THE NATURE OF WATER VAPOR

Consider two closed rooms adjacent to one another. If the partial pressure of the water vapor in room #1 is greater than the partial pressure of the water vapor in room #2, then the water vapor will travel through the wall into room #2 regardless of the composition of the wall.
Let's take this hypothetical example a step further. If the absolute humidity of the air in room #1 is greater than that of the air in room #2, then the water vapor pressure will be higher in room #1. Therefore, when drying room #2, the problem of water vapor coming through the wall from room #1 must be considered.
A vapor barrier can slow down the passage of vapor from wet to drier areas, but it cannot keep water vapor out; it can only slow the rate of penetration.
The choice of a vapor barrier is based on the degree of dryness required in the controlled space; the efficiency of the equipment being used for drying; and the cost of construction.
Commercial vapor barriers, moisture resistant construction material,p paints an other coatings, offer a variety of design alternatives. Manufacturers of vapor barrier materials can supply specific information on their products.

USING DESICCANTS TO DRY AIR

A simple straight forward way to obtain dry is to use desiccants - that is, adsorbents or materials that have a natural affinity for water. A desiccant is able to take up the additional moisture given up by the air without changing its size or shape. So an air stream can pass through a desiccant and become significantly drier without elaborate cooling, compression, or other complex systems or controls. After the drying task is complete, the desiccant is regenerated, and is ready to dry more air.
A desiccant dehumidifier utilizes only a small amount of desiccant at any one time and constantly regenerates a s part of a continuous cycle. This simple equipment is manufactured in many sizes, from very Small to very large to meet various dry air requirements.
An added feature of the dehumidifier is its ability to function equally well at extremely low to very high levels of humidity with no regeneration problems and no changes in cycle control. Its versatility in performing in any type of application is unique among most methods of drying air.

relationship

This afternoon while setting up the LCD projector and my laptop for the student's presentation, suddenly a student asked me,"Sir tahu buat pizza?" I really got shock on how can he know that? I was silence for a few seconds, coz I was just 'digesting' his question. Then only I realized that I did write this in my blogger. Meaning that he really read my blogger and not only looking for his assignment only. Feel glad coz my blogger has become a platform or medium for us to know each other. Or let them know me better. Hopefully it will create a closer relationship between me and the students.

ACR 3933 2ND ASSIGNMENT - PSYCHROMETRICS

Question 1:
Air at 95 DB and 104 grains of moisture enters a saturator in the building the Psychometric Chart Section. At what temperature will the air leave the saturator? What will be its relative humidity?

Question 2:
Air at 80 DB and 50% RH is cooled and dehumidified to 50 deg F and 100% RH. How much sensible heat and latent heat is removed from 1 000 cfm of this air?

Question 3:
If 500 cfm of outside a ir at 96 DB and 76 WB is mixed with 1 500 cfm of return air at 80 DB and 50% RH, find the following properties of the mixture:
a. Dry bulb
b. Wet bulb
c. Dew point
d. Specific humidity


Deadline for submission: 15/8/07, 10.00a.m