Refrigerant Capillary Tube Calculator

What Is a Refrigerant Capillary Tube Calculator?

A capillary tube is a narrow copper passage that meters refrigerant flow between the high-pressure condenser side and the low-pressure evaporator. When you change the inside diameter, you must also change the tube length to keep similar flow restriction. This calculator resizes capillary tubes and estimates pressure drop from refrigerant properties.

Capillary Tube Resizer Formula

The empirical resizing relationship used in refrigeration service is:

where \(NL\) is the new length, \(OL\) is the original length, and the inside diameters are in consistent units. A smaller diameter needs a shorter tube for the same restriction, and a larger diameter needs a longer tube.

Pressure Drop and Flow Sizing

For laminar refrigerant flow through a round tube, pressure drop can be estimated with:

Here \(\mu\) is dynamic viscosity, \(\rho\) is liquid density, \(L\) is tube length, \(\dot{m}\) is mass flow rate, and \(D\) is inside diameter. Refrigerant type changes \(\mu\) and \(\rho\), which is why the tool includes common refrigerants such as R-134a, R-22, and R-410A.

Related tools: Pressure Calculator, Pipe Flow Calculator, and Circle Calculator.