Wort Chiller

Has anybody tried something like this for a wort chiller? It's 14 inches long, not sure of diameter, guessing 1 1/4 in. Outlets are 3/8 & 5/8

If you have it, go for it! But i didn't have one in my hands already i'm not sure i'd aim for this, it looks to be a tube within a tube. I found some diagrams on the 'net showing the internal tube has indentations, but overall i'd be concerned with the limited surface area contact between the two tubes. I think the standard range for homebrewing plate chillers is .25-.50 m^2 (approx 2 to 5 sq ft), if this unit was flat on the inside then it'd have something like .3 sq ft, maybe .6 sq ft if it were doubled with ridges?