integrity simultaneously. These findings will benefit engineering and archaeological research teams wishing to evaluate rectangular stones. In addition, these techniques and methods, with minimal alteration, can be applied to a variety of materials including other types of stone, concrete, and even wood.

Adviser: Ece Erdogmus

A Composite Structural Steel and Prestressed Concrete Beam for Building Floor Systems

Nathan deWit — Tue, 24 Apr 2012 08:39:45 PDT

Precast prestressed concrete beams, such as rectangular and inverted tee beam, currently used in residential and commercial buildings are deep, heavy, and limited to span-to-depth ratios of 15. The research proposes a composite structural steel and prestressed concrete beam that is shallow, light, easy to produce and erect, and able to achieve a span-to-depth ratio of 24. The proposed beam is designed to be used with precast columns, hollow-core planks, and a cast-in-place topping to create a moment-resisting floor system that minimizes the need for shear walls. The goal of this system is to eliminate as many of the limitations of precast concrete buildings as possible while remaining economically competitive. The developed beams consists of one half of a standard steel W-section, embedded into the top of a shallow rectangular prestressed concrete bottom flange, to create a composite section that supports hollow-core planks. Cast-in-place concrete is then used to fill the voids between the hollow-cores and composite beam and provide a leveled topping. A typical commercial building was analyzed and designed using the proposed beam under normal loading conditions. This design example indicated that the proposed system is economical, shallower, lighter, and more resistant to lateral loads than conventional precast concrete floor systems.

Adviser: George Morcous

ELECTROMAGNETIC HARVESTING TO POWER ENERGY MANAGEMENT SENSORS IN THE BUILT ENVIRONMENT

Evans Sordiashie — Mon, 23 Apr 2012 09:24:32 PDT

Recently, a growing body of scholarly work in the field of energy conservation is focusing on the implementation of energy management sensors in the power distribution system. Since most of these sensors are either battery operated or hardwired to the existing power distribution system, their use comes with major drawbacks. Battery maintenance and associated labor costs can make implementing sensors very expensive. Although hardwired sensors require very little post-installation maintenance, any energy savings they may procure is offset by the amount of energy expended during the course of the sensors normal operation. In response to these energy challenges, this thesis proposes an electromagnetic harvesting device that powers such sensor technologies by scavenging low electromagnetic field energy. First, the quantities of magnetic flux densities around common current carrying conductors in the built environment are estimated according to the equivalent amount of power that can be generated. Then, a prototype of the harvesting device for scavenging low magnetic flux is designed and developed. Finally, the device is evaluated for real-world implementation using a novel prototype board.

Adviser: Mahmoud Alahmad

THE ASSESSMENT OF HIGH DYNAMIC RANGE LUMINANCE MEASUREMENTS WITH LED LIGHTING

Yulia I. Tyukhova — Thu, 19 Apr 2012 06:53:22 PDT

This research investigates whether a High Dynamic Range Imaging (HDRI) technique can accurately capture luminance values of a single LED chip. Previous studies show that a digital camera with exposure capability can be used as a luminance mapping tool in a wide range of luminance values with an accuracy of 10%. Previous work has also demonstrated the ability of HDRI to capture a rapidly-changing lighting environment with the sun. However these publications don’t investigate HDRI’s ability to capture a bright light source with a narrow light distribution (LED lighting).

Some of the existing concerns in LED technology today include low quality products on the market, inaccurate performance claims, and insufficient information on Solid-State Lighting (SSL) products. Division 2 in the International Commission on Illumination (CIE) (Physical Measurement of Light and Radiation) prepares the technical report (TC2-58) on measuring LED radiance and luminance; however progress has not yet been published. Manufacturers do not provide luminance data on their products even though luminance is the most important quantity in lighting design and illuminating engineering. It is one of the direct stimuli to vision, and many measures of performance and perception.

In this research two conventional luminance measurement methods of a single LED chip are implemented. One method involves the use of a luminance meter with a close-up lens, and the other method allows obtaining luminance through calculations from the illuminance measurements. Luminous intensity data can be determined using direct illuminance measurements taken in a created photometer. These data along with dimensions of an LED can then be used to calculate average luminance.

Varying apertures and shutter speeds in a digital camera allows obtaining a sequence of images with different exposures. These images are combined together using software to create an HDRI that gives pixel by pixel luminance values. The HDRI of a single LED chip is obtained using a neutral density filter. The results of this research indicate that the HDRI technique can capture luminance values of a single LED chip.

