Multi-Row CO2 Heat Exchanger Layout for Stable Temperature Difference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional air conditioners using CO2 refrigerant struggle to achieve maximum heat exchange efficiency due to limited rows of heat transfer tubes, which hinder effective heat transfer when refrigerant temperature varies significantly.
Innovation Solution
The indoor unit incorporates a heat exchanger with multiple rows of heat transfer tubes crossing the airflow direction, divided plate fins to suppress heat transfer on the surface, and optimized passage lengths to maintain temperature differences, along with CO2 as the refrigerant to enhance heat exchange performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only two or three rows of heat transfer tubes are formed in the flow direction of the airflow, then the device complexity is reduced, but the heat exchange efficiency cannot be maximized when refrigerant temperature greatly varies
Solution Approach 1:
The heat exchanger is segmented into multiple rows of heat transfer tubes (four or more rows) arranged in the airflow direction, with each row serving distinct heat exchange functions. This segmentation allows the system to handle varying refrigerant temperatures more effectively by providing multiple stages of heat transfer, thereby resolving the contradiction between device complexity and heat exchange efficiency.
Solution Approach 2:
Different rows of heat transfer tubes are positioned to interact with airflow at different locations, creating local quality variations in heat exchange intensity. The first row handles initial heat exchange, while subsequent rows handle progressively different temperature differentials, optimizing overall heat exchange efficiency without requiring excessive complexity.
2Ease of manufacture
If plate fins are not divided between adjacent rows, then the manufacturing process is simplified, but heat transfer on the plate fin surface is excessive causing temperature difference to decrease
Solution Approach 1:
Each plate fin is divided into multiple sections between adjacent rows of heat transfer tubes, creating thermal zones that prevent excessive heat transfer across the entire plate fin surface. This segmentation maintains temperature differences more effectively while keeping the manufacturing process relatively simple through standardized division patterns.
Solution Approach 2:
The plate fins have different thermal characteristics in different regions - divided sections between rows create local thermal barriers that control heat transfer rates. This local quality variation ensures appropriate temperature differences are maintained where needed while allowing efficient heat transfer in other areas.
3Area of stationary object
If heat transfer tubes extend in longer dimensions, then the heat exchange area is increased, but the distance refrigerant moves in the long axis direction increases causing temperature difference to decrease
Solution Approach 1:
Instead of extending heat transfer tubes primarily in one long dimension, the design uses multiple rows of tubes arranged in the airflow direction, distributing the heat exchange area across different spatial dimensions. This approach increases total heat exchange area while keeping the refrigerant flow path length manageable, thereby maintaining temperature differences.
Solution Approach 2:
The heat exchange function is distributed across multiple rows rather than concentrated in single long tubes. Each row provides localized heat exchange with optimized tube lengths, ensuring that refrigerant maintains appropriate temperature differences throughout its flow path while achieving sufficient total heat exchange area.
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 improves heat exchange efficiency by increasing the amount of heat exchanged with airflow, reducing processing costs, and ensuring environmental sustainability with low ozone destruction.
Implementation Method 1
heat transfer tubes... allow supercritical refrigerant to radiate heat to the air
Implementation Method 2
airflow exchanges heat with higher temperature refrigerant as the airflow moves downstream
Implementation Method 3
heat exchanger that allows supercritical refrigerant to radiate heat to the air
Implementation Method 4
each plate fin is divided, heat transfer on the plate fin surface is suppressed, and the difference in temperature between the refrigerant and the air is appropriately maintained
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
A heat exchanger with improved heat exchange performance is provided. An indoor heat exchanger (6) is a heat exchanger that allows supercritical CO2 refrigerant to radiate heat to the air, and includes a plurality of plate fins (11) and a plurality of heat transfer tubes (12). Four or more rows (61 to 72) of heat transfer tubes (12) arranged in the direction crossing the airflow are formed in the upstream-to-downstream direction of the airflow. Each plate fin (11) is divided between at least one pair of adjacent rows (61, 62). The refrigerant flows from the heat transfer tubes (12) in the row (72) on the downstream side of the airflow to the heat transfer tubes (12) in the row (61) on the upstream side of the airflow.