EFFECT OF SOME DESIGN PARAMETERS ON AIR TEMPERATURE DISTRIBUTION IN THE HIGHLY COOLED AIR CONDITIONING SYSTEMS

Abstract

Title: The Effect of Some Design Parameters on Air Temperature Distribution in Highly Cooled Air System.

Description: Highly cooled air distribution systems offer the thermal comfort at lower operating and primary costs when compared to the conventional air system. Supply air to the conditioned space at lower temperatures ranging from 5 to 10ºC resulting in lower air volume flow rates by about 30% compared with that required for the conventional air conditioning systems, which supply air to the conditioned space at temperatures ranging from 13 to 18 ºC. Consequently, the reduced air flow rates required smaller air ducts, smaller air handling units (AHUs), reduced fan energy consumption. For the improvements in indoor air quality, better results have been detected. It is strongly recommended carrying out life cycle analysis of using highly cooled air distribution systems versus conventional systems.

But the highly cooled air systems don’t much established because of some concerns such the condensation on surfaces and the fear from cold drafts formation which affect the human comfort. Review of the previous researches submitted in the field of highly cooled air and air temperature distribution and related indoor quality and feeling comfort. Computational Fluid Dynamics (CFD) governing equations and solution methods are explained in different turbulence modeling are represented. This research introduces a comparison between the comfort attained using highly-cooled and conventional air- conditioning systems using CFD simulation inside a 2-D room with height of 2.8 m and width of 2.9 m. The supply temperature for the conventional system is selected to be 13 and 8ºC for the highly cooled air system. Several arrangements of the supply return combination as well as the ceiling curvature were assessed using the air diffusion performance index, ADPI. Internal loads represented in constant heat flux from walls, ceiling and floor. Successful supply of the highly cooled air directly to the space at 8 ºC with a good mixing between the highly cooled air system and the room air streams. Results of each case figured and discussed through the specified air temperature and velocity contours and estimating the air diffusion performance index (ADPI)