# Flow and pressure drop characteristics of R22 in adiabatic capillary tubes

- Received:
- Revised:

DOI: 10.1007/BF03185674

- Cite this article as:
- Kim, S.G., Kim, M.S., Ro, S.T. et al. KSME International Journal (2001) 15: 1328. doi:10.1007/BF03185674

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## Abstract

The objective of this study is to present flow and pressure drop characteristics of R22 in adiabatic capillary tubes of inner diameters of 1.2 to 2.0 mm, and tube lengths of 500 to 2000 mm. Distributions of temperature and pressure along capillary tubes and the refrigerant flow rates through the tubes were measured for several condensing temperatures and various degrees of subcooling at the capillary tube inlet. Condensing temperatures of R22 were selected as 40, 45, and 50°C at the capillary tube inlet, and the degree of subcooling was adjusted to 1 to 18°C. Experimental results including mass flow rates and pressure drops of R22 in capillary tubes were provided. A new correlation based on Buckingham π theorem to predict the mass flow rate through the capillary tube was presented considering major parameters which affect the flow and pressure drop characteristics.

### Key Words

Alternative RefrigerantCapillary TubeMass Flow RatePressure DropR22### Nomenclature

*A*Constant defined in Eq. (3)

*a*Exponent defined in Eq. (3)

*b*Exponent defined in Eq. (3)

*c*Exponent defined in Eq. (3)

*C*_{P}Specific heat at inlet of capillary tube, J/(kg·K)

*d*Inner diameter of capillary tube, mm

*f*Friction factor

*G*Mass flux, kg/(m

^{2}·s)*L*Iength of capillary tube, mm

*m*Mass flow rate, kg/s

*P*Pressure, kPa

*P*_{sat}Saturation pressure corresponding to the measured refrigerant temperature, kPa

*P*_{meas}Measured pressure of refrigerant, kPa

*P*_{s}Saturated state pressure, kPa

*P*_{v}Measured pressure of refrigerant at the onset point of vaporization, kPa

*P*_{in}Inlet pressure of capillary tube, kPa

*T*_{sub}Degree of subcooling, °C

*v*Specific volume at the inlet of capillary tube, m

^{3}/kg- \(\bar v\)
Average of specific volume, m

^{3}/kg*x*Quality

*z*Length of capillary tube, mm

### Greek Symbols

- α
Void fraction

- μ
Viscosity at the inlet of capillary tube, kg/(m·s)

- ϱ
Density, kg/m

^{3}

### Subscripts

*a*Acceleration

*f*Saturated liquid phase

*g*Saturated vapor phase