Transient conjugated heat transfer in thermally developing laminar flow in thick walled pipes and minipipes with time periodically varying wall temperature boundary condition

• Published in: International journal of heat and mass transfer 2016-01, Vol.92, p.643-657
• Main Authors: Altun, Aziz H., Bilir, Şefik, Ateş, Ali
• Format: Article
• Language: English
• Subjects: Conjugate heat transfer; Laminar flow heat transfer in pipes; Minipipes; Numerical solution; Periodic temperature variation; Transient heat transfer
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2015.09.011

•Transient conjugated heat transfer for thermally developing laminar flow in thick walled pipes is analyzed.•Hydrodynamically developed flow is considered with periodically time-varying wall temperature in the downstream region.•A parametric study is done to analyze the effects of Pe, d′, kwf, αwf, and also Ω on heat transfer characteristics.•For too high Ω values, the amplitude of variation in heat transfer characteristics disappears.•For kwf>100, Pe>20, αwf>10 and Ω>9000, the effects of these parameters can be said to disappear. Transient conjugated heat transfer for thermally developing laminar flow in thick walled pipes is analyzed involving two-dimensional wall and axial fluid conduction. A two-regional, initially isothermal pipe is considered and the problem is handled for hydrodynamically developed flow with periodically time-varying outer wall temperature in the downstream region. The problem is solved numerically by a finite-difference method and a parametric study is done to analyse the effects of four defining parameters namely, wall thickness ratio, wall-to-fluid conductivity ratio, wall-to-fluid thermal diffusivity ratio, the Peclet number and also the effect of angular frequency. Considerable amount of heat is transferred through the upstream region due to both wall and fluid axial conduction. Heat transfer characteristics change periodically in time similar to the periodic change in the outer wall temperature. The results are found to be affected by the parameter values and by the angular frequency.