Experimental validation of lmtd method for microscale heat transfer

Abstract

The single phase fluid flow and heat transfer characteristic has been investigated experimentally.Experiments were conducted to cover transition zone for the Reynolds numbers ranging from 100 to 4800 by fused silica and stainless steel microtubes having diameters of 103-180 µm.The applicability of the Logarithmic Mean Temperature Difference (LMTD) method was revealed and an experimental method was developed to calculate the heat transfer coefficient.Moreover the scaling effects in micro scale such as axialtion, viscous heating and entrance effects were discussed.The heat transfer coefficients were compared with data obtained by the correlations available in the literature in the study.The Nusselters of microtube flows dot not accordial with the convention the convention lower thants was discussed discussed.The heat transfer coefficients was compared with the data obtained by the correlations available in the literature in the study.The numy.The Nusselt dot flows dot accord with the convention with the convention the convention the convention thants thantions that lower that 1000 that that that that the convention with the prediction with the prediction with the prediction with the prediction with the prediction with the prediction with the prediction with the prediction with the prediction the prediction that that that that that that that that that that that that that that that that that that that that that that the the the the the the the the that that that 1000 that that that of the whough of the whous that that thoughtion that that that that that the the the the the that that though that that that that that that that that tThe single phase fluid flow and heat transfer characteristic has been investigated experimentally.Experiments were conducted to cover transition zone for the Reynolds numbers ranging from 100 to 4800 by fused silica and stainless steel microtubes having diameters of 103-180 µm.The applicability of the Logarithmic Mean Temperature Difference (LMTD) method was revealed and an experimental method was developed to calculate the heat transfer coefficient.Moreover the scaling effects in micro scale such as axial conduction, viscous heating and entrance effects were discussed.The heat transfer coefficients were compared with data obtained by the correlations available in the literature in the study.The Nusselt numbers of microtube flows do not accord with the conventional results when the Reynolds number was lower than 1000.After that, the Nusselt number approaches the conventional theory prediction.On the aspect of fluid characteristics, the friction factor was well predicted with conventional theory and the conventional friction prediction was valid for water flow through microtube with a relative surface roughness less than about 4 %.The single phase fluid flow and heat transfer characteristic has been investigated experimentally.Experiments were conducted to cover transition zone for the Reynolds numbers ranging from 100 to 4800 by fused silica and stainless steel microtubes having diameters of 103-180 µm.The applicability of the Logarithmic Mean Temperature Difference (LMTD) method was revealed and an experimental method was developed to calculate the heat transfer coefficient.Moreover the scaling effects in microscale such as axial conduction, viscous heating and entrance effects were discussed.The heat transfer coefficients were compared with data obtained by the correlations available in the literature in the study.The Nusselt numbers of microtube flows do not agree with the conventional results when the Reynolds number was lower than 1000.After that, the Nusselt number approaches the conventional theory prediction.On the aspect of fluid characteristics, the friction factor was well predicted with conventional theory and the conventional friction prediction was valid for water flow through microtube with a relative surface roughness less than about 4%.The single phase fluid flow and heat transfer characteristic has been investigated experimentally.Experiments were conducted to cover transition zone for the Reynolds numbers ranging from 100 to 4800 by fused silica and stainless steel microtubes having diameters of 103-180 µm.The applicability of the Logarithmic Mean Temperature Difference (LMTD) method was revealed and an experimental method was developed to calculate the heat transfer coefficient.Moreover the scaling effects in micro scale such as axial conduction, viscous heating and entrance effects were discussed.The heat transfer coefficients were compared with data obtained by the correlations available in the literature in the study.The Nusselt numbers of microtube flows do accord with the convention results when the Reynolds number was lower than 1000.After that, the Nusselt number approdiction the convention prediction. the fluidOntics of the factor factor factor of the predical convention of the conventional through through through through through through through through through through through through through through through.تم التحقيق في خاصية تدفق السوائل ونقل الحرارة أحادية الطور تجريبيًا. تم إجراء تجارب لتغطية المنطقة الانتقالية لأرقام رينولدز التي تتراوح من 100 إلى 4800 بواسطة الأنابيب الدقيقة المصنوعة من السيليكا المنصهرة والفولاذ المقاوم للصدأ التي يبلغ قطرها 103-180 ميكرومتر. تم الكشف عن قابلية تطبيق طريقة فرق متوسط درجة الحرارة اللوغاريتمي (LMTD) وتم تطوير طريقة تجريبية لحساب معامل نقل الحرارة. علاوة على ذلك، فإن تأثيرات التحجيم في المقياس الدقيق مثل التوصيل المحوري والتدفئة اللزجة وتأثيرات المدخل تمت مناقشتها. تمت مقارنة معاملات نقل الحرارة بالبيانات التي تم الحصول عليها من خلال الارتباطات المتاحة في الأدبيات في الدراسة. لا تتفق أرقام نوسيلت لتدفقات الأنابيب الدقيقة مع النتائج التقليدية عندما كان رقم رينولدز أقل من 1000. بعد ذلك، يقترب رقم نوسيلت من التنبؤ النظري التقليدي. على جانب خصائص السوائل، تم التنبؤ بعامل الاحتكاك بشكل جيد مع النظرية التقليدية وكان التنبؤ التقليدي صالحًا لتدفق المياه الدقيقة من خلال أنبوب دقيق مع خشونة نسبية أقل من 4 ٪ تقريبًا.