KANATÇIK UÇ VE TABAN NOKTALARI ARASINDAKİ FARKLI BOŞLUK ORANLARI İÇİN KANATÇIK DİZİLERİNDEN DOĞAL TAŞINIM İLE ISI TRANSFERİNİN DENEYSEL ARAŞTIRILMASI

Kanatçık dizilerinden doğal taşınım ile ısı transferi kanatçık yüksekliği ve kanatçık uç ve taban noktaları arasındaki farklı boşluk oranları için geniş bir Rayleigh sayısı aralığında deneysel olarak araştırılmıştır. Taban kanatçıklar arası mesafe, kanatçık yüksekliği ve kanatçık kalınlığı sırasıyla 12, 100 ve 3 mm olarak sabit tutulmuştur. Kanatçık uç ve taban noktaları arasındaki boşluk oranı 0.25-1 aralığında ve kanat yüksekliği de 15-40 mm arasında değiştirilmiştir. Kanatçık dizisi ve çevre ortam arasındaki verilen bir sıcaklık farkı için kanatçık dizilerinden olan ısı transferinin, kanatçıkların uç ve taban noktaları arasındaki boşluk oranının ve kanatçık yüksekliğinin bir fonksiyonu olarak maksimum bir değer aldığı bulunmuştur. Deneysel çalışmadan elde edilen sonuçlar, maksimum ısı transferini veren kanatçıkların uç ve taban noktaları arasındaki optimum boşluk oranının C=0.50 ile C=0.75 arasında olduğunu göstermiştir. Maksimum ısı transferini sağlayan bu optimum oran özellikle kanatçık yüksekliğine ve Rayleigh sayısına bağlıdır. Dikdörtgen kesitli kanatçık dizileri ile karşılaştırıldığında optimum orana sahip kanatçık dizilerinden daha yüksek Nusselt sayıları elde edilmiştir. Nusselt sayısındaki bu artışın 33%'e kadar olduğu belirlenmiştir. Yapılan bu çalışma sonucunda Nusselt sayısı için bir ampirik bağıntı türetilmiştir

EXPERIMENTAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM FIN ARRAYS FOR DIFFERENT TIP-TO-BASE FIN SPACING RATIOS

Natural convection heat transfer from fin arrays was investigated experimentally at a wide range of Rayleigh numbers for fin height and different tip-to-base fin spacing ratios (C=St/Sb) . Base fin spacing, fin length and fin thickness were kept fixed at 12, 100 and 3 mm respectively. The ratio C was varied from 0.25 to 1 and fin height was also varied from 15 to 40 mm. It was found that the convection heat transfer rate from fin array takes on a maximum value as a function of the C and fin height for a given temperature difference between fin arrays and surrounding. The results obtained from experimental study showed that the optimum C which yields the maximum heat transfer rate is between C=0.50 and C=0.75. The optimum ratio also depends strongly on the fin height and Rayleigh number. It was observed that fin arrays with an optimum ratio gave higher Nusselt numbers compared to rectangular shaped fin arrays. The increase in the Nusselt number was determined to be about 33%. An empirical correlation for the Nusselt number was derived in the result of experimental study

