Heat Pump Water Heater Injection Circuit for Low-Temperature Heating
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Solution Overview
Problem
Conventional heat pump water heaters experience a decrease in heating and hot water supply ability at low ambient temperatures and have unstable refrigerant conditions and heat exchange performance due to varying load changes, especially in high-load scenarios.
Innovation Solution
A heat pump water heater outdoor unit with a compressor, water heat exchanger, air heat exchanger, first decompression device, and an injection circuit that injects refrigerant into the compressor, along with internal heat exchangers to stabilize refrigerant conditions and enhance heat exchange performance, using temperature and pressure sensors for control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a refrigerant is compressed to a predetermined pressure to ensure compressor reliability through overtemperature protection, then the compressor reliability is improved, but the operating ability (heating/hot water supply ability) decreases
Solution Approach 1:
A refrigerant injection valve is introduced as an intermediary device between the compressor suction port and the compressor cylinder. This valve controls the injection of refrigerant during the compression process, acting as a mediator to reduce discharge temperature while maintaining compression function. The injection valve enables precise control of refrigerant injection timing and amount, allowing the system to protect the compressor from overheating while preserving heating capability.
Solution Approach 2:
The system changes the physical parameters of the refrigerant by injecting it at specific points during the compression cycle. By controlling the injection timing, pressure, and temperature of the injected refrigerant, the system modifies the thermodynamic parameters of the compression process to reduce discharge temperature without sacrificing compression effectiveness or heating ability.
2Productivity
If the evaporation temperature of the evaporator decreases to provide high-temperature water supply mode at low temperatures, then the hot water supply ability is improved, but the discharge refrigerant temperature increases excessively
Solution Approach 1:
The refrigerant injection valve serves as an intermediary that introduces cooler refrigerant into the compression chamber during the compression process. This injected refrigerant acts as a thermal mediator, absorbing excess heat and reducing the discharge temperature even when the evaporator operates at low temperatures for high-temperature hot water supply mode.
Solution Approach 2:
The system employs periodic injection of refrigerant during specific phases of the compression cycle. By timing the refrigerant injection to occur during the compressing process rather than continuously, the system periodically reduces discharge temperature while maintaining the ability to supply high-temperature hot water when needed.
3Reliability
If the capacity (number of revolution) of the compressor is decreased to protect from overheating, then the compressor reliability is improved, but the operating ability decreases
Solution Approach 1:
Instead of reducing compressor capacity as the primary protection method, the system uses the refrigerant injection valve as an intermediary to actively manage discharge temperature. This allows the compressor to maintain its full capacity and operating ability while the injection valve mediates the thermal conditions to prevent overheating, thus preserving both reliability and productivity.
Solution Approach 2:
The system changes the thermal parameters of the compression process through refrigerant injection rather than changing the mechanical parameters (capacity, revolutions). By modifying the temperature and pressure parameters of the refrigerant during compression, the system protects the compressor while maintaining its full operating capacity and ability to meet heating demands.
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 maintains stable heating and hot water supply ability at low ambient temperatures, stabilizes refrigerant conditions in the water heat exchanger, and ensures high heat exchange performance even under varying loads, preventing a decrease in heating ability and optimizing the performance of both water and air heat exchangers.
Implementation Method 1
a first internal heat exchanger provided between the water heat exchanger and the first decompression device and used for exchanging heat between the refrigerant flowing between the water heat exchanger and the first decompression device and the refrigerant flowing between the air heat exchanger and the compressor
Implementation Method 2
a second internal heat exchanger for exchanging heat between the refrigerant flowing between the first internal heat exchanger and the first decompression device and the refrigerant flowing between the second decompression device and the compressor in the injection circuit
Implementation Method 3
a water heat exchanger for exchanging heat between water and a refrigerant
Implementation Method 4
an air heat exchanger for exchanging heat between air and the refrigerant
Data Source
AI summary
To provide a heat pump water heater outdoor unit and heat pump water heater capable of preventing reduction in heating/hot water supply ability even at a low ambient temperature. A heat pump water heater outdoor unit, in which a compressor, a water heat exchanger, a first expansion valve, and an air heat exchanger are connected with piping, includes a first internal heat exchanger provided between the water heat exchanger and the first expansion valve and used for heat exchange between a refrigerant flowing between the water heat exchanger and the first expansion valve and a refrigerant flowing between the air heat exchanger and the compressor, an injection circuit branching off at a point between the first internal heat exchanger and the first expansion valve and to inject the refrigerant into the compressor through a second expansion valve; and a second internal heat exchanger for heat exchange between the refrigerant flowing between the first internal heat exchanger and the first expansion valve and the refrigerant flowing between the second expansion valve and the compressor in the injection circuit.