## HEAT TRANSFER CORRELATIONS FOR HYDRODYNAMICALLY DEVELOPED LAMINAR FLOW IN AN ANNULUS
## ResumoIn recent work, the classical problem of convective heat transfer in hydrodynamically developed laminar flow in an annulus with isothermal walls was examined in a resistor-network framework. A delta network of three convective resistances was proposed to represent this problem. It was shown that the resistor-network formulation leads to a simple presentation of the solution, is more consistent with the physics of the problem, and reveals new information about the heat transfer phenomenon. Particularly, the split of heat transfer between the annulus walls and the flow can be resolved based on the paired resistances that characterize this network. A classical analytical solution was used to derive series expressions for the paired resistances, which can be used for any fluid and any laminar flow rate. The coefficients and exponents of the series solution, however, must be re-evaluated for each radius ratio. In the present paper, approximate expressions are presented for the three paired convective resistances that fully characterize the problem. Curve-fit relations are presented for the coefficients and exponents of the series solution. In this way, three semi-empirical expressions are obtained which can be used for any combination of geometry, fluid, laminar flow rate and boundary temperatures. These proposed correlations can be readily evaluated in a spreadsheet and replace the tabulated data. Sample calculations are presented to demonstrate the utility, accuracy and ease-of-use of the results. |

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