Heat Medium Pump Control to Prevent Air-Conditioner Pipe Freezing
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Solution Overview
Problem
In air-conditioning systems, the heat medium can freeze when circulation is stopped, leading to pipe damage due to environmental conditions, as described in Patent Literature 1.
Innovation Solution
An air-conditioning apparatus with a refrigeration cycle and heat medium circuit that includes a compressor, refrigerant flow switching device, heat source side heat exchanger, expansion device, intermediate heat exchanger, pump, use side heat exchanger, flow switching valve, outdoor air temperature detection, and a controller that activates the pump when outdoor temperature drops below a predetermined level to prevent freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump is continuously activated to circulate the heat medium, then freezing of the heat medium is prevented, but energy consumption increases
Solution Approach 1:
The controller activates the pump in advance before the heat medium temperature reaches the freezing point, based on predetermined temperature thresholds and time intervals. This preliminary action prevents freezing while avoiding continuous operation, thereby reducing energy consumption.
Solution Approach 2:
The pump operates periodically rather than continuously, with activation determined by temperature conditions and time intervals since the last operation. This periodic operation maintains freezing prevention while significantly reducing overall energy consumption compared to continuous circulation.
2Reliability
If the pump is activated frequently to prevent freezing, then heat medium safety is improved, but the number of pump activations increases leading to higher energy use
Solution Approach 1:
The system activates the pump in advance based on predicted freezing conditions rather than waiting for actual freezing to occur. This reduces the frequency of activations while maintaining safety, as the pump runs only when conditions warrant intervention rather than responding to critical failures.
Solution Approach 2:
The controller uses feedback from temperature detection and timing information to intelligently determine when pump activation is necessary. This feedback mechanism optimizes activation frequency by considering both current temperature conditions and the elapsed time since the last operation, balancing safety with energy 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
Prevents heat medium freezing, reducing the number of pump activations and achieving energy savings by controlling the circulation based on outdoor temperature and elapsed time since the last pump operation.
Implementation Method 1
at least one intermediate heat exchanger configured to exchange heat between the heat source side refrigerant and a heat medium different from the heat source side refrigerant
Implementation Method 2
configured to allow the heat source side refrigerant to exchange heat with an indoor side refrigerant (heat medium)
Implementation Method 3
a compressor configured to compress a heat source side refrigerant
Implementation Method 4
an expansion device configured to regulate a pressure of the heat source side refrigerant
Implementation Method 5
a heat medium circuit that includes at least one pump configured to circulate the heat medium related to heat exchange in the intermediate heat exchanger
Implementation Method 6
the heat medium may freeze depending on environment in which the heat medium circuit is placed. If the heat medium has frozen, the heat medium will increase in volume
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An air-conditioning apparatus includes a refrigeration cycle that includes one or more intermediate heat exchangers 15 connected by pipes, the intermediate heat exchanger 15 being configured to exchange heat between a heat source side refrigerant and a heat medium different from the heat source side refrigerant, a heat medium circuit that includes at least one pump 21 configured to circulate the heat medium related to heat exchange in the intermediate heat exchanger 15, a use side heat exchanger 26 configured to exchange heat between the heat medium and air related to an air-conditioned space, and flow switching valves 22 and 23 configured to switch between passing the heated heat medium through the use side heat exchanger 26 and passing the cooled heat medium therethrough, the pump 21, the use side heat exchanger 26, and the flow switching valves 22 and 23 being connected by pipes, a ninth temperature sensor 40 configured to detect the temperature of outdoor air, and a controller 60 configured to, when determining during suspension of an operation related to air conditioning that the temperature detected by the ninth temperature sensor 40 is at or below a first predetermined temperature and a first predetermined period of time has elapsed since the pump 21 was stopped, perform control such that the pump 21 is activated to circulate the heat medium through the heat medium circuit.