Heat Pump Water Heater Defrost Control for Compressor Durability
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Solution Overview
Problem
Conventional heat pump water heaters face reduced compressor durability during defrost operations due to the presence of liquid refrigerant in a gas-liquid two-phase state, leading to potential liquid lock and operational issues.
Innovation Solution
A heat pump water heater with a controller that selects between two defrost operations based on tank temperature and ambient conditions, adjusting the refrigerant circuit flow to prevent liquid refrigerant suction into the compressor, thereby maintaining compressor durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant circuit is configured to flow through the evaporator, decompressor, radiator and four-way valve during defrost operation, then the defrost operation can be performed, but liquid refrigerant may be sucked into the compressor reducing its durability
Solution Approach 1:
The patent applies dynamics by making the refrigerant circuit configuration changeable based on operating conditions. The controller dynamically switches between first and second defrost operations depending on whether liquid refrigerant is present in the circuit, allowing the system to adapt its refrigerant flow path to prevent liquid suction into the compressor while maintaining effective defrosting capability
Solution Approach 2:
The patent changes the refrigerant flow path parameters during defrost operation. By switching the four-way valve configuration between two different patterns (first defrost operation vs. second defrost operation), the system modifies the sequence and direction of refrigerant flow through various components to ensure liquid-free operation during defrosting
2Temperature
If the tank temperature increases during heating operation, then the water heating efficiency is improved, but the amount of liquid refrigerant in the circuit increases causing potential compressor damage
Solution Approach 1:
The patent implements feedback control by monitoring tank temperature during heating operation and using this information to determine the appropriate defrost operation mode. The controller continuously adjusts the refrigerant circuit configuration based on the current tank temperature state, preventing excessive liquid refrigerant accumulation that could damage the compressor while maintaining effective water heating
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 solution effectively prevents liquid refrigerant suction into the compressor during defrost operations, enhancing compressor durability and reducing the risk of liquid lock, thus improving the overall performance and longevity of the heat pump water heater.
Implementation Method 1
a tank for storing water heated by the radiator
Implementation Method 2
defrost operation to melt the frost on the evaporator
Implementation Method 3
a compressor for compressing a refrigerant
Implementation Method 4
a decompressor for decompressing the refrigerant
Data Source
Figure 1~2
Figure 3~4
AI summary
A heat pump water heater according to the present disclosure has a radiator located on the periphery of a tank. A refrigerant circuit is configured such that, when heating operation is performed, a refrigerant flows in sequence through a compressor, a four-way valve, a radiator, a decompressor, an evaporator and the four-way valve. When defrost operation to melt frost on the evaporator is performed, a controller selects and performs either a first defrost operation or a second defrost operation based on a state of the refrigerant in the refrigerant circuit from the outlet of the radiator to the suction side of the compressor through the decompressor, the evaporator and the four-way valve during the heating operation. Thus, a heat pump water heater that performs defrost operation with improved durability of a compressor can be provided.