By Tom Soukup
When it comes to heating water in large pools, one thing is clear: a substantial amount of heat is required. Consequently, the water heating systems employed are robust. In many cases, these systems use boilers and heat exchangers as the heat source, opposed to direct-fire pool heating units commonly found in smaller pool facilities.
This choice is driven by two primary factors: boilers and heat exchangers offer extended system life cycles, and boilers are available in much larger capacities than direct-fire heaters. At many of these installations, boiler systems serve not only for natatorium space heating but also dehumidification loads in addition to heating the bodies of water.
The author’s company specializes in designing, installing, and servicing pool heating systems, both large and small. The most prevalent method for transferring heat from the boiler to the pool water is using large shell-and-tube heat exchangers, although plate-and-frame heat exchangers are occasionally used as well. The author’s company prefers shell-and-tube heat exchangers but adds a unique twist to the design. By implementing minor adjustments to large pool heating systems, the company has found energy savings in the range of 10 to 20 per cent can be achieved. With more substantial modifications to the system, gas savings can exceed 40 per cent.
If heat exchangers are not regularly maintained, efficiencies will decline, and premature component failure can occur. Often, by the time the company is contacted for service, efficiency has decreased by more than 25 per cent due to factors such as metal degradation, deposits, clogging, and water bypass.
Beyond routine maintenance, one of the most effective practices to reduce fuel costs in large pools is to replace aging heat exchangers. Surprisingly, an in-kind replacement is seldom the best solution. Recalculating the heating load and choosing from a range of heat exchanger options can yield great results. The key lies in choosing the right heat exchanger.
Shell-and-tube versus plate-and-frame
Shell-and-tube heat exchangers are preferable to plate-and-frame heat exchangers due to their resistance to deposits, ease of servicing, and their notable reduction in head loss (resistance to pumping). While some plate-and-frame heat exchangers may offer slightly superior efficiency when compared to their shell-and-tube counterparts, they often require the addition of a booster pump package to operate within the system as intended.
