Heat Engine Variable Expansion Valve Control
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Solution Overview
Problem
Heat engines with positive displacement expanders face sub-optimal efficiency due to mismatches between the overall volumetric expansion ratio and the built-in volume ratio (BIVR) caused by variable heat transfer, leading to under-expansion or over-expansion, resulting in energy losses.
Innovation Solution
A heat engine system with a variable expansion valve and a controller that monitors and adjusts the overall volumetric expansion ratio by varying the pressure drop in the working fluid, maintaining it within an optimal range corresponding to the BIVR, using a database or model to determine valve settings based on operating parameters such as dryness, pressure, and flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a positive displacement expander is used to achieve higher peak operational efficiency, then efficiency is improved, but the overall volumetric expansion ratio mismatches the built-in volume ratio due to variable heat transfer, causing under-expansion or over-expansion and energy losses
Solution Approach 1:
The patent applies a variable expansion valve that dynamically adjusts the inlet pressure of the working fluid to the positive displacement expander. This dynamic adjustment allows the overall volumetric expansion ratio to match the built-in volume ratio of the expander under varying heat transfer conditions, preventing under-expansion or over-expansion and eliminating the associated energy losses while maintaining high peak operational efficiency
Solution Approach 2:
The patent implements a control system that monitors operating parameters and uses feedback to adjust the variable expansion valve. This feedback mechanism ensures that the inlet dryness and overall volumetric expansion ratio are continuously optimized to match the expander's built-in volume ratio, resolving the mismatch caused by variable heat transfer and maximizing energy extraction efficiency
2Adaptability or versatility
If the overall volumetric expansion ratio is allowed to vary due to variable heat transfer, then adaptability to different operating conditions is improved, but expansion efficiency deteriorates due to mismatch with built-in volume ratio
Solution Approach 1:
The variable expansion valve dynamically adjusts the inlet conditions of the working fluid based on real-time operating parameters. This dynamic control maintains the overall volumetric expansion ratio matched to the built-in volume ratio across varying heat transfer conditions, achieving both adaptability and high expansion efficiency simultaneously
Solution Approach 2:
The patent changes the inlet dryness parameter of the working fluid by adjusting the variable expansion valve. This parameter change ensures that despite variations in heat transfer conditions, the overall volumetric expansion ratio remains optimized for the expander's built-in volume ratio, maintaining high expansion efficiency while adapting to different operating conditions
Data Source
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AI summary
There is disclosed a heat engine 10 comprising: a heat exchanger 12 to transfer he at from a heat source 100 to a working fluid; a positive displacement expander 16 configured to receive inlet working fluid from the heat exchanger 12 and discharge expanded working fluid as a multiphase fluid so that there is an overall volumetric expansion ratio between the expanded working fluid and the inlet working fluid which is a function of an inlet dryness of the inlet working fluid; a variable expansion valve 14 disposed between the heat exchanger 12 and the expander 16, the valve being configured to introduce a variable pressure drop in the working fluid to vary the inlet dryness; and a controller 30 configured to maintain the overall volumetric expansion ratio by controlling the valve 14 to compensate for variable heat transfer to or from the working fluid.