6 replies to this topic

[ColorMan]

i am trying to determine if it is better to have laminar or turbalent flow for my system.

i have a hot material (nylon 6) that needs to be cooled. so i will have a jacketed wall (heat exchange plate) that will have water running through it.

should i use dimensions that will result in laminar or turbalent flow?

also, i am having trouble finding a simple equation to use that involves laminar flow in order to calculate my reynalds number.

thanx!

[Root]

Hi,

To Find out the nature of flow, calculate the Reynolds Number from this Equation.
ReN=Mass of fluid X Dia meter of pipe/viscosity of that fluid

after calculating the Reynold number then you will be able to know about the nature of flow and for 2nd part of your question let to explain by some expert.


Good luck

[ColorMan]

i understand how to determine whether it is laminar, transitional, or turbalent flow.

i am looking to determine which one results in optimal heat transfer when using water.

[Andree]

in most cases (all?) the turbulent flow results in higher heat transfer coefficients... but it also requires more energy (higher flowrate) to pump water through the same geometry

[ColorMan]

thanx for the reply andre.

so turbalent flow is what i'll go for.

know i am going to have a series of vertical plates that the water will be flowly through. the water will enter in the bottom of the plate, and exit the top.

my issue is that the characteriskic length is too large, which creates issues of me having turbalent flow.

i have 2 options.

1. if i have my heat exchange plates with only baffles inside (about 5) I will have to raise my pump to 80+ GPM.

2. or i could make a U-shaped path inside of the plates that will control where the water is able to flow. i can have a smaller pump in this case, but.... how will this effect my surface area?

normally the surface area would just be the height*width as in case 1, but in case 2, there seems like there would be less since the water will not be able to touch every aspect of the plate, and instead only the part where its tube is. so would i just use the surface area for the U-shaped tubes inside the heat exchange plates?

[joker1]

Hi ColorMan,
You mentioned that you have to cool Nylon. Is it in molten form or is it a solid ? Cooling of polymers can be tricky. For example if you cool a polymer melt with cooling water the polymer will solidify at the heat transfer surface blocking all heat transfer. In fact the colder the cooling water the worse the problem.
Please describe the system to get more meaningful assistance.