Fluid Flow Regimes in Air Conditioned Hall with Heat Source Equipment

Abstract

The present paper deals with experimental and numerical investigations of the influence of ventilation and air Conditioning supply and extract openings locations on room flow and thermal patterns in buildings. This work focuses on mechanical ventilation in industrial building. The effectiveness of a ventilation system is mainly determined by the removal of internally produced contaminants from the room (if any) and the supply of fresh air of acceptable quality in the room to replace contaminated air and reduce thermal load in inhabited zone. This is targeted to attain desired temperature regulation for human thermal comfort and machine safe operating thermal conditions. The present experimental facilities include a main room which is part of the pumping station complex having principal dimensions of 9 m long x 8m wide and 7m high. It includes mainly an electric motor driven screw pump; mounted on a concrete skid . The air supply comprises two short-ducted axial fans 0.483m diameter. The Extracted air side consists of a single roof extraction fan having the diameter of 0.76m with a specified fan duty of 3.82 m 3 /s. The main heat source has the overall dimensions of 1.5 m x 2.0m wide and 2.m high. Platinum Resistance thermometers were employed to measure local temperatures in the room and vicinity of heat source. On the other hand air velocity measurements were as low as 0.01 m/s and the turbulence intensity as high as 10%. The measuring probe, however, is omni-directional, the inaccuracy was in the order of 10 - 20% at 0.05 - 0.5 m/s and was regularly calibrated. The heat sources in the room create buoyant plumes that transport the air from the lower part (direct above the heat source) into the higher zones through entrainment. The velocity distributions have been measured at same vertical planes above the heat source similar to those of the temperature measurements. A numerical study was carried out to define the optimum airside design of the HVAC systems that provides the optimum ventilation and energy utilization. The present model is packaged as a Computational Fluid Dynamics (CFD) program and is named under the title 3DHVAC; a non-uniform grid of size of minimum of 80 X 60 X 44 was selected. Grid nodes were densely located in the vicinity of the heat source. The primary objective of the present work is to assess the airflow characteristics and Heat transfer in large airconditioned configurations with large heat source; reasonably good agreement between measured and predicted air velocities and temperatures were reported. The paper ends with a brief discussion and conclusion.