Heat transfer Chilled water tank help - Aspiring HVAC/thermal Engineer 1

[BlackestKnight]

Hello All,

(I posted this also in the HVAC/R forum because the question kind of pertains to both.) I am new to this forum, and to the field of Facilities and HVAC engineering. I am doing an internship for a chemical manufacturing company and the company uses a lot of used equipment for its maintenance/Facility Engineering department.

We have an HDPE uninsulated water storage tank and its in the vicinity of a compressed air unit and a boiler. The tank isn't insulated so the chiller is doing more work than required so I found this

http://www.radiantbarrier.com/double-bubble-insulation.htm

A reflective bubble wrap insulation. I have a few questions if anyone would please be willing to help.

1. How can I calculate the amount of heat we should be able to reflect at a given temperature of 80 F?

2. How can I justify this project in my proposal? would I measure the amount of power generated currently by the chiller to maintain the current chilled water temperature and compare it to the new, insulated temperature before performing a cost analysis?

3. The insulation is typically for roofs though would the same properties hold for an HDPE tank?

 

[Latexman]

faq731-376

Rule # 4, "Please do not cross-post the same question to two or more fora. If you feel strongly that your post needs to reach the audiences of two different fora, post your question to one forum and then post a link to that thread in the other forum."

Good luck,
Latexman

 

[som1973]

First try to calculate amount of heat gained by water, with HDPE tank without insulation.

Q = α A dt

Q = heat gained by water in BTU/HR
α = Heat transfer rate of water with HPDE Material (Tranmission surface), water and air on each side, search for α values - without insulation. BTU/HR FT2 F
A = Surface Area, PI x D X height of tank. FT2
dt = Temp Diff between water and air. F

Do similar calc, considering insulation, search for α values With insulation. BTU/HR FT2 F

Q = Q1-Q2 = "X" BTU/HR & convert to "X" K.W, SO your chiller drive will be absorbing this extra "X" K.W,

 

[BlackestKnight]

I apologize Latexman I just saw the rule board, won't happen again.

@Som1973

Thank you, I apologize I did not list the dimensions.

H = 15'

D = 8'

Tw (temp of water) = 55 F

Ta (temp of air) = 80 F
with heat transfer calculation what I did was

Qwater = α *A * (Tw-Ta)

α = 0.58

A= 376.8

dt = 25F

Qwater= 5463.6 BTU/HR FT2 F

Then Q of the HDPE with α = 0.50

Q = 0.50*376.8*25 = 4710

dQ= 753

With this value, I'd find the α of the radiant barrier and get the energy savings, however from what I am just now reading, radiant barrier reflects emissivity or radiant heat (banging head now). Does this stop me from continuing? because although it reflects heat, radiant heat is still a form of heat transfer, I just can't find any solid coefficient values for the double bubble.

 

[IRstuff]

It's bubble wrap, which places it somewhere between pure air and styrofoam, and there's not that much difference between the two. Or you could pick a slightly poor aerogel.

TTFN
faq731-376

 

[som1973]

Refer

http://www.dandadec.co.uk/Donard Files/Pulko.pdf

see page 6 for Bubble wrap properties, this may help you !

 

[IRstuff]

Alibaba shows a slightly lower thermal conductivity:

http://www.alibaba.com/product-gs/469739655/Fireproof_Heat_Reflective_Bubble_Foil_Wrap.html

TTFN
faq731-376