Effect of Concave Corrugated Tube Shape on The Effectiveness of Double Pipe Heat ExchangerI Made Arsana, Theodorus Wiyanto Wibowo, Muhaji, Handini Novita Sari and Haydar Aly KurniawanE3S Web of Conf., 517 (2024) 10002DOI: https://doi.org/10.1051/e3sconf/202451710002