Refrigeration systems

An aircraft electronics system, comprising:

• one or more avionics electrical circuits;
• and
• a refrigeration system operatively connected to the one or more avionics electrical circuits, comprising:
• a main flow circuit configured to flow a refrigerant therethrough;
• a heat input disposed in the main flow circuit and configured to receive heat and transfer the heat to the refrigerant in the main flow circuit to output heated refrigerant flow;
• a passive pump disposed in the main flow circuit downstream of the heat input configured to receive the heated refrigerant flow from the heat input and to use the heated refrigerant flow to generate a vacuum at a pump port,
• a condenser disposed in the main flow circuit downstream of the passive pump for receiving flow from the passive pump, the condenser configured to receive heat from the heated refrigerant flow and reject heat to cool the heated refrigerant flow to output partially cooled refrigerant flow, wherein an outlet of the condenser is upstream of the heat input;
• a cooling branch having a cooling branch inlet in fluid communication with the main flow circuit and disposed downstream of the condenser, and a cooling branch outlet in fluid communication with the passive pump port to generate flow through the cooling branch with heated refrigerant flow through the passive pump;
• one or more cooling modules disposed in the cooling branch downstream of the cooling branch inlet and upstream of a cooling branch outlet, the one or more cooling modules in thermal communication with the one or more aircraft avionics electrical circuits and configured to provide cooling to the one or more aircraft avionics electrical circuits;
• and
• at least one expander disposed in the cooling branch between the cooling branch inlet and the one or more cooling modules, the expander configured to receive the partially cooled refrigerant flow and cause expansion cooling to output cooling flow to the one or more cooling modules, wherein the one or more cooling modules includes a plurality of cooling modules disposed downstream of the at least one expander, wherein the plurality of cooling modules are disposed in parallel with each other such that all cooling modules are connected to the cooling branch inlet directly and all cooling modules are connected to the cooling branch outlet directly, wherein the heat input includes a heat exchanger in thermal communication with a waste heat source of an aircraft system and wherein the plurality of cooling modules are in thermal communication with one or more aircraft electronics.