DEVELOPMENT AND VALIDATION OF ANNULAR FINNED TUBES EVAPORATOR FOR CROSS-FLOW CO-CURRENT EXHAUST GAS - R245FA ORC SYSTEM

Abstract

An in depth analytical study was performed to predict the performance of annular finned tube in staggered array type evaporator used for exhaust gas- refrigerant (R245fa) system in organic Rankine cycle (ORC). The result was compared with simulated performance conducted using the HTRI heat transfer software used for heat exchanger design optimization. CFD studies, using ANSYS/CFX, were also conducted to give an insight on the distribution of the exhaust gas around the fins, the associated pressure drop and the resulting temperature distribution. The performance of the evaporator, in terms of fin efficiency, thermal resistances, dryness (vapour quality), and output temperatures was obtained. Regions that require essential developments were detected and potentials for design innovation were highlighted. At the tube side, improvement is required in regions of single phase flow, while at the exhaust gas side considerable improvements are required. CFD analysis provided information on air flow distribution, pressure, and temperature contours, which can be used for improvement of future designs.