Abrégé

A CO2 based system, such as a heat pump system or a refrigeration system, is disclosed. The system comprises a plurality of ejectors arranged in parallel. Each of the ejectors comprises a motive port and a suction port. Each of the ejectors has a fixed geometry. A first actuated ball valve is arranged in front of the motive port. A second actuated ball valve is arranged in front of the suction port. The system comprises a control unit arranged and configured to control the activity of the ball valves on the basis of one or more predefined criteria.

Classes IPC  ?

• F25B 9/08 - Machines, installations ou systèmes à compression dans lesquels le fluide frigorigène est l'air ou un autre gaz à point d'ébullition peu élevé utilisant des éjecteurs
• F25B 9/00 - Machines, installations ou systèmes à compression dans lesquels le fluide frigorigène est l'air ou un autre gaz à point d'ébullition peu élevé

Abrégé

Method for defrosting an air source heat pump comprising a plurality of outdoor evaporators each comprising a number of coils each comprising fins and pipes. The heat pump comprises a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils. The method comprising: a) by using at least one temperature sensor measuring at least one temperature of at least one of the coils of at least one of the outdoor evaporators; b) activating the defrost system and hereby performing several defrost processes each having a duration separated by a pause without defrosting, when the at least one temperature is below a predefined temperature value, d) by using at least one temperature sensor measuring at least one outdoor temperature, the method comprises the following steps: determine a maximum allowable pause time in dependency of the at least one outdoor temperature.