heat energy required to heat liquid flowing through pipe

[Sonix1]

I have to heat up some oil flowing through a 1" pipe. I need to know the equation (mind is hazy now).
I want to use an electrical resistance heater to heat the fluid. Fluid is oil, about 140W gear oil.
I just want to get into the ballpark to size the heater.

Need to raise the temp from ~0*C to ~40*C. Flow rate is about 3 gallons per day.
It's for the cylinder lube oil on a natural gas compressor. It's a high pressure application, so it requires very viscous lube oil for the cylinders, which means we have to keep it warm, because at freezing ambient temps it will not flow very well. So I'm thinking about some type of electrical resistance heater over the piping.

This is a repost from

http://www.eng-tips.com/viewthread.cfm?qid=227618&page=1

Hoping that this forum is more appropriate.
Thanks

 

[Latexman]

Q = w.Cp.[Δ]T

Good luck,
Latexman

 

[vpl]

To expand on Latexman's correct formula, and with apologies if I'm belaboring the point:

Q is the energy required to change the temperature
w is the flow rate
c_p is the thermal capacitance of the oil
and [Δ]T is the change in temperature

Obviously, you need to make sure all your units are compatible.

The hard part may be coming up with the c_p value for your lube oil. I don't have any good values for that weight oil. Your best bet may be going back to the oil distributor.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[Sonix1]

Thanks a bunch guys!
That's about what I had come up with, but was having a tough time finding the Cp for my oil... I'll dig some more.

W is the flow rate, in mass or volume flow rate?
Thanks

 

[vpl]

it should be in kg/sec for metric units. English units, it's lbm/sec.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[IRstuff]

That's not counting losses and inefficiencies, natch...

TTFN

FAQ731-376

 

[Sonix1]

Great! Thanks guys.

Yea i'm not too worried about loses, I just to be in the ballpark, to see how much electricity I need to budget for.

Thanks again

 

[25362]

A rough specific heat capacity of 1800 J/(kg.K) would be, as you say, in the ballpark.

 

[MintJulep]

The energy required to heat up the oil - as calculated by the above formula - will be trivial in comparison to the losses to ambient with a 40C delta-T.