Heat Transfer Performance of Twisted Heat Exchanger for Carbon Dioxide Gas in a Dispersed Power Plant System Using Marine Biomass Resource

This paper is to propose a basic concept of marine renewable energy power plant system as a dispersed one, which is composed of a marine biomass plantation and a micro gas turbine. In this system, high-efficiency compact heat exchanger becomes necessary for the limit of the marine plant space. The author has already reported about a steady and transient heat transfer process for CO₂ flowing over a horizontal plate under wide experimental conditions assuming a plate-type heat exchanger. For the heat transfer enhancement of the heat exchanger, the twisted plates were inserted in the tube and parallel plates. In the experiment, the overall heat transfer coefficients of the heat exchanger for carbon dioxide gas (CO₂) are measured to construct a fundamental database for the proposed marine renewable energy system. Moreover, the three-dimensional analysis of the twisted heat exchanger has been conducted using the commercial CFD code, CFD2000. The twisted plate with a thickness of 0.3 mm is inserted in a tube which inner diameter is 7 mm. The gas flow velocities are ranged from 2.5 to 7.18 m/s for the inlet gas temperature of 323K. In the experiment, the overall heat transfer coefficient increases as the gas flow velocity increases. In the numerical simulation, the fluid structure in the tube has been changed caused by the twisted plate. The flow velocity near the twisted plate increases due to the blockage of the flow-pass. The temperature distribution was affected by the helically twisting fluid motion.