Experimental development of natural convection heat transfer correlations for spiral-helical surface water heat exchangers (1385-RP)

Surface water heat pump systems utilize surface water bodies, such as lakes, reservoirs, and rivers, as heat sources and heat sinks. Closed-loop surface water heat pumps use submerged heat exchangers to extract or reject heat from the surface water body. Heat transfer between the heat exchanger and the lake is generally governed by buoyancy driven natural convection. One form of surface water heat exchanger is the spiral-helical heat exchanger, which is usually fabricated from high-density polyethylene tubing. Though the exterior convective resistance is an important part of the design calculation, convection correlations suitable for spiral-helical surface water heat exchangers are not available. In the current article, the authors cover an experimental study involving heat rejection experiments and heat extraction experiments on nine different spiral-helical configurations with three different high-density polyethylene tube sizes. Standard high-density polyethylene and thermally enhanced high-density polyethylene heat exchangers were also tested and compared. Convection correlations for spiral-helical heat exchangers were developed for heat extraction and heat rejection conditions. Heat transfer rate predicted with the correlations is compared against experimental data.