Patent ID: 7665427

Claim:
A heat exchange system for heating water, comprising: a first process shell-and-tube heat exchanger having a cold water inlet and a hot water outlet; at least a second process shell-and-tube heat exchanger also having a cold water inlet and being mounted in a water circulating circuit in parallel fashion with the first process heat exchanger to provide redundancy in case of the failure of either of the first and at least second heat exchangers; a steam source for continuously supplying steam to a selected one of a shell and a tube side of the first and second shell-and-tube heat exchangers; a steam trap associated with each of the first and at least second heat exchangers for collecting steam condensate, each of the steam traps having a closed position and an open position for discharging condensate, the discharge of condensate serving to allow more steam to enter the respective heat exchanger to provide additional heat for transfer to the water being heated; each of the first and at least second heat exchangers also having associated therewith a first and a second water blending valves mounted in series, each water blending valve having a cold inlet port and a hot inlet port and a blended water outlet, water from the blended outlet of the first water blending valve being directed to the hot inlet port of the second water blending valve, the first water blending valve acting to blend cold water and hot water to a predetermined temperature set point which is above a set point of the second water blending valve, to thereby bias the second water blending valve and minimize thermal hunting; a secondary heat exchanger having a first side for receiving a discharge of hot condensate from the steam traps and having a second side; an additional water circulation circuit for circulating a source of relatively colder water through the second side of the secondary heat exchanger to preheat the source of relatively colder water, the preheated water being circulated to the inlet of the first and at least second heat exchangers; and a safety by-pass operatively associated with the secondary heat exchanger for allowing the flow of the relatively colder water through the second side of the secondary heat exchanger, while by-passing the discharge from the steam traps in the event of a steam trap failure.