SoftwareHeat Exchanger for Domestic Boilers
The functioning principle of an heat exchanger is very simple: burnt gases are drawn over the fins of the exchanger, which transfer heat to the water circling within the fi ns matrix, where the matrix consists of an orderly array of identical cells.
Fig.1 - Heat exchanger to be embedded in a domestic boiler
When designing an heat exchanger, the goal is obviously to maximize the heat extracted per unit area. At the same time it is also important to minimize the gas pressure drop across the unit, as this measure directly determines how large a fan is needed to draw the gases through the unit, thus affecting size and cost.
High heat flux, and low pressure drop are then crucial to produce small, and cheap, heat exchangers. To solve this problem, Calortecnica S.p.A. turned to modeFRONTIER. The problem was addressed by parameterizing an elementary cell of the matrix (i.e., the shape of an exchanger fin) using Bezier curves with 11 control points. Manufacturing size constraints were imposed on the fin shape.
The flow of gases and the heat transmission were modelled with the FIDAP finite elements fluid dynamics and heat transfer code. The cascaded flow across the matrix fins was synthesized using flow across a single column of elementary cells, simulated at a range of Reynolds numbers.
After the MOGA algorithm extracted 8 generations with 64 elements each, the designs on the Pareto Frontier were singled out, and the decision support tool was used to extract a single utility function that captured the designer preferences. Subsequently, a quasi Newton hill climber was used, starting from one of the designs, to maximize this utility function.
The end result was a design that yielded the same heat fl ux as the original design, but with a 22% weight reduction and a 35% decrease in volume.
Fig.2 - Geometries tuned by optimization
References
[1] Spicer, D., Cook, J., Poloni, C. and Sen, P. - Frontier: Industrial Multiobjective Design Optimisation. - Proc. 13º ECCOMAS98, Athens, September 4-7 1998.
[2] Spicer, D. - Frontier: open system for collaborative design using Pareto frontiers.