Closed-Cycle Heat Transfer with Membrane Expansion Pressure Control
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Solution Overview
Problem
Closed thermodynamic devices like thermosyphons and heat pipes face challenges in maintaining efficiency due to the presence of non-condensable gases, which reduce heat transfer efficiency and affect pressure/temperature characteristics, especially when there is limited headroom requiring the condenser and evaporator to be at the same level, necessitating the exclusion of air and ensuring no vacuum conditions.
Innovation Solution
Incorporating an expansion device with a flexible membrane chamber connected to the fluid ducts to compensate for vapor phase expansion, allowing for controlled gas pressure adjustment and additional condensers to manage increased pressure and temperature, ensuring efficient heat transfer without vacuum conditions and non-condensable gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the condenser and evaporator are positioned at the same level to save headroom, then the device complexity is reduced and installation space is optimized, but the reliability of gravity-based condensate return is compromised
Solution Approach 1:
An expansion device is introduced as an intermediary component between the evaporator and condenser. This device uses gas pressure to actively push condensate through the expansion membrane, replacing the passive gravity-based return mechanism and enabling reliable operation at same-level configurations
Solution Approach 2:
The system transitions from gravity-based liquid return to pressure-driven liquid return by introducing gas pressure through the expansion device. The gas pressure acts on the expansion membrane to force condensate through the duct, enabling same-level evaporator-condenser configuration
2Quantity of substance
If the system is charged under vacuum to exclude non-condensable gases, then the purity of the working fluid is improved, but the risk of air ingress through leakage during non-operating conditions increases
Solution Approach 1:
The system operates at atmospheric pressure rather than vacuum, fundamentally changing the pressure parameter. This eliminates the driving force for air ingress while maintaining working fluid purity, as the expansion device regulates pressure to prevent vacuum formation during non-operating conditions
Solution Approach 2:
The expansion device acts as a pressure buffer that prevents the system from entering vacuum conditions during non-operating periods. By maintaining atmospheric pressure as a baseline, it cushions against the risk of air leakage that would occur under vacuum conditions
3Device complexity
If a fixed volume of working fluid is used in the system, then the system simplicity is maintained, but the ability to compensate for vapor phase expansion is limited
Solution Approach 1:
The expansion device introduces dynamic pressure regulation capability to the system. The gas pressure within the expansion device adjusts based on vapor phase expansion, automatically compensating for volume changes and maintaining reliable pressure management without requiring complex fluid volume control mechanisms
Solution Approach 2:
The system transitions from fixed fluid volume to dynamic pressure compensation. The expansion device changes the pressure parameter dynamically in response to vapor phase expansion, enabling the system to accommodate volume changes while maintaining reliability
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
The expansion device effectively manages vapor phase expansion, maintains efficient heat transfer by exposing additional heat transfer surfaces, and prevents air ingress by maintaining atmospheric pressure, enhancing system reliability and efficiency.
Implementation Method 1
compensate for expansion of a fluid vapour phase in at least the first fluid duct
Implementation Method 2
a regulating valve is disposed between the at least one further condenser and the second fluid duct
Implementation Method 3
a vessel divided internally into enclosed separate chambers by a flexible membrane such that a first said chamber is in communication with the second fluid duct and a second said chamber is isolated therefrom to contain a gas
Implementation Method 4
a first condenser connected to the first fluid duct and to the second fluid duct to receive working fluid in a vapour phase
Implementation Method 5
the vaporised working fluid condensing against a cooling medium
Implementation Method 6
A fixed volume of heat transfer fluid within a closed system is vaporised by application of heat in an evaporator
Implementation Method 7
heat is transferred principally via latent heat evaporation
Implementation Method 8
a pump may be used to return the condensate to the evaporator
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A closed cycle heat transfer device comprising a boiler (10) and a condenser (13), the condenser being used to recover useful heat by latent heat evaporation. A circuit defined by the boiler (10), condenser (13) and ducts (12, 15) is to be liquid-filled at a pressure just above atmospheric pressure. An expansion device (16) maintains the working pressure in the circuit but will receive excess condensate in a liquid phase to compensate for expansion of the working fluid vapour which passes from the boiler (10) to the condenser (13). The expansion chamber contains a movable or flexible member which, when working liquid is received in the chamber, is displaced to compress a gas in the chamber.