Evaporator Defrost Using Hot-Gas Flow in Selected Conduits
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Solution Overview
Problem
Conventional evaporator defrosting methods in refrigeration systems are inefficient, requiring substantial heat application over a short period while avoiding environmental heating, and often increase operational costs due to the need for additional defrost apparatus.
Innovation Solution
A method involving directing high-pressure, high-temperature hot gas refrigerant through specific conduits of the evaporator during defrosting, utilizing existing refrigerant from the circuit to provide heat without significantly increasing ambient temperature, and using sensors for automatic defrost initiation and termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional defrosting methods are used to remove ice accumulation, then the evaporator can be defrosted, but the defrosting process takes too long and heats the environment
Solution Approach 1:
The evaporator conduits are divided into two groups: a first group of conduits for normal refrigerant flow during cooling mode, and a second group of conduits specifically for directing hot gas refrigerant during defrost mode. This segmentation allows targeted heating of only the evaporator surfaces requiring defrosting, rather than heating the entire evaporator and surrounding environment, thereby increasing defrosting speed while maintaining environmental temperature stability.
Solution Approach 2:
Hot gas refrigerant is directed through specific second group conduits that are positioned to contact only the ice-covered portions of the evaporator. This local application of thermal energy concentrates the defrosting action precisely where needed, improving defrosting efficiency without unnecessarily heating adjacent areas or the overall environment.
2Productivity
If additional defrost apparatus are added to speed up defrosting, then defrosting efficiency improves, but device complexity and operational costs increase
Solution Approach 1:
The refrigeration circuit's existing compressor and refrigerant distribution system perform dual functions: during normal operation, they provide cooling through the first group of conduits; during defrost operation, the same compressor generates hot gas that is redirected through the second group of conduits to defrost the evaporator. This multi-functionality eliminates the need for separate defrosting equipment, maintaining high defrosting efficiency while avoiding increased device complexity and operational costs.
Solution Approach 2:
The refrigeration system uses its own compressed refrigerant gas to provide the heat necessary for defrosting. The compressor, which normally compresses refrigerant for cooling, also generates the hot gas required for defrosting by controlling refrigerant flow paths. This self-service approach allows the system to defrost itself using existing components, avoiding additional apparatus and reducing operational costs.
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 rapid and efficient defrosting of the evaporator, maintaining environmental temperature stability and reducing operational costs by leveraging the refrigeration circuit's existing components and energy.
Implementation Method 1
directing hot gas refrigerant through only a portion of the refrigerant conduits of the evaporator for defrosting the evaporator
Implementation Method 2
The hot gas refrigerant can be directed through the evaporator within a core portion thereof, i.e. a portion which is typically within the ice layer to be removed during the defrost cycle
Data Source
AI summary
Method for defrosting an evaporator in a refrigeration circuit (2) for circulating a refrigerant in a predetermined flow direction, the refrigeration circuit (2) comprising in flow direction a compressor unit (4), a heat-rejecting heat exchanger (6), an expansion device (12) and an evaporator (14), wherein the evaporator (14) comprises at least two refrigerant conduits (42; 44) and the method comprises the following steps: (a) operating the refrigeration circuit (2) in the normal cooling mode where the refrigerant exiting the heat-rejecting heat exchanger (6) flows through the expansion device (12) and through the evaporator (14) and towards the compressor unit (4); (b) terminating the cooling mode by interrupting the flow of the refrigerant exiting the heat-rejecting heat exchanger (6) into the evaporator (14); and (c) directing hot gas refrigerant through only a portion of the refrigerant conduits (42; 44) of the evaporator (14) for defrosting the evaporator (14).