STUDY ON IMPINGEMENT HEAT TRANSFER CONTROL WITH NON-CIRCULAR DUAL JETS USING REAL TIME AND SPATIAL TEMPERATURE MEASUREMENTS

在许多快速加热和冷却系统中，冲击射流被用来增强传热，因为在冲击射流的停滞区获得了较高的传热系数。多射流，特别是非圆形多射流，通常用于实际的换热装置，但单射流的数据不能直接应用于多射流的情况，因为多射流的流型反映了射流之间以及射流与废流之间的相互作用。为了获得一种相互作用现象对局部换热分布影响的基本信息，将两束空气射流撞击靶板。实验研究了非圆形椭圆喷嘴结构的双射流撞击靶板时，喷嘴间距对靶板传热特性的影响。为了测量平板上的时间和空间热分布，在实验中采用了一种带有二维铟锑（In Sb）传感器阵列的红外辐射计。然后根据测得的温度分布得到换热系数。此外，利用热电偶测量的其他温度分布得到了传热系数。用油-钛（iv）氧化物法对表面的流动模式进行了可视化。为了阐明发展过程中的行为，还测量了喷管出口下游的速度和湍流强度。结果表明：1)小间距s / l （s：喷嘴间距，l：椭圆喷嘴小轴宽）=1.67等温线；在小的喷嘴-板分离中，由于经过射流之间区域的花流非常强，流型呈十字形分布。2)在s / l =3.33时，由于单个射流条件的改变会立即影响到流动，因此小的喷嘴-板分离的流动行为变得不稳定。3)单椭圆射流的开关现象发生在较短的分离时间内。对于椭圆喷嘴的双射流，这种现象首先发生在较低的气流区域，即射流的外缘，随后也发生在中心部分。4)红外图像的等温线是了解流动和传热的时间和空间特征的有用方法。少

THE IMPINGEMENT JET HAS BEEN UTILIZED FOR ENHANCING THE HEAT TRANSFER IN MANY RAPID HEATING AND COOLING SYSTEMS BECAUSE THE RELATIVELY HIGH HEAT TRANSFER COEFFICIENTS ARE OBTAINED AT THE STAGNATION REGION OF THE IMPINGING JET.MULTIPLE JET,ESPECIALLY NON-CIRCULAR MULTIPLE JETS,ARE USUALLY USED FOR PRACTICAL HEAT TRANSFER DEVICES,BUT,THE DATA OF SINGLE JET CANNOT BE DIRECTLY APPLIED TO THE CASE OF MULTIPLE JETS BECAUSE THE FLOW PATTERN THEN REFLECTS THE INTERACTION AMONG JETS AND BETWEEN JET AND SPENT FLOW.IN ORDER TO OBTAIN THE BASIC INFORMATION ON EFFECTS OF AN INTERACTION PHENOMENA ON THE LOCAL HEAT TRANSFER DISTRIBUTIONS,TWO AIR JETS WERE IMPINGED TO THE TARGET PLATE.THE EFFECT OF NOZZLE-TO-NOZZLE SPACINGS ON THE HEAT TRNASFER CHARACTERISTICS OVER THE TARGET PLATE WERE EXPERIMENTALLY INVESTIGATED WHEN THE DUAL JETS ISSUING FROM THE NON-CIRCULAR ELLIPTIC NOZZLE CONFIGURATION STRUCK THE TARGET PLATE.TO MEASURE THE TIME AND SPATIAL THERMAL DISTRIBUTIONS OVER THE PLATE,AN INFRARED RADIOM … More ETER WITH A TWO-DIMENSIONAL ARRAY OF INDIUM-ANTIMONY (In Sb) SENSORS WAS EMPLOYED IN PRESENT EXPERIMENTS.THEN THE HEAT TRANSFER COEFFICIENTS WERE OBTAINED BY THE MEASURED TEMPERATURE PROFILE.MOREOVER,THE HEAT TRANSFER COEFFICIENTS WERE OBTAINED BY USING OTHER TEMPERATURE PROFILES MEASURED WITH THERMOCOUPLES.THE FLOW PATTERNS OF THE SURFACE WERE ALSO VISUALIZED BY THE OIL-TITANIUM (IV) OXIDE METHOD.TO CLARIFY THE BEHAVIORS IN DEVELOPING PROCESSES,THE VELOSITY AND TURBULENCE INTENSITY WERE ALSO MEASURED DOWNSTREAM FROM THE NOZZLE EXIT.THE MAIN RESULTS ARE :1) AT THE SMALL SPACINGS S/L (S : NOZZLE-TO-NOZZLE SPACING,L : MINOR AXIS WIDTH OF ELLIPTIC NOZZLE)=1.67 ISOTHERMS ; I.E.HEAT TRANSFER COEFFICIENTS CONTOURS,AND FLOW PATTERNS SHOW THE CROSS-SHAPED PATTERN FOR A SMALL NOZZLE-TO-PLATE SEPARATIONS BECAUSE THE SPENT FLOW THROUGH THE REGION BETWEEN JETS ARE SIGNIFICANTLY STRONG.2) AT S/L=3.33, THE FLOW BEHAVIOR FOR SMALL SEPARATIONS BECOMES UNSTEADY BECXAUSE THE FLOW ARE IMMEDIATELY AFFECTED BY THE CHANGE OF CONDITION OF A ONE JET..3) THE SWITCHING PHENOMENA OCCURRED AT A MORE SHORT SEPARATION FOR THE SINGLE ELLIPTIC JET.FOR DUAL JETS WITH ELLIPTIC NOZZLE,THE PHENOMENA OCCURRED AT A MORE DOWNSTEARM REGION,AT THE OUTER EDGES OF JETS AT FIRST,WHEREAFTER IT ALSO OCCURRED IN THE CENTRAL PARTS.4) THE ISOTHEMS OF INFRARED IMAGES ARE A USEFUL WAY TO AN UNDERSTANDING THE TIME AND SPATIAL CHARACTERISTICS OF FLOW AND HEAT TRANSFER. Less