كليدواژه :
فوم متخلخل , عملكرد حرارتي , حل تحليلي , تعادل حرارتي محلي , شدت عدم تعادل حرارتي محلي
چكيده فارسي :
مطالعه‌ي جريان سيال و انتقال حرارت درون فوم‌هاي متخلخل با استفاده از دو مدل تعادل حرارتي محلي (LTE) و عدم تعادل حرارتي محلي (LTNE) صورت مي‌گيرد. در اين نوشتار با تعريف انحراف ناسلت بين دو مدل LTE و LTNE شرايطي كه در آن اثر LTNE قابل توجه است تعيين شده است. درواقع با استفاده از اين تحليل كاربر مي‌تواند با توجه به خواص هندسيفوم مورد نظر ـ مانند تخلخل، چگالي حفرات و هدايت حرارتي فوم ـ و شرايط عملياتي مانند سرعت و هدايت حرارتي سيال، مدل مناسب براي انتقال حرارت در فوم را انتخاب كند. نتايج نشان مي‌دهد كه اثر LTNE در تخلخل و چگالي حفرات پايين و هدايت حرارتي بالاي فوم (فوم‌هاي فلزي نسبت به سراميكي) و در سرعت‌ها و هدايت حرارتي پايين سيال بيشتر اهميت دارد. همچنين، در ميان پارامترهاي مذكور، اثر «هدايت حرارتي فوم» بر شدت عدم تعادل حرارتي محلي بيشينه است.
چكيده لاتين :
As a kind of compact heat transfer media, open-cell foams offer a combination
of advantages that include high porosity, high surface density, low pressure
drop, and long-term service, making them well suited for advanced heat recovery
applications. The study of fluid flow and heat transfer in porous foams is generally carried out using two models, namely the Local Thermal Equilibrium (LTE) and
the Local Thermal non-Equilibrium (LTNE). The LTE model assumes no temperature difference between the local fluid and solid struts. However, when there is a significant temperature difference between solid and fluid phases,
then the local phases must be treated individually by the LTNE model. The LTNE
model is more difficult to apply because of more information required on the
interfacial heat transfer coefficient, which is usually obtained through
experimental investigations. In this study, by defining Nusselt deviation
obtained by the LTE and LTNE models, operational and geometrical conditions in
which the effect of LTNE model is significant are determined. As a matter of
fact, based on this analysis, one can choose a suitable model for heat transfer
analysis in porous open-cell foams based on the solid foam properties (such as
porosity, pore density, and thermal conductivity of the foam) and the desired
operating conditions (such as fluid velocity, pipe diameter, and thermal conductivity of the fluid). Results show that among the properties of porous
foams, lower pore density and higher thermal conductivity (metallic foams
against the ceramic foams) have the greatest impact on the importance of the
LTNE model. From the viewpoint of flow operating conditions, the lower flow
velocity, smaller pipe diameter, and lower thermal conductivity of the fluid
increase the importance of the LTNE model in heat transfer analysis of porous
foams. Among the parameters mentioned above, thermal conductivity of porous
foam has the greatest impact on the local thermal non-equilibrium intensity.
