Numerical and experimental investigation of two phase flow of refrigerants in capillary tubes

Dissertant

Ubayd, Zayn al-Abidin Husayn

Thesis advisor

Muhammad, Wahid S.
Antwan, Nizar Faraj

University

University of Technology

Faculty

-

Department

Department of Electromechanical Engineering

University Country

Iraq

Degree

Master

Degree Date

2009

English Abstract

A numerical and experimental study was performed to predict the flow and thermal performance of a capillary tube thai used in air conditioning and refrigeration systems, The governing equations of such flow include continuity, momentum and energy, in addition to (k-e) model equations for turbulence in two dimensional.

In the numerical study, the (CFD) technique was employed to model those equations using the finite volume method for a two-phase, two dimensionsI flow in the pipo.

This mode! gives a fled distribution for velocity, temperature, pressure, density, and dryness fraction .alone, the tube. In the experimental part, an experimental rig was constructed using a split unite to measure the temperature and pressure along the capillary tube (1.02 m) and (I063* 10-3m) inner diameter.

These measurements mere made for (R.-22] refrigerant for different ambient temperatures It was concluded that the mass flow rate of (R-22) increases as the inlet temperature increases in capillary rube at constant pressure in evaporator for a fixed length and diameter of capillary tube, The experimental data were used to verify the numerical results.

Othei published works were also used for more- verification of the computer code results in-eluding pressure, temperature, dryness fraction, velocity, and length for several refrigerants.

The verification reveals that rhe present code can be used to predict the proper capillary tube length for each application depending on the system operating conditions. Trie computer code was then applied to predict the flow and heat transfer along several types of capillary tube i.e.

several lengths (2,5 m.

3 m.

3.5 m.

4 m).

several diameters (1.24* 10-3 m.

1.63*10-3 m.

2.16* 10-3m, 3,05* 10-3 m), several refrigerants (R-12, R-22, R-I34la.

R-407C), and for adiabatic and non- adiabatic tube. In the adiabatic capillary results, the capillary tube length of (R-407C) was found to be shorter than that required for (R-22) by (29 6 %).it was also found iliac (R-22) vaporized later than its corresponding (R.-40TC).

A similar conclusion was also found for (R-134a) shorter man (R-12) by (26.2 %). The numerical results show also that the length of capillary tube has a large effect on its performance.

When the length increases, the drop in pressure, tempt-mule-, and density increases, as well as the velocity and dryness fraction increases..

The diameter of capillary tube was found CO have a little effect on pressure, temperature, density, velocity., and dryness fraction because the applied range was small.

Main Subjects

Physics

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Language

English

Data Type

Arab Theses

Record ID

BIM-305118