Determining Film Coefficient
Determining Film Coefficient
(OP)
Dear all.
Currently i am investigating cooldown times from a multilayered pipe. I need help in finding an experiment to determine the film coeffcient of polypropylene, is this worth doing or should i just take a conservative value found in the (large) range given online?
Thanking in advance.
Currently i am investigating cooldown times from a multilayered pipe. I need help in finding an experiment to determine the film coeffcient of polypropylene, is this worth doing or should i just take a conservative value found in the (large) range given online?
Thanking in advance.





RE: Determining Film Coefficient
For copolymers the values differ a bit.
RE: Determining Film Coefficient
corus
RE: Determining Film Coefficient
Good luck,
Latexman
RE: Determining Film Coefficient
RE: Determining Film Coefficient
what i'd like to know is how much heat is tranferred away from the surface of the multilayered pipe. Since the top layer is injected moulded polypropylene, it is 'cooling rate' and 'strain rate' dependent.due to shrinkage with cooling, the level of strain depends on the rate of surface cooling. the problem in hand is the pipe is cooled with water flowing across it, and i'm trying to find a value of film coefficient for computational modelling.(see Polymer Engineering Forum/Field Joint Failure for more detailed info.) Previous values for forced convection with water were in the range of (if i remember right) 20-3000 and most likely incorporated turbulent and laminar flow. I was wondering if anyone knew of specfic codes/guidlines/experiments to determining this value or even better aimed towards flow across a pipe? Thanking in advance for any advice/direction pointing.
RE: Determining Film Coefficient
there are several complex equations. the simple one is....
H = k * C * (Re^m) * (Pr^.33) / D
where k = external fluid conductivity
Re = reynolds number of external fluid
Pr = Prandtl number
D = external diameter
C and m vary with Re, but average values are....
C = m = .5 ( but they vary considerably)
there are other equations discussed that better fit various ranges of Pr and Re.
daveleo
RE: Determining Film Coefficient