The overall heat transfer coefficient, or U-value, refers to how well heat is conducted through over a series of resistant mediums. Its units are the W/(m2°C) [Btu/(hr-ft2°F)].
How do you calculate the U-value of a heat exchanger?
Typical Overall Heat-Transfer Coefficients
- Free Convection Gas – Free Convection Gas : U = 1 – 2 W/m2K (typical window, room to outside air through glass)
- Free Convection Gas – Forced liquid (flowing) water : U = 5 – 15 W/m2K (typical radiator central heating)
What is the U factor on a heat exchanger?
The U-factor or U-value is the overall heat transfer coefficient that describes how well a building element conducts heat or the rate of transfer of heat (in watts) through one square metre of a structure divided by the difference in temperature across the structure.
What is a good heat transfer coefficient?
As mentioned earlier in the article the convection heat transfer coefficient for each stream depends on the type of fluid, flow properties and temperature properties. Some typical heat transfer coefficients include: Air – h = 10 to 100 W/(m2K) Water – h = 500 to 10,000 W/(m2K).
How is UA calculated?
That is, UA = 954 BTU/hr-F, where U is the conductance of the building and A is the surface area of the building. When the average outside temperature is greater than 56.5 degrees F, the building heating system is not activated….
| Type of Window | R (ft2-hr-F/BTU) |
|---|---|
| Single-glazed | R = 0.9 |
How do you calculate heat transfer coefficient experimentally?
For determining the heat transfer coefficient the chip is replaced with a heating coil. The power input to the heating coil is obtained by measuring the input voltage and current. Temperature measurement for varying heat inputs is done using RTD thermocouples.
How do you calculate heat transfer coefficient from thermal conductivity?
The most common way of doing this is by dividing the thermal conductivity of the convection fluid by a length scale. It is also common to calculate the coefficient with the Nusselt number (one of a number of dimensionless groups used in fluid dynamics).
Is lower U-value better?
U-values can tell you how well an insulated glass unit (IGU) will hold in heated or cooled air. The lower the number, the better the insulating performance. U-values generally range from 0.1 (very little heat loss) to 1.0 (high heat loss).