HVAC's Unseen Protectors

As the world deals with the Novel Coronavirus I was reminded of research that I was involved in some 35 years ago.  At that time I was directly engaged in modeling airflow and temperature profiles using Computational Fluid Dynamic (CFD) software for a major air distribution products company.

While we used CFD modeling for a wide variety of complex air distribution problems the case that came to my mind this week was modeling an infectious disease isolation room for the CDC.  The challenge was to design a negative pressure isolation room that also minimized exposure of a health care worker positioned directly adjacent to the patient bed. 

The specific type of infection to be studied at that time was tuberculosis (TB).  Much like the current coronavirus, TB is often spread by droplets when a patient coughs.  A healthcare worker standing next to the patient bed was almost certain to risk exposure if the room used conventional air distribution layouts and patterns.  The correlation with today's problem is obvious.

My current company, Mestex, has been using CFD analysis for 20 years.  Although our modeling efforts have not included the case mentioned above we can apply the same techniques to create accurate temperature and airflow models of data centers, pharmaceutical storage warehouses, chocolate or wine warehouses, eCommerce fulfillment centers, or virtually any temperature sensitive application.  Much like the goal of the CDC study of 35 years ago our objective is to use modeling to optimize our product applications without the expense of full scale mockups or, worse yet, finding out about a problem after the building is complete.

The HVAC industry is continuing to refine the modeling techniques that I used those many years ago in order to create even better solutions to healthcare worker protection.  In general, when we do our jobs correctly, the end user is not aware of what is involved.  After all, you cannot "see" temperature or air so our work is "invisible".  However, the HVAC industry has a vital role in helping protect people and critical products from many types of threats.

Hot Air Balloons and eCommerce

I live in an area that is almost ideal for hot air ballooning.  On almost any morning it is not uncommon to see at least 6 hot air balloons dotting the horizon.  Watching some the other day as they prepared for launch and then ascended it struck me that there is a basic lesson in the process that is useful to remember when designing HVAC solutions for eCommerce buildings and warehouses in general.

The obvious lesson is that hot air is buoyant and the hotter it is the more buoyant it becomes.  When prepping for launch the crews use their direct fired burners to blast hot air into the balloon causing it to fill and lift.  Once the balloon is vertical the crew fires the burners at full heat to get the balloon off the ground and on its way upward.  While in the air you can hear the burners firing whenever the balloon starts to drop below the altitude the pilot is looking for.  Short blasts produce little heat and balloon either stays stable or starts to slowly descend.  Long blasts produce more heat and the balloon rises.

So...what does this have to do with eCommerce and warehouses?  While the HVAC equipment cannot produce air that is hot enough to lift the building off the ground it can produce air that is hot enough to rise rapidly and stay near the top of the space. In an eCommerce fulfillment building with dozens of humans occupying the bottom 6 feet of the building that hot air can be a problem.

There are some HVAC companies that propose using very high temperature air to heat the entire space.  This becomes a real challenge as the hotter the air the more it wants to stay up near the ceiling.  There are a couple of ways to deal with this but both ways impact electrical operating costs.

One method is to install several large fans that are intended to pull air from the ceiling space and force it down to the floor level.  In addition to the electric power required to spin the fans this solution can also make it difficult to achieve the rack heights that are desired in the building.  There may also be structural cost implications depending upon the weight of the fan/motor assemblies.

The other method is to use the HVAC equipment fans themselves to force the hot air to the floor area.  This also requires electrical energy to overcome the buoyancy of the air. A secondary characteristic of this method is that the velocity of the air from the HVAC unit must be pretty high in order to force the air downward.  The result is a column of air moving at pretty high speed that reaches the floor in a relatively small area that can cause worker discomfort or stir up paperwork or products that are in the airstream.

Mestex has been producing a product concept for decades that overcomes these problems.  The concept is called "air turnover" and many companies have since copied the idea under different names.  The idea is simple....push warm (not hot) air into the space just above the worker level and pull it back across the floor where the workers benefit from the relatively slow moving warm air flow.  Not only does this method produce even temperatures where it is needed it also avoids wasting heat energy that collects near the ceiling with the hot air methods.

Deciding how to design an air turnover system can be challenging since the system sends air into the occupied space that also includes equipment, bottoms of racks, conveyor systems and such.  Another Mestex first is the use of Computational Fluid Dynamic ("CFD") modeling of the space to refine and optimize these designs.  CFD modeling originated in the defense industry to model aircraft performance and later was adopted by the process industry to evaluate things such as the impact of ocean currents on offshore oil rigs.  Since air is a fluid Mestex started using CFD modeling 20 years ago to assure owners that temperature critical products would be kept at the proper condition.  Mestex' use of CFD has expanded over the years to optimizing more mundane warehouse applications as well as more sophisticated applications such as data centers.  This expertise is available exclusively for Mestex customers.

