Heat pump unit control system with enhanced vapor injection capabilities for upstream and downstream liquid extraction
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Solution Overview
Problem
Existing heat pump systems face instability and increased pressure loss due to the mutual influence between main and auxiliary circuit electronic expansion valves, particularly in downstream liquid extraction, which affects system performance and efficiency, while upstream liquid extraction may fail under insufficient subcooling conditions.
Innovation Solution
A heat pump unit control system incorporating both upstream and downstream liquid extraction control manners, utilizing switching elements to selectively configure the liquid extraction path, ensuring complementary operation to enhance economic efficiency, performance, and reliability by adjusting the switching elements' states to form either upstream or downstream liquid extraction circuits based on temperature conditions.
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 is sufficient, but main circuit and auxiliary circuit electronic expansion valves affect each other causing system oscillation and increased pressure loss
Solution Approach 1:
The patent segments the liquid extraction function into two independent circuits: upstream liquid extraction circuit and downstream liquid extraction circuit. Each circuit has its own electronic expansion valve (first auxiliary circuit electronic expansion valve and second auxiliary circuit electronic expansion valve respectively), allowing independent control and operation. This segmentation eliminates the mutual interference between circuits while ensuring sufficient liquid supply to the enhanced vapor injection circuit.
2Device complexity
If upstream liquid extraction is used, then electronic expansion valves 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 creates a multi-functional liquid extraction system where the heat exchanger and control system can operate in multiple modes: upstream liquid extraction mode, downstream liquid extraction mode, or combined mode. The first and second auxiliary circuit electronic expansion valves can be independently controlled to extract liquid from different positions, making the system adaptable to various operating conditions and ensuring reliable liquid supply regardless of subcooling degree variations.
3Temperature
If downstream liquid extraction is used, then subcooling is ensured for low temperature heating, but pressure loss increases when refrigerant passes through main channel
Solution Approach 1:
The patent implements dynamic control of liquid extraction by using two independently controllable auxiliary circuit electronic expansion valves. The system can dynamically adjust the extraction position and amount based on real-time operating conditions such as temperature, pressure, and subcooling degree. This dynamic adjustment optimizes the balance between ensuring sufficient subcooling and minimizing pressure loss in the main refrigerant 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 liquid extraction efficiency, reduces compressor exhaust temperature, and ensures reliable operation across various temperature conditions by complementing the disadvantages of both extraction methods, thereby enhancing energy and economic efficiency.
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
the main circuit throttling electronic expansion valve and the auxiliary circuit electronic expansion valve
Data Source
AI summary
A heat pump unit control system, comprising a heat exchanger, a compressor, a first switching element, a second switching element, an enhanced vapor injection electronic expansion valve, and a main circuit electronic expansion valve. A first end of the compressor is connected to a first port of the heat exchanger by the first switching element and the enhanced vapor injection valve, a second port of the heat exchanger is connected to an injection end of the compressor, the end of the first switching element connected to the compressor is connected to a third port of the heat exchanger, a fourth port of the heat exchanger is connected to a second end of the compressor by the main circuit valve, and the end of the first switching element connected to the enhanced vapor injection valve is connected to the fourth port of the heat exchanger by the second switching element.