CFD-Based Calibration of Representative Elementary Units for Dry Pressure Drop in Structured Packings

Öz

Representative Elementary Unit (REU) simplification has become a standard approach for CFD modeling of structured packings; however, its reliability in predicting dry pressure drop remains a critical yet underexplored issue. In particular, the sensitivity of hydraulic performance to internal geometric parameters is often overlooked in the current literature. This study addresses this gap by calibrating an REU model for Mellapak 500.Y against the semi-empirical correlation of Stichlmair et al. (1989) and experimental data from Tsai (2010). Single-phase simulations were conducted using the SST 𝑘−𝜔 turbulence model over a gas-load range of 0.72–4.32 Pa0.5. Grid independence was established at 0.53 million cells per REU. A domain-sensitivity analysis using one, four, and six REUs yielded deviations below 10%, confirming that a single-unit domain provides sufficient accuracy for dry-flow calibration. The results show that the nominal 2.00 mm sheet spacing leads to substantial underprediction of pressure drop, whereas an effective spacing of 0.24 mm brings the CFD predictions into agreement with Tsai’s measurements within a ±20% error band and consistent with the Stichlmair correlation across the operating window. These findings identify the effective sheet spacing as the dominant geometric calibration parameter and provide a reproducible, computationally efficient baseline REU for subsequent hydrodynamics simulations in Mellapak 500.Y.

Anahtar Kelimeler

• dry pressure drop
• representative elementary unit
• computational fluid dynamics
• separation process
• structured packing

Yapılandırılmış Dolgularda Kuru Basınç Düşümü için Temsili Eleman Birimlerinin CFD Tabanlı Kalibrasyonu

Öz

Temsili Eleman Birimi (TEB, Representative Elementary Unit - REU) sadeleştirmesi, yapılandırılmış dolguların CFD ile modellenmesinde standart bir yaklaşım hâline gelmiştir; ancak kuru basınç düşüşünü öngörmedeki güvenilirliği hâlen kritik ve yeterince incelenmemiş bir konu olarak kalmaktadır. Özellikle, hidrolik performansın iç geometrik parametrelere olan duyarlılığı mevcut literatürde sıklıkla göz ardı edilmektedir. Bu çalışma, Mellapak 500.Y için geliştirilen bir REU modelinin, Stichlmair ve arkadaşlarının (1989) yarı-ampirik korelasyonu ve Tsai’nin (2010) deneysel verileri ile kalibre edilmesi yoluyla bu boşluğu doldurmayı amaçlamaktadır. Tek fazlı akış simülasyonları, 0.72–4.32 Pa0.5 gaz yükü aralığında SST 𝑘–𝜔 türbülans modeli kullanılarak gerçekleştirilmiştir. Ağ bağımsızlığı, REU başına 0.53 milyon hücrede sağlanmıştır. Bir, dört ve altı REU kullanılarak yapılan alan-duyarlılık analizi, %10’un altında sapmalar vermiş ve tek birimlik bir hesaplama alanının kuru akış kalibrasyonu için yeterli doğruluk sağladığını doğrulamıştır. Elde edilen sonuçlar, nominal 2.00 mm sac aralığının basınç düşüşünün önemli ölçüde düşük tahmin edilmesine yol açtığını; buna karşılık 0.24 mm’lik etkin aralığın, CFD tahminlerini Tsai’nin ölçümleriyle ±%20 hata bandı içinde uyumlu hâle getirdiğini ve tüm işletme aralığında Stichlmair korelasyonu ile tutarlılık sağladığını göstermektedir. Bu bulgular, etkin sac aralığının baskın geometrik kalibrasyon parametresi olduğunu ortaya koymakta ve Mellapak 500.Y için sonraki hidrodinamik simülasyonlarda kullanılabilecek, tekrarlanabilir ve hesaplama açısından verimli bir temel REU modeli sunmaktadır.

Anahtar Kelimeler

• Ayırma prosesi
• yapılsal dolgu
• kuru basınç kaybı
• temsili eleman hücresi
• hesaplamalı akışkanlar dinamiği

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