Adviser: Clarence Waters

A Numerical Investigation of Two Phase Solar-Collector Pipe

Seyyed Hashem Abedini — Wed, 18 Apr 2012 10:15:16 PDT

In the United States, major portions of the annual electrical and primary energy are consumed for buildings. To help reduce the energy consumption of non-renewable energy sources, this study investigates a new technology for harvesting solar energy using a boiling-condensing cycle with water in a solar collector. The fluid circulation is under natural forced convection. A solar collector is made of a black lacquer copper with 2 meters in length is used. The design of the system is presented to simulate heat transfer rate in a cold climate an average daily solar irradiation of 4.5kWh/m2/day, e.g. for Omaha Nebraska. The tube surface temperature is calculated based on specified ambient temperature and solar radiation, i.e. 302.6K. A constant tube surface temperature is considered in this simulation-based study. The solar collector will not freeze since this system uses the lower pressure inside the tube. The correlations for the heat transfer coefficients in non-boiling and boiling regions are presented. This study analyzes the heat transfer development of a single phase flow and two-phase flow boiling process in different regions such as subcooled flow region, saturated flow boiling region and vapor region in various pressures. This research investigates how to maximize heat transfer in a single vertical tube. The proper subcooled flow region in the overall tube length and also a specific pressure are optimized and estimated to calculate the maximum total heat transfer rate in a solar collector. It is concluded that the maximum heat transfer rate will be obtained when the vapor region is minimized and the subcooled and saturation region are maximized in overall tube length.

Residential Energy Recovery Radiant Heat System

Scott Sharp — Fri, 06 Apr 2012 13:13:56 PDT

Energy recovery systems aim to recover waste energy that is normally lost to the environment. Waste energy comes in a variety of forms. Many processes involving building HVAC involves transferring energy from one working fluid to another. Governing codes put strict requirements on ventilation requirements for various occupancy types. Increased ventilation demands more from the HVAC equipment since outdoor air (ventilation air) is being brought into the building and requires tempering in order to retain occupant comfort. The energy required to temper this air increases as ventilation rates increase. Many commercial buildings have implemented exhaust air energy recovery, or runaround loops in order to re-capture the energy in the exhaust air streams.

Residential HVAC systems are no different than commercial systems, just less complex typically. There is little being done to recover energy lost in the residential sector. The commercial industry is much further along in energy recovery systems than the residential sector. This is partially due to the lack of interest by home owners. Residential buildings consumed 35% of the total U.S. natural gas consumption in 2008 accounting for more than $90 billion dollars annually. Typical residential furnaces are 80% thermally efficient. The wasted energy is largely found in the combustion products,or flue gasses. By recovering heat from the flue gases, this energy can be reclaimed and put to use.

Having a source for energy recovery is only part of the predicament. A desirable application of the recovered energy is also necessary. Home owners need to see a quick payback as well as an incentive in order to be enticed to make capital investments. Without government aid or tax incentives many individuals lose interest.

This thesis researches using energy recovery from residential gas furnaces to apply reclaimed heat to a radiant driveway heating system. The incentive for this application is the not only a maintenance free driveway in the winter, but reduced costs for snow removal.

Adviser: Haorong Li

ANN BASED LOAD IDENTIFICATION AND FORECASTING SYSTEM FOR THE BUILT ENVIRONMENT

Hosen Hasna — Mon, 05 Dec 2011 07:28:47 PST

"Phantom Loads" cause energy waste in homes and the built environment as a whole. Consumers spend more than $3 billion a year on "Phantom Load" in the United States alone. The goal of this work is to conserve energy by increasing consumer awareness on their energy usage and appropriate tools which in turn will be reducing and /or eliminating phantom loads and mismanagement of the load in the built environment. A further goal is to improve upon existing power distribution systems in the built environment with limited hardware additions to increase energy conservation. This work investigates remote identification of load types along the electrical circuitry where they (load) are being consumed. The load type and status (on, off, standby) are determined both remotely and in a non-intrusive manner using Non-Intrusive Load Monitoring Methods. Finally we added the short term for load forecasting were we will be able to predict the demand kW and leave the ability of using that for energy management strategies like load shifting and demand limiting.

OPTIMIZED CONTROL STRATEGIES FOR A TYPICAL WATER LOOP HEAT PUMP SYSTEM

Xu Lian — Mon, 25 Jul 2011 14:03:57 PDT

Water Loop Heat Pump (WLHP) System has been widely utilized in the Heating, Ventilating and Air Conditioning (HVAC) industry for several decades. There is no doubt about the energy saving potential of this type of system from the design and construction perspective. However, there are still many unsolved problems, such as high loop pump energy consumption, low heat pump efficiency and high electricity cost due to improper operation, although the system design intension was to save energy. Thus, how to control the WSHP to realize its energy-efficient value is an innovative but practical topic on which this thesis will focus.

