Heat-Medium Air Conditioning With Zeotropic Anti-Freezing Control
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Solution Overview
Problem
Conventional air-conditioning systems for buildings face issues such as energy inefficiency, refrigerant leakage risks, and complex construction due to long circulation paths and the use of zeotropic refrigerant mixtures, which can cause heat medium freezing and increased energy consumption.
Innovation Solution
An air-conditioning apparatus with a refrigerant circuit and a heat medium circuit that uses a zeotropic refrigerant mixture with a saturated liquid temperature lower than the saturated gas temperature, incorporating a heat exchanger and anti-freezing control to prevent heat medium freezing, and reduces the number of connecting pipes between units, enhancing safety and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heat medium circulation system is used to avoid refrigerant leakage, then safety is improved, but the circulation path becomes long and energy consumption increases
Solution Approach 1:
The system divides the heat transfer function into two separate circuits: a refrigerant circuit confined to the outdoor unit and a heat medium circuit distributed to indoor units. This segmentation allows the refrigerant to remain in a controlled location while heat medium serves multiple indoor units, thus maintaining safety without excessive circulation path length.
Solution Approach 2:
The patent introduces a heat medium (water or antifreeze solution) as an intermediary substance that carries thermal energy from the outdoor unit to indoor units. This intermediary allows heat transfer without requiring refrigerant circulation through indoor spaces, thereby improving safety while managing energy consumption through optimized heat medium circulation paths.
2Adaptability or versatility
If four water pipes are arranged to allow simultaneous cooling and heating selection, then versatility is improved, but construction complexity increases
Solution Approach 1:
The outdoor unit's heat exchanger serves multiple functions: it acts as a condenser during cooling mode and as an evaporator during heating mode. The same heat medium circulation system supports both cooling and heating operations, eliminating the need for separate dedicated pipe systems for each function and simplifying construction.
3Productivity
If zeotropic refrigerant mixture is used, then refrigerant performance is improved, but heat medium freezing risk increases
Solution Approach 1:
The system incorporates temperature detection means in the heat medium circulation system to continuously monitor heat medium temperature. When the temperature approaches the freezing point, the control system activates anti-freezing measures such as heating elements or adjusting refrigerant flow, thereby preventing heat medium freezing while maintaining zeotropic refrigerant performance.
4Productivity
If refrigerant is circulated to indoor units, then cooling and heating efficiency is improved, but refrigerant leakage risk increases
Solution Approach 1:
The patent extracts the refrigerant from the indoor unit circulation system and confines it entirely within the outdoor unit. The outdoor unit performs all refrigerant compression, heat exchange, and circulation control functions, while indoor units receive only heat medium through which thermal energy is transferred. This extraction eliminates refrigerant leakage risks in indoor spaces while maintaining system efficiency.
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 reduces energy consumption, minimizes refrigerant leakage risks, and prevents heat medium freezing, thereby increasing safety and construction ease while maintaining energy efficiency.
Implementation Method 1
a heat source side refrigerant and a heat medium exchanging heat in a plurality of heat exchangers (15a, 15b)
Implementation Method 2
an anti-freezing control that prevents the heat medium from freezing is executed on a basis of a comparison between a temperature of the refrigerant in the at least one of the heat exchangers related to heat medium and the anti-freezing temperature
Data Source
AI summary
An air-conditioning apparatus uses a zeotropic refrigerant mixture, in which its saturated liquid refrigerant temperature is lower than the saturated gas refrigerant temperature under the same pressure condition, as the heat source side refrigerant. When one or some of a plurality of heat exchangers related to heat medium functions as an evaporator, the air-conditioning apparatus executes an anti-freezing control that prevents the heat medium from freezing by estimating occurrence of freezing of the heat medium on the basis of a value obtained by subtracting a freezing temperature correction value that is set as a positive value larger than zero from an evaporating temperature of the refrigerant in the heat exchanger related to heat medium.