Psychrometrics and Air Conditioning Processes - a PDH Online Course for Engineers, Architects and Surveyors

Psychrometrics and Air Conditioning Processes

Course Outline

Psychrometry is the study of moist air. It is significant in terms of thermal comfort and is a major consideration in design of air conditioning systems. Air conditioning engineers use the psychometric chart to predict changes in the environment when the amount of heat and/or water in the air changes.

This 5-hr course gives an overview of psychrometrics and suggests how a better understanding of psychrometrics will improve air conditioning design and selection of equipment.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the reader will:

Understand the basic terminology and definitions related to air properties;
Read psychrometric chart;
Describe relationship of 7 air properties: DBT, WBT, RH, dew point, absolute humidity, enthalpy and specific volume;
Apply the psychrometric charts on air-conditioning applications;
Understand how the various properties of air are measured;
Understand various psychrometric processes viz. sensible heating and cooling, cooling and dehumidification, evaporative cooling and heating and humidification;
Understand adiabatic process and governing mass balance / energy balance equations for air mixing;
Understand the air conditioning processes for 4 extreme climatic conditions viz. Miami, Phoenix, Minneapolis and Seattle;
Understand the difference between sensible heat and latent heat;
Understand the sensible heat ratio;
Understand the terms sensible heat factor, room sensible heat factor and grand sensible heat factor;
Understand psychrometric analysis for draw through and blow through air handling unit;
Understand how to calculate the required volume air flow rate;
Understand how to compute the cooling coil capacity with example; and
Understand standard equations used in air conditioning.

Intended Audience

This course is aimed at mechanical and HVAC engineers, facility managers, environmentalists, H &S professionals, O & M personal, safety engineers, industrial hygienists, and engineers responsible for the design, purchase or upkeep of heating, ventilation and air conditioning systems.

Benefit to Attendees

Attendees of this course will enhance their knowledge of psychrometrics, which they can use to analyze, design and operate air-conditioning systems, equipment and controls. A solid understanding of psychrometrics can prevent costly mistakes in the design and operation of commercial, residential, industrial cooling, dehumidification, drying and humidification systems.

Course Introduction

Air conditioner sizing is a very important aspect of maintaining a desirable environment in buildings. Get the sizing wrong, and you’ll be facing problems such as insufficient cooling, insufficient moisture removal, and unnecessarily high electricity bills.

Air conditioning engineers use the psychometric chart for visualizing moist-air relations, predict changes in the environment and design the spaces for thermal comfort. A psychrometric chart provides a convenient way to look at the air conditioning processes and it will answer why heated air can hold more moisture, and conversely, how allowing moist air to cool will result in condensation. Air conditioning engineers use the psychometric chart to predict changes in the environment when the amount of heat and/or water in the air changes.

This course will provide you a basic understanding of psychrometric and air conditioning processes.

Course Content

This course is in the following PDF document:

Psychrometrics and Air Conditioning Processes

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

The design of cooling and heating systems is based on the principles of psychrometrics. Psychrometric chart describes the relationship of seven air properties namely dry-bulb temperature, wet-bulb temperatures, relative humidity, humidity ratio, specific volume, dewpoint temperature, and enthalpy can be quickly characterized at varying conditions. The versatility of the psychrometric chart lies in the fact that by knowing just two properties of moist air, the other properties can be determined.
Good understanding of psychrometrics is essential because:

Psychrometric analysis can be used to predict changes in the environment when the amount of heat and/or water in the air changes.
Psychrometric analysis is crucial in accurately computing the volume flow rates of air through the air-conditioning ducts.
Psychrometric analysis enables the HVAC designer to compute the load imposed on the conditioning equipment (grand load) including outside air load.
Psychrometric analysis is inherently capable of distinguishing between the sensible and latent load quantities of outside and conditioned space (room) air, thus providing an insightful picture of how to handle the existing moisture.
Psychrometric chart is a useful tool for visualizing moist air relations for instance; it will answer why heated air can hold more moisture, and conversely, how allowing moist air to cool will result in condensation.
Psychrometric analysis help you can estimate energy flows; evaluate performance and plan energy conservation.

Today, software’s are available to do psychrometric analysis and while very few engineers will ever need to do complex psychrometric analysis by hand, author believes that the HVAC engineers understand psychrometrics well enough to verify computer program results and even predict which systems will perform better than others.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.