Here are some random thoughts on chilling wort. I hope that you will find them helpful, and not at all as exhaustive.
Chilling wort is perceived by some, myself included, as a way to precipate the cold break in your wort. It also heps to lower the temperature from boiling to pitching in a relatively short period of time. This supposedly will help reduce the risk of infection or other undesirable effects.
You have three basid types of chillers: the Immersion Chiller, the Counterflow Chiller, and a Plate Chiller.
The immersion chiller (IC for short) is probably the least expensive option. It is usually a coil of copper or stainless steel through which is immersed into the boiling wort and through which you run cold water. Most people immerse the chiller into your boiling wort 15 minutes prior to flame out (to sanitize the chiller). At flameout you turn on the water to begin cooling your wort.
The Counterflow chiller is also a coil of copper that is surrounded by a larger coil of copper or a garden hose. The counterflow chiller has the wort travelling in one direction in the smaller diameter coil, with cold water flowing in the opposite direction in the larger diameter coild. These work really well, but most people use a pump with them; they circulate wort through them to sanitize the chiller during the last 15 minutes of the boil.
A plate chiller is similar to a counterflow chiller in that the wort flows in one direction, and the cold water flows in the other. Instead of two coils, one inside of the other, it has several parallel plates that have cold water on one side and hot wort on the other.
Each chiller has its advantages and disadvantages. The IC has the advantage of being easy to operate, relatively inexpesive, and it leaves the cold break in the kettle. It also cools the whole kettle of wort as it works. It also does not require a pump to operate. The CF and Plate Chiller (correct me if I am wrong) both benefit from having a pump. The pump is used to circulate wort through the chiller to sanitize the chiller prior to flame out. The do not keep the cold break from entering the fermentor. Also, you have to be careful so as to not get hops and other stuff caught in the chiller. Generally these type of chillers work very well, but they only cool a small amount of wort (that which is in the chiller) at a time.
I use an immersion chiller and find that I get good results with it. Part of this is due to the fact that my ground water is cold (something that will benefit any chiller) and I create a whirlpool while chilling (which causes the wort to chill faster because of the movement). I chose an Immersion Chiller because it was the easiest to build. Search the forum to see how others might be built. Because of the level of difficulty, I think that you must purchase a plate chiller if you choose to go that route.
Having said all this, I think that you will benefit greatly from any type of chiller. Also, given their advantages or disadvantages, there are several things that can be done to overcome any problems or weaknesses of the respective designs.
(All the time that I am saying this, I am aware of a no-chill method that has come out of Austrailia. You can find out more on this from a recent episode on Basic Brewing Radio.)
I hope that you find this helpful.
Mark
