In this study, the consequences of variation of the longitudinal fins angle on the heat transfer improvement during phase change are investigated. Therefore, the melting process of RT 35 as a phase change material is studied for triple-fin and double-fin cases for different angles and the results are compared with of bare tube case. Results indicated that due to the natural convection domination, the upper fin does not leave a great effect on the total melting time. Considering the triple-fin heat exchangers, as the fins angle increases from 60 to 120, the total melting time reduces. However, when double-fin cases are under consideration, reducing the angle from 150 to 45 results in melting time reduction. More reduction in the angle increases the total melting time. Results also showed that the best cases among triple -fin cases and among the double-fin cases result in 22.5 and 62% reduction in melting time with respect to the simple heat exchanger. (C) 2017 Elsevier Ltd. All rights reserved.