Tag: forced air

Air Cooling Maintenance?

Published on by Brian FarnoLeave a comment

The time has finally come, and spring is here! The Cincinnati Reds are playing, Spring Soccer is happening early on Saturday mornings, and the FC Cincinnati Stadium is bustling here in Cincy. With that, temperatures are climbing, the grass and weeds are growing, and more and more families are out walking around and doing outdoor activities. With this, also comes warmer temps, and lots of spring allergies in the Farno household. As a dad, I have stepped into my role pretty well by trying to delay turning on the air conditioner until everyone else in the house is plotting my demise. This year, I achieved it by putting off the routine maintenance of the condensing coils.

In case you weren’t aware, here in the Midwest, where pollen runs rampant and the winds have been strong this year, it is a great idea to clean out the condensing coils on your home’s A/C system before turning it on for the year. Unfortunately, your home A/C system is not maintenance-free like the Cabinet Cooler Systems EXAIR offers; at the same time, your home needs a lot more than a few thousand BTU/hr of cooling capacity. When we first bought the home, I didn’t know this was a thing, as the home I grew up in didn’t have central air. We rocked Window A/Cs, and my parents still do. So, cleaning the outdoor unit was not part of my knowledge base. This is something I learned once the air conditioner wasn’t working, and I started to troubleshoot.

The main purpose of the condensing coils is to strip all the heat out of the refrigerant and get it to “condense” back into its liquid state to be pushed back through the orifice and continue to cool the air that is being passed over the A Coils inside the house. These coils are covered in fins that are very tightly spaced. The outside unit has a large fan that pulls the surrounding air in through the coils and exhausts the hot air up out of the top. There is no filter on that incoming ambient air, though, so all the leaves, cobwebs, pet hair, pollen, dirt, mulch, you name it, get pulled up into these fins. Over time, this starts to get a buildup, and the cooling fins will start to lose their efficiency. The fan won’t be able to pull as much air through, and eventually, the gas doesn’t get condensed, which then reduces the cooling and can cause other bigger issues. This is just like a refrigerant-based A/C panel cooler in a facility. Most of the time, they have at least a small filter on the air intake to try and reduce the contamination of the condensing coils. So I clean the A/C condenser at my house using a coil cleaning solution diluted down, a pump sprayer, and a regular garden hose.

The main thing to remember when cleaning this is that the majority of the dirt is from the air being pulled into the center by the fan. So I rinse the coils from the inside out and make sure I have free passage all the way through. The water doesn’t need to be a high-pressure rinse like an OmniStream nozzle or one of BETE’s NF Nozzles, just a simple low-pressure stream of water to get between the fins and push all contaminants as well as rinse the solution away. Remove any leaves or other unwanted debris from inside the unit and then bolt the fan and cage back down. Then let the family enjoy some cold air inside the house.

This type of maintenance is something that easily gets overlooked when looking at refrigerant-based electrical panel coolers. That is where EXAIR Cabinet Cooler Systems shine. The only filter you have to worry about is a redundant point-of-use compressed air filter that is included with the Cabinet Cooler Systems. No chemicals needed for cleaning, no water, no mess to change out a compressed air filter, just long-lasting performance. If you want to talk about how to change your control panels over to Cabinet Cooler Systems, contact an Application Engineer today.

Brian Farno, MBA – CCASS Application Engineer

BrianFarno@EXAIR.com
@EXAIR_BF

Convective Heat Transfer: How Do We Use It?

Published on by Brian FarnoLeave a comment
Vortex Tubes have been studied for decades, close to a century. These phenoms of physics and the theory behind them have been discussed on this blog before. Many customers gravitate toward Vortex Tubes when needing parts and processes cooled. The fact of the matter is there is still more to be discussed on how to correctly select the which product may be needed in your application. The reason being, area, temperatures, and air flow volumes play a large role in choosing the best product for cooling. The tendency is to say, well I need to cool this down as far as possible so I need the coldest air possible which leads to the assumption that a Vortex Tube will be the right solution. That isn’t always the best option and we are going to discuss how to best determine which will be needed for your application. The first step, is to call, chat, or email an Application Engineer so that we can learn about your application and assist with the implementation of the Vortex Tube or other cooling product for you. You may also want to try and take some initial readings of temperatures. The temperatures that would help to determine how much cooling is going to be needed are listed below:
  • Part temperature
  • Part dimensions
  • Part material
  • Ambient environment temperature
  • Compressed air temperature
  • Compressed air line size
  • Amount of time desired to cool the part: Lastly desired temperature
With these bits of information, we use cooling equations to help determine what temperature and volume of air will best suit your needs to generate the cooling required. One of the equations we will sometimes use is the Forced or Assisted Convective Heat Transfer. Why do we use convective heat transfer rather than Natural Heat Transfer? Well, the air from EXAIR’s Intelligent Compressed Air Products® is always moving so it is a forced or assisted movement to the surface of the part. Thus, the need for Convective Heat Transfer.
Calculation of convection is shown below: q = hc A dT Where: q = Heat transferred per unit of time. (Watts, BTU/hr) A = Heat transfer area of the surface (m2 , ft2) hc= Convective heat transfer coefficient of the process (W/(m2°C), BTU/(ft2 h °F) dT = Temperature difference between the surface and the bulk fluid (compressed air in this case) (°C, °F)

The convective heat transfer coefficient for air flow is able to be approximated down to hc = 10.45 – v + 10 v1/2

Where: hc = Heat transfer coefficient (kCal/m2 h °C) v = relative speed between the surface of the object and the air (m/s)

This example is limited to velocities and there are different heat transfer methods, so this will give a ballpark calculation that will tell us if we have a shot at a providing a solution.  The chart below is also useful to see the Convective Heat Transfer, it can be a little tricky to read as the units for each axis are just enough to make you think of TRON light cycles. Rather than stare at this and try to find the hidden picture, contact an Application Engineer, we’ve got this figured out. convective_heat_transfer_chart

1 – Convective Heat Transfer Chart
Again, you don’t have to figure any of this out on your own. The first step to approach a cooling application is to reach out to an Application Engineer, we deal with these types of applications and equations regularly and can help you determine what the best approach is going to be.
Brian Farno Application Engineer BrianFarno@EXAIR.com @EXAIR_BF
1 – Engineering ToolBox, (2003). Convective Heat Transfer. [online] Available at: https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html [02/10/2021]