Page 3 of 3 FirstFirst 123
Results 31 to 39 of 39

Thread: .0001 Micron Dust Collector Filtering...

  1. #31
    Join Date
    Jun 2004
    Location
    Burlington, NC
    Posts
    821
    My cyclone is outside. In the winter the outlet of the cyclone is connected to the filters inside, to return the heated air to the space. In the summer, the outlet is diverted to the outside since I have no HVAC.

    Perry

  2. #32
    Join Date
    Apr 2010
    Location
    Nashville, TN
    Posts
    1,544
    I tend to find it hard to believe as well that if you pull BTUs out, and do not replace them, that the temperature stays the same.

    Offering a couple of suggestions to explain the shops that are not noticing a temp change:
    1. Your 1200 CFM blower is not likely pulling 1200 CFM. The exhaust volume is likely much less and therefore your air changes are less than predicted.
    2. There is stratification of air temperatures in the shop. It is cooler at the floor than the ceiling. Most of the exhaust points are going to be closer to the floor. Therefore, you get the coolest air out and is immediately replaced with slightly warmer air from the ceiling. This will help "temper" the effect of the cooler make-up air.
    3. Short runs of the DC will give the HVAC equipment a better chance of keeping up.

    I'm not trying to discredit anyone saying they haven't noticed temperature change. That is a measurable fact. I am pointing out that there are likely reasons for that. It is not because the rules of Thermo and heat balance only applies to certain shops.

    Mike


    Mike

  3. #33
    Another thing to keep in mind is what the shop is attached to. Is it a stand alone structure or is it part of a much larger building? Also (in my case at least) where the heat vents and thermostats are, which part of the building is properly insulated and which part of the building has had the air leaks sealed up all have a large effect on how the temperature changes when the blower is running.

    Also as has been said before the items in the room store a lot of heat. I often turn the heat way down at my house when I know I am going to be away for a couple days and when I come back and turn it back on the furnace may only run for 20 minutes and the air is up to 65degrees but since the structure of the house and everything in it is still at 50 degrees the house feels very cold. It usually isn't until the next morning that the house feels comfortable. I assume the same thing is happening in reverse when the blower is running in the winter. Add to that the fact that dust collection is usually only run for short periods at a time and the overall temperature change can be less than expected.
    Universal M-300 (35 Watt CO2)
    Universal X-660 (50 Watt CO2)

    Hans (35 watt YAG)
    Electrox Cobra (40 watt YAG)


    Glass With Class, Cameron, Wisconsin

  4. #34
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,648
    Quote Originally Posted by Steve Milito View Post
    You really can't compare a basement shop to a stick framed shop above grade. A basement has 3 or more foundation walls and floor (ie concrete) acting as a heat sink to earth. Therefore if your average earth temperature at 5 ft or so is 50 degrees F, then the basement will pretty much be the same temperature. You can change the air temperature by sucking in cold air, but it will return to base temperature in a reasonable time because the earth adds the energy necessary to warm up the air.

    A stick framed building has minimal heat capacity. Therefore, once you change the air temperature, it requires the addition of external energy to add heat to the system. Your equipment may mitigate the situation for a short period of time, but sooner or later you will need to pay the piper and add energy to warm up not only the air but also the now cold equipment.
    You are right about a stick framed building. However, I wasn't trying to compare my shop to anyone else's. What I said was that in the case of my basement shop the temp. does not drop much even after an hour of continuous exhaust with my 1200 cfm fan. I have a thermometer right near my spray booth, and it does not go down more than 1 or 2 degrees even on the coldest Winter day. I have a digital one about 30 feet away; it changes no more than 1 degree. I'm not ignoring a temp. drop - it just doesn't happen. When I'm done, I turn the boiler back on and it runs for maybe 10 - 15 minutes, and it might cycle a little more frequently than normal for the next hour. I really don't know where all the makeup air comes from. Some comes from the house upstairs, some comes down the chimney. Whatever comes down the chimney gets pre-heated some as it makes it's way into my shop. I heat the upstairs with a wood stove (and it's draft is just fine when I'm running the exhaust fan), so if some or even all of the make up air is coming from there it's OK with me because that heat is free. Remember, we're only talking about 10 air changes an hour. There isn't much heat in that that has to be made up.

