Refrigeration Suction-Pipe Heating to Suppress Dry Ice Formation
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Solution Overview
Problem
Refrigeration apparatuses using carbon dioxide (R744) face issues with carbon dioxide turning into dry ice at low temperatures, leading to pressure loss and pipe clogging, which prevents refrigerant circulation and causes temperature rises.
Innovation Solution
A refrigeration apparatus with a mixed refrigerant containing a first refrigerant with a boiling point between −89.0° C. and −78.1° C. and carbon dioxide (R744), along with a heater to heat the suction pipe and a capillary tube structure that enhances heat exchange, preventing dry ice formation by using a second refrigerant soluble in carbon dioxide at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon dioxide (R744) is used as refrigerant to reduce GWP and improve thermal conductivity, then refrigeration performance is improved, but carbon dioxide solidifies at low temperatures causing pipe clogging
Solution Approach 1:
The patent changes the temperature parameter of the suction pipe by introducing a heater that raises the suction pipe temperature to above the dew point temperature of carbon dioxide. This parameter change prevents carbon dioxide from solidifying in the suction pipe while maintaining the refrigeration performance benefits of using R744 as refrigerant.
Solution Approach 2:
The heater acts as an intermediary device between the cold refrigerant and the suction pipe wall. It introduces thermal energy to the suction pipe, creating a thermal barrier that prevents the refrigerant temperature from dropping below the carbon dioxide dew point, thereby preventing dry ice formation without affecting the overall refrigeration cycle.
2Productivity
If double pipe structure is used to enhance heat exchange between suction pipe and capillary tube, then refrigeration efficiency is improved, but pressure loss increases leading to dry ice formation
Solution Approach 1:
The patent applies local quality by selectively heating only the suction pipe portion where dry ice formation is most likely to occur, rather than heating the entire refrigeration system. This localized heating approach maintains high refrigeration efficiency in the evaporator while preventing pressure loss and dry ice formation in the suction pipe.
Solution Approach 2:
The heater provides preliminary anti-action by preemptively warming the suction pipe before carbon dioxide can solidify. This prevents the harmful effect of dry ice formation before it can occur, maintaining smooth refrigerant flow and preventing pressure loss that would otherwise reduce refrigeration 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
The solution effectively prevents carbon dioxide from turning into dry ice, ensuring stable refrigeration performance and efficient refrigerant circulation, maintaining low temperatures without pipe clogging.
Implementation Method 1
A heater that heats at least a portion of a suction pipe through which the refrigerant that returns from the evaporator to the compressor passes is provided
Implementation Method 2
causes the refrigerant to evaporate in an evaporator to exhibit a refrigeration effect
Implementation Method 3
causes the refrigerant to evaporate in an evaporator to exhibit a refrigeration effect
Implementation Method 4
decompresses the refrigerant with a capillary tube
Implementation Method 5
decompresses the refrigerant with a capillary tube
Implementation Method 6
a refrigerant circuit that condenses a refrigerant discharged from a compressor
Data Source
AI summary
A refrigeration apparatus includes: a refrigerant circuit that condenses a refrigerant discharged from a compressor, decompresses the refrigerant with a capillary tube, and causes the refrigerant to evaporate in an evaporator to exhibit a refrigeration effect, wherein, as the refrigerant in the refrigerant circuit, a mixed refrigerant containing a first refrigerant having a boiling point in an ultralow temperature range of not less than −89.0° C. and not more than −78.1° C. and carbon dioxide (R744) is enclosed, and a heater that heats at least a portion of a suction pipe through which the refrigerant that returns from the evaporator to the compressor passes is provided.