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| Humidification |
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| Atmospheric Air |
- Humidity is the amount of moisture content present in the atmospheric air.
- Absolute humidity of the atmosphere is the mass of the water vapour present per unit volume (eg. 10 g/ m 3).
- Relative Humidity is the amount of moisture contained in the air at any given temperature as compared to the maximum amount of moisture the air can hold at that temperature when saturated.
- Dew point is the temperature of air at which moisture starts condensing when air is cooled.
Fundamentals of Humidification
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| Sensible & latent heat |
Sensible Heat
- It is the heat that Raises the Temperature of the water without any change of phase (from liquid to vapour).
Latent Heat
- It is the heat which changes the phase of the water from liquid phase to vapour phase with reference to the air, it is the heat of evaporation of the contained water vapour.
Enthalpy or Total heat
- Enthalpy is the total heat contained in unit weight of air (in Kcal/kg of air) is the sum of sensible heat content and the latent heat of water vapour contained in it.
Formula to calculate Relative Humidity of a Department
Psychrometric Chart
A Graphical representation of the relationship between various properties of air.
(Dry bulb temperature , Wet bulb temperature , Humidity ratio , Enthalpy , Relative humidity ).
Relative Humidity (RH%)
98 - (Dry bulb temperature F - Wet bulb temperature F) x 300 / Dry bulb Temperature F
C = (F - 32 ) x 5/9
F = (C x 9/5 ) + 32
- Difference between Humidification and Air Conditioning in humidification, the department relative humidity is controlled.
- in air conditioning the department temperature,humidity,cleanliness (dust / fly Liberation ) and distribution of the air to meet the requirement of conditioned space.
- An air conditioning system may use heating , cooling , humidifying , dehumidifying and filtering units of combination of these depending upon the outside weather.
IMPORTANCE OF HUMIDITY CONTROL IN TEXTILES
- Proper control of Environmental conditions is essential for efficient performance of Man and Machine.
- In the Textiles Industry Appropriate environmental condition are achieved by control of Relative Humidity,Air Clean-liness, Air changes and Temperature.
- Air changes and Temperature are crucial for ensuring the quality of the final product, efficient operation of machinery and comfort of Operating Personnel.
- Higher Humidity Level may lead to Difficulties in opening and cause roller laps on machines.
- Due to high Humidity, apart form the dust levels, if stickiness is present in the cotton may cause sticking of fibres on rollers.
- Lower humidity level may lead to fibre fly in to the department.
- The number of air changes is an important factor to ensure that air is clean and safe.
- Air changes per hour affects the productivity, product quality and health of the personnel.
STATIC GENERATION ON TEXTILES FIBRES
Static Electricity
- An imbalance in the distribution of electrons which is an accumulation of a Time-In variant charge of positive and or negative sign on the material.
- Cotton fibres, particularly between the carding and Roving stages where they are loosely bound, are especially vulnerable to static electricity.
- Static electricity can cause roller licking increases fire hazards in the department.
- The higher the speeds, the more the likelihood of the above problems occurring.
- Higher machine speeds put a heavy mechanical stress on the fibre thus lead to end breakages during spinning and adversely affect productivity.
- Harsh treatment of fibre and yarn causes the liberation of fluff and dust which affects the working environment.
- Unlike cotton fibre, synthetic fibre does not absorb moisture , but tends to e sticky at higher temperatures.
EFFECT OF HUMIDIFICATION ON TEXTILES FIBRES
In synthetic fibre processing, the humidification plant cannot control the temperature due to the fluctuation in dry bulb temperature along with wet bulb temperature.
Air Conditioning is required to control both RH% and Temperature.
The condition of Temperature and RH for cotton and synthetic fibre vary according to the quality and blending of the fibres used, the speed of the processing machines etc..
IMPORTANCE OF CONTROLLED RELATIVE HUMIDITY AND TEMPERATURE
Reduction in static electricity there by removing possibilities of fire hazard and roller licking and consequently increasing productivity.
Increasing strength and abrasion resistance of cotton fibers.
A cleaner environment, as generation of fluff is reduced and fluff tends to settle down thus increase worker efficiency.
AIR CONDITIONING & REFRIGERATION
MINI HUMIDIFIERS
- Compact and Independent unit economical and used when spot humidification is desired.
- A mini humidifier provides continuous humidification of air.
- The unit comprises of a twin shaft driving an air circulating fab and atomizing disc.
- Water is atomised into a fine mist and the air flow is guided through the mist for humidification and proper distribution.
- Surplus unatomised water is drained and re-circulated form the tank externally located.
- By means of cooling coils placed within the air flow to be cooled.
- Cooling coils could be of direct expansion where refrigerant is circulated or chilled water type where chilled water is circulated.
- By direct mixing of chilled water with re circulation water and sprayed on the air washer.
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