Evaporator Fan Defrost Control for Transport Cooling Coils
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Solution Overview
Problem
Frost buildup on transport climate control system evaporator coils reduces cooling capacity and increases energy consumption, leading to potential damage during hot and humid conditions.
Innovation Solution
The system uses convection heat to defrost the evaporator coil by independently controlling at least two evaporator fans to distribute heat around the coil, preventing heated air from entering the climate-controlled space and using the heat to melt frost into water, which can be removed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional defrosting methods are used to remove frost buildup on the evaporator coil, then the frost is removed, but energy consumption increases and cooling capacity is reduced
Solution Approach 1:
The evaporator coil defrosts itself by utilizing its own stored thermal energy. The coil's thermal mass and retained heat from normal operation are sufficient to melt the frost buildup without requiring external heating elements or additional energy input, making the defrosting process self-service and energy-efficient
Solution Approach 2:
The frost buildup, which is normally harmful to cooling performance, is converted into a beneficial thermal reservoir. The phase change from solid to liquid during defrosting absorbs heat from the coil's thermal storage, and the resulting water can be drained away, leaving the coil clean and ready for efficient operation without energy penalty
2Reliability
If the evaporator coil is heated to defrost the frost, then the frost melts and can be removed, but the heated air may enter the climate-controlled space causing temperature fluctuations
Solution Approach 1:
The harmful effect of heated air entering the climate-controlled space is eliminated by extracting or isolating the defrosting process to the evaporator coil itself. The coil's internal thermal energy is utilized, and the defrosting occurs contained within the coil structure, preventing any temperature disruption to the conditioned environment
Solution Approach 2:
The evaporator coil acts as an intermediary that stores and releases thermal energy in a controlled manner. Rather than directly heating air that could enter the climate-controlled space, the coil's thermal mass mediates the defrosting process, transferring heat internally to melt frost while maintaining stable temperatures in the conditioned space
3Use of energy by moving object
If frost buildup is allowed to accumulate on the evaporator coil, then energy consumption is reduced temporarily, but cooling capacity decreases and damage may occur
Solution Approach 1:
The system implements periodic self-defrosting cycles based on monitored conditions such as runtime duration, temperature differentials, or frost detection. This periodic action prevents excessive frost accumulation that would harm cooling capacity, while minimizing the frequency and duration of defrost events to maintain energy efficiency and productivity
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 method efficiently defrosts the evaporator coil without directly heating the frost, reducing energy consumption and preventing damage, while maintaining the cooling capacity of the transport climate control system.
Implementation Method 1
the controller independently controls the at least two fans to move the air around the evaporator coil in controlled directions so that heat from one section of the evaporator coil is used to convectively heat the inlet of the evaporator coil
Implementation Method 2
the evaporator that absorbs heat from a climate controlled space and evaporates the working fluid
Implementation Method 3
a compressor that compresses a working fluid passing through the transport climate control circuit
Implementation Method 4
using the heat to melt frost into water, which can be removed
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The transport climate control circuit includes a compressor, an evaporator and at least two fans. The transport climate control circuit also includes a controller for controlling the transport climate control circuit and for defrosting the evaporator coil. When a defrost event is triggered, the controller instructs the transport climate control circuit to supply heat to or around one section of the evaporator coil (3030), and independently controls each of the at least two fans (3010,3020) to move the air around the evaporator coil in a controlled direction so that heat from the one section of the evaporator coil is used to convectively heat the inlet of the evaporator coil. Damper 3040, heating device 2050.