Heat Exchanger Flow Control for Uniform Defrosting in Air Conditioners
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Solution Overview
Problem
In air-conditioning apparatuses, the defrosting capacity is not uniform throughout the heat exchanger, leading to a higher risk of frost remaining unmelted, especially in the lower part where air velocity is low, due to temperature imbalances caused by refrigerant flow patterns.
Innovation Solution
An air-conditioning apparatus with a heat medium circuit, temperature detecting units, and a flow regulating unit that adjusts the flow rate through heat exchange units based on detected temperature differences to ensure uniform defrosting capacity across the heat exchanger during defrosting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the propeller fan is installed in the upper part of the heat source unit, then the air velocity in the upper part of the heat exchanger is high, but the air velocity in the lower part is low, resulting in deteriorated air velocity balance and increased frost formation in the lower part
Solution Approach 1:
The patent applies local quality by installing air blowing devices at different locations (upper, middle, and lower parts) of the heat exchanger to create localized air flow enhancement. Each air blowing device targets a specific region to ensure uniform air velocity distribution across the entire heat exchanger surface, preventing frost accumulation in low-velocity areas while maintaining high heat exchange efficiency.
2Temperature
If the gas refrigerant enters the upper part of the heat exchanger first during defrosting operation, then the temperature in the upper part decreases, but the temperature in the lower part becomes below the required defrosting temperature, resulting in non-uniform defrosting capacity
Solution Approach 1:
The patent applies preliminary action by introducing a flow regulating unit that adjusts the heat medium flow rate to the first heat exchange unit before the defrosting process begins. This pre-adjustment ensures that the lower part of the heat exchanger receives sufficient heat medium flow to maintain defrosting temperature, preventing the temperature from dropping below the required level and ensuring uniform defrosting capacity across all regions.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the flow rate of the heat medium through the flow regulating unit based on temperature differences detected between different heat exchange units. This parameter adjustment optimizes the heat distribution during defrosting operation, ensuring that each region receives appropriate heat flow to maintain uniform defrosting capacity.
3Productivity
If the flow rate of heat medium through the first heat exchange unit is high, then the defrosting capacity in the upper part is sufficient, but the temperature difference between heat exchange units increases, resulting in non-uniform defrosting capacity
Solution Approach 1:
The patent applies feedback by using temperature detecting units to monitor the outlet temperatures of different heat exchange units and using this information to adjust the flow rate through the flow regulating unit. This closed-loop control ensures that the flow rate is optimized to maintain uniform temperature distribution and defrosting capacity across all heat exchange units, preventing excessive temperature differences.
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 ensures uniform defrosting capacity throughout the heat exchanger, preventing frost from remaining unmelted by adjusting the flow rate of the heat medium in response to temperature differences between heat exchange units, thereby improving defrosting efficiency.
Implementation Method 1
a first temperature detecting unit configured to detect an outlet temperature of the first heat exchange unit
Implementation Method 2
a second temperature detecting unit configured to detect an outlet temperature of the second heat exchange unit
Implementation Method 3
a heat medium circuit in which a compressor, a heat source-side heat exchanger including a first heat exchange unit and a second heat exchange unit connected to the first heat exchange unit, an expansion unit, and a use-side heat exchanger are connected by a pipe, and through which a heat medium flows
Data Source
AI summary
An air-conditioning apparatus includes a heat medium circuit in which a compressor, a flow switching unit, a flow regulating unit, a gas header, a heat source-side heat exchanger, a distributor, an expansion unit, and a use-side heat exchanger are connected by a pipe, and during a defrosting operation to defrost the heat source-side heat exchanger, heat medium circulates, in order, the compressor, the flow switching unit, the gas header, the heat source-side heat exchanger, the distributor, the expansion unit, and the use-side heat exchanger. The heat source-side heat exchanger includes a first heat exchange unit, and a second heat exchange unit provided lower than the first heat exchange unit. The flow regulating unit is configured to, during the defrosting operation, regulate a flow rate of heat medium flowing through the first heat exchange unit and a flow rate of heat medium flowing through the second heat exchange unit.