Klima santrallerinde kullanılan delikli difüzörlü boş hücredeki hava akışının akış ve akustik açıdan incelenmesi
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Tarih
2019-10-30
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İnönü Üniversitesi
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info:eu-repo/semantics/embargoedAccess
Özet
Klima santrallerinde kullanılan fanların hava çıkış ağızlarının kesit alanı fandan sonra gelen ısıtıcı/soğutucu serpantin, nemlendirici, filtre ve susturucu gibi ünitelerin kesit alanından küçüktür. Klima santrallerinin enerji verimliliği açısından etkin çalışabilmesi için küçük kesit alanından çıkan havanın diğer ünitelerin bulunduğu büyük kesit alanına kısa mesafede yayılması gerekir. Bu yayılmanın sağlanması için fan hücresinden sonra delikli difüzörlü hücreler kullanılır. Bu delikli difüzörlerin havayı olabildiğince üniform ve en az basınç kaybı ile yaymasının yanında aeroakustik açıdan oluşturduğu gürültü de önem arz etmektedir.
Bu çalışmada, kare kesik piramit delikli difüzörlü hücredeki hava akış karakteristiği ve akış kaynaklı gürültü incelenmiştir. Kare kesik piramit delikli difüzörlü hücrenin geometrik tasarım parametrelerinin basınç kaybı, hava hızı dağılımı ve ses basınç seviyesi üzerindeki etkileri ortaya konmuştur. Geometrik tasarım parametresi olarak porozite, difüzörün et kalınlığı, koniklik açısı, difüzör mesafesi, delik geometrisi, delik hidrolik çapı, delik yerleşim türü ve difüzör yüzey türü gibi parametreler belirlenmiştir.
Akış analizleri için bir deney düzeneği kurulmuştur. İki farklı geometriye sahip delikli difüzör için deneyler yapılmış, sayısal modelin ağ yapısı ve türbülans modeli geçerli kılınmıştır. Geometrik tasarım parametrelerinin basınç kaybına, hız dağılımına ve aeroakustik performansa etkileri sayısal olarak incelenmiştir. Yapılan çalışmada katı modeller SolidWorks programında oluşturulmuştur. Akış ve aeroakustik analizler ANSYS Fluent paket programında gerçekleştirilmiştir. Sayısal akış analizleri için sıkıştırılamaz, daimi akış koşulları kabulü yapılmıştır. Çözümlerde standart k-ε türbülans modeli kullanılmıştır. Sayısal aeroakustik analizlerde ise ANSYS-Fluent programında zamana bağlı çözümler gerçekleştirilmiş ve program bünyesinde bulunan Ffowcs Williams ve Hawkings (FW-H) yönteminin modülü kullanılmıştır. Delikli difüzörlü hücre içine yerleştirilen üç farklı konumdaki mikrofondan alınan zamana bağlı sinyaller Hızlı Fourier Dönüştürme (FFT) yöntemiyle 0-1000 Hz frekans aralığına dönüştürülmüş ve ses basınç seviyesi (SPL) değerleri elde edilmiştir.
Outlet cross-sectional area of fans used in air handling units (AHUs) is smaller than cross-sectional area of chambers which are located next to the fan of HVAC equipment such as heating/cooling coils, silencer (sound attenuator), filter or heat recovery elements. In order to operating of air handling units (AHUs) in terms of energy efficiency, it is required that air blown by the fan diffuses from small cross-sectional area to large cross-section area as short as possible distance. To provide the diffusion, perforated diffuser are used after the fan cell. In addition to these diffusers diffuse the air as uniformly as and with minimal pressure loss, aerodynamically generated noise caused by perforated diffusers is also important. In this study, airflow characteristic and noise induced airflow were investigated in chamber with truncated pyramid perforated diffuser. The effects of geometrical design parameters of truncated pyramid perforated diffusers on pressure loss, airflow diffusion performance of diffuser and sound pressure level in the chamber were found out. As geometrical design parameters, porosity, thickness, draft angle, distance of diffuser, hole geometry type, hole hydrualic diameter, hole array type and diffuser surface type were determined. An experimental setup for flow analysis was established. Experimental studies were carried out for two different perforated diffusers, the mesh structure and turbulence model of the numerical model are validated. The effects of geometrical design parameters on pressure loss, velocity distribution and aeroacoustic performance were investigated numerically. Solid models were created in SolidWorks. Flow and aeroacoustic analyzes were performed in ANSYS Fluent package program. Incompressible, steady state flow conditions are supposed for numerical flow analyzes. In the numerical solutions, standard k-ε turbulence model was used. In the numerical aeroacoustic analyzes, transient flow condition were carried out in the ANSYS-Fluent program and the module of the Ffowcs Williams and Hawkings (FW-H) method build in the program was used. The time-dependent signals from the microphones in three different locations placed in a perforated diffuser cell were converted to a frequency range of 0-1000 Hz by Fast Fourier Transform (FFT) method and sound pressure level (SPL) values were obtained.
Outlet cross-sectional area of fans used in air handling units (AHUs) is smaller than cross-sectional area of chambers which are located next to the fan of HVAC equipment such as heating/cooling coils, silencer (sound attenuator), filter or heat recovery elements. In order to operating of air handling units (AHUs) in terms of energy efficiency, it is required that air blown by the fan diffuses from small cross-sectional area to large cross-section area as short as possible distance. To provide the diffusion, perforated diffuser are used after the fan cell. In addition to these diffusers diffuse the air as uniformly as and with minimal pressure loss, aerodynamically generated noise caused by perforated diffusers is also important. In this study, airflow characteristic and noise induced airflow were investigated in chamber with truncated pyramid perforated diffuser. The effects of geometrical design parameters of truncated pyramid perforated diffusers on pressure loss, airflow diffusion performance of diffuser and sound pressure level in the chamber were found out. As geometrical design parameters, porosity, thickness, draft angle, distance of diffuser, hole geometry type, hole hydrualic diameter, hole array type and diffuser surface type were determined. An experimental setup for flow analysis was established. Experimental studies were carried out for two different perforated diffusers, the mesh structure and turbulence model of the numerical model are validated. The effects of geometrical design parameters on pressure loss, velocity distribution and aeroacoustic performance were investigated numerically. Solid models were created in SolidWorks. Flow and aeroacoustic analyzes were performed in ANSYS Fluent package program. Incompressible, steady state flow conditions are supposed for numerical flow analyzes. In the numerical solutions, standard k-ε turbulence model was used. In the numerical aeroacoustic analyzes, transient flow condition were carried out in the ANSYS-Fluent program and the module of the Ffowcs Williams and Hawkings (FW-H) method build in the program was used. The time-dependent signals from the microphones in three different locations placed in a perforated diffuser cell were converted to a frequency range of 0-1000 Hz by Fast Fourier Transform (FFT) method and sound pressure level (SPL) values were obtained.
Açıklama
Anahtar Kelimeler
Klima santrali, Delikli difüzör, Hesaplamalı akışkanlar dinamiği, Basınç kaybı, Hız dağılımı, aeroakustik, Fan
