Outdoor Fan Control to Prevent Heat Exchanger Airflow Drop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing outdoor units of refrigeration apparatuses face challenges in maintaining air flow through the outdoor heat exchanger when the total blow rate of fans is reduced, leading to a decrease in the quantity of air passing through, which can affect the condensation capability and reliability of the compressor.
Innovation Solution
The implementation of a fan controller that transitions between operating states to manage the power supply of multiple outdoor fans, performing on/off control based on timers, electric current observations, and rotational speed measurements to maintain airflow and reduce blow rates smoothly, ensuring the condensation capability of the outdoor heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the total blow rate of outdoor fans is reduced to ensure high-low differential pressure in the compressor, then the compressor reliability is improved, but the quantity of air passing through the outdoor heat exchanger is reduced
Solution Approach 1:
The controller performs preliminary actions by monitoring fan rotational speeds and detecting when fans are approaching stoppage before actually stopping them. This allows the controller to preemptively adjust control strategies or activate backup fans to maintain airflow through the heat exchanger, preventing the harmful effect of airflow reduction while still enabling blow rate reduction for compressor protection.
Solution Approach 2:
The controller continuously monitors fan rotational speeds and uses this feedback to detect when fans are approaching stoppage. This feedback mechanism enables the controller to adjust the blow rate control strategy in real-time, maintaining adequate airflow through the heat exchanger while still reducing the total blow rate to protect the compressor's high-low differential pressure.
2Use of energy by moving object
If an outdoor fan is stopped or operated intermittently to lower the total blow rate, then the energy consumption is reduced, but air flow back through the stopped fan outlet reduces the effective air quantity through the heat exchanger
Solution Approach 1:
The controller applies preliminary anti-action by detecting when fan rotational speeds approach zero and preemptively taking corrective measures. This prevents the harmful backflow effect from occurring in the first place, maintaining effective airflow through the heat exchanger while still allowing intermittent operation to reduce energy consumption.
Solution Approach 2:
By continuously monitoring fan rotational speeds and providing feedback to the control system, the controller can detect the approach to stoppage and adjust operations to prevent backflow. This feedback loop enables energy-saving intermittent operation while maintaining effective heat exchanger airflow.
3Stress or pressure
If the blow rate is smoothly reduced during low blow rate demand, then the compressor high-low differential pressure is maintained, but the air flow through the heat exchanger may suddenly reduce when fans transition to stoppage
Solution Approach 1:
The controller performs preliminary detection of fan rotational speeds approaching stoppage and takes preemptive actions to maintain stable airflow. This prevents sudden airflow reductions that would occur if fans simply coasted to stop, thereby maintaining both the compressor's differential pressure and the heat exchanger's airflow stability.
Solution Approach 2:
The continuous monitoring of fan rotational speeds provides feedback that enables the controller to maintain stable airflow through the heat exchanger while smoothly reducing blow rate. The feedback mechanism detects approaching stoppage and triggers appropriate responses to prevent instability in the air flow composition.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is an outdoor unit of a refrigeration apparatus which can suppress a reduction in the total quantity of air passing through the outdoor heat exchanger, which is ensured by a plurality of outdoor fans, when the total blow rate of the fans is lowered. The outdoor unit comprises an outdoor heat exchanger (23), a first outdoor fan (28a) and a second outdoor fan (28b) for generating an air flow passing through the outdoor heat exchanger (23), and a fan controller. The fan controller transitions from a first operating state in which the first outdoor fan (28a) and the second outdoor fan (28b) operate, to a second operating state in which the first outdoor fan (28a) continues to operate and the power supply to the second outdoor fan (28b) is cut off, during low blow rate demand in which a low blow rate is desired. The fan controller, after transitioning to the second operating state, performs fan on/off control for turning the power supply to the first outdoor fan (28a) and the second outdoor fan (28b) on and off on the basis of a timer, observation of an electric current value relating to fan motors, or observation of the fan rotational speeds.