Heat Pump Refrigerant Control for High-Pressure and Liquid Back
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat pump hot water supply systems face issues with increased equipment size and cost due to the need for a large refrigerant amount adjusting device, and without such a device, liquid back to the compressor can occur, leading to malfunction during restarts, especially when dealing with high-temperature water inflow, which can cause abnormal pressure increases and liquid compression.
Innovation Solution
A heat pump system with a refrigerant circuit including a compressor, condenser, expansion valve, and refrigerant amount adjusting device, along with a hot water tank and circulating pump, uses an inlet refrigerant temperature detection unit and inlet water temperature detection unit to adjust the expansion valve's opening degree, ensuring the refrigerant concentration on the high-pressure side does not exceed a fixed pressure, thereby storing excess refrigerant in the adjusting device and preventing liquid compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a refrigerant amount adjusting device is provided to control high-pressure side pressure and improve efficiency, then the coefficient of performance is improved, but the equipment size and cost increase
Solution Approach 1:
The system performs preliminary action by controlling the expansion valve opening degree in advance when high-temperature water inflow is detected, preventing abnormal pressure increase before it occurs. This proactive control eliminates the need for a large refrigerant amount adjusting device while maintaining efficient operation.
Solution Approach 2:
The system changes operational parameters by dynamically adjusting the expansion valve opening degree based on inlet water temperature conditions. This parameter adjustment optimizes refrigerant flow and pressure control, achieving efficient heat pump operation without requiring additional equipment.
2Weight of stationary object
If no refrigerant amount adjusting device is provided to reduce equipment size, then equipment cost is reduced, but liquid back to the compressor occurs causing malfunction during restart
Solution Approach 1:
The system performs preliminary action by controlling the expansion valve opening degree in advance when high-temperature water inflow is detected, preventing abnormal pressure increase before it occurs. This proactive control eliminates the need for a large refrigerant amount adjusting device while maintaining efficient operation.
Solution Approach 2:
The system uses feedback from inlet water temperature detection to continuously adjust the expansion valve opening degree. This closed-loop control ensures refrigerant pressure and flow are optimized in real-time, preventing liquid back to the compressor and ensuring reliable operation during restart.
3Device complexity
If the expansion valve opening degree is not adjusted for high-temperature water inflow, then device complexity is reduced, but abnormal pressure increase occurs on the high-pressure side
Solution Approach 1:
The system uses feedback from inlet water temperature detection to continuously adjust the expansion valve opening degree. This closed-loop control ensures refrigerant pressure and flow are optimized in real-time, preventing liquid back to the compressor and ensuring reliable operation during restart.
Solution Approach 2:
The system changes operational parameters by dynamically adjusting the expansion valve opening degree based on inlet water temperature conditions. This parameter adjustment optimizes refrigerant flow and pressure control, achieving efficient heat pump operation without requiring additional equipment.
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 configuration reduces equipment size and cost, ensures compressor reliability by avoiding liquid compression, and maintains reliable boiling operations regardless of environmental conditions, while reducing high-pressure suppression and enhancing the coefficient of performance (COP).
Implementation Method 1
adjusting a valve opening degree of an expansion valve (3) such that a difference between a hot water target temperature transmitted from a tank control unit (12) provided at the hot water tank (14) and an inlet refrigerant temperature is equal to a temperature difference set in advance
Implementation Method 2
the storage amount of liquid refrigerant in the refrigerant amount adjusting device at an outlet of the evaporator decreases. As the amount of refrigerant on the high-pressure side increases, the pressure increases and the capacity increases
Implementation Method 3
a condenser (2) that exchanges heat between refrigerant and water
Implementation Method 4
an evaporator (4) that exchanges heat between air and refrigerant
Implementation Method 5
a compressor (1) that compresses refrigerant and discharges the compressed refrigerant
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention is to reduce the maximum high pressure, as high-pressure suppression, by storing refrigerant in a refrigerant amount adjusting device at the time of inflow of water at high temperature and to avoid liquid compression by storing liquid back at the time of transition into the refrigerant amount adjusting device, thereby the reliability of a compressor being ensured. At the time of boiling, the opening degree of an expansion valve is adjusted such that a difference between a hot water target temperature and an inlet refrigerant temperature is equal to a temperature difference set in advance. When the temperature of fluid sent from a hot water tank to a condenser is high, the temperature difference is changed to adjust the valve opening degree of the expansion valve in an opening direction, so that concentration of refrigerant on a high-pressure side can be reduced and high-pressure suppression can thus be achieved. In contrast, concentration of refrigerant on a low-pressure side increases, and excess liquid refrigerant is thus stored in the refrigerant amount adjusting device. Furthermore, after an operation stops, in the case where restarting is performed immediately after liquid refrigerant is stored in the evaporator, if no refrigerant amount adjusting device is provided, liquid back to the compressor may occur, resulting in liquid compression. Thus, due to storage of refrigerant in the refrigerant amount adjusting device, liquid compression can be avoided, and the reliability of the compressor can thus be ensured.