Thermal Conductance (UA) ?

[klonoa]

Hi all,

I am new here. I am recently working on a school project which requires a temperature model of domestic fridge. I have gone through a few papers and I am sure I am going for a really simple model which applies the newton's law of cooling. In such model, all those papers use a parameter, Overall Thermal Conductance (UA), but I dont seem to be able to find the range of this UA value for domestic refrigerators. Some paper refer this value with the unit of (Btu/h·ft²·°F) and I think it is what is used in HVAC field.

I wonder if any of you know the range of this UA value and where can I find such value? I have tried to search the internet for a long time and dont seem to come across the useful information I need. Hopefully I can get some help here. Thanks a lot.

-klo

[Tesla]

Hi klo and welcome to our forum.
Depending on where you are (imperial or metric) will determine which formula you use. Imperial (Btu/h·ft²·°F) = Metric (5.68W/m²K) or 1W/m²K = 0.176Btu/h·ft²·°F. These are for conductance (c). I think a cool room would be simpler due to the fridge often having the condenser and sometimes heaters on the outside.

[klonoa]

Hmm.. I thought the UA refers to the fridge material? (the insulation or so?). In a paper I found this value ranges from 0.9 to 1.1 Btu/hr.ft2.°F. But there is no reference so that I am not sure if this range of value makes any sense at all. Any idea?? Thanks

-klo

[Tesla]

Hi klo
Perhaps this calculation will help http://www.refrigeration-engineer.com/forums/showthread.php?t=20599&highlight=calculation+cold+room understand UValues and other related parameters. I did a quick google search and didn't find much but I'm sure if you tried harder - maybe a manufacturer would be helpful.

[wambat]

Hi all,

I am new here. I am recently working on a school project which requires a temperature model of domestic fridge. I have gone through a few papers and I am sure I am going for a really simple model which applies the newton's law of cooling. In such model, all those papers use a parameter, Overall Thermal Conductance (UA), but I dont seem to be able to find the range of this UA value for domestic refrigerators. Some paper refer this value with the unit of (Btu/h·ft²·°F) and I think it is what is used in HVAC field.

I wonder if any of you know the range of this UA value and where can I find such value? I have tried to search the internet for a long time and dont seem to come across the useful information I need. Hopefully I can get some help here. Thanks a lot.

-klo

Heat Transfer in a Heat Exchanger
Forced Convection (flowing) Gas - Forced Convection Gas : U = 10 - 30 W/m2K (heat exchangers gases and for Steel : U = 25.0 W/m2K, Aluminum : U = 25.0 W/m2K

I hope this helps you