A number of solar domestic hot water systems and many combined space and water heating systems have heat exchangers placed directly in the storage fluid to charge and/or discharge the tank. Operation of the heat exchanger produces a buoyancy-driven flow within the storage fluid. With a view toward controlling the flow field to increase heat transfer, a cylindrical baffle is inserted in a 350 l cylindrical storage tank. The baffle creates a 40 mm annular gap adjacent to the tank wall. A 10 m-long, 0.3 m2 copper coil heat exchanger is placed in the gap. The effects of the baffle on the transient heat transfer, delivered water temperature, heat exchanger effectiveness, and temperature distribution within the storage fluid are presented during discharge of initially thermally stratified and fully mixed storage tanks. The baffle increases the storage side convective heat transfer to the heat exchanger by 20%. This increase is attributed to higher storage fluid velocities across the heat exchanger.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Feb 2009|
Bibliographical noteFunding Information:
This study was supported by the National Renewable Energy Laboratory, the US Department of Energy, and the University of Minnesota Initiative for Renewable Energy and the Environment. This material is also based upon work supported under a National Science Foundation Graduate Research Fellowship awarded to Julia Haltiwanger. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the sponsors.
- Heat exchanger