Research PaperInfluence of manifold heating and split flow on thermal-hydraulic characteristics: Application to heat exchangers having non-axisymmetric flow

- The flow distribution from a heated manifold to tubes is investigated.
- It is found that for a combined manifold and tube heating, a non-axisymmetric flow exists.
- A thermal axis at the minimum temperature is defined to calculate the mean temperature.
- All computed Nusselt number results are validated with the literature.

The flow distribution from a manifold to tubes occurs in the tube side of a shell and tube heat exchanger. The tubes increase the contact surface area thus improving the thermal performance, with an accompanied pressure loss due to the split and smaller hydraulic diameter after the split. The surface conditions of uniform temperature and heat flux are examined. Additionally, the manifold is subjected to the same thermal conditions to examine the impact on thermal-hydraulic performance. Three layouts are being considered, including a single tube, 4 tube, and 37 tube system. It is found that for a combined manifold and tube heating, a non-axisymmetric flow exists in the smaller tubes. To accommodate such flow behavior, it is recommended to define the thermal axis at the minimum temperature for each cross-section, to calculate the peripheral Nusselt number distribution. This procedure is applied to different channel geometries subjected to non-axisymmetric inflow from the heated manifold. All the computed results presented in this paper are also validated against the results available in the literature.