Heat Medium Flow Reversal in Air Conditioning Heat Exchangers
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Solution Overview
Problem
Conventional air-conditioning apparatuses for office buildings face issues such as refrigerant leakage into indoor spaces, high energy consumption due to long heat medium circulation paths, complex and costly installations, and reduced heat exchange efficiency with zeotropic refrigerant mixtures, leading to increased energy waste and installation challenges.
Innovation Solution
An air-conditioning apparatus with a heat medium relay unit connected to both the outdoor and indoor units via reduced piping, utilizing a refrigerant circuit and heat medium circuit design that allows for efficient heat transfer and energy management, including a heat medium flow reversing device to optimize heat exchange and reduce refrigerant circulation within indoor units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant is circulated from outdoor unit to indoor units, then cooling and heating operations can be performed, but refrigerant leakage into indoor space occurs
Solution Approach 1:
The system is divided into two separate circulation loops: a refrigerant loop confined to the outdoor unit, and a heat medium loop that connects to indoor units. This segmentation prevents refrigerant from entering indoor spaces while maintaining the cooling and heating functions through the heat medium intermediary.
Solution Approach 2:
A heat medium (water or antifreeze solution) is introduced as an intermediary substance between the refrigerant and the indoor units. The refrigerant heats or cools the heat medium in the outdoor unit, and the heat medium then transports thermal energy to indoor units without containing refrigerant, thereby eliminating leakage risk.
2Reliability
If heat medium circulation path is made long to connect outdoor unit to indoor units, then cooling and heating can be performed in indoor units, but energy consumption for conveyance power increases
Solution Approach 1:
The system dynamically adjusts the circulation path of the heat medium based on operational requirements. By providing multiple circulation paths with different lengths and allowing selective activation, the system optimizes conveyance distance and reduces energy consumption while ensuring cooling and heating operations can be performed.
Solution Approach 2:
The system changes operational parameters by selectively activating different circulation paths based on load requirements and distance. This allows the system to adapt the heat medium circulation path length to minimize conveyance power consumption while maintaining the necessary cooling and heating capacity.
3Adaptability or versatility
If four water pipes are arranged between outdoor unit and indoor units for heat recovery chiller, then cooling or heating can be freely selected, but installation becomes complex
Solution Approach 1:
The outdoor unit is designed with multi-functional capability to provide both cooling and heating operations through a unified system architecture. By integrating heat recovery functionality and providing selective circulation paths, the system achieves versatility without requiring separate four-pipe configurations for each function, simplifying installation.
Solution Approach 2:
The complex four-pipe configuration is extracted and replaced by a simplified piping arrangement that utilizes the heat medium circulation paths. The system separates the thermal processing functions (cooling/heating) from the fluid transport complexity, achieving versatility through control logic rather than physical pipe complexity.
4Ease of operation
If heat exchanger for primary refrigerant and secondary refrigerant is disposed near each indoor unit, then secondary refrigerant can be conveyed to indoor units, but refrigerant leakage risk remains
Solution Approach 1:
The system segments the refrigerant containment to exclusively the outdoor unit, separating it from indoor unit installations. Heat exchangers near indoor units handle only heat medium, not refrigerant, thereby maintaining ease of operation for thermal exchange while eliminating refrigerant leakage risk in occupied spaces.
Solution Approach 2:
The heat medium serves as an intermediary that enables thermal exchange near indoor units without introducing refrigerant into those locations. The refrigerant remains confined to the outdoor unit where it heats or cools the heat medium, which then performs the thermal function near indoor units safely.
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 design reduces energy consumption, minimizes refrigerant leakage, simplifies installation by reducing piping complexity, and enhances heat transfer efficiency, thereby improving safety and energy efficiency while accommodating zeotropic refrigerant mixtures effectively.
Implementation Method 1
Water, antifreeze, or the like is heated or cooled by a heat exchanger disposed in an outdoor unit
Implementation Method 2
a conditioned space is cooled with air that has been cooled by a refrigerant removing heat from air
Implementation Method 3
heated with air that has been heated by the refrigerant transferring its heat
Data Source
Figure 1
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Figure 3
AI summary
Provided is an air-conditioning apparatus that improves heat transfer efficiency in a heat exchanger 15 related to heat medium. In an air-conditioning apparatus 100, a heat medium circuit B is provided with a heat medium flow reversing device 20 that can switch the flow direction of a heat medium in the heat medium side passage of the heat exchanger 15 related to heat medium.