Heat Medium Flow Control in Concurrent Cooling-Heating HVAC
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Solution Overview
Problem
Conventional air-conditioning apparatuses face challenges in maintaining stable operation and energy efficiency during concurrent cooling and heating operations, particularly due to the need for varying compressor ratios and heat exchanger capacities, which leads to frequent start-stop cycles and increased energy consumption.
Innovation Solution
An air-conditioning apparatus with a compressor, heat source unit side heat exchanger, and use-side heat exchangers, featuring a relay unit and a heat medium system that controls the flow rate of the heat medium based on the temperature difference and capacity of the use-side heat exchangers, allowing for efficient cooling and heating operations by adjusting the refrigerant flow and heat medium supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the AK value of the heat exchanger is decreased to match low cooling capacity, then the cooling capacity matches the heating capacity, but the air quantity of the outdoor fan must be reduced below the level required to cool the electronic board
Solution Approach 1:
The patent divides the heat exchanger into multiple independent heat exchange sections, each with adjustable heat transfer area. This allows selective reduction of heat transfer area in specific sections while maintaining adequate heat exchange in other sections, enabling the AK value to be decreased for capacity matching without completely reducing air quantity below the threshold needed for electronic board cooling.
Solution Approach 2:
The patent employs dynamic adjustment of the heat exchanger's heat transfer area through movable partitions or adjustable fins, allowing the AK value to be dynamically decreased to match cooling capacity requirements while maintaining minimum air quantity flow for electronic board cooling. The system can adapt the heat exchange capacity in real-time based on operational demands.
2Quantity of substance
If the AK value is decreased to achieve capacity matching, then the heat exchange amount decreases, but the air quantity reduction causes low pressure in the refrigeration cycle and prevents indoor units from operating
Solution Approach 1:
By segmenting the heat exchanger into multiple adjustable sections, the patent allows selective reduction of heat transfer area while maintaining sufficient air quantity flow through the heat exchanger. This segmentation enables the system to decrease the AK value for capacity matching without reducing air quantity below the level that would cause low pressure and indoor unit shutdown.
Solution Approach 2:
The patent changes the heat transfer area parameter of the heat exchanger independently from the air quantity parameter. This allows the AK value to be adjusted to match cooling capacity while maintaining air quantity at levels sufficient to prevent low pressure conditions and ensure continuous indoor unit operation.
3Quantity of substance
If the heat dissipation amount is reduced to approach zero for improved comfortability, then the cooling load is matched, but the AK value cannot be decreased sufficiently due to electronic board cooling requirements
Solution Approach 1:
The patent segments the heat exchanger into multiple independently controllable sections, allowing the heat dissipation amount to be reduced by adjusting specific sections while maintaining adequate heat transfer area in other sections for electronic board cooling. This segmentation provides precise control over heat dissipation without requiring complex system-wide adjustments.
Solution Approach 2:
The patent applies local quality adjustment by modifying the heat transfer area in specific local sections of the heat exchanger rather than uniformly across the entire heat exchanger. This allows the heat dissipation amount to be locally reduced to match cooling load while maintaining sufficient heat transfer area in other local sections for electronic board cooling, avoiding the need for complex global control.
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 enables stable and efficient cooling and heating operations, reducing power consumption and maintaining comfortability by dynamically adjusting the heat medium flow rate according to the thermal demands of the system.
Implementation Method 1
a heat source unit side heat exchanger that exchanges heat between the refrigerant and a heat medium different from the refrigerant
Implementation Method 2
use-side heat exchangers that exchange heat between the refrigerant and a usage medium near the refrigerant
Implementation Method 3
a compressor that compresses and discharges refrigerant
Data Source
AI summary
An air-conditioning apparatus includes a heat medium system configured to control a flow rate of the heat medium supplied to the heat source unit side heat exchanger that exchanges heat between refrigerant and the heat medium, the heat medium system having at least one system of a heat medium conveyor, a heat medium flow rate adjuster, and a heat medium flow rate control device. In the air-conditioning apparatus, the operation of each of use-side heat exchangers is changed to a cooling operation or a heating operation in accordance with a control command, and a cooling and heating concurrent operation is performed. The refrigerant is caused to flow through the heat source unit side heat exchanger in accordance with the ratio of the total cooling capacity of the use-side heat exchangers to the total heating capacity of the use-side heat exchangers. The heat medium flow rate control device controls the flow rate of the heat medium supplied to the heat source unit side heat exchanger, using the temperature of the heat medium flowing into the heat source unit side heat exchanger and the temperature of the heat medium flowing from the heat source unit side heat exchanger.