Flexible Inlet Stratification Pipe for Thermal Storage
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Solution Overview
Problem
Existing thermal energy storage systems face challenges in maintaining stratification due to mixing caused by buoyancy, jet mixing, and thermal conduction, leading to reduced thermal performance, and current stratification devices like rigid and fabric inlet pipes either mix fluids or become clogged, reducing efficiency.
Innovation Solution
A flexible, non-porous inlet stratification pipe made from materials like ETFE or PVDF, arranged vertically in the tank, which expands and collapses to equalize pressure, ensuring fluid enters at the correct temperature layer without turbulence, using holes that open and close based on temperature differences to prevent mixing and clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rigid inlet stratifiers with openings are used, then fluid can be delivered to thermal layers, but cold water gets sucked into the stratifier through lowest openings causing mixing and reducing thermal performance
Solution Approach 1:
The inlet stratifier transitions from a rigid structure to a flexible hose that can dynamically change its configuration. The flexible hose sags under its own weight to form a catenary curve, creating a self-adjusting structure that adapts to pressure changes and prevents cold water suction while maintaining fluid delivery capability
Solution Approach 2:
The invention changes the physical state of the stratifier from rigid to flexible, allowing it to deform and sag under gravity. This parameter change in flexibility enables the hose to form a catenary curve that naturally prevents cold water from being drawn up through the lowest openings while still allowing hot water to be delivered to the thermal layer
2Ease of operation
If fabric stratification inlet pipes are used, then stratification is enabled, but particles and calcium carbonate sediments block the pores reducing efficiency
Solution Approach 1:
The invention replaces porous fabric material with a flexible hose made of non-porous material. The flexible hose maintains the ability to sag and form a catenary curve for stratification while eliminating the pore-clogging problem entirely, as the smooth non-porous interior surface prevents particle and sediment accumulation
Solution Approach 2:
The flexible hose stratifier provides a durable, maintenance-free alternative to fabric pipes that require replacement due to clogging. By using a non-porous flexible material, the system eliminates the need for periodic maintenance or replacement, improving long-term reliability
3Loss of energy
If fabric pipes with multiple layers are used, then horizontal heat transfer is reduced, but the fabrics still function as filters reducing stratification efficiency
Solution Approach 1:
The invention replaces multi-layer fabric construction with a single-layer flexible hose made of thermally insulating non-porous material. This eliminates the need for multiple layers while achieving both thermal insulation and prevention of particle clogging, as the smooth interior surface prevents filtration of particles and sediments
4Adaptability or versatility
If vertically installed tubes with free openings are used, then inflow at variable heights is enabled, but jet mixing caused by kinetic energy of entering water destroys stratification
Solution Approach 1:
The flexible hose adapts its shape dynamically based on water pressure and flow rate. At lower pressures, the hose sags more, delivering water at lower heights, while at higher pressures it straightens to deliver water at higher heights, enabling variable inflow without jet mixing that would disrupt stratification
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 solution effectively maintains thermal stratification, enhancing the thermal performance of storage tanks by ensuring fluid delivery to the correct layer without turbulence or heat exchange, and preventing clogging, thus improving the overall efficiency of thermal energy storage systems.
Implementation Method 1
The flexible inlet pipe is made of a non-porous flexible material and comprises an inlet opening and a number of holes arranged in a single row in the longitudinal direction of the pipe. The flexible inlet pipe is arranged for circulating a fluid having a vertical temperature gradient through the storage tank, wherein the liquid in the pipe will not enter the storage tank until it reaches the layer when the temperature of the fluid in the pipe equals the temperature of the liquid in the storage tank leading to a slightly higher pressure in the pipe than in the storage tank or through the top opening of the pipe
Implementation Method 2
Stratification in thermal energy storage is a natural phenomenon encountered in liquid storage systems such as water tanks above a temperature of 4°C. Due to buoyancy forces, hot water tends to accumulate at the top of a thermal energy storage, whereas colder water will always be forced to move downwards
Implementation Method 3
Different factors tend to destroy the stratification. One example is mixing of water due to natural convection caused by buoyancy of hotter fluid that is surrounded by colder fluid, e.g. if the fluid inlet is hotter than the temperature at the position of the inlet or if a thermal energy storage is charged with an immersed heat exchanger. A different problem is by jet mixing (or plume entrainment) caused by the kinetic energy of the water entering the thermal energy storage or with thermal conduction and diffusion within the fluid itself
Data Source
Figure 1a
Figure 1b
Figure 2~4
AI summary
An inlet stratification device serves for providing and maintaining stratification of a fluid in a tank. The stratification device comprises a pipe (2) of a flexible non-porous material, having a number of holes (8), said pipe being configured to contract and expand such that exchange of fluid through the holes (8) of the pipe is substantially prevented in regions of the pipe, where the temperature of the fluid inside the pipe is higher than the temperature of the fluid outside of the pipe.