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

冲击射流在滞止区具有较高的传热系数，因此在许多快速加热和冷却系统中被用来强化传热。多股射流，特别是非圆形多股射流，通常用于实际的传热装置，但是，单股射流的数据不能直接应用于多股射流的情况，因为多股射流的流态反映的是射流之间以及射流与废流之间的相互作用。实验研究了两股空气射流冲击靶板时，喷嘴间距对靶板上传热特性的影响。为了测量靶板上的时间和空间传热，采用了红外辐射测量技术，测量了两股空气射流冲击靶板时，靶板上的传热特性。实验结果表明，两股空气射流冲击靶板时，靶板上的传热特性随喷嘴间距的增大而增大 ...更多信息 本文采用二维铟锑（InSb）传感器阵列的ETER实验装置，由测量的温度分布得到了ETER的传热系数，并利用热电偶测量的其它温度分布得到了ETER的传热系数。同时，用油-钛（IV）氧化物法观察了ETER表面的流态。为了验证ETER在蒸发过程中的行为，在喷管出口下游测量了流场的流速和湍流强度，主要结果如下：1）在小间距S/L处（S：喷嘴间距，L：椭圆形喷嘴短轴宽度）=1.67等温线;即传热系数等值线，流场显示了小喷管的十字形流场，2）在S/L=3.33时，小分离的流动特性变得不稳定，因为流动直接受到单射流条件变化的影响。3)对于单椭圆射流，射流的湍流现象发生在较短的分离距离内;对于双椭圆喷嘴射流，射流的湍流现象首先发生在射流的较下游区域，即射流的外缘，然后在射流的中部也发生了湍流现象。4）红外辐射等值线是了解流动和换热的时间和空间特性的有效途径。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