Modelling of Plate Heat Exchangers and Their Associated CO₂ Trancritical Power Generation System

Globally, there is no shortage of low-grade waste and renewable heat sources that can be converted into electricity and useful heat using applicable thermodynamic power cycles and appropriate working fluids. As a natural working fluid, CO₂ is a promising candidate for application in low-grade power generation systems but require optimised design and evaluation. Since CO₂ working fluid has a low critical temperature (31.1°C) and high critical pressure (73.8 bar), a CO₂ low-grade power generation system will most likely undergo supercritical Rankine (T-CO₂) cycles. A T-CO₂ system normally consists of a CO₂ supercritical gas heater, expander, recuperator, condenser and liquid pump with the CO₂ gas heater being a crucial component in determining system thermal and exergy efficiencies. In this paper, the models of a thermal oil-CO₂ plate gas heater has been developed and validated with measurements of a 5 kW_e T-CO₂ system test rig. The model is then integrated with other system component models to establish the system model. The system model can be used to evaluate and compare system performances at different operating conditions, including variable CO₂ gas heater pressures and heat sink parameters, thereby optimising system operations.