To achieve this goal, three optimal WLHP control strategies will be discussed in this thesis:

(1) Improve the water loop circulation pump control by using a differential pressure reset method;

(2) Optimize the water loop temperature control by resetting the fluid cooler supply temperature;

(3) Modify the building schedule and heat pump fan operation mode to save energy without sacrificing occupant comfort.

These new control strategies were implemented on a middle school building equipped with a very typical WLHP system in a building mechanical system commissioning project. Several experiments were conducted in order to demonstrate the energy savings and other benefits compared with the existing control and operation.

It is concluded from the results of the experiments that the new loop pump control reduced the pump speed by 16.3% on average and has the potential to save 40% to 70% pumping energy; the improved water loop temperature control saved 12.8% of heat pump electricity consumption; and the new HVAC operating schedule and heat pump fan mode are able to achieve 20% to 30% of total electricity savings annually.

Advisor: Mingsheng Liu

IMPLEMENTATION OF INTEGRATED COMMISSIONING, RETROFITS, AND CONTROL OPTIMIZATION PROCESS IN A SMALL COMMERCIAL BUILDING

Xiangnan Shi — Mon, 25 Jul 2011 13:22:30 PDT

A large amount of the primary energy consumed in the US is derived from the built environment followed by energy consumed in the transportation and industrial sectors. Consequently, improving the energy efficiency of buildings is an important part of ensuring a more sustainable world for future generations. Of the various techniques employed to improve the energy efficiency of buildings, commissioning and retrofits continue to be the most widely applied solutions. Control optimization, mainly imbedded with continuous commissioning so far, is not applied as widely. Even though there are currently a few applications that integrate all three techniques, no comparison has been made between the integrated process and conventional process. The objective of this research is thus to conduct such a comparison.

This thesis begins with a review of the applications for commissioning, retrofits, and control optimization of existing buildings. Then, to compare the conventional commissioning and retrofit process with integrated process, a case demonstration is applied to an existing small commercial building.

Study results indicate that in this existing commercial building, conventional retrofits should not be implemented without commissioning because of long simple payback period. The integrated process is more cost effective than conventional process. It can achieve Net Present Value (NPV) of 251,390$ during a 20-years span, which is 2.82 times of commissioning-only process and 1.62 times of combined commissioning and retrofits process.

Adviser: Mingsheng Liu

ADAPTIVE PHOTOVOLTAIC CONFIGURATIONS FOR DECREASING THE ELECTRICAL MISMATCHING LOSSES

Mohamed Amer Chaaban — Fri, 22 Apr 2011 13:10:16 PDT

Electrical mismatching losses in photovoltaic systems are of great interest to system designers. In this thesis, an adaptive photovoltaic (PV) system is proposed based on novel flexible switch matrixes that form different possible topologies. This system maximizes the generated power in real-time for utility interactive systems in a modified inverter configuration. The proposed system uses fewer components and achieves maximum efficiency during shading and module mismatches by reconfiguring the PV modules based on real-time solar insolation, current operational conditions, and maximum efficiency criterion. Simulation tools are used to demonstrate that the proposed topologies provide improvement in efficiency over existing traditional PV systems. Furthermore, a prototype has been designed and developed. Experimental results for efficiency comparison between traditional PV system configurations are described in this work. Potential improvement using the proposed adaptive configuration is analyzed. The overall results validate the adaptive system and its benefits for a wide range of applications.

Advisor: Mahmoud Alahmad

REAL-TIME POWER MONITORING, HOME AUTOMATION AND SUSTAINABILITY

Wisam Nader — Fri, 22 Apr 2011 12:51:25 PDT

As the supply and demand of electrical energy is challenged within the context of environmental awareness and national security, the need to evaluate and advance each side is growing in importance. The electrical distribution system plays a critical role in the built environment as it is an enabling product, an intangible necessity used to power our systems. In order to manage our energy and prevent the consequences caused by energy wastage we need to develop tools for the built environment to become elastic with its consumption to respond to the national smart grid. To advance the research in this field, ZNETH‘s (Zero-Net Energy Test Home) Power Monitor (ZPM) is proposed and implemented in which end-use detailed energy consumption data is provided for each Node in the building. The data is shown on a display panel and stored as an Excel file to facilitate further processing. This data is displayed on the computer screen via a novel virtual environment building system. The virtual environment gives residents immediate access to the building power consumption information in a user-friendly format. This thesis details the ZPM system and the process that leads to its creation. The basic components of the proposed system were designed and tested using a prototype board.

