Channel flow, natural convection heat transfer

In the operation of PSDRS, core decay heat is transferred to the containment vessel, as shown in Fig 7 and the heat from the contamment vessel is dissipated to the air flow which is generated by the natural circulation from the density difference between the mr channel and the environment The heat dissipation to the air flow is made of two paths One is the direct convection heat transfer from the containment wall surfece and the other is an mdirect path to the air In the indirect path, heat is first transported from the containment vessel surface by radiation to the air separator which separates the hot air from the mcommg cold air Then the heat is dissipated to the air flow by convection... 

Air flows by natural convection through the channel formed between 2 20-cm high plates kept at a temperature of 50°C. If the distance between the 2 plates is 3 cm and if the ambient air temperature is 20°C, find the rate of heat transfer from the 2 plates to the air and the mean velocity of the air through the channel. 

Consider the natural convective flow of air at 10°C though a plane vertical channel with isothermal walls whose temperature is 40°C and whose height is 10 cm. Determine how the mean heat transfer rate from the heated walls varies with the gap between the walls. 

Sparrow. E.M. Chrysler. G.M., and Azevedo. L.F.. Observed Flow Reversals and Measured-Predicted Nusselt Numbers for Natural Convection in a One-Sided Heated Vertical Channel . J. Heat Transfer Vol. 106, No. 2. pp. 325-332. 1984. 

Equipment designs based on indirect conduction usually transfer the heat from the primary heat transfer fluid to the intermediate wall within some kind of internal duct or channel. Transfer coefficients for these cases depend on the nature of the flow (laminar or turbulent) and the geometry of the duct or channel (short or long). Expressions for evaluating the transfer coefficients for these cases are available in standard texts. An expression for the convective thermal resistance can be generated similar to that derived for the conductive resistance ... 

Heat transfer to a laminar flow in an annulus is complicated by the fact that both the velocity and thermal profiles are simultaneously developing near the entrance and, often, over the length of the heated channel. Natural convection may also be a factor. It is usually conservative (i.e., predicted heat-transfer coefficients are lower than those experienced) to use equations for the fully developed flow. 

Chatoorgoon, V., 2001. StabiUty of supercritical fluid flow in a single channel natural-convection loop. International Journal of Heat and Mass Transfer 44, 1963—1972. 

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