Chiller Bleed Device Control for Low-GWP Refrigerant Air Accumulation
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Solution Overview
Problem
Conventional chillers using low-pressure, low global warming potential refrigerants face instability due to insufficient control of noncondensable gases, leading to operational failures and corrosion, as the existing methods for gas discharge are not sensitive enough to maintain stable conditions.
Innovation Solution
A control device and method that estimate the amount of air entering the chiller based on its structure and pressure, activating a bleed device when the total value exceeds a preset tolerance, ensuring the air level remains below a threshold that could disrupt operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure-difference-based discharge method is used, then the bleed device can discharge noncondensable gas, but the control sensitivity is insufficient to maintain stable operation with low GWP refrigerants
Solution Approach 1:
The invention changes the control parameter from pressure difference to air entering amount estimation. By estimating the air entering amount based on chiller structure and operating conditions, and comparing it against a threshold value, the system achieves more precise and sensitive control of noncondensable gas levels, enabling stable operation with low GWP refrigerants.
2Object-affected harmful factors
If low GWP refrigerants are used, then environmental impact is reduced, but the refrigerant is easily broken down by oxygen producing harmful by-products
Solution Approach 1:
The invention applies preliminary anti-action by proactively estimating and controlling air entering the chiller before oxygen can react with the low GWP refrigerant. By maintaining air entering amount below a threshold through predictive control, the system prevents the formation of harmful by-products like hydrogen fluoride and hydrogen chloride, while still using environmentally friendly refrigerants.
3Quantity of substance
If noncondensable gas accumulates in the chiller, then the existing bleed device can discharge it, but the condensing pressure rises causing operation failure
Solution Approach 1:
The invention implements feedback control by continuously estimating the air entering amount based on chiller operating conditions and structure, comparing it against a threshold value, and adjusting bleed device operation accordingly. This closed-loop approach maintains noncondensable gas levels within safe limits, preventing condensing pressure rise and operation failures.
Data Source
AI summary
The purpose of the present invention is to achieve stable operation when using a low pressure, low GWP refrigerant. In the present invention, a control device (16) is provided with an estimation unit (31), a determination unit (32), and an activation control unit (33). The estimation unit (31) estimates the amount of air entering using a degree of influence of air entering, which represents the ease with which air enters determined by the structure of the chiller, and a variable obtained by a function including pressure as a parameter. The determination unit (32) determines whether a total value for the amount of air entering is greater than or equal to a preset tolerance value. The activation control unit (33) activates a bleed device when the total value of the amount of air entering is equal to or greater than the tolerance value.