The TTHE by Peigné et al. was developed for a mechanical ventilation heat recovery system, in many cases in indoor installations. However, to accentuate the effect of heat losses on effectiveness, the surrounding conditions are modified to simulate heat exchange by forced convection due to the wind blowing perpendicular to the TTHE under the following conditions according to the Beaufort scale (e.g., Saucier ): light air of 1. 3 m s ⁄ and moderate breeze of 7.9 m s ⁄ . The inlet temperatures and capacity ratios are the same as in Table . Overall heat transfer coefficients are calculated (iteratively) for each additional meter of TTHE length using the definitions and correlations described by Peigné et al. , except for forced convection in internal flow and laminar regime, where the heat transfer coefficient is estimated using the Hausen correlation .