Using an Ersatz Thermosiphon Loop to Model Natural Convection Flows Inside a Shallow Enclosure.

Burch, J. D. ; Gawlik, K. M.

Technical Information Center Oak Ridge Tennessee

关键词: Solar energy;    Analytical solution;    Boundary conditions;    Heat exchangers;    Heat storage;   

RP-ID  :  DE2001776940

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

Natural convection loops (NCL) can occur when extracting energy from thermal storage with immersed heat exchangers. To assist in heat exchanger design and annual performance simulations of such systems, this paper proposes modeling an NCL with a comparatively simple ersatz thermosiphon loop (ETL). In an actual thermosiphon loop, fluid in channels or pipes flows in a closed loop, driven by a net buoyancy head which is equal to the total pressure drop. In the proposed approach, ersatz flow channels corresponding to the actual NCL flow are first defined, based upon experiment, numerical solution, or other information. The heat transfer and friction coefficients in the simplified ETL model must then be adjusted to fit these known data. The test case analyzed here is a horizontal shallow enclosure with temperature boundary conditions at both ends. A numerical solution is used to calibrate the ETL, and an analytical solution is used to extrapolate to other conditions for testing the ETL mo del predictions. It is shown that over two orders of magnitude variation in heat transfer, the calibrated ETL model predicts the heat transfer to 8% RMSD.