In modern dishwashers, heat pumps are integrated for heating up the water in order to reduce the consumption of electrical energy compared to conventional dishwashers with electrical resistance heating. Nevertheless, analyses have shown that there is still unused potential to shorten the duration of the dishwashing program, lowering both the electrical power and the water consumption. Many of these new insights and findings can also be adapted to dishwashers without heat pumps.
The two competence centers “Thermal Energy Systems and Process Engineering” and “Fluid Mechanics and Hydraulic Machines” support the V-ZUG AG in the optimization of the heat pump and the drying process as well as in the development of a new water pump.
In the area of optimizing the heat pump and the drying process, different mathematical-physical simulation models were developed. With the aid of these models it is possible to investigate and assess different concepts and configurations. In this way, the most promising measures can be identified and implemented very quickly. Furthermore, the effort for experimental studies can be reduced significantly.
For example, one result is a new type of condenser that is available for heat pumps. It notably reduces the logarithmic temperature difference of the heat transfer due to increased heat transfer coefficients. Furthermore, an evaporator was developed that is embedded within a latent heat storage filled with a phase change material.
For drying dishes, a new drying concept was developed, which provides targeted cooling of one of the dishwasher walls dependent on the temperature of the drying air. The goal is to avoid mist in the dishwasher for the following reasons. On one hand mist lowers the heat and material transfers and, on the other hand, it remoistens already dry dishes. This drying concept is particularly suitable for dishwashers without heat pumps.
During the entire dishwashing program, the water pump is in operation and is responsible for a considerable share of the energy consumption in modern, efficient dishwashers. By means of simulations (Computational Fluid Dynamics CFD), a new radial pump with a higher hydraulic efficiency was developed and designed. As well as the increased hydraulic efficiency it is also more stable when pumping fluids with air entrained, such as foams.
The results of this project helped V-ZUG AG to extend their technological leadership in the field of innovative and energy efficient household appliances.