Study Of Heat Transfer Characteristics Of An Array Of Impinging Slot Jets

Based on heat transfer characteristics between cooling gas and strip in actual worksituation in continuous annealing furnace, and combined with co-existing references andtest equipments, experimental apparatus and methods are explored, which canaccurately simulate heat transfer between impinging gaseous jets and strip in continuousannealing furnace. Forecasting model of numerical simulation method is built up aswell.This thesis studied the heat transfer characteristics of impinging gaseous slot jetsby experimental and numerical simulation methods. Setting up the experimentalapparatus of heat transfer between impinging gas and strip, taking the comparison of themeasurement results of different current test equipments, we can determine the suitablecurrent test apparatus. The strip is heated by hot oil. The strip’s emissivity which is setup in P30IR ThemoVision to obtain accurate temperature is checked. Analyzing theresults of experiment combine with heat transfer theory, we can test and verify thereliability of the experiment equipment.The impact of strip surface temperature, nozzle structure, jet velocity, nozzleemergence length and impinging distance (H/B) on forced convective heat transfercoefficient can be studied by experimental research. The result shows that the surfacetemperature of strip can influence the heat transfer significantly when there is noimpinging gas, but quite opposite when there is impinging gas. Heat transfer ability ofnozzleⅠis better than nozzleⅡ’s. Heat transfer capacity can be enhanced by increasingjet velocity; nozzle emergence length has some influence to the heat transfer; the bestimpinging distance is H/B=7~8. The impact of impinging distance (H/B) and Reynoldsnumber on convective heat transfer are discussed as well. Under the condition of highReynolds number and short impinging distance, secondary peak of convective heattransfer coefficient appears. All these provide an important principle for nozzles designin continuous annealing furnace.Heat transfer of impinging gaseous slot jets is simulated by computational fluiddynamics software——FLUENT, which finds out that the RNG k-ε model is the mostsuitable turbulent model, and the best calculation time is more than200times. Thesensitivity of various factors on the calculated result is discussed. The result shows thatthe inlet velocity and outlet temperature are sensitive to convective heat transfer, and the incorrect outlet temperature may result in a false heat transfer process, and thisphenomenon should be avoided in the numerical simulation. The physical parameters ofimpinging gas have a significant impact on the numerical result, which should be takenseriously in the numerical simulation. The numerical result being consistent with theexperimental result proves that the numerical heat transfer model is reliable and can beused for numerical calculation of heat transfer of an array of impinging gaseous slot jets.This provides an effective method for heat transfer problem.