Refrigerating Cycle Pressure Control for Fluctuating Thermal Loads
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Solution Overview
Problem
Conventional supercritical vapor compression cycle apparatuses struggle to efficiently manage fluctuations in thermal load and temperature conditions, leading to inefficient operation and inability to maintain high energy-saving performance.
Innovation Solution
A refrigerating cycle apparatus with a refrigerant circuit, heat exchangers, and a controlling system that adjusts compressor frequency, throttling means, and fluid flow rates based on detected thermal and pressure conditions to maintain optimal high-pressure pressure targets, ensuring operation in a high Coefficient of Performance (COP) state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional supercritical vapor compression cycle control methods are used, then the system can operate with simple control logic, but the system cannot efficiently respond to fluctuations in thermal load and temperature conditions
Solution Approach 1:
The control method dynamically adjusts the high-side pressure target value based on real-time detection of thermal load and temperature conditions. The system transitions from static pressure control to dynamic pressure control, allowing the high-side pressure target to vary according to operating conditions, thereby improving adaptability to thermal load fluctuations.
Solution Approach 2:
The control system incorporates feedback mechanisms by detecting actual thermal load and temperature conditions, comparing them with target values, and adjusting the high-side pressure target accordingly. This closed-loop control enables the system to respond to changing conditions while maintaining optimal performance.
2Use of energy by moving object
If the high-side pressure is kept constant to simplify control, then the control system remains simple, but the coefficient of performance cannot be optimized under varying thermal load conditions
Solution Approach 1:
The system changes the high-side pressure parameter dynamically based on thermal load and temperature conditions. By adjusting the high-side pressure target value according to operating conditions, the system optimizes the coefficient of performance across different thermal loads, transitioning from fixed parameter control to variable parameter control.
3Adaptability or versatility
If the system operates without considering heat transfer characteristics of the fluid, then the control logic remains simple, but the system cannot cope with fluctuations in fluid temperature and flow rate
Solution Approach 1:
The system uses the high-side pressure target value as an intermediary parameter that reflects the heat transfer characteristics of the fluid. By detecting fluid temperature and flow rate conditions and translating them into pressure target adjustments, the system indirectly accounts for heat transfer characteristics without requiring direct measurement of complex heat transfer parameters.
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 system effectively maintains high COP even with fluctuations in thermal load and temperature, enhancing energy-saving performance by adjusting refrigerant flow and pressure settings in response to changing conditions.
Implementation Method 1
a low-pressure heat exchanger through which a cooled medium flows, the refrigerant circulating through the refrigerant circuit cooling the heated medium in the high-pressure heat exchanger and cooling the cooled medium in the low-pressure heat exchanger
Implementation Method 2
a high-pressure heat exchanger through which a heated medium flows
Implementation Method 3
a high-pressure heat exchanger through which a heated medium flows
Implementation Method 4
the refrigerant circulating through the refrigerant circuit cooling the heated medium in the high-pressure heat exchanger
Implementation Method 5
a compressor, a high-pressure heat exchanger (radiator), a throttling means, and an evaporator
Implementation Method 6
for which a high-pressure side operates in a gas-liquid two-phase region or a supercritical region depending on conditions of thermal load
Implementation Method 7
a throttling means, and an evaporator
Data Source
AI summary
In a refrigerating cycle apparatus and control method thereof, a controller sets a high-pressure pressure target value from thermal load and temperature conditions based on refrigerant information that has been obtained from detectors, and controls at least one of a rotational frequency of a compressor, a degree of opening of an electronic expansion valve, a rotational frequency of an outdoor fan, or a rotational frequency of an indoor fan to match a high-pressure pressure to the high-pressure pressure target value that has been set. Here, a threshold value is set when the high-pressure pressure target value is set, and a method for setting the high-pressure pressure target value is modified depending on whether the high-pressure pressure is greater than or equal to the threshold value or less than the threshold value when the high-pressure pressure target value is decided.