AnalysisChamp.com Blog

A new AnalysisChamp.com Complex Converter user recently tried to convert using “cubic feet” and couldn’t find them in the list of units.  Are they there?  What are they called?  The power of the complex converter lies in its ability to handle any kind of unit expression.  Cubic Feet are expressed as “ft^3” or “ft*ft*ft” or “ft^2*ft” or “in^2*ft” or any unit of length taken in three multiples.

Example Conversion ScreenShot

This technique can be combined with other base units to evaluate complex conversions.  An example is converting “gallons per second” (GPS) into “cubic feet perminute” (CFM).

The input string, “gal/s” and output string, “ft^3/min” are entered into the Complex Converter and evaluated using the common Windows syntax of Visual Basic.  That’s why units like “GPS” or “CFM” are not found in the list of unit names.  They are not needed because the Complex Converter uses expressions instead.  (Most online converters are hindered by the limits of unit names available, The Complex Converter has no such limit.)

Try it out and experiment with your own daily calculation examples!

I came home to a bad surprise tonight; my refrigerator door was left open all day and the food inside was warmed up! I figure there is 50 lbm of food (with properties of water) affected. Most of the food in the freezer is still frozen and the food in the refridgerator is still chilled but needs to cool down 40 degrees F as soon as possible. I can get some ice but how much? Perhaps dry ice is better (it’s colder, doesn’t melt and bathes the food in carbon dioxide).

Heat to draw from food, Q = mass * specific heat * temperature change; wikipedia.org/wiki/Specific_heat gives property for water as 4.1813 J/(gm*degK) so Q = 50 * 4.1813 * 40 [lbm * J/(gm * degK) * degR] = 1997 BTU (degR = DegF difference). How much dry ice is needed to extract this much energy when sublimating into a gas?

The latent heat of sublimation for dry ice is given at www.continentalcarbonic.com/dryice/dryicemsds.php as 246 BTU/lbm. 1997 BTU / 246 (BTU/lbm) = 8.12 lbm dry ice needed to chill things down. I bought 10 lbm and put 2/3 in the refrigerator and 1/3 in the freezer. After 2 hours the freezer was at 10 degF and the refrigerator was a 45 degF with half the dry ice remaining.

The calculations are combined at follows: http://AnalysisChamp.com/EEX/ExpEval Note: When working with temperatures: Use absolute whenever performing calculations and when working with temperature changes – degF changes are = degR and degC changes are = degK.

Reply with any questions or comments and keep on crunching those numbers!