Department of NFE
Daffodil International University
Md Sohel Rana
ID No- 163-34-562
Department of NFE (Evening)
Submitted Date .0.2018
Properties of Dry Air: Is the specific heat, ratio of specific heats, dynamic viscosity, thermal conductivity, density and kinematic viscosity is the dry air properties, dry air properties temperatures at ranging 175 – 1900 K.
Air is a mixture of several constituent gases. The composition of air varies slightly, depending on the geographical location and altitude.
The apparent molecular weight of standard dry air is 28.9645. The gas constant for dry air, Ra, is computed as 8314.41/28.9645 = 287.055(m3Pa/kgk).
Specific Volume of Dry Air is the ideal gas laws can be used to determine the speci?c volume of dry air. Therefore, V’a =RaTa/pa.
Specific Heat of Dry Air is the 1 atm (101.325 kPa), the speci?c heat of dry air Cpa in a temperature range of -40 to 60 degree C varying from 0.997 to 1.022 kJ/(kg K) can be used.
Enthalpy is the heat content of dry air, is a relative term and requires selection of a reference point. Ha = 1.005(Ta-To)
Dry bulb temperature is the properties of dry air it measured by a thermometer.
Properties of Moist Air: Is the dry bulb temperature, dew point temperature, wet bulb temperature, relative humidity, absolute temperature, vapor pressure, heat content, specific volume ; density.
Important of Moist Air:
The useful life of moisture in inappropriate quantities and moisture is very harmful. Because of this, many attempts are made to reduce the content of dry food water to prolong their shelf life. Once it is reduced to the desired level then the product can be packaged for storage. Unfortunately, reducing humidity content is not always enough. Environmental conditions can play a role as well.
There are four mechanisms by which environmental conditions may cause a moisture problem in your food storage:
1.- The air holding the container with the food keeps enough moisture to increase the humidity of the food at an undisclosed level.
2. If water vapor is not too high, then a rotary temperature level can reach the dew point of the hollow moisture, due to which your diet can be concentrated from the water and on a hot, humid night after a hot, wet night on your lawn.
3. – The seal from the sand to the sand to prevent the wind stopped moisture may not be sufficient enough.
4. Packaging material itself can be porous to water vapor to one or another degree. All paper, wood and cardboard have this fault. Depending on their specific physical characteristics, some plastic as well. Metal and glass containers have excellent barrier features although they may not be sealed.