    As a guy who worked for over 30 years as a R&D engineer in a business where managing heat transfer was the very basis of the business, I learned that while equations never lie applying them to the empirical data at hand is not always a straight forward proposition. When the equations didn't fit our data, the source of the problem was almost never bad data.

    John

  5. #35
    Quote Originally Posted by John TenEyck View Post
    You are right about a stick framed building. However, I wasn't trying to compare my shop to anyone else's. What I said was that in the case of my basement shop the temp. does not drop much even after an hour of continuous exhaust with my 1200 cfm fan. I have a thermometer right near my spray booth, and it does not go down more than 1 or 2 degrees even on the coldest Winter day. I have a digital one about 30 feet away; it changes no more than 1 degree. I'm not ignoring a temp. drop - it just doesn't happen. When I'm done, I turn the boiler back on and it runs for maybe 10 - 15 minutes, and it might cycle a little more frequently than normal for the next hour. I really don't know where all the makeup air comes from. Some comes from the house upstairs, some comes down the chimney. Whatever comes down the chimney gets pre-heated some as it makes it's way into my shop. I heat the upstairs with a wood stove (and it's draft is just fine when I'm running the exhaust fan), so if some or even all of the make up air is coming from there it's OK with me because that heat is free. Remember, we're only talking about 10 air changes an hour. There isn't much heat in that that has to be made up.

    As a guy who worked for over 30 years as a R&D engineer in a business where managing heat transfer was the very basis of the business, I learned that while equations never lie applying them to the empirical data at hand is not always a straight forward proposition. When the equations didn't fit our data, the source of the problem was almost never bad data.

    John
    Clearly the makeup air isn't coming into the shop from outside.

  6. #36
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,648
    Quote Originally Posted by Steve Milito View Post
    Clearly the makeup air isn't coming into the shop from outside.
    You might want to rethink that. If you meant to say it's not coming into the shop directly from outside, without first being preheated, that could be true. That could explain why the temp. doesn't drop much. I really don't care; it works and that's all that matters.

    John

  7. #37
    Join Date
    Apr 2010
    Location
    Nashville, TN
    Posts
    1,544
    There are waaay too many variables involved to absolutley say whether the temp is going to fluctuate, and by how much, based soley on venting outside or not. In otherwords, can anyone guarantee absolutely that the temperature will not fluctuate for any shop under any conditions when venting outside? In turn, can anyone say that it will always fluctuate X degrees when you vent outside? It is purely an application specific question.

    However, if you remove (or add) heat, the temperature has to change. Whether or not it is a measurable difference, depends on all the other variables involved.

  8. #38
    Quote Originally Posted by John TenEyck View Post
    You might want to rethink that. If you meant to say it's not coming into the shop directly from outside, without first being preheated, that could be true. That could explain why the temp. doesn't drop much. I really don't care; it works and that's all that matters.

    John
    I'll clarify. If you are truly moving 10 volumes of air / hour through your shop on the coldest day of the year in New York State then either the temperature changes or you are replacing the air with heated air from some other source. The residual heat in your smoke stack is an unlikely candidate for the lost heat. The most likely explanation is that the make up air is heated air coming from your conditioned space. The conditioned space needs it's own makeup air which can only be cold air from outside. Since you home heating system is likely large, and the volume of the living space greatly exceeds the volume of your shop, the temperature change in is mitigated. Additionally, you are adding energy into the system to maintain a relatively constant temperature.

  9. #39
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,648
    Quote Originally Posted by Steve Milito View Post
    I'll clarify. If you are truly moving 10 volumes of air / hour through your shop on the coldest day of the year in New York State then either the temperature changes or you are replacing the air with heated air from some other source. The residual heat in your smoke stack is an unlikely candidate for the lost heat. The most likely explanation is that the make up air is heated air coming from your conditioned space. The conditioned space needs it's own makeup air which can only be cold air from outside. Since you home heating system is likely large, and the volume of the living space greatly exceeds the volume of your shop, the temperature change in is mitigated. Additionally, you are adding energy into the system to maintain a relatively constant temperature.
    I never said it couldn't be as you describe. All I said was the temp. in my shop doesn't change much with the exhaust going outside and that allows me to spray year round. You and others said it just couldn't be true but after I insisted that it is (and it is) you've now developed an explanation of how it could be. Thanks.

    John

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •