Journal of Indoor Environmental Quality

A study in warmth and air velocity and their role on the perception of air freshness.

excerpt: “Three methods were used to evoke a sensation of warmth at the threshold level: (1) by increasing the intensity of the radiant heat falling on the skin over that from the solid surroundings of the cubicle by an amount which was just sufficient to evoke a sensation of warmth, and obtaining values of such threshold intensities for various areas of skin; (2) by exposing the skin to a stream of air moving at one of several velocities and determining the increase in air temperature above that in the cubicle required to evoke a sensation of warmth; and (3) by increasing the intensity of the radiation falling on the skin, and simultaneously exposing the skin to a stream of moving air.”

Source: Turner, D., Radiative and convective stimuli of threshold intensity, Environmental Hygiene Research Unit, M.R.C. Laboratories, Hampstead, London, N.W 3, J Hyg (Lond),1955 March; 53(1): 32–49. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2217808/>

RBc:  I love these old studies because much of what we know today in the world of architecture which relates to occupant comfort, comes from this type of research work. A few statements that are of interest from this paper include:

1. "On the whole, a change of 1 C. in air temperature is equivalent to 1.40 C. change in mean radiant temperature in its effect upon thermal sensations."
2. "Bedford & Warner (1939) found that changes in both the average value and the variability of the air speed and in the temperature had a marked effect upon impressions of freshness."

Additional reading:

1. http://www.healthyheating.com/Definitions/facts_about_skin.htm

Energy and Mass Flow - Seeing that which was once invisible to the naked eye.

We’re big fans of Professor Gary S. Settles and his colleagues with their very cool schlieren camera work at Pennsylvania State University. We feature a number of their images and videos in our IEQ education programs – you can see them over at the http://www.healthyheating.com/ site.

Well today we got a heads up from Dr. Stefano Schiavon from the Center for the Built Environment, University of California, Berkeley that Dr. Settles with his colleague Dr. Michael J. Hargather have a paper published in the October issue of ASHRAE’s HVAC&R Research titled, “Background-oriented schlieren visualization of heating and ventilation flows: HVAC-BOS”

You’ll want to obtain this document if you have an interest in the field.

Abstract: There is an important need for simple methods to visualize and measure whole-field airflow patterns in the HVAC field. The background-oriented schlieren (BOS) method is presented here as an answer to this need—a simple and effective method for visualizing refractive HVAC flow fields in situ. The equipment required is simple, portable, inexpensive, and readily available, thus superseding some previous approaches, including lens-and-grid schlieren techniques that require large fixed installations. For BOS a custom random-dot background pattern is used, and imaging is done by a consumer-grade digital single-lens-reflex (SLR) camera. After covering the principles of BOS, examples are shown of visualized airjets and plumes from heating vents and registers, a space-heater, a tea kettle, and a human thermal plume and cough. BOS images of candle plumes are also used to explore several different visualization approaches, equipment arrangements, and image color scales. While current results are purely-qualitative visualizations, quantitative temperature measurements can also be made in certain cases where the flow is approximately two dimensional. Finally, BOS lends itself well to certain HVAC chores, such as the diagnosis of commercial kitchen ventilation airflows.

Citation: Michael J. Hargather & Gary S. Settles (2011): Background-oriented schlieren visualization of heating and ventilation flows: HVAC-BOS, HVAC&R Research, 17:5, 771-780

Article link: <http://www.tandfonline.com/doi/abs/10.1080/10789669.2011.588985>
___

Have a look at some of the images from the PSU website and imagine being able to obtain these wonderfully useful photographs -  to see that which was once invisible to the naked eye. Be sure to also check out the video we have featured at the website from our friends at Science Photo Library courtesy of donations from site visitors. A heads up it’s a large file - allow at least 120 seconds to load…best to grab a cup of coffee and come back in a few minutes - it’s well worth the wait.

For those of us who study indoor environmental quality this tool is like adding a third or fourth dimension to our understanding of fluid flow and its influence on occupant comfort.

A big thanks to Dr. Schiavon for bringing this to our attention.

Links of interest:

Dr. Gary Settles
Gas Dynamics Laboratory
Penn State University
http://www.mne.psu.edu/Directories/Faculty/Settles-G.html

Dr. Michael J. Hargather
Gas Dynamics Laboratory, Department of Mechanical and Nuclear Engineering
Penn State University
http://www.mne.psu.edu/psgdl/Staff.html

Dr. Stefano Schiavon
Center for the Built Environment
University of California, Berkeley
http://www.cbe.berkeley.edu/aboutus/staff-stefano.htm
www.cbe.berkeley.edu

Old and rare books related to IEQ and Human Factor Design

Old and rare books related to IEQ from Laurens (The Physiological Effects of Radiant Energy, 1933), Vernon (The Principles of Heating and Ventilation, 1934) and Bedford (Modern Principles of Ventilation and Heating, 1937)

Our three latest additions to our library have arrived! I’ve been harvesting a bumper crop of information from these treasures whose information is just as valid today as it was when they were written.I love this old stuff because it established the “why” and it stands the test of time.

Every day I come across someone who is ambivalent or ignorant to the importance of “human factor design” with most focusing on the “mechanics of doing” rather than the science of “understanding why”…it an unfortunate byproduct of our system which is based on judging the construction industry by “how” it put things together to meet the minimum requirements of the building code.

As I have said before, the contractors are the first and last people to touch the project…it behooves us to teach them the “why” before we teach them the “how”.

Educational Video's on IEQ and Energy

 
With the help from our UK friends at Science Photo Library we make available for web viewing several new videos illustrating concepts of heat transfer, energy and indoor environmental quality.

For the young grade school student working on a class project or clients of the seasoned veteran looking to educate themselves these high quality animations help explain concepts to the non-technical person.

The Schlieren video in particular emphasizes once again we’re not in the business of conditioning buildings but in conditioning people.

When accessing each of the pages for the first time, allow 60 to 120 seconds to load. We hope you enjoy the new content courtesy of our site supporters.

Best regards,

Robert Bean

New educational video’s:

• Human body - Thermal Plume 
• Heat transfer by conduction
• Heat transfer by infrared radiant
• Heat transfer by convection