Buried Chilled Water Lines in tropics

[stanier]

I am seeking a good text reference or website that will provide a design procedure to determine the steady and unsteady state heat transfer for the above. I need to be able to determine the need for insulation on the buried pipe for moist and dry condiotions. How does the compaction/backfill affect the heat transfer coefficients?

Is there any software out there specific to such applications?

many thanks

 

[PacificSteve]

You may wish to check this link, looks like they do some analysis for free.

http://www.foamglasinsulation.com/ear.html

Your soil type will be somewhat important, but much less important if you select a life cycle based cost analysis to come up with the optimum thickness and type of insulation. In tropics you will find lava (basalt and such), coral, limestone, sand, and even organic stuff (real soil). Bedding is often sand, which has more of an insulating effect that plain soil, lots of air pockets. Rain running past the pipe can play havoc on your thermal losses if the rain is allowed to get into / flow through the insulation, either by design or poor installation techniques.

Energy costs as well as efficiency of the plant will play into the equation. You should also consider pumping costs, cause for the BTU lost, you basically pumped that much water for no reason.

Perhaps you knew all this already....I am curious why you want unsteady state?

Pacific Steve

 

[KernOily]

PipePhase will do the heat transfer calcs. You will have to supply the soil conductivity and ambient temperature data. There is a text called Pipeline Rules of Thumb, published by Gulf Publishing, that probably has what you need in that department. I think PipePhase only does steady-state heat transfer; for true unsteady-state HT I think you will be looking at a FEA program.

Having said that, I have used Pipephase to simulate unsteady conditions with pretty good success. It's all in how you set your time frame. I've used it to calculate, for example, the cooling of heavy crude oil in a loooong pipeline when the flow was stopped. We were trying to see how long it would take before the viscosity went thru the roof after the flow was stopped. So you can use the steady-state simulators on a trial and error basis to get what you need. Thanks!
Pete
pjchandl@prou.com

 

[KernOily]

If you can't find any data on the sopil conductivity let me know and I'll see what I can dig up for ya. Thanks!
Pete
pjchandl@prou.com

 

[stanier]

In response to Pacific Steve,

I want the unsteady state approach as I suspect that a reticulated chilled water system will have diurnal demands. If the demand at night drops right down the pipeline will heat up would it not?