Search results for query: *

Sounds good. I assume I use the 355 BTU/ sqft hr to get the Q from solar radiation??? I guess I also need to take reflectivity into account with Q = emmesitivity X Stefan-boltmanz eq X (Tsurface - Tsky)^4 I think those are the equatins I am just not sure how to put it all together. SO I...

VPL - Wow you are very unhelpful. I am asking questions because I thought some people on this board with background in the subject matter could help me out. Really if you don't have an answer or don't like me for some strange reason then don't read my post and don't respond. What information...

MintJulep - I looked at those equations but I am not sure how to use them. Can you give me an example? FOr instance what are the following: a = solar radiation absortivity of a surface I = global solar irradiance ?Qir = infrared radiation transfer of sky temperature to surface

Ok as I said above I understand the heat transfer via conduction/convection. I can do that. I jsut don't know how to do the solar part. For example I have a inside temperature of 140F. My outside temperature is 120F. Typically you would see the heat transfer go thru the wall to the...

I might be missing somehting but I would find the heat transfer thruogh the pipe. YOu need the metal conductivity and thinckness, and the insulation conductivity and thickness alogn with the pipe length (You can assume a length to start). Then you can figure the amount of heat transfer you...

Can somebody provide me with the equations and show me how to do this? I don't have that book and I am looking for figure this out quickly. I just don't know the equaitons or how to add them into the thermal resistance. MY surfave emmissivity is assumed to be 0.9 right now.

I will use common objects to make this a bit more easy to ask. Lets say I have a medium sized enclosure (say a box that is around 3 feet by 2 feet by 2 feet). I have a internal heat load (given) and I also have a internal temperature that I would like to maintain (Lets say it is 135F). So I...

Aren't you missing a whole bunch of data? In reality don't you need to determine the UA values for the walls and ceiling and then figure out what you heat transfer out of the room is naturally. Then you can determine what you need to do to maintain a 10F temp difference on a 105 outdoor air...

IRstuff - Here is how I see it. I do understand what you are saying but my goal is to maintain a specific temperature in a given space. Therfore the steps to take would be to look at the given temperature and the outdoor air desing temperatures (both hot and cold). Solving for all the UA...

DRWeig - I agree with you totally. IRstuff - I am nto sure what you are talkign about. The deltaT is the difference in temperature between the inside area and the outside area or between the inside space and the garage space. If you want to keep a house at 80F and the outdoor design...

Sorry I have to dissagree again. I don't htink that is how it works cause the numbers jsut don't make sense. When you think about it Heat transfer or Q is equal to UA(Delta T). So if your wall UA value is 45 and lets assume a delta T = 40F then Q is 1800 That is just for one wall. If you do...

vpl - I beleive what you stated is not correct. When you are looking for the overall U value you use the equation: U = 1 / (R1 + R2 + R3...) However I don't think you add the invers of the UA values together to get an overall UA value???? Just htink abotu the math... Say the Wall UA=45 and...

I don't think that answered the basic question. How do you get the overall UA value for the room. Is the process simply you add the UA value you get for the wall to the UA value for the ceiling? How about this as an example. Pretend you have a two storry building that is open and has...

I know the basics of convection and conducion. I am havign a bit of a hard time tryign to figure out how you determine an overall UA value for a space if you need to look at walls, ceilings and floors - I know how to find each UA value but I am confused as how to find the overall UA value...

How do you add UA values for a space if you have walls and a ceiling. I have a space and I have walls built up of several materials and a ceiling and then an air gap and a metal outter surface (call it a roof). I know how to find the U values for the wall or the ceiling and therefore I can...

I understand there is nto a lot of inforamtion. I don't have all of the information at this time. Air enviromnet is 120F and there will be some airflow on the outside of the pipe. Don't have a mass for everyhitng- changes depending on location. Basically I have a pipe that will run thru some...

Ok I will look at the textbook but I had a hard time trying to follow the equations and methodology in the last book I went thru. I was hoping somebody could break it down for me so I could understand the process. For example imok2 how did you come up with those heat transfer values and what...

Ok so here is my problem. I have several pipes that are carying very hot compressed gas. Some of these pipes will be running near areas that are constructed of aluminum. I want to make sure that I do not overheat the aluminum but before I go puttign a ton of inssulation on the pipe I woudl...

That might be true but is your black globe in direct sunlight? If it is on your desk I assuem it could still be gettign sunlight but not a tremendous amount. If it were outside I would think it owuld get much hotter.

I understand what it is and how it is typicalyl measured. However I am not familiar with typical values are in correspondence with say the dry bulb temperature. I am looking for a table with typical vaues that I could use to do some approximate analysis. For example is there any data out...