Heat Pump Dual-Mode Liquid Extraction Control for Subcooling Stability
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Solution Overview
Problem
Existing heat pump systems face instability and increased cost due to the interference between main and auxiliary circuit electronic expansion valves in downstream liquid extraction, and insufficient subcooling in upstream liquid extraction, affecting performance and efficiency.
Innovation Solution
A heat pump unit control system with upstream and downstream liquid extraction control manners, utilizing a heat exchanger, compressor, switching elements, and electronic expansion valves to form complementary extraction circuits, allowing for adaptive selection based on temperature conditions to optimize economizer design and system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If downstream liquid extraction is used, then subcooling degree before auxiliary circuit electronic expansion valve is ensured and liquid supply for auxiliary injection circuit is sufficient, but main circuit and auxiliary circuit electronic expansion valves affect each other causing system oscillation and instability
Solution Approach 1:
The patent divides the liquid extraction system into two separate circuits: upstream liquid extraction circuit and downstream liquid extraction circuit. Each circuit has its own electronic expansion valve (first electronic expansion valve for upstream, second electronic expansion valve for downstream). This segmentation allows independent control of each extraction path, preventing the mutual interference that causes system oscillation while ensuring sufficient subcooling and liquid supply through the appropriate circuit.
2Stability of the object's composition
If upstream liquid extraction is used, then electronic expansion valves in main and auxiliary circuits do not affect each other and system is stable, but liquid extraction may fail when subcooling degree at condenser outlet is insufficient
Solution Approach 1:
The patent implements dynamic switching between upstream and downstream liquid extraction modes based on real-time system conditions. The control system monitors subcooling degree at the condenser outlet and automatically selects the appropriate extraction circuit: upstream mode when subcooling is sufficient (maintaining stability), and downstream mode when subcooling is insufficient (ensuring liquid extraction reliability). This dynamic adaptation resolves the contradiction between stability and reliability.
3Quantity of substance
If downstream liquid extraction is used, then sufficient liquid supply is ensured for auxiliary injection circuit, but pressure loss of refrigerant is increased when passing through main channel
Solution Approach 1:
The patent applies preliminary subcooling action in the upstream liquid extraction circuit before the refrigerant enters the downstream extraction path. By pre-subcooling the refrigerant in the upstream circuit, the system ensures sufficient liquid supply for the auxiliary injection circuit while reducing the temperature differential in the downstream path, thereby minimizing pressure loss during refrigerant passage through the main channel.
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 system effectively improves economic efficiency, performance, and reliability by complementing the disadvantages of both extraction methods, enhancing liquid extraction effects and energy efficiency across various temperature conditions.
Implementation Method 1
a plate heat exchanger is often used as an economizer to improve the subcooling degree of the refrigerant before it enters the evaporator
Implementation Method 2
improve the subcooling degree of the refrigerant before it enters the evaporator
Implementation Method 3
a compressor, a condenser, an expansion valve and an evaporator are connected in series
Implementation Method 4
the main circuit throttling electronic expansion valve and the auxiliary circuit electronic expansion valve
Data Source
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AI summary
A heat pump unit control system, comprising a heat exchanger (1), a compressor (2), a first switching element (3), a second switching element (4), an enhanced vapor injection electronic expansion valve (5), and a main circuit electronic expansion valve (6). A first end (22) of the compressor (2) is connected to a first port (7) of the heat exchanger (1) successively by the first switching element (3) and the enhanced vapor injection electronic expansion valve (5), a second port (8) of the heat exchanger (1) is connected to an injection end (21) of the compressor (2), the end of the first switching element (3) connected to the compressor (2) is connected to a third port (9) of the heat exchanger (1), a fourth port (10) of the heat exchanger (1) is connected to a second end (23) of the compressor(2) by the main circuit electronic expansion valve (5), and the end of the first switching element (3) connected to the enhanced vapor injection electronic expansion valve (5) is connected to the fourth port (10) of the heat exchanger (1) by the second switching element (4).