Multi-Coil Refrigerant Metering for Humidity-Safe Load Staging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing refrigerant systems with multiple coils face challenges in operating efficiently at reduced loads and preventing moisture condensation and humidity issues, particularly when only one variable expansion valve is active, leading to moisture condensation on inactive coils and increased humidity in the comfort zone.
Innovation Solution
A refrigerant system utilizing a single variable refrigerant metering device for the lowermost coil and one or more fixed refrigerant metering devices for upper coils, ensuring the lowermost coil operates at a lower superheat than others, thereby preventing moisture condensation and maintaining efficient cooling across varying loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If only one variable expansion valve is used to feed an upper evaporator coil while lower coils are deactivated, then the system can operate at reduced loads, but moisture condenses on the inactive lower coils and drains over them, increasing humidity in the comfort zone
Solution Approach 1:
The evaporator is divided into multiple independently metered coil circuits (upper and lower coils), each with its own fixed refrigerant metering device. This allows selective operation of individual coil circuits based on load requirements, enabling reduced capacity operation while maintaining proper refrigerant distribution to active coils and preventing moisture condensation issues on inactive coils.
2Reliability
If multiple variable expansion valves are used to individually meter refrigerant to each evaporator coil, then precise refrigerant control is achieved, but device complexity and cost increase
Solution Approach 1:
Different types of metering devices are assigned to different coil circuits based on their specific requirements. Fixed refrigerant metering devices are used for lower coils that operate at stable conditions, while variable expansion valves are used for upper coils that require dynamic control. This localized optimization achieves reliable refrigerant flow control while minimizing overall system complexity.
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 allows for efficient operation across various compressor capacities and loads while maintaining lower superheat in the lowermost coil, preventing moisture entrainment and reducing humidity, ensuring effective refrigerant flow and condensate drainage.
Implementation Method 1
a variable refrigerant metering device for throttling the flow of refrigerant to a multi-coil evaporator
Implementation Method 2
One or more of the metering devices may provide a fixed flow restriction
Implementation Method 3
an evaporator that uses the cooled refrigerant from the metering device to cool a current of air being supplied to a comfort zone
Implementation Method 4
a compressor for compressing a refrigerant
Implementation Method 5
a condenser for condensing and releasing heat from the compressed refrigerant
Data Source
AI summary
A refrigerant cooling system includes multiple evaporator coils fed by one variable refrigerant metering device and one or more fixed refrigerant metering devices. To avoid condensed moisture on the coils from being entrained by the supply air and ultimately adversely increasing the humidity of a room or comfort zone of a building, the variable refrigerant metering device delivers refrigerant to the evaporator's lowermost coil at a superheat that is less than that of the other higher coils. To operate the refrigerant system at various loads, two or more compressors are selectively energized individually and in combination for various stages of capacity, while the variable refrigerant metering device is active at each stage. The refrigerant system may include multiple refrigerant circuits that are hermetically isolated from each other, or two or more of the circuits may be in fluid communication with each other.