Heat Pump Vapor Injection Control for Hot Gas Temperature Limits
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Solution Overview
Problem
Heat pump devices face operational reliability issues due to high hot gas temperatures, which can lead to thermal destruction of compressor oil and reduced lubrication, especially at low outside temperatures and high heating flow temperatures.
Innovation Solution
Implementing an electronic expansion valve in the refrigeration circuit to regulate vapor injection, allowing for controlled superheating of refrigerant and reducing hot gas temperatures by injecting partially liquid refrigerant, thereby eliminating the need for an additional solenoid valve and enhancing operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vapor injection is used to maintain heating capacity at low temperatures, then heating capacity is improved, but hot gas temperature increases leading to thermal destruction of compressor oil
Solution Approach 1:
The patent changes the degree of superheat parameter of the injected refrigerant vapor. By reducing the superheat degree (injecting less superheated or even slightly subcooled vapor), the hot gas temperature in the compressor is reduced, preventing oil thermal destruction while maintaining adequate heating capacity through proper refrigerant dosage control
Solution Approach 2:
The patent implements feedback control by measuring the actual hot gas temperature or suction gas temperature and adjusting the expansion valve opening degree accordingly. When hot gas temperature exceeds a predetermined threshold, the control unit reduces the expansion valve opening to decrease the mass flow rate and reduce superheat degree, thereby lowering hot gas temperature back to acceptable levels
2Device complexity
If thermostatic expansion valve is used for vapor injection, then simple structure is achieved, but additional solenoid valve is required for standstill protection
Solution Approach 1:
The patent makes the expansion valve universal by equipping it with both temperature sensing capability (for vapor injection control) and solenoid valve integration (for standstill protection). This multi-functional expansion valve eliminates the need for separate protective valves while maintaining compressor protection functionality during standstill periods
Solution Approach 2:
The patent merges the standstill protection function (previously requiring a separate solenoid valve) with the vapor injection control function into a single integrated expansion valve assembly. The solenoid valve is incorporated directly into the expansion valve structure, allowing one component to perform both protection and regulation functions
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
This solution expands the operational range of heat pumps by reducing hot gas temperatures, preventing thermal destruction of compressor oil and maintaining effective lubrication, thus enhancing the reliability and efficiency of the device.
Implementation Method 1
The liquid refrigerant (which has been liquefied by the condenser 20) is supplied to the electronic expansion valve 80
Implementation Method 2
the thermal energy of the refrigerant is used in the economizer 60 to superheat the refrigerant to be injected
Implementation Method 3
the vaporized refrigerant is compressed in the compressor 10 and thus heated
Implementation Method 4
the refrigerant, which is under high pressure, gives off its heat in the condenser 20, for example to heating water, and condenses in the process
Implementation Method 5
the vaporized refrigerant is compressed by the heat pump's compressor and condensed in the heat pump's condenser... evaporates in the evaporator, absorbing ambient heat
Data Source
Figure 1~2
AI summary
An electronic expansion valve (80) is closed when a heating-pump device is inactive. It regulates overheating in an injected coolant when hot-gas temperatures are below a critical temperature. When hot-gas temperatures are in a range of a critical temperature, a partly liquid coolant is injected into a condenser (10) so that a defined maximum value is not reached in a hot-gas temperature. An independent claim is also included for a method for operating a heating-pump device.