How to Measure Air Infiltration

Adding r-value to a 40 yr old cold storage freezer by adding 2 inches of spray foam and sealing cracks. Also applying for an incentive based on kWh saved per year. Calculations are getting extremely complex. Ran a test of shutting the freezer down and logging temperature every 10 seconds while it cooled off.

The calcualation for conductance is pretty straight forward but comes out to a much larger number (10x) than the actual total heat gain of (air mass)(enthalpy)(deltaT). What is going on here? Is concrete slab floor absorbing a bunch of this heat?

The plan was to do this shut-off-and-log temps test before and after insulating. But the incentive offerer is not confident we are going to get a reliable difference - nor am I. Comments? Help?

Hi marinechiller
I have seen them do this on TV to domestic houses where the seal up the door and use a giant fan or two and measure the air flow and leakage via a laptop. I could only imagine that they measure the flow rate once pressureised through the fan, this could/should also be done with a negative pressure which would be more relevant on a cold room.

Thanks tesla, that was my first approach. Companies I contacted with blower doors said they can only give a number at negative pressures. No straight conversion to natural infiltration nor to btu loading.

I have been through this sort of calc before and it's pretty heafty to say the least. Professors Cleland and Cleland taught this at Massey University in Palmerston North NZ, you could do a Google search and there is also an Asian dude who has a calculation for it. I supose it would go something like work out an effective hole size in the room from pressure leakage, then take the enthalpy difference which would equal what passes in passes out which would give the energy transfer rate. The infiltration rate is different from a service load like doors opening and closing.
Dave Nichols who taught me also at Petone Tech NZ used to consult and also did the exact calculation for sealing up rivet holes in containers. So if you find it on a search please put it on this post so as we can all learn from this reference.
I do remember now I did answer a post on this forum some years ago - just can't remember what the result was.
http://www.refrigeration-engineer.co...t=infiltration from Frank
I Search for the other one but can't find it.

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Originally Posted by marinechiller

Adding r-value to a 40 yr old cold storage freezer by adding 2 inches of spray foam and sealing cracks. Also applying for an incentive based on kWh saved per year. Calculations are getting extremely complex. Ran a test of shutting the freezer down and logging temperature every 10 seconds while it cooled off.

The calcualation for conductance is pretty straight forward but comes out to a much larger number (10x) than the actual total heat gain of (air mass)(enthalpy)(deltaT). What is going on here? Is concrete slab floor absorbing a bunch of this heat?

The plan was to do this shut-off-and-log temps test before and after insulating. But the incentive offerer is not confident we are going to get a reliable difference - nor am I. Comments? Help?

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I think that it is wrong approach to fix old building. I understand that you put insulation on the walls from outside. What about floor and roof? Probably, roof in bad shape and a lot of heat comes through the roof. No infiltration through the cracks because this is not house. If you have crack, it full of ice and this ice block the actual infiltration. Don't forget when you cool the freezer, you handle heat that comes from outside and you cooling off the product in the freezer.

Roof was redone in 2005. Evidence of air infiltration is present where floor meets wall (product actually melted above a visible gap).

Freezer at -10F

Hi marinechiller
Just wondering if you had a few pics to share with us on this one?

Stay tuned for pics. We have decided to use multiple variable regression analysis to come up with an annual kWh savings number. Running the post insulated test this weekend.

Turns out there is still something happening that our numbers and measurement data is not describing. We have demonstrated that the load is much less post-insulation, but have approached some local 'experts' to try and get a proper analysis method.Attachment 10438Attachment 10439