Browsing by Subject "carbon dioxide"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Energy Optimization of Air Handling Unit Using CO2 Data and Coil Performance
    (ASME, 2016-11) Razban, Ali; Edalatnoor, Arash; Goodman, David; Chen, Jie; Mechanical Engineering, School of Engineering and Technology
    Air handling unit systems (AHU) are the series of mechanical systems that regulate and circulate the air through the ducts inside the buildings. In a commercial setting, air handling units accounted for more than 50% of the total energy cost of the building in 2013. To make the system more energy efficient without compromising comfort, it is very important for building energy management personnel to have tools to monitor the system performance and optimize its operation. Models are needed to meet the needs. The objectives of this study were to (1) develop models for the AHU elements and (2) implement control strategies to improve energy efficiency without sacrificing room comfort based on the published American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) standard. In this study, algorithms were developed to model the energy usage for heating/cooling coils as well as fans for AHU. Enthalpy based effectiveness and Dry Wet coil methods were identified and compared for accuracy of evaluating the system performance. Two different types of control systems were modeled and the results were shown based on occupancy reflected by the collected the rooms’ CO2 data. Discrete On/Off and fuzzy logic controller techniques were simulated using Simulink Matlab software and compared based on energy reduction and system performance. The models were used on an AHU in one of the campus buildings. The data for model inputs were collected wirelessly from the building using fully function devices (FFD) and a pan coordinator to send/receive the data. Current building management system Metasys software was also used to get additional data. The AHU modeling was done using Engineering Equation Solver (EES) Software for the coils and subsystems. Moving Average technique was utilized to process the data. The models were validated by comparing the calculated results with these measured experimentally. Simulation results showed that in humid regions, where there is more than 45% of relative humidity, the dry wet coil method is the effective way to provide more accurate details of the heat transfer and energy usage of the AHU comparing to the enthalpy based effectiveness. Also results of fuzzy logic controller method show that 62% of the current return fan energy can be reduced weekly using this method without sacrificing the occupant comfort level comparing to the ON/OFF method. Energy consumption can be optimized inside the building using fuzzy logic controller. At the same time system performance can be increased by taking the appropriate steps to prevent the loss of static pressure in the ducts. The implementation of the method developed in this study will improve the energy efficiency of the AHU while the occupants comfort level stay intact.
  • Thumbnail Image
    Item
    Implementation of Continuous Capnography Is Associated With a Decreased Utilization of Blood Gases
    (2015-02) Rowan, Courtney M.; Speicher, Richard H.; Hedlund, Terri; Ahmed, Sheikh S.; Swigonski, Nancy L.; Department of Pediatrics, Indiana University School of Medicine
    Background Capnography provides a continuous, non-invasive monitoring of the CO2 to assess adequacy of ventilation and provide added safety features in mechanically ventilated patients by allowing for quick identification of unplanned extubation. These monitors may allow for decreased utilization of blood gases. The objective was to determine if implementation of continuous capnography monitoring decreases the utilization of blood gases resulting in decreased charges. Methods This is a retrospective review of a quality improvement project that compares the utilization of blood gases before and after the implementation of standard continuous capnography. The time period of April 2010 to September 2010 was compared to April 2011 to September 2011. Parameters collected included total number of blood gases analyzed, cost of blood gas analysis, ventilator and patient days. Results The total number of blood gases after the institution of end tidal CO2 monitoring decreased from 12,937 in 2009 and 13,171 in 2010 to 8,070 in 2011. The average number of blood gases per encounter decreased from 20.8 in 2009 and 21.6 in 2010 to 13.8 post intervention. The blood gases per ventilator day decreased from 4.94 in 2009 and 4.76 in 2010 to 3.30 post intervention. The total charge savings over a 6-month period was $880,496. Conclusions Continuous capnography resulted in a significant savings over a 6-month period by decreasing the utilization of blood gas measurements.