CO2 Refrigerant Pressure Control With Split Heat Exchanger
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Solution Overview
Problem
Refrigeration apparatuses using carbon dioxide as a refrigerant face performance deterioration due to increased specific enthalpy at the evaporator inlet, especially when the temperature of the refrigerant at the gas cooler outlet rises, leading to decreased coefficients of performance and refrigeration efficiency.
Innovation Solution
Incorporating a pressure-regulation throttle section, a tank, a split heat exchanger, and auxiliary throttle sections to regulate refrigerant pressure, with a control system that adjusts the pressure of the refrigerant flowing into the main throttle section based on detected pressures, ensuring optimal refrigerant flow and maintaining a consistent refrigerant amount throughout the cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the discharge pressure of the compression section is increased to decrease specific enthalpy at the evaporator inlet, then refrigeration performance is improved, but coefficients of performance decrease due to increased compression power
Solution Approach 1:
The patent divides the single refrigerant flow into two separate flows using a flow divider. One flow goes through the evaporator while the other bypasses it. This segmentation allows independent control of refrigerant paths to optimize both refrigeration effect and energy efficiency without requiring excessive compression pressure.
Solution Approach 2:
The patent introduces an auxiliary heat exchanger as an intermediary component that enables heat exchange between the two refrigerant flows. This mediator allows the system to adjust refrigeration performance by controlling heat transfer between flows, thereby improving efficiency without increasing compression power.
2Temperature
If the temperature of refrigerant at the gas cooler outlet increases due to high outside air temperature, then heat exchange efficiency decreases, but specific enthalpy at the evaporator inlet increases causing refrigeration performance deterioration
Solution Approach 1:
The patent employs dynamic control mechanisms including adjustable flow dividers and controllable throttle valves that can adapt refrigerant flow distribution based on operating conditions. When gas cooler outlet temperature increases due to high ambient temperature, the system dynamically adjusts flow ratios to maintain optimal refrigeration performance despite temperature variations.
Solution Approach 2:
The system changes operational parameters such as flow distribution ratios, throttle valve openings, and heat exchanger configurations to optimize performance under varying temperature conditions. By adjusting these parameters dynamically, the system maintains efficient refrigeration even when gas cooler outlet temperature rises.
3Productivity
If a split cycle is implemented to cool the refrigerant flow through an auxiliary throttle section, then specific enthalpy at the evaporator inlet decreases and refrigeration performance is enhanced, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated components. The flow divider also serves as a heat exchanger, and the auxiliary throttle section is integrated with the main refrigerant circuit. This merging reduces the number of separate components needed, thereby lowering system complexity while maintaining the performance benefits of the split cycle.
Solution Approach 2:
Components in the system are designed with multi-functionality. For example, the auxiliary heat exchanger can operate in different modes depending on system requirements, and the flow divider can adjust its configuration based on operational needs. This universality allows a single component to perform multiple functions, reducing overall system complexity.
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 configuration effectively maintains the required refrigerant amount, stabilizes refrigerant flow, and enhances refrigeration performance by regulating pressure and optimizing the refrigerant cycle, thereby improving both refrigeration and cold storage operations.
Implementation Method 1
a split heat exchanger provided in the refrigerant circuit that is on a downstream side of the tank and is on an upstream side of the main throttle section
Implementation Method 2
a pressure-regulation throttle section connected to the refrigerant circuit that is on a downstream side of the gas cooler and is on an upstream side of the main throttle section
Data Source
AI summary
Refrigeration apparatus R that includes a refrigerant circuit composed of compressor 11, gas cooler 28, electric expansion valve 39, and evaporator 41 includes: electric expansion valve 33; tank 36; split heat exchanger 29; electric expansion valve 43; electric expansion valve 47; auxiliary circuit 48; main circuit 38; low-pressure sensor 51; and control apparatus 57, in which control apparatus 57 regulates the pressure of the refrigerant after the refrigerant flows out of tank 36 but before flows into electric expansion valve 39 to be a first constant pressure when the pressure detected by low-pressure sensor 51 is smaller than a specified pressure, and regulates the pressure of the refrigerant to be a second constant pressure smaller than the first constant pressure when the pressure detected by low-pressure sensor 51 is larger than the specified pressure.