Heat Pump Water Heater Outdoor Unit With Refrigerant Injection
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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
Incorporating an injection circuit into the compressor to manage refrigerant flow and pressure, with a control system that adjusts the operation of expansion valves and compressor capacity based on temperature and pressure sensors to maintain stable refrigerant conditions and optimize heat exchange in the water heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the evaporator temperature decreases at low ambient temperatures to supply high-temperature water, then the heating ability is improved, but the discharge refrigerant temperature increases excessively causing overtemperature protection and compressor capacity reduction
Solution Approach 1:
The suction refrigerant serves as an intermediary cooling medium. It is cooled by the evaporator from -15°C to -40°C, then used to cool the compression chamber during the compression process. This intermediary cooling prevents excessive discharge temperature without requiring direct compression of sub-zero refrigerant, resolving the contradiction between water heating capability and compressor reliability.
Solution Approach 2:
The suction refrigerant is pre-cooled by the evaporator before entering the compression chamber. This preliminary cooling action prepares the refrigerant to absorb heat during compression, preventing overheating before it occurs. The compression chamber is also pre-cooled by circulating the pre-cooled suction refrigerant, establishing favorable thermal conditions in advance.
2Temperature
If the compressor capacity is reduced due to overtemperature protection, then the discharge refrigerant temperature is controlled, but the heating and hot water supply ability decreases
Solution Approach 1:
The suction refrigerant acts as a heat transfer intermediary within the compression process. By circulating this pre-cooled refrigerant through the compression chamber, it absorbs compression heat internally, allowing the compressor to maintain full capacity while controlling discharge temperature through the intermediary's heat absorption rather than reducing compressor output.
3Temperature
If a conventional injection circuit is added to control refrigerant flow, then the discharge temperature is controlled, but the device complexity increases
Solution Approach 1:
The suction refrigerant circulation system serves multiple functions simultaneously: it cools the evaporator, pre-cools the compression chamber, and acts as an intermediary cooling medium during compression. This multi-functionality eliminates the need for separate injection circuits, reducing device complexity while achieving temperature control.
Solution Approach 2:
The suction refrigerant serves itself by circulating through the compression chamber and absorbing compression heat. The system uses its own refrigerant rather than requiring external injection circuits or additional cooling media. The refrigerant self-regulates the compression chamber temperature through its natural circulation and heat absorption properties.
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 ensures consistent heating and hot water supply ability across varying loads and ambient temperatures, stabilizing refrigerant conditions and enhancing heat exchange performance, even in high-load situations, by controlling the refrigerant flow and pressure within the heat pump water heater outdoor unit.
Implementation Method 1
an evaporation temperature of an evaporator decreases
Implementation Method 2
A heat pump utilizing heat energy in air
Implementation Method 3
a refrigerant is compressed to a predetermined pressure, a temperature of the refrigerant discharged from a compressor increases
Implementation Method 4
as a mechanism for injecting a refrigerant during a compressing process of a compressor
Implementation Method 5
a heating/hot water supply ability of the water heater or a heating ability of the air conditioner
Data Source
Figure 1~2
Figure 3
AI summary
To provide a heat pump water heater outdoor unit (100) 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 (3), a water heat exchanger (2), a first expansion valve (7), and an air heat exchanger (1) are connected with piping, includes a first internal heat exchanger (9) 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 (13) 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 (8); and a second internal heat exchanger (10) 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.