Adviser: Mahmoud Alahmad

Investigations of the relationships between unoccupied classroom acoustical conditions and elementary student achievement

Lauren M. Ronsse — Thu, 21 Apr 2011 20:47:53 PDT

Current building standards recommend specific unoccupied background noise levels and reverberation times for classroom spaces. While clear communication in elementary school classrooms may be critical for successful learning environments, the existing research does not show a consistent connection between the classroom acoustics parameters specified in building standards and student achievement. This research seeks to determine what acoustical conditions should be attained in elementary school classrooms to optimize student achievement.

In this dissertation, acoustical studies in two midwestern United States public school systems are described. Unoccupied background noise level (BNL) and reverberation time (RT) measurements were gathered in a range of elementary school classrooms (125 total). Additionally, detailed binaural room impulse response (BRIR) measurements were gathered in 24 of these classrooms. For the BRIR measurements, a source loudspeaker with a directivity pattern similar to that of a human talker was used. The loudspeaker was placed at the front of each room at varying rotation angles to simulate a teacher facing different directions while speaking to the class. Multiple receiver positions at typical student locations were used in each classroom. The metrics calculated from the BRIR measurements include perception-based parameters, such as speech transmission index (STI), distortion of frequency-smoothed magnitude (DFSM), interaural cross-correlation (IACC), and interaural level difference (ILD).

The results from this research suggest that elementary student reading and language subject areas may be negatively impacted by higher unoccupied BNLs. Also, classrooms with lower DFSMs generally had students with higher language achievement scores. However, the classrooms included in the study had a limited range of RTs. Therefore, further investigations are needed in classrooms with longer RTs to fully assess the relationships between classroom acoustical conditions and student achievement.

Advisor: Lily M. Wang

A VIRTUAL SUPPLY AIRFLOW RATE METER IN ROOFTOP AIR CONDITIONING UNITS

Daihong Yu — Wed, 20 Apr 2011 14:04:16 PDT

Virtual sensing technology aims to estimate difficult to measure, expensive, or new quantities by using multifarious mathematical models along with non-invasive and low-cost measurements. Such embedded intelligence is a key to improving the performance of building systems in terms of functionality, safety, energy efficiency, environmental impacts, and costs. Considering the progress that has been achieved over many various fields (e.g., process controls, automobiles, avionics, autonomous robots, telemedicine) within the last two decades, numerous intelligent features have been incorporated and enabled that would otherwise not be possible or economical.

To identify the potential opportunities and research/development needs of virtual sensing technology in building systems,

First, this thesis reviews the major milestones of virtual sensing development in other emerging fields and its formulation of development methodologies.

Second, the state-of-the-art in virtual sensing technology in building systems is summarized as a starting point for its future developments and applications.

After that, a cost-effective virtual supply airflow (SCFM ) meter for rooftop air-conditioning units (RTUs) is created by using a first-principle model in combination with accurate measurements of virtual or virtually calibrated temperature sensors (a virtual mixed air temperature sensor and a virtually calibrated supply air temperature sensor) as a supplementary example. Modeling of the virtual meter, uncertainty analysis, and experimental evaluation are performed through a wide range of laboratory testing in the development. The study reveals that the first-principle based virtual SCFM meter could accurately predict SCFM values for RTUs (uncertainty is ± 6.9%). This innovative application is promising with a number of merits, such as high cost-effectiveness, ease-of-implementation, long-term availability after one-time development, and generic characteristics for all RTUs with gas heating.

Significant research and developments are needed before virtual sensors become commonplace within buildings. It is believed a wealth of virtual sensing derived applications would facilitate the sustainable management and optimize the advanced controls in building systems. It is hoped that this study can provide a resource for future developments.

A VIRTUAL SUPPLY AIRFLOW RATE METER IN ROOFTOP AIR CONDITIONING UNITS

Daihong Yu — Mon, 18 Apr 2011 08:14:00 PDT

To identify the potential opportunities and research/development needs of virtual sensing technology in building systems,

First, this thesis reviews the major milestones of virtual sensing development in other emerging fields and its formulation of development methodologies.

Second, the state-of-the-art in virtual sensing technology in building systems is summarized as a starting point for its future developments and applications.