03-01-2013, 04:51 PM
An experimental and numerical study of heat transfer off
an inclined surface subject to an impinging airflow
An experimental and numerical study.pdf (Size: 1.59 MB / Downloads: 60)
Abstract
Understanding the heat transfer interaction between an impinging jet and an inclined surface is of paramount
practical significance. In this paper, the heat transfer process is investigated utilizing a three-dimensional finite volume
numerical method and renormalization group (RNG) theory based k–e turbulence model. The issuing incompressible
jet is impinging upon the inside of an inclined surface creating a thermal boundary layer and a fully three-dimensional
vortex structure. Numerical analyses predict a detailed description of fluid flow patterns and heat transfer coefficients.
Experimental investigations are performed on the inner surface for the purpose of obtaining local and average heat
transfer coefficients and further validation of the numerical results. The effect of different turbulence levels in the
numerical solution is also reported. 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Climate control; Inclined surface; Impinging jets; Rectangular slots
Introduction
The flow of an impinging air jet on an inclined surface
addresses a number of practical applications. Industrial
applications include defogging and deicing of a
vehicle’s windshield, vertical/short takeoff and landing
(V/STOL) engineering, film cooling of turbine blades,
electronics cooling, and waste disposal from smokestacks
into the atmosphere. In many of these applications,
the temperature distribution resulting from the jet
attachment to the inclined plane, and the trajectory and
the physical path of the jet are critical design parameters.
In this paper, the specific application of interest is
air issuing from the defroster’s nozzles of a vehicle and
impinging on the glass windshield. Various factors can
be examined for optimizing the flow performance for
defrosting ice on the outside surface or clearing fog on
the inside surface. The nozzle outlet must be capable of
generating an airflow that disperses over the entire inner
surface of the windshield. Extensive testing on vehicle
systems and components would generally meet specific
customer requirements. However, utilizing Computational
Fluid Dynamics (CFD) tools, a designer can
predict the performance of a system and optimize its
objectives cost-effectively by complementing numerical
computation with fewer experiments.
Results and discussion
This section is divided into two parts: the experimental
results, and the numerical predictions.
. Experimental results
An experimental apparatus consisting of the HVAC
module of a car and a windshield was assembled. A
general schematic of the experimental apparatus is
shown in Fig. 2 (color figures for this paper are available
at . Air is forced onto the inclined surface (windshield),
via the blower of the HVAC module, impinges on the
windshield, hugs the large surface of the windshield, and
disperses into the laboratory environment. The main
base of the test stand is intentionally kept open for unrestricted
placement, adjustment, and accessibility of the
HVAC module components. To allow for the possible
adjustment of the windshield’s angle between the windshield
and dashpad, two pillars made of 3.81 cm perforated
angle were affixed to the stand.