Heat Pump Ejector Circuit for Cold-Climate Compressor Efficiency
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Solution Overview
Problem
Existing heat pump systems are limited by the operational range between indoor and outdoor heat exchangers, particularly in cold climates, and there is a need for improved compressor energy efficiency to operate effectively in colder environments.
Innovation Solution
Incorporation of an ejector into the refrigerant circuit of heat pump HVAC systems, which combines flows of refrigerant to maintain pressure and temperature differences, allowing for expanded operational ranges and reduced compressor work input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the operational range between indoor and outdoor heat exchangers is expanded to colder temperatures, then the heat pump can operate in colder environments, but the compressor energy efficiency deteriorates due to increased pressure difference requirements
Solution Approach 1:
The refrigerant flow is divided into two separate circuits: a high-side circuit operating between the compressor and indoor heat exchanger, and a low-side circuit operating between the ejector and outdoor heat exchanger. This segmentation allows each circuit to operate at optimized pressure levels, enabling cold climate operation while maintaining compressor efficiency by preventing excessive pressure differences.
Solution Approach 2:
The ejector acts as an intermediary device that connects the high-side and low-side circuits. It uses the expansion of high-pressure refrigerant to drive the circulation of low-pressure refrigerant through the outdoor heat exchanger, thereby mediating between the two circuits and enabling the system to operate in cold climates without requiring the compressor to maintain excessively high pressure differences.
2Temperature
If the pressure difference between compressor input and output is increased to enable colder temperature operation, then the operational range expands, but the compressor work input increases
Solution Approach 1:
The system segments the refrigeration cycle into high-side and low-side circuits with distinct pressure ranges. The compressor only needs to maintain pressure difference across the high-side circuit, while the ejector handles the low-side circulation, thereby reducing the total compressor work input required for cold climate operation.
Solution Approach 2:
The ejector utilizes the inherent expansion energy of high-pressure refrigerant to self-drive the circulation of low-pressure refrigerant through the outdoor heat exchanger. This self-service mechanism eliminates the need for the compressor to provide additional work input for the low-side circuit, enabling colder temperature operation with minimal increase in compressor power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The ejector system enables heat pump operation at lower ambient temperatures, enhancing energy efficiency and expanding the operational range of heat pumps to colder conditions, such as down to 5 F (−15 C) or −15 F (−26 C) ambient temperatures.
Implementation Method 1
an ejector is in fluid communication with the refrigerant circuit. When the heat pump HVAC system is in the heating mode, the refrigerant circuit includes a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger. Additionally, the ejector is configurable to combine the first flow and the second flow into a combined flow
Implementation Method 2
a refrigerant flows through an HVAC circuit where the refrigerant is compressed in a compressor
Implementation Method 3
In the condenser, heat is exchanged between a medium such as outside air, water, or the like and the refrigerant
Implementation Method 4
From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature
Data Source
AI summary
A heat pump heating, ventilation, and air conditioning (heat pump HVAC) system is operable to use a refrigerant to heat or cool an indoor space with a refrigerant circuit performing a reversible vapor compression cycle between an outdoor heat exchanger and an indoor heat exchanger. The heat pump HVAC system includes an ejector in fluid communication with the refrigerant circuit. The refrigerant circuit includes a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger; and the ejector is configurable to combine the first flow and the second flow into a combined flow, at least a portion of which is returned to the compressor.