Multiple-Effect Multi-Train Desalination for Latent Heat Recovery
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Solution Overview
Problem
Current multi-effect desalination (MED) devices suffer from high specific energy consumption due to limited recycling of latent heat, mineral precipitation issues, and high salinity levels in later effects, leading to inefficient water production.
Innovation Solution
The multi-effect multi-train desalination (MEMTD) device employs High Transition Region Density Heat Exchangers (HTRDHE) with alternating microchannels and inverse symmetry meniscus design to enhance latent heat exchange, coupled with sensible heat exchangers between trains, reducing thermal gradients and increasing the number of effects to 30, and using residual vapor below 70°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of evaporator-condenser effects is increased to improve water production capacity, then productivity increases, but specific energy consumption increases due to limited latent heat recycling
Solution Approach 1:
The system divides the evaporation process into multiple separate trains of effects (first train, second train, third train) with different temperature ranges. Each train operates independently with its own heat exchangers, allowing optimized heat recovery within each segment and reducing the thermal gradient requirements that limit traditional single-train systems.
Solution Approach 2:
The patent implements nested heat exchangers where condenser tubes are positioned inside evaporator chambers and vice versa, creating concentric heat transfer paths. This nested configuration allows maximum latent heat recovery by placing the condenser of one effect directly within the evaporator of another, enabling efficient thermal coupling between successive effects.
2Device complexity
If the temperature difference per effect is increased to reduce the number of effects needed, then device complexity decreases, but manufacturing precision and heat exchange efficiency worsen
Solution Approach 1:
Each heat exchanger is designed with locally optimized geometry including specific tube diameters (20-50mm for evaporators, 10-30mm for condensers), wall thicknesses (1-5mm), and arrangement configurations tailored to the specific temperature range and heat transfer requirements of each effect. This local optimization maintains high efficiency even with small temperature differences of 2-5°C per effect.
Solution Approach 2:
The patent transitions from conventional shell-and-tube heat exchangers to a nested concentric configuration where tubes are positioned inside chambers, adding a radial dimension to heat transfer. This dimensional change increases the heat transfer surface area and improves thermal coupling efficiency, allowing smaller temperature differences while maintaining or enhancing heat exchange performance.
3Reliability
If residual vapor temperature is limited to below 70°C to prevent mineral precipitation, then reliability improves, but productivity decreases due to reduced thermal energy availability
Solution Approach 1:
The system segments the temperature range by creating multiple trains of effects, with the first train operating at lower temperatures (vapor below 70°C) to avoid mineral precipitation, and subsequent trains operating at progressively higher temperatures. This segmentation allows the system to utilize the full thermal energy spectrum while maintaining reliable operation in each segment.
Solution Approach 2:
The patent changes the operating parameters of each effect train, specifically controlling the vapor temperature, pressure, and concentration levels to remain within ranges that prevent mineral precipitation. By adjusting these parameters across multiple trains rather than using a single high-temperature system, the patent achieves both reliability and enhanced productivity.
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
MEMTD achieves a threefold increase in water production capacity from a given mass flow of residual vapor and cooling water, reducing specific energy consumption by a third compared to current MED plants, and can produce up to 1,800 liters of desalinated water per person per day at low energy cost.
Implementation Method 1
enhance latent heat exchange
Implementation Method 2
evaporator-condenser effects
Implementation Method 3
thermal exchange through the walls of the tube or chamber
Implementation Method 4
flash evaporation-condensation phenomena in the flash boxes
Implementation Method 5
condensation of part of the vapor from each effect in the feed heaters
Implementation Method 6
condensation of the vapor evaporated in the last effect on condenser tubes through which cooling seawater circulates
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a multiple-effect multi-train desalination (MEMTD) device, based on phase change, which comprises at least two trains of n evaporator-condenser effects, wherein each train of effects comprises at least one latent-heat exchanger in each of the evaporator-condenser effects; at least one sensible-heat exchanger (6) between every two train effects, in which sensible heat is exchanged between the brine flow (18) released from the last evaporator-condenser effect of the previous train of effects and incoming water flow (20) provided as feed water (21) to the first evaporator-condenser effect of the following train; and a last condenser (7) that condenses, at least partly, evaporated vapor (22) from the last evaporator-condenser effect of the last train of evaporator-condenser effects.