Estimation for heat loss to the working fluid in the heat exchanger of an Organic Rankine Cycle for a given concentration of gases

Abstract

Geothermal Energy is the thermal energy derived from the earth`s subsurface, often extracted from steam or hot water. It is a clean, reliable, and promising source of renewable energy. However, geothermal fluids brought to the surface through production wells contain non-condensable gases and minerals. These gases can reduce the heat transfer efficiency process in the surface plant, impacting the turbine`s efficiency when used to generate electricity. The gases mainly constitute CO2.
The paper demonstrates two process models one calculating the output from the turbine for similar input conditions as in one of the geothermal powerplant in New Zealand and the second calculating the change in heat transfer efficiency of the heat exchanger for a given concentration of gases in the geothermal fluid. The second process model is a cut-down model of the heat exchanger from the complete process model developed, which helps understand the loss of efficiency in heat transfer when geothermal fluid with different concentrations of gases passes through it. The heat exchanger is run for a range of values of the concentration of gases. The primary focus is on evaluating the change in heat transfer efficiency in the heat exchanger.