Skip to main content

What is Dew point temperature and What is Dry bulb Temperature ?

 If a mixture of air and superheated water vapor is cooled at constant pressure, the partial pressure of each constituent remains constant until the water vapor reaches the saturated state. Further cooling causes condensation. The temperature at which water vapor starts condensing is called the dew point temperature tdp of the mixture. It is equal to the saturation temperature at the partial pressure pw, of the water vapor in the mixture. 


Dry bulb temperature (dbt) is the temperature recorded by a thermometer with a dry bulb. 

Wet bulb temperature (wbt) is the temperature recorded by a thermometer when the bulb is enveloped by the a cotton wick saturated with water. As the air stream flows past it , some water evaporates taking the latent heat from the water -soaked wick, thus decreasing its temperature. Energy is then transferred  to wick from the air. When equilibrium condition is reached , there is a balance between energy removed from the water film by evaporation and energy supplied to the wick by heat transfer, and the temperature recorded is the wet bulb temperature. 

A psychrometer is an instrument which measures both the dry bulb and the wet bulb temperature of air. A sling thermometer has mounted on a frame with a handle. The handle is rotated so that there is good air motion. The wet bulb temperature is the lowest temperature recorded by the moistened bulb. 



Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of  detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of  a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of  the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of  electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a  roll. The objec...
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more