Investigation of twisted tape turbulator for fire tube boiler : part i. heat transfer

الملخص EN

The present work presents a new experimental study of the enhancement of turbulent convection heat transfer inside tubes for combined thermal and hydrodynamic entry length of one popular “tabulator” (twisted tape with width slightly less than internal tube diameter) inserted for fire tube boilers.

Cylindrical combustion chamber was used to burn (1.6 to 7kg/h) fuel oil #2 to deliver hot gases with ranges of Reynolds number (10500 to 21700), and (11400 to 24150) for both empty and inserted tube respectively.

A uniform wall temperature technique was used by keeping approximately constant water temperature difference (25ºC) between inlet and exit cooling water in parallel flow shell and tube heat exchanger.

The test tube consisted of smooth carbon steel tube of (2400mm) long and (52mm) internal diameter.

This test tube instrumented to derive local heat transfer coefficient and local flue gasses static pressure.

The experimental results show that for the same fuel consumption, twisted tape insert with (H/D = 11.15) enhanced the mean Nusselt number in (75.2 %), (68.8 %), (49.8 %), (40.3 %), and (16.7 %) for fuel consumption (7kg/h), (6.16kg/h), (4.5kg/h), (3.24kg/h), and (1.6kg/h) respectively.

A set of empirical correlations that permit the evaluation of the mean Nusselt number (for developing and fully developed region), and average Nusselt number (for developed region) for empty and inserted tube are generated for engineering applications.