(246j) CFD Modeling of Piston-Type Direct Work Exchangers

One-step (direct) Work Exchangers (WEs) can be considered as a type of process unit for mechanical energy recovery in chemical plants. The type of device was first introduced for reverse osmosis (Cheng et al., 1967; Cheng and Cheng, 1970). Dual Work Exchange Energy Recovery Device (DWEER) is a piston-type WE that has been widely used for seawater reverse osmosis (RO) desalination, which is one of the most efficient energy recovery systems developed to date. However, this type of units cannot be directly used for the pressurization/depressurization of process streams in gas phase in chemical plants. In this work, we present our investigation on the feasibility and design of a piston-type WE that works for processing gas-phase process streams. Our main approach is to use a Computational Fluid Dynamic (CFD) technique to construct a WE model. In simulation, different unit configurations are compared, and different operational characteristics, energy recovery efficiency, clearance volume, and safety issues related to leakage and mixing losses are considered. We also describe the dynamic behavior of the WE, which is critical in the improvement of energy recovery efficiency. Case studies will demonstrate great potential of using this type of unit in the process industry.

References:

Cheng CY, Cheng SW, Fan LT. Flow work exchanger. AIChE J. 1967;13:438-442.

Cheng CY, Cheng SW. Method and apparatus for pressurizing and depressurizing of fluids. US patent 3,489,159. 1970.