Outdoor Heat Exchanger Control Under Variable Wind and Rain
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Solution Overview
Problem
Conventional air-conditioning systems face challenges in precisely controlling the heat exchange amount due to variations in refrigerant flow rate and external factors like wind or rain, leading to inefficiencies and increased complexity in heat exchanger design.
Innovation Solution
An air-conditioning apparatus with a refrigerant circuit that includes a compressor, expansion means, and a heat exchanger, equipped with controllers to adjust the tube-outside and tube-inside heat transfer coefficients and heat transfer area, allowing for continuous control of the heat exchange amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flow rate of the refrigerant through the heat exchanger is reduced, then a variation in heat exchange amount will be reduced in the control of the heat transfer coefficient of the outside of the heat transfer tube, but the heat exchange amount will fail to be reduced when the fan is operating at the lower limit air flow rate due to external factors like wind or rain
Solution Approach 1:
The invention changes the control parameter from only air flow rate to a combination of refrigerant flow rate and air flow rate. By adjusting the refrigerant flow rate through the heat exchanger, the system can compensate for external factors like wind or rain that affect heat exchange, thereby maintaining reliable control adaptability under various operating conditions.
2Reliability
If flow rate changing means changes the refrigerant passage in the heat exchanger to cause a stepwise change in heat transfer area of the inside of a heat transfer tube, then the heat exchange amount can be controlled, but this results in an increased cost and a complicated shape of the heat exchanger
Solution Approach 1:
The heat exchanger is divided into multiple independent heat exchange sections, each with its own refrigerant passage. By selectively opening or closing solenoid valves for each section, the system can stepwise adjust the heat transfer area without requiring complex internal flow path changes within a single heat exchanger, thus maintaining structural simplicity while achieving control capability.
Solution Approach 2:
The solenoid valves serve multiple functions: they control refrigerant flow to individual heat exchange sections for capacity control, and can be combined to provide stepwise adjustment of heat transfer area. This multi-functionality eliminates the need for separate mechanisms, reducing overall system complexity and cost.
3Manufacturing precision
If the flow rate of the refrigerant through the heat exchanger is reduced, then a variation in heat exchange amount will be reduced, but many changing means are required if the heat exchange amount has to be continuously controlled
Solution Approach 1:
The system uses dynamically controllable solenoid valves that can be opened or closed in various combinations to continuously adjust the heat exchange amount. This dynamic control approach replaces the need for multiple fixed changing means, achieving continuous control precision with fewer physical components.
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
Enables precise control of the heat exchange amount, maintaining efficiency even under varying conditions, and reduces the complexity and cost associated with traditional methods.
Implementation Method 1
a heat exchanger which includes a heat transfer tube through which a refrigerant flows and a heat transfer coefficient of an outside of the heat transfer tube
Implementation Method 2
the coefficient of heat transfer (hereinafter, 'heat transfer coefficient') of the outside of a heat transfer tube, thus controlling the heat exchange amount
Data Source
AI summary
An outdoor heat exchanger includes a fan configured to adjust a heat transfer coefficient ao of the outside of a heat transfer tube through which a refrigerant flows, a bypass passage and flow rate control valve configured to adjust a heat transfer coefficient αi of the inside of the heat transfer tube through which the refrigerant flows, and an on-off valve configured to adjust a heat transfer area A where the refrigerant exchanges heat with a heat medium. A controller controls the heat transfer coefficient αo of the outside of the heat transfer tube, the heat transfer coefficient αi of the inside thereof, and the heat transfer area A to control a heat exchange amount of the outdoor heat exchanger.