GSP models > Heat transfer

In GSP there are several methods by which heat transfer among the various components and the surrounding environment can be modeled:

•A steady-state heat flux can be specified in a Duct component. A negative value will stand for a heat flux out of the system, whereas a positive value represents a heat input. For this component a heat flow is defined specifically and cannot be related to the system in the cycle calculations.

•A steady-state or dynamic heat flux using the Heat Sink component. The Heat Sink component has the ability to simulate heat transfer via conduction, convection and radiation among components and with the ambient environment.

•A Heat soakage heat flux during a transient, heating up or cooling down the gas path surrounding walls until thermal stability has been obtained (average wall and gas temperatures equal). Heat soakage has an effect on performance, for example slowing down an acceleration by absorbing part of the combustor released heat for heating up the combustor and/or turbine walls.

Compressor and turbine performance is significantly affected by heat transfer causing the process to become non-adiabatic. In GSP this effect is modeled by dividing the total heat flux (i.e. the sum of heat sink and heat soakage heat fluxes) in two heat fluxes, one happening before (start heat flux) and one after (end heat flux) the compression or expansion process. The compression or expansion process itself is happening 'in between' the points of the start and end heat fluxes and is calculated as adiabatic. The start heat flux increases the compression or expansion start temperature thereby affecting compression (increase if heat is added) or expansion (decreased in case of heat loss) work. The en heat flux does not affect the work but merely changes the exit enthalpy (and thus temperature).

The ratio of the start heat flux to the total can be user specified in the compressor and turbine Design tab sheets.