Superheating control for heating, ventilation, air conditioning and refrigeration (HVACR) system including a dynamic receiver
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Solution Overview
Problem
Refrigeration circuits with fixed liquid receivers face inefficiencies across different operating conditions and loads, leading to instability and failures such as low pressure cutouts and excessive defrosting cycles due to uncontrolled mass flow changes.
Innovation Solution
A dynamic liquid receiver system with a controller that adjusts the refrigerant charge based on measured subcooling values and operating modes, using inlet and outlet valves to regulate the working fluid quantity and mass flow rate, ensuring stable operation by maintaining optimal refrigerant levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed receiver filling setting is used, then the system can operate across different parts of the operating map, but efficiency is sacrificed under specific operating conditions
Solution Approach 1:
The patent implements a dynamic receiver filling system where the receiver filling valve is controlled to adjust the refrigerant charge in the receiver based on operating conditions. The controller dynamically modifies the filling level to optimize efficiency across different operating modes (heating, cooling, defrosting), transforming the static fixed-filling system into an adaptive dynamic system that responds to real-time operational requirements
2Productivity
If working fluid is drained from the dynamic receiver into the circulating flow, then mass flow changes occur, but this causes instability and system failures due to delayed detection and response
Solution Approach 1:
The controller proactively monitors and predicts the effects of working fluid drainage on mass flow before instability occurs. By detecting changes in operating parameters and anticipating the impact of receiver drainage on system stability, the controller adjusts the expander control in advance to prevent low pressure cutouts, excessive defrosting cycles, and other failure modes
Solution Approach 2:
The system implements a feedback control mechanism where the controller continuously monitors operating parameters (pressure, temperature, mass flow) and adjusts the expander control based on the detected effects of receiver drainage. This closed-loop feedback ensures that mass flow changes are compensated in real-time, maintaining system stability despite dynamic refrigerant charge adjustments
Data Source
AI summary
A dynamic receiver is included in parallel to an expander of a heating, ventilation, air conditioning, and refrigeration (HVACR) system. The dynamic receiver allows control of the refrigerant charge of the HVACR system to respond to different operating conditions. The dynamic receiver can be filled or emptied in response to the subcooling observed in the HVACR system compared to desired subcooling for various operating modes. The flow through an expander of the HVACR system can be controlled to account for the mass flow rate through an outlet valve of the dynamic receiver when the dynamic receiver is emptied, preventing or reducing instability or effects on system parameters such as the suction superheat.