Turbotec Products Inc.'s double-wall heat exchangers feature TRU-TWIST™ properties that allow for compact designs in potable water applications. These vented double-wall heat exchangers can be used in heat pumps, chillers and heat-recovery systems. In addition, they meet code requirements for domestic hot water in applications such as food-processing plants, restaurants, hotels and ice skating rinks. TRU-TWIST technology provides more surface area for a given length of tubing, while creating a turbulent mixing action that results in very high heat transfer through the tube walls. Turbotec Products Inc. Circle 6.