Kanat dizilerinde ışınım ve iletimle ısı geçişi

Abstract

Bu çalışmada dikdörtgen kesitli boyuna kanatlarda ısı geçişi ve sıcaklık dağılımının ışınım ve üretimin etkisinde çeşitli fiziksel büyüklüklerle nasıl değiştiği bir takım kabuller yapılarak incelenmiştir. Bölüm 2 de açıklandığı gibi kanat üzerinde alınan diferansiyel bir parçada enerji dengesi yazılarak bir integrodiferansiyel denklem elde edilmiştir. Bu denklem bilgisayarda programlanabilecek hale getirildikten sonra FTN77 programlama dili ile Newton Raphson iterasyon yöntemi esas alınarak bir program yapılmıştır. Bu programdan elde edilen sonuçlarla bu modelde ışınım iletim ve toplam ısı geçişleri hesaplanmıştır. Program sonuçlan grafiksel olarak Bölüm 3 'de gösterilmişti

Physical situations that involve only conduction and radiation are fairly common. Some examples are heat losses through the walls of a vacuum Dewar, heat transfer through "superinsulation" made up of seperated layers of highly reflective material, and heat losses and temperature distributions in satellite and spacecraft structures. This study theoretically investigates the radiative and conduction heat transfer characteristics of the fin array shown in Fig.l to achive the following primary objectives : (1) tiie evaluation of the total heat transfer from the fin ensemble (2) the evaluation of the local fin temperature and (3) the influence of the important parameters on the thermal performance of the fin array. An infinite array of thin fins of thickness b, width W and infinite length are attached black bases that is held at a constant temperatures Tbl and Tb2 as pictured in Fig.l. The fin surface radiates in a difluse gray manner and the fins are in vacuum. Set up the equation necessary for describing the local fin temperature. Because the fins are thin, it will be assumed that the local temperature of the fin is constant across the thickness b. An energy balance will now be derived for the circled differential element of one fin shown in the inset of Fig. 1. Hence from symmetry, only half the fin thickness need be considered. Also the problem is simplified because the temperature distribution Tf(f) of the adjacent fin is the same as Tflx). Thus the energy balance need be considered for only one fin. The conduction terms for the energy into and out of the element dx per unit time and per unit length of fin in the z direction are: w 1ı*Ö QvM dx 1iio(x) ete Qc,o(s) l _, d. Fıg 1. Geometry for the determination of local temperatures on parallel fins The radiation terms are formulated by using Poljakfs net radiation method. The incoming radiation to the element originates from the acent fin and from the base surfaces, The irradition The irradition The irradition from the adjacent from the base 1 from the base 2 fin (3) q^i(x)dx = dx j qR,0(OdFto-df + dx^dF^ + dxaT^dF^