Two plate heat exchangers from Spirax Sarco have replaced two calorifiers that were designed to run on waste heat from CHP plant which generates electricity for the hospital. It is cooled by water, which then acts as a heating medium for the DHW heat exchangers. Paul King, project technician at Bradford Royal Infirmary, explains. ‘The calorifiers weren't particularly old, but we wanted to be more efficient. They were also starting to cause a few maintenance issues, and the need to strip them down for insurance inspections was a bit of a nightmare. PHEs avoid that completely.’
The plate heat exchangers predominantly run on water heat from the CHP cooling water, which is topped up with steam from the hospital's boiler when necessary. Mr King says, ‘The system takes as much heat from the CHP plant as possible and is only topped by 8% live steam on average three times a day, when the running load is at its highest.’
These units proved such a success that the hospital subsequently installed two more Spirax Sarco plate heat exchangers to provide hot water for heating. These units run mainly on plant steam, but the system is piped to accept steam from the CHP plant when available. This has enabled the hospital to simplify the heating system and remove a further six calorifiers in all.
Before the system was installed, Spirax Sarco estimated a 12% energy saving. Although it is too early to confirm definite figures, the hospital is confident that the actual savings will be closer to 5%, amounting to over £5000 a month.'
PHEs are generally more efficient than calorifiers and, being typically a quarter of the size, have lower heat losses. They are also easier to control and provide more efficient heat transfer.
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