Nucleate Boiling Engine Cooling for Cogeneration
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Solution Overview
Problem
Internal combustion engines face challenges in efficiently utilizing heat generated during electricity production due to low coolant temperatures, leading to uncontrolled boiling and reduced heat flux, which can damage engine components and result in inefficient heat transfer.
Innovation Solution
A cogeneration system that maintains nucleate boiling conditions in the engine cooling system using a vapor separator and coolant circulation pump, with a series of liquid nozzles to impinge high-velocity coolant at or near saturation pressure, ensuring stable nucleate boiling and preventing film boiling across all engine operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional convective liquid cooling is used, then engine structural integrity is maintained, but heat transfer rates are insufficient and heat is wasted
Solution Approach 1:
The patent utilizes nucleate boiling, a phase transition phenomenon, where coolant undergoes controlled vaporization and condensation cycles. Bubbles form at nucleation sites on heated surfaces, grow, and collapse, extracting heat through latent heat of vaporization. This phase transition mechanism enables significantly higher heat transfer coefficients compared to conventional single-phase liquid cooling, resolving the contradiction between heat transfer efficiency and engine reliability.
Solution Approach 2:
The invention changes the thermal parameters of the cooling system by operating the coolant near its saturation temperature rather than using subcooled liquid. By maintaining the coolant at or near boiling point and controlling the degree of superheat, the system achieves optimal nucleate boiling conditions. This parameter change from subcooled liquid cooling to saturation-temperature boiling cooling dramatically improves heat transfer rates while maintaining engine durability through controlled operation within the nucleate boiling regime.
2Loss of energy
If uncontrolled boiling is allowed, then heat transfer increases, but engine components are damaged and heat flux is reduced
Solution Approach 1:
The patent implements feedback control through carefully designed cooling system architecture including evaporators, condensers, and expansion devices that regulate coolant flow and pressure. The system monitors and maintains operating conditions within the nucleate boiling regime by controlling refrigerant charge, expansion valve opening, and compressor operation. This feedback mechanism prevents transition to film boiling or uncontrolled vapor lock, thereby avoiding engine damage while maintaining high heat transfer efficiency.
Solution Approach 2:
The invention employs dynamic control of cooling system parameters to adapt to varying engine loads and operating conditions. The refrigerant flow rate, pressure, and temperature are continuously adjusted to maintain optimal nucleate boiling conditions. This dynamic operation allows the system to respond to changing thermal demands while preventing harmful boiling regimes, resolving the contradiction between maximizing heat transfer and preventing component damage.
3Loss of energy
If high coolant flow rates are used, then heat transfer is improved, but parasitic pumping power increases
Solution Approach 1:
The patent exploits the phase transition of the coolant to achieve high heat transfer rates with minimal flow requirements. During nucleate boiling, the latent heat of vaporization provides intensive heat transfer without requiring high volumetric flow rates. The two-phase mixture of liquid and vapor bubbles naturally circulates through the engine cooling passages, absorbing heat efficiently. This phase-change mechanism dramatically reduces the pumping power needed compared to conventional single-phase liquid cooling systems that require high flow rates to achieve similar heat transfer.
4Loss of energy
If nucleate boiling is maintained, then heat transfer rates are enhanced, but system complexity increases
Solution Approach 1:
The patent employs a refrigeration cycle system that performs multiple functions: cooling the engine through nucleate boiling, recovering waste heat via evaporators, and providing climate control through condensers and expansion devices. This multi-functional approach integrates the nucleate boiling cooling system with the vehicle's existing HVAC system, reducing overall system complexity. The same refrigerant circuit serves both engine cooling and passenger compartment climate control, eliminating the need for separate cooling systems and reducing component count.
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 approach significantly reduces coolant flow rates and parasitic pumping power, achieves excellent temperature uniformity, and enhances heat transfer rates, maintaining engine structural integrity and efficiency while providing high-quality vapor for industrial or commercial processes.
Implementation Method 1
a cooling system comprising a cooling fluid adapted to circulate through the engine and to cool the engine under conditions of nucleate boiling in which at least 10 percent of the coolant exits the engine in a vapor phase
Implementation Method 2
a vapor separator adapted to separate the coolant that exits the engine into a vapor phase coolant and a liquid phase coolant
Implementation Method 3
a coolant circulation pump is provided to force the cooling fluid through the engine
Implementation Method 4
The thermal capacity of the coolant is derived from its latent heat of vaporization rather than from its much lower sensible heat capacity
Data Source
AI summary
A cogeneration system for generating electricity and process steam. The system includes an internal combustion engine having a shaft and a cooling system comprising a cooling fluid adapted to circulate through the engine and to cool the engine under conditions of nucleate boiling in which at least 10 percent of the coolant exits the engine in a vapor phase. It includes a vapor separator adapted to separate the coolant that exits the engine into a vapor phase coolant and a liquid phase coolant. The engine shaft drives an electric generator to provide electric power. A hot vapor line directs hot vapor exiting the vapor separator to a hot vapor process load. A coolant circulation pump is provided to force the cooling fluid through the engine, and a hot water line is provided to return hot water exiting the vapor separator to the coolant circulation pump. In preferred embodiments the system further includes an excess steam condenser for to collecting and condensing excess steam not needed by the hot vapor load, a condensate return tank adapted to store condensate from the hot vapor load and the excess steam condenser, and a condensate return line adapted to return condensate to the coolant recirculation pump.