Collector performance-curve variable calculator

The reduced-temperature coordinate compares the fluid-to-ambient temperature difference with incident irradiance.

Units

x = \frac{T_{\text{in}} - T_{\text{ambient}}}{I}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

x = \frac{150 - 70}{250} = 0.32

Symbol	Meaning	Unit
$x$	reduced-temperature curve coordinate	h·ft²·°F/Btu
$T_{\text{in}}$	fluid inlet temperature	°F
$T_{\text{ambient}}$	ambient temperature	°F
$I$	solar irradiance	Btu/(h·ft²)

Symbol	Meaning	Unit
$x$	reduced-temperature curve coordinate	m²·K/W
$T_{\text{in}}$	fluid inlet temperature	°C
$T_{\text{ambient}}$	ambient temperature	°C
$I$	solar irradiance	W/m²

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.