Çeşitli Soğutma Sıvıları İçin Dairesel ve Düz Tüplü Otomobil Radyatörlerinin Deneysel Performanslarının Karşılaştırılması

Bu çalışmada, otomobil radyatörlerinin ısı transferi performanslarını çeşitli motor soğutma sıvıları için test etmek amacıyla bir radyatör test sistemi geliştirilmiştir. Sistem, sirkülasyon pompası, soğutma sıvısı tankı, eksenel fan, elektrikli ısıtıcılar, PLC kontrollü sürücüler, çeşitli mekanik ölçüm cihazları ve test edilen radyatörlerden oluşturulmuştur. Testlerde dairesel ve düz tüplü iki farklı otomobil radyatörü ile su, etilen glikol, bunların 50/50 karışımı ve ticari bir ısı transfer yağı olmak üzere dört farklı soğutma sıvısı kullanılmıştır. Radyatörlerin attığı ısılar, geniş bir test koşulu aralığında deneysel olarak belirlenmiştir. Radyatörlerden geçen hava hızı 2 ve 4 m s-1 arasında, soğutma sıvısı debisi 0.1 ve 0.3 l s-1 arasında, radyatörlere giren hava akımının sıcaklığı 25 ve 35 °C aralığında değiştirilmiştir. Radyatörlere giren soğutma sıvısı sıcaklığı ise tüm testler için 90 °C'de sabit tutulmuştur. Soğutma sıvısı olarak su kullanıldığında, düz tüplü radyatörün dairesel tüplüye göre ortalama % 4.8 daha fazla ısı attığı; etilen glikol kullanıldığında ise düz tüplü radyatörün dairesel tüplüden ortalama % 66.4 daha fazla ısı attığı tespit edilmiştir. Soğutma sıvısı olarak ısı transfer yağı kullanılması durumunda, düz tüplü radyatörün dairesel tüplüye kıyasla ortalama % 101.6 daha fazla ısı attığı belirlenmiştir.

Comparison of the experimental performance of round and flat tube automobile radiators for various coolants

A radiator test system was developed to test the heat transfer performance of automobile radiators for various engine coolants. Thesystem was made up from a circulation pump, coolant reservoir, axial fan, electric heaters, PLC controlled drivers and instrumentsfor various mechanical measurements along with the tested radiators. Two different radiators, namely round and flat tube ones, andfour different engine coolants, namely water, ethylene glycol, their 50/50 mixture and a commercial heat transfer oil, were tested.The experimental heat dissipation rates of the radiators were evaluated under a broad range of operating conditions. The air speedwas changed between 2 and 4 m s-1, the coolant flow rate was varied between 0.1 and 0.3 l s-1, and the air temperature at the inletsof the radiators was changed between 25 and 35 °C, while the coolant temperature was fixed at 90 °C in all tests. The flat tuberadiator dissipated on average 4.8% more heat than the circular tube one for water coolant, while it rejected on average 66.4% moreheat than the circular tube one for ethylene glycol. Furthermore, when the heat transfer oil was used as coolant, the flat tube radiatordissipated on average 101.6% more heat than the circular tube one.

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