A method of operating a cooling system
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Solution Overview
Problem
Conventional cooling systems face challenges in efficiently managing refrigerant flow during compressor startup and operation, leading to potential damage from liquid hammering and increased manufacturing costs due to complex structures required for unloading valves in closed-type compressors.
Innovation Solution
A method involving a suction pressure regulating valve and an unloading part installed in parallel on the refrigerant inflow tube between the compressor and evaporator, allowing reduced refrigerant flow during initial startup or re-startup and full capacity flow during normal operation, minimizing compressor load and preventing liquid hammering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full capacity refrigerant flow is supplied to the compressor during initial startup or re-startup, then the compressor can operate at full capacity, but liquid hammering damage occurs and compression efficiency decreases
Solution Approach 1:
The system dynamically adjusts refrigerant flow capacity based on operational state. During initial startup or re-startup, the unloading part restricts flow to less than full capacity. During normal operation, the unloading part opens to allow full capacity flow. This dynamic adaptation resolves the contradiction between protecting the compressor during vulnerable startup phases and maximizing productivity during stable operation.
2Reliability
If an unloading valve is integrated into the closed-type compressor to enable unloaded operation, then compressor load is minimized during startup, but the manufacturing cost increases and device complexity increases
Solution Approach 1:
The unloading function is segmented from the compressor body and implemented as a separate part installed on the refrigerant inflow tube. This external unloading part can be installed or removed independently without modifying the compressor's internal structure, thus protecting the compressor during startup while avoiding increased manufacturing complexity and cost.
Solution Approach 2:
The unloading part serves multiple functions: it restricts refrigerant flow during startup to prevent liquid hammering, enables unloaded operation to minimize compressor load, and can be easily installed or removed. This multi-functionality resolves the contradiction by providing comprehensive protection without requiring complex integrated design.
3Productivity
If refrigerant flow rate is increased during normal operation to match compressor capacity, then compression efficiency is improved, but liquid hammering risk increases during transitions
Solution Approach 1:
The unloading part is configured to maintain a restricted flow state during initial startup or re-startup before full operation begins. This preliminary restricted flow prevents liquid hammering from occurring during the transition phase, and only after this protected startup phase does the system transition to full capacity flow for optimal compression efficiency.
Data Source
Figure 1
AI summary
According to the present invention, According to the present invention, a cooling system is provided which comprises: a compressor for compressing refrigerant; a condenser for condensing the refrigerant which is compressed by said compressor; an expansion valve for expanding the refrigerant which is condensed by said condenser; an evaporator for evaporating the refrigerant which is expanded by said expansion valve; a suction pressure-regulating valve which is installed to a refrigerant inflow tube connecting between said compressor and said evaporator and which allows the refrigerant supplied from said evaporator to said compressor to have a pressure lower than a predetermined pressure for preventing said compressor from being overloaded, wherein said suction pressure-regulating valve is set to supply the amount of the refrigerant which is less than amount of refrigerant corresponding to compression capacity of said compressor; and, an unloading part being installed to said refrigerant inflow tube in parallel with said suction pressure-regulating valve and including a bypass tube for an unloaded operation and an opening/closing-valve for said bypass tube, wherein said bypass tube has a supply amount of the refrigerant, which is equivalent to a difference between the supply amount of the refrigerant corresponding to the compression capacity of said compressor and the supply amount of the refrigerant through said suction pressure regulating valve, wherein said unloading part makes it possible to attain the unloaded operation by closing said bypass tube by means of said opening/closing-valve, to thereby supply the refrigerant to said compressor only through said suction pressure regulating valve upon an initial startup or a re-startup of said compressor, so that the amount of the refrigerant flowing through said suction pressure regulating valve is less than the amount of the refrigerant corresponding to the compression capacity of said compressor and, wherein said unloading part makes it possible to attain a normal operation by opening said bypass tube by means of said opening/closing-valve, to thereby supply the refrigerant to said compressor through said suction pressure regulating valve and said bypass tube while in a normal operation of said compressor after a certain period from the initial startup, so that the amount of the refrigerant in the normal operation is equivalent to the amount of the refrigerant corresponding to the compression capacity of said compressor.