CO2 Refrigeration Cycle Bypass Control for Stronger Defrosting
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Solution Overview
Problem
Conventional air-conditioning apparatuses using carbon dioxide as a refrigerant face inefficiencies due to high temperature differences between the refrigerant and water or air in heat exchangers, leading to increased heat radiation loss and reduced defrosting capacity, especially when operating in supercritical ranges.
Innovation Solution
The refrigeration apparatus incorporates an intercooler bypass tube and a second-stage injection tube to control refrigerant flow, preventing heat radiation and maintaining high refrigerant temperature, while using an economizer heat exchanger to enhance refrigerant flow rates and reduce frost formation, thereby improving operating efficiency and defrosting capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If refrigerant is cooled in the outdoor heat exchanger to reduce temperature difference, then heat radiation loss decreases, but defrosting capacity is reduced
Solution Approach 1:
The outdoor heat exchanger is divided into two functional zones: an upper section that serves as a cooler to reduce heat radiation loss, and a lower section that serves as a defroster to maintain defrosting capacity. This segmentation allows each zone to perform its specific function optimally without interfering with the other.
Solution Approach 2:
A bypass tube with a bypass valve is introduced as an intermediary component to control refrigerant flow distribution. The bypass tube allows refrigerant to be directed either through the upper cooler section or through the lower defroster section, enabling flexible flow management to balance cooling efficiency and defrosting capacity.
2Loss of energy
If refrigerant flow rate through the outdoor heat exchanger is increased to improve cooling, then heat radiation loss decreases, but frost formation increases
Solution Approach 1:
The bypass valve is made dynamically controllable to adjust refrigerant flow distribution in real-time. Based on operating conditions such as temperature and humidity, the valve dynamically regulates the proportion of refrigerant flowing through the upper cooler section versus the lower defroster section, adapting to changing environmental conditions to prevent frost while maintaining cooling efficiency.
Solution Approach 2:
Different sections of the outdoor heat exchanger are assigned different functional qualities: the upper section is optimized for cooling with higher refrigerant flow to minimize heat radiation loss, while the lower section is optimized for defrosting with controlled refrigerant flow to prevent frost formation. Each section has tailored local characteristics suited to its specific function.
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 minimizes heat radiation loss, maintains high refrigerant temperature, and enhances defrosting capacity by optimizing refrigerant flow rates, addressing inefficiencies and frost-related issues in supercritical operation.
Implementation Method 1
The intercooler is a heat exchanger integrated with the heat source-side heat exchanger and having air as a heat source, is provided to an intermediate refrigerant tube for drawing refrigerant discharged from the first-stage compression element into the second-stage compression element, and functions as a cooler of the refrigerant discharged from the first-stage compression element and drawn into the second-stage compression element
Implementation Method 2
The heat source-side heat exchanger is a heat exchanger having air as a heat source
Implementation Method 3
an expansion mechanism for depressurizing the refrigerant
Implementation Method 4
The compression mechanism has a plurality of compression elements, and is configured so that refrigerant discharged from a first-stage compression element, which is one of a plurality of compression elements, is sequentially compressed by a second-stage compression element
Data Source
AI summary
A refrigeration apparatus uses a refrigerant that operates in a supercritical range. The refrigeration apparatus includes a compression mechanism, a heat source-side heat exchanger, an expansion mechanism, a usage-side heat exchanger, a switching mechanism, an intercooler, a bypass tube, and an injection tube. The switching mechanism is configured to switch between cooling and heating operation states. When the switching mechanism is switched to the cooling operation state to allow refrigerant to flow to the heat source-side heat exchanger and a reverse cycle defrosting operation for defrosting the heat source-side heat exchanger is performed, the refrigerant is caused to flow to the heat source-side heat exchanger, the intercooler and the injection tube. After the defrosting of the intercooler is detected as being complete, the bypass tube is used so as to ensure that the refrigerant does not flow to the intercooler and the injection valve is controlled so that the opening degree is increased.