Reverse liquid defrosting system and method
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Solution Overview
Problem
Existing multi-evaporator refrigeration systems with a unique expansion device face challenges in defrosting selected evaporators without pressure drops and efficient heat transfer when using reverse liquid defrosting methods, as they cannot accommodate multiple 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 manage defrosting of selected evaporators while maintaining compressor suction pressure and enabling efficient heat transfer across multiple evaporators operating at different pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse liquid defrosting is used in a multi-evaporator system with a unique expansion device, then defrosting of selected evaporators is achieved, but pressure drops occur and efficient heat transfer cannot be maintained across multiple evaporators operating at different pressures
Solution Approach 1:
The system segments the evaporators into defrosting and non-defrosting groups using isolation valves, allowing independent pressure control for each group. The unique expansion device is divided into separate circuits with individual flow control, enabling each evaporator to operate at its optimal pressure while one evaporator undergoes defrosting without affecting the others.
Solution Approach 2:
An intermediary circuit is introduced between the expansion device and evaporators, containing flow control valves and isolation valves that act as mediators to regulate refrigerant flow and pressure distribution. This intermediary system allows the defrosting evaporator to receive liquid refrigerant while maintaining proper pressure levels in the non-defrosting evaporators.
2Object-generated harmful factors
If reverse liquid defrosting is implemented, then ice removal on evaporator coils is achieved, but system complexity increases due to additional flow lines and control valves
Solution Approach 1:
The isolation valves and flow control valves serve multiple functions: they control refrigerant flow during normal operation, enable defrosting cycles by redirecting liquid refrigerant, and maintain pressure balance across different evaporator circuits. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The system uses reverse flow defrosting where liquid refrigerant flows through the evaporator in the opposite direction during defrosting cycles. This inversion of normal flow direction allows the evaporator to act as a heat exchanger for melting ice while the refrigerant absorbs heat from the surrounding environment, efficiently removing ice accumulation.
3Adaptability or versatility
If multiple evaporators operate at different evaporating pressures, then each evaporator can be optimized for its specific load, but maintaining compressor suction pressure becomes difficult during defrosting operations
Solution Approach 1:
The system employs dynamic flow control through adjustable valves that can adapt refrigerant distribution in real-time. During defrosting operations, the isolation valves and flow control valves dynamically adjust to maintain proper suction pressure at the compressor while allowing different evaporators to operate at their optimized pressures. This dynamic adjustment ensures system reliability despite varying operating conditions.
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 ensures effective defrosting of selected evaporators without pressure drops, enhances efficiency by using a second compression stage, and supports heat pump mobile systems 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 to release heat to dissolve the ice that has accumulated on the coil
Implementation Method 2
the liquid refrigerant which flows through it becomes sub-cooled
Implementation Method 3
by the use in addition of further flow lines, further check valves, an ejector, a vapor-liquid separator
Data Source
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.