Ejectors for heat pumps

Ejectors in heat pumps
Ejectors are innovative components that are used in heat pumps to significantly increase their efficiency. They enable a significant increase in efficiency by optimising and partially recovering the compression work required in the compressor.

How ejectors work
Ejectors work according to the Venturi principle. A high-pressure flow is accelerated through a nozzle, which leads to a drop in pressure. This pressure drop creates a vacuum, which makes it possible to attract a low-pressure flow (suction flow) that mixes with the high-pressure flow. The kinetic energy in the diffuser is then converted back into pressure energy, which leads to an increase in the pressure of the total mass flow.

Advantages
By recovering throttling losses, part of the compression work can be saved, which increases the overall energy efficiency of the heat pump

Ejectors can significantly reduce the required power of the compressor or even replace a compressor stage in multi-stage systems.

Ejectors allow adaptation to different operating conditions and can be used in different configurations to optimise performance.

Challenges
Despite their advantages, ejectors are not yet widely used in practice. Ejectors need to be precisely matched to their operating conditions, which places high demands on the design. Furthermore, uncertainty about the cost-benefit ratio is one reason why many manufacturers do not implement this technology.

Overall, ejectors offer promising opportunities for increasing efficiency in heat pump systems, but require further research and development in order to optimise their application in industry and make them economically attractive.