طراحي آزمايش معكوس براي تخمين ضريب انتقال حرارت جابه‌جايي جت برخوردي شياري

Inverse Experiment Design for Estimation of Local Convective Heat Transfer Coefficient Impinging Slot Jet

در اين مقاله ضريب انتقال حرارت جابه‌جايي محلي در جت برخوردي شياري با استفاده از دماهاي اندازه‌گيري شده در صفحه‌ي برخورد و روش انتقال حرارت هدايتي معكوس تخمين زده شده است. روش معكوس استفاده شده در اين مقاله روش دنباله‌يي تخمين متوالي توابع بك است. در اين مطالعه تاثير پارامترهاي مهمي مانند گام زماني، پارامتر تنظيم، مقدار شار حرارتي توليدي هيتر، ضخامت صفحه‌ي برخورد، تعداد ترموكوپل‌ها در نتايج بررسي شده است. براي تخمين دقيق‌تر ضريب انتقال حرارت جابه‌جايي يك سري شبيه‌سازي‌هاي عددي انجام شده تا مقدار بهينه‌ي پارامتر‌هاي اثرگذار در اين روش با توجه به خطاي باياس و واريانس و مجذور ميانگين مربع خطا تعيين گردد و آزمايش بهينه طراحي شود. مشاهده مي‌شود كه با استفاده از اين روش با توجه به ساده و ارزان بودن آن، ضريب انتقال حرارت جابه‌جايي با دقت خوب و با خطاي كمي تخمين زده شده است.

Jet impingement is widely used in industry because of the highly favorable heat transfer rate it provides. Engineering applications include the annealing of metal sheets, drying of textile products, deicing of aircraft wings, and cooling of gas turbine blades and electronic components. There are several techniques used in evaluating the local convective heat transfer coefficient. Mass transfer methods have been widely used since many years ago. The heat-mass transfer analogy, in conjunction with the naphthalene sublimation technique, was used to investigate local and average heat transfer coefficients. Thermo chromic liquid crystals have been applied extensively to heat transfer measurements. Using temperature maps obtained from liquid crystals applied to a constant heat ?ux surface, Newton’s Law of Cooling is used to establish distributions of the convective heat transfer coefficient. However, these methods either require expensive or delicate equipment or have limitations to high temperatures or high levels of turbulence in the ?ow. An alternative method that is also particularly suited for the investigation of jet impingement heat transfer, is the inverse heat conduction(IHC) technique. The temperature on the impingement surface is measured. It is advantageous because it can be carried out with simple, low-cost instrumentation and subsequent numerical procedures. In this technique, temperatures measured at some proper interior locations on the impingement surface are used to estimate a thermal boundary condition. The word “estimation” is used here, as temperature measurements always contain noise. Tikhonov’s regularization technique and Beck’s function estimation method are among the most well-known approaches in inverse heat transfer. The purpose of this study is to use the solution of a transient, sequential IHC scheme to estimate the distribution of the steady-state and unsteady convective heat transfer coefficient in a pulsating jet in laminar flow and turbulence flow at different frequencies, and present the optimum simulation. The method is required to be considered two-dimensional because of the lateral conduction that occurs between the warmer and cooler areas of the surface of the target plate. The inverse scheme used is tested using simulated measured temperatures containing Gaussian noise.