Shell and Tube heat Exchangers made by Bell & Gossett. Bell & Gossett shell tube heat exchangers, models SU and WU. Choose from Bell & Gossett heat exchangers for steam or water along with their replacement shell tube heat exchanger cores - known as tube bundles. When that Bell & Gossett heat exchanger starts leaking it may be time to replace the heat exchanger core tube bundle. Great pricing! Order online or give us a call at 1-877-775-7705. State Supply is a leading distributor of Bell & Gossett products for both steam heating systems and hot water heating & cooling applications.