Entrance effect on heat transfer to laminar flow through passages

This paper presents an accurate methodology to determine heat transfer coefficients near the thermal entrance region of ducts. These include parallel plate channels, circular pipes and rectangular passages. The solution technique uses a classical Airy differential equation when the thermal penetration is small. The validation and verification of these solutions are the essential part of this presentation as they are compared with available solutions. The results show a high degree of accuracy when the thermal entrance distance is very small. Also, this paper discusses the range of validity of this solution since its accuracy reduces at a larger distance from the thermal entrance location.