Comparative Study of the Straight Capillary Tube for CO2 and R22 Refrigerants

The flow characteristics of CO2 refrigerant are numerically studied for an adiabatic spirally coiled capillary tube employing choked flow conditions. The mass, momentum and energy conservation equations are used to develop a numerical model. The existing model is verified with the published results. The choked flow behavior at various geometric parameters viz. tube diameter and spiral pitch is studied. Similarly, the influence of these parameters on the mass flow rate through the tube is observed. A significant change in mass flow rate is due to a change in tube diameter, whereas a minimal variation is observed with the change in surface roughness and spiral pitch. Moreover, it is observed that the coiling effect has a significant influence on the flow behavior of the spiral capillary tube. As the pressure decreases, from unchoked to the choked pressure in the evaporator by 63.46%, the mass flow rate increases by 9.46% only. The capillary tube choking is circumvented by increasing spiral pitch, tube diameter and decreasing the length of the tube. A unique nomogram is developed that gives the best understanding of choked and unchoked flow conditions, that graphical representation is useful to design the spirally coiled capillary tube. By using that, the choked length is identified for the known mass flow rate, even more, the choked mass flow rate is known for a given tube length. Moreover, for the given tube length and evaporator temperature, a nomogram is useful to the known choked values of mass flow rate and exit values of the evaporator pressure and quality of refrigerant.

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Choked Flow Behavior of CO₂ Refrigerant Flowing Through the Spiral Capillary Tube

Jadhav

Agrawal

2020

Int. J. Air-Cond. Ref.

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A Review on Flow Characteristics of the Straight and Coiled Capillary Tubes

Jadhav¹,

Agrawal

2021

Int. J. Air-Cond. Ref.

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A detailed literature review on the flow characterization of the capillary tubes is presented in this paper. The flow behavior is reviewed for straight, helically, and spirally coiled capillary tubes at different operating and geometric conditions by considering various aspects in the tube. This paper summarizes experimental and numerical study on the adiabatic and nonadiabatic straight and coiled capillary tubes at different geometries conditions. The vital information of the range of the tube geometry and operating conditions are discussed, which can be utilized for further studies on the capillary tube. Various methodologies with generalized correlations are indicated. It has been observed that there are even more studies need to do with environmentally friendly refrigerants with various practical aspects in the capillary tube. It would be interesting to find the coiling effect on the design and simulation of the capillary tube. In addition to that more experimental and numerical studies need to explore the nonadiabatic coiled capillary tube. It would be fascinating to study the metastable condition in the capillary tube and set suitable relations to present its effect on the mass flow rate.

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Comparative Study of the Straight Capillary Tube for CO2 and R22 Refrigerants

Cited by 2 publications

References 12 publications

Choked Flow Behavior of CO₂ Refrigerant Flowing Through the Spiral Capillary Tube

Choked Flow Behavior of CO₂ Refrigerant Flowing Through the Spiral Capillary Tube

A Review on Flow Characteristics of the Straight and Coiled Capillary Tubes

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Comparative Study of the Straight Capillary Tube for CO2 and R22 Refrigerants

Cited by 2 publications

References 12 publications

Choked Flow Behavior of CO2 Refrigerant Flowing Through the Spiral Capillary Tube

Choked Flow Behavior of CO2 Refrigerant Flowing Through the Spiral Capillary Tube

A Review on Flow Characteristics of the Straight and Coiled Capillary Tubes

Contact Info

Product

Resources

About

Choked Flow Behavior of CO₂ Refrigerant Flowing Through the Spiral Capillary Tube

Choked Flow Behavior of CO₂ Refrigerant Flowing Through the Spiral Capillary Tube