ESL Theses and Dissertations

Recent Submissions

• Analysis of Innovative HVAC System Technologies and Their Application for Office Buildings in Hot and Humid Climates

  Tanskyi, Oleksandr (Energy Systems Laboratory, December 2010)

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  Abstract:

  ABSTRACT Analysis of Innovative HVAC System Technologies and Their Application for Office Buildings in Hot and Humid Climates. (December 2010) Oleksandr Tanskyi, B.S., National Technical University of Ukraine; M.S., National Technical University of Ukraine Co-Chairs of Advisory Committee: Dr. David E. Claridge Dr. Michael B. Pate The commercial buildings sector in the United States used 18% (17.93 Quads) of the U.S. primary energy in 2006. Office buildings are the largest single energy consumption category in the commercial buildings sector of the United States with annual energy consumption around 1.1 Quads. Traditional approaches used in commercial building designs are not adequate to save energy in both depth and scale. One of the most effective ways to reduce energy consumption is to improve energy performance of HVAC systems. High-performance HVAC systems and components, as well as application of renewable energy sources, were surveyed for buildings in hot and humid climates. An analysis of performance and energy saving potential estimation for selected HVAC systems in hot and humid climates was developed based on energy consumption simulation models in DOE-2.1E. A calibrated energy consumption model of an existing office building located in the hot and humid climate conditions of Texas was developed. Based on this model, the energy saving potential of the building was estimated. In addition, energy consumption simulation models were developed for a new office building, including simulation of energy saving measures that could be achieved with further improvements of HVAC system above the energy conservation codes requirements. The theoretical minimum energy consumption level for the same office building was estimated for the purpose of evaluating the whole building energy efficiency level. The theoretical minimum energy consumption model of the office building was designed to provide the same level of comfort and services to the building occupants as provided in the actual building simulation model. Finally, the energy efficiency of the building that satisfies valid energy conservation codes and the building with an improved HVAC system was estimated based on theoretically minimum energy consumption level. The analysis provided herein can be used for new building practitioners and existing building owners to evaluate energy reduction potential and the performance of innovative technologies such as dedicated outdoor air system, displacement ventilation, improved cooling system efficiency, air source heat pumps and natural gas heat pumps.

  URI:

  http://hdl.handle.net/1969.1/127954

  Files in this item: 1

  ESL-TH-10-12-01.pdf   (4.684Mb)
• The Effect of Alternate Defrost Strategies on the Reverse-Cycle Defrost of an Air-Source Heat Pump

  Schliesing, J. S. (Energy Systems Laboratory (http://esl.tamu.edu), August 1988)

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  Abstract:

  The effect of alternate defrost strategies on the transient performance of the air-source heat pump during the reverse-cycle defrost was investigated. Tests of a base-case heat pump configuration and defrost strategy were completed to provide a basis for performance evaluations of the alternate defrost strategies. The compressor and indoor coil fan operated continuously in the base-case defrost strategy, and the outdoor coil fan was stopped. Alternate defrost strategies utilized variations in fan and compressor operation during and after the defrost. Pre-starting of the outdoor coil fan prior to termination of the reverse-cycle defrost reduced pressure spikes commonly seen at defrost termination in the base-case defrost strategy. A strategy in which the compressor was stopped and the outdoor coil was allowed to drain of melted frost during the last three minutes of the defrost improved overall cyclic performance. Strategies which involved stopping of the indoor fan during defrost or delaying the start of the outdoor fan following defrost termination had a negative impact on defrost performance. A final strategy involved down-sizing of the heat pump compressor from 3.0 tons (36,000 btu/hr) capacity to 2.5 tons capacity. This alternate configuration had a comparable overall performance with the base-case while having a reduced frequency of required defrost periods.

  URI:

  http://hdl.handle.net/1969.1/94832

  Files in this item: 1

  ESL-TH-88-08-01.pdf   (29.66Mb)
• Development of a Transient Heat and Mass Transfer Model of Residential Attics to Predict Energy Savings Produced by the Use of Radiant Barriers

  Medina, M. A. (Energy Systems Laboratory (http://esl.tamu.edu), December 1992)

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  Abstract:

