Book - School of Science and Technology

Non-storage calorifiers 219Figure 8.17 Steam-to-water plate heat exchanger (Spirax Sarco/Alfa Laval)cover plate providing pipework connections. Figure 8.17 illustrates a typical steam-towatertype.The extended area for heat transfer and high velocity flows in both primary andsecondary circuits enable the equipment to be very compact. Any deposition on the heatexchange surfaces will affect performance and water quality is critical as a consequence.Manufacturers claim the units are easy to dismantle and reassemble for maintenance.Calorifier ratings and mountingsSince, in most respects, a non-storage calorifier is a `boiler substitute', calculations todetermine the rating and number of units required should follow almost the same routineas that used for boiler selection. The only difference of any significance is that low loadefficiency need be considered only as a function of the standing heat loss from a calorifierwhich is heated when output is not required. As in the case of a boiler, reference should bemade to manufacturers' lists for actual outputs and sizes particularly since the use bysome of controlled flow paths and high velocities within the shell produce an enhancedperformance.As to mountings, those required for a non-storage calorifier are precisely the same asthe items which would be fitted to a boiler having an equivalent rating, as noted inChapter 10, pp. 276±78.