Outdoor unit, refrigeration cycle device, and refrigerating machine
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Solution Overview
Problem
Refrigeration cycle apparatuses using CO2 as a refrigerant face challenges with high evaporation temperatures leading to high intermediate pressures, making it difficult to ensure subcooling and maintain refrigeration capability, especially when using load devices designed for lower pressures, which increases system costs.
Innovation Solution
An outdoor unit with a compressor, condenser, heat exchanger, and second expansion valve, along with a flow path switching unit and third expansion valve, controls the refrigerant flow to ensure subcooling at the load device inlet, even at high evaporation temperatures, by selectively routing refrigerant to the suction or intermediate pressure port based on temperature thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CO2 refrigeration cycle apparatus is used with high evaporation temperature, then the system can operate in summer high temperature conditions, but the intermediate pressure becomes high making it difficult to ensure subcooling
Solution Approach 1:
The patent segments the refrigerant flow path into multiple branches: a main flow path through the heat exchanger and a bypass flow path through the subcooling heat exchanger. This segmentation allows selective routing of refrigerant to ensure subcooling even at high evaporation temperatures where intermediate pressure would otherwise be too high.
Solution Approach 2:
The subcooling heat exchanger acts as an intermediary device that receives refrigerant from the high-pressure side and cools it using heat exchange with the suction-side refrigerant flow, thereby ensuring subcooling before the refrigerant reaches the expansion valve regardless of intermediate pressure conditions.
2Ease of manufacture
If decompression is performed at expansion valve in liquid pipe, then the load device can be used unchanged for cost reduction, but gas refrigerant mixing into liquid refrigerant significantly decreases expansion valve flow rate
Solution Approach 1:
The patent performs preliminary subcooling of the liquid refrigerant in the subcooling heat exchanger before it reaches the expansion valve. This preliminary action ensures that the refrigerant is fully liquid and properly subcooled, preventing gas refrigerant from mixing into the liquid flow and maintaining expansion valve flow rate.
Solution Approach 2:
The subcooling heat exchanger serves as an intermediary between the high-pressure liquid refrigerant and the expansion valve, ensuring proper subcooling and preventing gas-liquid mixing that would degrade expansion valve performance.
3Temperature
If intermediate pressure injection circuit with internal heat exchanger is adopted, then subcool can be increased, but when evaporation temperature is high the intermediate pressure is also high making it difficult to ensure subcool
Solution Approach 1:
The subcooling heat exchanger acts as an intermediary that enables subcooling by utilizing heat exchange between high-pressure liquid refrigerant and low-pressure suction-side refrigerant, bypassing the limitation of intermediate pressure that constrains traditional internal heat exchanger approaches.
Solution Approach 2:
The patent changes the operational parameters by routing refrigerant through the subcooling heat exchanger where heat transfer occurs between different pressure levels, enabling subcooling to be achieved independently of the intermediate pressure constraints that limit conventional internal heat exchanger effectiveness.
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 ensures subcooling of the refrigerant at the load device inlet, preventing capability degradation and allowing the use of conventional load devices, thereby reducing system costs by maintaining the design pressure within manageable limits.
Implementation Method 1
The heat exchanger has a first passage and a second passage, and is configured to exchange heat between refrigerant flowing in the first passage and the refrigerant flowing in the second passage
Implementation Method 2
a third expansion valve disposed on the first refrigerant flow path
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An outdoor unit (2) includes a compressor (10), a condenser (20), a heat exchanger (30) configured to exchange heat between refrigerant flowing in a first passage (HI) and the refrigerant flowing in a second passage (H2), and a second expansion valve (40). The outdoor unit (2) further includes a first refrigerant flow path (91 to 94) configured to cause the refrigerant to flow from a portion of a circulation flow path between an outlet of the first passage (HI) and the second expansion valve (40) to an inlet of the second passage (H2), a second refrigerant flow path (96 to 98) configured to cause the refrigerant to flow from an outlet of the second passage (H2) to a suction port (G1) or an intermediate pressure port (G3) of the compressor (10), and a flow path switching unit (74) disposed on the second refrigerant flow path and configured to switch, to one of the suction port (G1) and the intermediate pressure port (G3), a destination of the refrigerant flowing out from the outlet of the second passage (H2).