Mixture temperature is the mass- and specific-heat-weighted mean of the two fluids, which is what an energy balance gives when neither fluid changes phase. Mixture specific heat is the plain mass-weighted mean.
Corrected 2026-09: the previous version read the specific heat of Dichlorodifluoromethane R-12 saturated -40oF as 0.528 instead of 0.211, and of n-Butane, 32oF as 0.94 instead of 0.55. Those two rows sit out of alphabetical order in the source table and the lookup beside them assumes the table is sorted, so each picked up the fluid above it. Both now read the value the table itself lists.
Specific heats are the workbook's own table in Btu/lb-F, which is numerically the same number in kCal/kg-C, so the table serves both unit systems. Ten fluids are listed there with no specific heat and count as zero.
Selecting _Other replaces the table value with the specific heat you type.
