Optimal tube diameter on heat exchanger shell and tube type with 15 mega watt thermal power using fluent 6.3Siti Nurhasanah, Muhammad Subekti, Moch. Nurul Subkhi and Bebeh Wahid NuryadinMATEC Web Conf., 197 (2018) 02011DOI: https://doi.org/10.1051/matecconf/201819702011