Thermal Performance of Submerged Coil Heat Exchangers Used in Solar Energy Storage Tanks

Testing and analysis of immersed heat exchangers

“…Data from Klett et al (1983) are shown in Figure 3-9a for their SW heat exchanger in a 450-L (119-gal) tank at a flow rate of 15.1 L/min (40 gal/min). Although Klett et al did not include a diagram of the heat exchanger they tested, it appears from their description to be very similar to the SW bayonet heat exchanger we tested except that it had twice the heat transfer area.…”

“…They also concluded that closely spaced fins (4 fins/cm for their study) appear to reduce the convection heat transfer coefficient. Klett et al (1983) concluded that although the effectiveness of immersed coils was a function of both flow rate and temperature difference, an average effectiveness could be selected for a given flow rate and an intermediate value of the temperature difference.…”

“…Feiereisen (1982) experimentally examined the effects of several parameters on heat exchanger performance, including coil position, flow direction, flow rate, temperature difference, parallel versus series flow (using two heat exchangers), enhanced convection techniques, and coil orientation. Klett et al (1983) tested a single-wall and a double-wall bayonet heat exchanger, each with a heat exchanger area of 1.95 m (21 ft ), as a function of flow rate and temperature difference at two different tank volumes. concluded that "effectiveness is found to be nearly independent of temperature difference" but that "effectiveness is found to vary significantly over the range of flow rates tested."…”

“…All of the above tests were conducted at a temperature difference above 7°C (13°F) with most of the data in the Klett et al (1983) tests taken at temperature differences above 10°C (18°F).…”