Heat Pump Dryer Refrigerant Precharge for Faster Start-Up
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Solution Overview
Problem
Heat pump dryers face challenges in reducing the time constant to full capacity at start-up due to their inherent slow rise in system equilibrium, which existing methods attempt to address using auxiliary heaters for a gradual increase in system performance.
Innovation Solution
A method and apparatus that collect refrigerant during a run cycle when pressure exceeds a threshold, retain it until the next cycle, and discharge it to an evaporator or condenser to elevate the refrigeration cycle's start condition, using a sensor and controller to manage the refrigerant's use and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If existing approaches use an auxiliary heater to gently add load during the run cycle, then the system equilibrium point rises slowly, but the time constant to full capacity at start-up remains long
Solution Approach 1:
The patent applies preliminary action by collecting and storing refrigerant in an accumulator during the run cycle, then discharging it at the start of the next cycle to pre-elevate the system equilibrium point before the compressor begins operation. This advance preparation eliminates the slow warm-up period inherent in conventional systems.
Solution Approach 2:
The patent changes the physical state and distribution of the refrigerant parameter by concentrating it in the accumulator during operation, then rapidly redistributing it to the evaporator/condenser at cycle start. This parameter transformation enables rapid elevation of system pressure and temperature equilibrium points.
2Productivity
If refrigerant is collected during run cycle when pressure exceeds threshold, then system capacity is elevated at start-up, but additional control complexity is introduced
Solution Approach 1:
The patent implements feedback control by continuously monitoring refrigerant pressure and using this information to control when the accumulator inlet valve opens and closes. The controller adjusts refrigerant collection based on real-time pressure conditions, ensuring optimal refrigerant accumulation without over-pressurizing the system.
Solution Approach 2:
The patent introduces an accumulator as an intermediary component between the evaporator/condenser and the rest of the refrigeration cycle. This intermediate storage device buffers refrigerant flow, allowing decoupling of refrigerant collection during operation from refrigerant discharge at start-up, thereby simplifying the overall control logic.
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 approach significantly reduces the time to reach full capacity, accelerating the drying process and improving the efficiency of the refrigeration cycle by modifying the start condition of the refrigeration cycle, thereby enhancing the system's transient performance during start-up.
Implementation Method 1
collecting refrigerant during a run cycle when pressure exceeds a predetermined threshold value
Implementation Method 2
discharging the retained refrigerant to an evaporator or condenser when the subsequent run cycle is started
Data Source
AI summary
An apparatus includes a mechanical refrigeration cycle arrangement having a working fluid, an evaporator, a condenser, a compressor, and an expansion device, cooperatively interconnected and containing the working fluid. The apparatus also includes a drum to receive clothes, a duct and fan arrangement configured to pass air over the evaporator, condenser and through the drum, a sensor located to sense parameters, a working fluid accumulator, and a controller coupled to the sensor, accumulator and/or compressor. The controller is operative to control collection of refrigerant during a run cycle when pressure exceeds a predetermined threshold value, control retention of the collected refrigerant when the run cycle is completed, until a subsequent run cycle, control discharge of the retained refrigerant to an evaporator or condenser when the subsequent run cycle is started, and control use of discharged refrigerant to elevate the refrigeration cycle by modifying a start condition of the refrigeration cycle.