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Arquis E. and Rady M., 2005, Study of natural convection heat transfer in a finned horizontal fluid layer, International Journal of Thermal Sciences, 44, 43-52.
Baskaya S., Sivrioglu M. and Ozek M., 2000, Parametric study of natural convection heat transfer from horizontal rectangular fin arrays, International Journal of Thermal Sciences, 39, 797-805.
Chen H.T. and Hsu W.L., 2007, Estimation of heat transfer coefficient on the fin of annular-finned tube heat exchangers in natural convection for various fin spacings, International Journal of Heat and Mass Transfer, 50, 1750-1761.
Dharma R. V., Naidu S.V., Govinda R.B. and Sharma K.V., 2006, Heat transfer from a horizontal fin array by natural convection and radiation-A conjugate analysis, International Journal of Heat and Mass Transfer, 49, 3379-3391.
Doğan A., Akkus S. and Baskaya Ş., 2012, Numerical Analysis of Natural Convection Heat Transfer From Annular Fıns on a Horizontal Cylinder, Journal of Thermal Science and Technology, 32, 31-41.
Elenbaas W., 1942, Heat dissipation of parallel plates by free convection, Physica, 9, 1-28.
Fabbri G., 1999, Optimum performances of longitudinal convective fins with symmetrical and asymmetrical profiles, International Journal of Heat and Fluid Flow, 20, 634-64.
Harahap F. and McManus H.N., 1967 Natural Convection Heat Transfer From Horizontal Rectangular Fin Arrays, Journal of Heat Transfer, 89 32-38.
Huang R.T., Sheu W.J. and Wang C.C., 2008, Orientation effect on natural convective performance of square pin fin heat sinks, International Journal of Heat and Mass Transfer, 51, 2368-2376.
Incropera F.P., 1988, Convection Heat Transfer in Electronic Equipment Cooling, Journal of Heat Transfer, 110, 1097-1111.
Jones C.D. and Smith L.F., 1970, Optimum Arrangement of Rectangular Fins on Horizontal Surfaces for Free-Convection Heat Transfer, Journal of Heat Transfer, 92, 6-10.
Khor Y.K., Hung Y.M. and Lim B.K., 2010, On the role of radiation view factor in thermal performance of straight-fin heat sinks, International Communications in Heat and Mass Transfer, 37, 1087-1095.
Kim D.K., 2012, Thermal optimization of plate heat sinks with fins of variables thickness under natural convection, International Journal of Heat and Mass Transfer, 55, 752-761.
Kobus C.J. and Oshio, T., 2005a, Development of a theoretical model for predicting the thermal performance characteristics of a vertical pin-fin array heat sink under combined forced and natural convection with impinging flow, International Journal of Heat and Mass Transfer, 48, 1053-1063.
Kobus C.J. and Oshio, T., 2005b, Predicting the thermal performance characteristics of staggered vertical pin fin array heat sinks under combined mode radiation and mixed convection with impinging flow, International Journal of Heat and Mass Transfer, 48, 2684-2696.
Kundu B. and Das, P.K., 2009, Performance and optimum design analysis of convective fin arrays attached to flat and curved primary surfaces, International Journal of Refrigeration, 32, 430-443.
Leung C.W., Probert S.D. and Shilston M.J., 1985, Heat exchanger design: Thermal performances of rectangular fins protruding from a vertical or horizontal rectangular bases, Applied Energy, 20, 123-140.
Leung C.W. and Probert, S.D., 1989 Thermal effectiveness of short-protrusion rectangular, heatexchanger fins, Applied Energy, 34, 1-8.
Mobedi M. and Yüncü H., 2003, A three dimensional numerical study on natural convection heat transfer from short horizontal rectangular fin array, Heat and Mass Transfer, 39, 267-275.
Moffat R.J., 1982, Contributions to the Theory of Single-Sample Uncertainty Analysis, Journal of Fluids Engineering, 104, 250-258.
Moffat R.J., 1985, Using Uncertainty Analysis in the Planning of an Experiment, Journal of Fluids Engineering, 107, 173-178.
N. Ellison Gordon., 1979, Generalized Computations of the Gray Body Shape Factor for Thermal Radiation from a Rectangular U-Channel, IEEE Transactions on Components Hybrids and Manufacturing Technology, 2, 517-522.
Nada S.A., 2007, Natural convection heat transfer in horizontal and vertical closed narrow enclosures with heated rectangular finned base plate, International Journal of Heat and Mass Transfer, 50, 667-679.
Naik S., Probert S.D. and Wood C.I., 1987, NaturalConvection Characteristics of a Horizontally-Based Vertical Rectangular Fin-Array in the Presence of a shroud, Applied Energy, 28, 295-319.
Rammohan R.V. and Venkateshan S.P., 1996, Experimental study of free convection and radiation in horizontal fin arrays, International Journal of Heat and Mass Transfer, 39, 779-789.
Sparrow E.M. and Vemuri S.B., 1985, Natural Convection/Radiation Heat Transfer From Highly Populated Pin Fin Arrays, Journal of Heat Transfer, 107, 190-197.
Sparrow E.M. and Vemuri, S.B., 1986, Orientation effects on natural convection/radiation heat transfer from pin-fin arrays, International Journal of Heat and Mass Transfer, 29, 359-368.
Starner K.E. and McManus H.N., 1963, An Experimental Investigation of Free-Convection Heat Transfer From Rectangular-Fin-Arrays, Journal of Heat Transfer, 85, 273-277.
Tari I. and Mehrtash M., 2013, Natural convection heat transfer from inclined plate-fin heat sinks, International Journal of Heat and Mass Transfer, 56, 574-593.
Turkyilmazoglu M., 2015, Nonlinear Heat Transfer In Rectangular Fins And Exact Solutions With Temperature Dependent Properties, Journal of Thermal Science and Technology, 35, 29-35.
Welling J.R. and Wooldridge C.B., 1965, Free Convection Heat Transfer Coefficients From Rectangular Vertical Fins, Journal of Heat Transfer, 87, 439-444.
Wong S.C. and Huang G.J., 2013, Parametric study on the dynamic behavior of natural convection from horizontal rectangular fin arrays, International Journal of Heat and Mass Transfer, 60, 334-342.
Yalcin H.G., Baskaya S. and Sivrioglu M., 2008, Numerical analysis of natural convection heat transfer from rectangular shrouded fin arrays on a horizontal surface, International Communications in Heat and Mass Transfer, 35, 299-311.
Yazıcıoğlu B. and Yüncü H., 2009, A Correlation For Optimum Fin Spacing of Vertically-Based Rectangular Fin Arrays Subjected to Natural Convection Heat transfer, Journal of Thermal Science and Technology, 29, 99-105.
Yüncü H. and Anbar G., 1998, An experimental investigation on performance of rectangular fins on a horizontal base in free convection heat transfer, Heat and Mass Transfer, 33, 507-514.