Sub-Zero Air Conditioner Coil Switching to Prevent Frost Blockage
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Solution Overview
Problem
Conventional air conditioners face issues with ice accumulation when cooling air to sub-zero dew points, requiring defrost cycles that increase energy consumption and maintenance costs, and are not cost-effective or reliable for continuous operation.
Innovation Solution
An energy-efficient air conditioner design featuring multiple cooling coils, a refrigeration circuit, and a control circuit to maintain a steady air flow at sub-zero temperatures without external heating, using precooling, heat recovery, and reheating coils to prevent ice formation, allowing continuous operation below zero degrees Celsius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air is cooled to sub-zero dew point in conventional air conditioners, then air conditioning capability is improved, but ice accumulates on the cooling coil blocking air passage
Solution Approach 1:
The patent implements periodic reversal of refrigerant flow direction through the cooling coils. The refrigerant flow is alternately directed through first cooling coils and second cooling coils in successive time periods. This periodic action prevents ice accumulation by ensuring that when ice forms on one set of coils, the other set remains ice-free and can handle the air conditioning load, thereby maintaining continuous reliable operation at sub-zero dew points
Solution Approach 2:
The cooling system is divided into multiple independent cooling coil sets (first cooling coils and second cooling coils) that can operate independently. This segmentation allows the system to switch between different coil sets, preventing complete blockage of air passage even when one set becomes iced over
2Reliability
If defrost cycle is implemented to remove ice, then air passage is cleared, but energy consumption increases and temperature control is disrupted
Solution Approach 1:
The patent maintains continuous air conditioning operation by switching between multiple cooling coil sets rather than interrupting the cooling process for defrost cycles. The refrigerant flow is continuously directed through different coil sets in a periodic manner, ensuring that air cooling never stops and temperature control remains uninterrupted, thereby eliminating the energy-wasting defrost cycles
Solution Approach 2:
The control system acts as an intermediary that manages refrigerant flow distribution between multiple cooling coil sets. By intelligently directing refrigerant flow through different coils at different times, the control system prevents ice accumulation without requiring active defrosting, thus avoiding the energy consumption and temperature disruption associated with traditional defrost cycles
3Reliability
If external heating is used to defrost the coil, then ice is removed, but the air temperature rises above design specification
Solution Approach 1:
The system uses periodic reversal of refrigerant flow direction instead of external heating for defrosting. By alternately switching refrigerant flow between first and second cooling coils, the system prevents ice accumulation through continuous cooling action on alternating coil sets, thereby maintaining air temperature within design specifications without the temperature spikes caused by external heating methods
4Temperature
If chemical de-humidification unit is used to provide sub-zero air temperature, then sub-zero cooling capability is achieved, but energy consumption increases significantly
Solution Approach 1:
The patent recovers heat from the refrigerant by directing it through heat recovery coils that pre-cool incoming air before it reaches the main cooling coils. This heat recovery process reduces the overall energy consumption by utilizing the thermal energy that would otherwise be wasted, enabling sub-zero air temperature provision with lower energy input compared to chemical de-humidification methods
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 system provides a continuous, frost-free supply of air at sub-zero dew points with reduced energy consumption and maintenance, ensuring reliable operation and lower costs compared to traditional air conditioners.
Implementation Method 1
a refrigeration circuit comprising at least one compressor having condenser coil, said refrigeration circuit further comprises an electric motor driven fan for cooling said condenser coil
Implementation Method 2
plurality of heat recovery coils to recover heat from precooling coils
Implementation Method 3
at least one compressor having condenser coil
Data Source
AI summary
The present invention provides an energy efficient air conditioner that can provide a continuous supply of air at dew point that is several degrees Celsius below zero, without requiring a defrost cycle. The air conditioner in accordance to present invention comprises a plurality of cooling coils with interconnecting refrigerant piping, refrigeration circuit consisting of compressor and condenser coils, control circuit and one or more electric motor driven centrifugal fan. The present invention uses two cooling systems. The first cooling system having single coil cools the air to a temperature just above zero deg. C., say four deg. C. so that the second stage gets a steady supply of cold air. The second stage has two coils, each being half the size of the first stage coil, thus taking half the air from it so that all the air from stage 1 passes through stage 2. In operation, only one coil of the second stage is active arid chills the air going through it to say minus 14 Deg. C. The other coil, being inactive, passes on the +4 Deg. C. air coming from the first stage. In order to prevent the active coil from icing up, a control circuit diverts the refrigerant to the second coil within a period short enough to prevent any significant ice build up in that coil. This goes on so that the total air flow is a steady 50% mixture of air at 4 Deg. C. and minus 14 deg. C. This works out to minus 5 Deg. C. at the output.