# $\Delta T$, temperature units. How to use fahrenheit in this formula

To calculate the power in a fluid with a flow, the following formula is applied:

$$P = \Delta T \rho c_p \times flow$$

$\Delta T$ can be entered as both Kelvin and Celsius. But what if I want to use Fahrenheit? Is there any formula for this?

Reason is I'm making a web application that calculate some stuff. I have full unit support. I live in Europe so we always use Celsius or Kelvin. But, are americans using fahrenheit for calculations in general? If not, then maybe I can skip it all together.

• Multiply by 5/9 – Mike Dunlavey Jan 31 '14 at 14:22
• Thx for answear! Haven't added the feature yet in my app but it will be available in next version. Here's my app btw, sizepipe.com. – Joe Jan 31 '14 at 18:57
• Looks cool! Good luck. – Mike Dunlavey Jan 31 '14 at 20:34

Given that the conversion from Celsius to Fahrenheit is given by:

$$T_F=T_C\cdot 1.8+32$$

Then,

$\Delta T_F=T_{F_2}-T_{F_1}=T_{C_2}\cdot1.8 +32 -T_{C_1}\cdot1.8-32 = \Delta T_C\cdot1.8$

Or, to be used in that case,

$$\Delta T_C = \frac{\Delta T_F}{1.8}$$

So the formula becomes

$$P =\frac{\Delta T_F}{1.8} \rho c_p \times flow$$