Economizer cycles have been recognized as important energy conservation measures for building air handling systems and have been included in most Energy Management and Control Systems (EMCS). This report describes the psychrometric processes of the most commonly used economizer cycles and presents algorithms for implementing these cycles on a typical Energy Management and Control System. Economizer cycles included in this study are dry-bulb and enthalpy types, as applied to both dry coils and sprayed coils. In addition, an enhancement to the normal enthalpy economizer cycle algorithm is presented for dual-duct or multi-zone system which takes into account differences in the costs of heating energy and cooling energy. Computer program listings of the algorithms and sample input/output data are shown in the appendices. A brief discussion of common types of air handling systems is also given to help the reader better understand the application of the algorithms presented in this report .
A comparative analysis is made of the thermal performance of a small office building using various HVAC systems and commonly emDloyed strategies. The comparisons are made for seven geographical locations representing xyide climatic variations within the continental United States.Results were obtained for fan, space heating hot water, and chilled water energv consumption through hour-by-hour simulations using the BT.AST computer program. A small office building model was used in the simulations along with several HVAC systems; a constant volume reheat unit (serving the entire building), dual constant volume reheat units (serving separate zones of the building), and a variable air volume reheat unit. The strategies investigated included simply air temperature reset (constant, zone-controlled, and outdoor air-controlled), economy cycles (temperature and enthalpy), continuous conditioning versus conditioning only during occupied hours, changes in reheat set point temperature, and changes in minimum variable air volume ratio.For comparable control strategies, the variable-air volume terminal reheat system exhibited the least energy consumption for chilled water, hot water and circulating fan. The system incorporating two independently-operating constant volume terminal reheat units ranked second in energy consumption while the single constant volume terminal reheat unit ranked last.Changes in thermal performance resulting from implementing one strategy in place of or in combination with another were found to vary significantly by climate and the type of HVAC system employed.
Five gas-fired water heaters (four natural gas and one LP gas) were tested in laboratory with simulated home conditions to evaluate their flame roll-out characteristics.Simulated
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