Parallel flow expansion for pressure and superheat control

A method for operating a Heating, Ventilation, and Air Conditioning (HVAC) system, comprising:

• receiving, at a fixed expansion device, a refrigerant from a condenser, wherein the fixed expansion device is fluidly coupled to the condenser and comprises a tubular structure with an opening;
• receiving, at a variable expansion device, the refrigerant from the condenser;
• outputting, by the fixed expansion device, a first portion of the refrigerant to a first downstream HVAC component at a fixed flow rate;
• applying a first force to a pin of the variable expansion device based on a temperature of a primary evaporator, wherein:
• applying the first force to the pin repositions the pin within the variable expansion device;
• and
• the size of the pin is proportional to a ratio between a maximum variable flow rate of the variable expansion device and a total flow rate that is equal to the fixed flow rate plus the maximum variable flow rate of the variable expansion device;
• applying a second force to a valve of the variable expansion device based on the first force;
• and
• outputting, by the valve of the variable expansion device, a second portion of the refrigerant to a second downstream HVAC component at a variable flow rate based on the second force.

A Heating, Ventilation, and Air Conditioning (HVAC) system, comprising:

• an evaporator configured to:
• receive a refrigerant in a liquid state;
• evaporate the refrigerant into a gaseous state;
• and
• output the refrigerant in the gaseous state;
• a compressor fluidly coupled to the evaporator, configured to:
• receive the refrigerant in the gaseous state;
• compress the refrigerant;
• and
• output the compressed refrigerant in the gaseous state;
• a condenser fluidly coupled to the compressor, configured to:
• receive the compressed refrigerant from the compressor;
• condense the compressed refrigerant from the gaseous state into the liquid state;
• and
• output the condensed refrigerant in the liquid state;
• a fixed expansion device fluidly coupled to the condenser, comprising a tubular structure with an opening that is configured to:
• receive the condensed refrigerant from the condenser;
• output a first portion of the condensed refrigerant at a fixed flow rate, wherein the fixed flow rate is proportional to a diameter of the opening of the tubular structure;
• and
• a variable expansion device fluidly coupled to the condenser, wherein:
• the variable expansion device is configured to:
• receive the condensed refrigerant from the condenser;
• output a second portion of the condensed refrigerant at a variable flow rate, wherein the variable flow rate is proportional to a temperature of the evaporator;
• and
• the variable expansion device comprises:
• a flexible diaphragm configured to apply a first force to a pin based on the temperature of the evaporator;
• the pin operably configured to apply a second force to a valve based on the first force, wherein the size of the pin is proportional to a ratio between a maximum variable flow rate of the variable expansion device and a total flow rate that is equal to the fixed flow rate plus the maximum variable flow rate of the variable expansion device;
• and
• the valve fluidly coupled to the condenser and configured to output the second portion of the condensed refrigerant.