Experimental Study of Forced Convective Heat Transfer in Annular Passage with Axially Varying Cross Sectional Area

Abstract

Listen

Translate article

An experimental investigation of forced convective heat transfer in a passage with variable cross sectional area in the axial direction is presented. Experiments were performed with air flowing acceleratedly in the annular space constructed with a uniformly heated core tube and an outer tube with variable inner diameter. The results show that acceleration parameter K becomes a controlling characteristic quantity of heat transfer in this case. For this parameter below about 2×10-6, the local Nusselt number varies proportionally to the 0.77 power of the local Reynolds number, that is the same trend as in the turbulent case of uniform cross sectional area. Depending on the temperature distributions of fluid at the inlet, the heat transfer coefficient decreases and then increases, or monotonously increases with axial distance. Local heat transfer coefficients with K≤2×10-6 and in the axial region, where they increase with axial distance, are smaller than the values predicted by substitution of the same local flow conditions and diameter ratio into the fully developed heat transfer correlation for uniform cross section. These experimental results are correlated in the empirical formula.