Traditional air-handling unit (AHU) control systems link the position of the exhaust, recirculation, and outdoor air dampers. Laboratory tests of a variable-air-volume AHU using the traditional damper control approach revealed that outdoor air could enter the AHU through the exhaust air damper. This can negatively impact indoor air quality. This paper examines the conditions that lead to this phenomenon and presents a new control system that can help alleviate the problem. The new control system links only the position of the exhaust and recirculation air dampers.
Ventilation air change rate, local mean age-of-air, and interzonal ventilation air distribution were measured for two single-family homes and eight ventilation systems. A multizone, single-gas, tracer gas decay measurement technique was used. A single-story, slab-on-grade, 1350 ff house was tested in Las ~gas, Nevada, and a two-story, 3192ft2 house with basement was tested in Minneapolis, Minnesota.
This paper describes a procedure for deriving a dynamic model of an air-conditioned room (space) by applying physical laws to it. The room under control is divided into five zones. The dynamics of each zone can be described by a lumped-capacity model, and a total of I 5 linear differential equations can be obtained. The model parameters derived from this procedure can be numerically related to the overall heat transfer coefficients for the room, and the various significant time constants associated with the room envelope.
Samples of 31 different air filters, representative of the designs and efficiency range of those used in general ventilation, were tested at constant airflow. The complete array of ASHRAE Standard 52.1 tests was run on these filters, plus particle-size efficiency tests and tests measuring the reentrainment of dust from the filters when subjected to ultra-clean air flow. Additional samples of the same filters were then subjected to the same test array, except that VAV flow was simulated.
A lab house constructed in Pittsburgh has been used as a site for the comparative evaluation of several ventilation systems. The house was built to relatively high performance standards and is representative of the type of house that would be a candidate for a purposely designed ventilation system. The systems installed and tested were (1) supply fan, (2) exhaust fan, (3) heat recovery ventilator, (4) balanced flow fan, and (5) open pipe to the RA plenum.
A method has been developed to estimate the air leakage through high-use automatic doors. This air leakage is specified as a function of the rate of use of the door, the door geometry, and the pressure difference across the door. Two studies were carried out to obtain these results. One was a laboratory study of the discharge coefficients of doors of various geometries. The other was a field study of the times when automatic doors are open as a function of use.
For many years there has been an increasing rate of complaints on the air quality in nonindustrial buildings. The occupants suffer from many diseases especially problems of breathing. Besides other reasons the air-conditioning systems themselves pollute the indoor air because dust, aerosols and other substances deposit inside the system. Therefore an airconditioning system, which has been operating 26 years was investigated. The aim was to find the main pollution sources of the system and possibilities to eliminate them.
Relations between indoor neutral temperatures and outdoor temperatures are currently proposed as an "adaptive standard" to supplement ASHRAE Standard 55-1992. They rest on the 1998 ASHRAE database. Humphreys and Nicol drew attention to the depression of the regression coefficient by measurement and formulaic error in thermal comfort indices. This paper applies their suggested correction, and improves the precision of the relations. Comparison is made with similar relations from earlier data. The relation for unheated, naturally ventilated buildings has remained unchanged.
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