Injection Refrigeration Cycle Pressure Control in Supercritical Overload
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Solution Overview
Problem
Vapor compression refrigeration cycles face challenges in controlling refrigeration capacity under overload conditions, particularly when the refrigerant enters a supercritical state, leading to difficulties in managing the specific enthalpy and cooling effect due to high inlet air temperatures at the radiator and evaporator.
Innovation Solution
A refrigeration cycle apparatus with a main circuit, an injection circuit, and a controller that adjusts the high-pressure-side pressure by controlling the second pressure reducing device and the heat transfer area of the radiator, allowing for increased cooling capacity even under overload conditions by managing the refrigerant's state and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant is subjected to pressure reduction under overload conditions, then the refrigerant may enter a supercritical state, but the degree of superheat cannot be calculated and specific enthalpy control becomes impossible
Solution Approach 1:
The patent changes the control parameter from degree of superheat (which cannot be calculated in supercritical state) to high-pressure-side pressure (which can be measured and controlled). The controller adjusts the high-pressure-side pressure within a predetermined range to indirectly control the specific enthalpy of the refrigerant, enabling reliable control even when the refrigerant enters supercritical state.
2Productivity
If the refrigerant enters a supercritical state during heating process, then no latent heat change occurs, but the cooling effect on the other portion of refrigerant cannot be expected
Solution Approach 1:
The patent controls the high-pressure-side pressure within a predetermined range to prevent the refrigerant from entering the supercritical state during the heating process in the heat exchanger. By maintaining pressure below the supercritical threshold, the refrigerant undergoes phase change with latent heat absorption, ensuring effective cooling of the other portion of refrigerant and maintaining high cooling capacity.
3Productivity
If the high-pressure-side pressure is increased to increase cooling capacity, then the refrigerant may enter supercritical state, but control becomes difficult under overload conditions
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors the high-pressure-side pressure and adjusts the opening degree of the expansion valve to maintain pressure within the predetermined range. This closed-loop control enables easy and reliable operation even under overload conditions, allowing the system to increase cooling capacity without risking supercritical state entry.
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 apparatus effectively increases cooling capacity by controlling the high-pressure-side pressure and heat transfer area, ensuring reliable operation even when the refrigerant is in a supercritical state, thereby enhancing cooling performance under high-load conditions.
Implementation Method 1
a compressor (1) that compresses a refrigerant
Implementation Method 2
a radiator (2) that rejects heat of the refrigerant compressed by the compressor
Implementation Method 3
a primary passage of an internal heat exchanger (3) that exchanges heat between the refrigerant which has passed through the radiator and the refrigerant which has passed through the radiator and is to be injected into the compressor
Implementation Method 4
a first pressure reducing device (4) that reduces a pressure of the refrigerant which has passed through the primary passage of the internal heat exchanger
Implementation Method 5
an evaporator (5) where the refrigerant that has been subjected to pressure reduction by the first pressure reducing device evaporates
Implementation Method 6
a second pressure reducing device (6) that reduces a pressure of the refrigerant which has passed through the radiator and is to be injected into the compressor
Data Source
AI summary
A refrigeration cycle apparatus increases the cooling capacity even under overload conditions in a refrigeration cycle apparatus that uses a refrigerant which undergoes transition to a supercritical state and in which the high-pressure side enters a supercritical state.A refrigeration cycle apparatus adjusts a high-pressure-side pressure of a refrigerant flowing through a main refrigerant circuit by causing a controller to control an opening degree of a second expansion valve and a heat transfer area of a radiator.