Intermediate Heat Exchanger Control for Partial-Load Air Conditioning
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Solution Overview
Problem
Existing air-conditioning apparatuses face issues with excessive air conditioning capacity during reduced loads, leading to uncomfortable temperature fluctuations and increased energy consumption due to constant control target values for indoor-unit inlet-outlet temperature differences, which result in inefficient heat transfer and start-stop losses.
Innovation Solution
An air-conditioning apparatus with a controller that adjusts the target heat medium temperature difference for intermediate heat exchangers, allowing them to dynamically control the flow rate of the heat medium based on detected temperature deviations, ensuring optimal temperature efficiency and preventing excessive capacity during partial load operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant control target value for indoor-unit inlet-outlet temperature difference is used, then the control system is simple and easy to operate, but excessive air conditioning capacity occurs during reduced loads causing uncomfortable temperature fluctuations and start-stop losses
Solution Approach 1:
The control target value for indoor-unit inlet-outlet temperature difference is changed from a constant value to a dynamic value that varies according to the operating conditions. Specifically, when the number of operating indoor units is small (reduced load), a different control target value is applied compared to when many units operate (full load), thereby adapting the control strategy to match the actual system state and preventing excessive capacity and temperature fluctuations
Solution Approach 2:
The control target value parameter is modified based on the operating load conditions. By detecting the number of operating indoor units and adjusting the control target value accordingly (using different thresholds for different load scenarios), the system optimizes the temperature difference control to match the actual heat demand, avoiding both overheating and start-stop cycles
2Use of energy by moving object
If the flow rate of heat medium is reduced during partial load operation, then energy consumption decreases, but the temperature efficiency ratio of the intermediate heat exchanger increases causing excessive temperature rise
Solution Approach 1:
The system continuously monitors the actual indoor-unit inlet-outlet temperature difference and compares it with the dynamic control target value. Based on this feedback, the flow rate of the heat medium through the intermediate heat exchanger is adjusted to maintain the temperature difference within the desired range, preventing both energy waste and excessive temperature rise
Solution Approach 2:
The control target value for temperature difference is dynamically adjusted based on the number of operating indoor units. During partial load operation, an appropriate control target value is selected that accounts for the reduced heat demand, allowing the system to optimize the heat medium flow rate to achieve energy savings while maintaining acceptable temperature efficiency
3Device complexity
If a single control target value is used for all operating conditions, then the control logic is simple, but the system cannot adapt to varying heat loads across different numbers of operating indoor units
Solution Approach 1:
The control target value is segmented into multiple discrete values corresponding to different operating scenarios (e.g., one value when one indoor unit operates, another value when multiple units operate). This segmentation allows the system to adapt to varying heat loads without requiring complex continuous control algorithms, maintaining relative simplicity while improving adaptability
Solution Approach 2:
The control system transitions from a static single target value to a dynamic multi-value target structure that automatically selects the appropriate control target based on the detected number of operating indoor units. This dynamic adaptation enables the system to respond appropriately to different load conditions while keeping the control logic manageable through predefined thresholds
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 solution prevents excessive temperature fluctuations, maintains user comfort, and reduces energy consumption by dynamically adjusting the heat medium flow rate, thereby minimizing start-stop losses and enhancing the efficiency of the air-conditioning system.
Implementation Method 1
an intermediate heat exchanger is allowed to exchange heat between a refrigerant heated or cooled on a heat source side and a heat medium flowing through a use side circuit such that heat energy produced on the heat source side is transmitted to a use side heat exchanger
Data Source
AI summary
An air-conditioning apparatus includes a intermediate heat exchangers operating as a condenser or an evaporator and allows each intermediate heat exchanger to exchange heat between a refrigerant heated or cooled in a refrigeration cycle on a heat source side and a heat transfer medium flowing through a heat transfer medium circuit on a use side such that heat energy produced on the heat source side is transmitted to use side heat exchangers. A controller calculates the heat transfer medium temperature difference between a heat transfer medium inlet and outlet temperatures. When a detected value of a heat transfer medium temperature detecting device deviates from a predetermined range, the controller changes the target heat transfer medium temperature difference and controls a heat transfer medium flow control device, such that the heat transfer medium temperature difference reaches the changed target heat transfer medium temperature difference.