Isothermal air jet and premixed flame jet impingement: Heat transfer characterisation and comparison
Isothermal air jet and premixed flame jet impingement: Heat transfer characterisation and comparison
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DOI：
10.1016/j.ijthermalsci.2015.10.018
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发表时间：
2016-02
影响因子：
4.5
通讯作者：
Pramod Kuntikana;S. Prabhu
中科院分区：
文献类型：
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作者：
Pramod Kuntikana;S. Prabhu
射流冲击换热是一种成熟的技术，可在许多冷却和加热应用中获得高的换热速率。冲击换热方法广泛应用于家用电器和工业家电中。撞击等温气体射流既可用于加热，也可用于冷却。然而，预混火焰射流用于加热目标表面。本文对等温风射流和预混火焰射流的换热特性进行了比较。对喷流温度为30℃(冷喷或常温喷流)、100℃(热喷流)和预混甲烷-空气火焰射流(化学计量混合物)、雷诺数分别为500、750、1000、1250和1500、喷嘴或燃烧器间距为2d、4d和6d的等温空气射流进行了换热特性实验研究。薄金属箔技术用于表征等温空气射流。对于固定的射流雷诺数，等温空气射流的努塞尔数与射流与周围流体的温差无关。提出了一种用于表征预混火焰射流的稳态技术。研究结果表明，等温空气射流和预混火焰射流的换热特性基本相同。与等温空气射流相比，预混火焰射流中的热卷积量较大，导致效率较低。现有的传热学数据可直接用于许多实际应用。
The jet impingement heat transfer is a well-established technique for obtaining high heat transfer rates for many cooling and heating applications. Impingement heat transfer methods are widely used in domestic and industrial appliances. The impinging isothermal gas jets are used for both heating and cooling. However, premixed flame jets are used for heating the target surface. Present study is an attempt to compare the heat transfer characteristics of the isothermal air jets and premixed flame jets. The isothermal air jet having jet temperature of 30 °C (cold jet or ambient temperature jet), 100 °C (hot jet), and premixed methane–air flame jet (stoichiometric mixture) with Reynolds numbers of 500, 750, 1000, 1250 and 1500 and nozzle or burner to plate spacings of 2d, 4dand 6dare experimentally investigated for heat transfer characterisation. Thin metal foil technique is used for characterising isothermal air jets. For a fixed jet Reynolds number, the Nusselt number of isothermal air jet is found independent of the temperature difference between jet and surrounding fluid. A steady state technique is proposed for characterisation of premixed flame jets. The outcome of the present study reveals that the heat transfer characteristics of isothermal air jet and the premixed flame jet are almost same. The higher thermal entrainment in premixed flame jet in comparison with isothermal air jet results in a lower effectiveness. The present heat transfer data can be directly utilised for many practical applications.