Category Archives: Psychrometrics

Psychrometics is the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. These posts will deal with the field of psychrometrics and the psychrometric chart.

Exploring Evaporative Cooling–Part 1

If you look at a psych chart closely, you will notice that the constant wet bulb lines are not exactly parallel to the constant enthalpy lines. Note that to make things more visually apparent in this blog post, for most … Continue reading

Posted in Air Handling Systems, HVAC Calculations, HVAC Fundamentals, Psychrometrics | Leave a comment

Build Your Own Psych Chart – Creating the Data for the Saturation Curve and a Bit About VLOOKUP

So here I am, over a year later after starting this string, getting back to it.  All I can say is life happens and sometimes, because of that, you find that what you set out to do takes a bit … Continue reading

Posted in Excel Techniques, HVAC Calculations, HVAC Fundamentals, Psychrometrics | Leave a comment

A Free Electronic Psych Chart and How to Use It to Plot Basic HVAC Processes

Ryan Stroupe of the Pacific Energy Center recently worked out a deal that allows him to provide a free limited capability version of Hands Down Software’s electronic psych chart.  You can get a copy at this link and a overview … Continue reading

Posted in Air Handling Systems, Economizers, Excel Techniques, HVAC Calculations, HVAC Fundamentals, Psychrometrics, Resource List and other Resources, Weather and Climate Interactions with Buildings and Systems | 1 Comment

Economizers–The Physics of a Mixed Air Plenum

I’ve been working on a post that shows how a scatter plot technique can be used to assess the performance of an HVAC airside economizer.  It’s based on comparing a plot of outdoor air temperature vs. mixed air temperature for … Continue reading

Posted in Air Handling Systems, Controls, Economizers, HVAC Calculations, HVAC Fundamentals, Psychrometrics | Leave a comment

Build Your Own Psych Chart – A Few Fundamental Principles

To get you started on the process of building your own psych chart, I need to make sure we are all on the same page about a few basic principles.  So that discussion will be the focus of this post. … Continue reading

Posted in Psychrometrics | 2 Comments

Build Your Own Psych Chart – In Memory of Bill Coad

I can’t really remember which of my HVAC mentors was the first to introduce me to psychrometrics and the psychrometric chart.  They all generously shared their knowledge and time with me as I tried to take the engineering basics I … Continue reading

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Applied Psychrometrics – the Psych Chart Dry Bulb Temperature Axis (Plus a Bit about Dry Bulb Thermometers)

This post looks at dry-bulb temperature and how it is measured.  Then, it looks at how you plot a dry-bulb temperature on a psych chart.  The links below will jump you to the various topics in the post. What Is … Continue reading

Posted in Controls, Psychrometrics | Leave a comment