Heat Source Unit Refrigerant Valve Control for High-Pressure Safety
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Solution Overview
Problem
Existing refrigeration apparatuses face challenges in managing high pressures within the refrigeration cycle that exceed the critical pressure of the refrigerant, leading to potential damage and reduced cooling capacity when operating near the design pressure limits.
Innovation Solution
A refrigeration apparatus with a heat source unit that includes a compressor, heat exchanger, and a controller that adjusts the opening degree of refrigerant control valves in a stepwise manner, using a variable unit change amount based on outdoor air temperature as a high pressure index to maintain high pressure within safe limits and enhance cooling capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the opening degree of the refrigerant control valve is increased to enhance cooling capacity, then the cooling capacity is improved, but the high pressure of the refrigeration cycle exceeds the critical pressure leading to potential damage
Solution Approach 1:
The patent applies dynamics by making the unit change amount of the valve opening degree variable rather than fixed. The controller dynamically adjusts the unit change amount based on the current valve opening degree and high pressure conditions. When the valve opening degree is small, a larger unit change amount is used for faster response. When the valve opening degree is large or high pressure approaches critical levels, a smaller unit change amount is used to prevent excessive pressure increases, thus resolving the contradiction between cooling capacity enhancement and high pressure safety.
Solution Approach 2:
The patent changes the parameter of the unit change amount of the valve opening degree based on operating conditions. By adjusting this parameter dynamically according to the current valve opening degree and high pressure index, the system can optimize the balance between cooling capacity and pressure safety. The controller modifies the control parameters to prevent the high pressure from exceeding critical pressure while maintaining effective cooling performance.
2Device complexity
If a fixed unit change amount is used for valve opening degree control, then the control system is simple, but the high pressure cannot be effectively managed when operating near design pressure limits
Solution Approach 1:
The control system transitions from a static fixed unit change amount to a dynamic variable unit change amount that adapts to operating conditions. The controller determines the unit change amount based on the current valve opening degree and high pressure index, creating a more complex but reliable control mechanism that can effectively manage high pressure near design limits while maintaining system stability.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the high pressure index and the current valve opening degree, then using this information to adjust the unit change amount for the next control step. This feedback mechanism allows the system to respond to changing conditions and maintain high pressure within safe limits, resolving the contradiction between control simplicity and effective high pressure management.
3Speed
If the valve opening degree is adjusted in large steps to respond quickly to cooling demands, then the response speed is improved, but the high pressure may exceed safe limits causing damage
Solution Approach 1:
The patent applies dynamics by making the step size (unit change amount) variable rather than fixed. The controller dynamically selects the unit change amount based on the current operating state, allowing large steps when safe and small steps when approaching pressure limits. This resolves the contradiction between fast response speed and preventing high pressure damage.
Solution Approach 2:
The patent changes the control parameter (unit change amount of valve opening degree) based on the high pressure index and current valve opening degree. By adjusting this parameter dynamically, the system can achieve fast response when conditions permit while preventing harmful high pressure excursions, thus resolving the contradiction between response speed and damage prevention.
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 allows for increased cooling capacity while preventing damage by setting higher upper limit pressures closer to the design pressure, ensuring appropriate control of refrigerant flow and pressure management.
Implementation Method 1
a compressor
Implementation Method 2
a heat-source-side heat exchanger
Implementation Method 3
a refrigerant control valve of which an opening degree is variable to control a flow of the refrigerant
Data Source
AI summary
The heat source unit includes a refrigerant control valve and a controller. If the opening degree of the refrigerant control valve changes, the high pressure of the refrigeration cycle changes. The controller adjusts the opening degree of the refrigerant control valve in a stepwise manner. The amount of change by one step in the opening degree of the refrigerant control valve is the unit change amount. The physical quantity indicating the high pressure of the refrigeration cycle is the high pressure index. The controller changes the unit change amount employed when the high pressure index is higher than the reference value to a value lower than the unit change amount employed when the high pressure index is lower than the reference value.