Shipboard Cold Recovery Heat Exchange Using an Intermediate Fluid
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Solution Overview
Problem
Small heat exchangers in cryogenic power generation systems, such as those on ships, are prone to blockage due to solidification of heat exchange media, which compromises their reliability.
Innovation Solution
A cold energy recovery system with a working fluid circulation line, intermediate heat medium circulation line, and multiple heat exchangers is employed, using fluids with lower freezing points to prevent solidification and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small heat exchanger is used in a ship-based cryogenic power generation system, then the system size is reduced and adaptability to ship constraints is improved, but the reliability deteriorates due to blockage from solidification of heat exchange media
Solution Approach 1:
The patent introduces an intermediate heat exchange fluid (propane or butane) that circulates between the LNG and the heat exchange fluid in a closed loop. This intermediary fluid has a lower freezing point than water and acts as a mediator to transfer heat without solidifying at the operating temperatures, thereby preventing blockage in the compact heat exchanger while maintaining its small size.
Solution Approach 2:
The patent changes the physical parameters of the heat exchange medium by using fluids with lower freezing points (propane, butane) instead of water. By selecting working fluids with appropriate phase change characteristics and freezing points below the minimum operating temperature, the system prevents solidification and maintains reliable heat exchange in the compact configuration.
2Device complexity
If water is used as the heat exchange medium, then the system is simple and cost-effective, but the reliability deteriorates because water solidifies at low temperatures and blocks the heat exchanger
Solution Approach 1:
The patent replaces water with an intermediate heat exchange fluid (propane or butane) that serves as a mediator between the LNG and the heat exchange process. This intermediary fluid remains liquid at the operating temperatures and does not solidify, thereby preventing blockage while maintaining a relatively simple closed-loop circulation system.
Solution Approach 2:
The patent changes the fundamental parameter of the heat exchange medium from water to fluids with lower freezing points (propane, butane). This parameter change ensures that the heat exchange medium remains fluid at sub-zero temperatures, eliminating the solidification problem and maintaining system reliability without significantly increasing complexity.
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 system effectively suppresses blockage in heat exchangers by maintaining heat exchange media above their freezing points, enhancing the reliability and efficiency of cold energy recovery.
Implementation Method 1
a first heat exchanger which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line
Implementation Method 2
a second heat exchanger disposed downstream of the first heat exchanger on the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid flowing through the working fluid circulation line and the intermediate heat medium flowing through the intermediate heat medium circulation line
Implementation Method 3
a third heat exchanger which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system
Implementation Method 4
an auxiliary heat exchanger disposed downstream of the first heat exchanger on the liquefied gas supply line, the auxiliary heat exchanger being configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line and a heating medium circulating in the cold energy recovery system
Implementation Method 5
a working fluid circulation line which is configured to circulate a working fluid having a lower solidifying point than water
Implementation Method 6
using fluids with lower freezing points to prevent solidification and improve reliability
Data Source
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AI summary
This cold recovery system is installed in a ship having a liquefied gas storage device that stores a liquid liquefied gas, the system comprising: a working fluid circulation line that causes a working fluid having a lower freezing point than water to circulate therethrough; a cold recovery device that includes a turbine driven by the working fluid; a first heat exchanger that exchanges heat between the liquefied gas and the working fluid; an intermediate heat medium circulation line that causes an intermediate heat medium having a lower freezing point than water to circulate therethrough; a second heat exchanger that is provided on the downstream side of the working fluid circulation line with respect to the first heat exchanger, and exchanges heat between the working fluid and the intermediate heat medium; and a third heat exchanger that exchanges heat between the intermediate heat medium and heated water introduced from the outside of the cold recovery system.