So the next time you see a hot air balloon rising into the air you can appreciate the challenges of heating a warehouse or eCommerce building.

The Amazon Effect

I recently attended an interesting conference on the impact of E-commerce on the world of logistics and warehousing.  Of course, virtually everyone knows about Amazon and their E-commerce model.  "The Amazon Effect" is used to describe E-commerce in general and the economic impact on communities of having an Amazon facility in their area.

But I think that the part of the story that is not discussed enough is the changing nature of the facilities and the people in the facilities. 

Years ago a warehouse was a warehouse.  These big, uninsulated, boxes were filled with metal racks stretching to the ceiling and covering the floor from wall to wall.  Those racks were at least partially filled with finished goods that would eventually be located manually and pulled from the racks with a human-driven forklift.  From there the finished product would be taken to a truck at the loading dock and sent on its way.  I actually spent a summer during my school years, eons ago, locating products and driving the forklift to the truck.  I had a clipboard (that was like a tablet computer but held actual paper and used something called a "pen" to mark things off on the paper) and the process was tedious.  The building itself was hot in the summer and cold in the winter but we just dressed for it.

An E-commerce facility today is only similar in that the box is still big and there are still metal racks but that is about it.  In the first place, those racks may not be used to store finished goods but components that can be used to create a finished good.  Maybe it is a shirt and tie that are packaged into a set.  Maybe it is a cell phone, battery, charging cable, etc packaged into a retail package. 

This approach is designed to give the end customer flexibility.  Order the color, size, accessories that you want to make the purchase unique to you and the E-commerce company "fulfills" that order to your specification.  So, now, you have "fulfillment" centers instead of warehouses and they are occupied by dozens of workers using computers to configure your package to your needs.  In many cases the components that these workers put together are not retrieved by a human but by a robotic retrieval system.  The robots, and the human workers, all receive their instructions from on-site servers processing thousands of orders a day.

So, the old warehouses of my school days are now air conditioned, filtered, well-lit, high tech "factories" with their own small data center.  The challenge for the HVAC systems is how to handle three different requirements in those buildings.

The area used by workers to fulfill the orders needs comfortable temperature conditions but only in the lowest 7 or 8 feet of the building height.  The rack area where the robots run around might need temperature control for the entire 35 or 40 feet of the building height depending upon the product storage requirements.  And the on-site data center needs filtered fresh air, or evaporative cooling, to keep the servers running at an affordable operating cost. 

And to compound the problem the E-commerce company is probably growing so fast that the system configuration today will be obsolete in 2 or 3 years.

In order to satisfy all of those requirements, and provide future flexibility, requires the kind of analysis that a tool like CFD can provide.  Being able to create the building and experiment with equipment locations and sizes before the space is built, or reconfigured, has tremendous value.  Mistakes can be avoided and performance can be optimized to the requirements of the area being served.  Mestex has invested heavily over the last 15 years in CFD software, computers, and training so that we can perform the kind of analysis required.  We use this tool almost daily to help designers and owners make the best equipment selection for their project.

If you are involved in the E-commerce world and need to know the best type and location of the HVAC equipment for your project please feel free to contact us at www.mestex.com.

Virtual Reality

In recent days a company created a virtual world that showed the application of a real world product.  In their case the real world product was firearms.  The object of the game was basically to kill as many of your enemies as possible using a firearm of choice.  I will not go into the sociopolitical discussion of whether or not this is a good thing.  It was financially successful for the company to develop, so from their perspective I’m sure it is considered a success.

My company also creates virtual worlds that show the application of real world products.  In our case the real world products are heating, air conditioning, and ventilation products.  The object of our virtual world is to improve comfort and in some cases actually save lives.



Virtual Building and Temperature Simulation

In our business the control of temperature and air is what our products are intended to do.  The problem is that air is invisible.  So how can we know in advance that our products will make someone comfortable or prevent a drug from becoming unusable or even dangerous.  The way we do this is by creating a virtual world.

In our business we use software called CFD, “Computational Fluid Dynamics”, to create virtual buildings filled with equipment, storage racks, and temperature sensitive products.  After this model is created we then create virtual HVAC equipment.  This virtual equipment is modeled after our real equipment.  These HVAC units are then positioned where we believe they will produce the best results.  Many times our experience provides the best result.  However, sometimes the application is more difficult.  In those cases we let the computer determine the best location and best characteristics of our product in order to provide the best result.



Air Particle Tracks through the Building

This process can sometimes take several days but the end result is a building that performs the way that it was intended to perform.  And when that happens, occupants are more comfortable or temperature sensitive drugs continue to be stored at the proper temperature.

