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

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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