مطالعه ي عددي پارامتر هاي تأثير گذار بر عملكرد حرارتي و ديناميكي كوره ي حرارتي پرس گرم

Numerical investigation of affecting parameters on the thermal and dynamic performance of a hot isostatic pressing furnace

پرس ايزواستاتيك گرم يا هيپ يكي از فرايندهاي مورد استفاده در متالورژي پودر است. به دليل هزينه‌ي بسيار بالاي ساخت نمونه آزمايشگاهي اين نوع از كوره، استفاده از شبيه‌سازي عددي به منظور مطالعه‌ي رفتار آن بسيار حائز اهميت است. در اين پژوهش، عملكرد هندسه‌ي خاصي از يك كوره‌ي حرارتي پرس گرم به‌صورت عددي مطالعه شده است. به منظور افزايش دقت حل مسئله از مدل ترموديناميكي گاز واقعي استفاده شده و معادلات پيوستگي، مومنتوم، آشفتگي و انرژي به‌صورت هم‌زمان حل شده است. در اين پژوهش ضمن مطالعه‌ي رفتار كوره بر اساس شرايط مرزي و اوليه پيش‌فرض، تأثير فراسنجه‌هاي مختلف بر رفتار كوره‌ي حرارتي پرس گرم مثل تغيير نوع گاز، دماي ديواره‌ي آبگرد، وجود يا عدم وجود سپر حرارتي، شرايط مرزي المنت و نيز فشار اوليه بررسي شده است. نتايج به دست آمده نشان مي‌دهد كه فشار اوليه‌ي گاز داخل كوره و نيز دماي مرز آبگرد تأثير قابل توجهي بر ميزان فشار نهايي گاز كوره دارند. همچنين مطالعه‌ي تغييرات گذراي دماي ناحيه گرم در دو حالت خاموش شدن المنت مي‌تواند مبنايي براي طراحي و ساخت يك سيستم كنترل دماي مناسب براي كوره باشد.

Hot isostatic pressing (HIP) is a manufacturing process used in powder metallurgy science. It can be used to consolidate a powder, enhance the properties of a single crystal, solidify a cast blade in a specified direction and generally, densify a cold pressed, sintered or a cast part. The numerical simulation of the thermofluidic responses of working gases can provide important and detailed information about the dynamics of fluid flow and heat transfer in a HIP furnace. This information cannot be obtained from experimental observations. The experimental investigation of such a high temperature and pressure process is quite expensive. Moreover, the high working pressure and temperature limits the application of probes and sensors that may enable detailed data collection. This paper presents the modeling procedure and the results of a numerical investigation of a HIP furnace. The effects of the heater temperature, the performance of the cooling water system, and the presence of a radiation shield in front of the element were studied for two working gases. Moreover, investigation of the element heat flux and the temperature variation of the furnace could be used to choose a proper element and design an accurate control system. In order to increase the accuracy of the results, a real gas thermodynamic model has been also employed. In terms of physical modeling, the momentum and continuity equations and a two-equation turbulence model were coupled with the energy equation and radiation correlations. The results indicate that the final furnace pressure is directly influenced by the performance of the cooling system and the initial furnace pressure. A linear relation between the final and initial furnace pressure is observed. In addition, the final pressure is dependent on the type of the working gas whereas the temperature distribution is not significantly varied by gas selection. Based on the results, existence of the radiation shield causes non-uniformity in the flow field and temperature distribution of the hot zone area. The thermal conductivity of the furnace wall has a significant effect on the furnace heat loss. As the thermal conductivity increases tenfold, heat loss increases by 700 percent.