Numerical study on thermal hydraulic performance of a Printed Circuit Heat Exchanger

摘要

Very High Temperature Reactors (VHTRs) require a high-temperature and high integrity Intermediate Heat Exchanger (IHX) with high effectiveness to efficiently transfer the core thermal output to a secondary fluid for electricity generation, hydrogen production, and/or other industrial process heat applications. A class of compact plate-type heat exchanger, namely, Printed Circuit Heat Exchanger (PCHE), is one of the leading candidate IHX configuration being considered for VHTR applications. In the current study, simplified computational models of PCHE are investigated using Fluent? software. The geometry of the models considered in the study replicate the PCHEs that were fabricated using Alloy 617 plates for use in a High-Temperature Helium Facility (HTHF) at The Ohio State University. The computational cases investigated are based on the design conditions of the HTHF, i.e., a maximum operating pressure of 3 MPa, hot and cold side inlet temperatures of 1173 K and 813 K, respectively, and mass flow rates varying from 10 to 80 kg/h. This range of mass flow rates correspond to laminar and laminar-to-turbulent transition flows in the PCHE flow channel passages. The laminar-to-turbulent transition behavior has been numerically investigated for the semicircular and circular channel geometries. The numerical study showed that the transition is observed at Reynolds numbers of 2300 and 3100 for the circular and semicircular channels, respectively. Heat transfer and pressure drop characteristics are evaluated to provide preliminary performance data for the PCHEs fabricated at operating temperatures similar to those of the VHTRs. Local convective heat transfer coefficients are calculated for the hot and cold sides and compared with the available correlations for the circular and semicircular ducts. Overall performance characteristics of the PCHE computational model are computed and described in terms of the thermal effectiveness, number of transfer units, and overall heat transfer coefficient.