A streamlined strut supporting a bearing housingis exposed

Chapter 6, Problem 6.66

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A streamlined strut supporting a bearing housingis exposed to a hot airflow from an engine exhaust. It isnecessary to run experiments to determine the averageconvection heat transfer coefficient from the air to thestrut in order to be able to cool the strut to the desiredsurface temperature Ts. It is decided to run mass trans-fer experiments on an object of the same shape and toobtain the desired heat transfer results by using the heatand mass transfer analogy. The mass transfer experiments were conducted using ahalf-size model strut constructed from naphthaleneexposed to an airstream at 27C. Mass transfer mea-surements yielded these results:ReLShL60,000 282120,000 491144,000 568288,000 989(a) Using the mass transfer experimental results, deter- mine the coefficients Cand mfor a correlation ofthe form .(b) Determine the average convection heat transfer coef-ficient for the full-sized strut, LH?60 mm, whenexposed to a free stream airflow with V?60 m/s,T??184C, and p??1 atm when Ts?70C.(c) The surface area of the strut can be expressed asAs?2.2LH?l, where lis the length normal to the page.For the conditions of part (b), what is the change inthe rate of heat transfer to the strut if the characteristiclength LHis doubled?