Evaluation of selected economizer and cold deck reset strategies for dual duct single fan AHUs in hot and humid climates /
The discharge air temperature reset, or deck reset, and economizer cycle are common heating, ventilating, and air conditioning (HVAC) energy saving control strategies. Significant savings have been achieved with finely tuned, outside air dependent, deck temperature settings. Likewise, the economiz...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2003.
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| Summary: | The discharge air temperature reset, or deck reset, and economizer cycle are common heating, ventilating, and air conditioning (HVAC) energy saving control strategies. Significant savings have been achieved with finely tuned, outside air dependent, deck temperature settings. Likewise, the economizer cycle has known potential to save cooling energy by varying the proportion of outside air supplied to the building air handler units in times of moderate or cool weather. The performance of these measures in a single duct HVAC system is fairly straightforward, along with their combined effect, but becomes more complicated for a dual duct air handling unit (AHU). Additional heating costs, or heating penalty, typically offsets some portion of the cooling energy savings in dual duct AHUs. This research studies the deck reset and economizer measures in dual duct, single fan, variable air volume (DDVAV) AHUs, with an emphasis on performance in hot and humid locations. An office and classroom building in a hot and humid Texas location was modeled and then simulated with combinations of these measures. These same simulated deck reset and economizer measures were also implemented in the building. Experimental data was obtained from February 8 through April 2 of 2001, and supported the simulated results. The building model was used for simulation of other hot and humid locations, such as Lake Charles Louisiana, Houston Texas, Atlanta Georgia, and Little Rock Arkansas. Additionally, more moderate weather locations in the United States were also simulated. Simulated results show savings ranging from 4.8 to 11.4% for optimum hot and cold deck reset schedules in the studied hot and humid locations, for the case of near equal cooling to heating energy costs. Savings of 9.5% were observed for the northern location of Madison Wisconsin for the same cost scenario, and Santa Maria California showed 16.6% savings. The simulation results for both temperature and enthalpy based economizer cycle operation indicated the heating energy cost must be less than the cooling energy cost for it to be of any real benefit. Otherwise the heating penalty, or extra heat load due to colder mixed air from economizer operation, negated the majority of the savings for all locations but Santa Maria. The heating penalty and the dramatic effect of the heating energy cost discourage the implementation of the economizer cycle in DDVAV systems having some similarity to the studied office and classroom building. Additionally, the information and experience of physically implementing the temperature and enthalpy economizer control strategies was invaluable. The difficulties encountered demonstrated the economizer cycle was more than a control algorithm. It required special effort and attention to ensure sensor error or mechanical system failure did not compromise proper execution of the economizer cycle control strategy. |
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| Item Description: | Vita. "Major subject: Mechanical Engineering". |
| Physical Description: | xiii, 152 leaves : illustrations ; 28 cm. Issued also on microfiche from Lange Micrographics. |
| Bibliography: | Includes bibliographical references (leaves 124-126). |