Reduced order model for flow distribution in tapered headers of U-type heat exchangers

Abstract

Flow maldistribution in the channels of plate heat exchangers (PHEs) results in uneven temperature distribution leading to thermal distortion of the plates, increased pressure drop, and reduced thermal efficiency. Ensuring a uniform flow distribution is paramount for the efficiency and reliability of these systems. Using a modified header shape has the potential to improve flow conditions. To date, there is no mathematical model to predict flow distribution for tapered headers in PHEs. In this context, a reduced-order model has been developed to rapidly assess the potential impact of tapered headers on flow distribution. This model marks a pioneering effort in developing a comprehensive model for estimating flow distribution and pressure drop applicable to both uniform and tapered headers of U-type PHEs, providing valuable insights without necessitating significant computational resources. Key structural parameters, such as header diameter, number of channels, channel area, and taper ratio, that influence flow distribution have been identified by solving the differential equations numerically. For tapered headers, a more uniform flow distribution occurs with fewer plates for the same flow resistance, i.e., the average total head loss coefficient (ζ). Beyond a critical header diameter, the flow remains nearly uniform, regardless of the ζ value. For higher ζ values, there is a channel area range where flow uniformity either increases or remains nearly uniform. One of the most significant findings is the identification of the conditions where tapered headers provide more flow uniformity compared to straight headers. Validated by existing literature, this model shows promising practical applications in the rapid design and optimization of plate heat exchangers.