Mass Management System Pressure Control
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Solution Overview
Problem
Industrial heat engine systems face inefficiencies due to the venting of working fluid, leading to increased operating costs and reduced pressure management, especially when dealing with low-grade heat and supercritical carbon dioxide cycles, where maintaining optimal pressure is crucial to avoid cavitation and maximize power generation.
Innovation Solution
A heat engine system with a mass management system (MMS) that utilizes a controller to regulate pressure by strategically opening and closing valves to manage the flow of working fluid, including a tank, pump, heat exchanger, and offload terminal, ensuring the low-side pressure remains within a safe range, thereby minimizing fluid venting and optimizing system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional venting systems are used to maintain pressure, then pressure management is achieved, but working fluid is continuously vented leading to increased operating costs
Solution Approach 1:
The mass management system implements a feedback control mechanism where the controller continuously monitors low-side pressure and adjusts valve positions accordingly. When pressure drops below the threshold, the controller opens the first valve to allow working fluid from the tank to replenish the system, and closes the second valve to prevent venting. This closed-loop feedback system maintains pressure within acceptable ranges while minimizing working fluid loss.
Solution Approach 2:
The system uses the existing high-side pressure working fluid to automatically replenish the low-side pressure without requiring external intervention or continuous venting. The mass management system enables the system to self-regulate by transferring fluid from the tank to the low-side, and from the high-side to the tank, creating a self-sustaining pressure management mechanism that prevents working fluid loss.
2Productivity
If low-side pressure is maintained at the lowest safe level to maximize power generation, then system efficiency is improved, but risk of cavitation increases
Solution Approach 1:
The controller continuously monitors low-side pressure and compares it to a pre-set threshold value. When pressure approaches the cavitation risk zone, the controller automatically opens the first valve to replenish working fluid from the tank, thereby maintaining pressure above the cavitation threshold. This feedback mechanism allows the system to operate at the optimal pressure boundary without exceeding safety limits.
Solution Approach 2:
The system maintains a reservoir of working fluid in the tank at high-side pressure, prepared in advance for rapid replenishment. When low-side pressure drops, the pre-positioned fluid in the tank can immediately be transferred to prevent cavitation, rather than waiting for external replenishment. This preliminary preparation enables rapid response to pressure changes.
3Productivity
If high-side pressure is increased to improve power generation, then system efficiency increases, but pressure ratio control becomes more difficult
Solution Approach 1:
The mass management system divides pressure control into two independent segments: high-side pressure management through the second valve controlling fluid transfer to the tank, and low-side pressure management through the first valve controlling replenishment from the tank. This segmentation allows each valve to be controlled independently based on its respective pressure conditions, simplifying the overall control strategy while maintaining optimal pressure ratio for power generation.
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 MMS effectively maintains desired pressure ranges, reduces fluid venting, and enhances the efficiency of the heat engine system in generating electricity from waste heat streams, particularly in supercritical carbon dioxide cycles, by actively controlling the flow and pressure of the working fluid.
Implementation Method 1
capturing or otherwise absorbing thermal energy of the waste heat stream with one or more heat exchangers
Implementation Method 2
the pump being configured to receive the working fluid from the condenser and to pressurize the working fluid
Implementation Method 3
The thermal energy is transformed to mechanical energy by a power turbine
Data Source
AI summary
Embodiments of the invention generally provide a heat engine system, a mass management system (MMS), and a method for regulating pressure in the heat engine system while generating electricity. In one embodiment, the MMS contains a tank fluidly coupled to a pump, a turbine, a heat exchanger, an offload terminal, and a working fluid contained in the tank at a storage pressure. The working fluid may be at a system pressure proximal an outlet of the heat exchanger, at a low-side pressure proximal a pump inlet, and at a high-side pressure proximal a pump outlet. The MMS contains a controller communicably coupled to a valve between the tank and the heat exchanger outlet, a valve between the tank and the pump inlet, a valve between the tank and the pump outlet, and a valve between the tank and the offload terminal.