Dynamic Receiver Control for HVACR Mass Flow Stability
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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 from dynamic receivers.
Innovation Solution
A dynamic liquid receiver system with a controller that adjusts the refrigerant charge by opening or closing valves to maintain a target quantity based on subcooling values and operating modes, ensuring stable mass flow through the expander and reducing instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed liquid receiver filling level 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 liquid receiver system where the filling level is continuously adjusted based on operating conditions such as load, ambient temperature, and system pressure. The receiver transitions from a fixed filling level to a variable filling level that adapts to different operating points on the operating map, thereby optimizing efficiency across all conditions rather than sacrificing efficiency for one specific condition.
2Quantity of substance
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 patent incorporates a control system with sensors that continuously monitor mass flow, pressure, and temperature parameters in real-time. When working fluid is drained from the dynamic receiver, the feedback system immediately detects the mass flow change and adjusts system parameters (such as compressor speed, expansion valve opening, or receiver discharge rate) to maintain stability and prevent failures like low pressure cutouts or excessive defrosting cycles.
3Loss of energy
If the dynamic receiver adjusts refrigerant charge dynamically, then operating efficiency improves, but system complexity increases due to additional control mechanisms
Solution Approach 1:
The patent designs the dynamic receiver control system to perform multiple functions: it not only adjusts refrigerant charge based on operating conditions but also integrates with existing system components (compressor, expansion valve, sensors) to provide coordinated control. This multi-functionality allows the system to achieve efficiency improvements across different operating conditions while avoiding the need for entirely separate control systems, thereby limiting the increase in 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
The dynamic receiver system enhances operational stability and efficiency by maintaining optimal refrigerant levels, reducing failure modes and improving overall system performance across varying loads and conditions.
Implementation Method 1
the first heat exchanger is configured to exchange heat between a working fluid in the fluid circuit and a first process fluid, the second heat exchanger is configured to exchange heat between the working fluid and a second process fluid, and the third heat exchanger is configured to exchange heat with ambient air
Data Source
Figure 1A
Figure 1B
Figure 1C
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.