Air-conditioning system with variable subcooling
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Solution Overview
Problem
Conventional air-conditioning systems face inefficiencies in handling increased outside air ventilation rates and humidity control, leading to over-sizing of HVAC units and high energy consumption, as they lack effective capacity control and modulation capabilities, especially in dehumidification processes.
Innovation Solution
A dedicated outside air-conditioning system (DOAS) with heat exchanger coils and sensors, utilizing variable subcooling refrigerant and modulating hot discharge gas to enhance system capacity and efficiency, incorporating fluid control valves and performance sensors to optimize refrigerant delivery and reheating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional central HVAC systems are oversized to handle peak latent load and meet ASHRAE ventilation standards, then humidity control capability is improved, but system size and energy consumption increase
Solution Approach 1:
The patent implements dynamic modulation of the hot gas valve to control the amount of hot discharge gas injected into the evaporator. This allows the system to adjust its dehumidification capacity in real-time based on actual load conditions, rather than operating at fixed high capacity. The control system monitors conditions and modulates the valve opening to match the precise amount of hot gas needed, enabling the system to maintain humidity control capability while consuming less energy during part-load operation.
Solution Approach 2:
The system changes the temperature parameter of the refrigerant by injecting hot discharge gas directly into the evaporator. This raises the evaporator temperature above the standard subfreezing temperature, allowing moisture to condense on the evaporator coils for dehumidification. By dynamically adjusting this temperature parameter through hot gas injection, the system can control humidity levels without requiring an oversized physical configuration.
2Productivity
If outside air flow rate is increased to meet ASHRAE ventilation standards, then ventilation capability is improved, but difficulty in achieving target humidity level increases
Solution Approach 1:
The patent introduces hot discharge gas as an intermediary substance to facilitate dehumidification. The hot gas is injected into the evaporator to raise its temperature, creating conditions where moisture from the high-volume outside air can condense on the evaporator coils. This intermediary hot gas enables the system to handle increased ventilation airflows while maintaining the ability to achieve target humidity levels, as the heated evaporator surface promotes condensation of excess moisture from the ventilated air.
3Adaptability or versatility
If separate heat exchangers are used for refrigerant subcooling and air reheating, then functional capability is improved, but system complexity and efficiency deteriorate
Solution Approach 1:
The patent merges the refrigerant subcooling function and the air reheating function into a single integrated heat exchanger assembly. The hot discharge gas heat exchanger serves dual purposes: it subcools the liquid refrigerant by heat exchange and simultaneously reheats the conditioned air that has been cooled by the evaporator. This consolidation eliminates the need for separate subcooling coils and reheating coils, reducing system complexity while maintaining both functional capabilities.
Solution Approach 2:
The hot gas heat exchanger is designed to perform multiple functions within a single component. It acts as both a refrigerant subcooling device and an air reheating device. The heat exchanger is positioned and configured so that hot discharge gas flows through it to cool the liquid refrigerant line while also heating the conditioned air stream passing through the same component, thereby achieving universal functionality with a single device.
4Ease of manufacture
If conventional air conditioning systems are used without modulation capabilities, then initial system cost is reduced, but operational efficiency and capacity control are worsened
Solution Approach 1:
The system incorporates a control system that monitors operational conditions and provides feedback to modulate the hot gas valve. The control system receives information about system state and adjusts the valve opening accordingly to optimize performance. This feedback mechanism enables the system to automatically adjust its capacity and operation to match actual conditions, significantly improving operational efficiency without requiring complex manual controls or high-cost components.
Solution Approach 2:
The patent introduces dynamic modulation capability through the hot gas valve, which can adjust its opening position to control the flow of hot discharge gas into the evaporator. This dynamic adjustment allows the system to vary its dehumidification capacity in real-time based on load conditions, transforming a static system into a dynamic one that can optimize efficiency across different operating conditions without requiring a complete system redesign.
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 DOAS achieves improved latent capacity, energy efficiency, and precise control over supply air dry bulb temperature and humidity, reducing compressor power usage and enabling compliance with new efficiency regulations like ISMRE, while scaling down system size to match performance with larger conventional systems.
Implementation Method 1
heat exchanger coils configured with sensors, fluid and gas refrigerant control valves that combine the effects of variable subcooling refrigerant
Implementation Method 2
modulating hot discharge gas to provide enhanced system capacity and efficiency
Data Source
AI summary
A dedicated outside air-conditioning system (DOAS) that may automatically generate variable subcooling refrigerant delivered to the evaporator; and modulate hot discharge gas to reduce the relative humidity of the discharge air from the DOAS. The DOAS may include fluid control valves configured to regulate delivery of the refrigerant in order to seamlessly flex between maximum latent capacity (minimum discharge dewpoint) and maximum sensible capacity (minimum leaving air discharge dry bulb temperature) to match load and/or ventilation air requirements.