  A transient heat and mass transfer model was developed to predict ceiling heat gain/loss through the attic space in residences and to accurately estimate savings in cooling and heating loads produced by the use of radiant barriers. The model accounted for transient conduction, convection and radiation and incorporated moisture and air transport across the attic. Environmental variables such as solar loads on outer attic surfaces and sky temperatures were also estimated. The model was driven by hourly weather data which included: time, outdoor air temperature, horizontal sun and sky radiation, wind speed and direction, relative humidity (dew point), and cloud cover data. The outputs of the model were ceiling heat fluxes, inner and outer heat fluxes from all surfaces, inner and outer surface temperatures and attic air temperatures. Transient conduction was modeled using response factors. Response factors were calculated for each attic component based on construction type. Convective heat transfer was modeled using “flat plate” correlations found in the literature and radiative heat transfer was modeled using radiation enclosure theory. Moisture was incorporated via a condensation/evaporation model. A new procedure was developed to account for attic air stratification. Both forced and natural attic ventilation patterns were added to the model for three types of louver combination arrangements. An iterative technique was used to solve a set of simultaneous heat balance equations. The model predictions were compared to experimental data gathered throughout a three year experimental effort of side-by-side testing of attics retrofit with radiant barriers. The model was compared to the experimental data for a variety of situations which included: different attic insulation levels, various attic airflow rates, cooling and heating seasons, and different radiant barrier orientations. The model predicted ceiling heat flows within 10% for most cases. The model was used to run simulations and parametric studies under a diversity of climates, insulation levels and attic airflow patterns. Model predictions and results were presented on the basis of savings produced by the use of radiant barriers. Hourly, daily, and seasonal predictions by the model were in excellent agreement with observed experimental data and with literature.

  URI:

  http://hdl.handle.net/1969.1/94831

  Files in this item: 1

  ESL-TH-92-12-04.pdf   (5.868Mb)
• A Methodology for Baselining the Energy Use At Large Campus Utility Plants for the Purpose of Measuring Energy Savings from Energy Conservation Retrofits

  Beasley, R. C. (Energy Systems Laboratory (http://esl.tamu.edu), August 1999)

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  Abstract:

  The development of the energy services industry and the implementation of energy savings retrofits by energy services companies has increased the focus on the performance of energy saving retrofits. Energy savings measurement, though not an exact science, has been developing as well to ensure the benefit of a retrofit and to provide a level of assurance for the customers of energy services companies. This thesis presents a useful methodology for baselining campus utility usage using regression modeling techniques and measured daily data for the purpose of measuring energy savings. The methodology of this thesis improves upon previous regression modeling of individual buildings by extending commercial building energy usage models to an entire campus, modeling the operation of a central plant, and modeling central plant equipment performance with regression models. By adding equipment production layers, the user can more easily determine the cause of changes in the primary energy usage of a central plant. The case study for the application of the methodology of this thesis was the Texas A&M University main campus central plant. Useful results were obtained by utilizing one portion of the data to develop an energy usage baseline model and using the second portion of the data to validate the performance of the baseline model. Further development of the methodology could include the addition of an economic module and refinement of the model to incorporate the use of hourly data.

  URI:

  http://hdl.handle.net/1969.1/94830

  Files in this item: 1

  ESL-TH-99-08-01.pdf   (59.82Mb)
• Development of Empirical Temperature and Humidity-Based Degraded-Condition Indicators for Low-Tonnage Air Conditioners

  Watt, J. B. (Energy Systems Laboratory (http://esl.tamu.edu), December 1997)

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  Abstract:

  A split-system direct-expansion air conditioner was used to empirically determine temperature and return-air humidity indicators that could detect performance degradation resulting from degraded conditions. The air conditioner test bench was equipped with the ability to use either a short-tube orifice (STO) or a thermal expansion valve (TXV). The degraded conditions studied include low evaporator airflow, highand low-charge, and a blocked condenser coil. The work presented in this thesis is experimentally based which could identify degraded effects that fall outside of a simulation-based approach. It sought to utilize only low-cost temperature sensing means, although return-air humidity was an important factor for obtaining early detection over a wide range of operating conditions. It was empirically based rather than model based to reduce computation time with a real-time processor. Further, the current work differentiated between a system that uses a shorttube orifice (STO), or fixed-orifice expansion, and a system that uses a thermal expansion valve (TXV), or variable-orifice expansion. This thesis shows that low-cost temperature sensors could be used to detect the degraded conditions studied. However, it is also shown that indicators of low evaporator airflow depend on three loading factors; outdoor-air temperature, return-air temperature, and return-air humidity. In the literature, the humidity sensing point has been neglected by automated detection systems for failures and degraded conditions of low-tonnage air conditioners. The effects of the loading factors on the indicators relative to improper charge and a blocked condenser coil were not studied. Finally, while there were differences in the performance of a STO system and a TXV system relative to the degradations studied, a common set of indicators was identified that could detect degraded conditions without regard to the expansion device.

  URI:

  http://hdl.handle.net/1969.1/94784

  Files in this item: 1

  ESL-TH-97-12-03.pdf   (54.24Mb)