Geometry miniaturization in fin-and-tube heat exchangers for refrigerant charge reduction

The indications given by the F-gas regulation and also the European Green Deal are contributing to the growing spread of small heat pumps that in many cases can be affected by flammability issues coupled with the use of natural refrigerants. Consequently, the market is looking for ever more efficient solutions to be achieved with very compact components, to reduce cost and refrigerant charge and to comply with safety constraints. LU-VE has developed a new heat exchanger geometry specifically designed for small air-to-water heat pumps, giving significant advantages compared to the solutions currently available on the market. The adoption of a very small tube diameter, coupled with a fin shape optimized for this specific application through parametric CFD analysis, enables the ratio between thermal capacity and refrigerant charge to be increased by up to 40%. An experimental campaign has been set up to validate the theoretical analysis, showing good matching both regarding heat transfer performance and air pressure loss.