Pengaruh Kecepatan Fluida Pendingin (Udara) Terhadap Unjuk Kerja Dan Karakteristik Perpindahan Panas Pada Radiator Sepeda Motor Yamaha Nmax 155CC

Penelitian ini menggunakan metode ɛ-NTU untuk menganalisis data. Radiator yang digunakan adalah radiator sepeda motor Yamaha Nmax 155cc dengan jenis aliran vertical, flat tube dan louvered fins, kipas/fan sebagai sumber angin simulasi, dengan campuran 50% air + 50% coolant radiator. Laju aliran air konstan 4 lpm dan temperatur fluida panas konstan 80. Variasi kecepatan aliran udara yang digunakan pada pengujian kali ini adalah 4-8 m/s dan diatur menggunakan Dimmer sebagai alat bantu. Dari pengujian yang telah dilakukan didapat laju massa aliran udara yang paling besar terjadi pada kecepatan kipas 8 m/s. Laju perpindahan panas yang paling besar terjadi dikecepatan kipas 8 m/s sebesar 0,0735 kW dan panas menyeluruh terbesar juga terjadi dikecepatan kipas 8 m/s yaitu sebesar 9,50 W/m2°C. Efisiensi radiator maksimum terjadi pada kecepatan kipas 5 m/s dengan nilai sebesar 7,59. Kata kunci: Efektifitas, Metode ε-NTU, Radiator Nmax 155cc. This study uses the ε-NTU method to analyze the data. The radiator used is a 155cc Yamaha Nmax motorcycle radiator with vertical flow type, flat tube and louvered fins, fan/fan as a simulation source, with a mixture of 50% water + 50% coolant radiator. The water flow rate is constant 4 lpm and the hot fluid temperature is constant 80℃. The variation of air flow velocity used in this test is 4-8 m/s and is adjusted using a dimmer as a tool. From the tests that have been carried out, the largest air flow rate occurs at a fan speed of 8 m/s. The highest heat transfer rate occurs at a fan speed of 8 m/s at 0.0735 kW and the largest overall heat also occurs at a fan speed of 8 m/s at 9.50 W/m2°C. The maximum radiator efficiency occurs at a fan speed of 5 m/s with a value of 7.59 Keywords: Effectivenes, ɛ-NTU Method, Nmax 155cc Radiator

Comparison of a Novel Polymeric Hollow Fiber Heat Exchanger and a Commercially Available Metal Automotive Radiator

A novel heat exchanger for automotive applications developed by the Heat Transfer and Fluid Flow Laboratory at the Brno University of Technology, Czech Republic, is compared with a conventional commercially available metal radiator. The heat transfer surface of this heat exchanger is composed of polymeric hollow fibers made from polyamide 612 by DuPont (Zytel LC6159). The cross-section of the polymeric radiator is identical to the aluminum radiator (louvered fins on flat tubes) in a Skoda Octavia and measures 720 × 480 mm. The goal of the study is to compare the functionality and performance parameters of both radiators based on the results of tests in a calibrated air wind tunnel. During testing, both heat exchangers were tested in conventional conditions used for car radiators with different air flow and coolant (50% ethylene glycol) rates. The polymeric hollow fiber heat exchanger demonstrated about 20% higher thermal performance for the same air flow. The efficiency of the polymeric radiator was in the range 80–93% and the efficiency of the aluminum radiator was in the range 64–84%. The polymeric radiator is 30% lighter than its conventional metal competitor. Both tested radiators had very similar pressure loss on the liquid side, but the polymeric radiator featured higher air pressure loss.

Development of Heat Transfer Surface Area Enhancements: A Test Facility for New Heat Exchanger Designs

Enhancing the heat transfer surface by usage of cellular metal structures, such as foams or wire structures, might allow enlarging the surface area, increasing the heat transfer coefficients, decreasing the material utilization, and enabling the flexibility of different geometrical dimensions. However their manufacturing and assembling in a large heat exchanger for performance testing and optimizing can be costly. Therefore a test rig was constructed for experimental characterization of heat transfer surface area enhancements. Heat exchanger samples with dimensions in the centimeter range can be measured. The fluid flow and heat transfer features of a micro pin fin wire structure made from copper by soft-soldering were experimentally characterized under steady-state forced air convection. The results are compared to performance characteristics of louvered fins. Heat transfer coefficients of the pin fins are twice as high as for the louvered fins. The relative expanded uncertainty of the Nusselt number is ±7%.