Stainless steel plate heat exchangers . Brazed with 99.9+ percent Pure copper by Duda Energy . Plate heat exchangers have significantly good heat transfer rates because they use metal plates which have high heat conductivity rates and the plates are extremely thin. The plate heat exchangers also achieve high amounts of heat transfer through Convective forces with both working fluids. With large temperature differentials, great amounts of heat transfer can be achieved using a plate heat exchanger.This is an extremely popular unit for wood burning furnaces, radiant floor systems, refrigerant systems, straight vegetable oil conversions, beer chilling, air conditioning system and solar water heating systems. It will work for any application in which the desired result is for two fluids (liquid or gas) to exchange heat. Fluid a passes from the port on the left of the heat exchanger through every other channel created by the plates to the opposite end port on the left of the heat exchanger (looking at it the long way). fluid b passes from the port on the right through the other channels created by the plates and comes out the other port on the right side. The fluids are essentially touching each other through the plates and heat is transferred from the hot fluid to the cold fluid. (But the fluids do not mix).