I am using 3/8" copper tubing, but was thinking about going to 3/4". I would obviosly need to use a bigger diameter hose and reduce to be able to hook up to my hose bib. How much of a difference whould I see? Can I chill using less water; would it go faster?
For a given flow rate, you’d chill faster using the smaller diameter tubing. Greater surface area per unit volume. Doubling the tubing diameter will double SA, but quadruple V. So unless you can at least double the flow rate by using larger tubing, the 3/8" will be better.
To speed chilling, you need to increase SA/V, flow rate, and/or temperature differential.
Makes sense. Right now the chill water input is on the sam end as the hot wort input. Do you think switching chill input to the output end of the wort would make any difference?
What you have is NOT a counterflow wort chiller. It is a paralell flow wort chiller.
I’m interested in the answer though, if someone knows.
Yes, a lot.
Yes, it makes a big difference - chilling rate is a function of the temperature differential. It will chill quickly at the beginning of the tube the way you have it set up, but the chilling water will get hotter as it moves to the outlet, so the temperature difference may approach zero (depending on flow rate). If you have the cold side at the outlet, you can get it colder because you are maintaining a temperature difference even as the wort gets cool flowing to the outlet.
With counter-flow, your cooled wort temp will be within a few degrees of your raw cooling water temp.
Configured the way you descibe, your cooled wort will be a weighted average of the two temps (hotter finished wort temp).
Condensers work the same way too. 
Yes, it matter quite a bit as others have said.
The counterflow chiller I use is 3/4" convoluted copper inside a 1 1/2" copper jacket. Works great and fast.
::drool::
I just got around to opening the most recent issue of BYO and there’s an article in there on optimizing heat exchanger performance.
Nice.
“joy to me, woe to you”? Interesting translation of your signature line…
counter flow and parallel flow are different, in terms of rate of cooling probably less than you think. in a parallel flow exchanger the hottest part of the wort is with the coldest part of the coolant. this is a bigger temperature differential and the most you will get during a heat exchanger process. the big problem with these is that the larger the temperature differential the greater the thermal stresses induced on the components. in a counterflow exchanger, the coldest part of the wart is with the coolest part of the coolant and the warmest wort with the warmest part of the coolant. thus the temperature differential is more uniform.
Impressive. How fast is fast?
I use one of these I bought from Hearts in Orlando many years ago. It is an adapted AC heat exchanger. Hearts claims cooling to within 5 degrees of cooling water temp. By throttling my pump I get it down to <2 degrees.
Takes 15 gal from boiling to 62f in around 6 minutes. /w tap water. I’m going to try ice water tonight.
Well, the real family motto is :“Hooray for me, the he11 with you” or so my dad used to say when we kids were only thinking of ourselves. I’d like to think that I’ve grown past that. Thought the latin gave it a little more class.
there’s an old Bad Religion song that has that as the chorus, though with a more colorful word than he11
cool chill rigs punatic and fightdman
That is fast.