Reverse Liquid Defrosting for Multi-Evaporator Refrigeration Systems
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Solution Overview
Problem
Existing multi-evaporator refrigeration systems with a unique expansion device face challenges in defrosting a selected evaporator without pressure drops and maintaining efficient operation across evaporators operating at different pressures.
Innovation Solution
The system employs additional liquid reverse flow lines and check valves, along with an ejector and vapor-liquid separator, to enable defrosting of a selected evaporator while maintaining compressor suction pressure and evaporating pressures across non-selected evaporators, and includes a second compression stage for enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If liquid refrigerant is circulated through a selected evaporator in reverse direction for defrosting, then ice accumulation is removed, but pressure drops occur in the system
Solution Approach 1:
The patent introduces a three-way valve as an intermediary device to control refrigerant flow distribution. This valve directs liquid refrigerant to either the selected evaporator for defrosting or to non-selected evaporators for normal cooling, preventing pressure drops by ensuring continuous flow through the expansion device and maintaining system pressure balance.
Solution Approach 2:
The refrigeration system is segmented into multiple independent flow paths: one path for defrosting the selected evaporator and another path for cooling non-selected evaporators. This segmentation allows simultaneous operation of defrosting and cooling functions without interfering with each other's pressure requirements, eliminating pressure drops.
2Device complexity
If a unique expansion device feeds all evaporators in normal flow, then system complexity is reduced, but defrosting of a selected evaporator becomes difficult without affecting other evaporators
Solution Approach 1:
The patent employs a three-way valve that dynamically redirects refrigerant flow based on operational requirements. During defrosting cycles, the valve dynamically switches to send liquid refrigerant to the selected evaporator in reverse flow mode while simultaneously directing flow to non-selected evaporators, enabling flexible operation with a single expansion device.
Solution Approach 2:
The unique expansion device serves multiple functions: it provides refrigerant to all evaporators during normal cooling operation and redirects refrigerant to the selected evaporator during defrosting cycles. The three-way valve enhances this universality by enabling the single expansion device to support both cooling and defrosting operations of different evaporators sequentially or simultaneously.
3Object-generated harmful factors
If defrosting is performed by hot vapor refrigerant flow, then ice is melted, but energy efficiency decreases
Solution Approach 1:
The patent utilizes phase transition of liquid refrigerant to cold vapor as it flows through the selected evaporator during defrosting. This phase transition absorbs heat from the ice accumulation, melting it efficiently. The sub-cooled liquid refrigerant then flows to non-selected evaporators where it provides additional cooling, effectively utilizing the refrigerant's thermal energy without requiring external heating sources.
Solution Approach 2:
The patent converts the normally wasted cold thermal energy in the refrigerant into a useful defrosting resource. By circulating sub-cooled liquid refrigerant through the selected evaporator in reverse flow, the system uses the refrigerant's cold content to melt ice, transforming what would be a energy loss into a beneficial defrosting mechanism that also provides cooling to other evaporators.
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 allows for effective defrosting of evaporators without pressure drops and enhances system efficiency, making it suitable for vehicle air conditioning with varying re-heating performance levels.
Implementation Method 1
circulating liquid refrigerant through the selected evaporator in reverse direction to normal flow - by a dedicated liquid reverse flow line - to release heat to dissolve the ice that has accumulated on the coil
Implementation Method 2
the liquid refrigerant wich flows through it becomes sub-cooled
Implementation Method 3
circulating said sub-cooled liquid refrigerant into the unique expansion device feeding all the other non-selected evaporators... so as to feed two distinct non-selected evaporators at two different evaporating pressures
Data Source
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AI summary
Reverse liquid defrosting system and method of a selected evaporator of a plurality of evaporators of a closed loop vapor cycle refrigeration system having a unique expansion device feeding all the evaporators in normal flow are provided. During defrost, the liquid refrigerant - that releasing heat in the selected evaporator became subcooled - is circulated to the remaining not- selected evaporators by the unique expansion device or eventually also by an auxiliary expansion device in order to feed at least two distinct non-selected evaporators at different evaporating pressures obtaining that the higher evaporating pressure becomes the compression suction pressure via the use of additional flow lines, check valves, an ejector, a vapor-liquid separator and isolation valves which can be automatic valves of the close on rise of inlet pressure type. Usable in vehicles as heat pump mobile system at various re- heating performance levels.