Experimental Study Of Cold Inflow And
Its Effect On Draft Of A Chimney
Author(s)
C. Chi-Ming Chu, R. Kwok-How Chu & M. M. Rahman
Abstract
This paper aims to study the cold air inflow into a natural draft air cooled heat
exchanger chimney. In total, seven configurations of experiments were carried
out in the prototype natural draft air-cooled heat exchanger model for two
different supplied heat loads at approximately 0.75 kW to 1.25 kW to determine
the effects of wire mesh screen in the chimney performance. Temperature and
velocity were measured for the configurations and heat loads. It was found that
the Top-only, Top-and-Middle, and Middle-only installations were able to
maintain draft velocities to within 3.0 % of the control experiment draft velocity,
in spite of the resistance of the mesh. It was also found that configurations
utilising mesh at the bottom had experienced a drop in draft velocity by up to
50% from the Control. The smoke flow visualisation tests clearly proved that
cold air inflow phenomenon exist, and can be countered with the installation of
wire mesh at the top of the model.
Keywords: cold inflow, natural draft, heat exchanger, smoke visualisation, wire
mesh.
1 Introduction
In the natural draft air cooled heat exchanger (NDACHX) or cooling tower, the
hot air continuously flows in the upward direction and the cold air enters from
bottom. The airflow is due solely to local buoyancy differences caused by the
presence of temperature difference between process side and ambient. However,
in the forced convection process, a fan is placed either at the bottom or above the
tube bundle to increase airflow rate to remove waste heat. In certain appliances,
natural draft air cooled heat exchanger has the advantage in terms of operational
Keywords
cold inflow, natural draft, heat exchanger, smoke visualisation, wiremesh.
Related Book
Other papers in this volume
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