The local heat transfer coefficient for finned surface increased to up to 77%.
"Heat Transfer Augmentation Between Circular Air Jet and Flat Plate Using Finned Surfaces" Paper, Heat and Mass Transfer Conference, Guwahati, India.
When heat must be removed from the barrel, a fan drives air over the external finned surface
of the barrel.
The Fin-B surface in the present test is similar to the finned surface (Fin-A) in the Chien and Lin (2005) study.
The average heat transfer coefficients of falling film evaporation on the plain surface and the finned surface at a fixed flow rate of 1.6[+ or -]0.2 g/s (0.003527[+ or -]0.00044 lb/s) for R-141b at 15.5[degrees]C (59.9[degrees]F [+ or -] 0.9[degrees]F) are shown in Figure 5.
During the present tests, bubble nucleation phenomena were found under many test conditions on either the plain surface or the finned surface. More bubbles were observed on the finned surface than the plain surface.
For the finned surface, bubbles grew in the grooves between fins.
where r is the radius, h is the heat transfer coefficient, [eta] is the finned surface
efficiency, k is the tube thermal conductivity, i means internal, and o means external; [h.sub.i] was evaluated with the Gnielinski equation, so it was possible to obtain [[eta].sub.o][h.sub.o] from Equation 12.
[(Area of finned surface
- Area of plane surface)/Area of plane surface]*100
Evaporator models for operation with dry, wet, and frosted finned surfaces
: Part 1--Heat transfer and fluid flow theory.
But, of course not everything is as simple as it may seem at first glance: transformers have in fact densely finned surfaces
with deep undercuts which make proper cleaning difficult.