Brayton Refrigeration Flow Control for Fast Heat-Load Response
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Solution Overview
Problem
In refrigerating apparatus using a Brayton cycle with multiple stages of compressors, controlling refrigeration capacity in response to changes in heat load is slow and inefficient, leading to reduced coefficient of performance due to changes in rotational speed, which affects adiabatic efficiency and other control parameters.
Innovation Solution
Adjusting the openings of first and second valves to control the flow rate of refrigerant while keeping volume flow rate constant, using a buffer tank to manage pressure differences between high and low pressure lines, and incorporating a heat exchanger to precool refrigerant, allowing for rapid adjustment of refrigeration capacity without reducing adiabatic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotational speed control is used to adjust refrigeration capacity, then the refrigeration capacity can be adjusted to match heat load changes, but the response time becomes slow and the coefficient of performance declines
Solution Approach 1:
The patent changes the control parameter from rotational speed to refrigerant flow rate. By controlling the flow rate of refrigerant through the expansion turbine while maintaining constant rotational speed, the system achieves rapid adjustment of refrigeration capacity without the slow response and efficiency loss associated with rotational speed control. This parameter substitution resolves the contradiction between adaptability and response speed.
2Adaptability or versatility
If rotational speed control is used to adjust refrigeration capacity, then the refrigeration capacity can be adjusted, but the adiabatic efficiency of the expander is reduced
Solution Approach 1:
The patent substitutes rotational speed control with refrigerant flow rate control. The expansion turbine operates at constant rotational speed, maintaining optimal adiabatic efficiency, while the refrigeration capacity is adjusted by controlling the mass flow rate of refrigerant through the expansion valve. This eliminates the energy loss caused by varying rotational speed while preserving the ability to adjust refrigeration capacity.
3Productivity
If multiple stages of compressors are used to improve cooling capacity, then the refrigeration capacity increases, but the number of control parameters increases and response becomes slower
Solution Approach 1:
The patent applies a unified control strategy where the flow rates of refrigerant are controlled for all compression stages simultaneously. Instead of independently controlling each compressor's rotational speed, the system uses a single flow rate control mechanism that affects all stages, reducing the number of control parameters while maintaining the enhanced cooling capacity provided by multiple compression stages.
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 approach enables rapid and efficient response to changes in heat load without reducing the coefficient of performance, maintaining energy efficiency and simplifying the system by avoiding the need for external power supply.
Implementation Method 1
a Brayton cycle type refrigerating apparatus which is capable of controlling the cooling capacity against a change in heat load of the object to be cooled
Implementation Method 2
reduction the adiabatic efficiency of the expander
Implementation Method 3
heat exchanger for exchanging heat between the refrigerant compressed by the compressors and the refrigerant after cooling the object to be cooled
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
To provide a Brayton cycle type refrigerating apparatus using multiple stages of compressors and having a good response without reduction in efficiency due to change in heat load of the object to be cooled, the Brayton cycle type refrigerating apparatus (100) according to the present invention comprises, on a refrigerant line (101), multiple stages of compressors (102a, 102b, 102c), a temperature sensor (160) for detecting heat load of an object to be cooled, and a buffer tank (111) provided between a low pressure line (109) and a high pressure line (110), wherein a flow rate of the refrigerant in the refrigerant line is controlled by controlling opening degrees of valves (112, 113) to adjust the cooling capacity.