If you were a young fluids engineer starting in industry back in the 1970s or 80s, you were exposed to specialized thermo-fluid systems analysis software that was created by engineers. Their purpose was to solve the problems the engineers faced on a daily basis. They had names like BOLTJ, HOTRAD, and HYDFLO. All were command line driven and most of them had to be run from a mainframe computer.

They were clunky but they worked and most of them were quite fast. They were written in the language that the engineers knew – Fortran. Since it was used by the engineers who created them, there was little or no documentation to support the tool. A new engineer would be trained by the tool creator, and if there were any questions, they were referred to an engineering handbook or the company design manual. This in turn created an environment whereby the code was trusted and not questioned as it was created by a more senior and experienced engineer.

‘In-House’ codes were created out of necessity as there was nothing commercially available that could solve specific problems that engineers were faced with. Since these codes were created by the end user, there was a great deal of company specific design process and information embedded within them, much of which was proprietary data. All of this created an inertia, which helped perpetuate their use and made them difficult to replace. This paper outlines the case for switching to commercial software and what should be considered before making a decision that will affect your company's future and processes.