Counterflow Method
The counterflow method chills the boiled wort by recirculating cold water through the following path:
Cold water in mash tun to pump 1 to outer copper tubing in counterflow back to mash tun.
While the hot wort follows this path:
Boiled wort in kettle to inner copper tubing in counterflow (by gravity) to end of tubing and into a bucket.
The temperature of the 212-degree wort is instantly reduced to approximately 75 when it exits the system.
 
Wort may be chilled as quickly as gravity and tubing will allow.  Pumping water through the inner tubing with an additional pump (pump 2) after it has been brushed may clean the system.  Brushing to remove cold break material is done after the unfastening of the clamped flexible copper tubing.
 
Even though this system has not been constructed, I am convinced that it will work well. The design took into account existing counterflow technology in which the hot wort and cold water flow in opposite directions for at least 15 feet.  Most commercially available systems chill with tap water at normal flow rates.  My system utilizes a pump for rapid flow over 18 feet using cold water from the mash tun.  The water in the mash tun may also be loaded with ice for improved chilling capacity.  The combination of rapid flow, optional addition of ice, and unique & cleanable design, should result in an efficient and easy-to-maintain chiller.

 
Materials                                                                                                          Special Equipment
18 Feet of 3/8”OD (1/4”ID) Solid Copper Tubing                                         Copper Tube Bender (3/8”)
20 Feet of 1/2”OD Solid Copper Tubing
2 Feet of 3/8”OD Flexible Copper Tubing
10  1/2” Copper T Joint
8  1/2” Copper End Caps
2  1/2” Compression to 1/2” Sweat with Nuts
3  1/2” Full Port Ball Valves (sweat)
1  1/2” to 3/8” Copper Reducer
1  3/8” Copper T Joint
Several 1/2” Copper Elbows
1  1/2” Sweat to 1/2” NPT (to attach the Temperature Gauge)
1 Temperature Gauge, like model#  2A608, but with a short stem, 1/2”NPT, Grainger’s, www.grainger.com
2 Rubber Washers (no center hole)
2 Pieces of Stainless Steel (for inside of compression nuts)
4 pieces of Hose with 4 to 8 Hose Clamps

 
Procedures
None established.  This design has not been built.