2011) the mechanism of wood drying using an IR heat transfer method was studied The results indicated that the moisture transport mechanism could be considered as a semi-permeable membrane process with the moisture content as a dilute aqueous solution We proposed that the moisture movement in wood is governed by osmotic effects based on a Drying has a number of close synonyms Dehydration is the process of depriving a material of its water or the loss of water as a constituent The term is often used in food-drying operations to describe processes which strive to expel moisture but retain other volatile constituents in the original material and which are responsible for valuable aromatic and flavoring properties

Mechanism of moisture movement in the drying of organic

drying rate is dependent upon the nature of moisture movement from within the material to the surface Critical moisture content is defined as the concentration at v hich the transition from the constant rate to a falling rate period occurs Equilibrium moisture content is the lovrest moisture content

mechanism the concentration gradient is the driving force Water diffusion can be in the form of liquid or vapor In the case of liquid diffusion osmotic pressure could be the driving force for water movement In capillary mechanism the moisture moves due to surface tension and does not conform to

Drying mechanism In some products having a relatively high initial moisture content an initial linear reduction of the average product moisture content as a function of time may be observed for a limited time often known as a constant drying rate period Usually in this period it is surface moisture outside individual particles that is

This is a simple theory of moisture movement during drying Actually the drying is very complicated phenomenon Moisture in foods is subdivided in to ionic groups such as carboxyl and amino acids hydrogen groups such as hydroxyl and amides and unbound free moisture in interstitial pores and intercellular spaces (Figure 4)

For a hygroscopic material the dry zone is called the sorption zone due to the adsorptive nature of moisture retention In the dry zone the free water content is zero and the main mechanism of moisture transfer is vapor flow However in this region the movement of adsorbed water may also play an important role During drying the position

Heat and Mass Transfer in Convective Drying Processes

the mechanism of internal moisture movement Although it is now accepted that in most practical situations of air drying of foods the principal rate-determining step is internal mass transfer there is no agreement on the mechanism of internal moisture movement In the case of capillary-porous materials such as fruits and

Dec 12 2014Linear concave or convex drying-rate plots possible depending on the nature of solids and mechanism of internal moisture flow Graph B: Drying rate which is the derivative of curve A The rate is constant or decreasing slightly for a considerable period Typical plots of total moisture content and drying rate 28

The drying characteristics of dense samples were not affected by total pressure suggesting that the mechanism of internal moisture movement is best considered a liquid or adsorbed phase diffusion phenomenon Effective moisture diffusivities of dense pasta increased as temperature and moisture content increased

Dec 12 2014Linear concave or convex drying-rate plots possible depending on the nature of solids and mechanism of internal moisture flow Graph B: Drying rate which is the derivative of curve A The rate is constant or decreasing slightly for a considerable period Typical plots of total moisture content and drying rate 28

Moisture content of the grain after passing the dryer may be reduced 2 to 4% depending on the grain moisture content at intake drying air temperature and the air flow rate The grain is held in the buffer bins 6 hours or more allowing for the equalisation of moisture within the kernel

sistant to moisture flow (less permeable) than sapwood and thus heartwood usually requires longer drying time The lower permeability of heartwood also makes it more susceptible to certain drying defects (ch 8) and so it requires milder drying conditions Heartwood is usually darker than sapwood However because the

Drying rate decreases because of the decrease in wet surface area Fraction of wet surface decreases to zero where first falling rate ends Second falling rate Sub surface evaporation takes place it continues until the equilibrium moisture content is reached Mechanism of drying process Movement of moisture takes place due to

Since drying involves extracting the moisture from the food items and expelling it into the surrounding air low humidity will help with the drying process If the humidity is high drying will be slower simply because the surrounding air would also be laden with moisture By increasing the currents or flow of air one can speed up the drying

Moisture Management

Moisture management fabric is widely applied in sport clothing high value casual wear and uniforms The concept of this technology is to have a quicker drying rate and provision of efficient movement of moisture away from the skin The mechanism of moisture management fabric

The major wetting and drying processes and the moisture transport mechanisms involved in the movement of moisture into and out of the enclosure are summarized in Figure 2 Moisture Sources There are four primary sources of moisture in buildings It is useful to categorize them as: 1

Moisture is a word used commonly to describe any volatile liquid or vapor involved in drying ie it is not used selectively to mean only water Moisture gradient is the moisture profile in a material at a specific moment during drying which usually reveals the mechanisms of moisture movement in the material up to the moment of measurement

A Comparison: Dehumidification Versus Heat in Construction Drying Applications Garrett Freeman September 2009 The effects of moisture inside a building under construction can become a serious problem for contractors as well as a danger to future occupants Many of the materials used today to construct buildings absorb moisture

Soil is a mixture of organic matter minerals gases liquids and organisms that together support life Earth's body of soil called the pedosphere has four important functions: as a medium for plant growth as a means of water storage supply and purification as a modifier of Earth's atmosphere as a habitat for organisms All of these functions in their turn modify the soil and its

Moisture management fabric is widely applied in sport clothing high value casual wear and uniforms The concept of this technology is to have a quicker drying rate and provision of efficient movement of moisture away from the skin The mechanism of moisture management fabric

For a hygroscopic material the dry zone is called the sorption zone due to the adsorptive nature of moisture retention In the dry zone the free water content is zero and the main mechanism of moisture transfer is vapor flow However in this region the movement of adsorbed water may also play an important role During drying the position

Jun 01 2010The effect of process variables on average effective moisture diffusivities were illustrated in Table 1 Increasing the drying air temperature and air velocity increase the D eff values When absolute humidity of air increases average D eff values decrease Low air absolute humidity is of the air is driving force to moisture movement from the surface to the air

Drying mechanism In some products having a relatively high initial moisture content an initial linear reduction of the average product moisture content as a function of time may be observed for a limited time often known as a constant drying rate period Usually in this period it is surface moisture outside individual particles that is