Drain-Back Solar Circuit Pump Start-Up Against Pipe Freezing
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Solution Overview
Problem
Solar thermal circuits face damage from freezing fluids in the second line section due to low temperatures, as existing systems fail to adequately prevent fluid freezing, leading to reduced operational hours and increased maintenance costs.
Innovation Solution
A pump start-up program that gradually introduces fluid into the second line section, monitors return flow temperature, and adjusts pumping parameters to prevent freezing, including the option to deactivate the pump if freezing risk is detected, and utilizes existing components with minimal additional costs or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump is activated to fill the second line section with fluid, then the solar collector can generate heat, but the fluid freezes in the subcooled pipelines causing damage
Solution Approach 1:
The control unit checks the temperature of the second line section before activating the pump. If the temperature is below the freezing point, the pump activation is prevented in advance, avoiding the harmful freezing effect before it can occur. This preliminary temperature check resolves the contradiction by preventing pump operation under dangerous temperature conditions.
Solution Approach 2:
A temperature sensor continuously monitors the temperature in the second line section and provides feedback to the control unit. The control unit uses this feedback to dynamically adjust pump operation, activating the pump only when temperatures are safe and preventing activation when freezing conditions exist. This closed-loop feedback system resolves the contradiction by adapting pump operation to real-time temperature conditions.
2Reliability
If the second line section is emptied to prevent freezing, then damage is avoided, but the system cannot operate when outside temperatures are low
Solution Approach 1:
The temperature sensor provides continuous feedback about the thermal state of the second line section. Based on this feedback, the control unit intelligently decides whether to activate the pump or keep it deactivated, allowing the system to operate during safe low temperatures while protecting against freezing when temperatures are dangerous. This resolves the contradiction by enabling operation whenever conditions permit rather than permanently emptying the system.
Solution Approach 2:
The system transitions from a static state (permanently empty or permanently filled) to a dynamic state where the pump activation status changes based on temperature conditions. The control unit dynamically adjusts the system state by activating or deactivating the pump according to real-time temperature readings, allowing the system to adapt to varying environmental conditions and maximize operational hours while maintaining protection.
3Ease of operation
If the pump is activated without temperature monitoring, then the system is simpler to operate, but large parts of the second line section are already filled with fluid and damaged by freezing
Solution Approach 1:
The temperature sensor and control unit create an automated feedback system that monitors temperature and controls pump activation. This eliminates the need for complex manual temperature checks and decision-making by the operator, maintaining ease of operation while preventing freezing damage through automated intelligent control. The system appears simple to operate but incorporates sophisticated temperature-based protection.
Solution Approach 2:
The system performs its own temperature monitoring and pump control decisions automatically without requiring external intervention. The control unit uses the temperature sensor data to self-regulate pump operation, making the system both simple to operate (no manual monitoring needed) and effective at preventing freezing damage through autonomous temperature-based control.
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 frost damage by recognizing freezing risks early, increases operational hours of solar circuits, and allows for efficient heat generation even in low temperatures without additional hardware, making it cost-effective and retrofittable.
Implementation Method 1
a pump (11) for conveying fluid (F) is arranged in the first line section (10)
Implementation Method 2
a solar collector (41) is provided in the second line section (20) for heating the fluid (F) flowing through it
Implementation Method 3
for heating the fluid (F) flowing through it
Implementation Method 4
the first line section (10) is thermally coupled to a heat accumulator (52) in front of the pump (11)
Implementation Method 5
the fluid (F) often freezes in the second line section (20), which can cause damage
Implementation Method 6
water has a density anomaly in the temperature range from 0 °C to 4 °C and expands in the frozen solid phase
Data Source
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AI summary
Solar-heat circuits having a drain-back system can freeze during filling of a line section which is arranged in the exterior region, although a high temperature prevails in the solar collector. This freezing is to be prevented. The method according to the invention comprises activation of a pump starting program in the case of a pump activation. Said program comprises stipulation of a fluid quantity to be delivered; a fluid introduction sequence, containing the delivery of the stipulated fluid quantity from a first line section into an unfilled second line section in the exterior region; and a fluid return sequence, containing determination of a return temperature of the returning fluid. Subsequently, the stipulation of the delivery quantity is increased and either the above-mentioned steps are repeated if the return temperature is greater than or equal to a limiting return temperature and the increased stipulation of the fluid quantity to be delivered is less than or equal to a limiting quantity; or the pump starting program is deactivated and standard operation of the pump is started if the increased stipulation of the delivery quantity is greater than the limiting quantity; or pump starting program and pump are deactivated and the stipulation of the fluid quantity to be delivered is reset if the return temperature undershoots the limiting return temperature.