Virtual worlds can be created for many different reasons.  We have chosen to create virtual worlds that provide great benefit to mankind.

A Simple Concept That Saves Big Dollars

Or, How a Bad Hair Day Can Save You Thousands Of Dollars...



Airflow Pattern From An Air Curtain

You have probably walked through a doorway some time in your life that totally messed up your hair…you had just experienced an “air curtain”.  So why would someone want to install one of these things if they can be so annoying?  The reason, as is most often the case, is to save money. 

“Air curtains” or “air doors” have been around for decades.  You find them on some commercial buildings up north in entry vestibules as a way to help isolate the cold outdoors from the heated indoors.  You also find thousands of them on industrial and warehouse buildings because of the large number of “dock doors” that are constantly being opened and closed.  Every time one of those doors opens, the building has the potential to lose heat to the cold outdoors…and that costs money.  Most facility managers realize this instinctively (or it was passed down from one generation to the next) but I am not sure how many have actually tried to calculate just how much energy and money is lost through a single dock door.

Here at Mestex we produce a number of “air curtain” products under brand names such as King, Applied Air, and LJ Wing.  All of our “air curtains” are intended for use on the large dock or ramp doors that you find in industrial or warehouse buildings.  The purpose of this little article, though, is to highlight the operating cost savings from using an “air curtain” rather than to tell you which one to use.  In order to do that we turned to one of our engineering analysis tools that we employ for more complicated application studies…Computational Fluid Dynamics, or “CFD”.

In some of our other blog articles we talked about CFD and how it works so I won’t go into that in detail but suffice to say that we can predict the temperature and airflow impact of HVAC equipment in a building…and do so with surprising accuracy.

For this study we created a model of a 20,000 square foot warehouse with a 20 foot height.  We then added a 14 foot wide by 16 foot tall dock door.  The model included R-13 wall construction and R-11 roof construction.  Our target inside design temperature in winter was set at 68 degrees F.  We threw in a few storage racks and a heating system on the opposite wall of the building from the dock door…about as far away as we could put it.  We then ran the CFD software with winter weather conditions from Syracuse, Chicago, and Atlanta.  (The little video above shows the airflow patterns in the warehouse and around the open door.)

Our CFD study showed a heating requirement of 3.5 million btuh in Syracuse without an “air curtain” and only 2.4 million btuh with an “air curtain”.  In Chicago it was 3.75 million versus 2.5 million, and in Atlanta it was 2.25 million versus 1.75 million.  You can see that the savings in btuh were significant in each case…even in Atlanta.

Converting this into dollars and cents translates into a savings of almost $21,000 per year in Syracuse, $19,000 dollars per year in Chicago, and $3,600 per year in Atlanta.  When you consider that a typical “air curtain” for a 14x16 dock door only costs about $18,000 completely installed and operational you can see why facility managers in cold climates can easily justify the investment…I mean, who doesn’t want a 1-year payback?  Even in “Hot-Lanta” the payback is 5 years just for heating…and the concept also helps with cooling.  We have also calculated the internal rate of return with various hours per day of door opening but that analysis is too lengthy for this already lengthy blog article.  If you want more information about the IRR or want information for your city just contact us at www.appliedair.com using the “contact us” selection under the “support” tab.

 

Using CFD in the HVAC Industry

One of the most useful design analysis tools now being used in the HVAC industry is something called "CFD".  "CFD" stands for "Computational Fluid Dynamics" and it provides insights into potential building performance that no other analysis tool can provide.  While CFD software has been in the marketplace for over 20 years it is still fairly rare in the HVAC environment.  CFD was originally used in the aerospace and fluid process industries.  It is now the number one analysis tool used in Formula One and automotive design in general.  CFD is also now widely used in the data center design community.

The reason that CFD is so widely used in those high technology industries is that CFD allows the designer to "see" air in a space...it's temperature, it's direction, it's velocity, and even it's density and moisture content in some cases.  Mestex has been using CFD for years to help engineers and building designers understand the best product for their building and the best place to locate that product. 

By creating a 3D model of a building and it's contents, and then adding a model of the proposed cooling or heating product, the CFD user can evaluate just how well the proposed system will satisfy the design requirements.  More sophisticated versions of CFD software, such as the software used by Mestex, can actually help the designer optimize his application by letting the computer modify the equipment location and operating conditions to get a result that is as close to the design target as possible.

CFD studies can be very complicated, and might take several days to complete, but the end result is so valuable that it is worth the time.  Mestex recently completed a study for a pharmaceutical company that assured the company that their multi-million dollar inventory would be kept at the proper temperature anywhere in their warehouse.  No other analysis tool can provide that type of owner security.