Besant and Johnson (1995) point out that
... a simulation model must include all of the many design and operating variables. With such a large number of design variables and wide range of operating temperatures under which these systems perform, it is not surprising that, in the past, run-around systems have not been designed for least life cycle cost nor for high performance. The designer needs an accurate, validated numerical model of the thermal behavior of the run-around system, along with the detailed manufacturing costs associated with each coil design variable and the utility rate structure for fuel and electricity.
