## Air change

The quantity of infiltration of ventilation air in cubic meters per second divided by the volume of the room gives the number of so-called air changes during a given interval of time. Tables of the recommended number of such air changes for various rooms are used for estimating purposes.

Air changes per hour, abbreviated ACPH or ACH, or air change rate is a measure of the air volume added to or removed from a space (normally a room or house) divided by the volume of the space.[1] If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced.

In many air distribution arrangements, air is neither uniform nor perfectly mixed. The actual percentage of an enclosure's air which is exchanged in a period depends on the airflow efficiency of the enclosure and the methods used to ventilate it. The actual amount of air changed in a well mixed ventilation scenario will be 63.2% after 1 hour and 1 ACH.[2] In order to achieve equilibrium pressure, the amount of air leaving the space and entering the space must be the same.

{displaystyle quad ACPH={frac {60Q}{Vol}}}

Where:

• ACPH = number of air changes per hour; higher values correspond to better ventilation
• Q = Volumetric flow rate of air in cubic feet per minute (cfm), if using Imperial units, or cubic meters per minute if using SI
• Vol = Space volume L × W × H, in cubic feet if using Imperial units, or cubic meters if using SI

Ventilation rates are often expressed as a volume rate per person (CFM per person, L/s per person). The conversion between air changes per hour and ventilation rate per person is as follows:

{displaystyle quad Rp={frac {ACPH*D*h}{60}}}

Where:

• Rp = ventilation rate per person (CFM per person, L/s per person)
• ACPH = Air changes per hour
• D = Occupant density (square feet per occupant, square meters per occupant)
• h = Ceiling height (ft, meters)

### Office hours

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### Civil Eng. Students

DON'T miss!

As we approaching the second midterm exams..  Get ready and remember our offices are open to answer you . do not hesitate to .contact me if you have difficulties

For CE 370 students : Your second midterm exam will be on Wednesday 27 March 2019. In the surveying lab

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### Announcements

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There will be an orientation session in the midell of this term to help you select your track in Civil and Environmental Engineering

### Special Event

#### Special Issue

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### Mining Engineering

Mining engineering is an engineering discipline that involves practice, theory, science, technology, and the application of extracting and processing minerals from a naturally occurring environment. Mining engineering also includes processing minerals for additional value.

### Environmental Engineering

Environmental engineers are the technical professionals who identify and design solutions for    environmental problems. Environmental engineers provide safe drinking water, treat and properly dispose of wastes, maintain air quality, control water pollution, and remediate sites contaminated due to spills or improper disposal of hazardous substances. They monitor the quality of the air, water, and land. And, they develop new and improved means to protect the environment.

### Proverb

Actions speak louder than words

### Univeristies

Universities I've worked in

Assuit University (Home University), Egypt

Imperial College, London, UK

King Saud University, KSA

,Majmaah University

### Also visit

https://www.researchgate.net/profile/Sameh_Ahemd

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### Course 2018/19-2

1. Surveying 1 CE 370
2. Surveying II  CE 371
3. Senior Design II  (round 6) CE 499

### Latest

Member of the Editorial Board: " Journal of Water Resources and Ocean Sciences"  2013 till now

Participating in The Third International Conference on Water, Energy and Environment,(ICWEE) 2019 - American University of Sharjah, UAE 26-28 March 2019 with a Paper and Poster

New article

### Coming soon

2nd Midterm Exams on 3/4/2019

### Student Conference

Participation  in the 6Th Student Conference

With a paper and oral presentation

From the Senior Design Project CE499 -35

See inside, the paper, and presentation

## 2018-2019S

 Power point Sheets Lecture notes 15 3-4-2019 :Second Midterm Exam Results Model Answer

Working  marks is available -Click on Surveying I

## 2018-2019-2

 Lectures First midterm exam Lab Results

See Inside

Working marks out of 60 is  available- Click on Surveying 2

## Photogrammetry

### 2018-2019-1

 Available 0-1-2-3-4 Power point Available Quizzes 2 and 3 with model Answer Quizzes Available Chapter 1,2,3,4,5 Lecture notes Report 1  Cameras Report Y 60 marks Exams

See Inside

Student Performance Records

### CE 499 Course

Second Best paper from Senior Design Projects in 2015

Paper title:

### Evaluation of Groundwater Quality Parameters using Multivariate Statistics- a case Study of Majmaah, KSA

Students:

Abdullah A. Alzeer

Husam K. Almubark

Maijd M. Almotairi

### الهيئة الوطنية للاعتماد والتقويم الاكاديمي

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## الهيئة السعودية للمهندسين

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