Refrigeration Defrost Control Using Closed-Valve Compressor Evacuation
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Solution Overview
Problem
Refrigeration devices face inefficiencies during the defrosting process due to unnecessary heating of refrigerant, which prolongs the defrosting time and can lead to incomplete defrosting or premature interruption, especially when the compressor is not optimized in relation to the shut-off valve and heater operation.
Innovation Solution
A refrigeration device with a compressor and shut-off valve configuration where the compressor operates with the shut-off valve closed to create negative pressure in the evaporator, allowing for efficient evaporation of refrigerant before defrosting, reducing the residual refrigerant and thus minimizing the energy needed for heating, and using a rotation speed-regulated compressor to manage pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the defrosting heater is operated immediately after the compressor switches off, then the defrosting process can start quickly, but a large amount of energy is wasted heating the liquid refrigerant which must then be evaporated
Solution Approach 1:
The control unit closes the shut-off valve before switching off the compressor, creating a sealed system where the compressor continues to operate and draw refrigerant into the evaporator. This preliminary action prepares the system by reducing the refrigerant quantity in the evaporator before defrosting begins, so that when the heater is activated, less energy is wasted evaporating liquid refrigerant and more energy is available for actually defrosting the evaporator surfaces.
2Quantity of substance
If the compressor continues to run with the shut-off valve closed, then liquid refrigerant evaporates and is drawn away reducing residual refrigerant, but the compressor running time must be extended
Solution Approach 1:
The control unit monitors the operating time of the compressor during the defrost preparation phase and compares it against a predetermined threshold value. When the compressor has run long enough for the refrigerant quantity in the evaporator to be sufficiently reduced, the control unit automatically switches off the compressor and activates the defrosting heater. This parameter-based control ensures optimal refrigerant removal without unnecessarily extending compressor runtime.
3Loss of energy
If a waiting period is introduced between compressor shutdown and heater activation, then less liquid refrigerant remains to be evaporated, but the refrigerating compartment warms up and may require premature defrosting interruption
Solution Approach 1:
Instead of shutting off the compressor and creating an idle waiting period, the invention maintains continuous useful action by keeping the compressor running with the shut-off valve closed. The compressor continues to draw refrigerant into the evaporator where it evaporates and is removed from the system, continuously reducing the refrigerant quantity without allowing the refrigerating compartment to warm up. This eliminates the need for premature defrosting interruption while maintaining energy efficiency.
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 energy required for defrosting, shortens the defrosting time, and minimizes unnecessary heating of the refrigerating compartment, enhancing overall energy efficiency and ensuring complete defrosting without interrupting cooling requirements.
Implementation Method 1
When the compressor operates with the shut-off valve closed, it creates a negative pressure in the evaporator which favors the evaporation of liquid refrigerant contained therein
Implementation Method 2
When the compressor operates with the shut-off valve closed, it creates a negative pressure in the evaporator which favors the evaporation of liquid refrigerant contained therein; Since the vapor produced during the evaporation is drawn away by the compressor
Implementation Method 3
a heater for defrosting the evaporator
Data Source
AI summary
The invention relates to a refrigeration device, in particular a domestic refrigeration device, comprising a refrigerant circuit. The refrigerant circuit has a compressor, an evaporator, and a shut-off valve between an outlet of the compressor and an inlet of the evaporator. The refrigeration device also comprises a heater for defrosting the evaporator and a control unit that is designed to prepare for defrosting of the evaporator by operating the compressor with the shut-off valve closed.