What is sorption hysteresis?
What is sorption hysteresis?
INTRODUCTION. The sorption hysteresis is a well known phenomenon for wood. Hysteresis means in this context that the equilibrium moisture content (EMC) is different in desorption and adsorption processes.
What is hysteresis in moisture absorption?
The amount of moisture adsorbed by the material is dependent on the relative humidity of air to which wood is exposed or to the availability of water. This phenomenon, called hysteresis between the adsorption and desorption curves, is rarely considered during modeling or experimental studies of the building envelope.
Why hysteresis occurs in sorption isotherm?
In the hygroscopic range, sorption hysteresis is related to internal changes in cell walls as the amount of liquid water in the void structure is minuscule.
How does hysteresis occur?
Hysteresis occurs whenever there is a state change (a “stateful” material) in a system, so that when the input cycles back to the starting point, the material and the output of the system transition through a different series of states. Magnetic materials and tunnel diodes, are good examples of the effect.
What is hysteresis in magnetism explain?
Magnetic hysteresis occurs when an external magnetic field is applied to a ferromagnet such as iron and the atomic dipoles align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become magnetized. Once magnetized, the magnet will stay magnetized indefinitely.
How do you test for hysteresis?
Hysteresis loops can be measured either in a maximum field of 1250 mT, using a vibrating sample magnetometer (VSM), or in a maximum field of 5 T, using a Quantum Design MPMS-2 magnetic-properties measurement system, equipped with a superconducting magnet. These high fields are necessary to fully saturate samples.
What is hysteresis in chemistry?
Hysteresis is the common property of ferromagnetic substances. Generally, when the magnetization of ferromagnetic materials lags behind the magnetic field this effect can be described as the hysteresis effect.
Does the desorption curve for an isotherm show hysteresis?
The desorption curve for this isotherm appears to show hysteresis, especially below a water activity of 0.60. However, an isotherm, run on a sample wetted to a maximum water activity below the phase change, exhibits very little hysteresis.
What is true hysteresis in a full boundary isotherm?
Differences between sorption curves in the subsequent isotherms represents true hysteresis. Working Isotherms Full boundary isotherms give information about the physical characteristics of a product, show hysteresis, and are important in establishing critical control points, but in many cases a working isotherm will prove very useful.
Is there a hysteresis model for water in the matrix?
Several plausible hysteresis models exist for samples wet enough for water to be held in the matrix by capillary forces. The “ink bottle” model pictures a pore with a narrow neck and a larger internal radius.
