Modular Plastic Thermosiphon Evaporator for MED Fouling
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Solution Overview
Problem
Existing evaporators in Multi Effect Distillation (MED) processes face challenges with fouling, scaling, and poor heat transfer efficiency due to metal materials' sensitivity and plastics' non-wetting properties, leading to suboptimal heat transfer and stability issues.
Innovation Solution
A modular evaporator design using plastic materials with a matrix configuration of longitudinal tubes and connectors, incorporating a thermosiphon effect for improved wetting and heat transfer, along with a vapour-liquid separation zone to enhance circulation and stability, allowing for efficient heat exchange and easy assembly/disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metal materials are used for heat transfer surfaces, then heat transfer efficiency is improved, but sensitivity to fouling and scaling increases
Solution Approach 1:
The patent changes the material parameter from metal to plastic, specifically selecting plastic materials with thermal conductivity between 0.1-0.5 W/mK. This parameter change resolves the contradiction by providing corrosion and scaling resistance while maintaining acceptable heat transfer performance through optimized wall thickness and heat exchange surface area.
Solution Approach 2:
The patent employs composite construction by combining plastic heat transfer elements with supporting structures. The plastic components provide fouling and scaling resistance, while the overall composite structure maintains mechanical strength and stability, resolving the reliability issue associated with pure plastic materials.
2Reliability
If plastic materials are used to prevent scaling, then resistance to fouling and scaling is improved, but heat transfer efficiency deteriorates due to low thermal conductivity
Solution Approach 1:
The patent optimizes the wall thickness parameter of plastic heat transfer elements to a specific range (0.5-5 mm) to compensate for low thermal conductivity. By adjusting this parameter, the design achieves acceptable heat transfer efficiency while maintaining the scaling resistance benefits of plastic materials.
Solution Approach 2:
The plastic heat transfer elements serve multiple functions: they provide scaling and fouling resistance, maintain structural stability, and enable efficient heat transfer when properly designed. This multi-functionality resolves the contradiction by making plastic materials viable for heat transfer applications despite their lower thermal conductivity compared to metals.
3Ease of manufacture
If plastic materials are used, then material cost is reduced and scaling is prevented, but wall thickness must be increased to maintain strength, reducing heat transfer efficiency
Solution Approach 1:
The patent optimizes wall thickness parameters to balance structural strength requirements with heat transfer efficiency. By carefully selecting wall thickness within the 0.5-5 mm range, the design achieves adequate mechanical strength while minimizing thermal resistance, thus maintaining heat transfer efficiency without requiring excessive material thickness.
Solution Approach 2:
The patent compensates for the lower thermal conductivity of plastic materials by increasing the heat transfer surface area through optimized geometric dimensions. This dimensional approach allows the use of thinner walls while maintaining overall heat transfer performance, resolving the contradiction between material cost savings and heat transfer efficiency.
4Ease of operation
If spray nozzles are used for liquid distribution, then liquid film formation is improved, but plugging occurs rapidly when liquid contains solids and scaling fragments
Solution Approach 1:
The patent removes spray nozzles from the system entirely, replacing them with alternative liquid distribution methods such as gravity-driven flow or simple distribution channels. This extraction of the problematic component eliminates the plugging issue while maintaining adequate liquid film formation through the simplified distribution mechanism.
Solution Approach 2:
The patent employs simple, easily replaceable distribution elements that are less prone to plugging. These simplified components can be quickly replaced if needed, providing a cost-effective solution that maintains reliability in applications with solid-containing liquids.
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 design achieves a high heat transfer area over volume ratio, reduces fouling and scaling risks, and maintains stability and strength, even with low wall thickness, making it suitable for industrial-scale use with corrosive media like seawater.
Implementation Method 1
A flow path for a second fluid is defined by a space enclosed between adjacent modules... The design achieves a high heat transfer area over volume ratio, reduces fouling and scaling risks, and maintains stability and strength
Implementation Method 2
The evaporator for heat exchange between fluids... exchanging heat from the first fluid to the second liquid and partially evaporating said second liquid
Implementation Method 3
separating vapour from the vapour-liquid mixture in a phase separation zone and returning the liquid to the liquid recycle zone
Implementation Method 4
partially evaporating said second liquid generating a vapour-liquid mixture
Data Source
AI summary
The invention relates to an evaporator (10) for heat exchange between fluids, comprising a housing (12) having at least one inlet (20; 27) and at least one outlet (26, 28; 29) for each fluid, the inlet and outlet for each fluid being connected to one another by a flow path (38; 58), the flow path (38) of a first fluid comprising multiple heat exchange modules (60) comprising at least one longitudinal hollow tube (36), wherein the modules (60) are arranged in a stack spaced apart from the housing (12) leaving free a gap (59), and wherein a module (60) is provided with at least one connector (50) for connecting to a co-operating connector of an adjacent module, such that the gap (59) between the housing and the stack defining at least a liquid recycle zone for containing the second fluid and a phase separation zone for separating a vapor phase and a liquid phase of the second fluid and the space (56) enclosed between adjacent modules in the stack defining a flow path (58) for a second fluid, parallel to the flow path (38) for the first fluid, are in fluid communication with each other.