Papers by peter armstrong
AIP Conference Proceedings, 2017
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Solar Energy, 2018
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Energy and Buildings, 2015
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The key to cost-effective on-line fault detection and diagnosis (FDD) may be in finding just the ... more The key to cost-effective on-line fault detection and diagnosis (FDD) may be in finding just the right mix of reliable sensors and automated analysis techniques to detect faults before they result in costly consequential damage. Much attention has been focused on temperature- and pressure-based fault detection of the vapor compression cycle of rooftop cooling equipment (Rossi and Braun 1997). However, temperature sensors must be installed in specific locations regardless of the resulting susceptibility to harsh environments or damage during inspection and service activities. Considering both long-term sensor reliability and suitability for detecting a broad spectrum of common faults in rooftop equipment, less intrusive power sensors coupled with power signature analysis (PSA) techniques may provide an attractive alternative to the temperature- and pressure-based FDD methods currently in development. The non-intrusive load monitor (NILM) was first conceived as a device to track end-use loads at the building service entrance based on step change in power and reactive power (Hart 1992). Subsequent MIT development identified loads by sampling voltage and current at high rates and reducing the resulting step changes, start transients, and harmonic content to concise “signatures ” (Leeb 1993, Shaw et al.
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Applied Energy, 2010
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Hvac&r Research, 2011
A modular variable-speed heat pump model is developed from first principles. The system model con... more A modular variable-speed heat pump model is developed from first principles. The system model consists of steady-state evaporator, compressor, and condenser component sub-models. The compressor model currently implemented accounts for re-expansion, valve pressure drop, and back leakage using empirical coefficients obtained from tests covering a wide range of pressure ratio and shaft speed. Variations in heat transfer coefficients with refrigerant
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Energy and Buildings, 2014
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Non-intrusive load monitoring (NILM) is accomplished by sampling voltage and current at high rate... more Non-intrusive load monitoring (NILM) is accomplished by sampling voltage and current at high rates and reducing the resulting start transients or harmonic content to concise load “signatures.” Changes in these signatures can be used to detect, and possibly diagnose, equipment and component faults associated with roof-top cooling units. NILM-based fault detection and diagnosis (FDD) is important because 1) it complements other FDD schemes that are based on thermo-fluid sensors and analyses and 2) it is minimally intrusive (one measuring point in the relatively protected confines of the control panel) and therefore inherently reliable. This paper describes changes in the power signatures of fans and compressors that were found, experimentally and theoretically, to be useful for fault detection.
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Estimates of daily electrical cooling load for a city of 800,000 are developed based on the relat... more Estimates of daily electrical cooling load for a city of 800,000 are developed based on the relationship between weather variables and daily-average electricity consumption over 1 year. The relationship is found to be nearly linear above a threshold temperature. Temperature and humidity were found to be the largest, at 59%, and second largest, at 21%, contributors to electrical cooling load. Direct normal irradiation intercepted by a vertical cylinder, DNI sin , was found to be a useful explanatory variable when modeling aggregates of buildings without a known or dominant orientation. The best study case
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The presence of liquid refrigerant in the compressor cylinder during operation, or liquid sluggin... more The presence of liquid refrigerant in the compressor cylinder during operation, or liquid slugging, is one of the most common causes of failure in reciprocating compressors. We propose to detect this fault by analyzing the electrical current flowing into the compressor and identifying the chan ge in the load on the motor caused by the presence of liquid in the compressor cylinder. Two different types of liquid slugging are examined in this paper. In the first, small volumes of liquid are ingested during the steady-state operation of the compressor; in the second, small volumes of liquid are present at the suction port of the compressor immediately prior to the compressor start. Experimental data from a 1-ton split air conditioning system is used to demonstrate methods for identifying these faults.
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A low cost, field-deployable instrument for retrieving the radial profile of solar radiance acros... more A low cost, field-deployable instrument for retrieving the radial profile of solar radiance across the sun´s disk and trough the circumsolar region is described. A prototype of the sunshape Profiling Irradiometer (SPI) has been built by modifying a stepping.motor-based Rotating Shadowband Irradiometer (RSI) with straghtforward changes to the control and data collection program and mechanical modifications that are novel but simple. A slit, rather than circular, reciever aperture is disposed on the bank axis such that penumbra crosses the aperture with a very small angualar displacement of the shadowband. because a single detectzor with diffusing fore-optic is used to generate the sunshape profiles, calibrationa nd soliling problems commonly associated with high resolution cameras are avoided. The circumsolar ratio (CSR) of the generated SPI trajectory is estimatedby finding the best match of the normalized measured profile to the family of simulated profiles using a single-parameter...
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Dedicated outdoor air systems (DOAS) make use of the sensible and latent capacity of the return (... more Dedicated outdoor air systems (DOAS) make use of the sensible and latent capacity of the return (exhaust) air to cool and dehumidify the supply (outside) air. “Closed DAOS” is an advanced form of typical DOAS with desuperheater and evaporatively cooled condenser in the return air stream. The air entering the condenser in Closed DOAS is in the fully saturated state. In order to fully saturate the return air, it needs to be sprayed by water. Sufficient amounts of water is required for fully saturating the air and keeping the coils of the condenser wet during the process. This water is obtained internally as a result of condensation on the evaporator fins, not requiring additional water use at the buildings site. Closed packaged configuration requires to have a water balance of water obtained in evaporator to that required for saturating the air and wetting the condenser coil. This water balance can be achieved under most conditions by an optimal control of enthalpy wheel and heat whee...
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Sustainability
In many cities that have experienced rapid growth like Abu Dhabi, urban microclimate scenarios ev... more In many cities that have experienced rapid growth like Abu Dhabi, urban microclimate scenarios evolve rapidly as well and it is important to study the urban thermal dynamics continuously. The Local Climate Zone (LCZ) classification considers factors related to the physical properties like surface cover and surface structure of the city which allow to analyze urban heat flows. Abu Dhabi city is rapidly expanding and is characterized by highly heterogeneous types of built forms that comprise mainly of old mid-rise and modern high-rise buildings with varied degrees of vegetation cover in different parts of the city. The fact that it is a coastal city in a desert environment makes it quite unique. This paper presents an approach of studying urban heat flows in such heterogeneous setup. First, the city is classified into local climate zones using images acquired by Landsat Satellite. Numerical simulations are performed in the designated LCZs using a computational fluid dynamics software,...
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Ashrae Transactions, 2006
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A combined heat and power-configured microturbine system was evaluated as an alternative to grid-... more A combined heat and power-configured microturbine system was evaluated as an alternative to grid-supplied electric power. While off-grid, the system provides auxiliary power for gas-fired boilers and a portion of the domestic hot water for a 500-man barracks and kitchen. One-time tests were made of sound levels, stack emissions and power quality. Steady-state generating capacity dropped faster than the ratings
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Ashrae Transactions, Jun 1, 2001
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Papers by peter armstrong