Subcooler Valve Layout for Refrigerant Storage and Pressure Relief
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Solution Overview
Problem
Reversible HVAC refrigerant systems require a larger and more expensive receiver to store excess refrigerant during the heating mode due to the difference in refrigerant charge between heating and cooling modes.
Innovation Solution
A refrigerant system with a valve and subcooler arrangement that allows for the storage of excess refrigerant in the heating mode by using a valve system to connect and disconnect the main coil and subcooler, and a pressure relief valve to manage pressure limits, thereby minimizing the size of the receiver needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a receiver or holding tank is used to store excess liquid refrigerant during heating mode, then the system can accommodate the difference in refrigerant charge between heating and cooling modes, but the receiver becomes rather large and expensive
Solution Approach 1:
The patent combines the subcooler function with excess refrigerant storage capability. The subcooler, originally designed for heat exchange, is utilized to store excess liquid refrigerant during heating mode by closing the expansion valve to trap refrigerant between the subcooler and the valve, eliminating the need for a separate large receiver tank
Solution Approach 2:
The subcooler serves multiple functions: it acts as both a heat exchange device and a refrigerant storage reservoir. By implementing this multi-functionality, the system accommodates varying refrigerant charge requirements between heating and cooling modes without requiring additional dedicated storage components
2Quantity of substance
If the valve system closes to trap refrigerant in the subcooler during heating mode, then refrigerant storage is achieved, but pressure may exceed safe limits causing overloading
Solution Approach 1:
The pressure relief valve provides continuous feedback on the pressure conditions within the subcooler. When pressure reaches a predetermined maximum limit, the valve automatically opens to release excess pressure, creating a closed-loop control system that maintains pressure within safe operating parameters while allowing refrigerant storage
Solution Approach 2:
The pressure relief valve is pre-configured with a spring mechanism that provides cushioning against excessive pressure buildup. The spring is calibrated to open the valve at a specific pressure threshold, preventing pressure from exceeding safe limits before damage can occur to the system components
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 reduces the size and cost of the receiver by effectively managing refrigerant storage and pressure in the system, ensuring efficient operation in both heating and cooling modes while preventing overloading and damage from excessive pressure.
Implementation Method 1
the pressure relief valve opens to release at least some of the refrigerant from within the heat exchanger system in response to the refrigerant within the heat exchanger system exceeding a maximum pressure limit
Implementation Method 2
The exterior heat exchanger system is arranged to release heat to the outside fluid when the refrigerant system is in the cooling mode and absorb heat from the outside fluid when the refrigerant system is in the heating mode
Implementation Method 3
a compressor periodically drawing the refrigerant at a suction pressure and discharging the refrigerant at a discharge pressure, thereby providing the refrigerant system with a high-pressure side and a low-pressure side
Implementation Method 4
the valve system is in the open position when the refrigerant system is in the heating mode while the refrigerant within the subcooler is above the predetermined pressure limit
Data Source
Figure 1~2
AI summary
A reversible HVAC heating/cooling refrigerant system includes a novel valve system that allows an outdoor heat exchanger to function as a subcooler during a cooling or defrost mode and function as a receiver tank for storing excess liquid refrigerant during a heating mode. In the heating mode, a cooling expansion valve is kept slightly open to flood the subcooler with liquid refrigerant while a heating expansion valve is regulated to maintain a desired level of superheat at the suction side of the refrigerant system's compressor. The novel valve system also serves as a pressure relief valve to protect the subcooler from excess pressure caused by thermal expansion of liquid refrigerant trapped within the subcooler.