Loop Heat Pipe Startup Control Using Vapor Line Condensation
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Solution Overview
Problem
Loop heat pipes fail to start up efficiently when the evaporator is positioned below the condenser, leading to energy wastage and delayed cooling due to fixed heating times and varying working fluid distribution profiles, especially in portable devices where the positional relationship and attitude change.
Innovation Solution
A loop heat pipe system with a temperature sensor and controller to monitor and heat specific parts of the vapor line, ensuring efficient startup by detecting condensation changes and optimizing heating times based on temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the evaporator is positioned below the condenser to enable startup in certain configurations, then the loop heat pipe can be installed in apparatuses requiring this orientation, but the working fluid distribution becomes unstable and varies with time and attitude changes
Solution Approach 1:
The heater attached to the vapor line performs preliminary heating before the heat source is activated. This pre-heating action ensures that the vapor line temperature is sufficiently high to vaporize working fluid and initiate circulation, overcoming the gravitational challenge of evaporator-below-condenser configuration and enabling stable operation despite orientation variations.
2Ease of operation
If a fixed heating time is used to start up the loop heat pipe, then the startup process is simple to control, but energy is wasted and cooling starts later than necessary
Solution Approach 1:
A temperature sensor monitors the temperature of the vapor line or evaporator, and this temperature feedback is used by the controller to dynamically adjust the heater operation. The heating continues only until the temperature reaches a predetermined threshold, automatically stopping the heater to avoid unnecessary energy consumption while ensuring timely startup.
3Device complexity
If the heater is operated for a fixed duration, then the startup sequence is straightforward, but the cooling target activation is delayed and energy efficiency deteriorates
Solution Approach 1:
The controller continuously monitors temperature feedback from the sensor and adjusts the heater operation in real-time. This feedback mechanism enables the system to determine the exact moment when heating is sufficient, immediately activating the cooling target without unnecessary delays, thus reducing startup time while maintaining simple control logic.
4Reliability
If the vapor line is heated extensively to ensure startup, then reliable startup is achieved, but excessive energy is consumed
Solution Approach 1:
The temperature sensor provides continuous feedback to the controller, which stops the heater exactly when the predetermined temperature threshold is reached. This feedback-controlled approach ensures that heating continues long enough to guarantee reliable startup while automatically preventing any excessive heating that would waste energy, achieving optimal balance between reliability and 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
This solution allows for efficient startup of the loop heat pipe, reducing energy consumption and ensuring timely cooling by dynamically adjusting heating based on temperature changes, thus overcoming the limitations of fixed heating times and varying fluid distributions.
Implementation Method 1
an evaporator to evaporate working liquid (a liquid phase of a working fluid) by adsorbing heat from a heat source
Implementation Method 2
a condenser to condense vaporized working liquid (vapor phase of a working fluid) by radiating heat
Implementation Method 3
attach a heater to part of the vapor line (a part of the vapor line near the evaporator) and to heat, by using the heater, the part of the vapor line
Data Source
AI summary
A loop heat pipe system includes: a loop heat pipe (LHP) including an evaporator, a condenser, a vapor line, and a liquid; a temperature sensor to measure temperature of part of the LHP, a working fluid portion in which has different phases in a situation where the LHP functions as a heat transport device and in a situation where the LHP dose not function as a heat transport device and a liquid phase of the working fluid dose not exist in the evaporator; a heater to heat a heating target part of the vapor line; and a controller, in order to start the LHP, to turn on the heater, to monitor temperature of the heating target part using the temperature sensor, and to turn off the heater when detecting a change caused by condensation of a vapor phase of the working fluid in the monitored temperature.